xmpp: Implement syncStreams()

This should ensure that the incoming and outgoing XML streams are in
sync.

1 files changed, 30 insertions, 0 deletions

diff --git a/xmpp/stream_pair.go b/xmpp/stream_pair.go
index 6224a77..e02cca6 100644
--- a/xmpp/stream_pair.go
+++ b/xmpp/stream_pair.go
@@ -42,6 +42,36 @@ func openStream(s *session) {
 	if err != nil {
 		log.Println("Could not encode stream start!")
 	}
+
+	syncStreams(s)
+}
+
+// syncStreams drops XML tokens from the receiving stream until an
+// xml.StartElement with the local name `stream` is received. If this function
+// is called after opening a new stream in the sending direction it is ensured
+// that both streams directions work on the same stream level and are in sync.
+// Tokens received which are not a stream StartElement are not handled but
+// logged since this should not happen.
+func syncStreams(s *session) {
+	for {
+		select {
+		case data := <-s.in:
+			switch data.(type) {
+			case SessionShouldDisconnect:
+				return
+			default:
+				log.Printf("Unhandled data '%d' during stream sync!\n", data)
+			}
+		case t := <-s.rx:
+			switch token := t.(type) {
+			case xml.StartElement:
+				if token.Name.Local == "stream" {
+					return
+				}
+			}
+			log.Printf("Unhandled XML token '%v' during stream sync!\n", t)
+		}
+	}
 }
 
 func closeStream(s *session) {