esp-protocols/components/mdns/mdns.c

/*
 * SPDX-FileCopyrightText: 2015-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "freertos/semphr.h"
#include "esp_log.h"
#include "esp_event.h"
#include "mdns.h"
#include "mdns_private.h"
#include "mdns_networking.h"
#include "esp_log.h"
#include "esp_random.h"

#if CONFIG_ETH_ENABLED && CONFIG_MDNS_PREDEF_NETIF_ETH
#include "esp_eth.h"
#endif
#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP
#include "esp_wifi.h"
#endif


#ifdef MDNS_ENABLE_DEBUG
void mdns_debug_packet(const uint8_t *data, size_t len);
#endif

#ifndef ARRAY_SIZE
#define ARRAY_SIZE(array) (sizeof(array) / sizeof((array)[0]))
#endif

// Internal size of IPv6 address is defined here as size of AAAA record in mdns packet
// since the ip6_addr_t is defined in lwip and depends on using IPv6 zones
#define _MDNS_SIZEOF_IP6_ADDR (MDNS_ANSWER_AAAA_SIZE)

static const char *MDNS_DEFAULT_DOMAIN = "local";
static const char *MDNS_SUB_STR = "_sub";

mdns_server_t *_mdns_server = NULL;
static mdns_host_item_t *_mdns_host_list = NULL;
static mdns_host_item_t _mdns_self_host;

static const char *TAG = "mdns";

static volatile TaskHandle_t _mdns_service_task_handle = NULL;
static SemaphoreHandle_t _mdns_service_semaphore = NULL;

static void _mdns_search_finish_done(void);
static mdns_search_once_t *_mdns_search_find_from(mdns_search_once_t *search, mdns_name_t *name, uint16_t type, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol);
static void _mdns_search_result_add_ip(mdns_search_once_t *search, const char *hostname, esp_ip_addr_t *ip,
                                       mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, uint32_t ttl);
static void _mdns_search_result_add_srv(mdns_search_once_t *search, const char *hostname, uint16_t port,
                                        mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, uint32_t ttl);
static void _mdns_search_result_add_txt(mdns_search_once_t *search, mdns_txt_item_t *txt, uint8_t *txt_value_len,
                                        size_t txt_count, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol,
                                        uint32_t ttl);
static mdns_result_t *_mdns_search_result_add_ptr(mdns_search_once_t *search, const char *instance,
        const char *service_type, const char *proto, mdns_if_t tcpip_if,
        mdns_ip_protocol_t ip_protocol, uint32_t ttl);
static bool _mdns_append_host_list_in_services(mdns_out_answer_t **destination, mdns_srv_item_t *services[], size_t services_len, bool flush, bool bye);
static bool _mdns_append_host_list(mdns_out_answer_t **destination, bool flush, bool bye);
static void _mdns_remap_self_service_hostname(const char *old_hostname, const char *new_hostname);
static esp_err_t mdns_post_custom_action_tcpip_if(mdns_if_t mdns_if, mdns_event_actions_t event_action);

typedef enum {
    MDNS_IF_STA = 0,
    MDNS_IF_AP = 1,
    MDNS_IF_ETH = 2,
} mdns_predef_if_t;

typedef struct mdns_interfaces mdns_interfaces_t;

struct mdns_interfaces {
    const bool predefined;
    esp_netif_t *netif;
    const mdns_predef_if_t predef_if;
    mdns_if_t duplicate;
};

/*
 * @brief  Internal collection of mdns supported interfaces
 *
 */
static mdns_interfaces_t s_esp_netifs[MDNS_MAX_INTERFACES] = {
#if CONFIG_MDNS_PREDEF_NETIF_STA
    { .predefined = true, .netif = NULL, .predef_if = MDNS_IF_STA, .duplicate = MDNS_MAX_INTERFACES },
#endif
#if CONFIG_MDNS_PREDEF_NETIF_AP
    { .predefined = true, .netif = NULL, .predef_if = MDNS_IF_AP,  .duplicate = MDNS_MAX_INTERFACES },
#endif
#if CONFIG_MDNS_PREDEF_NETIF_ETH
    { .predefined = true, .netif = NULL, .predef_if = MDNS_IF_ETH, .duplicate = MDNS_MAX_INTERFACES },
#endif
};


/**
 * @brief  Convert Predefined interface to the netif id from the internal netif list
 * @param  predef_if Predefined interface enum
 * @return Ordinal number of internal list of mdns network interface.
 *         Returns MDNS_MAX_INTERFACES if the predefined interface wasn't found in the list
 */
static mdns_if_t mdns_if_from_preset_if(mdns_predef_if_t predef_if)
{
    for (int i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        if (s_esp_netifs[i].predefined && s_esp_netifs[i].predef_if == predef_if) {
            return i;
        }
    }
    return MDNS_MAX_INTERFACES;
}

/**
 * @brief  Convert Predefined interface to esp-netif handle
 * @param  predef_if Predefined interface enum
 * @return esp_netif pointer from system list of network interfaces
 */
static inline esp_netif_t *esp_netif_from_preset_if(mdns_predef_if_t predef_if)
{
    switch (predef_if) {
    case MDNS_IF_STA:
        return esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
    case MDNS_IF_AP:
        return esp_netif_get_handle_from_ifkey("WIFI_AP_DEF");
#if CONFIG_ETH_ENABLED
    case MDNS_IF_ETH:
        return esp_netif_get_handle_from_ifkey("ETH_DEF");
#endif
    default:
        return NULL;
    }
}

/**
 * @brief Gets the actual esp_netif pointer from the internal network interface list
 *
 * The supplied ordinal number could
 * - point to a predef netif -> "STA", "AP", "ETH"
 *      - if no entry in the list (NULL) -> check if the system added this netif
 * - point to a custom netif -> just return the entry in the list
 *      - users is responsible for the lifetime of this netif (to be valid between mdns-init -> deinit)
 *
 * @param tcpip_if Ordinal number of the interface
 * @return Pointer ot the esp_netif object if the interface is available, NULL otherwise
 */
esp_netif_t *_mdns_get_esp_netif(mdns_if_t tcpip_if)
{
    if (tcpip_if < MDNS_MAX_INTERFACES) {
        if (s_esp_netifs[tcpip_if].netif == NULL && s_esp_netifs[tcpip_if].predefined) {
            // If the local copy is NULL and this netif is predefined -> we can find it in the global netif list
            s_esp_netifs[tcpip_if].netif = esp_netif_from_preset_if(s_esp_netifs[tcpip_if].predef_if);
            // failing to find it means that the netif is *not* available -> return NULL
        }
        return s_esp_netifs[tcpip_if].netif;
    }
    return NULL;
}


/*
 * @brief Clean internal mdns interface's pointer
 */
static inline void _mdns_clean_netif_ptr(mdns_if_t tcpip_if)
{
    if (tcpip_if < MDNS_MAX_INTERFACES) {
        s_esp_netifs[tcpip_if].netif = NULL;
    }
}


/*
 * @brief  Convert esp-netif handle to mdns if
 */
static mdns_if_t _mdns_get_if_from_esp_netif(esp_netif_t *esp_netif)
{
    for (int i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        if (esp_netif == s_esp_netifs[i].netif) {
            return i;
        }
    }
    return MDNS_MAX_INTERFACES;
}



static inline bool _str_null_or_empty(const char *str)
{
    return (str == NULL || *str == 0);
}

/*
 * @brief  Appends/increments a number to name/instance in case of collision
 * */
static char *_mdns_mangle_name(char *in)
{
    char *p = strrchr(in, '-');
    int suffix = 0;
    if (p == NULL) {
        //No - in ``in``
        suffix = 2;
    } else {
        char *endp = NULL;
        suffix = strtol(p + 1, &endp, 10);
        if (*endp != 0) {
            //suffix is not numerical
            suffix = 2;
            p = NULL; //so we append -suffix to the entire string
        }
    }
    char *ret;
    if (p == NULL) {
        //need to add -2 to string
        ret = malloc(strlen(in) + 3);
        if (ret == NULL) {
            HOOK_MALLOC_FAILED;
            return NULL;
        }
        sprintf(ret, "%s-2", in);
    } else {
        ret = malloc(strlen(in) + 2); //one extra byte in case 9-10 or 99-100 etc
        if (ret == NULL) {
            HOOK_MALLOC_FAILED;
            return NULL;
        }
        strcpy(ret, in);
        int baseLen = p - in; //length of 'bla' in 'bla-123'
        //overwrite suffix with new suffix
        sprintf(ret + baseLen, "-%d", suffix + 1);
    }
    return ret;
}

static bool _mdns_service_match(const mdns_service_t *srv, const char *service, const char *proto,
                                const char *hostname)
{
    if (!service || !proto || !srv->hostname) {
        return false;
    }
    return !strcasecmp(srv->service, service) && !strcasecmp(srv->proto, proto) &&
           (_str_null_or_empty(hostname) || !strcasecmp(srv->hostname, hostname));
}

/**
 * @brief  finds service from given service type
 * @param  server       the server
 * @param  service      service type to match
 * @param  proto        proto to match
 * @param  hostname     hostname of the service (if non-null)
 *
 * @return the service item if found or NULL on error
 */
static mdns_srv_item_t *_mdns_get_service_item(const char *service, const char *proto, const char *hostname)
{
    mdns_srv_item_t *s = _mdns_server->services;
    while (s) {
        if (_mdns_service_match(s->service, service, proto, hostname)) {
            return s;
        }
        s = s->next;
    }
    return NULL;
}

static mdns_srv_item_t *_mdns_get_service_item_subtype(const char *subtype, const char *service, const char *proto)
{
    mdns_srv_item_t *s = _mdns_server->services;
    while (s) {
        if (_mdns_service_match(s->service, service, proto, NULL)) {
            mdns_subtype_t *subtype_item = s->service->subtype;
            while (subtype_item) {
                if (!strcasecmp(subtype_item->subtype, subtype)) {
                    return s;
                }
                subtype_item = subtype_item->next;
            }
        }
        s = s->next;
    }
    return NULL;
}

static mdns_host_item_t *mdns_get_host_item(const char *hostname)
{
    if (hostname == NULL || strcasecmp(hostname, _mdns_server->hostname) == 0) {
        return &_mdns_self_host;
    }
    mdns_host_item_t *host = _mdns_host_list;
    while (host != NULL) {
        if (strcasecmp(host->hostname, hostname) == 0) {
            return host;
        }
        host = host->next;
    }
    return NULL;
}

static bool _mdns_can_add_more_services(void)
{
    mdns_srv_item_t *s = _mdns_server->services;
    uint16_t service_num = 0;
    while (s) {
        service_num ++;
        s = s->next;
        if (service_num >= MDNS_MAX_SERVICES) {
            return false;
        }
    }

    return true;
}

esp_err_t _mdns_send_rx_action(mdns_rx_packet_t *packet)
{
    mdns_action_t *action = NULL;

    action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }

    action->type = ACTION_RX_HANDLE;
    action->data.rx_handle.packet = packet;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

static const char *_mdns_get_default_instance_name(void)
{
    if (_mdns_server && !_str_null_or_empty(_mdns_server->instance)) {
        return _mdns_server->instance;
    }

    if (_mdns_server && !_str_null_or_empty(_mdns_server->hostname)) {
        return _mdns_server->hostname;
    }

    return NULL;
}

/**
 * @brief  Get the service name of a service
 */
static const char *_mdns_get_service_instance_name(const mdns_service_t *service)
{
    if (service && !_str_null_or_empty(service->instance)) {
        return service->instance;
    }

    return _mdns_get_default_instance_name();
}

static bool _mdns_instance_name_match(const char *lhs, const char *rhs)
{
    if (lhs == NULL) {
        lhs = _mdns_get_default_instance_name();
    }
    if (rhs == NULL) {
        rhs = _mdns_get_default_instance_name();
    }
    return !strcasecmp(lhs, rhs);
}

static bool _mdns_service_match_instance(const mdns_service_t *srv, const char *instance, const char *service,
        const char *proto, const char *hostname)
{
    // service and proto must be supplied, if not this instance won't match
    if (!service || !proto) {
        return false;
    }
    // instance==NULL -> _mdns_instance_name_match() will check the default instance
    // hostname==NULL -> matches if instance, service and proto matches
    return !strcasecmp(srv->service, service) && _mdns_instance_name_match(srv->instance, instance) &&
           !strcasecmp(srv->proto, proto) && (_str_null_or_empty(hostname) || !strcasecmp(srv->hostname, hostname));
}

static mdns_srv_item_t *_mdns_get_service_item_instance(const char *instance, const char *service, const char *proto,
        const char *hostname)
{
    mdns_srv_item_t *s = _mdns_server->services;
    while (s) {
        if (instance) {
            if (_mdns_service_match_instance(s->service, instance, service, proto, hostname)) {
                return s;
            }
        } else {
            if (_mdns_service_match(s->service, service, proto, hostname)) {
                return s;
            }
        }
        s = s->next;
    }
    return NULL;
}

/**
 * @brief  reads MDNS FQDN into mdns_name_t structure
 *         FQDN is in format: [hostname.|[instance.]_service._proto.]local.
 *
 * @param  packet       MDNS packet
 * @param  start        Starting point of FQDN
 * @param  name         mdns_name_t structure to populate
 * @param  buf          temporary char buffer
 *
 * @return the address after the parsed FQDN in the packet or NULL on error
 */
static const uint8_t *_mdns_read_fqdn(const uint8_t *packet, const uint8_t *start, mdns_name_t *name, char *buf, size_t packet_len)
{
    size_t index = 0;
    const uint8_t *packet_end = packet + packet_len;
    while (start + index < packet_end && start[index]) {
        if (name->parts == 4) {
            name->invalid = true;
        }
        uint8_t len = start[index++];
        if (len < 0xC0) {
            if (len > 63) {
                //length can not be more than 63
                return NULL;
            }
            uint8_t i;
            for (i = 0; i < len; i++) {
                if (start + index >= packet_end) {
                    return NULL;
                }
                buf[i] = start[index++];
            }
            buf[len] = '\0';
            if (name->parts == 1 && buf[0] != '_'
                    && (strcasecmp(buf, MDNS_DEFAULT_DOMAIN) != 0)
                    && (strcasecmp(buf, "arpa") != 0)
#ifndef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
                    && (strcasecmp(buf, "ip6") != 0)
                    && (strcasecmp(buf, "in-addr") != 0)
#endif
               ) {
                strlcat(name->host, ".", sizeof(name->host));
                strlcat(name->host, buf, sizeof(name->host));
            } else if (strcasecmp(buf, MDNS_SUB_STR) == 0) {
                name->sub = 1;
            } else if (!name->invalid) {
                char *mdns_name_ptrs[] = {name->host, name->service, name->proto, name->domain};
                memcpy(mdns_name_ptrs[name->parts++], buf, len + 1);
            }
        } else {
            size_t address = (((uint16_t)len & 0x3F) << 8) | start[index++];
            if ((packet + address) >= start) {
                //reference address can not be after where we are
                return NULL;
            }
            if (_mdns_read_fqdn(packet, packet + address, name, buf, packet_len)) {
                return start + index;
            }
            return NULL;
        }
    }
    return start + index + 1;
}

/**
 * @brief  sets uint16_t value in a packet
 *
 * @param  packet       MDNS packet
 * @param  index        offset of uint16_t value
 * @param  value        the value to set
 */
static inline void _mdns_set_u16(uint8_t *packet, uint16_t index, uint16_t value)
{
    if ((index + 1) >= MDNS_MAX_PACKET_SIZE) {
        return;
    }
    packet[index] = (value >> 8) & 0xFF;
    packet[index + 1] = value & 0xFF;
}

/**
 * @brief  appends byte in a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  value        the value to set
 *
 * @return length of added data: 0 on error or 1 on success
 */
static inline uint8_t _mdns_append_u8(uint8_t *packet, uint16_t *index, uint8_t value)
{
    if (*index >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    packet[*index] = value;
    *index += 1;
    return 1;
}

/**
 * @brief  appends uint16_t in a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  value        the value to set
 *
 * @return length of added data: 0 on error or 2 on success
 */
static inline uint8_t _mdns_append_u16(uint8_t *packet, uint16_t *index, uint16_t value)
{
    if ((*index + 1) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, (value >> 8) & 0xFF);
    _mdns_append_u8(packet, index, value & 0xFF);
    return 2;
}

/**
 * @brief  appends uint32_t in a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  value        the value to set
 *
 * @return length of added data: 0 on error or 4 on success
 */
static inline uint8_t _mdns_append_u32(uint8_t *packet, uint16_t *index, uint32_t value)
{
    if ((*index + 3) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, (value >> 24) & 0xFF);
    _mdns_append_u8(packet, index, (value >> 16) & 0xFF);
    _mdns_append_u8(packet, index, (value >> 8) & 0xFF);
    _mdns_append_u8(packet, index, value & 0xFF);
    return 4;
}

/**
 * @brief  appends answer type, class, ttl and data length to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  type         answer type
 * @param  ttl          answer ttl
 *
 * @return length of added data: 0 on error or 10 on success
 */
static inline uint8_t _mdns_append_type(uint8_t *packet, uint16_t *index, uint8_t type, bool flush, uint32_t ttl)
{
    if ((*index + 10) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    uint16_t mdns_class = MDNS_CLASS_IN;
    if (flush) {
        mdns_class = MDNS_CLASS_IN_FLUSH_CACHE;
    }
    if (type == MDNS_ANSWER_PTR) {
        _mdns_append_u16(packet, index, MDNS_TYPE_PTR);
        _mdns_append_u16(packet, index, mdns_class);
    } else if (type == MDNS_ANSWER_TXT) {
        _mdns_append_u16(packet, index, MDNS_TYPE_TXT);
        _mdns_append_u16(packet, index, mdns_class);
    } else if (type == MDNS_ANSWER_SRV) {
        _mdns_append_u16(packet, index, MDNS_TYPE_SRV);
        _mdns_append_u16(packet, index, mdns_class);
    } else if (type == MDNS_ANSWER_A) {
        _mdns_append_u16(packet, index, MDNS_TYPE_A);
        _mdns_append_u16(packet, index, mdns_class);
    } else if (type == MDNS_ANSWER_AAAA) {
        _mdns_append_u16(packet, index, MDNS_TYPE_AAAA);
        _mdns_append_u16(packet, index, mdns_class);
    } else {
        return 0;
    }
    _mdns_append_u32(packet, index, ttl);
    _mdns_append_u16(packet, index, 0);
    return 10;
}

static inline uint8_t _mdns_append_string_with_len(uint8_t *packet, uint16_t *index, const char *string, uint8_t len)
{
    if ((*index + len + 1) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, len);
    memcpy(packet + *index, string, len);
    *index += len;
    return len + 1;
}

/**
 * @brief  appends single string to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  string       the string to append
 *
 * @return length of added data: 0 on error or length of the string + 1 on success
 */
static inline uint8_t _mdns_append_string(uint8_t *packet, uint16_t *index, const char *string)
{
    uint8_t len = strlen(string);
    if ((*index + len + 1) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, len);
    memcpy(packet + *index, string, len);
    *index += len;
    return len + 1;
}

/**
 * @brief  appends one TXT record ("key=value" or "key")
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  txt          one txt record
 *
 * @return length of added data: length of the added txt value + 1 on success
 *         0  if data won't fit the packet
 *         -1 if invalid TXT entry
 */
static inline int append_one_txt_record_entry(uint8_t *packet, uint16_t *index, mdns_txt_linked_item_t *txt)
{
    if (txt == NULL || txt->key == NULL) {
        return -1;
    }
    size_t key_len = strlen(txt->key);
    size_t len = key_len + txt->value_len + (txt->value ? 1 : 0);
    if ((*index + len + 1) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, len);
    memcpy(packet + *index, txt->key, key_len);
    if (txt->value) {
        packet[*index + key_len] = '=';
        memcpy(packet + *index + key_len + 1, txt->value, txt->value_len);
    }
    *index += len;
    return len + 1;
}

#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
static inline int append_single_str(uint8_t *packet, uint16_t *index, const char *str, int len)
{
    if ((*index + len + 1) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    if (!_mdns_append_u8(packet, index, len)) {
        return 0;
    }
    memcpy(packet + *index, str, len);
    *index += len;
    return *index;
}

/**
 * @brief  appends FQDN to a packet from hostname separated by dots. This API works the same way as
 * _mdns_append_fqdn(), but refrains from DNS compression (as it's mainly used for IP addresses (many short items),
 * where we gain very little (or compression even gets counter-productive mainly for IPv6 addresses)
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  name         name representing FQDN in '.' separated parts
 * @param  last         true if appending the last part (domain, typically "arpa")
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t append_fqdn_dots(uint8_t *packet, uint16_t *index, const char *name, bool last)
{
    int len = strlen(name);
    char *host = (char *)name;
    char *end = host;
    char *start = host;
    do  {
        end = memchr(start, '.', host + len - start);
        end = end ? end : host + len;
        int part_len = end - start;
        if (!append_single_str(packet, index, start, part_len)) {
            return 0;
        }
        start = ++end;
    } while (end < name + len);

    if (!append_single_str(packet, index, "arpa", sizeof("arpa") - 1)) {
        return 0;
    }

    //empty string so terminate
    if (!_mdns_append_u8(packet, index, 0)) {
        return 0;
    }
    return *index;
}
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */

/**
 * @brief  appends FQDN to a packet, incrementing the index and
 *         compressing the output if previous occurrence of the string (or part of it) has been found
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  strings      string array containing the parts of the FQDN
 * @param  count        number of strings in the array
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_fqdn(uint8_t *packet, uint16_t *index, const char *strings[], uint8_t count, size_t packet_len)
{
    if (!count) {
        //empty string so terminate
        return _mdns_append_u8(packet, index, 0);
    }
    mdns_name_t name;
    static char buf[MDNS_NAME_BUF_LEN];
    uint8_t len = strlen(strings[0]);
    //try to find first the string length in the packet (if it exists)
    uint8_t *len_location = (uint8_t *)memchr(packet, (char)len, *index);
    while (len_location) {
        //check if the string after len_location is the string that we are looking for
        if (memcmp(len_location + 1, strings[0], len)) { //not continuing with our string
search_next:
            //try and find the length byte further in the packet
            len_location = (uint8_t *)memchr(len_location + 1, (char)len, *index - (len_location + 1 - packet));
            continue;
        }
        //seems that we might have found the string that we are looking for
        //read the destination into name and compare
        name.parts = 0;
        name.sub = 0;
        name.invalid = false;
        name.host[0] = 0;
        name.service[0] = 0;
        name.proto[0] = 0;
        name.domain[0] = 0;
        const uint8_t *content = _mdns_read_fqdn(packet, len_location, &name, buf, packet_len);
        if (!content) {
            //not a readable fqdn?
            goto search_next; // could be our unfinished fqdn, continue searching
        }
        if (name.parts == count) {
            uint8_t i;
            for (i = 0; i < count; i++) {
                if (strcasecmp(strings[i], (const char *)&name + (i * (MDNS_NAME_BUF_LEN)))) {
                    //not our string! let's search more
                    goto search_next;
                }
            }
            //we actually have found the string
            break;
        } else {
            goto search_next;
        }
    }
    //string is not yet in the packet, so let's add it
    if (!len_location) {
        uint8_t written = _mdns_append_string(packet, index, strings[0]);
        if (!written) {
            return 0;
        }
        //run the same for the other strings in the name
        return written + _mdns_append_fqdn(packet, index, &strings[1], count - 1, packet_len);
    }

    //we have found the string so let's insert a pointer to it instead
    uint16_t offset = len_location - packet;
    offset |= MDNS_NAME_REF;
    return _mdns_append_u16(packet, index, offset);
}

/**
 * @brief  appends PTR record for service to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  server       the server that is hosting the service
 * @param  service      the service to add record for
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_ptr_record(uint8_t *packet, uint16_t *index, const char *instance, const char *service, const char *proto, bool flush, bool bye)
{
    const char *str[4];
    uint16_t record_length = 0;
    uint8_t part_length;

    if (service == NULL) {
        return 0;
    }

    str[0] = instance;
    str[1] = service;
    str[2] = proto;
    str[3] = MDNS_DEFAULT_DOMAIN;

    part_length = _mdns_append_fqdn(packet, index, str + 1, 3, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_PTR, false, bye ? 0 : MDNS_ANSWER_PTR_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;
    part_length = _mdns_append_fqdn(packet, index, str, 4, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    _mdns_set_u16(packet, data_len_location, part_length);
    record_length += part_length;
    return record_length;
}

/**
 * @brief  appends PTR record for a subtype to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  instance     the service instance name
 * @param  subtype      the service subtype
 * @param  proto        the service protocol
 * @param  flush        whether to set the flush flag
 * @param  bye          whether to set the bye flag
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_subtype_ptr_record(uint8_t *packet, uint16_t *index, const char *instance,
        const char *subtype, const char *service, const char *proto, bool flush,
        bool bye)
{
    const char *subtype_str[5] = {subtype, MDNS_SUB_STR, service, proto, MDNS_DEFAULT_DOMAIN};
    const char *instance_str[4] = {instance, service, proto, MDNS_DEFAULT_DOMAIN};
    uint16_t record_length = 0;
    uint8_t part_length;

    if (service == NULL) {
        return 0;
    }

    part_length = _mdns_append_fqdn(packet, index, subtype_str, ARRAY_SIZE(subtype_str), MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_PTR, false, bye ? 0 : MDNS_ANSWER_PTR_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;
    part_length = _mdns_append_fqdn(packet, index, instance_str, ARRAY_SIZE(instance_str), MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    _mdns_set_u16(packet, data_len_location, part_length);
    record_length += part_length;
    return record_length;
}

/**
 * @brief  appends DNS-SD PTR record for service to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  server       the server that is hosting the service
 * @param  service      the service to add record for
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_sdptr_record(uint8_t *packet, uint16_t *index, mdns_service_t *service, bool flush, bool bye)
{
    const char *str[3];
    const char *sd_str[4];
    uint16_t record_length = 0;
    uint8_t part_length;

    if (service == NULL) {
        return 0;
    }

    sd_str[0] = (char *)"_services";
    sd_str[1] = (char *)"_dns-sd";
    sd_str[2] = (char *)"_udp";
    sd_str[3] = MDNS_DEFAULT_DOMAIN;

    str[0] = service->service;
    str[1] = service->proto;
    str[2] = MDNS_DEFAULT_DOMAIN;

    part_length = _mdns_append_fqdn(packet, index, sd_str, 4, MDNS_MAX_PACKET_SIZE);

    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_PTR, flush, MDNS_ANSWER_PTR_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;
    part_length = _mdns_append_fqdn(packet, index, str, 3, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    _mdns_set_u16(packet, data_len_location, part_length);
    record_length += part_length;
    return record_length;
}

