net: socket: Add support for SO_DOMAIN option

The getsockopt() will return the address domain of the given
socket like AF_INET or AF_INET6.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

include/zephyr/net/socket.h

@@ -1166,7 +1166,7 @@ struct ifreq {
 /** Protocol used with the socket */
 #define SO_PROTOCOL 38
 
-/** Domain used with SOCKET (ignored, for compatibility) */
+/** Domain used with SOCKET */
 #define SO_DOMAIN 39
 
 /** Enable SOCKS5 for Socket */

subsys/net/lib/sockets/sockets.c

@@ -2447,6 +2447,18 @@ int zsock_getsockopt_ctx(struct net_context *ctx, int level, int optname,
 
 			return 0;
 		}
+
+		case SO_DOMAIN: {
+			if (*optlen != sizeof(int)) {
+				errno = EINVAL;
+				return -1;
+			}
+
+			*(int *)optval = net_context_get_family(ctx);
+
+			return 0;
+		}
+
 		break;
 
 		case SO_RCVBUF: