Keep the gateway connection alive and resume hosted queues after reconnecting

The client doesn't ping while it's sending, so when the proxy answers its frames itself (everything it
sends in a hosted room), IMVU's gateway saw an idle connection and closed it after about a minute. A
ping now goes to the gateway in place of each answered frame. And after a reconnect, hosted rooms'
queues are taken out of C2gOpenFloodgates and answered here (the gateway never answered them, so the
client gave up and closed the room).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/proxy/connect.go

@@ -253,12 +253,33 @@ func (st *stream) filtered(f imq.Frame, frame []byte) []byte {
 			}
 			rest := router.Route(st.conn, f.Type == imq.C2gUnsubscribe, sub)
 			if rest.Empty() {
-				return nil
+				return keepalive()
 			}
 			if len(rest.All()) == len(sub.All()) {
 				return frame
 			}
 			return imq.EncodeFrame(f.Type, rest.Marshal())
+		case imq.C2gOpenFloodgates:
+			// Resuming queues after a reconnect: the router's are answered here, the rest go to the gateway.
+			router, ok := st.watcher.(IMQRouter)
+			if !ok {
+				return frame
+			}
+			states, err := imq.ParseFloodgates(f.Data)
+			if err != nil {
+				return frame
+			}
+			var rest []imq.QueueOp
+			for _, q := range states {
+				if router.Route(st.conn, false, imq.Subscription{WithResults: []imq.QueueOp{q}}).Empty() {
+					continue
+				}
+				rest = append(rest, q)
+			}
+			if len(rest) == len(states) {
+				return frame
+			}
+			return imq.EncodeFrame(imq.C2gOpenFloodgates, imq.MarshalFloodgates(rest))
 		case imq.G2cSendMessage:
 			m, err := imq.ParseDelivered(f.Data)
 			if err != nil {
@@ -284,7 +305,7 @@ func (st *stream) filtered(f imq.Frame, frame []byte) []byte {
 		if st.reply != nil {
 			st.reply.Write(imq.EncodeFrame(imq.G2cResult, imq.Result(m.OpID, 0)))
 		}
-		return nil
+		return keepalive()
 	}
 	if bytes.Equal(out, m.Message) {
 		return frame
@@ -293,6 +314,11 @@ func (st *stream) filtered(f imq.Frame, frame []byte) []byte {
 	return imq.EncodeFrame(imq.C2gSendMessage, m.Marshal())
 }
 
+// keepalive is what goes to the gateway in place of a frame the proxy answered itself: a ping. The client doesn't
+// ping while it's sending, so without it the gateway sees an idle connection and closes it (in a hosted room, where
+// everything the client sends is answered here).
+func keepalive() []byte { return imq.EncodeFrame(imq.C2gPing, nil) }
+
 func (st *stream) summary() string {
 	if st.other {
 		return fmt.Sprintf("%s %dB", st.name, st.bytes)