chan_sip.c: Fax detected but no fax extension

I’m trying to set up incoming faxing with Asterisk, FreePBX 1.8.x and

Typical scenario:

  1. Mr. Somebody called an operator (at example - local 2345555)
  2. Operator acceped the call
  3. They are talking about some documentary questions and then mr. Somebody stated: “OK, please catch the fax”
  4. Mr. Somebody pressed SEND button on his analog fax
  5. Operator received the paper.
  6. They have a voice conversation again.

Note that there is no special fax DID and fax transfer started just in middle of voice call.

But if a voice conversation alresdy started, Asterisk just hangs up when mr. Somebody have pressed SEND. Log message is “chan_sip.c: Fax detected but no fax extension”.

Incoming route for 234555
Detect Faxes: yes
Fax Destination: Fax Recipient / Operator (1555)

Extension 1555
Fax Enabled
Fax Email: [email protected]

I’ve checked that [ext-did-000x] generated OK, app-fax and so on is there.

But “Fax detected but no fax extension”.

After some digging in chan_sip source I’ve figured that chan_sip looked up extension ‘fax’ in latest macro context:

const char *target_context = S_OR(chan->macrocontext, chan->context);

And of course [macro-dial-one] that fired when voice conversation started doesn’t include any fax extensions.

How can I fix this?

Is the right way adding to extensions_custom.conf these lines?

exten => fax,1,Goto(${CUT(FAX_DEST,^,1)},${CUT(FAX_DEST,^,2)},${CUT(FAX_DEST,^,3)})

i have same problem

exten => fax,1,Goto(${CUT(FAX_DEST,^,1)},${CUT(FAX_DEST,^,2)},${CUT(FAX_DEST,^,3)})
in extensions_custom.conf does not help

any other idea?