feat(examples): Move the slip example to esp-netif folder

And update the slip_modem_get_ipv6_address() to return the address by
copy instead of reference (to employ return value optimizaiton where
possible)

examples/esp_netif/slip_custom_netif/components/slip_modem/include/slip_modem.h

@@ -29,7 +29,6 @@
 
 extern esp_netif_netstack_config_t *netstack_default_slip;
 
-// Forward declare modem object
 typedef struct slip_modem slip_modem_t;
 
 // Filter callbacks for handling application specific slip messages
@@ -64,7 +63,7 @@ typedef struct {
  * @returns
  *          - slip modem driver glue object
  */
-slip_modem_t *slip_modem_create(esp_netif_t *slip_netif, slip_modem_config_t *modem_config);
+slip_modem_t *slip_modem_create(esp_netif_t *slip_netif, const slip_modem_config_t *modem_config);
 
 /** @brief Destroy a slip modem
  *
@@ -81,9 +80,9 @@ esp_err_t slip_modem_destroy(slip_modem_t *slip);
  * @param[in]    slip modem object
  *
  * @returns
- *          - ipv6 address
+ *          - ipv6 address returned by copy
  */
-const esp_ip6_addr_t *slip_modem_get_ipv6_address(slip_modem_t *slip);
+esp_ip6_addr_t slip_modem_get_ipv6_address(slip_modem_t *slip);
 
 /**
  * @brief  Data path API that forward the supplied data to the attached network interface
@@ -93,4 +92,4 @@ const esp_ip6_addr_t *slip_modem_get_ipv6_address(slip_modem_t *slip);
  * @param[in]    len length of the data
  *
  */
-void slip_modem_raw_output(slip_modem_t *slip, void *buffer, size_t len);
+void slip_modem_raw_write(slip_modem_t *slip, void *buffer, size_t len);

examples/esp_netif/slip_custom_netif/components/slip_modem/library/slip_modem.c

@@ -64,12 +64,11 @@ struct slip_modem {
 };
 
 
-// Forward function declaration
 static void slip_modem_uart_rx_task(void *arg);
 static esp_err_t slip_modem_post_attach(esp_netif_t *esp_netif, void *args);
 
 // Create a new slip modem
-slip_modem_t *slip_modem_create(esp_netif_t *slip_netif, slip_modem_config_t *modem_config)
+slip_modem_t *slip_modem_create(esp_netif_t *slip_netif, const slip_modem_config_t *modem_config)
 {
     ESP_LOGI(TAG, "%s: Creating slip modem (netif: %p)", __func__, slip_netif);
 
@@ -228,7 +227,7 @@ static void slip_modem_uart_rx_task(void *arg)
             esp_netif_receive(slip_modem->base.netif, slip_modem->buffer, len, NULL);
         }
 
-        // Yeild to allow other tasks to progress
+        // Yield to allow other tasks to progress
         vTaskDelay(1 * portTICK_PERIOD_MS);
     }
 }
@@ -236,12 +235,12 @@ static void slip_modem_uart_rx_task(void *arg)
 /**
  * @brief Gets the internally configured ipv6 address
  */
-const esp_ip6_addr_t *slip_modem_get_ipv6_address(slip_modem_t *slip)
+esp_ip6_addr_t slip_modem_get_ipv6_address(slip_modem_t *slip)
 {
-    return &slip->addr;
+    return slip->addr;
 }
 
-void slip_modem_raw_output(slip_modem_t *slip, void *buffer, size_t len)
+void slip_modem_raw_write(slip_modem_t *slip, void *buffer, size_t len)
 {
-    slip_modem_netif_raw_output(slip->base.netif, buffer, len);
+    slip_modem_netif_raw_write(slip->base.netif, buffer, len);
 }

examples/esp_netif/slip_custom_netif/components/slip_modem/library/slip_modem_netif.c

@@ -81,7 +81,7 @@ void esp_netif_lwip_slip_input(void *h, void *buffer, unsigned int len, void *eb
 /**
  * @brief Write raw data out the SLIP interface
  */
-void slip_modem_netif_raw_output(esp_netif_t *netif, void *buffer, size_t len)
+void slip_modem_netif_raw_write(esp_netif_t *netif, void *buffer, size_t len)
 {
     struct netif *lwip_netif = esp_netif_get_netif_impl(netif);
 

examples/esp_netif/slip_custom_netif/components/slip_modem/library/slip_modem_netif.h

@@ -39,4 +39,4 @@ esp_err_t slip_modem_netif_start(esp_netif_t *esp_netif, esp_ip6_addr_t *addr);
  * @return
  *         - ESP_OK on success
  */
-void slip_modem_netif_raw_output(esp_netif_t *netif, void *buffer, size_t len);
+void slip_modem_netif_raw_write(esp_netif_t *netif, void *buffer, size_t len);

examples/esp_netif/slip_custom_netif/main/slip_client_main.c

@@ -119,21 +119,21 @@ esp_err_t udp_rx_tx_init(void)
 static void slip_set_prefix(slip_modem_t *slip)
 {
     uint8_t buff[10] = {0};
-    const esp_ip6_addr_t *addr = slip_modem_get_ipv6_address(slip);
+    const esp_ip6_addr_t addr = slip_modem_get_ipv6_address(slip);
     ESP_LOGI(TAG, "%s: prefix set (%08x:%08x)", __func__,
-             lwip_ntohl(addr->addr[0]), lwip_ntohl(addr->addr[1]));
+             lwip_ntohl(addr.addr[0]), lwip_ntohl(addr.addr[1]));
 
     // Build slip set message
     buff[0] = '!';
     buff[1] = 'P';
     for (int i = 0; i < 2; i++) {
         for (int j = 0; j < 4; j++) {
-            buff[2 + i * 4 + j] = addr->addr[i] >> (j * 8);
+            buff[2 + i * 4 + j] = addr.addr[i] >> (j * 8);
         }
     }
 
     // Write raw data out the slip interface
-    slip_modem_raw_output(slip, buff, 2 + 8);
+    slip_modem_raw_write(slip, buff, 2 + 8);
 }
 
 // slip_rx_filter filters incoming commands from the slip interface