LwipIntfDev - config static IP auto gw,mask,dns as in Arduino libraries

for 'modern' Ethernet libraries W5100lwIP, W5500lwIP and ENC28J60lwIP
used without EthernetCompat

Author: JAndrassy

cores/esp8266/LwipIntfDev.h

@@ -63,9 +63,14 @@ class LwipIntfDev: public LwipIntf, public RawDev
         memset(&_netif, 0, sizeof(_netif));
     }
 
+    //The argument order for ESP is not the same as for Arduino. However, there is compatibility code under the hood
+    //to detect Arduino arg order, and handle it correctly.
     boolean config(const IPAddress& local_ip, const IPAddress& arg1, const IPAddress& arg2,
                    const IPAddress& arg3 = IPADDR_NONE, const IPAddress& dns2 = IPADDR_NONE);
 
+    // two and one parameter version. 2nd parameter is DNS like in Arduino. IPv4 only
+    boolean config(IPAddress local_ip, IPAddress dns = INADDR_ANY);
+
     // default mac-address is inferred from esp8266's STA interface
     boolean begin(const uint8_t* macAddress = nullptr, const uint16_t mtu = DEFAULT_MTU);
     void    end();
@@ -209,6 +214,25 @@ boolean LwipIntfDev<RawDev>::config(const IPAddress& localIP, const IPAddress& g
     return true;
 }
 
+template<class RawDev>
+boolean LwipIntfDev<RawDev>::config(IPAddress local_ip, IPAddress dns)
+{
+
+    if (!local_ip.isSet())
+        return config(INADDR_ANY, INADDR_ANY, INADDR_ANY);
+
+    if (!local_ip.isV4())
+        return false;
+
+    IPAddress gw(local_ip);
+    gw[3] = 1;
+    if (!dns.isSet())
+    {
+        dns = gw;
+    }
+    return config(local_ip, gw, IPAddress(255, 255, 255, 0), dns);
+}
+
 template<class RawDev>
 boolean LwipIntfDev<RawDev>::begin(const uint8_t* macAddress, const uint16_t mtu)
 {
@@ -336,9 +360,6 @@ template<class RawDev>
 void LwipIntfDev<RawDev>::end()
 {
     netif_remove(&_netif);
-    ip_addr_copy(_netif.ip_addr, ip_addr_any);  // to allow DHCP at next begin
-    ip_addr_copy(_netif.netmask, ip_addr_any);
-    ip_addr_copy(_netif.gw, ip_addr_any);
     _started = false;
     RawDev::end();
 }

libraries/lwIP_Ethernet/src/EthernetCompat.h

@@ -86,6 +86,13 @@ class ArduinoEthernet: public LwipIntfDev<RawDev>
         return ret;
     }
 
+    void end()
+    {
+        ip_addr_copy(LwipIntfDev<RawDev>::_netif.ip_addr,
+                     ip_addr_any);  // to allow DHCP at next begin
+        LwipIntfDev<RawDev>::end();
+    }
+
     HardwareStatus hardwareStatus() const
     {
         return _hardwareStatus;