Return the new channel from RequestOpenChannel

This fixes a quirk where it would've been difficult to tell which of
several channels of the same type+direction is the one you just created.

It's also a fairly common pattern to want to interact with a channel
right after opening it; for example, a chat channel is opened and can
immediately send messages before getting the peer response. It's
convenient to not have to do a separate lookup.

connection/connection.go

@@ -109,9 +109,10 @@ func (rc *Connection) Do(do func() error) error {
 // An error is returned only if the requirements for opening this channel
 // are not met on the local side (a nil error return does not mean the
 // channel was opened successfully, because channels open asynchronously).
-func (rc *Connection) RequestOpenChannel(ctype string, handler channels.Handler) error {
+func (rc *Connection) RequestOpenChannel(ctype string, handler channels.Handler) (*channels.Channel, error) {
 	rc.traceLog(fmt.Sprintf("requesting open channel of type %s", ctype))
-	return rc.Do(func() error {
+	var channel *channels.Channel
+	err := rc.Do(func() error {
 		// Check that we have the authentication already
 		if handler.RequiresAuthentication() != "none" {
 			// Enforce Authentication Check.
@@ -121,7 +122,8 @@ func (rc *Connection) RequestOpenChannel(ctype string, handler channels.Handler)
 			}
 		}
 
-		channel, err := rc.channelManager.OpenChannelRequest(handler)
+		var err error
+		channel, err = rc.channelManager.OpenChannelRequest(handler)
 
 		if err != nil {
 			rc.traceLog(fmt.Sprintf("failed to request open channel of type %v", err))
@@ -148,6 +150,7 @@ func (rc *Connection) RequestOpenChannel(ctype string, handler channels.Handler)
 		}
 		return nil
 	})
+	return channel, err
 }
 
 // Process receives socket and protocol events for the connection. Methods

connection/outboundconnectionhandler.go

@@ -48,7 +48,7 @@ func (och *OutboundConnectionHandler) ProcessAuthAsClient(privateKey *rsa.Privat
 		och.connection.Break()
 	}
 
-	err := och.connection.RequestOpenChannel("im.ricochet.auth.hidden-service",
+	_, err := och.connection.RequestOpenChannel("im.ricochet.auth.hidden-service",
 		&channels.HiddenServiceAuthChannel{
 			PrivateKey:       privateKey,
 			ServerHostname:   och.connection.RemoteHostname,

examples/echobot/main.go

@@ -64,7 +64,7 @@ func (echobot *RicochetEchoBot) Connect(privateKeyFile string, hostname string)
 		go rc.Process(echobot)
 
 		if !known {
-			err := rc.RequestOpenChannel("im.ricochet.contact.request", &channels.ContactRequestChannel{Handler: echobot})
+			_, err := rc.RequestOpenChannel("im.ricochet.contact.request", &channels.ContactRequestChannel{Handler: echobot})
 			if err != nil {
 				log.Printf("could not contact %s", err)
 			}