/**
 * @brief  appends TXT record for service to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  server       the server that is hosting the service
 * @param  service      the service to add record for
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_txt_record(uint8_t *packet, uint16_t *index, mdns_service_t *service, bool flush, bool bye)
{
    const char *str[4];
    uint16_t record_length = 0;
    uint8_t part_length;

    if (service == NULL) {
        return 0;
    }

    str[0] = _mdns_get_service_instance_name(service);
    str[1] = service->service;
    str[2] = service->proto;
    str[3] = MDNS_DEFAULT_DOMAIN;

    if (!str[0]) {
        return 0;
    }

    part_length = _mdns_append_fqdn(packet, index, str, 4, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_TXT, flush, bye ? 0 : MDNS_ANSWER_TXT_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;
    uint16_t data_len = 0;

    mdns_txt_linked_item_t *txt = service->txt;
    while (txt) {
        int l = append_one_txt_record_entry(packet, index, txt);
        if (l > 0) {
            data_len += l;
        } else if (l == 0) { // TXT entry won't fit into the mdns packet
            return 0;
        }
        txt = txt->next;
    }
    if (!data_len) {
        data_len = 1;
        packet[*index] = 0;
        *index = *index + 1;
    }
    _mdns_set_u16(packet, data_len_location, data_len);
    record_length += data_len;
    return record_length;
}

/**
 * @brief  appends SRV record for service to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  server       the server that is hosting the service
 * @param  service      the service to add record for
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_srv_record(uint8_t *packet, uint16_t *index, mdns_service_t *service, bool flush, bool bye)
{
    const char *str[4];
    uint16_t record_length = 0;
    uint8_t part_length;

    if (service == NULL) {
        return 0;
    }

    str[0] = _mdns_get_service_instance_name(service);
    str[1] = service->service;
    str[2] = service->proto;
    str[3] = MDNS_DEFAULT_DOMAIN;

    if (!str[0]) {
        return 0;
    }

    part_length = _mdns_append_fqdn(packet, index, str, 4, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_SRV, flush, bye ? 0 : MDNS_ANSWER_SRV_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;

    part_length = 0;
    part_length += _mdns_append_u16(packet, index, service->priority);
    part_length += _mdns_append_u16(packet, index, service->weight);
    part_length += _mdns_append_u16(packet, index, service->port);
    if (part_length != 6) {
        return 0;
    }

    if (service->hostname) {
        str[0] = service->hostname;
    } else {
        str[0] = _mdns_server->hostname;
    }
    str[1] = MDNS_DEFAULT_DOMAIN;

    if (_str_null_or_empty(str[0])) {
        return 0;
    }

    part_length = _mdns_append_fqdn(packet, index, str, 2, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    _mdns_set_u16(packet, data_len_location, part_length + 6);

    record_length += part_length + 6;
    return record_length;
}

/**
 * @brief  appends A record to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  hostname     the hostname address to add
 * @param  ip           the IP address to add
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_a_record(uint8_t *packet, uint16_t *index, const char *hostname, uint32_t ip, bool flush, bool bye)
{
    const char *str[2];
    uint16_t record_length = 0;
    uint8_t part_length;

    str[0] = hostname;
    str[1] = MDNS_DEFAULT_DOMAIN;

    if (_str_null_or_empty(str[0])) {
        return 0;
    }

    part_length = _mdns_append_fqdn(packet, index, str, 2, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_A, flush, bye ? 0 : MDNS_ANSWER_A_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;

    if ((*index + 3) >= MDNS_MAX_PACKET_SIZE) {
        return 0;
    }
    _mdns_append_u8(packet, index, ip & 0xFF);
    _mdns_append_u8(packet, index, (ip >> 8) & 0xFF);
    _mdns_append_u8(packet, index, (ip >> 16) & 0xFF);
    _mdns_append_u8(packet, index, (ip >> 24) & 0xFF);
    _mdns_set_u16(packet, data_len_location, 4);

    record_length += 4;
    return record_length;
}

#if CONFIG_LWIP_IPV6
/**
 * @brief  appends AAAA record to a packet, incrementing the index
 *
 * @param  packet       MDNS packet
 * @param  index        offset in the packet
 * @param  hostname     the hostname address to add
 * @param  ipv6         the IPv6 address to add
 *
 * @return length of added data: 0 on error or length on success
 */
static uint16_t _mdns_append_aaaa_record(uint8_t *packet, uint16_t *index, const char *hostname, uint8_t *ipv6, bool flush, bool bye)
{
    const char *str[2];
    uint16_t record_length = 0;
    uint8_t part_length;

    str[0] = hostname;
    str[1] = MDNS_DEFAULT_DOMAIN;

    if (_str_null_or_empty(str[0])) {
        return 0;
    }


    part_length = _mdns_append_fqdn(packet, index, str, 2, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    part_length = _mdns_append_type(packet, index, MDNS_ANSWER_AAAA, flush, bye ? 0 : MDNS_ANSWER_AAAA_TTL);
    if (!part_length) {
        return 0;
    }
    record_length += part_length;

    uint16_t data_len_location = *index - 2;

    if ((*index + MDNS_ANSWER_AAAA_SIZE) > MDNS_MAX_PACKET_SIZE) {
        return 0;
    }

    part_length = MDNS_ANSWER_AAAA_SIZE;
    memcpy(packet + *index, ipv6, part_length);
    *index += part_length;
    _mdns_set_u16(packet, data_len_location, part_length);
    record_length += part_length;
    return record_length;
}
#endif

/**
 * @brief  Append question to packet
 */
static uint16_t _mdns_append_question(uint8_t *packet, uint16_t *index, mdns_out_question_t *q)
{
    uint8_t part_length;
#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
    if (q->host && (strstr(q->host, "in-addr") || strstr(q->host, "ip6"))) {
        part_length = append_fqdn_dots(packet, index, q->host, false);
        if (!part_length) {
            return 0;
        }
    } else
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
    {
        const char *str[4];
        uint8_t str_index = 0;
        if (q->host) {
            str[str_index++] = q->host;
        }
        if (q->service) {
            str[str_index++] = q->service;
        }
        if (q->proto) {
            str[str_index++] = q->proto;
        }
        if (q->domain) {
            str[str_index++] = q->domain;
        }
        part_length = _mdns_append_fqdn(packet, index, str, str_index, MDNS_MAX_PACKET_SIZE);
        if (!part_length) {
            return 0;
        }
    }

    part_length += _mdns_append_u16(packet, index, q->type);
    part_length += _mdns_append_u16(packet, index, q->unicast ? 0x8001 : 0x0001);
    return part_length;
}

/**
 * @brief  Helper to get either ETH or STA if the other is provided
 *          Used when two interfaces are on the same subnet
 */
static mdns_if_t _mdns_get_other_if (mdns_if_t tcpip_if)
{
    if (tcpip_if < MDNS_MAX_INTERFACES) {
        return s_esp_netifs[tcpip_if].duplicate;
    }
    return MDNS_MAX_INTERFACES;
}

/**
 * @brief  Check if interface is duplicate (two interfaces on the same subnet)
 */
static bool _mdns_if_is_dup(mdns_if_t tcpip_if)
{
    mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
    if (other_if == MDNS_MAX_INTERFACES) {
        return false;
    }
    if (_mdns_server->interfaces[tcpip_if].pcbs[MDNS_IP_PROTOCOL_V4].state == PCB_DUP
            || _mdns_server->interfaces[tcpip_if].pcbs[MDNS_IP_PROTOCOL_V6].state == PCB_DUP
            || _mdns_server->interfaces[other_if].pcbs[MDNS_IP_PROTOCOL_V4].state == PCB_DUP
            || _mdns_server->interfaces[other_if].pcbs[MDNS_IP_PROTOCOL_V6].state == PCB_DUP
       ) {
        return true;
    }
    return false;
}

#if CONFIG_LWIP_IPV6
/**
 * @brief  Check if IPv6 address is NULL
 */
static bool _ipv6_address_is_zero(esp_ip6_addr_t ip6)
{
    uint8_t i;
    uint8_t *data = (uint8_t *)ip6.addr;
    for (i = 0; i < _MDNS_SIZEOF_IP6_ADDR; i++) {
        if (data[i]) {
            return false;
        }
    }
    return true;
}
#endif

static uint8_t _mdns_append_host_answer(uint8_t *packet, uint16_t *index, mdns_host_item_t *host,
                                        uint8_t address_type, bool flush, bool bye)
{
    mdns_ip_addr_t *addr = host->address_list;
    uint8_t num_records = 0;

    while (addr != NULL) {
        if (addr->addr.type == address_type) {
            if (address_type == ESP_IPADDR_TYPE_V4 &&
                    _mdns_append_a_record(packet, index, host->hostname, addr->addr.u_addr.ip4.addr, flush, bye) <= 0) {
                break;
            }
#if CONFIG_LWIP_IPV6
            if (address_type == ESP_IPADDR_TYPE_V6 &&
                    _mdns_append_aaaa_record(packet, index, host->hostname, (uint8_t *)addr->addr.u_addr.ip6.addr, flush,
                                             bye) <= 0) {
                break;
            }
#endif // CONFIG_LWIP_IPV6
            num_records++;
        }
        addr = addr->next;
    }
    return num_records;
}

#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
/**
 * @brief Appends reverse lookup PTR record
 */
static uint8_t _mdns_append_reverse_ptr_record(uint8_t *packet, uint16_t *index, const char *name)
{
    if (strstr(name, "in-addr") == NULL && strstr(name, "ip6") == NULL) {
        return 0;
    }

    if (!append_fqdn_dots(packet, index, name, false)) {
        return 0;
    }

    if (!_mdns_append_type(packet, index, MDNS_ANSWER_PTR, false, 10 /* TTL set to 10s*/ )) {
        return 0;
    }

    uint16_t data_len_location = *index - 2; /* store the position of size (2=16bis) of this record */
    const char *str[2] = { _mdns_self_host.hostname, MDNS_DEFAULT_DOMAIN };

    int part_length = _mdns_append_fqdn(packet, index, str, 2, MDNS_MAX_PACKET_SIZE);
    if (!part_length) {
        return 0;
    }

    _mdns_set_u16(packet, data_len_location, part_length);
    return 1; /* appending only 1 record */
}
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */

/**
 * @brief  Append PTR answers to packet
 *
 *  @return number of answers added to the packet
 */
static uint8_t _mdns_append_service_ptr_answers(uint8_t *packet, uint16_t *index, mdns_service_t *service, bool flush,
        bool bye)
{
    uint8_t appended_answers = 0;

    if (_mdns_append_ptr_record(packet, index, _mdns_get_service_instance_name(service), service->service,
                                service->proto, flush, bye) <= 0) {
        return appended_answers;
    }
    appended_answers++;

    mdns_subtype_t *subtype = service->subtype;
    while (subtype) {
        appended_answers +=
            (_mdns_append_subtype_ptr_record(packet, index, _mdns_get_service_instance_name(service), subtype->subtype,
                                             service->service, service->proto, flush, bye) > 0);
        subtype = subtype->next;
    }

    return appended_answers;
}


/**
 * @brief  Append answer to packet
 *
 *  @return number of answers added to the packet
 */
static uint8_t _mdns_append_answer(uint8_t *packet, uint16_t *index, mdns_out_answer_t *answer, mdns_if_t tcpip_if)
{
    if (answer->type == MDNS_TYPE_PTR) {
        if (answer->service) {
            return _mdns_append_service_ptr_answers(packet, index, answer->service, answer->flush, answer->bye);
#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
        } else if (answer->host && answer->host->hostname &&
                   (strstr(answer->host->hostname, "in-addr") || strstr(answer->host->hostname, "ip6"))) {
            return _mdns_append_reverse_ptr_record(packet, index, answer->host->hostname) > 0;
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
        } else {
            return _mdns_append_ptr_record(packet, index,
                                           answer->custom_instance, answer->custom_service, answer->custom_proto,
                                           answer->flush, answer->bye) > 0;
        }
    } else if (answer->type == MDNS_TYPE_SRV) {
        return _mdns_append_srv_record(packet, index, answer->service, answer->flush, answer->bye) > 0;
    } else if (answer->type == MDNS_TYPE_TXT) {
        return _mdns_append_txt_record(packet, index, answer->service, answer->flush, answer->bye) > 0;
    } else if (answer->type == MDNS_TYPE_SDPTR) {
        return _mdns_append_sdptr_record(packet, index, answer->service, answer->flush, answer->bye) > 0;
    } else if (answer->type == MDNS_TYPE_A) {
        if (answer->host == &_mdns_self_host) {
            esp_netif_ip_info_t if_ip_info;
            if (!mdns_is_netif_ready(tcpip_if, MDNS_IP_PROTOCOL_V4) && _mdns_server->interfaces[tcpip_if].pcbs[MDNS_IP_PROTOCOL_V4].state != PCB_DUP) {
                return 0;
            }
            if (esp_netif_get_ip_info(_mdns_get_esp_netif(tcpip_if), &if_ip_info)) {
                return 0;
            }
            if (_mdns_append_a_record(packet, index, _mdns_server->hostname, if_ip_info.ip.addr, answer->flush, answer->bye) <= 0) {
                return 0;
            }
            if (!_mdns_if_is_dup(tcpip_if)) {
                return 1;
            }
            mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
            if (esp_netif_get_ip_info(_mdns_get_esp_netif(other_if), &if_ip_info)) {
                return 1;
            }
            if (_mdns_append_a_record(packet, index, _mdns_server->hostname, if_ip_info.ip.addr, answer->flush, answer->bye) > 0) {
                return 2;
            }
            return 1;
        } else if (answer->host != NULL) {
            return _mdns_append_host_answer(packet, index, answer->host, ESP_IPADDR_TYPE_V4, answer->flush, answer->bye);
        }
    }
#if CONFIG_LWIP_IPV6
    else if (answer->type == MDNS_TYPE_AAAA) {
        if (answer->host == &_mdns_self_host) {
            struct esp_ip6_addr if_ip6s[NETIF_IPV6_MAX_NUMS];
            uint8_t count = 0;
            if (!mdns_is_netif_ready(tcpip_if, MDNS_IP_PROTOCOL_V6) && _mdns_server->interfaces[tcpip_if].pcbs[MDNS_IP_PROTOCOL_V6].state != PCB_DUP) {
                return 0;
            }
            count = esp_netif_get_all_ip6(_mdns_get_esp_netif(tcpip_if), if_ip6s);
            assert(count <= NETIF_IPV6_MAX_NUMS);
            for (int i = 0; i < count; i++) {
                if (_ipv6_address_is_zero(if_ip6s[i])) {
                    return 0;
                }
                if (_mdns_append_aaaa_record(packet, index, _mdns_server->hostname, (uint8_t *)if_ip6s[i].addr,
                                             answer->flush, answer->bye) <= 0) {
                    return 0;
                }
            }
            if (!_mdns_if_is_dup(tcpip_if)) {
                return count;
            }

            mdns_if_t other_if = _mdns_get_other_if(tcpip_if);
            struct esp_ip6_addr other_ip6;
            if (esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(other_if), &other_ip6)) {
                return count;
            }
            if (_mdns_append_aaaa_record(packet, index, _mdns_server->hostname, (uint8_t *)other_ip6.addr,
                                         answer->flush, answer->bye) > 0) {
                return 1 + count;
            }
            return count;
        } else if (answer->host != NULL) {
            return _mdns_append_host_answer(packet, index, answer->host, ESP_IPADDR_TYPE_V6, answer->flush,
                                            answer->bye);
        }
    }
#endif
    return 0;
}

/**
 * @brief  sends a packet
 *
 * @param  p       the packet
 */
static void _mdns_dispatch_tx_packet(mdns_tx_packet_t *p)
{
    static uint8_t packet[MDNS_MAX_PACKET_SIZE];
    uint16_t index = MDNS_HEAD_LEN;
    memset(packet, 0, MDNS_HEAD_LEN);
    mdns_out_question_t *q;
    mdns_out_answer_t *a;
    uint8_t count;

    _mdns_set_u16(packet, MDNS_HEAD_FLAGS_OFFSET, p->flags);
    _mdns_set_u16(packet, MDNS_HEAD_ID_OFFSET, p->id);

    count = 0;
    q = p->questions;
    while (q) {
        if (_mdns_append_question(packet, &index, q)) {
            count++;
        }
        q = q->next;
    }
    _mdns_set_u16(packet, MDNS_HEAD_QUESTIONS_OFFSET, count);

    count = 0;
    a = p->answers;
    while (a) {
        count += _mdns_append_answer(packet, &index, a, p->tcpip_if);
        a = a->next;
    }
    _mdns_set_u16(packet, MDNS_HEAD_ANSWERS_OFFSET, count);

    count = 0;
    a = p->servers;
    while (a) {
        count += _mdns_append_answer(packet, &index, a, p->tcpip_if);
        a = a->next;
    }
    _mdns_set_u16(packet, MDNS_HEAD_SERVERS_OFFSET, count);

    count = 0;
    a = p->additional;
    while (a) {
        count += _mdns_append_answer(packet, &index, a, p->tcpip_if);
        a = a->next;
    }
    _mdns_set_u16(packet, MDNS_HEAD_ADDITIONAL_OFFSET, count);

#ifdef MDNS_ENABLE_DEBUG
    _mdns_dbg_printf("\nTX[%u][%u]: ", p->tcpip_if, p->ip_protocol);
    if (p->dst.type == ESP_IPADDR_TYPE_V4) {
        _mdns_dbg_printf("To: " IPSTR ":%u, ", IP2STR(&p->dst.u_addr.ip4), p->port);
    } else {
        _mdns_dbg_printf("To: " IPV6STR ":%u, ", IPV62STR(p->dst.u_addr.ip6), p->port);
    }
    mdns_debug_packet(packet, index);
#endif

    _mdns_udp_pcb_write(p->tcpip_if, p->ip_protocol, &p->dst, p->port, packet, index);
}

/**
 * @brief  frees a packet
 *
 * @param  packet       the packet
 */
static void _mdns_free_tx_packet(mdns_tx_packet_t *packet)
{
    if (!packet) {
        return;
    }
    mdns_out_question_t *q = packet->questions;
    while (q) {
        mdns_out_question_t *next = q->next;
        if (q->own_dynamic_memory) {
            free((char *)q->host);
            free((char *)q->service);
            free((char *)q->proto);
            free((char *)q->domain);
        }
        free(q);
        q = next;
    }
    queueFree(mdns_out_answer_t, packet->answers);
    queueFree(mdns_out_answer_t, packet->servers);
    queueFree(mdns_out_answer_t, packet->additional);
    free(packet);
}

/**
 * @brief  schedules a packet to be sent after given milliseconds
 *
 * @param  packet       the packet
 * @param  ms_after     number of milliseconds after which the packet should be dispatched
 */
static void _mdns_schedule_tx_packet(mdns_tx_packet_t *packet, uint32_t ms_after)
{
    if (!packet) {
        return;
    }
    packet->send_at = (xTaskGetTickCount() * portTICK_PERIOD_MS) + ms_after;
    packet->next = NULL;
    if (!_mdns_server->tx_queue_head || _mdns_server->tx_queue_head->send_at > packet->send_at) {
        packet->next = _mdns_server->tx_queue_head;
        _mdns_server->tx_queue_head = packet;
        return;
    }
    mdns_tx_packet_t *q = _mdns_server->tx_queue_head;
    while (q->next && q->next->send_at <= packet->send_at) {
        q = q->next;
    }
    packet->next = q->next;
    q->next = packet;
}

/**
 * @brief  free all packets scheduled for sending
 */
static void _mdns_clear_tx_queue_head(void)
{
    mdns_tx_packet_t *q;
    while (_mdns_server->tx_queue_head) {
        q = _mdns_server->tx_queue_head;
        _mdns_server->tx_queue_head = _mdns_server->tx_queue_head->next;
        _mdns_free_tx_packet(q);
    }
}

/**
 * @brief  clear packets scheduled for sending on a specific interface
 *
 * @param  tcpip_if     the interface
 * @param  ip_protocol     pcb type V4/V6
 */
static void _mdns_clear_pcb_tx_queue_head(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_tx_packet_t *q, * p;
    while (_mdns_server->tx_queue_head && _mdns_server->tx_queue_head->tcpip_if == tcpip_if && _mdns_server->tx_queue_head->ip_protocol == ip_protocol) {
        q = _mdns_server->tx_queue_head;
        _mdns_server->tx_queue_head = _mdns_server->tx_queue_head->next;
        _mdns_free_tx_packet(q);
    }
    if (_mdns_server->tx_queue_head) {
        q = _mdns_server->tx_queue_head;
        while (q->next) {
            if (q->next->tcpip_if == tcpip_if && q->next->ip_protocol == ip_protocol) {
                p = q->next;
                q->next = p->next;
                _mdns_free_tx_packet(p);
            } else {
                q = q->next;
            }
        }
    }
}

/**
 * @brief  get the next packet scheduled for sending on a specific interface
 *
 * @param  tcpip_if     the interface
 * @param  ip_protocol     pcb type V4/V6
 */
static mdns_tx_packet_t *_mdns_get_next_pcb_packet(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_tx_packet_t *q = _mdns_server->tx_queue_head;
    while (q) {
        if (q->tcpip_if == tcpip_if && q->ip_protocol == ip_protocol) {
            return q;
        }
        q = q->next;
    }
    return NULL;
}

/**
 * @brief  Find, remove and free answer from the scheduled packets
 */
static void _mdns_remove_scheduled_answer(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, uint16_t type, mdns_srv_item_t *service)
{
    mdns_srv_item_t s = {NULL, NULL};
    if (!service) {
        service = &s;
    }
    mdns_tx_packet_t *q = _mdns_server->tx_queue_head;
    while (q) {
        if (q->tcpip_if == tcpip_if && q->ip_protocol == ip_protocol && q->distributed) {
            mdns_out_answer_t *a = q->answers;
            if (a) {
                if (a->type == type && a->service == service->service) {
                    q->answers = q->answers->next;
                    free(a);
                } else {
                    while (a->next) {
                        if (a->next->type == type && a->next->service == service->service) {
                            mdns_out_answer_t *b = a->next;
                            a->next = b->next;
                            free(b);
                            break;
                        }
                        a = a->next;
                    }
                }
            }
        }
        q = q->next;
    }
}

/**
 * @brief  Remove and free answer from answer list (destination)
 */
static void _mdns_dealloc_answer(mdns_out_answer_t **destination, uint16_t type, mdns_srv_item_t *service)
{
    mdns_out_answer_t *d = *destination;
    if (!d) {
        return;
    }
    mdns_srv_item_t s = {NULL, NULL};
    if (!service) {
        service = &s;
    }
    if (d->type == type && d->service == service->service) {
        *destination = d->next;
        free(d);
        return;
    }
    while (d->next) {
        mdns_out_answer_t *a = d->next;
        if (a->type == type && a->service == service->service) {
            d->next = a->next;
            free(a);
            return;
        }
        d = d->next;
    }
}

/**
 * @brief  Allocate new answer and add it to answer list (destination)
 */
static bool _mdns_alloc_answer(mdns_out_answer_t **destination, uint16_t type, mdns_service_t *service,
                               mdns_host_item_t *host, bool flush, bool bye)
{
    mdns_out_answer_t *d = *destination;
    while (d) {
        if (d->type == type && d->service == service && d->host == host) {
            return true;
        }
        d = d->next;
    }

    mdns_out_answer_t *a = (mdns_out_answer_t *)malloc(sizeof(mdns_out_answer_t));
    if (!a) {
        HOOK_MALLOC_FAILED;
        return false;
    }
    a->type = type;
    a->service = service;
    a->host = host;
    a->custom_service = NULL;
    a->bye = bye;
    a->flush = flush;
    a->next = NULL;
    queueToEnd(mdns_out_answer_t, *destination, a);
    return true;
}

/**
 * @brief  Allocate new packet for sending
 */
static mdns_tx_packet_t *_mdns_alloc_packet_default(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_tx_packet_t *packet = (mdns_tx_packet_t *)malloc(sizeof(mdns_tx_packet_t));
    if (!packet) {
        HOOK_MALLOC_FAILED;
        return NULL;
    }
    memset((uint8_t *)packet, 0, sizeof(mdns_tx_packet_t));
    packet->tcpip_if = tcpip_if;
    packet->ip_protocol = ip_protocol;
    packet->port = MDNS_SERVICE_PORT;
    if (ip_protocol == MDNS_IP_PROTOCOL_V4) {
        esp_ip_addr_t addr = ESP_IP4ADDR_INIT(224, 0, 0, 251);
        memcpy(&packet->dst, &addr, sizeof(esp_ip_addr_t));
    }
#if CONFIG_LWIP_IPV6
    else {
        esp_ip_addr_t addr = ESP_IP6ADDR_INIT(0x000002ff, 0, 0, 0xfb000000);
        memcpy(&packet->dst, &addr, sizeof(esp_ip_addr_t));
    }
#endif
    return packet;
}

static bool _mdns_create_answer_from_service(mdns_tx_packet_t *packet, mdns_service_t *service,
        mdns_parsed_question_t *question, bool shared, bool send_flush)
{
    mdns_host_item_t *host = mdns_get_host_item(service->hostname);
    bool is_delegated = (host != &_mdns_self_host);
    if (question->type == MDNS_TYPE_PTR || question->type == MDNS_TYPE_ANY) {
        // According to RFC6763-section12.1, for DNS-SD, SRV, TXT and all address records
        // should be included in additional records.
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_PTR, service, NULL, false, false) ||
                !_mdns_alloc_answer(is_delegated ? &packet->additional : &packet->answers, MDNS_TYPE_SRV, service, NULL, send_flush, false) ||
                !_mdns_alloc_answer(is_delegated ? &packet->additional : &packet->answers, MDNS_TYPE_TXT, service, NULL, send_flush, false) ||
                !_mdns_alloc_answer((shared || is_delegated) ? &packet->additional : &packet->answers, MDNS_TYPE_A, service, host, send_flush,
                                    false) ||
                !_mdns_alloc_answer((shared || is_delegated) ? &packet->additional : &packet->answers, MDNS_TYPE_AAAA, service, host,
                                    send_flush, false)) {
            return false;
        }
    } else if (question->type == MDNS_TYPE_SRV) {
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SRV, service, NULL, send_flush, false) ||
                !_mdns_alloc_answer(&packet->additional, MDNS_TYPE_A, service, host, send_flush, false) ||
                !_mdns_alloc_answer(&packet->additional, MDNS_TYPE_AAAA, service, host, send_flush, false)) {
            return false;
        }
    } else if (question->type == MDNS_TYPE_TXT) {
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_TXT, service, NULL, send_flush, false)) {
            return false;
        }
    } else if (question->type == MDNS_TYPE_SDPTR) {
        shared = true;
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SDPTR, service, NULL, false, false)) {
            return false;
        }
    }
    return true;
}

static bool _mdns_create_answer_from_hostname(mdns_tx_packet_t *packet, const char *hostname, bool send_flush)
{
    mdns_host_item_t *host = mdns_get_host_item(hostname);
    if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_A, NULL, host, send_flush, false) ||
            !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_AAAA, NULL, host, send_flush, false)) {
        return false;
    }
    return true;
}

static bool _mdns_service_match_ptr_question(const mdns_service_t *service, const mdns_parsed_question_t *question)
{
    if (!_mdns_service_match(service, question->service, question->proto, NULL)) {
        return false;
    }
    // The question parser stores anything before _type._proto in question->host
    // So the question->host can be subtype or instance name based on its content
    if (question->sub) {
        mdns_subtype_t *subtype = service->subtype;
        while (subtype) {
            if (!strcasecmp(subtype->subtype, question->host)) {
                return true;
            }
            subtype = subtype->next;
        }
        return false;
    }
    if (question->host) {
        if (strcasecmp(_mdns_get_service_instance_name(service), question->host) != 0) {
            return false;
        }
    }
    return true;
}

