WebSocket: message handler sometimes called with null data (potentially issue in frame processing)

[farwayer]

Bug Description

I’ll say right away that the bug is floating and I don’t have a ready-made recipe for reproducing it. The bug usually appeared during debugging. Apparently, timings and the sequence of data arrival are important. The server should also send pings to get this effect.

From the screenshot you can see that the websocketMessageReceived function is called with this.#info.originalOpcode=9 (PING frame type), which should not happen.

Logs & Screenshots

Environment

node v21.6.2

[KhafraDev]

does this only occur during debugging?

[farwayer]

Yes, I only encountered this error in debugging. But, I assume that the problem is not related to it, but to the timings. Before null in the message handler received, two breakpoints are triggered. But if you send a ping from the server with a little delay (calling process.hrtime() before sending is enough), then everything goes fine.

[KhafraDev]

Maybe, I think there's definitely room for improvement in parsing control frames (frames that can't be fragmented). I'll look into it but no promises.

[LubosD]

FWIW, I definitely encountered this bug outside of debugging. The WebSocket would receive messages correctly for a while and then it would always give me nulls.