[asterisk-bugs] [JIRA] (ASTERISK-20638) SIP dialog matching is incorrect when multiple provisional responses are received with pedantic SIP checking

[Joshua Colp (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-20638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=199834#comment-199834 ] 

Joshua Colp commented on ASTERISK-20638:
----------------------------------------

While not proper according to the RFC this *should* be okay on 1.8. With a normal SIP stack there would be multiple SIP dialogs and stuff would match properly, unlike chan_sip where there is only one and it doesn't.

Where I think this will fall apart is on Asterisk 10 and higher, where additional stuff was put in to more properly handle forking. I've done reading of the code there but am rather uncertain as to what will actually happen. Would it be possible for you to quickly lab that up in your setup to tell me and provide the logs? If not - no worries, I'll spend time to put together everything needed next week.
                
> SIP dialog matching is incorrect when multiple provisional responses are received with pedantic SIP checking
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: ASTERISK-20638
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-20638
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/Interoperability
>    Affects Versions: 1.8.17.0
>            Reporter: Eelco Brolman
>            Assignee: Eelco Brolman
>         Attachments: pedantic-call-pickup-from-tag.patch
>
>
> When an external call pickup (INVITE with Replaces: header) is sent to asterisk, asterisk tries to find the call ({{get_sip_pvt_byid_locked}}) based on the {{callid}}, {{fromtag}} and {{totag}} in pedantic mode.
> The match will fail in certain situations since the fromtag is not definite (final) as long as only Provisional responses have been received.
> When asterisk dials a SIP proxy which does ring group dialing for instance, multiple {{180 Ringing}} responses will be received, and the dialog within asterisk cannot be matched against a single fromtag.
> So as long as only provisional responses are received (i.e. when flag {{SIP_PAGE2_DIALOG_ESTABLISHED}} is not set), asterisk should not reject the match based on the fromtag.
> The patch for this specific situation is easy of course, you need to test if the dialog is established when checking the fromtag:
> {code}
> if ((frommismatch && ast_test_flag(&sip_pvt_ptr->flags[1], SIP_PAGE2_DIALOG_ESTABLISHED)) || tomismatch) {
> {code}
> but I don't know if this breaks other checks.

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