/**
 * @brief  Create answer packet to questions from parsed packet
 */
static void _mdns_create_answer_from_parsed_packet(mdns_parsed_packet_t *parsed_packet)
{
    if (!parsed_packet->questions) {
        return;
    }
    bool send_flush = parsed_packet->src_port == MDNS_SERVICE_PORT;
    bool unicast = false;
    bool shared = false;
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(parsed_packet->tcpip_if, parsed_packet->ip_protocol);
    if (!packet) {
        return;
    }
    packet->flags = MDNS_FLAGS_QR_AUTHORITATIVE;
    packet->distributed = parsed_packet->distributed;
    packet->id = parsed_packet->id;

    mdns_parsed_question_t *q = parsed_packet->questions;
    while (q) {
        shared = q->type == MDNS_TYPE_PTR || q->type == MDNS_TYPE_SDPTR || !parsed_packet->probe;
        if (q->type == MDNS_TYPE_SRV || q->type == MDNS_TYPE_TXT) {
            mdns_srv_item_t *service = _mdns_get_service_item_instance(q->host, q->service, q->proto, NULL);
            if (service == NULL || !_mdns_create_answer_from_service(packet, service->service, q, shared, send_flush)) {
                _mdns_free_tx_packet(packet);
                return;
            }
        } else if (q->service && q->proto) {
            mdns_srv_item_t *service = _mdns_server->services;
            while (service) {
                if (_mdns_service_match_ptr_question(service->service, q)) {
                    if (!_mdns_create_answer_from_service(packet, service->service, q, shared, send_flush)) {
                        _mdns_free_tx_packet(packet);
                        return;
                    }
                }
                service = service->next;
            }
        } else if (q->type == MDNS_TYPE_A || q->type == MDNS_TYPE_AAAA) {
            if (!_mdns_create_answer_from_hostname(packet, q->host, send_flush)) {
                _mdns_free_tx_packet(packet);
                return;
            }
        } else if (q->type == MDNS_TYPE_ANY) {
            if (!_mdns_append_host_list(&packet->answers, send_flush, false)) {
                _mdns_free_tx_packet(packet);
                return;
            }
#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
        } else if (q->type == MDNS_TYPE_PTR) {
            mdns_host_item_t *host = mdns_get_host_item(q->host);
            if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_PTR, NULL, host, send_flush, false)) {
                return;
            }
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
        } else if (!_mdns_alloc_answer(&packet->answers, q->type, NULL, NULL, send_flush, false)) {
            _mdns_free_tx_packet(packet);
            return;
        }

        if (parsed_packet->src_port != MDNS_SERVICE_PORT &&  // Repeat the queries only for "One-Shot mDNS queries"
                (q->type == MDNS_TYPE_ANY || q->type == MDNS_TYPE_A || q->type == MDNS_TYPE_AAAA
#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
                 || q->type == MDNS_TYPE_PTR
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
                )) {
            mdns_out_question_t *out_question = malloc(sizeof(mdns_out_question_t));
            if (out_question == NULL) {
                HOOK_MALLOC_FAILED;
                _mdns_free_tx_packet(packet);
                return;
            }
            out_question->type = q->type;
            out_question->unicast = q->unicast;
            out_question->host = q->host;
            q->host = NULL;
            out_question->service = q->service;
            q->service = NULL;
            out_question->proto = q->proto;
            q->proto = NULL;
            out_question->domain = q->domain;
            q->domain = NULL;
            out_question->next = NULL;
            out_question->own_dynamic_memory = true;
            queueToEnd(mdns_out_question_t, packet->questions, out_question);
        }
        if (q->unicast) {
            unicast = true;
        }
        q = q->next;
    }
    if (unicast || !send_flush) {
        memcpy(&packet->dst, &parsed_packet->src, sizeof(esp_ip_addr_t));
        packet->port = parsed_packet->src_port;
    }

    static uint8_t share_step = 0;
    if (shared) {
        _mdns_schedule_tx_packet(packet, 25 + (share_step * 25));
        share_step = (share_step + 1) & 0x03;
    } else {
        _mdns_dispatch_tx_packet(packet);
        _mdns_free_tx_packet(packet);
    }
}

/**
 * @brief  Check if question is already in the list
 */
static bool _mdns_question_exists(mdns_out_question_t *needle, mdns_out_question_t *haystack)
{
    while (haystack) {
        if (haystack->type == needle->type
                && haystack->host == needle->host
                && haystack->service == needle->service
                && haystack->proto == needle->proto) {
            return true;
        }
        haystack = haystack->next;
    }
    return false;
}

static bool _mdns_append_host(mdns_out_answer_t **destination, mdns_host_item_t *host, bool flush, bool bye)
{
    if (!_mdns_alloc_answer(destination, MDNS_TYPE_A, NULL, host, flush, bye)) {
        return false;
    }
    if (!_mdns_alloc_answer(destination, MDNS_TYPE_AAAA, NULL, host, flush, bye)) {
        return false;
    }
    return true;
}

static bool _mdns_append_host_list_in_services(mdns_out_answer_t **destination, mdns_srv_item_t *services[],
        size_t services_len, bool flush, bool bye)
{
    if (services == NULL) {
        mdns_host_item_t *host = mdns_get_host_item(_mdns_server->hostname);
        if (host != NULL) {
            return _mdns_append_host(destination, host, flush, bye);
        }
        return true;
    }
    for (size_t i = 0; i < services_len; i++) {
        mdns_host_item_t *host = mdns_get_host_item(services[i]->service->hostname);
        if (!_mdns_append_host(destination, host, flush, bye)) {
            return false;
        }
    }
    return true;
}

static bool _mdns_append_host_list(mdns_out_answer_t **destination, bool flush, bool bye)
{
    if (!_str_null_or_empty(_mdns_server->hostname)) {
        mdns_host_item_t *self_host = mdns_get_host_item(_mdns_server->hostname);
        if (!_mdns_append_host(destination, self_host, flush, bye)) {
            return false;
        }
    }
    mdns_host_item_t *host = _mdns_host_list;
    while (host != NULL) {
        host = host->next;
        if (!_mdns_append_host(destination, host, flush, bye)) {
            return false;
        }
    }
    return true;
}

static bool _mdns_append_host_question(mdns_out_question_t **questions, const char *hostname, bool unicast)
{
    mdns_out_question_t *q = (mdns_out_question_t *)malloc(sizeof(mdns_out_question_t));
    if (!q) {
        HOOK_MALLOC_FAILED;
        return false;
    }
    q->next = NULL;
    q->unicast = unicast;
    q->type = MDNS_TYPE_ANY;
    q->host = hostname;
    q->service = NULL;
    q->proto = NULL;
    q->domain = MDNS_DEFAULT_DOMAIN;
    q->own_dynamic_memory = false;
    if (_mdns_question_exists(q, *questions)) {
        free(q);
    } else {
        queueToEnd(mdns_out_question_t, *questions, q);
    }
    return true;
}

static bool _mdns_append_host_questions_for_services(mdns_out_question_t **questions, mdns_srv_item_t *services[],
        size_t len, bool unicast)
{
    if (!_str_null_or_empty(_mdns_server->hostname) &&
            !_mdns_append_host_question(questions, _mdns_server->hostname, unicast)) {
        return false;
    }
    for (size_t i = 0; i < len; i++) {
        if (!_mdns_append_host_question(questions, services[i]->service->hostname, unicast)) {
            return false;
        }
    }
    return true;
}

/**
 * @brief  Create probe packet for particular services on particular PCB
 */
static mdns_tx_packet_t *_mdns_create_probe_packet(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t *services[], size_t len, bool first, bool include_ip)
{
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(tcpip_if, ip_protocol);
    if (!packet) {
        return NULL;
    }

    size_t i;
    for (i = 0; i < len; i++) {
        mdns_out_question_t *q = (mdns_out_question_t *)malloc(sizeof(mdns_out_question_t));
        if (!q) {
            HOOK_MALLOC_FAILED;
            _mdns_free_tx_packet(packet);
            return NULL;
        }
        q->next = NULL;
        q->unicast = first;
        q->type = MDNS_TYPE_ANY;
        q->host = _mdns_get_service_instance_name(services[i]->service);
        q->service = services[i]->service->service;
        q->proto = services[i]->service->proto;
        q->domain = MDNS_DEFAULT_DOMAIN;
        q->own_dynamic_memory = false;
        if (!q->host || _mdns_question_exists(q, packet->questions)) {
            free(q);
            continue;
        } else {
            queueToEnd(mdns_out_question_t, packet->questions, q);
        }

        if (!q->host || !_mdns_alloc_answer(&packet->servers, MDNS_TYPE_SRV, services[i]->service, NULL, false, false)) {
            _mdns_free_tx_packet(packet);
            return NULL;
        }
    }

    if (include_ip) {
        if (!_mdns_append_host_questions_for_services(&packet->questions, services, len, first)) {
            _mdns_free_tx_packet(packet);
            return NULL;
        }

        if (!_mdns_append_host_list_in_services(&packet->servers, services, len, false, false)) {
            _mdns_free_tx_packet(packet);
            return NULL;
        }
    }

    return packet;
}

/**
 * @brief  Create announce packet for particular services on particular PCB
 */
static mdns_tx_packet_t *_mdns_create_announce_packet(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t *services[], size_t len, bool include_ip)
{
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(tcpip_if, ip_protocol);
    if (!packet) {
        return NULL;
    }
    packet->flags = MDNS_FLAGS_QR_AUTHORITATIVE;

    uint8_t i;
    for (i = 0; i < len; i++) {
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SDPTR, services[i]->service, NULL, false, false)
                || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_PTR, services[i]->service, NULL, false, false)
                || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SRV, services[i]->service, NULL, true, false)
                || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_TXT, services[i]->service, NULL, true, false)) {
            _mdns_free_tx_packet(packet);
            return NULL;
        }
    }
    if (include_ip) {
        if (!_mdns_append_host_list_in_services(&packet->servers, services, len, true, false)) {
            _mdns_free_tx_packet(packet);
            return NULL;
        }
    }
    return packet;
}

/**
 * @brief  Convert probe packet to announce
 */
static mdns_tx_packet_t *_mdns_create_announce_from_probe(mdns_tx_packet_t *probe)
{
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(probe->tcpip_if, probe->ip_protocol);
    if (!packet) {
        return NULL;
    }
    packet->flags = MDNS_FLAGS_QR_AUTHORITATIVE;

    mdns_out_answer_t *s = probe->servers;
    while (s) {
        if (s->type == MDNS_TYPE_SRV) {
            if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SDPTR, s->service, NULL, false, false)
                    || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_PTR, s->service, NULL, false, false)
                    || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_SRV, s->service, NULL, true, false)
                    || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_TXT, s->service, NULL, true, false)) {
                _mdns_free_tx_packet(packet);
                return NULL;
            }
            mdns_host_item_t *host = mdns_get_host_item(s->service->hostname);
            if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_A, NULL, host, true, false)
                    || !_mdns_alloc_answer(&packet->answers, MDNS_TYPE_AAAA, NULL, host, true, false)) {
                _mdns_free_tx_packet(packet);
                return NULL;
            }

        } else if (s->type == MDNS_TYPE_A || s->type == MDNS_TYPE_AAAA) {
            if (!_mdns_alloc_answer(&packet->answers, s->type, NULL, s->host, true, false)) {
                _mdns_free_tx_packet(packet);
                return NULL;
            }
        }

        s = s->next;
    }
    return packet;
}

/**
 * @brief  Send by for particular services on particular PCB
 */
static void _mdns_pcb_send_bye(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t **services, size_t len, bool include_ip)
{
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(tcpip_if, ip_protocol);
    if (!packet) {
        return;
    }
    packet->flags = MDNS_FLAGS_QR_AUTHORITATIVE;
    size_t i;
    for (i = 0; i < len; i++) {
        if (!_mdns_alloc_answer(&packet->answers, MDNS_TYPE_PTR, services[i]->service, NULL, true, true)) {
            _mdns_free_tx_packet(packet);
            return;
        }
    }
    if (include_ip) {
        _mdns_append_host_list_in_services(&packet->answers, services, len, true, true);
    }
    _mdns_dispatch_tx_packet(packet);
    _mdns_free_tx_packet(packet);
}

/**
 * @brief  Send probe for additional services on particular PCB
 */
static void _mdns_init_pcb_probe_new_service(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t **services, size_t len, bool probe_ip)
{
    mdns_pcb_t *pcb = &_mdns_server->interfaces[tcpip_if].pcbs[ip_protocol];
    size_t services_final_len = len;

    if (PCB_STATE_IS_PROBING(pcb)) {
        services_final_len += pcb->probe_services_len;
    }
    mdns_srv_item_t **_services = NULL;
    if (services_final_len) {
        _services = (mdns_srv_item_t **)malloc(sizeof(mdns_srv_item_t *) * services_final_len);
        if (!_services) {
            HOOK_MALLOC_FAILED;
            return;
        }

        size_t i;
        for (i = 0; i < len; i++) {
            _services[i] = services[i];
        }
        if (pcb->probe_services) {
            for (i = 0; i < pcb->probe_services_len; i++) {
                _services[len + i] = pcb->probe_services[i];
            }
            free(pcb->probe_services);
        }
    }

    probe_ip = pcb->probe_ip || probe_ip;

    pcb->probe_ip = false;
    pcb->probe_services = NULL;
    pcb->probe_services_len = 0;
    pcb->probe_running = false;

    mdns_tx_packet_t *packet = _mdns_create_probe_packet(tcpip_if, ip_protocol, _services, services_final_len, true, probe_ip);
    if (!packet) {
        free(_services);
        return;
    }

    pcb->probe_ip = probe_ip;
    pcb->probe_services = _services;
    pcb->probe_services_len = services_final_len;
    pcb->probe_running = true;
    _mdns_schedule_tx_packet(packet, ((pcb->failed_probes > 5) ? 1000 : 120) + (esp_random() & 0x7F));
    pcb->state = PCB_PROBE_1;
}

/**
 * @brief  Send probe for particular services on particular PCB
 *
 * Tests possible duplication on probing service structure and probes only for new entries.
 * - If pcb probing then add only non-probing services and restarts probing
 * - If pcb not probing, run probing for all specified services
 */
static void _mdns_init_pcb_probe(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t **services, size_t len, bool probe_ip)
{
    mdns_pcb_t *pcb = &_mdns_server->interfaces[tcpip_if].pcbs[ip_protocol];

    _mdns_clear_pcb_tx_queue_head(tcpip_if, ip_protocol);

    if (_str_null_or_empty(_mdns_server->hostname)) {
        pcb->state = PCB_RUNNING;
        return;
    }

    if (PCB_STATE_IS_PROBING(pcb)) {
        // Looking for already probing services to resolve duplications
        mdns_srv_item_t *new_probe_services[len];
        int new_probe_service_len = 0;
        bool found;
        for (size_t j = 0; j < len; ++j) {
            found = false;
            for (int i = 0; i < pcb->probe_services_len; ++i) {
                if (pcb->probe_services[i] == services[j]) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                new_probe_services[new_probe_service_len++] = services[j];
            }
        }
        // init probing for newly added services
        _mdns_init_pcb_probe_new_service(tcpip_if, ip_protocol,
                                         new_probe_service_len ? new_probe_services : NULL, new_probe_service_len, probe_ip);
    } else {
        // not probing, so init for all services
        _mdns_init_pcb_probe_new_service(tcpip_if, ip_protocol, services, len, probe_ip);
    }
}

/**
 * @brief  Restart the responder on particular PCB
 */
static void _mdns_restart_pcb(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    size_t srv_count = 0;
    mdns_srv_item_t *a = _mdns_server->services;
    while (a) {
        srv_count++;
        a = a->next;
    }
    mdns_srv_item_t *services[srv_count];
    size_t i = 0;
    a = _mdns_server->services;
    while (a) {
        services[i++] = a;
        a = a->next;
    }
    _mdns_init_pcb_probe(tcpip_if, ip_protocol, services, srv_count, true);
}

/**
 * @brief  Send by for particular services
 */
static void _mdns_send_bye(mdns_srv_item_t **services, size_t len, bool include_ip)
{
    uint8_t i, j;
    if (_str_null_or_empty(_mdns_server->hostname)) {
        return;
    }

    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        for (j = 0; j < MDNS_IP_PROTOCOL_MAX; j++) {
            if (mdns_is_netif_ready(i, j) && _mdns_server->interfaces[i].pcbs[j].state == PCB_RUNNING) {
                _mdns_pcb_send_bye((mdns_if_t)i, (mdns_ip_protocol_t)j, services, len, include_ip);
            }
        }
    }
}

/**
 * @brief  Send announcement on particular PCB
 */
static void _mdns_announce_pcb(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, mdns_srv_item_t **services, size_t len, bool include_ip)
{
    mdns_pcb_t *_pcb = &_mdns_server->interfaces[tcpip_if].pcbs[ip_protocol];
    size_t i;
    if (mdns_is_netif_ready(tcpip_if, ip_protocol)) {
        if (PCB_STATE_IS_PROBING(_pcb)) {
            _mdns_init_pcb_probe(tcpip_if, ip_protocol, services, len, include_ip);
        } else if (PCB_STATE_IS_ANNOUNCING(_pcb)) {
            mdns_tx_packet_t   *p = _mdns_get_next_pcb_packet(tcpip_if, ip_protocol);
            if (p) {
                for (i = 0; i < len; i++) {
                    if (!_mdns_alloc_answer(&p->answers, MDNS_TYPE_SDPTR, services[i]->service, NULL, false, false)
                            || !_mdns_alloc_answer(&p->answers, MDNS_TYPE_PTR, services[i]->service, NULL, false, false)
                            || !_mdns_alloc_answer(&p->answers, MDNS_TYPE_SRV, services[i]->service, NULL, true, false)
                            || !_mdns_alloc_answer(&p->answers, MDNS_TYPE_TXT, services[i]->service, NULL, true, false)) {
                        break;
                    }
                }
                if (include_ip) {
                    _mdns_dealloc_answer(&p->additional, MDNS_TYPE_A, NULL);
                    _mdns_dealloc_answer(&p->additional, MDNS_TYPE_AAAA, NULL);
                    _mdns_append_host_list_in_services(&p->answers, services, len, true, false);
                }
                _pcb->state = PCB_ANNOUNCE_1;
            }
        } else if (_pcb->state == PCB_RUNNING) {

            if (_str_null_or_empty(_mdns_server->hostname)) {
                return;
            }

            _pcb->state = PCB_ANNOUNCE_1;
            mdns_tx_packet_t *p = _mdns_create_announce_packet(tcpip_if, ip_protocol, services, len, include_ip);
            if (p) {
                _mdns_schedule_tx_packet(p, 0);
            }
        }
    }
}

/**
 * @brief  Send probe on all active PCBs
 */
static void _mdns_probe_all_pcbs(mdns_srv_item_t **services, size_t len, bool probe_ip, bool clear_old_probe)
{
    uint8_t i, j;
    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        for (j = 0; j < MDNS_IP_PROTOCOL_MAX; j++) {
            if (mdns_is_netif_ready(i, j)) {
                mdns_pcb_t *_pcb = &_mdns_server->interfaces[i].pcbs[j];
                if (clear_old_probe) {
                    free(_pcb->probe_services);
                    _pcb->probe_services = NULL;
                    _pcb->probe_services_len = 0;
                    _pcb->probe_running = false;
                }
                _mdns_init_pcb_probe((mdns_if_t)i, (mdns_ip_protocol_t)j, services, len, probe_ip);
            }
        }
    }
}

/**
 * @brief  Send announcement on all active PCBs
 */
static void _mdns_announce_all_pcbs(mdns_srv_item_t **services, size_t len, bool include_ip)
{
    uint8_t i, j;
    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        for (j = 0; j < MDNS_IP_PROTOCOL_MAX; j++) {
            _mdns_announce_pcb((mdns_if_t)i, (mdns_ip_protocol_t)j, services, len, include_ip);
        }
    }
}

/**
 * @brief  Restart the responder on all active PCBs
 */
static void _mdns_send_final_bye(bool include_ip)
{
    //collect all services and start probe
    size_t srv_count = 0;
    mdns_srv_item_t *a = _mdns_server->services;
    while (a) {
        srv_count++;
        a = a->next;
    }
    if (!srv_count) {
        return;
    }
    mdns_srv_item_t *services[srv_count];
    size_t i = 0;
    a = _mdns_server->services;
    while (a) {
        services[i++] = a;
        a = a->next;
    }
    _mdns_send_bye(services, srv_count, include_ip);
}

/**
 * @brief  Stop the responder on all services without instance
 */
static void _mdns_send_bye_all_pcbs_no_instance(bool include_ip)
{
    size_t srv_count = 0;
    mdns_srv_item_t *a = _mdns_server->services;
    while (a) {
        if (!a->service->instance) {
            srv_count++;
        }
        a = a->next;
    }
    if (!srv_count) {
        return;
    }
    mdns_srv_item_t *services[srv_count];
    size_t i = 0;
    a = _mdns_server->services;
    while (a) {
        if (!a->service->instance) {
            services[i++] = a;
        }
        a = a->next;
    }
    _mdns_send_bye(services, srv_count, include_ip);
}

/**
 * @brief  Restart the responder on all services without instance
 */
static void _mdns_restart_all_pcbs_no_instance(void)
{
    size_t srv_count = 0;
    mdns_srv_item_t *a = _mdns_server->services;
    while (a) {
        if (!a->service->instance) {
            srv_count++;
        }
        a = a->next;
    }
    if (!srv_count) {
        return;
    }
    mdns_srv_item_t *services[srv_count];
    size_t i = 0;
    a = _mdns_server->services;
    while (a) {
        if (!a->service->instance) {
            services[i++] = a;
        }
        a = a->next;
    }
    _mdns_probe_all_pcbs(services, srv_count, false, true);
}

/**
 * @brief  Restart the responder on all active PCBs
 */
static void _mdns_restart_all_pcbs(void)
{
    _mdns_clear_tx_queue_head();
    size_t srv_count = 0;
    mdns_srv_item_t *a = _mdns_server->services;
    while (a) {
        srv_count++;
        a = a->next;
    }
    mdns_srv_item_t *services[srv_count];
    size_t l = 0;
    a = _mdns_server->services;
    while (a) {
        services[l++] = a;
        a = a->next;
    }

    _mdns_probe_all_pcbs(services, srv_count, true, true);
}



/**
 * @brief  creates/allocates new text item list
 * @param  num_items     service number of txt items or 0
 * @param  txt           service txt items array or NULL
 *
 * @return pointer to the linked txt item list or NULL
 */
static mdns_txt_linked_item_t *_mdns_allocate_txt(size_t num_items, mdns_txt_item_t txt[])
{
    mdns_txt_linked_item_t *new_txt = NULL;
    size_t i = 0;
    if (num_items) {
        for (i = 0; i < num_items; i++) {
            mdns_txt_linked_item_t *new_item = (mdns_txt_linked_item_t *)malloc(sizeof(mdns_txt_linked_item_t));
            if (!new_item) {
                HOOK_MALLOC_FAILED;
                break;
            }
            new_item->key = strdup(txt[i].key);
            if (!new_item->key) {
                free(new_item);
                break;
            }
            new_item->value = strdup(txt[i].value);
            if (!new_item->value) {
                free((char *)new_item->key);
                free(new_item);
                break;
            }
            new_item->value_len = strlen(new_item->value);
            new_item->next = new_txt;
            new_txt = new_item;
        }
    }
    return new_txt;
}

/**
 * @brief Deallocate the txt linked list
 * @param txt pointer to the txt pointer to free, noop if txt==NULL
 */
static void _mdns_free_linked_txt(mdns_txt_linked_item_t *txt)
{
    mdns_txt_linked_item_t *t;
    while (txt) {
        t = txt;
        txt = txt->next;
        free((char *)t->value);
        free((char *)t->key);
        free(t);
    }
}

/**
 * @brief  creates/allocates new service
 * @param  service       service type
 * @param  proto         service proto
 * @param  hostname      service hostname
 * @param  port          service port
 * @param  instance      service instance
 * @param  num_items     service number of txt items or 0
 * @param  txt           service txt items array or NULL
 *
 * @return pointer to the service or NULL on error
 */
static mdns_service_t *_mdns_create_service(const char *service, const char *proto, const char *hostname,
        uint16_t port, const char *instance, size_t num_items,
        mdns_txt_item_t txt[])
{
    mdns_service_t *s = (mdns_service_t *)calloc(1, sizeof(mdns_service_t));
    if (!s) {
        HOOK_MALLOC_FAILED;
        return NULL;
    }

    mdns_txt_linked_item_t *new_txt = _mdns_allocate_txt(num_items, txt);
    if (num_items && new_txt == NULL) {
        goto fail;
    }

    s->priority = 0;
    s->weight = 0;
    s->instance = instance ? strndup(instance, MDNS_NAME_BUF_LEN - 1) : NULL;
    s->txt = new_txt;
    s->port = port;
    s->subtype = NULL;

    if (hostname) {
        s->hostname = strndup(hostname, MDNS_NAME_BUF_LEN - 1);
        if (!s->hostname) {
            goto fail;
        }
    } else {
        s->hostname = NULL;
    }

    s->service = strndup(service, MDNS_NAME_BUF_LEN - 1);
    if (!s->service) {
        goto fail;
    }

    s->proto = strndup(proto, MDNS_NAME_BUF_LEN - 1);
    if (!s->proto) {
        goto fail;
    }
    return s;

fail:
    _mdns_free_linked_txt(s->txt);
    free((char *)s->instance);
    free((char *)s->service);
    free((char *)s->proto);
    free((char *)s->hostname);
    free(s);

    return NULL;
}

/**
 * @brief  Remove and free service answer from answer list (destination)
 */
static void _mdns_dealloc_scheduled_service_answers(mdns_out_answer_t **destination, mdns_service_t *service)
{
    mdns_out_answer_t *d = *destination;
    if (!d) {
        return;
    }
    while (d && d->service == service) {
        *destination = d->next;
        free(d);
        d = *destination;
    }
    while (d && d->next) {
        mdns_out_answer_t *a = d->next;
        if (a->service == service) {
            d->next = a->next;
            free(a);
        } else {
            d = d->next;
        }
    }
}

