specify actual mtu in our RI for i2pv6

RouterContext.cpp

@@ -162,7 +162,13 @@ namespace i2p
 		{
 			// create new address
 			m_RouterInfo.AddNTCPAddress (host.to_string ().c_str (), port);
-			m_RouterInfo.AddSSUAddress (host.to_string ().c_str (), port, GetIdentHash (), 1472); // TODO
+			auto mtu = i2p::util::net::GetMTU (host);
+			if (mtu)
+			{	
+				LogPrint ("Our v6 MTU=", mtu);
+				if (mtu > 1472) mtu = 1472; 
+			}	
+			m_RouterInfo.AddSSUAddress (host.to_string ().c_str (), port, GetIdentHash (), mtu ? mtu : 1472); // TODO
 			updated = true;
 		}
 		if (updated)

util.cpp

@@ -411,6 +411,7 @@ namespace net
 		// loook for interface matching local address	
 		for (ifa = ifaddr; ifa != nullptr; ifa = ifa->ifa_next) 
 		{
+			if (!ifa->ifa_addr) continue;
         	family = ifa->ifa_addr->sa_family;
 			if (family == AF_INET && localAddress.is_v4 ())
 			{