[asterisk-dev] Adding Required header to OK response will fail.

[Mark Michelson]

On 11/13/2014 12:34 PM, Dave WOOLLEY wrote:
>
> I don’t believe that the code that adds Required: timers to a 200 OK 
> response will work, even in Asterisk 13, current branch version.
>
> In my back port, it produces an error saying headers cannot be added 
> after lines have been added. The same conditions for this seem to 
> apply in version 13:
>
> In add_header:
>
> if (req->lines) {
>
> ast_log(LOG_WARNING, "Can't add more headers when lines have been 
> added\n");
>
> return -1;
>
> }
>
> In transmit_response_with_sdp:
>
> if (p->rtp) {
>
> ...
>
> if (p->t38.state == T38_ENABLED) {
>
> add_sdp(&resp, p, oldsdp, TRUE, TRUE);
>
> } else {
>
> add_sdp(&resp, p, oldsdp, TRUE, FALSE);
>
> }
>
> } else
>
> ast_log(LOG_ERROR, "Can't add SDP to response, since we have no RTP 
> session allocated. Call-ID %s\n", p->callid);
>
> if (reliable && !p->pendinginvite)
>
> p->pendinginvite = seqno;             /* Buggy clients sends ACK on 
> RINGING too */
>
> add_required_respheader(&resp);
>
> Note that SDP is added, and therefore “req->lines” becomes non-zero, 
> as the response now has a body, before add_required_respheader is called.
>
> In add_required_respheader:
>
>          if (ast_str_strlen(str) > 0) {
>                 add_header(req, "Require", ast_str_buffer(str));
>          }
>
> For information, the test setup for this was two Asterisk instances in 
> tandem.  The first one uses session-timers=originate.  The second one 
> uses sendrpid=true, session-timers=accept and session-refresher=uas.  
> The dialplan (after a delay) sets the connected line, to force a 
> re-invite against the call setup direction (then goes into a long 
> wait).  As the first Asterisk is UAS for the re-invite, but is in 
> session timer originate mode, it is forced to use Require. The test 
> was trying to confirm that session timer role reversals worked.
>
>
> BTS Holdings PLC - Registered office: BTS House, Manor Road, 
> Wallington, SM6 0DD - Registered in England: 1517630
>
>

Agreed that this looks like a bug. Probably should be doing the 
add_required_respheader() call before adding the SDP.
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