Asterisk is crashing on receiving fax (SpanDSP 3.0, Asterisk 20.9)

[aneessadeek]

I’m new to setting up fax functionality and am trying to send faxes from one Asterisk instance to another using T.38. I’ve installed FreeSWITCH/SpanDSP 3.0.0 and configured Asterisk 20.9.3 for fax handling.

However, I’m encountering an issue: Asterisk crashes during fax transmission without showing any errors. Interestingly, if I disable T.38, the fax gets sent to the server successfully, but both Asterisk instances crash after the transmission is completed.

Could this issue be related to the SpanDSP version? If so, which SpanDSP version is stable and recommended for setting up T.38 fax transactions?

[aneessadeek]

Can anybody confirm atleast the Asterisk configurations are correct.

Using the same config in both the servers

pjsip.conf
[general]

[transport-udp-nat]
type=transport
protocol=udp
bind=0.0.0.0

[transport-tcp]
type = transport
protocol=tcp
bind=0.0.0.0

[fax_poc]
type=endpoint
auth=fax_poc
outbound_auth=fax_poc
context=fax-context
disallow=all
allow=ulaw,alaw,t38
aors=fax_poc
fax_detect=yes
t38_udptl=yes
t38_udptl_ec=redundancy
t38_udptl_maxdatagram=400

[fax_poc]
type=auth
auth_type=userpass
password=XX
username=fax_poc

[fax_poc]
type=aor
contact=sip:XXXXX

[fax_poc]
type=identify
endpoint=fax_poc
match=XXXXX

extension.conf
[fax-context]
exten => fax,1,NoOp(Detected fax hureeeeee)
same => n,ReceiveFAX(/var/spool/asterisk/fax/${UNIQUEID}.tif)
same => n,Hangup
exten => _+X.,1,Verbose(Call from ${CALLERID(num)} to ${EXTEN})
same => n,Answer()
same => n,Ringing()
same => n,Wait(5)
same => n,Playback(demo-congrats)
same => n,Hangup
[send-fax]
exten => s,1,Verbose(Sending fax!)
same => n,Answer
same => n,SendFax(/var/spool/asterisk/fax/obcallerid.tiff,fd)
same => n,Hangup

cli command
channel originate PJSIP/+1234@fax_poc extension s@send-fax

[jcolp]

There is insufficient information. If a crash occurs then a backtrace would be required[1] to see where the crash happened.

[1] Getting a Backtrace - Asterisk Documentation

[aneessadeek]

Apologies, I modified the spandsp package before capturing the trace as I wasn’t familiar with the process. After switching from freeswitch/spandsp 3.0 to soft-switch/spandsp 0.0.6, fax is now working fine with both G711 and T38 formats.