ws2_32: Move the getsockopt(IP_MULTICAST_IF) implementation to ntdll.

dlls/ntdll/unix/socket.c

@@ -1750,6 +1750,9 @@ NTSTATUS sock_ioctl( HANDLE handle, HANDLE event, PIO_APC_ROUTINE apc, void *apc
             return do_setsockopt( handle, io, IPPROTO_IP, IP_HDRINCL, in_buffer, in_size );
 #endif
 
+        case IOCTL_AFD_WINE_GET_IP_MULTICAST_IF:
+            return do_getsockopt( handle, io, IPPROTO_IP, IP_MULTICAST_IF, out_buffer, out_size );
+
         default:
         {
             if ((code >> 16) == FILE_DEVICE_NETWORK)

dlls/ws2_32/socket.c

@@ -2440,6 +2440,8 @@ INT WINAPI WS_getsockopt(SOCKET s, INT level,
             return server_getsockopt( s, IOCTL_AFD_WINE_GET_IP_HDRINCL, optval, optlen );
 
         case WS_IP_MULTICAST_IF:
+            return server_getsockopt( s, IOCTL_AFD_WINE_GET_IP_MULTICAST_IF, optval, optlen );
+
         case WS_IP_MULTICAST_LOOP:
         case WS_IP_MULTICAST_TTL:
         case WS_IP_OPTIONS:

include/wine/afd.h

@@ -190,6 +190,7 @@ struct afd_get_events_params
 #define IOCTL_AFD_WINE_SET_IP_DROP_SOURCE_MEMBERSHIP    WINE_AFD_IOC(245)
 #define IOCTL_AFD_WINE_GET_IP_HDRINCL                   WINE_AFD_IOC(246)
 #define IOCTL_AFD_WINE_SET_IP_HDRINCL                   WINE_AFD_IOC(247)
+#define IOCTL_AFD_WINE_GET_IP_MULTICAST_IF              WINE_AFD_IOC(248)
 
 struct afd_create_params
 {