[asterisk-bugs] [JIRA] (ASTERISK-29989) app_dial, chan_dahdi: DIALSTATUS is inconsistent for busy

[N A (JIRA)]

N A created ASTERISK-29989:
------------------------------

             Summary: app_dial, chan_dahdi: DIALSTATUS is inconsistent for busy
                 Key: ASTERISK-29989
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-29989
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
          Components: Applications/app_dial
    Affects Versions: 18.6.0
         Environment: Debian
            Reporter: N A


When an endpoint or line is BUSY, we expect a DIALSTATUS of BUSY and HANGUPCAUSE of 17.

This is how it works with PJSIP, for example:

Dialing busy PJSIP endpoint:

{noformat}
[2022-03-27 10:54:51]   == Using SIP RTP Audio TOS bits 184
[2022-03-27 10:54:51]     -- Called PJSIP/ATAxOldGrandstream1
[2022-03-27 10:54:51]     -- Local/4002702595 at lines-pre-000000df;2 requested media update control 20, passing it to PJSIP/ATAxOldGrandstream1-0000002f
[2022-03-27 10:54:51]     -- Local/4002702595 at lines-pre-000000df;2 requested media update control 20, passing it to PJSIP/ATAxOldGrandstream1-0000002f
[2022-03-27 10:54:51]   == Everyone is busy/congested at this time (1:1/0/0)
[2022-03-27 10:54:51]     -- Executing [4002702595 at lines:3] NoOp("Local/4002702595 at lines-pre-000000df;2", "BUSY / 17") in new stack
{noformat}

However, that's not what happens if you dial a busy DAHDI line:

{noformat}
[Mar 27 05:50:50]     -- Executing [2 at ring:3] Dial("DAHDI/2-1", "DAHDI/2") in new stack
[Mar 27 05:50:50] DEBUG[1387][C-00000001]: app_dial.c:2299 dial_exec_full:  DAHDI/2-1: Data: DAHDI/2
[Mar 27 05:50:50] DEBUG[1387][C-00000001]: sig_analog.c:799 analog_available: analog_available 2
[Mar 27 05:50:50] WARNING[1387][C-00000001]: app_dial.c:2604 dial_exec_full: Unable to create channel of type 'DAHDI' (cause 17 - User busy)
[Mar 27 05:50:50]     -- No devices or endpoints to dial (technology/resource)
[Mar 27 05:50:50] DEBUG[1387][C-00000001]: app_dial.c:3363 dial_exec_full: Exiting with DIALSTATUS=CHANUNAVAIL.
[Mar 27 05:50:50] DEBUG[1387][C-00000001]: app_dial.c:3394 dial_exec_full:  DAHDI/2-1: Done
[Mar 27 05:50:50] DEBUG[1387][C-00000001]: pbx.c:2938 pbx_extension_helper: Launching 'NoOp'
[Mar 27 05:50:50]     -- Executing [2 at ring:4] NoOp("DAHDI/2-1", "CHANUNAVAIL / 17") in new stack
{noformat}

This is because ast_request_with_stream_topology is returning NULL, and this would succeed with other channel drivers, presumably, because Asterisk doesn't "know" if a line is busy or not until it actually tries dialing it. However, with DAHDI, it knows immediately, before we even try, so it's returning NULL here.

It's a little unclear what the appropriate fix here is. Code could be added to detect a hang up case of 17 and, if that's the case, NOT set it to CHANUNAVAIL but busy instead, right about here: https://github.com/asterisk/asterisk/blob/master/apps/app_dial.c#L2823

That would fix the problem, but not sure if that would be considered too "hacky".

Alternately, we tell everyone that using DIALSTATUS is wrong and should not be relied on, and they need to case on the HANGUPCAUSE instead... but I think the DIALSTATUS should be fixed to match the HANGUPCAUSE.

Thoughts anyone?



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