I have this problem with compression, and I am not sure if it is a bug. My WebSocket server does not support context takeover, and I am having problems sending messages, but not receiving.
The browser issues a request like this:
GET /socket HTTP/1.1
Host: thirdparty.com
Origin: http://example.com
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Version: 13
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits, x-webkit-deflate-frame
If the server does not specify any option about context takeover:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Access-Control-Allow-Origin: http://example.com
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Extensions: permessage-deflate
I can read and write the first message, but cannot do subsequent reads or writes, because Chrome expects the server is keeping the context.
So my server provides this answer:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Access-Control-Allow-Origin: http://example.com
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=
Sec-WebSocket-Extensions: permessage-deflate; client_no_context_takeover; server_no_context_takeover
And now I can receive messages without problems, but again, I can only send the first message, the second message fails, and I see an error in Chrome saying that it failed at inflating the frame. I tried to send two identical strings, and I can see how the server is sending twice the same data, but the client fails to decompress it the second time.
So it seems that Chrome accepts the client_no_context_takeover
parameter that specify that the client won't use the same compression context for all messages when compressing, but ignores server_no_context_takeover
indicates the server won't use the same context.
Is this a bug in Chrome? I am not clear about if I can send options back that have not been offered/requested by the client.
Is there any other option I can use to disable the client context takeover?
UPDATE:
In WebSocketPerMessageDeflate.cpp in the Chromium source code, I can see:
if (clientNoContextTakeover != parameters.end()) {
if (!clientNoContextTakeover->value.isNull()) {
m_failureReason = "Received invalid client_no_context_takeover parameter";
return false;
}
mode = WebSocketDeflater::DoNotTakeOverContext;
++numProcessedParameters;
}
But also:
if (serverNoContextTakeover != parameters.end()) {
if (!serverNoContextTakeover->value.isNull()) {
m_failureReason = "Received invalid server_no_context_takeover parameter";
return false;
}
++numProcessedParameters;
}
In the first snippet, it is setting the "mode" variable, but in the second one is not doing nothing, so it seems it is basically ignoring the parameter.
Cheers.