[Freeswitch-dev] FS doesn't update rtp port when sdp changed in 200OK response for invite message.

Lei Tang lei.tlfly at gmail.com
Thu Dec 24 03:06:41 PST 2009

Merry Christmas everyone!

I'm using FS 1.0.5pre9, I think there is a bug in mod_sofia when SDP changed
in 200 OK response for INVITE message,

the scenario is :
A(FreeSwitch)                      B
      ------INVITE ------->
      <----100 Tring--------
      <----180 Ring --------   with sdp m=audio 55066 RTP/AVP 0 120  c=IN
      <----UPDATE -------    with sdp m=audio 45486 RTP/AVP 0 120  c=IN IP4
      -----200 OK  ------>     response for UPDATE message
      <---- 200 OK--------     response for INVITE message,  with sdp
m=audio 45486 RTP/AVP 0 120  c=IN IP4
      --------ACK --------->

The problem is, B changed the rtp port in UPDATE message and "200 OK"
response message, but FS didn't do update, so it still send and receive data
from port 55066.
I read the mod_sofia source code and debug log, I found that  when get 200OK
response ,mod_sofia should update rtp session when sdp information is
different of the the pre sdp received in 180 ring response,
I'm using proxy_media mode, and I think there is the same problem in normal

here is the outbound channel state change log
entering state [received][100]
entering state [calling][0]
entering state [proceeding][180]
entering state [proceeding][200]
entering state [completing][200]
entering state [ready][200]
entering state [completed][200]
entering state [ready][200]

The problem is in state [proceeding][200], The code is as follow:
sofia.c line 3876
                if (switch_channel_test_flag(channel, CF_PROXY_MEDIA)) {
                    if (sofia_glue_activate_rtp(tech_pvt, 0) !=
                        goto done;

Since the rtp session is initialized when 180 RING response received,
sofia_glue_activate_rtp will return SWITCH_STATUS_SUCCESS without change any
So, I think the code should be as follow

3876                 if (switch_channel_test_flag(channel, CF_PROXY_MEDIA))
3877                     if (tech_pvt->rtp_session &&

3878                         sofia_set_flag_locked(tech_pvt,
3879                         if (sofia_glue_tech_proxy_remote_addr(tech_pvt)
!= SWITCH_STATUS_SUCCESS || sofia_glue_activate_rtp(tec     h_pvt, 0) !=

3880                             sofia_clear_flag_locked(tech_pvt,
3881                             goto


3883                         sofia_clear_flag_locked(tech_pvt,

3885                         if (sofia_glue_activate_rtp(tech_pvt, 0) !=
3886                             goto



3889                 }

When get 200OK reponse and sdp is changed, we should update remote port and
set reinvite flag before call  sofia_glue_activate_rtp.

Because I'm not so familiy with sofia and mod_sofia's source code, this code
is only for PROXY MEDIA mode and doesn't check for codec changed.(in my
scenario, only the remote port and ip are changed).

Could some fs dev check this problem, and give a offical patch?

BTW, I guess maybe mod_sofia is just ignore UPDATE message too. (just ignore
it if I was wrong)

Best Regards
lei.tlfly at gmail.com
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