Pong response contains a mask

[anisimovsergey]

Pong response to my ping requests contains a mask and overall it looks like this "8a 80 00 00 00 00". I'm not entirely sure if sending a mask without data is a valid case.

[Links2004]

from the RFC:

In the WebSocket Protocol, data is transmitted using a sequence of
frames. To avoid confusing network intermediaries (such as
intercepting proxies) and for security reasons that are further
discussed in Section 10.3, a client MUST mask all frames that it
sends to the server (see Section 5.3 for further details). (Note
that masking is done whether or not the WebSocket Protocol is running
over TLS.) The server MUST close the connection upon receiving a
frame that is not masked.

hopes that answer the question.

[anisimovsergey]

Thank you for your prompt response.
It does seem like it's a problem is the client I'm trying to use. It closes connection upon receiving a pong with a mask. What is strange though, that this is a quite popular WebSocktets client library (~3000 stars on github) and claims to be conformant with the Autobahn test suite. Anyhow, I'm closing this one.

[anisimovsergey]

Finally I got some time to go through the RFC and that what it is saying in section Section 5.3

A server MUST NOT mask any frames that it sends to
   the client.  A client MUST close a connection if it detects a masked
   frame. 

PONG should not be masked since it is sent from a server to a client.

[Links2004]

missed your response, will look in to this.
may need some restructuring to handle this cases.

[Gl0ntz]

Connection being dropped by the client running on an Android Device with Reason="A frame from the server is masked". Is there a solution to this?

[Links2004]

as a workaround you can remove this line:
https://github.com/Links2004/arduinoWebSockets/blob/master/src/WebSocketsServer.cpp#L862
and change the true to false here:
https://github.com/Links2004/arduinoWebSockets/blob/master/src/WebSockets.cpp#L437

Note:
this will break the client implementation, since it will not be masked there any more.

[sanketplus]

any plans to fix this? @Links2004

One approach I have in mind is to introduce a isServer field in WSClient_t and use it in sendFrame on line #L197 to check if it is server, and skip.

If you think this is a good way to approach, happy to open a PR :)

[Links2004]

sounds good, a PR is welcome.
the fix for this got lost on my Todo list some how...

I think with the isServer change it we can remove the mask parameter all together form the function.
since sendFrame is a internal function it will not change the external API.