task #7507, patch #6786: DNS supports static hosts table. New configuration options DNS_LOCAL_HOSTLIST and DNS_LOCAL_HOSTLIST_IS_DYNAMIC.

src/include/lwip/dns.h

@@ -87,6 +87,12 @@ struct ip_addr dns_getserver(u8_t numdns);
 err_t          dns_gethostbyname(const char *hostname, struct ip_addr *addr,
                                  dns_found_callback found, void *callback_arg);
 
+#if DNS_LOCAL_HOSTLIST && DNS_LOCAL_HOSTLIST_IS_DYNAMIC
+int            dns_local_removehostname(const char *hostname);
+int            dns_local_removehostaddr(const struct ip_addr *addr);
+err_t          dns_local_addhost(const char *hostname, const struct ip_addr *addr);
+#endif /* DNS_LOCAL_HOSTLIST && DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
+
 #endif /* LWIP_DNS */
 
 #endif /* __LWIP_DNS_H__ */

src/include/lwip/opt.h

@@ -148,7 +148,7 @@
 /**
  * MEM_USE_POOLS==1: Use an alternative to malloc() by allocating from a set
  * of memory pools of various sizes. When mem_malloc is called, an element of
- * the smallest pool that can provide the lenght needed is returned.
+ * the smallest pool that can provide the length needed is returned.
  */
 #ifndef MEM_USE_POOLS
 #define MEM_USE_POOLS                   0
@@ -635,6 +635,22 @@
 #define DNS_MSG_SIZE                    512
 #endif
 
+/** DNS_LOCAL_HOSTLIST: Implements a local host-to-address list. If enabled,
+ *  you have to define
+ *    #define DNS_LOCAL_HOSTLIST_INIT {{"host1", 0x123}, {"host2", 0x234}}
+ *  (an array of structs name/address, where address is an u32_t in network
+ *  byte order).
+ */
+#ifndef DNS_LOCAL_HOSTLIST
+#define DNS_LOCAL_HOSTLIST              0
+#endif /* DNS_LOCAL_HOSTLIST */
+
+/** If this is turned on, the local host-list can be dynamically changed
+ *  at runtime. */
+#ifndef DNS_LOCAL_HOSTLIST_IS_DYNAMIC
+#define DNS_LOCAL_HOSTLIST_IS_DYNAMIC   0
+#endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
+
 /*
    ---------------------------------
    ---------- UDP options ----------