[Freeswitch-users] Problems with t38_gateway

[Steven Lam, KeenSystems B.V.]

Hi all,

I'm experimenting with the t38_gateway in mod_spandsp to build a gateway that fully supports "passive" T_38. My test config looks like this:

<extension name="test">
  <condition>
    <action application="set" data="fax_enable_t38=true"/>
    <action application="set" data="sip_execute_on_image=t38_gateway self nocng"/>
    <action application="bridge" data="{sip_execute_on_image='t38_gateway self nocng'}sofia/internal/1234 at hostB"/>
  </condition>
</extension>

This works perfectly when:
- the A-leg sends a T38 re-INVITE and the B-leg doesn't
or
- the A-leg doesn't send a T38 re-INVITE but the B-leg does
or
- nor the A-leg, nor the B-leg send a T38 re-INVITE

This does _NOT_ work when both the A-leg and the B-leg send a T38 re-INVITE, in this case the call is hangup.
A snipped from the logging on the cli after the second T38 re-INVITE is received shows:

2012-02-29 14:11:34.044702 [DEBUG] sofia.c:5526 Channel sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx entering state [received][100]
2012-02-29 14:11:34.044702 [DEBUG] sofia.c:5537 Remote SDP:
v=0
o=keen 1348795719 1348795720 IN IP4 xxx.xxx.xxx.xxx
s=Keen
c=IN IP4 xxx.xxx.xxx.xxx
t=0 0
m=image 4568 udptl t38
a=T38FaxVersion:0
a=T38MaxBitRate:14400
a=T38FaxRateManagement:transferredTCF
a=T38FaxMaxDatagram:849
a=T38FaxUdpEC:t38UDPFEC

EXECUTE sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx t38_gateway(self nocng)
2012-02-29 14:11:34.044702 [DEBUG] mod_spandsp_fax.c:1950 sofia/wan_in/anonymous at xxx.xxx.xxx.xxx starting gateway mode to sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx
2012-02-29 14:11:34.044702 [DEBUG] mod_spandsp_fax.c:1965 (sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx) State Change CS_CONSUME_MEDIA -> CS_RESET
2012-02-29 14:11:34.044702 [DEBUG] switch_core_session.c:1180 Send signal sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx [BREAK]
2012-02-29 14:11:34.044702 [DEBUG] mod_spandsp_fax.c:1968 (sofia/wan_in/anonymous at xxx.xxx.xxx.xxx) State Change CS_SOFT_EXECUTE -> CS_RESET
2012-02-29 14:11:34.044702 [DEBUG] switch_core_session.c:1180 Send signal sofia/wan_in/anonymous at xxx.xxx.xxx.xxx [BREAK]
2012-02-29 14:11:34.044702 [DEBUG] switch_core_session.c:729 Send signal sofia/wan_in/anonymous at xxx.xxx.xxx.xxx [BREAK]
2012-02-29 14:11:34.044702 [DEBUG] switch_channel.c:2848 (sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx) Callstate Change ACTIVE -> HANGUP
2012-02-29 14:11:34.044702 [DEBUG] switch_core_session.c:2285 sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx skip receive message [APPLICATION_EXEC_COMPLETE] (channel is hungup already)
2012-02-29 14:11:34.044702 [NOTICE] mod_spandsp_fax.c:1663 Hangup sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx [CS_RESET] [NORMAL_CLEARING]
2012-02-29 14:11:34.044702 [DEBUG] switch_channel.c:2871 Send signal sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx [KILL]
2012-02-29 14:11:34.044702 [DEBUG] switch_core_session.c:1180 Send signal sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx [BREAK]
2012-02-29 14:11:34.044702 [DEBUG] switch_channel.c:2848 (sofia/wan_in/anonymous at xxx.xxx.xxx.xxx) Callstate Change ACTIVE -> HANGUP
2012-02-29 14:11:34.044702 [NOTICE] mod_spandsp_fax.c:1671 Hangup sofia/wan_in/anonymous at xxx.xxx.xxx.xxx [CS_RESET] [NORMAL_CLEARING]
2012-02-29 14:11:34.044702 [DEBUG] mod_spandsp_fax.c:1858 sofia/wan_out/+3188xxx at xxx.xxx.xxx.xxx skip receive message [UNBRIDGE] (channel is hungup already)

Does anybody know what goes wrong here?

Steven