ESP8266: Add built-in DNS resolution (disabled by default)

components/wifi/esp8266-driver/ESP8266/ESP8266.cpp

@@ -609,7 +609,11 @@ nsapi_error_t ESP8266::open_tcp(int id, const char *addr, int port, int keepaliv
 bool ESP8266::dns_lookup(const char *name, char *ip)
 {
     _smutex.lock();
-    bool done = _parser.send("AT+CIPDOMAIN=\"%s\"", name) && _parser.recv("+CIPDOMAIN:%s%*[\r]%*[\n]", ip);
+    set_timeout(ESP8266_DNS_TIMEOUT);
+    bool done = _parser.send("AT+CIPDOMAIN=\"%s\"", name)
+                && _parser.recv("+CIPDOMAIN:%15[^\n]\n", ip)
+                && _parser.recv("OK\n");
+    set_timeout();
     _smutex.unlock();
 
     return done;

components/wifi/esp8266-driver/ESP8266/ESP8266.h

@@ -43,6 +43,9 @@
 #ifndef ESP8266_MISC_TIMEOUT
 #define ESP8266_MISC_TIMEOUT    2000
 #endif
+#ifndef ESP8266_DNS_TIMEOUT
+#define ESP8266_DNS_TIMEOUT     15000
+#endif
 
 #define ESP8266_SCAN_TIME_MIN 0     // [ms]
 #define ESP8266_SCAN_TIME_MAX 1500  // [ms]

components/wifi/esp8266-driver/ESP8266Interface.cpp

@@ -652,6 +652,28 @@ int ESP8266Interface::scan(WiFiAccessPoint *res, unsigned count, scan_mode mode,
     return ret;
 }
 
+#if MBED_CONF_ESP8266_BUILT_IN_DNS
+nsapi_error_t ESP8266Interface::gethostbyname(const char *name, SocketAddress *address, nsapi_version_t version, const char *interface_name)
+{
+    char ip[NSAPI_IPv4_SIZE];
+    memset(ip, 0, NSAPI_IPv4_SIZE);
+    if (!_esp.dns_lookup(name, ip)) {
+        return NSAPI_ERROR_DNS_FAILURE;
+    }
+    if (!address->set_ip_address(ip)) {
+        return NSAPI_ERROR_DNS_FAILURE;
+    }
+
+    return NSAPI_ERROR_OK;
+}
+
+
+nsapi_error_t ESP8266Interface::add_dns_server(const SocketAddress &address, const char *interface_name)
+{
+    return NSAPI_ERROR_OK;
+}
+#endif
+
 bool ESP8266Interface::_get_firmware_ok()
 {
     ESP8266::fw_at_version at_v = _esp.at_version();

components/wifi/esp8266-driver/ESP8266Interface.h

@@ -228,14 +228,25 @@ public:
      *                  version is chosen by the stack (defaults to NSAPI_UNSPEC)
      *  @return         0 on success, negative error code on failure
      */
+#if MBED_CONF_ESP8266_BUILT_IN_DNS
+    nsapi_error_t gethostbyname(const char *name, SocketAddress *address, nsapi_version_t version, const char *interface_name);
+#else
     using NetworkInterface::gethostbyname;
+#endif
+
+    using NetworkInterface::gethostbyname_async;
+    using NetworkInterface::gethostbyname_async_cancel;
 
     /** Add a domain name server to list of servers to query
      *
      *  @param addr     Destination for the host address
      *  @return         0 on success, negative error code on failure
      */
+#if MBED_CONF_ESP8266_BUILT_IN_DNS
+    nsapi_error_t add_dns_server(const SocketAddress &address, const char *interface_name);
+#else
     using NetworkInterface::add_dns_server;
+#endif
 
     /** @copydoc NetworkStack::setsockopt
      */

components/wifi/esp8266-driver/mbed_lib.json

@@ -65,6 +65,10 @@
         "channels": {
             "help": "channel count, 13 by default",
             "value": null
+        },
+        "built-in-dns": {
+            "help": "use built-in CIPDOMAIN AT command to resolve address to IP",
+            "value": false
         }
     },
     "target_overrides": {