/**
 * @brief  Find, remove and free answers and scheduled packets for service
 */
static void _mdns_remove_scheduled_service_packets(mdns_service_t *service)
{
    if (!service) {
        return;
    }
    mdns_tx_packet_t *p = NULL;
    mdns_tx_packet_t *q = _mdns_server->tx_queue_head;
    while (q) {
        bool had_answers = (q->answers != NULL);

        _mdns_dealloc_scheduled_service_answers(&(q->answers), service);
        _mdns_dealloc_scheduled_service_answers(&(q->additional), service);
        _mdns_dealloc_scheduled_service_answers(&(q->servers), service);


        mdns_pcb_t *_pcb = &_mdns_server->interfaces[q->tcpip_if].pcbs[q->ip_protocol];
        if (mdns_is_netif_ready(q->tcpip_if, q->ip_protocol)) {
            if (PCB_STATE_IS_PROBING(_pcb)) {
                uint8_t i;
                //check if we are probing this service
                for (i = 0; i < _pcb->probe_services_len; i++) {
                    mdns_srv_item_t *s = _pcb->probe_services[i];
                    if (s->service == service) {
                        break;
                    }
                }
                if (i < _pcb->probe_services_len) {
                    if (_pcb->probe_services_len > 1) {
                        uint8_t n;
                        for (n = (i + 1); n < _pcb->probe_services_len; n++) {
                            _pcb->probe_services[n - 1] = _pcb->probe_services[n];
                        }
                        _pcb->probe_services_len--;
                    } else {
                        _pcb->probe_services_len = 0;
                        free(_pcb->probe_services);
                        _pcb->probe_services = NULL;
                        if (!_pcb->probe_ip) {
                            _pcb->probe_running = false;
                            _pcb->state = PCB_RUNNING;
                        }
                    }

                    if (q->questions) {
                        mdns_out_question_t *qsn = NULL;
                        mdns_out_question_t *qs = q->questions;
                        if (qs->type == MDNS_TYPE_ANY
                                && qs->service && strcmp(qs->service, service->service) == 0
                                && qs->proto && strcmp(qs->proto, service->proto) == 0) {
                            q->questions = q->questions->next;
                            free(qs);
                        } else while (qs->next) {
                                qsn = qs->next;
                                if (qsn->type == MDNS_TYPE_ANY
                                        && qsn->service && strcmp(qsn->service, service->service) == 0
                                        && qsn->proto && strcmp(qsn->proto, service->proto) == 0) {
                                    qs->next = qsn->next;
                                    free(qsn);
                                    break;
                                }
                                qs = qs->next;
                            }
                    }
                }
            } else if (PCB_STATE_IS_ANNOUNCING(_pcb)) {
                //if answers were cleared, set to running
                if (had_answers && q->answers == NULL) {
                    _pcb->state = PCB_RUNNING;
                }
            }
        }

        p = q;
        q = q->next;
        if (!p->questions && !p->answers && !p->additional && !p->servers) {
            queueDetach(mdns_tx_packet_t, _mdns_server->tx_queue_head, p);
            _mdns_free_tx_packet(p);
        }
    }
}

/**
 * @brief  free service memory
 *
 * @param  service      the service
 */
static void _mdns_free_service(mdns_service_t *service)
{
    if (!service) {
        return;
    }
    free((char *)service->instance);
    free((char *)service->service);
    free((char *)service->proto);
    free((char *)service->hostname);
    while (service->txt) {
        mdns_txt_linked_item_t *s = service->txt;
        service->txt = service->txt->next;
        free((char *)s->key);
        free((char *)s->value);
        free(s);
    }
    while (service->subtype) {
        mdns_subtype_t *next = service->subtype->next;
        free((char *)service->subtype->subtype);
        free(service->subtype);
        service->subtype = next;
    }
    free(service);
}


/*
 * Received Packet Handling
 * */

/**
 * @brief  Detect SRV collision
 */
static int _mdns_check_srv_collision(mdns_service_t *service, uint16_t priority, uint16_t weight, uint16_t port, const char *host, const char *domain)
{
    if (_str_null_or_empty(_mdns_server->hostname)) {
        return 0;
    }

    size_t our_host_len = strlen(_mdns_server->hostname);
    size_t our_len = 14 + our_host_len;

    size_t their_host_len = strlen(host);
    size_t their_domain_len = strlen(domain);
    size_t their_len = 9 + their_host_len + their_domain_len;

    if (their_len > our_len) {
        return 1;//they win
    } else if (their_len < our_len) {
        return -1;//we win
    }

    uint16_t our_index = 0;
    uint8_t our_data[our_len];
    _mdns_append_u16(our_data, &our_index, service->priority);
    _mdns_append_u16(our_data, &our_index, service->weight);
    _mdns_append_u16(our_data, &our_index, service->port);
    our_data[our_index++] = our_host_len;
    memcpy(our_data + our_index, _mdns_server->hostname, our_host_len);
    our_index += our_host_len;
    our_data[our_index++] = 5;
    memcpy(our_data + our_index, MDNS_DEFAULT_DOMAIN, 5);
    our_index += 5;
    our_data[our_index++] = 0;

    uint16_t their_index = 0;
    uint8_t their_data[their_len];
    _mdns_append_u16(their_data, &their_index, priority);
    _mdns_append_u16(their_data, &their_index, weight);
    _mdns_append_u16(their_data, &their_index, port);
    their_data[their_index++] = their_host_len;
    memcpy(their_data + their_index, host, their_host_len);
    their_index += their_host_len;
    their_data[their_index++] = their_domain_len;
    memcpy(their_data + their_index, domain, their_domain_len);
    their_index += their_domain_len;
    their_data[their_index++] = 0;

    int ret = memcmp(our_data, their_data, our_len);
    if (ret > 0) {
        return -1;//we win
    } else if (ret < 0) {
        return 1;//they win
    }
    return 0;//same
}

/**
 * @brief  Detect TXT collision
 */
static int _mdns_check_txt_collision(mdns_service_t *service, const uint8_t *data, size_t len)
{
    size_t data_len = 0;
    if (len == 1 && service->txt) {
        return -1;//we win
    } else if (len > 1 && !service->txt) {
        return 1;//they win
    } else if (len == 1 && !service->txt) {
        return 0;//same
    }

    mdns_txt_linked_item_t *txt = service->txt;
    while (txt) {
        data_len += 1 /* record-len */ + strlen(txt->key) + txt->value_len + (txt->value ? 1 : 0 /* "=" */);
        txt = txt->next;
    }

    if (len > data_len) {
        return 1;//they win
    } else if (len < data_len) {
        return -1;//we win
    }

    uint8_t ours[len];
    uint16_t index = 0;

    txt = service->txt;
    while (txt) {
        append_one_txt_record_entry(ours, &index, txt);
        txt = txt->next;
    }

    int ret = memcmp(ours, data, len);
    if (ret > 0) {
        return -1;//we win
    } else if (ret < 0) {
        return 1;//they win
    }
    return 0;//same
}

static esp_err_t mdns_pcb_deinit_local(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_proto)
{
    esp_err_t err = _mdns_pcb_deinit(tcpip_if, ip_proto);
    mdns_pcb_t *_pcb = &_mdns_server->interfaces[tcpip_if].pcbs[ip_proto];
    if (_pcb == NULL || err != ESP_OK) {
        return err;
    }
    free(_pcb->probe_services);
    _pcb->state = PCB_OFF;
    _pcb->probe_ip = false;
    _pcb->probe_services = NULL;
    _pcb->probe_services_len = 0;
    _pcb->probe_running = false;
    _pcb->failed_probes = 0;
    return ESP_OK;
}
/**
 * @brief  Set interface as duplicate if another is found on the same subnet
 */
static void _mdns_dup_interface(mdns_if_t tcpip_if)
{
    uint8_t i;
    mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
    if (other_if == MDNS_MAX_INTERFACES) {
        return; // no other interface found
    }
    for (i = 0; i < MDNS_IP_PROTOCOL_MAX; i++) {
        if (mdns_is_netif_ready(other_if, i)) {
            //stop this interface and mark as dup
            if (mdns_is_netif_ready(tcpip_if, i)) {
                _mdns_clear_pcb_tx_queue_head(tcpip_if, i);
                mdns_pcb_deinit_local(tcpip_if, i);
            }
            _mdns_server->interfaces[tcpip_if].pcbs[i].state = PCB_DUP;
            _mdns_announce_pcb(other_if, i, NULL, 0, true);
        }
    }
}

/**
 * @brief  Detect IPv4 address collision
 */
static int _mdns_check_a_collision(esp_ip4_addr_t *ip, mdns_if_t tcpip_if)
{
    esp_netif_ip_info_t if_ip_info;
    esp_netif_ip_info_t other_ip_info;
    if (!ip->addr) {
        return 1;//denial! they win
    }
    if (esp_netif_get_ip_info(_mdns_get_esp_netif(tcpip_if), &if_ip_info)) {
        return 1;//they win
    }

    int ret = memcmp((uint8_t *)&if_ip_info.ip.addr, (uint8_t *)&ip->addr, sizeof(esp_ip4_addr_t));
    if (ret > 0) {
        return -1;//we win
    } else if (ret < 0) {
        //is it the other interface?
        mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
        if (other_if == MDNS_MAX_INTERFACES) {
            return 1;//AP interface! They win
        }
        if (esp_netif_get_ip_info(_mdns_get_esp_netif(other_if), &other_ip_info)) {
            return 1;//IPv4 not active! They win
        }
        if (ip->addr != other_ip_info.ip.addr) {
            return 1;//IPv4 not ours! They win
        }
        _mdns_dup_interface(tcpip_if);
        return 2;//they win
    }
    return 0;//same
}

#if CONFIG_LWIP_IPV6
/**
 * @brief  Detect IPv6 address collision
 */
static int _mdns_check_aaaa_collision(esp_ip6_addr_t *ip, mdns_if_t tcpip_if)
{
    struct esp_ip6_addr if_ip6;
    struct esp_ip6_addr other_ip6;
    if (_ipv6_address_is_zero(*ip)) {
        return 1;//denial! they win
    }
    if (esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(tcpip_if), &if_ip6)) {
        return 1;//they win
    }
    int ret = memcmp((uint8_t *)&if_ip6.addr, (uint8_t *)ip->addr, _MDNS_SIZEOF_IP6_ADDR);
    if (ret > 0) {
        return -1;//we win
    } else if (ret < 0) {
        //is it the other interface?
        mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
        if (other_if == MDNS_MAX_INTERFACES) {
            return 1;//AP interface! They win
        }
        if (esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(other_if), &other_ip6)) {
            return 1;//IPv6 not active! They win
        }
        if (memcmp((uint8_t *)&other_ip6.addr, (uint8_t *)ip->addr, _MDNS_SIZEOF_IP6_ADDR)) {
            return 1;//IPv6 not ours! They win
        }
        _mdns_dup_interface(tcpip_if);
        return 2;//they win
    }
    return 0;//same
}
#endif

static bool _hostname_is_ours(const char *hostname)
{
    if (!_str_null_or_empty(_mdns_server->hostname) &&
            strcasecmp(hostname, _mdns_server->hostname) == 0) {
        return true;
    }
    mdns_host_item_t *host = _mdns_host_list;
    while (host != NULL) {
        if (strcasecmp(hostname, host->hostname) == 0) {
            return true;
        }
        host = host->next;
    }
    return false;
}

/**
 * @brief Adds a delegated hostname to the linked list
 * @param hostname Host name pointer
 * @param address_list Address list
 * @return  true on success
 *          false if the host wasn't attached (this is our hostname, or alloc failure) so we have to free the structs
 */
static bool _mdns_delegate_hostname_add(const char *hostname, mdns_ip_addr_t *address_list)
{
    if (_hostname_is_ours(hostname)) {
        return false;
    }

    mdns_host_item_t *host = (mdns_host_item_t *)malloc(sizeof(mdns_host_item_t));

    if (host == NULL) {
        return false;
    }
    host->address_list = address_list;
    host->hostname = hostname;
    host->next = _mdns_host_list;
    _mdns_host_list = host;
    return true;
}

static void free_address_list(mdns_ip_addr_t *address_list)
{
    while (address_list != NULL) {
        mdns_ip_addr_t *next = address_list->next;
        free(address_list);
        address_list = next;
    }
}


static bool _mdns_delegate_hostname_set_address(const char *hostname, mdns_ip_addr_t *address_list)
{
    if (!_str_null_or_empty(_mdns_server->hostname) &&
            strcasecmp(hostname, _mdns_server->hostname) == 0) {
        return false;
    }
    mdns_host_item_t *host = _mdns_host_list;
    while (host != NULL) {
        if (strcasecmp(hostname, host->hostname) == 0) {
            // free previous address list
            free_address_list(host->address_list);
            // set current address list to the host
            host->address_list = address_list;
            return true;
        }
        host = host->next;
    }
    return false;
}

static mdns_ip_addr_t *copy_address_list(const mdns_ip_addr_t *address_list)
{
    mdns_ip_addr_t *head = NULL;
    mdns_ip_addr_t *tail = NULL;
    while (address_list != NULL) {
        mdns_ip_addr_t *addr = (mdns_ip_addr_t *)malloc(sizeof(mdns_ip_addr_t));
        if (addr == NULL) {
            free_address_list(head);
            return NULL;
        }
        addr->addr = address_list->addr;
        addr->next = NULL;
        if (head == NULL) {
            head = addr;
            tail = addr;
        } else {
            tail->next = addr;
            tail = tail->next;
        }
        address_list = address_list->next;
    }
    return head;
}

static void free_delegated_hostnames(void)
{
    mdns_host_item_t *host = _mdns_host_list;
    while (host != NULL) {
        free_address_list(host->address_list);
        free((char *)host->hostname);
        mdns_host_item_t *item = host;
        host = host->next;
        free(item);
    }
}

static bool _mdns_delegate_hostname_remove(const char *hostname)
{
    mdns_srv_item_t *srv = _mdns_server->services;
    mdns_srv_item_t *prev_srv = NULL;
    while (srv) {
        if (strcasecmp(srv->service->hostname, hostname) == 0) {
            mdns_srv_item_t *to_free = srv;
            _mdns_send_bye(&srv, 1, false);
            _mdns_remove_scheduled_service_packets(srv->service);
            if (prev_srv == NULL) {
                _mdns_server->services = srv->next;
                srv = srv->next;
            } else {
                prev_srv->next = srv->next;
                srv = srv->next;
            }
            _mdns_free_service(to_free->service);
            free(to_free);
        } else {
            prev_srv = srv;
            srv = srv->next;
        }
    }
    mdns_host_item_t *host = _mdns_host_list;
    mdns_host_item_t *prev_host = NULL;
    while (host != NULL) {
        if (strcasecmp(hostname, host->hostname) == 0) {
            if (prev_host == NULL) {
                _mdns_host_list = host->next;
            } else {
                prev_host->next = host->next;
            }
            free_address_list(host->address_list);
            free((char *)host->hostname);
            free(host);
            break;
        } else {
            prev_host = host;
            host = host->next;
        }
    }
    return true;
}

/**
 * @brief  Check if parsed name is discovery
 */
static bool _mdns_name_is_discovery(mdns_name_t *name, uint16_t type)
{
    return (
               (name->host[0] && !strcasecmp(name->host, "_services"))
               && (name->service[0] && !strcasecmp(name->service, "_dns-sd"))
               && (name->proto[0] && !strcasecmp(name->proto, "_udp"))
               && (name->domain[0] && !strcasecmp(name->domain, MDNS_DEFAULT_DOMAIN))
               && type == MDNS_TYPE_PTR
           );
}

/**
 * @brief  Check if the parsed name is self-hosted, i.e. we should resolve conflicts
 */
static bool _mdns_name_is_selfhosted(mdns_name_t *name)
{
    if (_str_null_or_empty(_mdns_server->hostname)) { // self-hostname needs to be defined
        return false;
    }

    // hostname only -- check if selfhosted name
    if (_str_null_or_empty(name->service) && _str_null_or_empty(name->proto) &&
            strcasecmp(name->host, _mdns_server->hostname) == 0 ) {
        return true;
    }

    // service -- check if selfhosted service
    mdns_srv_item_t *srv = _mdns_get_service_item(name->service, name->proto, NULL);
    if (srv && strcasecmp(_mdns_server->hostname, srv->service->hostname) == 0) {
        return true;
    }
    return false;
}

/**
 * @brief  Check if the parsed name is ours (matches service or host name)
 */
static bool _mdns_name_is_ours(mdns_name_t *name)
{
    //domain have to be "local"
    if (_str_null_or_empty(name->domain) || ( strcasecmp(name->domain, MDNS_DEFAULT_DOMAIN)
#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
            && strcasecmp(name->domain, "arpa")
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
                                            ) ) {
        return false;
    }

    //if service and proto are empty, host must match out hostname
    if (_str_null_or_empty(name->service) && _str_null_or_empty(name->proto)) {
        if (!_str_null_or_empty(name->host)
                && !_str_null_or_empty(_mdns_server->hostname)
                && _hostname_is_ours(name->host)) {
            return true;
        }
        return false;
    }

    //if service or proto is empty, name is invalid
    if (_str_null_or_empty(name->service) || _str_null_or_empty(name->proto)) {
        return false;
    }


    //find the service
    mdns_srv_item_t *service;
    if (name->sub) {
        service = _mdns_get_service_item_subtype(name->host, name->service, name->proto);
    } else if (_str_null_or_empty(name->host)) {
        service = _mdns_get_service_item(name->service, name->proto, NULL);
    } else {
        service = _mdns_get_service_item_instance(name->host, name->service, name->proto, NULL);
    }
    if (!service) {
        return false;
    }

    //if query is PTR query and we have service, we have success
    if (name->sub || _str_null_or_empty(name->host)) {
        return true;
    }

    //OK we have host in the name. find what is the instance of the service
    const char *instance = _mdns_get_service_instance_name(service->service);
    if (instance == NULL) {
        return false;
    }

    //compare the instance against the name
    if (strcasecmp(name->host, instance) == 0) {
        return true;
    }

    return false;
}

/**
 * @brief  read uint16_t from a packet
 * @param  packet       the packet
 * @param  index        index in the packet where the value starts
 *
 * @return the value
 */
static inline uint16_t _mdns_read_u16(const uint8_t *packet, uint16_t index)
{
    return (uint16_t)(packet[index]) << 8 | packet[index + 1];
}

/**
 * @brief  read uint32_t from a packet
 * @param  packet       the packet
 * @param  index        index in the packet where the value starts
 *
 * @return the value
 */
static inline uint32_t _mdns_read_u32(const uint8_t *packet, uint16_t index)
{
    return (uint32_t)(packet[index]) << 24 | (uint32_t)(packet[index + 1]) << 16 | (uint32_t)(packet[index + 2]) << 8 | packet[index + 3];
}

/**
 * @brief  reads and formats MDNS FQDN into mdns_name_t structure
 *
 * @param  packet       MDNS packet
 * @param  start        Starting point of FQDN
 * @param  name         mdns_name_t structure to populate
 *
 * @return the address after the parsed FQDN in the packet or NULL on error
 */
static const uint8_t *_mdns_parse_fqdn(const uint8_t *packet, const uint8_t *start, mdns_name_t *name, size_t packet_len)
{
    name->parts = 0;
    name->sub = 0;
    name->host[0] = 0;
    name->service[0] = 0;
    name->proto[0] = 0;
    name->domain[0] = 0;
    name->invalid = false;

    static char buf[MDNS_NAME_BUF_LEN];

    const uint8_t *next_data = (uint8_t *)_mdns_read_fqdn(packet, start, name, buf, packet_len);
    if (!next_data) {
        return 0;
    }
    if (!name->parts || name->invalid) {
        return next_data;
    }
    if (name->parts == 3) {
        memmove((uint8_t *)name + (MDNS_NAME_BUF_LEN), (uint8_t *)name, 3 * (MDNS_NAME_BUF_LEN));
        name->host[0] = 0;
    } else if (name->parts == 2) {
        memmove((uint8_t *)(name->domain), (uint8_t *)(name->service), (MDNS_NAME_BUF_LEN));
        name->service[0] = 0;
        name->proto[0] = 0;
    }
    if (strcasecmp(name->domain, MDNS_DEFAULT_DOMAIN) == 0 || strcasecmp(name->domain, "arpa") == 0) {
        return next_data;
    }
    name->invalid = true; // mark the current name invalid, but continue with other question
    return next_data;
}

/**
 * @brief  Called from parser to check if question matches particular service
 */
static bool _mdns_question_matches(mdns_parsed_question_t *question, uint16_t type, mdns_srv_item_t *service)
{
    if (question->type != type) {
        return false;
    }
    if (type == MDNS_TYPE_A || type == MDNS_TYPE_AAAA) {
        return true;
    } else if (type == MDNS_TYPE_PTR || type == MDNS_TYPE_SDPTR) {
        if (question->service && question->proto && question->domain
                && !strcasecmp(service->service->service, question->service)
                && !strcasecmp(service->service->proto, question->proto)
                && !strcasecmp(MDNS_DEFAULT_DOMAIN, question->domain)) {
            return true;
        }
    } else if (service && (type == MDNS_TYPE_SRV || type == MDNS_TYPE_TXT)) {
        const char *name = _mdns_get_service_instance_name(service->service);
        if (name && question->host && question->service && question->proto && question->domain
                && !strcasecmp(name, question->host)
                && !strcasecmp(service->service->service, question->service)
                && !strcasecmp(service->service->proto, question->proto)
                && !strcasecmp(MDNS_DEFAULT_DOMAIN, question->domain)) {
            return true;
        }
    }

    return false;
}

/**
 * @brief  Removes saved question from parsed data
 */
static void _mdns_remove_parsed_question(mdns_parsed_packet_t *parsed_packet, uint16_t type, mdns_srv_item_t *service)
{
    mdns_parsed_question_t *q = parsed_packet->questions;

    if (_mdns_question_matches(q, type, service)) {
        parsed_packet->questions = q->next;
        free(q->host);
        free(q->service);
        free(q->proto);
        free(q->domain);
        free(q);
        return;
    }

    while (q->next) {
        mdns_parsed_question_t *p = q->next;
        if (_mdns_question_matches(p, type, service)) {
            q->next = p->next;
            free(p->host);
            free(p->service);
            free(p->proto);
            free(p->domain);
            free(p);
            return;
        }
        q = q->next;
    }
}

/**
 * @brief  Get number of items in TXT parsed data
 */
static int _mdns_txt_items_count_get(const uint8_t *data, size_t len)
{
    if (len == 1) {
        return 0;
    }

    int num_items = 0;
    uint16_t i = 0;
    size_t partLen = 0;

    while (i < len) {
        partLen = data[i++];
        if (!partLen) {
            break;
        }
        if ((i + partLen) > len) {
            return -1;//error
        }
        i += partLen;
        num_items++;
    }
    return num_items;
}

/**
 * @brief  Get the length of TXT item's key name
 */
static int _mdns_txt_item_name_get_len(const uint8_t *data, size_t len)
{
    if (*data == '=') {
        return -1;
    }
    for (size_t i = 0; i < len; i++) {
        if (data[i] == '=') {
            return i;
        }
    }
    return len;
}

/**
 * @brief  Create TXT result array from parsed TXT data
 */
static void _mdns_result_txt_create(const uint8_t *data, size_t len, mdns_txt_item_t **out_txt, uint8_t **out_value_len,
                                    size_t *out_count)
{
    *out_txt = NULL;
    *out_count = 0;
    uint16_t i = 0, y;
    size_t partLen = 0;
    int num_items = _mdns_txt_items_count_get(data, len);
    if (num_items < 0) {
        return;//error
    }

    if (!num_items) {
        return;
    }

    mdns_txt_item_t *txt = (mdns_txt_item_t *)malloc(sizeof(mdns_txt_item_t) * num_items);
    if (!txt) {
        HOOK_MALLOC_FAILED;
        return;
    }
    uint8_t *txt_value_len = (uint8_t *)malloc(num_items);
    if (!txt_value_len) {
        free(txt);
        HOOK_MALLOC_FAILED;
        return;
    }
    memset(txt, 0, sizeof(mdns_txt_item_t) * num_items);
    memset(txt_value_len, 0, num_items);
    size_t txt_num = 0;

    while (i < len) {
        partLen = data[i++];
        if (!partLen) {
            break;
        }

        if ((i + partLen) > len) {
            goto handle_error;//error
        }

        int name_len = _mdns_txt_item_name_get_len(data + i, partLen);
        if (name_len < 0) {//invalid item (no name)
            i += partLen;
            continue;
        }
        char *key = (char *)malloc(name_len + 1);
        if (!key) {
            HOOK_MALLOC_FAILED;
            goto handle_error;//error
        }

        mdns_txt_item_t *t = &txt[txt_num];
        uint8_t *value_len = &txt_value_len[txt_num];
        txt_num++;

        memcpy(key, data + i, name_len);
        key[name_len] = 0;
        i += name_len + 1;
        t->key = key;

        int new_value_len = partLen - name_len - 1;
        if (new_value_len > 0) {
            char *value = (char *)malloc(new_value_len + 1);
            if (!value) {
                HOOK_MALLOC_FAILED;
                goto handle_error;//error
            }
            memcpy(value, data + i, new_value_len);
            value[new_value_len] = 0;
            *value_len = new_value_len;
            i += new_value_len;
            t->value = value;
        }
    }

    *out_txt = txt;
    *out_count = txt_num;
    *out_value_len = txt_value_len;
    return;

handle_error :
    for (y = 0; y < txt_num; y++) {
        mdns_txt_item_t *t = &txt[y];
        free((char *)t->key);
        free((char *)t->value);
    }
    free(txt_value_len);
    free(txt);
}

/**
 * @brief  Duplicate string or return error
 */
static esp_err_t _mdns_strdup_check(char **out, char *in)
{
    if (in && in[0]) {
        *out = strdup(in);
        if (!*out) {
            return ESP_FAIL;
        }
        return ESP_OK;
    }
    *out = NULL;
    return ESP_OK;
}

/**
 * @brief  main packet parser
 *
 * @param  packet       the packet
 */
void mdns_parse_packet(mdns_rx_packet_t *packet)
{
    static mdns_name_t n;
    mdns_header_t header;
    const uint8_t *data = _mdns_get_packet_data(packet);
    size_t len = _mdns_get_packet_len(packet);
    const uint8_t *content = data + MDNS_HEAD_LEN;
    bool do_not_reply = false;
    mdns_search_once_t *search_result = NULL;

