[SR-Users] Websockets WSS problem with NOTIFY

[Pete Kelly]

Hi Peter, thanks for that info.

It looks like all the packets marked Websocket in Wireshark are coming
across OK from Kamailio. The first nibble is always 1000 as expected.

However I notice now that whenever a NOTIFY is sent out from Kamailio the
packet is *not* a Websocket packet, it's identified as HTTP within
Wireshark and does not contain the 4 "header" bytes that Websocket packets
seem to contain.

As a result the first byte for the NOTIFY is the letter 'N' represented as
01001110.

So the browser could be reading the second bit as 1, and interpreting that
as meaning the compressed bit set to 1.

Does that sound plausible?


On 24 January 2013 14:54, Peter Dunkley <peter.dunkley at crocodile-rcs.com>wrote:

> The RSV1 bit (which is the compressed bit) should be the second bit from
> the left in the WebSocket frame.  The first bit is the FIN (should always
> be one here), then you have RSV1, RSV2, and RSV3, and the last nibble of
> the first byte will be the opcode.
>
> Regards,
>
> Peter
>
>
> On 24 Jan 2013, at 14:47, Pete Kelly <pkelly at gmail.com> wrote:
>
> Chrome 26, 24 and Firefox nightly all exhibit the same behaviour.
>
> I've decrypted the packets in wireshark, could you point me at what I am
> looking for to see the compressed bit?
>
> Wireshark reports (on what seems to be the problematic frame) "This frame
> ACKs a segment we have not seen"
>
>
> On 24 January 2013 13:50, Peter Dunkley <peter.dunkley at crocodile-rcs.com>wrote:
>
>> **
>> Have you checked to see if there are any known bugs in the browser you
>> are using?
>>
>> As the WebSocket message compression stuff is still draft the browser
>> implementation probably won't be complete or fully tested yet.
>>
>> As I said, the Kamailio WebSocket implementation does not support any
>> extensions and all the reserved bits are 0'd.  So I don't think it is
>> likely that the compressed bit is set to 1 at all.
>>
>> The only other thing I can suggest is capturing your TLS traffic with
>> WireShark and importing the certificates into it so you can decode the
>> packets.  At that point you should be able to look at the binary of the
>> frame and see if the compressed bit is set or not.
>>
>> Regards,
>>
>> Peter
>>
>>
>> On Thu, 2013-01-24 at 13:45 +0000, Pete Kelly wrote:
>>
>> Hi Peter
>>
>>
>>
>>  I can confirm it works correctly for WS and not WSS, and it appears to
>> be only the NOTIFY request in the direction of Kamailio > UAC. INVITE
>> requests in the direction of Kamailio > UAC are fine.
>>
>>
>>
>>  I've tried it with the tls tls_disable_compression flag set to both 0
>> and 1
>>
>>
>>
>>  Pete
>>
>>
>>
>>  On 24 January 2013 09:53, Peter Dunkley <peter.dunkley at crocodile-rcs.com>
>> wrote:
>>
>>  Hi,
>>
>> I've done some checking online and in the code.  The compressed bit is
>> defined in draft-ietf-hybi-permessage-compression and uses the RSV1 bit
>> from the WebSocket frame header.  As per RFC 6455 the Kamailio WebSocket
>> implementation is careful to leave RSV1, RSV2, and RSV3 with values of 0.
>>
>> As this part of the code is identical for WS and WSS connections can you
>> confirm that it works correctly for WS?
>>
>> Regards,
>>
>> Peter
>>
>>
>>
>> On Thu, 2013-01-24 at 09:09 +0000, Peter Dunkley wrote:
>>
>> I shod also add that the Kamailio WebSocket implementation does not
>> support any extensions.  So unless the deflate frame extension is implicit
>> for TLS it will not be negotiated.  Further, the implementation does not
>> set any compressed bits and all unused flags etc should be zeroed
>> automatically - but I will look at the code later.
>>
>>
>> Peter
>>
>> On 24 Jan 2013, at 09:05, Peter Dunkley <peter.dunkley at crocodile-rcs.com>
>> wrote:
>>
>>
>>  I am not sure how to investigate this.  It sounds like it might be a TLS
>> related problem (or a WebSocket/TLS interworking problem in Kamailio).  I
>> don't know anything about the Kamailio TLS implementation - I just drop
>> WebSocket frames into it as required.
>>
>>
>> I did do (a little) WSS testing and saw no problems myself.
>>
>>
>> Regards,
>>
>>
>> Peter
>>
>> On 23 Jan 2013, at 22:12, Pete Kelly <pkelly at gmail.com> wrote:
>>
>>
>>  Hi, I am having an issue at the moment with SIP NOTIFY messages being
>> sent from Kamailio (latest git master) over wss transport
>>
>> I am getting reports from the receiving end saying "Compressed bit must
>> be 0 if no negotiated deflate-frame extension"
>>
>> The only reference I can find to it is at the following URL... where the
>> problem was caused by the server miscalculating the size of the msg:
>> http://stackoverflow.com/questions/12308728/compressed-bit-must-be-0-when-sending-a-message-to-websocket-client
>>
>> Does anyone have any suggestions as to how I could debug this within
>> Kamailio? It sounds like Kamailio may be sending some incorrect packet
>> information but I am unsure at this point.
>>
>>
>>
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>>
>>
>>     --
>> Peter Dunkley
>> Technical Director
>> Crocodile RCS Ltd
>>
>>
>>
>>
>>   --
>> Peter Dunkley
>> Technical Director
>> Crocodile RCS Ltd
>>
>>
>
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