we dont support AI_V4MAPPED so hardcode IPv4 for now

Index: src/transports/udp_listeningpoint.c
--- src/transports/udp_listeningpoint.c.orig
+++ src/transports/udp_listeningpoint.c
@@ -65,7 +65,7 @@ BELLE_SIP_INSTANCIATE_CUSTOM_VPTR_BEGIN(belle_sip_udp_
 	belle_sip_set_socket_api(NULL);
 
 	snprintf(portnum, sizeof(portnum), "%i", *port);
-	hints.ai_family = AF_UNSPEC;
+	hints.ai_family = AF_INET;
 	hints.ai_socktype = SOCK_DGRAM;
 	hints.ai_protocol = IPPROTO_UDP;
 	hints.ai_flags = AI_NUMERICSERV;