#ifdef MDNS_ENABLE_DEBUG
    _mdns_dbg_printf("\nRX[%u][%u]: ", packet->tcpip_if, (uint32_t)packet->ip_protocol);
    if (packet->src.type == ESP_IPADDR_TYPE_V4) {
        _mdns_dbg_printf("From: " IPSTR ":%u, To: " IPSTR ", ", IP2STR(&packet->src.u_addr.ip4), packet->src_port, IP2STR(&packet->dest.u_addr.ip4));
    } else {
        _mdns_dbg_printf("From: " IPV6STR ":%u, To: " IPV6STR ", ", IPV62STR(packet->src.u_addr.ip6), packet->src_port, IPV62STR(packet->dest.u_addr.ip6));
    }
    mdns_debug_packet(data, len);
#endif

#ifndef CONFIG_MDNS_SKIP_SUPPRESSING_OWN_QUERIES
    // Check if the packet wasn't sent by us
    if (packet->ip_protocol == MDNS_IP_PROTOCOL_V4) {
        esp_netif_ip_info_t if_ip_info;
        if (esp_netif_get_ip_info(_mdns_get_esp_netif(packet->tcpip_if), &if_ip_info) == ESP_OK &&
                memcmp(&if_ip_info.ip.addr, &packet->src.u_addr.ip4.addr, sizeof(esp_ip4_addr_t)) == 0) {
            return;
        }
#if CONFIG_LWIP_IPV6
    } else {
        struct esp_ip6_addr if_ip6;
        if (esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(packet->tcpip_if), &if_ip6) == ESP_OK &&
                memcmp(&if_ip6, &packet->src.u_addr.ip6, sizeof(esp_ip6_addr_t)) == 0) {
            return;
        }
#endif
    }
#endif

    // Check for the minimum size of mdns packet
    if (len <=  MDNS_HEAD_ADDITIONAL_OFFSET) {
        return;
    }

    mdns_parsed_packet_t *parsed_packet = (mdns_parsed_packet_t *)malloc(sizeof(mdns_parsed_packet_t));
    if (!parsed_packet) {
        HOOK_MALLOC_FAILED;
        return;
    }
    memset(parsed_packet, 0, sizeof(mdns_parsed_packet_t));

    mdns_name_t *name = &n;
    memset(name, 0, sizeof(mdns_name_t));

    header.id = _mdns_read_u16(data, MDNS_HEAD_ID_OFFSET);
    header.flags = _mdns_read_u16(data, MDNS_HEAD_FLAGS_OFFSET);
    header.questions = _mdns_read_u16(data, MDNS_HEAD_QUESTIONS_OFFSET);
    header.answers = _mdns_read_u16(data, MDNS_HEAD_ANSWERS_OFFSET);
    header.servers = _mdns_read_u16(data, MDNS_HEAD_SERVERS_OFFSET);
    header.additional = _mdns_read_u16(data, MDNS_HEAD_ADDITIONAL_OFFSET);

    if (header.flags == MDNS_FLAGS_QR_AUTHORITATIVE && packet->src_port != MDNS_SERVICE_PORT) {
        free(parsed_packet);
        return;
    }

    //if we have not set the hostname, we can not answer questions
    if (header.questions && !header.answers && _str_null_or_empty(_mdns_server->hostname)) {
        free(parsed_packet);
        return;
    }

    parsed_packet->tcpip_if = packet->tcpip_if;
    parsed_packet->ip_protocol = packet->ip_protocol;
    parsed_packet->multicast = packet->multicast;
    parsed_packet->authoritative = (header.flags == MDNS_FLAGS_QR_AUTHORITATIVE);
    parsed_packet->distributed = header.flags == MDNS_FLAGS_DISTRIBUTED;
    parsed_packet->id = header.id;
    esp_netif_ip_addr_copy(&parsed_packet->src, &packet->src);
    parsed_packet->src_port = packet->src_port;

    if (header.questions) {
        uint8_t qs = header.questions;

        while (qs--) {
            content = _mdns_parse_fqdn(data, content, name, len);
            if (!content) {
                header.answers = 0;
                header.additional = 0;
                header.servers = 0;
                goto clear_rx_packet;//error
            }

            if (content + MDNS_CLASS_OFFSET + 1 >= data + len) {
                goto clear_rx_packet; // malformed packet, won't read behind it
            }
            uint16_t type = _mdns_read_u16(content, MDNS_TYPE_OFFSET);
            uint16_t mdns_class = _mdns_read_u16(content, MDNS_CLASS_OFFSET);
            bool unicast = !!(mdns_class & 0x8000);
            mdns_class &= 0x7FFF;
            content = content + 4;

            if (mdns_class != 0x0001 || name->invalid) {//bad class or invalid name for this question entry
                continue;
            }

            if (_mdns_name_is_discovery(name, type)) {
                //service discovery
                parsed_packet->discovery = true;
                mdns_srv_item_t *a = _mdns_server->services;
                while (a) {
                    mdns_parsed_question_t *question = (mdns_parsed_question_t *)calloc(1, sizeof(mdns_parsed_question_t));
                    if (!question) {
                        HOOK_MALLOC_FAILED;
                        goto clear_rx_packet;
                    }
                    question->next = parsed_packet->questions;
                    parsed_packet->questions = question;

                    question->unicast = unicast;
                    question->type = MDNS_TYPE_SDPTR;
                    question->host = NULL;
                    question->service = strdup(a->service->service);
                    question->proto = strdup(a->service->proto);
                    question->domain = strdup(MDNS_DEFAULT_DOMAIN);
                    if (!question->service || !question->proto || !question->domain) {
                        goto clear_rx_packet;
                    }
                    a = a->next;
                }
                continue;
            }
            if (!_mdns_name_is_ours(name)) {
                continue;
            }

            if (type == MDNS_TYPE_ANY && !_str_null_or_empty(name->host)) {
                parsed_packet->probe = true;
            }

            mdns_parsed_question_t *question = (mdns_parsed_question_t *)calloc(1, sizeof(mdns_parsed_question_t));
            if (!question) {
                HOOK_MALLOC_FAILED;
                goto clear_rx_packet;
            }
            question->next = parsed_packet->questions;
            parsed_packet->questions = question;

            question->unicast = unicast;
            question->type = type;
            question->sub = name->sub;
            if (_mdns_strdup_check(&(question->host), name->host)
                    || _mdns_strdup_check(&(question->service), name->service)
                    || _mdns_strdup_check(&(question->proto), name->proto)
                    || _mdns_strdup_check(&(question->domain), name->domain)) {
                goto clear_rx_packet;
            }
        }
    }

    if (header.questions && !parsed_packet->questions && !parsed_packet->discovery && !header.answers) {
        goto clear_rx_packet;
    } else if (header.answers || header.servers || header.additional) {
        uint16_t recordIndex = 0;

        while (content < (data + len)) {

            content = _mdns_parse_fqdn(data, content, name, len);
            if (!content) {
                goto clear_rx_packet;//error
            }

            if (content + MDNS_LEN_OFFSET + 1 >= data + len) {
                goto clear_rx_packet; // malformed packet, won't read behind it
            }
            uint16_t type = _mdns_read_u16(content, MDNS_TYPE_OFFSET);
            uint16_t mdns_class = _mdns_read_u16(content, MDNS_CLASS_OFFSET);
            uint32_t ttl = _mdns_read_u32(content, MDNS_TTL_OFFSET);
            uint16_t data_len = _mdns_read_u16(content, MDNS_LEN_OFFSET);
            const uint8_t *data_ptr = content + MDNS_DATA_OFFSET;
            mdns_class &= 0x7FFF;

            content = data_ptr + data_len;
            if (content > (data + len)) {
                goto clear_rx_packet;
            }

            bool discovery = false;
            bool ours = false;
            mdns_srv_item_t *service = NULL;
            mdns_parsed_record_type_t record_type = MDNS_ANSWER;

            if (recordIndex >= (header.answers + header.servers)) {
                record_type = MDNS_EXTRA;
            } else if (recordIndex >= (header.answers)) {
                record_type = MDNS_NS;
            }
            recordIndex++;

            if (type == MDNS_TYPE_NSEC || type == MDNS_TYPE_OPT) {
                //skip NSEC and OPT
                continue;
            }

            if (parsed_packet->discovery && _mdns_name_is_discovery(name, type)) {
                discovery = true;
            } else if (!name->sub && _mdns_name_is_ours(name)) {
                ours = true;
                if (name->service[0] && name->proto[0]) {
                    service = _mdns_get_service_item(name->service, name->proto, NULL);
                }
            } else {
                if ((header.flags & MDNS_FLAGS_QUERY_REPSONSE) == 0 || record_type == MDNS_NS) {
                    //skip this record
                    continue;
                }
                search_result = _mdns_search_find_from(_mdns_server->search_once, name, type, packet->tcpip_if, packet->ip_protocol);
            }

            if (type == MDNS_TYPE_PTR) {
                if (!_mdns_parse_fqdn(data, data_ptr, name, len)) {
                    continue;//error
                }
                if (search_result) {
                    _mdns_search_result_add_ptr(search_result, name->host, name->service, name->proto,
                                                packet->tcpip_if, packet->ip_protocol, ttl);
                } else if ((discovery || ours) && !name->sub && _mdns_name_is_ours(name)) {
                    if (discovery && (service = _mdns_get_service_item(name->service, name->proto, NULL))) {
                        _mdns_remove_parsed_question(parsed_packet, MDNS_TYPE_SDPTR, service);
                    } else if (service && parsed_packet->questions && !parsed_packet->probe) {
                        _mdns_remove_parsed_question(parsed_packet, type, service);
                    } else if (service) {
                        //check if TTL is more than half of the full TTL value (4500)
                        if (ttl > (MDNS_ANSWER_PTR_TTL / 2)) {
                            _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, service);
                        }
                    }
                }
            } else if (type == MDNS_TYPE_SRV) {
                mdns_result_t *result = NULL;
                if (search_result && search_result->type == MDNS_TYPE_PTR) {
                    result = search_result->result;
                    while (result) {
                        if (_mdns_get_esp_netif(packet->tcpip_if) == result->esp_netif
                                && packet->ip_protocol == result->ip_protocol
                                && result->instance_name && !strcmp(name->host, result->instance_name)) {
                            break;
                        }
                        result = result->next;
                    }
                    if (!result) {
                        result = _mdns_search_result_add_ptr(search_result, name->host, name->service, name->proto,
                                                             packet->tcpip_if, packet->ip_protocol, ttl);
                        if (!result) {
                            continue;//error
                        }
                    }
                }
                bool is_selfhosted = _mdns_name_is_selfhosted(name);
                if (!_mdns_parse_fqdn(data, data_ptr + MDNS_SRV_FQDN_OFFSET, name, len)) {
                    continue;//error
                }
                if (data_ptr + MDNS_SRV_PORT_OFFSET + 1 >= data + len) {
                    goto clear_rx_packet; // malformed packet, won't read behind it
                }
                uint16_t priority = _mdns_read_u16(data_ptr, MDNS_SRV_PRIORITY_OFFSET);
                uint16_t weight = _mdns_read_u16(data_ptr, MDNS_SRV_WEIGHT_OFFSET);
                uint16_t port = _mdns_read_u16(data_ptr, MDNS_SRV_PORT_OFFSET);

                if (search_result) {
                    if (search_result->type == MDNS_TYPE_PTR) {
                        if (!result->hostname) { // assign host/port for this entry only if not previously set
                            result->port = port;
                            result->hostname = strdup(name->host);
                        }
                    } else {
                        _mdns_search_result_add_srv(search_result, name->host, port, packet->tcpip_if, packet->ip_protocol, ttl);
                    }
                } else if (ours) {
                    if (parsed_packet->questions && !parsed_packet->probe) {
                        _mdns_remove_parsed_question(parsed_packet, type, service);
                        continue;
                    } else if (parsed_packet->distributed) {
                        _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, service);
                        continue;
                    }
                    if (!is_selfhosted) {
                        continue;
                    }
                    //detect collision (-1=won, 0=none, 1=lost)
                    int col = 0;
                    if (mdns_class > 1) {
                        col = 1;
                    } else if (!mdns_class) {
                        col = -1;
                    } else if (service) { // only detect srv collision if service existed
                        col = _mdns_check_srv_collision(service->service, priority, weight, port, name->host, name->domain);
                    }
                    if (service && col && (parsed_packet->probe || parsed_packet->authoritative)) {
                        if (col > 0 || !port) {
                            do_not_reply = true;
                            if (_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                                _mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].failed_probes++;
                                if (!_str_null_or_empty(service->service->instance)) {
                                    char *new_instance = _mdns_mangle_name((char *)service->service->instance);
                                    if (new_instance) {
                                        free((char *)service->service->instance);
                                        service->service->instance = new_instance;
                                    }
                                    _mdns_probe_all_pcbs(&service, 1, false, false);
                                } else if (!_str_null_or_empty(_mdns_server->instance)) {
                                    char *new_instance = _mdns_mangle_name((char *)_mdns_server->instance);
                                    if (new_instance) {
                                        free((char *)_mdns_server->instance);
                                        _mdns_server->instance = new_instance;
                                    }
                                    _mdns_restart_all_pcbs_no_instance();
                                } else {
                                    char *new_host = _mdns_mangle_name((char *)_mdns_server->hostname);
                                    if (new_host) {
                                        _mdns_remap_self_service_hostname(_mdns_server->hostname, new_host);
                                        free((char *)_mdns_server->hostname);
                                        _mdns_server->hostname = new_host;
                                        _mdns_self_host.hostname = new_host;
                                    }
                                    _mdns_restart_all_pcbs();
                                }
                            } else if (service) {
                                _mdns_pcb_send_bye(packet->tcpip_if, packet->ip_protocol, &service, 1, false);
                                _mdns_init_pcb_probe(packet->tcpip_if, packet->ip_protocol, &service, 1, false);
                            }
                        }
                    } else if (ttl > 60 && !col && !parsed_packet->authoritative && !parsed_packet->probe && !parsed_packet->questions) {
                        _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, service);
                    }
                }
            } else if (type == MDNS_TYPE_TXT) {
                if (search_result) {
                    mdns_txt_item_t *txt = NULL;
                    uint8_t *txt_value_len = NULL;
                    size_t txt_count = 0;

                    mdns_result_t *result = NULL;
                    if (search_result->type == MDNS_TYPE_PTR) {
                        result = search_result->result;
                        while (result) {
                            if (_mdns_get_esp_netif(packet->tcpip_if) == result->esp_netif
                                    && packet->ip_protocol == result->ip_protocol
                                    && result->instance_name && !strcmp(name->host, result->instance_name)) {
                                break;
                            }
                            result = result->next;
                        }
                        if (!result) {
                            result = _mdns_search_result_add_ptr(search_result, name->host, name->service, name->proto,
                                                                 packet->tcpip_if, packet->ip_protocol, ttl);
                            if (!result) {
                                continue;//error
                            }
                        }
                        if (!result->txt) {
                            _mdns_result_txt_create(data_ptr, data_len, &txt, &txt_value_len, &txt_count);
                            if (txt_count) {
                                result->txt = txt;
                                result->txt_count = txt_count;
                                result->txt_value_len = txt_value_len;
                            }
                        }
                    } else {
                        _mdns_result_txt_create(data_ptr, data_len, &txt, &txt_value_len, &txt_count);
                        if (txt_count) {
                            _mdns_search_result_add_txt(search_result, txt, txt_value_len, txt_count, packet->tcpip_if, packet->ip_protocol, ttl);
                        }
                    }
                } else if (ours) {
                    if (parsed_packet->questions && !parsed_packet->probe && service) {
                        _mdns_remove_parsed_question(parsed_packet, type, service);
                        continue;
                    }
                    if (!_mdns_name_is_selfhosted(name)) {
                        continue;
                    }
                    //detect collision (-1=won, 0=none, 1=lost)
                    int col = 0;
                    if (mdns_class > 1) {
                        col = 1;
                    } else if (!mdns_class) {
                        col = -1;
                    } else if (service) { // only detect txt collision if service existed
                        col = _mdns_check_txt_collision(service->service, data_ptr, data_len);
                    }
                    if (col && !_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running && service) {
                        do_not_reply = true;
                        _mdns_init_pcb_probe(packet->tcpip_if, packet->ip_protocol, &service, 1, true);
                    } else if (ttl > (MDNS_ANSWER_TXT_TTL / 2) && !col && !parsed_packet->authoritative && !parsed_packet->probe && !parsed_packet->questions && !_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                        _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, service);
                    }
                }

            }
#if CONFIG_LWIP_IPV6
            else if (type == MDNS_TYPE_AAAA) {//ipv6
                esp_ip_addr_t ip6;
                ip6.type = ESP_IPADDR_TYPE_V6;
                memcpy(ip6.u_addr.ip6.addr, data_ptr, MDNS_ANSWER_AAAA_SIZE);
                if (search_result) {
                    //check for more applicable searches (PTR & A/AAAA at the same time)
                    while (search_result) {
                        _mdns_search_result_add_ip(search_result, name->host, &ip6, packet->tcpip_if, packet->ip_protocol, ttl);
                        search_result = _mdns_search_find_from(search_result->next, name, type, packet->tcpip_if, packet->ip_protocol);
                    }
                } else if (ours) {
                    if (parsed_packet->questions && !parsed_packet->probe) {
                        _mdns_remove_parsed_question(parsed_packet, type, NULL);
                        continue;
                    }
                    if (!_mdns_name_is_selfhosted(name)) {
                        continue;
                    }
                    //detect collision (-1=won, 0=none, 1=lost)
                    int col = 0;
                    if (mdns_class > 1) {
                        col = 1;
                    } else if (!mdns_class) {
                        col = -1;
                    } else {
                        col = _mdns_check_aaaa_collision(&(ip6.u_addr.ip6), packet->tcpip_if);
                    }
                    if (col == 2) {
                        goto clear_rx_packet;
                    } else if (col == 1) {
                        do_not_reply = true;
                        if (_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                            if (col && (parsed_packet->probe || parsed_packet->authoritative)) {
                                _mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].failed_probes++;
                                char *new_host = _mdns_mangle_name((char *)_mdns_server->hostname);
                                if (new_host) {
                                    _mdns_remap_self_service_hostname(_mdns_server->hostname, new_host);
                                    free((char *)_mdns_server->hostname);
                                    _mdns_server->hostname = new_host;
                                    _mdns_self_host.hostname = new_host;
                                }
                                _mdns_restart_all_pcbs();
                            }
                        } else {
                            _mdns_init_pcb_probe(packet->tcpip_if, packet->ip_protocol, NULL, 0, true);
                        }
                    } else if (ttl > 60 && !col && !parsed_packet->authoritative && !parsed_packet->probe && !parsed_packet->questions && !_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                        _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, NULL);
                    }
                }

            }
#endif
            else if (type == MDNS_TYPE_A) {
                esp_ip_addr_t ip;
                ip.type = ESP_IPADDR_TYPE_V4;
                memcpy(&(ip.u_addr.ip4.addr), data_ptr, 4);
                if (search_result) {
                    //check for more applicable searches (PTR & A/AAAA at the same time)
                    while (search_result) {
                        _mdns_search_result_add_ip(search_result, name->host, &ip, packet->tcpip_if, packet->ip_protocol, ttl);
                        search_result = _mdns_search_find_from(search_result->next, name, type, packet->tcpip_if, packet->ip_protocol);
                    }
                } else if (ours) {
                    if (parsed_packet->questions && !parsed_packet->probe) {
                        _mdns_remove_parsed_question(parsed_packet, type, NULL);
                        continue;
                    }
                    if (!_mdns_name_is_selfhosted(name)) {
                        continue;
                    }
                    //detect collision (-1=won, 0=none, 1=lost)
                    int col = 0;
                    if (mdns_class > 1) {
                        col = 1;
                    } else if (!mdns_class) {
                        col = -1;
                    } else {
                        col = _mdns_check_a_collision(&(ip.u_addr.ip4), packet->tcpip_if);
                    }
                    if (col == 2) {
                        goto clear_rx_packet;
                    } else if (col == 1) {
                        do_not_reply = true;
                        if (_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                            if (col && (parsed_packet->probe || parsed_packet->authoritative)) {
                                _mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].failed_probes++;
                                char *new_host = _mdns_mangle_name((char *)_mdns_server->hostname);
                                if (new_host) {
                                    _mdns_remap_self_service_hostname(_mdns_server->hostname, new_host);
                                    free((char *)_mdns_server->hostname);
                                    _mdns_server->hostname = new_host;
                                    _mdns_self_host.hostname = new_host;
                                }
                                _mdns_restart_all_pcbs();
                            }
                        } else {
                            _mdns_init_pcb_probe(packet->tcpip_if, packet->ip_protocol, NULL, 0, true);
                        }
                    } else if (ttl > 60 && !col && !parsed_packet->authoritative && !parsed_packet->probe && !parsed_packet->questions && !_mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].probe_running) {
                        _mdns_remove_scheduled_answer(packet->tcpip_if, packet->ip_protocol, type, NULL);
                    }
                }

            }
        }
        //end while
        if (parsed_packet->authoritative) {
            _mdns_search_finish_done();
        }
    }

    if (!do_not_reply && _mdns_server->interfaces[packet->tcpip_if].pcbs[packet->ip_protocol].state > PCB_PROBE_3 && (parsed_packet->questions || parsed_packet->discovery)) {
        _mdns_create_answer_from_parsed_packet(parsed_packet);
    }


clear_rx_packet:
    while (parsed_packet->questions) {
        mdns_parsed_question_t *question = parsed_packet->questions;
        parsed_packet->questions = parsed_packet->questions->next;
        if (question->host) {
            free(question->host);
        }
        if (question->service) {
            free(question->service);
        }
        if (question->proto) {
            free(question->proto);
        }
        if (question->domain) {
            free(question->domain);
        }
        free(question);
    }
    free(parsed_packet);
}

/**
 * @brief  Enable mDNS interface
 */
void _mdns_enable_pcb(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    if (!mdns_is_netif_ready(tcpip_if, ip_protocol)) {
        if (_mdns_pcb_init(tcpip_if, ip_protocol)) {
            _mdns_server->interfaces[tcpip_if].pcbs[ip_protocol].failed_probes = 0;
            return;
        }
    }
    _mdns_restart_pcb(tcpip_if, ip_protocol);
}

/**
 * @brief  Disable mDNS interface
 */
void _mdns_disable_pcb(mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    _mdns_clean_netif_ptr(tcpip_if);

    if (mdns_is_netif_ready(tcpip_if, ip_protocol)) {
        _mdns_clear_pcb_tx_queue_head(tcpip_if, ip_protocol);
        mdns_pcb_deinit_local(tcpip_if, ip_protocol);
        mdns_if_t other_if = _mdns_get_other_if (tcpip_if);
        if (other_if != MDNS_MAX_INTERFACES && _mdns_server->interfaces[other_if].pcbs[ip_protocol].state == PCB_DUP) {
            _mdns_server->interfaces[other_if].pcbs[ip_protocol].state = PCB_OFF;
            _mdns_enable_pcb(other_if, ip_protocol);
        }
    }
    _mdns_server->interfaces[tcpip_if].pcbs[ip_protocol].state = PCB_OFF;
}

#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
static inline char nibble_to_hex(int var)
{
    return var > 9 ?  var - 10 + 'a' : var + '0';
}
#endif

/**
 * @brief  Performs interface changes based on system events or custom commands
 */
static void perform_event_action(mdns_if_t mdns_if, mdns_event_actions_t action)
{
    if (!_mdns_server || mdns_if >= MDNS_MAX_INTERFACES) {
        return;
    }
    if (action & MDNS_EVENT_ENABLE_IP4) {
        _mdns_enable_pcb(mdns_if, MDNS_IP_PROTOCOL_V4);
    }
    if (action & MDNS_EVENT_ENABLE_IP6) {
        _mdns_enable_pcb(mdns_if, MDNS_IP_PROTOCOL_V6);
    }
    if (action & MDNS_EVENT_DISABLE_IP4) {
        _mdns_disable_pcb(mdns_if, MDNS_IP_PROTOCOL_V4);
    }
    if (action & MDNS_EVENT_DISABLE_IP6) {
        _mdns_disable_pcb(mdns_if, MDNS_IP_PROTOCOL_V6);
    }
    if (action & MDNS_EVENT_ANNOUNCE_IP4) {
        _mdns_announce_pcb(mdns_if, MDNS_IP_PROTOCOL_V4, NULL, 0, true);
    }
    if (action & MDNS_EVENT_ANNOUNCE_IP6) {
        _mdns_announce_pcb(mdns_if, MDNS_IP_PROTOCOL_V6, NULL, 0, true);
    }

#ifdef CONFIG_MDNS_RESPOND_REVERSE_QUERIES
    if (action & MDNS_EVENT_IP4_REVERSE_LOOKUP) {
        esp_netif_ip_info_t if_ip_info;
        if (esp_netif_get_ip_info(_mdns_get_esp_netif(mdns_if), &if_ip_info) == ESP_OK) {
            esp_ip4_addr_t *ip = &if_ip_info.ip;
            char *reverse_query_name = NULL;
            if (asprintf(&reverse_query_name, "%d.%d.%d.%d.in-addr",
                         esp_ip4_addr4_16(ip), esp_ip4_addr3_16(ip),
                         esp_ip4_addr2_16(ip), esp_ip4_addr1_16(ip)) > 0 && reverse_query_name) {
                ESP_LOGD(TAG, "Registered reverse query: %s.arpa", reverse_query_name);
                _mdns_delegate_hostname_add(reverse_query_name, NULL);
            }
        }
    }

#ifdef CONFIG_LWIP_IPV6
    if (action & MDNS_EVENT_IP6_REVERSE_LOOKUP) {
        esp_ip6_addr_t addr6;
        if (!esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(mdns_if), &addr6) && !_ipv6_address_is_zero(addr6)) {
            uint8_t *paddr = (uint8_t *)&addr6.addr;
            const char sub[] = "ip6";
            const size_t query_name_size = 4 * sizeof(addr6.addr) /* (2 nibbles + 2 dots)/per byte of IP address */ + sizeof(sub);
            char *reverse_query_name = malloc(query_name_size);
            if (reverse_query_name) {
                char *ptr = &reverse_query_name[query_name_size];   // point to the end
                memcpy(ptr - sizeof(sub), sub, sizeof(sub));        // copy the IP sub-domain
                ptr -= sizeof(sub) + 1;                             // move before the sub-domain
                while (reverse_query_name < ptr) {                  // continue populating reverse query from the end
                    *ptr-- = '.';                                   // nibble by nibble, until we reach the beginning
                    *ptr-- = nibble_to_hex(((*paddr) >> 4) & 0x0F);
                    *ptr-- = '.';
                    *ptr-- = nibble_to_hex((*paddr) & 0x0F);
                    paddr++;
                }
                ESP_LOGD(TAG, "Registered reverse query: %s.arpa", reverse_query_name);
                _mdns_delegate_hostname_add(reverse_query_name, NULL);
            }
        }
    }
#endif /* CONFIG_LWIP_IPV6 */
#endif /* CONFIG_MDNS_RESPOND_REVERSE_QUERIES */
}

