Add dial interruption support to plugin dialers.

psiphon/common/pluginProtocol.go

@@ -38,8 +38,11 @@ type PluginProtocolNetDialer func(network, addr string) (net.Conn, error)
 // connection(s) and sends its log messages to loggerOutput.
 // PluginProtocolDialer returns true if it attempts to create
 // a connection, or false if it decides not to attempt a connection.
+// PluginProtocolDialer must add its connection to pendingConns
+// before the initial dial to allow for interruption.
 type PluginProtocolDialer func(
 	loggerOutput io.Writer,
+	pendingConns *Conns,
 	netDialer PluginProtocolNetDialer,
 	addr string) (
 	bool, net.Conn, error)
@@ -54,13 +57,15 @@ func RegisterPluginProtocol(protcolDialer PluginProtocolDialer) {
 // if set, to connect to addr over the plugin protocol.
 func DialPluginProtocol(
 	loggerOutput io.Writer,
+	pendingConns *Conns,
 	netDialer PluginProtocolNetDialer,
 	addr string) (
 	bool, net.Conn, error) {
 
 	dialer := registeredPluginProtocolDialer.Load()
 	if dialer != nil {
-		return dialer.(PluginProtocolDialer)(loggerOutput, netDialer, addr)
+		return dialer.(PluginProtocolDialer)(
+			loggerOutput, pendingConns, netDialer, addr)
 	}
 	return false, nil, nil
 }

psiphon/tunnel.go

@@ -695,6 +695,7 @@ func dialSsh(
 		var dialedPlugin bool
 		dialedPlugin, dialConn, err = common.DialPluginProtocol(
 			NewNoticeWriter("DialPluginProtocol"),
+			pendingConns,
 			func(_, addr string) (net.Conn, error) {
 
 				// Use a copy of DialConfig without pendingConns