[asterisk-users] PJSIP: how to retrieve underlying SIP Call-ID

[Matthew Jordan]

On Tue, Oct 6, 2015 at 3:25 PM, Michael Ulitskiy <mulitskiy at acedsl.com> wrote:
> Hello,
>
>
>
> I've started to play with PJSIP and got stuck at the following problem.
>
> I need to retrieve SIP Call-ID associated with PJSIP channel.
>
> For inbound channel I can use ${PJSIP_HEADER(read,Call-ID)}, but that
> doesn't work for
>
> outbound channel even in pre-dial or hangup handler. Whatever I do
> PJSIP_HEADER
>
> seem to be unable to read headers for outbound channel.
>
>
>
> Here's what I do:
>
>
>
> [xyz]
>
> exten => 999,1,NoOp(Call-ID: ${PJSIP_HEADER(read,Call-ID)})
>
> same =>
> n,Dial(PJSIP/xyz011101/sip:xyz011101@<outbound_proxy>:5060,30,b(_pre_dial,s,1))
>
> exten => h,1,NoOp()
>
>
>
> [_pre_dial]
>
> exten => s,1,NoOp(Call-ID: ${PJSIP_HEADER(read,Call-ID)})
>
> same => n,Set(CHANNEL(hangup_handler_push)=_hangup,s,1())
>
> same => n,Return
>
>
>
> [_hangup]
>
> exten => s,1,NoOp(Call-ID: ${PJSIP_HEADER(read,Call-ID)})
>
> same => n,Return
>
>
>
>
>
> Here's the result:
>
> -- Executing [999 at xyz:1] NoOp("PJSIP/poly_650_2_01-0000006f", "Call-ID:
> e3e249e5-7e8941dd-da386565 at 192.168.100.238") in new stack
>
> -- Executing [999 at xyz:2] Dial("PJSIP/poly_650_2_01-0000006f",
> "PJSIP/xyz011101/sip:xyz011101@<outbound_proxy>:5060,30,b(_pre_dial,s,1)")
> in new stack
>
> -- PJSIP/xyz011101-00000070 Internal Gosub(_pre_dial,s,1) start
>
> -- Executing [s at _pre_dial:1] NoOp("PJSIP/xyz011101-00000070", "Call-ID: ")
> in new stack
>
> -- Executing [s at _pre_dial:2] Set("PJSIP/xyz011101-00000070",
> "CHANNEL(hangup_handler_push)=_hangup,s,1()") in new stack
>
> -- Executing [s at _pre_dial:3] Return("PJSIP/xyz011101-00000070", "") in new
> stack
>
> == Spawn extension (xyz, 999, 1) exited non-zero on
> 'PJSIP/xyz011101-00000070'
>
> -- PJSIP/xyz011101-00000070 Internal Gosub(_pre_dial,s,1) complete
> GOSUB_RETVAL=
>
> -- Called PJSIP/xyz011101/sip:xyz011101@<outbound_proxy>:5060
>
> == Using SIP RTP Audio TOS bits 184
>
> -- PJSIP/xyz011101-00000070 is ringing
>
> -- PJSIP/xyz011101-00000070 Internal Gosub(_hangup,s,1) start
>
> -- Executing [s at _hangup:1] NoOp("PJSIP/xyz011101-00000070", "Call-ID: ") in
> new stack
>
> -- Executing [s at _hangup:2] Return("PJSIP/xyz011101-00000070", "") in new
> stack
>
> == Spawn extension (xyz, 999, 1) exited non-zero on
> 'PJSIP/xyz011101-00000070'
>
> -- PJSIP/xyz011101-00000070 Internal Gosub(_hangup,s,1) complete
> GOSUB_RETVAL=
>
> == Spawn extension (xyz, 999, 2) exited non-zero on
> 'PJSIP/poly_650_2_01-0000006f'
>
> -- Executing [h at xyz:1] NoOp("PJSIP/poly_650_2_01-0000006f", "") in new stack
>
>
>
> As you can see I can get Call-ID of inbound channel, but I receive null for
> the outbound channel in both pre-dial and hangup handlers.
>
>
>
> So my question is if there's a way to retrieve SIP Call-ID for outbound
> channels?
>
> Also the 2nd question is if PJSIP_HEADER is supposed to be able to read
> headers of the outbound channel?
>

Hi Michael -

While you can use PJSIP_HEADER, the ability to retrieve the SIP
Call-ID through the CHANNEL function on a PJSIP channel was actually
just added in 13.6.0, and should be in the latest RC (13.6.0-rc2 [2]).

In either case, you're using a function as opposed to some
application, which means you do need to call the functions on the
specific channel. To get access to the outbound channel, you can use a
pre-dial handler's 'b' option [3]. The Call-ID *should* be set up on
the underlying invite session in the PJSIP dialog, even though it
hasn't been transmitted yet.

Matt

[1] https://gerrit.asterisk.org/#/c/1204/
[2] http://downloads.asterisk.org/pub/telephony/asterisk/ChangeLog-13.6.0-rc2
[3] https://wiki.asterisk.org/wiki/display/AST/Pre-Dial+Handlers

-- 
Matthew Jordan
Digium, Inc. | Director of Technology
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org