dns: added one-shot multicast DNS queries

src/include/lwip/dns.h

@@ -84,6 +84,13 @@ struct local_hostlist_entry {
 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
 #endif /* DNS_LOCAL_HOSTLIST */
 
+#if LWIP_IPV4
+extern const ip_addr_t dns_mquery_v4group;
+#endif /* LWIP_IPV4 */
+#if LWIP_IPV6
+extern const ip_addr_t dns_mquery_v6group;
+#endif /* LWIP_IPV6 */
+
 /** Callback which is invoked when a hostname is found.
  * A function of this type must be implemented by the application using the DNS resolver.
  * @param name pointer to the name that was looked up.

src/include/lwip/opt.h

@@ -1057,6 +1057,12 @@
 #if !defined DNS_LOCAL_HOSTLIST_IS_DYNAMIC || defined __DOXYGEN__
 #define DNS_LOCAL_HOSTLIST_IS_DYNAMIC   0
 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
+
+/** Set this to 1 to enable querying ".local" names via mDNS
+ *  using a One-Shot Multicast DNS Query */
+#if !defined LWIP_DNS_SUPPORT_MDNS_QUERIES || defined __DOXYGEN__
+#define LWIP_DNS_SUPPORT_MDNS_QUERIES  0
+#endif
 /**
  * @}
  */

src/include/lwip/prot/dns.h

@@ -115,6 +115,24 @@ PACK_STRUCT_END
 #endif
 #define SIZEOF_DNS_HDR 12
 
+
+/* Multicast DNS definitions */
+
+/** UDP port for multicast DNS queries */
+#ifndef DNS_MQUERY_PORT
+#define DNS_MQUERY_PORT             5353
+#endif
+
+/* IPv4 group for multicast DNS queries: 224.0.0.251 */
+#ifndef DNS_MQUERY_IPV4_GROUP_INIT
+#define DNS_MQUERY_IPV4_GROUP_INIT  IPADDR4_INIT_BYTES(224,0,0,251)
+#endif
+
+/* IPv6 group for multicast DNS queries: FF02::FB */
+#ifndef DNS_MQUERY_IPV6_GROUP_INIT
+#define DNS_MQUERY_IPV6_GROUP_INIT  IPADDR6_INIT_HOST(0xFF020000,0,0,0xFB)
+#endif
+
 #ifdef __cplusplus
 }
 #endif