Return interface address for NetBIOS name lookup

When NetBIOS returns a match, it should return the IP address of the device.
Presently, however, it returns the address of multicast IP for the subnet
since the incoming NBNS packet's UDP target will be multicast
(i.e. 192.168.1.255).

Iterate over the active network interfaces and check netmasks to determine
where the packet came from, and return the appropriate IP interface address
instead.

Author: earlephilhower

libraries/NetBIOS/src/NetBIOS.cpp

@@ -1,5 +1,8 @@
 #include "NetBIOS.h"
 #include <functional>
+extern "C" {
+#include <lwip/netif.h>
+}; // extern "C"
 
 #define NBNS_PORT             137
 #define NBNS_MAX_HOSTNAME_LEN 32
@@ -91,7 +94,16 @@ void NetBIOS::_onPacket(AsyncUDPPacket &packet) {
         append_32((void *)&nbnsa.ttl, 300000);
         append_16((void *)&nbnsa.data_len, 6);
         append_16((void *)&nbnsa.flags, 0);
-        nbnsa.addr = packet.localIP();
+        nbnsa.addr = packet.localIP(); // By default, should be overridden below
+        // Iterate over all netifs, see if the incoming address matches one of the netmaskes networks
+        for (auto netif = netif_list; netif; netif = netif->next) {
+          auto maskedip = ip4_addr_get_u32(netif_ip4_addr(netif)) & ip4_addr_get_u32(netif_ip4_netmask(netif));
+          auto maskedin = ((uint32_t)packet.localIP()) & ip4_addr_get_u32(netif_ip4_netmask(netif));
+          if (maskedip == maskedin) {
+            nbnsa.addr = ip4_addr_get_u32(netif_ip4_addr(netif));
+            break;
+          }
+        }
         _udp.writeTo((uint8_t *)&nbnsa, sizeof(nbnsa), packet.remoteIP(), NBNS_PORT);
       }
     }