Fix a MediaRelay issue while processing a SDP without ICE containing …

…an IPv6 connection address, and flexisip has no IPv6 address available.

Previously, an empty connection address was set by the MediaRelay, causing a blank call. Now, the IPv4 address will be used as fallback, which will work if the network provides NAT64 service.

src/agent.cc

@@ -667,6 +667,7 @@ pair<string, string> Agent::getPreferredIp(const string &destination) const {
 	memset(&hints, 0, sizeof(hints));
 	hints.ai_family = AF_UNSPEC;
 	hints.ai_flags = AI_NUMERICHOST;
+	bool isIpv6;
 
 	struct addrinfo *result;
 	err = getaddrinfo(dest.c_str(), NULL, &hints, &result);
@@ -681,8 +682,12 @@ pair<string, string> Agent::getPreferredIp(const string &destination) const {
 	} else {
 		LOGE("getPreferredIp() getaddrinfo() error while resolving '%s': %s", dest.c_str(), gai_strerror(err));
 	}
-	return strchr(dest.c_str(), ':') == NULL ? make_pair(getResolvedPublicIp(), getRtpBindIp())
-											 : make_pair(getResolvedPublicIp(true), getRtpBindIp(true));
+	isIpv6 = strchr(dest.c_str(), ':') != NULL;
+	if (getResolvedPublicIp(true).empty()){
+		// If no IPv6 available, fallback to ipv4 and relay on NAT64.
+		return make_pair(getResolvedPublicIp(), getRtpBindIp());
+	}
+	return isIpv6 ? make_pair(getResolvedPublicIp(), getRtpBindIp()) : make_pair(getResolvedPublicIp(true), getRtpBindIp(true));
 }
 
 Agent::Network::Network(const Network &net) : mIP(net.mIP) {

src/callcontext-mediarelay.cc

@@ -48,8 +48,8 @@ void RelayedCall::enableTelephoneEventDrooping(bool value){
 
 void RelayedCall::setupSpecificRelayTransport(RelayTransport *rt, const char *destHost){
 	Agent *agent = mServer->getAgent();
-	bool isIpv6 = (strchr(destHost, ':') != nullptr);
 	auto relayIps = agent->getPreferredIp(destHost);
+	bool isIpv6 = strchr(relayIps.first.c_str(), ':') != nullptr;
 	if (isIpv6){
 		rt->mIpv6Address = relayIps.first;
 		rt->mIpv6BindAddress = relayIps.second;
@@ -97,7 +97,7 @@ void RelayedCall::initChannels ( const std::shared_ptr< SdpModifier >& m, const
 		rt.mIpv4Address = agent->getResolvedPublicIp(false);
 		rt.mIpv6BindAddress = agent->getRtpBindIp(true);
 		rt.mIpv4BindAddress = agent->getRtpBindIp(false);
-		rt.mPreferredFamily = isIpv6 ? AF_INET6 : AF_INET;
+		rt.mPreferredFamily = (!rt.mIpv6Address.empty() && isIpv6) ? AF_INET6 : AF_INET;
 		rt.mDualStackRequired = hasIce && !rt.mIpv6Address.empty();
 
 		if (s == NULL) {