/**
 * @brief  Dispatch interface changes based on system events
 */
static inline void post_mdns_disable_pcb(mdns_predef_if_t preset_if, mdns_ip_protocol_t protocol)
{
    mdns_post_custom_action_tcpip_if(mdns_if_from_preset_if(preset_if), protocol == MDNS_IP_PROTOCOL_V4 ? MDNS_EVENT_DISABLE_IP4 : MDNS_EVENT_DISABLE_IP6);
}

static inline void post_mdns_enable_pcb(mdns_predef_if_t preset_if, mdns_ip_protocol_t protocol)
{
    mdns_post_custom_action_tcpip_if(mdns_if_from_preset_if(preset_if), protocol == MDNS_IP_PROTOCOL_V4 ? MDNS_EVENT_ENABLE_IP4 : MDNS_EVENT_ENABLE_IP6);
}

static inline void post_mdns_announce_pcb(mdns_predef_if_t preset_if, mdns_ip_protocol_t protocol)
{
    mdns_post_custom_action_tcpip_if(mdns_if_from_preset_if(preset_if), protocol == MDNS_IP_PROTOCOL_V4 ? MDNS_EVENT_ANNOUNCE_IP4 : MDNS_EVENT_ANNOUNCE_IP6);
}

#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH
void mdns_preset_if_handle_system_event(void *arg, esp_event_base_t event_base,
                                        int32_t event_id, void *event_data)
{
    if (!_mdns_server) {
        return;
    }

    esp_netif_dhcp_status_t dcst;
    if (event_base == WIFI_EVENT) {
        switch (event_id) {
        case WIFI_EVENT_STA_CONNECTED:
            if (!esp_netif_dhcpc_get_status(esp_netif_from_preset_if(MDNS_IF_STA), &dcst)) {
                if (dcst == ESP_NETIF_DHCP_STOPPED) {
                    post_mdns_enable_pcb(MDNS_IF_STA, MDNS_IP_PROTOCOL_V4);
                }
            }
            break;
        case WIFI_EVENT_STA_DISCONNECTED:
            post_mdns_disable_pcb(MDNS_IF_STA, MDNS_IP_PROTOCOL_V4);
            post_mdns_disable_pcb(MDNS_IF_STA, MDNS_IP_PROTOCOL_V6);
            break;
        case WIFI_EVENT_AP_START:
            post_mdns_enable_pcb(MDNS_IF_AP, MDNS_IP_PROTOCOL_V4);
            break;
        case WIFI_EVENT_AP_STOP:
            post_mdns_disable_pcb(MDNS_IF_AP, MDNS_IP_PROTOCOL_V4);
            post_mdns_disable_pcb(MDNS_IF_AP, MDNS_IP_PROTOCOL_V6);
            break;
        default:
            break;
        }
    }
#if CONFIG_ETH_ENABLED
    else if (event_base == ETH_EVENT) {
        switch (event_id) {
        case ETHERNET_EVENT_CONNECTED:
            if (!esp_netif_dhcpc_get_status(esp_netif_from_preset_if(MDNS_IF_ETH), &dcst)) {
                if (dcst == ESP_NETIF_DHCP_STOPPED) {
                    post_mdns_enable_pcb(MDNS_IF_ETH, MDNS_IP_PROTOCOL_V4);
                }
            }
            break;
        case ETHERNET_EVENT_DISCONNECTED:
            post_mdns_disable_pcb(MDNS_IF_ETH, MDNS_IP_PROTOCOL_V4);
            post_mdns_disable_pcb(MDNS_IF_ETH, MDNS_IP_PROTOCOL_V6);
            break;
        default:
            break;
        }
    }
#endif
    else if (event_base == IP_EVENT) {
        switch (event_id) {
        case IP_EVENT_STA_GOT_IP:
            post_mdns_enable_pcb(MDNS_IF_STA, MDNS_IP_PROTOCOL_V4);
            post_mdns_announce_pcb(MDNS_IF_STA, MDNS_IP_PROTOCOL_V6);
            break;
#if CONFIG_ETH_ENABLED
        case IP_EVENT_ETH_GOT_IP:
            post_mdns_enable_pcb(MDNS_IF_ETH, MDNS_IP_PROTOCOL_V4);
            break;
#endif
        case IP_EVENT_GOT_IP6: {
            ip_event_got_ip6_t *event = (ip_event_got_ip6_t *) event_data;
            mdns_if_t mdns_if = _mdns_get_if_from_esp_netif(event->esp_netif);
            if (mdns_if < MDNS_MAX_INTERFACES) {
                post_mdns_enable_pcb(mdns_if, MDNS_IP_PROTOCOL_V6);
                post_mdns_announce_pcb(mdns_if, MDNS_IP_PROTOCOL_V4);
            }

        }
        break;
        default:
            break;
        }
    }
}
#endif /* CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH */

/*
 * MDNS Search
 * */

/**
 * @brief  Free search structure (except the results)
 */
static void _mdns_search_free(mdns_search_once_t *search)
{
    free(search->instance);
    free(search->service);
    free(search->proto);
    vSemaphoreDelete(search->done_semaphore);
    free(search);
}

/**
 * @brief  Allocate new search structure
 */
static mdns_search_once_t *_mdns_search_init(const char *name, const char *service, const char *proto, uint16_t type, bool unicast,
        uint32_t timeout, uint8_t max_results, mdns_query_notify_t notifier)
{
    mdns_search_once_t *search = (mdns_search_once_t *)malloc(sizeof(mdns_search_once_t));
    if (!search) {
        HOOK_MALLOC_FAILED;
        return NULL;
    }
    memset(search, 0, sizeof(mdns_search_once_t));

    search->done_semaphore = xSemaphoreCreateBinary();
    if (!search->done_semaphore) {
        free(search);
        return NULL;
    }

    if (!_str_null_or_empty(name)) {
        search->instance = strndup(name, MDNS_NAME_BUF_LEN - 1);
        if (!search->instance) {
            _mdns_search_free(search);
            return NULL;
        }
    }

    if (!_str_null_or_empty(service)) {
        search->service = strndup(service, MDNS_NAME_BUF_LEN - 1);
        if (!search->service) {
            _mdns_search_free(search);
            return NULL;
        }
    }

    if (!_str_null_or_empty(proto)) {
        search->proto = strndup(proto, MDNS_NAME_BUF_LEN - 1);
        if (!search->proto) {
            _mdns_search_free(search);
            return NULL;
        }
    }

    search->type = type;
    search->unicast = unicast;
    search->timeout = timeout;
    search->num_results = 0;
    search->max_results = max_results;
    search->result = NULL;
    search->state = SEARCH_INIT;
    search->sent_at = 0;
    search->started_at = xTaskGetTickCount() * portTICK_PERIOD_MS;
    search->notifier = notifier;
    search->next = NULL;

    return search;
}

/**
 * @brief  Mark search as finished and remove it from search chain
 */
static void _mdns_search_finish(mdns_search_once_t *search)
{
    search->state = SEARCH_OFF;
    queueDetach(mdns_search_once_t, _mdns_server->search_once, search);
    if (search->notifier) {
        search->notifier(search);
    }
    xSemaphoreGive(search->done_semaphore);
}

/**
 * @brief  Add new search to the search chain
 */
static void _mdns_search_add(mdns_search_once_t *search)
{
    search->next = _mdns_server->search_once;
    _mdns_server->search_once = search;
}

/**
 * @brief  Called from parser to finish any searches that have reached maximum results
 */
static void _mdns_search_finish_done(void)
{
    mdns_search_once_t *search = _mdns_server->search_once;
    mdns_search_once_t *s = NULL;
    while (search) {
        s = search;
        search = search->next;
        if (s->max_results && s->num_results >= s->max_results) {
            _mdns_search_finish(s);
        }
    }
}

/**
 * @brief  Create linked IP (copy) from parsed one
 */
static mdns_ip_addr_t *_mdns_result_addr_create_ip(esp_ip_addr_t *ip)
{
    mdns_ip_addr_t *a = (mdns_ip_addr_t *)malloc(sizeof(mdns_ip_addr_t));
    if (!a) {
        HOOK_MALLOC_FAILED;
        return NULL;
    }
    memset(a, 0, sizeof(mdns_ip_addr_t));
    a->addr.type = ip->type;
    if (ip->type == ESP_IPADDR_TYPE_V6) {
        memcpy(a->addr.u_addr.ip6.addr, ip->u_addr.ip6.addr, 16);
    } else {
        a->addr.u_addr.ip4.addr = ip->u_addr.ip4.addr;
    }
    return a;
}

static inline void _mdns_result_update_ttl(mdns_result_t *r, uint32_t ttl)
{
    r->ttl = r->ttl < ttl ? r->ttl : ttl;
}

/**
 * @brief  Chain new IP to search result
 */
static void _mdns_result_add_ip(mdns_result_t *r, esp_ip_addr_t *ip)
{
    mdns_ip_addr_t *a = r->addr;
    while (a) {
        if (a->addr.type == ip->type) {
            if (a->addr.type == ESP_IPADDR_TYPE_V4 && a->addr.u_addr.ip4.addr == ip->u_addr.ip4.addr) {
                return;
            }
            if (a->addr.type == ESP_IPADDR_TYPE_V6 && !memcmp(a->addr.u_addr.ip6.addr, ip->u_addr.ip6.addr, 16)) {
                return;
            }
        }
        a = a->next;
    }
    a = _mdns_result_addr_create_ip(ip);
    if (!a) {
        return;
    }
    a->next = r->addr;
    r->addr = a;
}

/**
 * @brief  Called from parser to add A/AAAA data to search result
 */
static void _mdns_search_result_add_ip(mdns_search_once_t *search, const char *hostname, esp_ip_addr_t *ip,
                                       mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, uint32_t ttl)
{
    mdns_result_t *r = NULL;
    mdns_ip_addr_t *a = NULL;

    if ((search->type == MDNS_TYPE_A && ip->type == ESP_IPADDR_TYPE_V4)
            || (search->type == MDNS_TYPE_AAAA && ip->type == ESP_IPADDR_TYPE_V6)
            || search->type == MDNS_TYPE_ANY) {
        r = search->result;
        while (r) {
            if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol) {
                _mdns_result_add_ip(r, ip);
                _mdns_result_update_ttl(r, ttl);
                return;
            }
            r = r->next;
        }
        if (!search->max_results || search->num_results < search->max_results) {
            r = (mdns_result_t *)malloc(sizeof(mdns_result_t));
            if (!r) {
                HOOK_MALLOC_FAILED;
                return;
            }

            memset(r, 0, sizeof(mdns_result_t));

            a = _mdns_result_addr_create_ip(ip);
            if (!a) {
                free(r);
                return;
            }
            a->next = r->addr;
            r->hostname = strdup(hostname);
            r->addr = a;
            r->esp_netif = _mdns_get_esp_netif(tcpip_if);
            r->ip_protocol = ip_protocol;
            r->next = search->result;
            r->ttl = ttl;
            search->result = r;
            search->num_results++;
        }
    } else if (search->type == MDNS_TYPE_PTR || search->type == MDNS_TYPE_SRV) {
        r = search->result;
        while (r) {
            if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol && !_str_null_or_empty(r->hostname) && !strcasecmp(hostname, r->hostname)) {
                _mdns_result_add_ip(r, ip);
                _mdns_result_update_ttl(r, ttl);
                break;
            }
            r = r->next;
        }
    }
}

/**
 * @brief  Called from parser to add PTR data to search result
 */
static mdns_result_t *_mdns_search_result_add_ptr(mdns_search_once_t *search, const char *instance,
        const char *service_type, const char *proto, mdns_if_t tcpip_if,
        mdns_ip_protocol_t ip_protocol, uint32_t ttl)
{
    mdns_result_t *r = search->result;
    while (r) {
        if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol && !_str_null_or_empty(r->instance_name) && !strcasecmp(instance, r->instance_name)) {
            _mdns_result_update_ttl(r, ttl);
            return r;
        }
        r = r->next;
    }
    if (!search->max_results || search->num_results < search->max_results) {
        r = (mdns_result_t *)malloc(sizeof(mdns_result_t));
        if (!r) {
            HOOK_MALLOC_FAILED;
            return NULL;
        }

        memset(r, 0, sizeof(mdns_result_t));
        r->instance_name = strdup(instance);
        r->service_type = strdup(service_type);
        r->proto = strdup(proto);
        if (!r->instance_name) {
            free(r);
            return NULL;
        }

        r->esp_netif = _mdns_get_esp_netif(tcpip_if);
        r->ip_protocol = ip_protocol;
        r->ttl = ttl;
        r->next = search->result;
        search->result = r;
        search->num_results++;
        return r;
    }
    return NULL;
}

/**
 * @brief  Called from parser to add SRV data to search result
 */
static void _mdns_search_result_add_srv(mdns_search_once_t *search, const char *hostname, uint16_t port,
                                        mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol, uint32_t ttl)
{
    mdns_result_t *r = search->result;
    while (r) {
        if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol && !_str_null_or_empty(r->hostname) && !strcasecmp(hostname, r->hostname)) {
            _mdns_result_update_ttl(r, ttl);
            return;
        }
        r = r->next;
    }
    if (!search->max_results || search->num_results < search->max_results) {
        r = (mdns_result_t *)malloc(sizeof(mdns_result_t));
        if (!r) {
            HOOK_MALLOC_FAILED;
            return;
        }

        memset(r, 0, sizeof(mdns_result_t));
        r->hostname = strdup(hostname);
        if (!r->hostname) {
            free(r);
            return;
        }
        if (search->instance) {
            r->instance_name = strdup(search->instance);
        }
        r->service_type = strdup(search->service);
        r->proto = strdup(search->proto);
        r->port = port;
        r->esp_netif = _mdns_get_esp_netif(tcpip_if);
        r->ip_protocol = ip_protocol;
        r->ttl = ttl;
        r->next = search->result;
        search->result = r;
        search->num_results++;
    }
}

/**
 * @brief  Called from parser to add TXT data to search result
 */
static void _mdns_search_result_add_txt(mdns_search_once_t *search, mdns_txt_item_t *txt, uint8_t *txt_value_len,
                                        size_t txt_count, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol,
                                        uint32_t ttl)
{
    mdns_result_t *r = search->result;
    while (r) {
        if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol) {
            if (r->txt) {
                goto free_txt;
            }
            r->txt = txt;
            r->txt_value_len = txt_value_len;
            r->txt_count = txt_count;
            _mdns_result_update_ttl(r, ttl);
            return;
        }
        r = r->next;
    }
    if (!search->max_results || search->num_results < search->max_results) {
        r = (mdns_result_t *)malloc(sizeof(mdns_result_t));
        if (!r) {
            HOOK_MALLOC_FAILED;
            goto free_txt;
        }

        memset(r, 0, sizeof(mdns_result_t));
        r->txt = txt;
        r->txt_value_len = txt_value_len;
        r->txt_count = txt_count;
        r->esp_netif = _mdns_get_esp_netif(tcpip_if);
        r->ip_protocol = ip_protocol;
        r->ttl = ttl;
        r->next = search->result;
        search->result = r;
        search->num_results++;
    }
    return;

free_txt:
    for (size_t i = 0; i < txt_count; i++) {
        free((char *)(txt[i].key));
        free((char *)(txt[i].value));
    }
    free(txt);
}

/**
 * @brief  Called from packet parser to find matching running search
 */
static mdns_search_once_t *_mdns_search_find_from(mdns_search_once_t *s, mdns_name_t *name, uint16_t type, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_result_t *r = NULL;
    while (s) {
        if (s->state == SEARCH_OFF) {
            s = s->next;
            continue;
        }

        if (type == MDNS_TYPE_A || type == MDNS_TYPE_AAAA) {
            if ((s->type == MDNS_TYPE_ANY && s->service != NULL)
                    || (s->type != MDNS_TYPE_ANY && s->type != type && s->type != MDNS_TYPE_PTR && s->type != MDNS_TYPE_SRV)) {
                s = s->next;
                continue;
            }
            if (s->type != MDNS_TYPE_PTR && s->type != MDNS_TYPE_SRV) {
                if (!strcasecmp(name->host, s->instance)) {
                    return s;
                }
                s = s->next;
                continue;
            }
            r = s->result;
            while (r) {
                if (r->esp_netif == _mdns_get_esp_netif(tcpip_if) && r->ip_protocol == ip_protocol && !_str_null_or_empty(r->hostname) && !strcasecmp(name->host, r->hostname)) {
                    return s;
                }
                r = r->next;
            }
            s = s->next;
            continue;
        }

        if (type == MDNS_TYPE_SRV || type == MDNS_TYPE_TXT) {
            if ((s->type == MDNS_TYPE_ANY && s->service == NULL)
                    || (s->type != MDNS_TYPE_ANY && s->type != type && s->type != MDNS_TYPE_PTR)) {
                s = s->next;
                continue;
            }
            if (strcasecmp(name->service, s->service)
                    || strcasecmp(name->proto, s->proto)) {
                s = s->next;
                continue;
            }
            if (s->type != MDNS_TYPE_PTR) {
                if (s->instance && strcasecmp(name->host, s->instance) == 0) {
                    return s;
                }
                s = s->next;
                continue;
            }
            return s;
        }

        if (type == MDNS_TYPE_PTR && type == s->type && !strcasecmp(name->service, s->service) && !strcasecmp(name->proto, s->proto)) {
            return s;
        }

        s = s->next;
    }

    return NULL;
}

/**
 * @brief  Create search packet for particular interface
 */
static mdns_tx_packet_t *_mdns_create_search_packet(mdns_search_once_t *search, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_result_t *r = NULL;
    mdns_tx_packet_t *packet = _mdns_alloc_packet_default(tcpip_if, ip_protocol);
    if (!packet) {
        return NULL;
    }

    mdns_out_question_t *q = (mdns_out_question_t *)malloc(sizeof(mdns_out_question_t));
    if (!q) {
        HOOK_MALLOC_FAILED;
        _mdns_free_tx_packet(packet);
        return NULL;
    }
    q->next = NULL;
    q->unicast = search->unicast;
    q->type = search->type;
    q->host = search->instance;
    q->service = search->service;
    q->proto = search->proto;
    q->domain = MDNS_DEFAULT_DOMAIN;
    q->own_dynamic_memory = false;
    queueToEnd(mdns_out_question_t, packet->questions, q);

    if (search->type == MDNS_TYPE_PTR) {
        r = search->result;
        while (r) {
            //full record on the same interface is available
            if (r->esp_netif != _mdns_get_esp_netif(tcpip_if) || r->ip_protocol != ip_protocol || r->instance_name == NULL || r->hostname == NULL || r->addr == NULL) {
                r = r->next;
                continue;
            }
            mdns_out_answer_t *a = (mdns_out_answer_t *)malloc(sizeof(mdns_out_answer_t));
            if (!a) {
                HOOK_MALLOC_FAILED;
                _mdns_free_tx_packet(packet);
                return NULL;
            }
            a->type = MDNS_TYPE_PTR;
            a->service = NULL;
            a->custom_instance = r->instance_name;
            a->custom_service = search->service;
            a->custom_proto = search->proto;
            a->bye = false;
            a->flush = false;
            a->next = NULL;
            queueToEnd(mdns_out_answer_t, packet->answers, a);
            r = r->next;
        }
    }

    return packet;
}

/**
 * @brief  Send search packet to particular interface
 */
static void _mdns_search_send_pcb(mdns_search_once_t *search, mdns_if_t tcpip_if, mdns_ip_protocol_t ip_protocol)
{
    mdns_tx_packet_t *packet = NULL;
    if (mdns_is_netif_ready(tcpip_if, ip_protocol) && _mdns_server->interfaces[tcpip_if].pcbs[ip_protocol].state > PCB_INIT) {
        packet = _mdns_create_search_packet(search, tcpip_if, ip_protocol);
        if (!packet) {
            return;
        }
        _mdns_dispatch_tx_packet(packet);
        _mdns_free_tx_packet(packet);
    }
}

/**
 * @brief  Send search packet to all available interfaces
 */
static void _mdns_search_send(mdns_search_once_t *search)
{
    mdns_search_once_t *queue = _mdns_server->search_once;
    bool found = false;
    // looking for this search in active searches
    while (queue) {
        if (queue == search) {
            found = true;
            break;
        }
        queue = queue->next;
    }

    if (!found) {
        // no longer active -> skip sending this search
        return;
    }

    uint8_t i, j;
    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        for (j = 0; j < MDNS_IP_PROTOCOL_MAX; j++) {
            _mdns_search_send_pcb(search, (mdns_if_t)i, (mdns_ip_protocol_t)j);
        }
    }
}

static void _mdns_tx_handle_packet(mdns_tx_packet_t *p)
{
    mdns_tx_packet_t *a = NULL;
    mdns_out_question_t *q = NULL;
    mdns_pcb_t *pcb = &_mdns_server->interfaces[p->tcpip_if].pcbs[p->ip_protocol];
    uint32_t send_after = 1000;

    if (pcb->state == PCB_OFF) {
        _mdns_free_tx_packet(p);
        return;
    }
    _mdns_dispatch_tx_packet(p);

    switch (pcb->state) {
    case PCB_PROBE_1:
        q = p->questions;
        while (q) {
            q->unicast = false;
            q = q->next;
        }
    //fallthrough
    case PCB_PROBE_2:
        _mdns_schedule_tx_packet(p, 250);
        pcb->state = (mdns_pcb_state_t)((uint8_t)(pcb->state) + 1);
        break;
    case PCB_PROBE_3:
        a = _mdns_create_announce_from_probe(p);
        if (!a) {
            _mdns_schedule_tx_packet(p, 250);
            break;
        }
        pcb->probe_running = false;
        pcb->probe_ip = false;
        pcb->probe_services_len = 0;
        pcb->failed_probes = 0;
        free(pcb->probe_services);
        pcb->probe_services = NULL;
        _mdns_free_tx_packet(p);
        p = a;
        send_after = 250;
    //fallthrough
    case PCB_ANNOUNCE_1:
    //fallthrough
    case PCB_ANNOUNCE_2:
        _mdns_schedule_tx_packet(p, send_after);
        pcb->state = (mdns_pcb_state_t)((uint8_t)(pcb->state) + 1);
        break;
    case PCB_ANNOUNCE_3:
        pcb->state = PCB_RUNNING;
        _mdns_free_tx_packet(p);
        break;
    default:
        _mdns_free_tx_packet(p);
        break;
    }
}

static void _mdns_remap_self_service_hostname(const char *old_hostname, const char *new_hostname)
{
    mdns_srv_item_t *service = _mdns_server->services;

    while (service) {
        if (service->service->hostname &&
                strcmp(service->service->hostname, old_hostname) == 0) {
            free((char *)service->service->hostname);
            service->service->hostname = strdup(new_hostname);
        }
        service = service->next;
    }
}

/**
 * @brief  Free action data
 */
static void _mdns_free_action(mdns_action_t *action)
{
    switch (action->type) {
    case ACTION_HOSTNAME_SET:
        free(action->data.hostname_set.hostname);
        break;
    case ACTION_INSTANCE_SET:
        free(action->data.instance);
        break;
    case ACTION_SERVICE_ADD:
        _mdns_free_service(action->data.srv_add.service->service);
        free(action->data.srv_add.service);
        break;
    case ACTION_SERVICE_INSTANCE_SET:
        free(action->data.srv_instance.instance);
        break;
    case ACTION_SERVICE_TXT_REPLACE:
        _mdns_free_linked_txt(action->data.srv_txt_replace.txt);
        break;
    case ACTION_SERVICE_TXT_SET:
        free(action->data.srv_txt_set.key);
        free(action->data.srv_txt_set.value);
        break;
    case ACTION_SERVICE_TXT_DEL:
        free(action->data.srv_txt_del.key);
        break;
    case ACTION_SERVICE_SUBTYPE_ADD:
        free(action->data.srv_subtype_add.subtype);
        break;
    case ACTION_SEARCH_ADD:
    //fallthrough
    case ACTION_SEARCH_SEND:
    //fallthrough
    case ACTION_SEARCH_END:
        _mdns_search_free(action->data.search_add.search);
        break;
    case ACTION_TX_HANDLE:
        _mdns_free_tx_packet(action->data.tx_handle.packet);
        break;
    case ACTION_RX_HANDLE:
        _mdns_packet_free(action->data.rx_handle.packet);
        break;
    case ACTION_DELEGATE_HOSTNAME_SET_ADDR:
    case ACTION_DELEGATE_HOSTNAME_ADD:
        free((char *)action->data.delegate_hostname.hostname);
        free_address_list(action->data.delegate_hostname.address_list);
        break;
    case ACTION_DELEGATE_HOSTNAME_REMOVE:
        free((char *)action->data.delegate_hostname.hostname);
        break;
    default:
        break;
    }
    free(action);
}

/**
 * @brief  Called from service thread to execute given action
 */
static void _mdns_execute_action(mdns_action_t *action)
{
    mdns_srv_item_t *a = NULL;
    mdns_service_t *service;
    char *key;
    char *value;
    char *subtype;
    mdns_subtype_t *subtype_item;
    mdns_txt_linked_item_t *txt, * t;

    switch (action->type) {
    case ACTION_SYSTEM_EVENT:
        perform_event_action(action->data.sys_event.interface, action->data.sys_event.event_action);
        break;
    case ACTION_HOSTNAME_SET:
        _mdns_send_bye_all_pcbs_no_instance(true);
        _mdns_remap_self_service_hostname(_mdns_server->hostname, action->data.hostname_set.hostname);
        free((char *)_mdns_server->hostname);
        _mdns_server->hostname = action->data.hostname_set.hostname;
        _mdns_self_host.hostname = action->data.hostname_set.hostname;
        _mdns_restart_all_pcbs();
        xSemaphoreGive(_mdns_server->action_sema);
        break;
    case ACTION_INSTANCE_SET:
        _mdns_send_bye_all_pcbs_no_instance(false);
        free((char *)_mdns_server->instance);
        _mdns_server->instance = action->data.instance;
        _mdns_restart_all_pcbs_no_instance();

        break;
    case ACTION_SERVICE_ADD:
        action->data.srv_add.service->next = _mdns_server->services;
        _mdns_server->services = action->data.srv_add.service;
        _mdns_probe_all_pcbs(&action->data.srv_add.service, 1, false, false);
        break;
    case ACTION_SERVICE_INSTANCE_SET:
        if (action->data.srv_instance.service->service->instance) {
            _mdns_send_bye(&action->data.srv_instance.service, 1, false);
            free((char *)action->data.srv_instance.service->service->instance);
        }
        action->data.srv_instance.service->service->instance = action->data.srv_instance.instance;
        _mdns_probe_all_pcbs(&action->data.srv_instance.service, 1, false, false);

        break;
    case ACTION_SERVICE_PORT_SET:
        action->data.srv_port.service->service->port = action->data.srv_port.port;
        _mdns_announce_all_pcbs(&action->data.srv_port.service, 1, true);

        break;
    case ACTION_SERVICE_TXT_REPLACE:
        service = action->data.srv_txt_replace.service->service;
        txt = service->txt;
        service->txt = NULL;
        _mdns_free_linked_txt(txt);
        service->txt = action->data.srv_txt_replace.txt;
        _mdns_announce_all_pcbs(&action->data.srv_txt_replace.service, 1, false);

        break;
    case ACTION_SERVICE_TXT_SET:
        service = action->data.srv_txt_set.service->service;
        key = action->data.srv_txt_set.key;
        value = action->data.srv_txt_set.value;
        txt = service->txt;
        while (txt) {
            if (strcmp(txt->key, key) == 0) {
                free((char *)txt->value);
                free(key);
                txt->value = value;
                txt->value_len = action->data.srv_txt_set.value_len;
                break;
            }
            txt = txt->next;
        }
        if (!txt) {
            txt = (mdns_txt_linked_item_t *)malloc(sizeof(mdns_txt_linked_item_t));
            if (!txt) {
                HOOK_MALLOC_FAILED;
                _mdns_free_action(action);
                return;
            }
            txt->key = key;
            txt->value = value;
            txt->value_len = action->data.srv_txt_set.value_len;
            txt->next = service->txt;
            service->txt = txt;
        }

