Invalid RSV bits regardless of compression mode

[ZackaryWelch]

When reading from a websocket client (specifically the python package websocket), I get an error from the websocket connection's read:

failed to read: WebSocket closed: received header with unexpected rsv bits set: true:false:true

This is from an accepted connection with compression disabled. When I set compression to NoContextTakeover, I get the following:

failed to read: WebSocket closed: received header with unexpected rsv bits set: false:false:true

Finally, when compression is set to ContextTakeover:

failed to read: WebSocket closed: sent close frame: status = StatusPolicyViolation and reason = "unexpected data message"

It should be noted the client does not support permessage-deflate. I'm not sure why RSV1 is enabled when compression is disabled, and then disabled when it is enabled. I also do not know why RSV3 is set. The client does not support any RSV bits, and it is clear from source that this library does not support RSV2 or RSV3 at all,l and RSV1 only if compression is enabled.

These bits may also be misread garbage, As I've also seen "false:true:false", which would explain why the settings do not make sense.

[ZackaryWelch]

Seems related to: #337

[nhooyr]

@ZackaryWelch Were you able to continue reproducing? #337 seems to have been user error.

[verbumfeit]

@nhooyr I can reproduce the error with htmx as the client.

received header with unexpected rsv bits set: true:false:false

I would be happy to help debug, but I have no clue yet where to start.

[nhooyr]

That's concerning. What version of the library are you using? Is it consistently reproducible?