Allow a second call to initQUICSockets. (scionproto#79)

* Allow a second call to initQUICSockets.

Force the port to zero before the second call.

* use a parameter to ignore the port

* fix comment

go/lib/infra/infraenv/infraenv.go

@@ -104,7 +104,7 @@ func (nc *NetworkConfig) QUICStack() (*QUICStack, error) {
 	if nc.QUIC.Address == "" {
 		nc.QUIC.Address = net.JoinHostPort(nc.Public.IP.String(), "0")
 	}
-	client, server, err := nc.initQUICSockets()
+	client, server, err := nc.initQUICSockets(false)
 	if err != nil {
 		return nil, err
 	}
@@ -121,7 +121,9 @@ func (nc *NetworkConfig) QUICStack() (*QUICStack, error) {
 	}
 
 	//TLS/QUIC part
-	tlsClient, tlsServer, err := nc.initQUICSockets()
+	// Calling initQUICSockets again will fail if nc.QUIC.Address has a port other than 0.
+	// As a workaround, forcefully set the port to 0 via a parameter.
+	tlsClient, tlsServer, err := nc.initQUICSockets(true)
 	if err != nil {
 		return nil, err
 	}
@@ -283,7 +285,7 @@ func (nc *NetworkConfig) initSvcRedirect(quicAddress string, tlsQUICAdress strin
 	return cancel, nil
 }
 
-func (nc *NetworkConfig) initQUICSockets() (net.PacketConn, net.PacketConn, error) {
+func (nc *NetworkConfig) initQUICSockets(ignorePort bool) (net.PacketConn, net.PacketConn, error) {
 	dispatcherService := reliable.NewDispatcher("")
 	if nc.ReconnectToDispatcher {
 		dispatcherService = reconnect.NewDispatcherService(dispatcherService)
@@ -303,6 +305,9 @@ func (nc *NetworkConfig) initQUICSockets() (net.PacketConn, net.PacketConn, erro
 	if err != nil {
 		return nil, nil, serrors.WrapStr("parsing server QUIC address", err)
 	}
+	if ignorePort {
+		serverAddr.Port = 0
+	}
 	server, err := serverNet.Listen(context.Background(), "udp", serverAddr, addr.SvcNone)
 	if err != nil {
 		return nil, nil, serrors.WrapStr("creating server connection", err)