        _mdns_announce_all_pcbs(&action->data.srv_txt_set.service, 1, false);

        break;
    case ACTION_SERVICE_TXT_DEL:
        service = action->data.srv_txt_del.service->service;
        key = action->data.srv_txt_del.key;
        txt = service->txt;
        if (!txt) {
            break;
        }
        if (strcmp(txt->key, key) == 0) {
            service->txt = txt->next;
            free((char *)txt->key);
            free((char *)txt->value);
            free(txt);
        } else {
            while (txt->next) {
                if (strcmp(txt->next->key, key) == 0) {
                    t = txt->next;
                    txt->next = t->next;
                    free((char *)t->key);
                    free((char *)t->value);
                    free(t);
                    break;
                } else {
                    txt = txt->next;
                }
            }
        }
        free(key);

        _mdns_announce_all_pcbs(&action->data.srv_txt_set.service, 1, false);

        break;
    case ACTION_SERVICE_SUBTYPE_ADD:
        service = action->data.srv_subtype_add.service->service;
        subtype = action->data.srv_subtype_add.subtype;
        subtype_item = (mdns_subtype_t *)malloc(sizeof(mdns_subtype_t));
        if (!subtype_item) {
            HOOK_MALLOC_FAILED;
            _mdns_free_action(action);
            return;
        }
        subtype_item->subtype = subtype;
        subtype_item->next = service->subtype;
        service->subtype = subtype_item;
        break;
    case ACTION_SERVICE_DEL:
        a = _mdns_server->services;
        if (action->data.srv_del.service) {
            if (_mdns_server->services == action->data.srv_del.service) {
                _mdns_server->services = a->next;
                _mdns_send_bye(&a, 1, false);
                _mdns_remove_scheduled_service_packets(a->service);
                _mdns_free_service(a->service);
                free(a);
            } else {
                while (a->next && a->next != action->data.srv_del.service) {
                    a = a->next;
                }
                if (a->next == action->data.srv_del.service) {
                    mdns_srv_item_t *b = a->next;
                    a->next = a->next->next;
                    _mdns_send_bye(&b, 1, false);
                    _mdns_remove_scheduled_service_packets(b->service);
                    _mdns_free_service(b->service);
                    free(b);
                }
            }
        }

        break;
    case ACTION_SERVICES_CLEAR:
        _mdns_send_final_bye(false);
        a = _mdns_server->services;
        _mdns_server->services = NULL;
        while (a) {
            mdns_srv_item_t *s = a;
            a = a->next;
            _mdns_remove_scheduled_service_packets(s->service);
            _mdns_free_service(s->service);
            free(s);
        }

        break;
    case ACTION_SEARCH_ADD:
        _mdns_search_add(action->data.search_add.search);
        break;
    case ACTION_SEARCH_SEND:
        _mdns_search_send(action->data.search_add.search);
        break;
    case ACTION_SEARCH_END:
        _mdns_search_finish(action->data.search_add.search);
        break;
    case ACTION_TX_HANDLE: {
        mdns_tx_packet_t *p = _mdns_server->tx_queue_head;
        // packet to be handled should be at tx head, but must be consistent with the one pushed to action queue
        if (p && p == action->data.tx_handle.packet && p->queued) {
            p->queued = false; // clearing, as the packet might be reused (pushed and transmitted again)
            _mdns_server->tx_queue_head = p->next;
            _mdns_tx_handle_packet(p);
        } else {
            ESP_LOGD(TAG, "Skipping transmit of an unexpected packet!");
        }
    }
    break;
    case ACTION_RX_HANDLE:
        mdns_parse_packet(action->data.rx_handle.packet);
        _mdns_packet_free(action->data.rx_handle.packet);
        break;
    case ACTION_DELEGATE_HOSTNAME_ADD:
        if (!_mdns_delegate_hostname_add(action->data.delegate_hostname.hostname,
                                         action->data.delegate_hostname.address_list)) {
            free((char *)action->data.delegate_hostname.hostname);
            free_address_list(action->data.delegate_hostname.address_list);
        }
        break;
    case ACTION_DELEGATE_HOSTNAME_SET_ADDR:
        if (!_mdns_delegate_hostname_set_address(action->data.delegate_hostname.hostname,
                action->data.delegate_hostname.address_list)) {
            free_address_list(action->data.delegate_hostname.address_list);
        }
        free((char *)action->data.delegate_hostname.hostname);
        break;
    case ACTION_DELEGATE_HOSTNAME_REMOVE:
        _mdns_delegate_hostname_remove(action->data.delegate_hostname.hostname);
        free((char *)action->data.delegate_hostname.hostname);
        break;
    default:
        break;
    }
    free(action);
}

/**
 * @brief  Queue search action
 */
static esp_err_t _mdns_send_search_action(mdns_action_type_t type, mdns_search_once_t *search)
{
    mdns_action_t *action = NULL;

    action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }

    action->type = type;
    action->data.search_add.search = search;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

/**
 * @brief  Called from timer task to run mDNS responder
 *
 * periodically checks first unqueued packet (from tx head).
 * if it is scheduled to be transmitted, then pushes the packet to action queue to be handled.
 *
 */
static void _mdns_scheduler_run(void)
{
    MDNS_SERVICE_LOCK();
    mdns_tx_packet_t *p = _mdns_server->tx_queue_head;
    mdns_action_t *action = NULL;

    // find first unqueued packet
    while (p && p->queued) {
        p = p->next;
    }
    if (!p) {
        MDNS_SERVICE_UNLOCK();
        return;
    }
    if ((int32_t)(p->send_at - (xTaskGetTickCount() * portTICK_PERIOD_MS)) < 0) {
        action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
        if (action) {
            action->type = ACTION_TX_HANDLE;
            action->data.tx_handle.packet = p;
            p->queued = true;
            if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
                free(action);
                p->queued = false;
            }
        } else {
            HOOK_MALLOC_FAILED;
            // continue
        }
    }
    MDNS_SERVICE_UNLOCK();
}

/**
 * @brief  Called from timer task to run active searches
 */
static void _mdns_search_run(void)
{
    MDNS_SERVICE_LOCK();
    mdns_search_once_t *s = _mdns_server->search_once;
    uint32_t now = xTaskGetTickCount() * portTICK_PERIOD_MS;
    if (!s) {
        MDNS_SERVICE_UNLOCK();
        return;
    }
    while (s) {
        if (s->state != SEARCH_OFF) {
            if (now > (s->started_at + s->timeout)) {
                s->state = SEARCH_OFF;
                if (_mdns_send_search_action(ACTION_SEARCH_END, s) != ESP_OK) {
                    s->state = SEARCH_RUNNING;
                }
            } else if (s->state == SEARCH_INIT || (now - s->sent_at) > 1000) {
                s->state = SEARCH_RUNNING;
                s->sent_at = now;
                if (_mdns_send_search_action(ACTION_SEARCH_SEND, s) != ESP_OK) {
                    s->sent_at -= 1000;
                }
            }
        }
        s = s->next;
    }
    MDNS_SERVICE_UNLOCK();
}

/**
 * @brief  the main MDNS service task. Packets are received and parsed here
 */
static void _mdns_service_task(void *pvParameters)
{
    mdns_action_t *a = NULL;
    for (;;) {
        if (_mdns_server && _mdns_server->action_queue) {
            if (xQueueReceive(_mdns_server->action_queue, &a, portMAX_DELAY) == pdTRUE) {
                if (a && a->type == ACTION_TASK_STOP) {
                    break;
                }
                MDNS_SERVICE_LOCK();
                _mdns_execute_action(a);
                MDNS_SERVICE_UNLOCK();
            }
        } else {
            vTaskDelay(500 * portTICK_PERIOD_MS);
        }
    }
    _mdns_service_task_handle = NULL;
    vTaskDelete(NULL);
}

static void _mdns_timer_cb(void *arg)
{
    _mdns_scheduler_run();
    _mdns_search_run();
}

static esp_err_t _mdns_start_timer(void)
{
    esp_timer_create_args_t timer_conf = {
        .callback = _mdns_timer_cb,
        .arg = NULL,
        .dispatch_method = ESP_TIMER_TASK,
        .name = "mdns_timer"
    };
    esp_err_t err = esp_timer_create(&timer_conf, &(_mdns_server->timer_handle));
    if (err) {
        return err;
    }
    return esp_timer_start_periodic(_mdns_server->timer_handle, MDNS_TIMER_PERIOD_US);
}

static esp_err_t _mdns_stop_timer(void)
{
    esp_err_t err = ESP_OK;
    if (_mdns_server->timer_handle) {
        err = esp_timer_stop(_mdns_server->timer_handle);
        if (err) {
            return err;
        }
        err = esp_timer_delete(_mdns_server->timer_handle);
    }
    return err;
}

/**
 * @brief  Start the service thread if not running
 *
 * @return
 *      - ESP_OK on success
 *      - ESP_FAIL on error
 */
static esp_err_t _mdns_service_task_start(void)
{
    if (!_mdns_service_semaphore) {
        _mdns_service_semaphore = xSemaphoreCreateMutex();
        if (!_mdns_service_semaphore) {
            return ESP_FAIL;
        }
    }
    MDNS_SERVICE_LOCK();
    if (_mdns_start_timer()) {
        MDNS_SERVICE_UNLOCK();
        return ESP_FAIL;
    }
    if (!_mdns_service_task_handle) {
        xTaskCreatePinnedToCore(_mdns_service_task, "mdns", MDNS_SERVICE_STACK_DEPTH, NULL, MDNS_TASK_PRIORITY,
                                (TaskHandle_t *const)(&_mdns_service_task_handle), MDNS_TASK_AFFINITY);
        if (!_mdns_service_task_handle) {
            _mdns_stop_timer();
            MDNS_SERVICE_UNLOCK();
            vSemaphoreDelete(_mdns_service_semaphore);
            _mdns_service_semaphore = NULL;
            return ESP_FAIL;
        }
    }
    MDNS_SERVICE_UNLOCK();
    return ESP_OK;
}

/**
 * @brief  Stop the service thread
 *
 * @return
 *      - ESP_OK
 */
static esp_err_t _mdns_service_task_stop(void)
{
    _mdns_stop_timer();
    if (_mdns_service_task_handle) {
        mdns_action_t action;
        mdns_action_t *a = &action;
        action.type = ACTION_TASK_STOP;
        if (xQueueSend(_mdns_server->action_queue, &a, (TickType_t)0) != pdPASS) {
            vTaskDelete(_mdns_service_task_handle);
            _mdns_service_task_handle = NULL;
        }
        while (_mdns_service_task_handle) {
            vTaskDelay(10 / portTICK_PERIOD_MS);
        }
    }
    vSemaphoreDelete(_mdns_service_semaphore);
    _mdns_service_semaphore = NULL;
    return ESP_OK;
}

static esp_err_t mdns_post_custom_action_tcpip_if(mdns_if_t mdns_if, mdns_event_actions_t event_action)
{
    if (!_mdns_server || mdns_if >= MDNS_MAX_INTERFACES) {
        return ESP_ERR_INVALID_STATE;
    }

    mdns_action_t *action = (mdns_action_t *)calloc(1, sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SYSTEM_EVENT;
    action->data.sys_event.event_action = event_action;
    action->data.sys_event.interface = mdns_if;

    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
    }
    return ESP_OK;
}

static inline void set_default_duplicated_interfaces(void)
{
    mdns_if_t wifi_sta_if = MDNS_MAX_INTERFACES;
    mdns_if_t eth_if = MDNS_MAX_INTERFACES;
    for (mdns_if_t i = 0; i < MDNS_MAX_INTERFACES; i++) {
        if (s_esp_netifs[i].predefined && s_esp_netifs[i].predef_if == MDNS_IF_STA) {
            wifi_sta_if = i;
        }
        if (s_esp_netifs[i].predefined && s_esp_netifs[i].predef_if == MDNS_IF_ETH) {
            eth_if = i;
        }
    }
    if (wifi_sta_if != MDNS_MAX_INTERFACES && eth_if != MDNS_MAX_INTERFACES) {
        s_esp_netifs[wifi_sta_if].duplicate = eth_if;
        s_esp_netifs[eth_if].duplicate = wifi_sta_if;
    }
}

static inline void unregister_predefined_handlers(void)
{
#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP
    esp_event_handler_unregister(WIFI_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event);
#endif
#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH
    esp_event_handler_unregister(IP_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event);
#endif
#if defined(CONFIG_ETH_ENABLED) && CONFIG_MDNS_PREDEF_NETIF_ETH
    esp_event_handler_unregister(ETH_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event);
#endif
}

/*
 * Public Methods
 * */

esp_err_t mdns_netif_action(esp_netif_t *esp_netif, mdns_event_actions_t event_action)
{
    return mdns_post_custom_action_tcpip_if(_mdns_get_if_from_esp_netif(esp_netif), event_action);
}

esp_err_t mdns_register_netif(esp_netif_t *esp_netif)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }

    esp_err_t err = ESP_ERR_NO_MEM;
    MDNS_SERVICE_LOCK();
    for (mdns_if_t i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        if (s_esp_netifs[i].netif == esp_netif) {
            MDNS_SERVICE_UNLOCK();
            return ESP_ERR_INVALID_STATE;
        }
    }

    for (mdns_if_t i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        if (!s_esp_netifs[i].predefined && s_esp_netifs[i].netif == NULL) {
            s_esp_netifs[i].netif = esp_netif;
            err = ESP_OK;
            break;
        }
    }
    MDNS_SERVICE_UNLOCK();
    return err;
}

esp_err_t mdns_unregister_netif(esp_netif_t *esp_netif)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }

    esp_err_t err = ESP_ERR_NOT_FOUND;
    MDNS_SERVICE_LOCK();
    for (mdns_if_t i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        if (!s_esp_netifs[i].predefined && s_esp_netifs[i].netif == esp_netif) {
            s_esp_netifs[i].netif = NULL;
            err = ESP_OK;
            break;
        }
    }
    MDNS_SERVICE_UNLOCK();
    return err;
}


esp_err_t mdns_init(void)
{
    esp_err_t err = ESP_OK;

    if (_mdns_server) {
        return err;
    }

    _mdns_server = (mdns_server_t *)malloc(sizeof(mdns_server_t));
    if (!_mdns_server) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }
    memset((uint8_t *)_mdns_server, 0, sizeof(mdns_server_t));
    // zero-out local copy of netifs to initiate a fresh search by interface key whenever a netif ptr is needed
    for (mdns_if_t i = 0; i < MDNS_MAX_INTERFACES; ++i) {
        s_esp_netifs[i].netif = NULL;
    }

    _mdns_server->action_queue = xQueueCreate(MDNS_ACTION_QUEUE_LEN, sizeof(mdns_action_t *));
    if (!_mdns_server->action_queue) {
        err = ESP_ERR_NO_MEM;
        goto free_server;
    }

    _mdns_server->action_sema = xSemaphoreCreateBinary();
    if (!_mdns_server->action_sema) {
        err = ESP_ERR_NO_MEM;
        goto free_queue;
    }

#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP
    if ((err = esp_event_handler_register(WIFI_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event, NULL)) != ESP_OK) {
        goto free_event_handlers;
    }
#endif
#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH
    if ((err = esp_event_handler_register(IP_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event, NULL)) != ESP_OK) {
        goto free_event_handlers;
    }
#endif
#if defined(CONFIG_ETH_ENABLED) && CONFIG_MDNS_PREDEF_NETIF_ETH
    if ((err = esp_event_handler_register(ETH_EVENT, ESP_EVENT_ANY_ID, mdns_preset_if_handle_system_event, NULL)) != ESP_OK) {
        goto free_event_handlers;
    }
#endif

#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH
    set_default_duplicated_interfaces();
#endif

    uint8_t i;
#if CONFIG_LWIP_IPV6
    esp_ip6_addr_t tmp_addr6;
#endif
    esp_netif_ip_info_t if_ip_info;

    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
#if CONFIG_LWIP_IPV6
        if (!esp_netif_get_ip6_linklocal(_mdns_get_esp_netif(i), &tmp_addr6) && !_ipv6_address_is_zero(tmp_addr6)) {
            _mdns_enable_pcb(i, MDNS_IP_PROTOCOL_V6);
        }
#endif
        if (!esp_netif_get_ip_info(_mdns_get_esp_netif(i), &if_ip_info) && if_ip_info.ip.addr) {
            _mdns_enable_pcb(i, MDNS_IP_PROTOCOL_V4);
        }
    }

    if (_mdns_service_task_start()) {
        //service start failed!
        err = ESP_FAIL;
        goto free_all_and_disable_pcbs;
    }

    return ESP_OK;

free_all_and_disable_pcbs:
    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        _mdns_disable_pcb(i, MDNS_IP_PROTOCOL_V6);
        _mdns_disable_pcb(i, MDNS_IP_PROTOCOL_V4);
        s_esp_netifs[i].duplicate = MDNS_MAX_INTERFACES;
    }
#if CONFIG_MDNS_PREDEF_NETIF_STA || CONFIG_MDNS_PREDEF_NETIF_AP || CONFIG_MDNS_PREDEF_NETIF_ETH
free_event_handlers:
    unregister_predefined_handlers();
#endif
    vSemaphoreDelete(_mdns_server->action_sema);
free_queue:
    vQueueDelete(_mdns_server->action_queue);
free_server:
    free(_mdns_server);
    _mdns_server = NULL;
    return err;
}

void mdns_free(void)
{
    uint8_t i, j;
    if (!_mdns_server) {
        return;
    }

    // Unregister handlers before destroying the mdns internals to avoid receiving async events while deinit
    unregister_predefined_handlers();

    mdns_service_remove_all();
    free_delegated_hostnames();
    _mdns_service_task_stop();
    for (i = 0; i < MDNS_MAX_INTERFACES; i++) {
        for (j = 0; j < MDNS_IP_PROTOCOL_MAX; j++) {
            mdns_pcb_deinit_local(i, j);
        }
    }
    free((char *)_mdns_server->hostname);
    free((char *)_mdns_server->instance);
    if (_mdns_server->action_queue) {
        mdns_action_t *c;
        while (xQueueReceive(_mdns_server->action_queue, &c, 0) == pdTRUE) {
            _mdns_free_action(c);
        }
        vQueueDelete(_mdns_server->action_queue);
    }
    _mdns_clear_tx_queue_head();
    while (_mdns_server->search_once) {
        mdns_search_once_t *h = _mdns_server->search_once;
        _mdns_server->search_once = h->next;
        free(h->instance);
        free(h->service);
        free(h->proto);
        vSemaphoreDelete(h->done_semaphore);
        if (h->result) {
            mdns_query_results_free(h->result);
        }
        free(h);
    }
    vSemaphoreDelete(_mdns_server->action_sema);
    free(_mdns_server);
    _mdns_server = NULL;
}

esp_err_t mdns_hostname_set(const char *hostname)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_ARG;
    }
    if (_str_null_or_empty(hostname) || strlen(hostname) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    char *new_hostname = strndup(hostname, MDNS_NAME_BUF_LEN - 1);
    if (!new_hostname) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_hostname);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_HOSTNAME_SET;
    action->data.hostname_set.hostname = new_hostname;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_hostname);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    xSemaphoreTake(_mdns_server->action_sema, portMAX_DELAY);
    return ESP_OK;
}

esp_err_t mdns_hostname_get(char *hostname)
{
    if (!_mdns_server || !hostname) {
        return ESP_ERR_INVALID_ARG;
    }
    MDNS_SERVICE_LOCK();
    strncpy(hostname, _mdns_server->hostname, strnlen(_mdns_server->hostname, MDNS_NAME_BUF_LEN));
    MDNS_SERVICE_UNLOCK();
    return ESP_OK;
}

esp_err_t mdns_delegate_hostname_add(const char *hostname, const mdns_ip_addr_t *address_list)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (_str_null_or_empty(hostname) || strlen(hostname) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    char *new_hostname = strndup(hostname, MDNS_NAME_BUF_LEN - 1);
    if (!new_hostname) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_hostname);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_DELEGATE_HOSTNAME_ADD;
    action->data.delegate_hostname.hostname = new_hostname;
    action->data.delegate_hostname.address_list = copy_address_list(address_list);
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_hostname);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_delegate_hostname_remove(const char *hostname)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (_str_null_or_empty(hostname) || strlen(hostname) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    char *new_hostname = strndup(hostname, MDNS_NAME_BUF_LEN - 1);
    if (!new_hostname) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_hostname);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_DELEGATE_HOSTNAME_REMOVE;
    action->data.delegate_hostname.hostname = new_hostname;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_hostname);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_delegate_hostname_set_address(const char *hostname, const mdns_ip_addr_t *address_list)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (_str_null_or_empty(hostname) || strlen(hostname) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    char *new_hostname = strndup(hostname, MDNS_NAME_BUF_LEN - 1);
    if (!new_hostname) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_hostname);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_DELEGATE_HOSTNAME_SET_ADDR;
    action->data.delegate_hostname.hostname = new_hostname;
    action->data.delegate_hostname.address_list = copy_address_list(address_list);
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_hostname);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

bool mdns_hostname_exists(const char *hostname)
{
    return _hostname_is_ours(hostname);
}

esp_err_t mdns_instance_name_set(const char *instance)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (_str_null_or_empty(instance) || _mdns_server->hostname == NULL || strlen(instance) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    char *new_instance = strndup(instance, MDNS_NAME_BUF_LEN - 1);
    if (!new_instance) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_instance);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_INSTANCE_SET;
    action->data.instance = new_instance;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_instance);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

/*
 * MDNS SERVICES
 * */

esp_err_t mdns_service_add_for_host(const char *instance, const char *service, const char *proto, const char *hostname,
                                    uint16_t port, mdns_txt_item_t txt[], size_t num_items)
{
    if (!_mdns_server || _str_null_or_empty(service) || _str_null_or_empty(proto) || !port || !hostname) {
        return ESP_ERR_INVALID_ARG;
    }

    if (!_mdns_can_add_more_services()) {
        return ESP_ERR_NO_MEM;
    }

    mdns_srv_item_t *item = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (item) {
        return ESP_ERR_INVALID_ARG;
    }

    mdns_service_t *s = _mdns_create_service(service, proto, hostname, port, instance, num_items, txt);
    if (!s) {
        return ESP_ERR_NO_MEM;
    }

    item = (mdns_srv_item_t *)malloc(sizeof(mdns_srv_item_t));
    if (!item) {
        HOOK_MALLOC_FAILED;
        _mdns_free_service(s);
        return ESP_ERR_NO_MEM;
    }

    item->service = s;
    item->next = NULL;

