[nsapi] Adopted netconn_gethostbyname in the lwip interface

Provides proper integration with DHCP through lwip

Author: geky

features/net/FEATURE_IPV4/lwip-interface/lwip_stack.c

@@ -217,7 +217,7 @@ static int lwip_err_remap(err_t err) {
 
 
 /* LWIP network stack implementation */
-static nsapi_addr_t lwip_get_addr(nsapi_stack_t *stack)
+static nsapi_addr_t lwip_getaddr(nsapi_stack_t *stack)
 {
     if (!lwip_get_ip_address()) {
         return (nsapi_addr_t){0};
@@ -229,6 +229,17 @@ static nsapi_addr_t lwip_get_addr(nsapi_stack_t *stack)
     return addr;
 }
 
+static int lwip_gethostbyname(nsapi_stack_t *stack, nsapi_addr_t *addr, const char *host)
+{
+    err_t err = netconn_gethostbyname(host, (ip_addr_t *)addr->bytes);
+    if (err != ERR_OK) {
+        return NSAPI_ERROR_DNS_FAILURE;
+    }
+
+    addr->version = NSAPI_IPv4;
+    return 0;
+}
+
 static int lwip_socket_open(nsapi_stack_t *stack, nsapi_socket_t *handle, nsapi_protocol_t proto)
 {
     struct lwip_socket *s = lwip_arena_alloc();
@@ -449,7 +460,8 @@ static void lwip_socket_attach(nsapi_stack_t *stack, nsapi_socket_t handle, void
 
 /* LWIP network stack */
 const nsapi_stack_api_t lwip_stack_api = {
-    .get_ip_address     = lwip_get_addr,
+    .get_ip_address     = lwip_getaddr,
+    .gethostbyname      = lwip_gethostbyname,
     .socket_open        = lwip_socket_open,
     .socket_close       = lwip_socket_close,
     .socket_bind        = lwip_socket_bind,

features/net/FEATURE_IPV4/lwip-interface/lwipopts.h

@@ -66,6 +66,7 @@
 
 #define LWIP_DHCP                   1
 #define LWIP_DNS                    1
+#define LWIP_SOCKET                 0
 
 #define SO_REUSE                    1