Re: [Linphone-users] SRTP encrypted calls error

[Guillaume BERAUDO]

Hi Liviu,


Linphone invites the remote part with SRTP information:
m=audio 7078 RTP/SAVP 110 111 112 3 8 0 101
a=crypto:1 AES_CM_128_HMAC_SHA1_80 
inline:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
a=crypto:2 AES_CM_128_HMAC_SHA1_32 
inline:YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY

But the answer sent by the iptel Sip Express Media Server doesn't contain
SRTP information:
m=audio 10576 RTP/AVP 110 3 8 0 101


That is why the call fails.

The behaviour expected by Linphone is that the remote part refuse call if it
cannot handle SRTP. Then Linphone would try a non encrypted invite.

Right now, your only solution is to disable SRTP.
On the Linphone side, I will update the "no codec intersection" UI error message
to a more general one.


Cheers,

Guillaume



RFC 4568 - 5.1.2: 
   When the answerer receives the initial offer with one or more crypto
   attributes for a given unicast media stream, the answerer MUST either
   accept exactly one of the offered crypto attributes, or the offered
   stream MUST be rejected.



> >> Dear all
> >> Is it normal that when I'm selecting 'SRTP' encryption and making a
> >> call to, say, <sip:address@hidden>, I get the following error:
> >> "No codec intersection"
> >>
> >> I find the following message in teh log:
> >> "error: Incompatible SDP offer received in 200Ok, need to abort the
> >> call".
> >>
> >> Using Linphone 3.5.0 on Ubuntu Lucid, compiled against
> >> 'srtp-1.4.4'.