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        _mdns_free_service(s);
        free(item);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICE_ADD;
    action->data.srv_add.service = item;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        _mdns_free_service(s);
        free(item);
        free(action);
        return ESP_ERR_NO_MEM;
    }

    size_t start = xTaskGetTickCount();
    size_t timeout_ticks = pdMS_TO_TICKS(MDNS_SERVICE_ADD_TIMEOUT_MS);
    while (_mdns_get_service_item_instance(instance, service, proto, hostname) == NULL) {
        uint32_t expired = xTaskGetTickCount() - start;
        if (expired >= timeout_ticks) {
            return ESP_FAIL; // Timeout
        }
        vTaskDelay(MIN(10 / portTICK_PERIOD_MS, timeout_ticks - expired));
    }

    return ESP_OK;
}

esp_err_t mdns_service_add(const char *instance, const char *service, const char *proto, uint16_t port,
                           mdns_txt_item_t txt[], size_t num_items)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_add_for_host(instance, service, proto, _mdns_server->hostname, port, txt, num_items);
}

bool mdns_service_exists(const char *service_type, const char *proto, const char *hostname)
{
    return _mdns_get_service_item(service_type, proto, hostname) != NULL;
}

bool mdns_service_exists_with_instance(const char *instance, const char *service_type, const char *proto,
                                       const char *hostname)
{
    return _mdns_get_service_item_instance(instance, service_type, proto, hostname) != NULL;
}

static mdns_txt_item_t *_copy_mdns_txt_items(mdns_txt_linked_item_t *items, uint8_t **txt_value_len, size_t *txt_count)
{
    mdns_txt_item_t *ret = NULL;
    size_t ret_index = 0;
    for (mdns_txt_linked_item_t *tmp = items; tmp != NULL; tmp = tmp->next) {
        ret_index++;
    }
    *txt_count = ret_index;
    ret = (mdns_txt_item_t *)calloc(ret_index, sizeof(mdns_txt_item_t));
    *txt_value_len = (uint8_t *)calloc(ret_index, sizeof(uint8_t));
    if (!ret || !(*txt_value_len)) {
        HOOK_MALLOC_FAILED;
        goto handle_error;
    }
    ret_index = 0;
    for (mdns_txt_linked_item_t *tmp = items; tmp != NULL; tmp = tmp->next) {
        size_t key_len = strlen(tmp->key);
        char *key = (char *)malloc(key_len + 1);
        if (!key) {
            HOOK_MALLOC_FAILED;
            goto handle_error;
        }
        memcpy(key, tmp->key, key_len);
        key[key_len] = 0;
        ret[ret_index].key = key;
        char *value = (char *)malloc(tmp->value_len + 1);
        if (!value) {
            HOOK_MALLOC_FAILED;
            goto handle_error;
        }
        memcpy(value, tmp->value, tmp->value_len);
        value[tmp->value_len] = 0;
        ret[ret_index].value = value;
        (*txt_value_len)[ret_index] = tmp->value_len;
        ret_index++;
    }
    return ret;

handle_error:
    for (size_t y = 0; y < ret_index + 1; y++) {
        mdns_txt_item_t *t = &ret[y];
        free((char *)t->key);
        free((char *)t->value);
    }
    free(*txt_value_len);
    free(ret);
    return NULL;
}

static mdns_ip_addr_t *_copy_delegated_host_address_list(char *hostname)
{
    mdns_host_item_t *host = _mdns_host_list;
    while (host) {
        if (strcasecmp(host->hostname, hostname) == 0) {
            return copy_address_list(host->address_list);
        }
    }
    return NULL;
}

static mdns_result_t *_mdns_lookup_service(const char *instance, const char *service, const char *proto, size_t max_results, bool selfhost)
{
    if (_str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return NULL;
    }
    mdns_result_t *results = NULL;
    size_t num_results = 0;
    mdns_srv_item_t *s = _mdns_server->services;
    while (s) {
        mdns_service_t *srv = s->service;
        if (!srv || !srv->hostname) {
            s = s->next;
            continue;
        }
        bool is_service_selfhosted = !_str_null_or_empty(_mdns_server->hostname) && !strcasecmp(_mdns_server->hostname, srv->hostname);
        bool is_service_delegated = _str_null_or_empty(_mdns_server->hostname) || strcasecmp(_mdns_server->hostname, srv->hostname);
        if ((selfhost && is_service_selfhosted) || (!selfhost && is_service_delegated)) {
            if (!strcasecmp(srv->service, service) && !strcasecmp(srv->proto, proto) &&
                    (_str_null_or_empty(instance) || _mdns_instance_name_match(srv->instance, instance))) {
                mdns_result_t *item = (mdns_result_t *)malloc(sizeof(mdns_result_t));
                if (!item) {
                    HOOK_MALLOC_FAILED;
                    goto handle_error;
                }
                item->next = results;
                results = item;
                item->esp_netif = NULL;
                item->ttl = _str_null_or_empty(instance) ? MDNS_ANSWER_PTR_TTL : MDNS_ANSWER_SRV_TTL;
                item->ip_protocol = MDNS_IP_PROTOCOL_MAX;
                item->instance_name = strndup(srv->instance, MDNS_NAME_BUF_LEN - 1);
                if (!item->instance_name) {
                    HOOK_MALLOC_FAILED;
                    goto handle_error;
                }
                item->service_type = strndup(srv->service, MDNS_NAME_BUF_LEN - 1);
                if (!item->service_type) {
                    HOOK_MALLOC_FAILED;
                    goto handle_error;
                }
                item->proto = strndup(srv->proto, MDNS_NAME_BUF_LEN - 1);
                if (!item->proto) {
                    HOOK_MALLOC_FAILED;
                    goto handle_error;
                }
                item->hostname = strndup(srv->hostname, MDNS_NAME_BUF_LEN - 1);
                if (!item->hostname) {
                    HOOK_MALLOC_FAILED;
                    goto handle_error;
                }
                item->port = srv->port;
                item->txt = _copy_mdns_txt_items(srv->txt, &(item->txt_value_len), &(item->txt_count));
                // We should not append addresses for selfhost lookup result as we don't know which interface's address to append.
                if (selfhost) {
                    item->addr = NULL;
                } else {
                    item->addr = _copy_delegated_host_address_list(item->hostname);
                    if (!item->addr) {
                        goto handle_error;
                    }
                }
                if (num_results < max_results) {
                    num_results++;
                }
                if (num_results >= max_results) {
                    break;
                }
            }
        }
        s = s->next;
    }
    return results;
handle_error:
    mdns_query_results_free(results);
    return NULL;
}

esp_err_t mdns_service_port_set_for_host(const char *instance, const char *service, const char *proto, const char *hostname, uint16_t port)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto) || !port) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICE_PORT_SET;
    action->data.srv_port.service = s;
    action->data.srv_port.port = port;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_port_set(const char *service, const char *proto, uint16_t port)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_port_set_for_host(NULL, service, proto, _mdns_server->hostname, port);
}

esp_err_t mdns_service_txt_set_for_host(const char *instance, const char *service, const char *proto, const char *hostname,
                                        mdns_txt_item_t txt[], uint8_t num_items)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto) || (num_items && txt == NULL)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }

    mdns_txt_linked_item_t *new_txt = NULL;
    if (num_items) {
        new_txt = _mdns_allocate_txt(num_items, txt);
        if (!new_txt) {
            return ESP_ERR_NO_MEM;
        }
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        _mdns_free_linked_txt(new_txt);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICE_TXT_REPLACE;
    action->data.srv_txt_replace.service = s;
    action->data.srv_txt_replace.txt = new_txt;

    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        _mdns_free_linked_txt(new_txt);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_txt_set(const char *service, const char *proto, mdns_txt_item_t txt[], uint8_t num_items)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_txt_set_for_host(NULL, service, proto, _mdns_server->hostname, txt, num_items);
}

esp_err_t mdns_service_txt_item_set_for_host_with_explicit_value_len(const char *instance, const char *service, const char *proto,
        const char *hostname, const char *key,
        const char *value, uint8_t value_len)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto) ||
            _str_null_or_empty(key) || (!value && value_len)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }
    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }

    action->type = ACTION_SERVICE_TXT_SET;
    action->data.srv_txt_set.service = s;
    action->data.srv_txt_set.key = strdup(key);
    if (!action->data.srv_txt_set.key) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    if (value_len > 0) {
        action->data.srv_txt_set.value = (char *)malloc(value_len);
        if (!action->data.srv_txt_set.value) {
            free(action->data.srv_txt_set.key);
            free(action);
            return ESP_ERR_NO_MEM;
        }
        memcpy(action->data.srv_txt_set.value, value, value_len);
        action->data.srv_txt_set.value_len = value_len;
    } else {
        action->data.srv_txt_set.value = NULL;
        action->data.srv_txt_set.value_len = 0;
    }
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action->data.srv_txt_set.key);
        free(action->data.srv_txt_set.value);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_txt_item_set_for_host(const char *instance, const char *service, const char *proto, const char *hostname,
        const char *key, const char *value)
{
    return mdns_service_txt_item_set_for_host_with_explicit_value_len(instance, service, proto, hostname, key, value,
            strlen(value));
}


esp_err_t mdns_service_txt_item_set(const char *service, const char *proto, const char *key, const char *value)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_txt_item_set_for_host_with_explicit_value_len(NULL, service, proto, _mdns_server->hostname, key,
            value, strlen(value));
}

esp_err_t mdns_service_txt_item_set_with_explicit_value_len(const char *service, const char *proto, const char *key,
        const char *value, uint8_t value_len)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_txt_item_set_for_host_with_explicit_value_len(NULL, service, proto, _mdns_server->hostname, key,
            value, value_len);
}

esp_err_t mdns_service_txt_item_remove_for_host(const char *instance, const char *service, const char *proto, const char *hostname,
        const char *key)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto) || _str_null_or_empty(key)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }
    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }

    action->type = ACTION_SERVICE_TXT_DEL;
    action->data.srv_txt_del.service = s;
    action->data.srv_txt_del.key = strdup(key);
    if (!action->data.srv_txt_del.key) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action->data.srv_txt_del.key);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_txt_item_remove(const char *service, const char *proto, const char *key)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_txt_item_remove_for_host(NULL, service, proto, _mdns_server->hostname, key);
}

esp_err_t mdns_service_subtype_add_for_host(const char *instance_name, const char *service, const char *proto,
        const char *hostname, const char *subtype)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto) ||
            _str_null_or_empty(subtype)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance_name, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }
    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }

    action->type = ACTION_SERVICE_SUBTYPE_ADD;
    action->data.srv_subtype_add.service = s;
    action->data.srv_subtype_add.subtype = strdup(subtype);

    if (!action->data.srv_subtype_add.subtype) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action->data.srv_subtype_add.subtype);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_instance_name_set_for_host(const char *instance_old, const char *service, const char *proto, const char *hostname,
        const char *instance)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }
    if (_str_null_or_empty(instance) || strlen(instance) > (MDNS_NAME_BUF_LEN - 1)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance_old, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }
    char *new_instance = strndup(instance, MDNS_NAME_BUF_LEN - 1);
    if (!new_instance) {
        return ESP_ERR_NO_MEM;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        free(new_instance);
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICE_INSTANCE_SET;
    action->data.srv_instance.service = s;
    action->data.srv_instance.instance = new_instance;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(new_instance);
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_instance_name_set(const char *service, const char *proto, const char *instance)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_instance_name_set_for_host(NULL, service, proto, _mdns_server->hostname, instance);
}

esp_err_t mdns_service_remove_for_host(const char *instance, const char *service, const char *proto, const char *hostname)
{
    if (!_mdns_server || !_mdns_server->services || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }
    mdns_srv_item_t *s = _mdns_get_service_item_instance(instance, service, proto, hostname);
    if (!s) {
        return ESP_ERR_NOT_FOUND;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICE_DEL;
    action->data.srv_del.service = s;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

esp_err_t mdns_service_remove(const char *service_type, const char *proto)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    return mdns_service_remove_for_host(NULL, service_type, proto, _mdns_server->hostname);
}

esp_err_t mdns_service_remove_all(void)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_ARG;
    }
    if (!_mdns_server->services) {
        return ESP_OK;
    }

    mdns_action_t *action = (mdns_action_t *)malloc(sizeof(mdns_action_t));
    if (!action) {
        HOOK_MALLOC_FAILED;
        return ESP_ERR_NO_MEM;
    }
    action->type = ACTION_SERVICES_CLEAR;
    if (xQueueSend(_mdns_server->action_queue, &action, (TickType_t)0) != pdPASS) {
        free(action);
        return ESP_ERR_NO_MEM;
    }
    return ESP_OK;
}

/*
 * MDNS QUERY
 * */

void mdns_query_results_free(mdns_result_t *results)
{
    mdns_result_t *r;
    mdns_ip_addr_t *a;

    while (results) {
        r = results;

        free((char *)(r->hostname));
        free((char *)(r->instance_name));
        free((char *)(r->service_type));
        free((char *)(r->proto));

        for (size_t i = 0; i < r->txt_count; i++) {
            free((char *)(r->txt[i].key));
            free((char *)(r->txt[i].value));
        }
        free(r->txt);
        free(r->txt_value_len);

        while (r->addr) {
            a = r->addr;
            r->addr = r->addr->next;
            free(a);
        }

        results = results->next;
        free(r);
    }
}

esp_err_t mdns_query_async_delete(mdns_search_once_t *search)
{
    if (!search) {
        return ESP_ERR_INVALID_ARG;
    }
    if (search->state != SEARCH_OFF) {
        return ESP_ERR_INVALID_STATE;
    }

    MDNS_SERVICE_LOCK();
    _mdns_search_free(search);
    MDNS_SERVICE_UNLOCK();

    return ESP_OK;
}

bool mdns_query_async_get_results(mdns_search_once_t *search, uint32_t timeout, mdns_result_t **results, uint8_t *num_results)
{
    if (xSemaphoreTake(search->done_semaphore, pdMS_TO_TICKS(timeout)) == pdTRUE) {
        if (results) {
            *results = search->result;
        }
        if (num_results) {
            *num_results = search->num_results;
        }
        return true;
    }
    return false;
}

mdns_search_once_t *mdns_query_async_new(const char *name, const char *service, const char *proto, uint16_t type,
        uint32_t timeout, size_t max_results, mdns_query_notify_t notifier)
{
    mdns_search_once_t *search = NULL;

    if (!_mdns_server || !timeout || _str_null_or_empty(service) != _str_null_or_empty(proto)) {
        return NULL;
    }

    search = _mdns_search_init(name, service, proto, type, type != MDNS_TYPE_PTR, timeout, max_results, notifier);
    if (!search) {
        return NULL;
    }

    if (_mdns_send_search_action(ACTION_SEARCH_ADD, search)) {
        _mdns_search_free(search);
        return NULL;
    }

    return search;
}

esp_err_t mdns_query_generic(const char *name, const char *service, const char *proto, uint16_t type, mdns_query_transmission_type_t transmission_type, uint32_t timeout, size_t max_results, mdns_result_t **results)
{
    mdns_search_once_t *search = NULL;

    *results = NULL;

    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }

    if (!timeout || _str_null_or_empty(service) != _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }

    search = _mdns_search_init(name, service, proto, type, transmission_type == MDNS_QUERY_UNICAST, timeout, max_results, NULL);
    if (!search) {
        return ESP_ERR_NO_MEM;
    }

    if (_mdns_send_search_action(ACTION_SEARCH_ADD, search)) {
        _mdns_search_free(search);
        return ESP_ERR_NO_MEM;
    }
    xSemaphoreTake(search->done_semaphore, portMAX_DELAY);

    *results = search->result;
    _mdns_search_free(search);

    return ESP_OK;
}

esp_err_t mdns_query(const char *name, const char *service_type, const char *proto, uint16_t type, uint32_t timeout, size_t max_results, mdns_result_t **results)
{
    return mdns_query_generic(name, service_type, proto, type, type != MDNS_TYPE_PTR, timeout, max_results, results);
}

esp_err_t mdns_query_ptr(const char *service, const char *proto, uint32_t timeout, size_t max_results, mdns_result_t **results)
{
    if (_str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }

    return mdns_query(NULL, service, proto, MDNS_TYPE_PTR, timeout, max_results, results);
}

esp_err_t mdns_query_srv(const char *instance, const char *service, const char *proto, uint32_t timeout, mdns_result_t **result)
{
    if (_str_null_or_empty(instance) || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }

    return mdns_query(instance, service, proto, MDNS_TYPE_SRV, timeout, 1, result);
}

esp_err_t mdns_query_txt(const char *instance, const char *service, const char *proto, uint32_t timeout, mdns_result_t **result)
{
    if (_str_null_or_empty(instance) || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }

    return mdns_query(instance, service, proto, MDNS_TYPE_TXT, timeout, 1, result);
}

esp_err_t mdns_lookup_delegated_service(const char *instance, const char *service, const char *proto, size_t max_results,
                                        mdns_result_t **result)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (!result || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }
    MDNS_SERVICE_LOCK();
    *result = _mdns_lookup_service(instance, service, proto, max_results, false);
    MDNS_SERVICE_UNLOCK();
    return ESP_OK;
}

esp_err_t mdns_lookup_selfhosted_service(const char *instance, const char *service, const char *proto, size_t max_results,
        mdns_result_t **result)
{
    if (!_mdns_server) {
        return ESP_ERR_INVALID_STATE;
    }
    if (!result || _str_null_or_empty(service) || _str_null_or_empty(proto)) {
        return ESP_ERR_INVALID_ARG;
    }
    MDNS_SERVICE_LOCK();
    *result = _mdns_lookup_service(instance, service, proto, max_results, true);
    MDNS_SERVICE_UNLOCK();
    return ESP_OK;
}

esp_err_t mdns_query_a(const char *name, uint32_t timeout, esp_ip4_addr_t *addr)
{
    mdns_result_t *result = NULL;
    esp_err_t err;

    if (_str_null_or_empty(name)) {
        return ESP_ERR_INVALID_ARG;
    }

    if (strstr(name, ".local")) {
        ESP_LOGW(TAG, "Please note that hostname must not contain domain name, as mDNS uses '.local' domain");
    }

    err = mdns_query(name, NULL, NULL, MDNS_TYPE_A, timeout, 1, &result);

    if (err) {
        return err;
    }

    if (!result) {
        return ESP_ERR_NOT_FOUND;
    }

    mdns_ip_addr_t *a = result->addr;
    while (a) {
        if (a->addr.type == ESP_IPADDR_TYPE_V4) {
            addr->addr = a->addr.u_addr.ip4.addr;
            mdns_query_results_free(result);
            return ESP_OK;
        }
        a = a->next;
    }

    mdns_query_results_free(result);
    return ESP_ERR_NOT_FOUND;
}

#if CONFIG_LWIP_IPV6
esp_err_t mdns_query_aaaa(const char *name, uint32_t timeout, esp_ip6_addr_t *addr)
{
    mdns_result_t *result = NULL;
    esp_err_t err;

    if (_str_null_or_empty(name)) {
        return ESP_ERR_INVALID_ARG;
    }

    if (strstr(name, ".local")) {
        ESP_LOGW(TAG, "Please note that hostname must not contain domain name, as mDNS uses '.local' domain");
    }

    err = mdns_query(name, NULL, NULL, MDNS_TYPE_AAAA, timeout, 1, &result);

    if (err) {
        return err;
    }

    if (!result) {
        return ESP_ERR_NOT_FOUND;
    }

    mdns_ip_addr_t *a = result->addr;
    while (a) {
        if (a->addr.type == ESP_IPADDR_TYPE_V6) {
            memcpy(addr->addr, a->addr.u_addr.ip6.addr, 16);
            mdns_query_results_free(result);
            return ESP_OK;
        }
        a = a->next;
    }

    mdns_query_results_free(result);
    return ESP_ERR_NOT_FOUND;
}
#endif

#ifdef MDNS_ENABLE_DEBUG

void mdns_debug_packet(const uint8_t *data, size_t len)
{
    static mdns_name_t n;
    mdns_header_t header;
    const uint8_t *content = data + MDNS_HEAD_LEN;
    uint32_t t = xTaskGetTickCount() * portTICK_PERIOD_MS;
    mdns_name_t *name = &n;
    memset(name, 0, sizeof(mdns_name_t));

    _mdns_dbg_printf("Packet[%u]: ", t);

    header.id = _mdns_read_u16(data, MDNS_HEAD_ID_OFFSET);
    header.flags = _mdns_read_u16(data, MDNS_HEAD_FLAGS_OFFSET);
    header.questions = _mdns_read_u16(data, MDNS_HEAD_QUESTIONS_OFFSET);
    header.answers = _mdns_read_u16(data, MDNS_HEAD_ANSWERS_OFFSET);
    header.servers = _mdns_read_u16(data, MDNS_HEAD_SERVERS_OFFSET);
    header.additional = _mdns_read_u16(data, MDNS_HEAD_ADDITIONAL_OFFSET);

    _mdns_dbg_printf("%s",
                     (header.flags == MDNS_FLAGS_QR_AUTHORITATIVE) ? "AUTHORITATIVE\n" :
                     (header.flags == MDNS_FLAGS_DISTRIBUTED) ? "DISTRIBUTED\n" :
                     (header.flags == 0) ? "\n" : " "
                    );
    if (header.flags && header.flags != MDNS_FLAGS_QR_AUTHORITATIVE) {
        _mdns_dbg_printf("0x%04X\n", header.flags);
    }

    if (header.questions) {
        uint8_t qs = header.questions;

        while (qs--) {
            content = _mdns_parse_fqdn(data, content, name, len);
            if (!content || content + MDNS_CLASS_OFFSET + 1 >= data + len) {
                header.answers = 0;
                header.additional = 0;
                header.servers = 0;
                _mdns_dbg_printf("ERROR: parse header questions\n");
                break;
            }

            uint16_t type = _mdns_read_u16(content, MDNS_TYPE_OFFSET);
            uint16_t mdns_class = _mdns_read_u16(content, MDNS_CLASS_OFFSET);
            bool unicast = !!(mdns_class & 0x8000);
            mdns_class &= 0x7FFF;
            content = content + 4;

            _mdns_dbg_printf("    Q: ");
            if (unicast) {
                _mdns_dbg_printf("*U* ");
            }
            if (type == MDNS_TYPE_PTR) {
                _mdns_dbg_printf("%s.%s%s.%s.%s. PTR ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_SRV) {
                _mdns_dbg_printf("%s.%s%s.%s.%s. SRV ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_TXT) {
                _mdns_dbg_printf("%s.%s%s.%s.%s. TXT ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_A) {
                _mdns_dbg_printf("%s.%s. A ", name->host, name->domain);
            } else if (type == MDNS_TYPE_AAAA) {
                _mdns_dbg_printf("%s.%s. AAAA ", name->host, name->domain);
            } else if (type == MDNS_TYPE_NSEC) {
                _mdns_dbg_printf("%s.%s%s.%s.%s. NSEC ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_ANY) {
                _mdns_dbg_printf("%s.%s%s.%s.%s. ANY ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain);
            } else {
                _mdns_dbg_printf("%s.%s%s.%s.%s. %04X ", name->host, name->sub ? "_sub." : "", name->service, name->proto, name->domain, type);
            }

            if (mdns_class == 0x0001) {
                _mdns_dbg_printf("IN");
            } else {
                _mdns_dbg_printf("%04X", mdns_class);
            }
            _mdns_dbg_printf("\n");
        }
    }

    if (header.answers || header.servers || header.additional) {
        uint16_t recordIndex = 0;

        while (content < (data + len)) {

            content = _mdns_parse_fqdn(data, content, name, len);
            if (!content) {
                _mdns_dbg_printf("ERROR: parse mdns records\n");
                break;
            }

            uint16_t type = _mdns_read_u16(content, MDNS_TYPE_OFFSET);
            uint16_t mdns_class = _mdns_read_u16(content, MDNS_CLASS_OFFSET);
            uint32_t ttl = _mdns_read_u32(content, MDNS_TTL_OFFSET);
            uint16_t data_len = _mdns_read_u16(content, MDNS_LEN_OFFSET);
            const uint8_t *data_ptr = content + MDNS_DATA_OFFSET;
            bool flush = !!(mdns_class & 0x8000);
            mdns_class &= 0x7FFF;

            content = data_ptr + data_len;
            if (content > (data + len)) {
                _mdns_dbg_printf("ERROR: content length overflow\n");
                break;
            }

            mdns_parsed_record_type_t record_type = MDNS_ANSWER;

            if (recordIndex >= (header.answers + header.servers)) {
                record_type = MDNS_EXTRA;
            } else if (recordIndex >= (header.answers)) {
                record_type = MDNS_NS;
            }
            recordIndex++;

            if (record_type == MDNS_EXTRA) {
                _mdns_dbg_printf("    X");
            } else if (record_type == MDNS_NS) {
                _mdns_dbg_printf("    S");
            } else {
                _mdns_dbg_printf("    A");
            }

            if (type == MDNS_TYPE_PTR) {
                _mdns_dbg_printf(": %s%s%s.%s.%s. PTR ", name->host, name->host[0] ? "." : "", name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_SRV) {
                _mdns_dbg_printf(": %s.%s.%s.%s. SRV ", name->host, name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_TXT) {
                _mdns_dbg_printf(": %s.%s.%s.%s. TXT ", name->host, name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_A) {
                _mdns_dbg_printf(": %s.%s. A ", name->host, name->domain);
            } else if (type == MDNS_TYPE_AAAA) {
                _mdns_dbg_printf(": %s.%s. AAAA ", name->host, name->domain);
            } else if (type == MDNS_TYPE_NSEC) {
                _mdns_dbg_printf(": %s.%s.%s.%s. NSEC ", name->host, name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_ANY) {
                _mdns_dbg_printf(": %s.%s.%s.%s. ANY ", name->host, name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_OPT) {
                _mdns_dbg_printf(": . OPT ");
            } else {
                _mdns_dbg_printf(": %s.%s.%s.%s. %04X ", name->host, name->service, name->proto, name->domain, type);
            }

            if (mdns_class == 0x0001) {
                _mdns_dbg_printf("IN ");
            } else {
                _mdns_dbg_printf("%04X ", mdns_class);
            }
            if (flush) {
                _mdns_dbg_printf("FLUSH ");
            }
            _mdns_dbg_printf("%u ", ttl);
            _mdns_dbg_printf("[%u] ", data_len);
            if (type == MDNS_TYPE_PTR) {
                if (!_mdns_parse_fqdn(data, data_ptr, name, len)) {
                    _mdns_dbg_printf("ERROR: parse PTR\n");
                    continue;
                }
                _mdns_dbg_printf("%s.%s.%s.%s.\n", name->host, name->service, name->proto, name->domain);
            } else if (type == MDNS_TYPE_SRV) {
                if (!_mdns_parse_fqdn(data, data_ptr + MDNS_SRV_FQDN_OFFSET, name, len)) {
                    _mdns_dbg_printf("ERROR: parse SRV\n");
                    continue;
                }
                uint16_t priority = _mdns_read_u16(data_ptr, MDNS_SRV_PRIORITY_OFFSET);
                uint16_t weight = _mdns_read_u16(data_ptr, MDNS_SRV_WEIGHT_OFFSET);
                uint16_t port = _mdns_read_u16(data_ptr, MDNS_SRV_PORT_OFFSET);
                _mdns_dbg_printf("%u %u %u %s.%s.\n", priority, weight, port, name->host, name->domain);
            } else if (type == MDNS_TYPE_TXT) {
                uint16_t i = 0, y;
                while (i < data_len) {
                    uint8_t partLen = data_ptr[i++];
                    if ((i + partLen) > data_len) {
                        _mdns_dbg_printf("ERROR: parse TXT\n");
                        break;
                    }
                    char txt[partLen + 1];
                    for (y = 0; y < partLen; y++) {
                        char d = data_ptr[i++];
                        txt[y] = d;
                    }
                    txt[partLen] = 0;
                    _mdns_dbg_printf("%s", txt);
                    if (i < data_len) {
                        _mdns_dbg_printf("; ");
                    }
                }
                _mdns_dbg_printf("\n");
            } else if (type == MDNS_TYPE_AAAA) {
                esp_ip6_addr_t ip6;
                memcpy(&ip6, data_ptr, sizeof(esp_ip6_addr_t));
                _mdns_dbg_printf(IPV6STR "\n", IPV62STR(ip6));
            } else if (type == MDNS_TYPE_A) {
                esp_ip4_addr_t ip;
                memcpy(&ip, data_ptr, sizeof(esp_ip4_addr_t));
                _mdns_dbg_printf(IPSTR "\n", IP2STR(&ip));
            } else if (type == MDNS_TYPE_NSEC) {
                const uint8_t *old_ptr = data_ptr;
                const uint8_t *new_ptr = _mdns_parse_fqdn(data, data_ptr, name, len);
                if (new_ptr) {
                    _mdns_dbg_printf("%s.%s.%s.%s. ", name->host, name->service, name->proto, name->domain);
                    size_t diff = new_ptr - old_ptr;
                    data_len -= diff;
                    data_ptr = new_ptr;
                }
                size_t i;
                for (i = 0; i < data_len; i++) {
                    _mdns_dbg_printf(" %02x", data_ptr[i]);
                }
                _mdns_dbg_printf("\n");
            } else if (type == MDNS_TYPE_OPT) {
                uint16_t opCode = _mdns_read_u16(data_ptr, 0);
                uint16_t opLen = _mdns_read_u16(data_ptr, 2);
                _mdns_dbg_printf(" Code: %04x Data[%u]:", opCode, opLen);
                size_t i;
                for (i = 4; i < data_len; i++) {
                    _mdns_dbg_printf(" %02x", data_ptr[i]);
                }
                _mdns_dbg_printf("\n");
            } else {
                size_t i;
                for (i = 0; i < data_len; i++) {
                    _mdns_dbg_printf(" %02x", data_ptr[i]);
                }
                _mdns_dbg_printf("\n");
            }
        }
    }
}
#endif