Re: [Linphone-developers] patch to fix ZRTP sequence number handling

[Guillaume Beraudo]

Hi Eli,

Thanks for the information.
I think we will integrate the patch, though it seems to me very strange to
receive chaotical sequence numbers.


Why are you using such a strange zrtp stack as Groundwire's?


Cheers,

Guillaume

On Tue, Apr 30, 2013 at 12:46:12PM -0400, Eli Burke wrote:
> Attached is a patch to oRTP that fixes incorrect handling of ZRTP sequence 
> numbers. We encountered a consistent error when connecting between Linphone 
> and Groundwire using ZRTP (note: compatibility with Groundwire requires my 
> previously submitted zrtp-hash patch). 
> 
> Bug details: Linphone sends ZrtpHello and receives Groundwire's ZrtpHelloAck, 
> followed by ZrtpHello with a lower sequence number. This packet gets dropped 
> with the error "Discarding received out of order zrtp packet:..." and 
> Linphone never completes the ZRTP handshake. 
> 
> Though you may conclude that Groundwire is misbehaving, it is in fact in 
> compliance with the RFC, which simply says:
> > The Sequence Number is a count that is incremented for each ZRTP
> >    packet sent.  The count is initialized to a random value.  This is
> >    useful in estimating ZRTP packet loss and also detecting when ZRTP
> >    packets arrive out of sequence.
> 
> http://tools.ietf.org/html/rfc6189#section-5
> 
> I have confirmed with Werner Dittmann (author of ZrtpCpp) that the sequence 
> number is only intended for diagnostic purposes and not for enforcing any 
> kind of packet ordering. 
> 

> _______________________________________________
> Linphone-developers mailing list
> address@hidden
> https://lists.nongnu.org/mailman/listinfo/linphone-developers

signature.asc
Description: Digital signature