Add DNS Server

libraries/DNSServer/src/DNSServer.h

@@ -0,0 +1,76 @@
+#ifndef DNSServer_h
+#define DNSServer_h
+#include <WiFiUdp.h>
+
+#define DNS_QR_QUERY 0
+#define DNS_QR_RESPONSE 1
+#define DNS_OPCODE_QUERY 0
+
+enum class DNSReplyCode
+{
+  NoError = 0,
+  FormError = 1,
+  ServerFailure = 2,
+  NonExistentDomain = 3,
+  NotImplemented = 4,
+  Refused = 5,
+  YXDomain = 6,
+  YXRRSet = 7,
+  NXRRSet = 8
+};
+
+struct DNSHeader
+{
+  uint16_t ID;               // identification number
+  union {
+    struct {
+      uint16_t RD : 1;      // recursion desired
+      uint16_t TC : 1;      // truncated message
+      uint16_t AA : 1;      // authoritive answer
+      uint16_t OPCode : 4;  // message_type
+      uint16_t QR : 1;      // query/response flag
+      uint16_t RCode : 4;   // response code
+      uint16_t Z : 3;       // its z! reserved
+      uint16_t RA : 1;      // recursion available
+    };
+    uint16_t Flags;
+  };
+  uint16_t QDCount;          // number of question entries
+  uint16_t ANCount;          // number of answer entries
+  uint16_t NSCount;          // number of authority entries
+  uint16_t ARCount;          // number of resource entries
+};
+
+class DNSServer
+{
+  public:
+    DNSServer();
+    void processNextRequest();
+    void setErrorReplyCode(const DNSReplyCode &replyCode);
+    void setTTL(const uint32_t &ttl);
+
+    // Returns true if successful, false if there are no sockets available
+    bool start(const uint16_t &port,
+              const String &domainName,
+              const IPAddress &resolvedIP);
+    // stops the DNS server
+    void stop();
+
+  private:
+    WiFiUDP _udp;
+    uint16_t _port;
+    String _domainName;
+    unsigned char _resolvedIP[4];
+    int _currentPacketSize;
+    unsigned char* _buffer;
+    DNSHeader* _dnsHeader;
+    uint32_t _ttl;
+    DNSReplyCode _errorReplyCode;
+
+    void downcaseAndRemoveWwwPrefix(String &domainName);
+    String getDomainNameWithoutWwwPrefix();
+    bool requestIncludesOnlyOneQuestion();
+    void replyWithIP();
+    void replyWithCustomCode();
+};
+#endif