[asterisk-bugs] [JIRA] (ASTERISK-29014) res_pjsip_session: Re-INVITE collisions aren't handled correctly

[Joshua C. Colp (JIRA)]

    [ https://issues.asterisk.org/jira/browse/ASTERISK-29014?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=251688#comment-251688 ] 

Joshua C. Colp edited comment on ASTERISK-29014 at 8/18/20 12:44 PM:
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The pending media state being empty is due to the T.38 implementation. For session refresh it is not empty. If this change results in changes there then that'd be nice, but it is not a fix focused on that.


was (Author: jcolp):
The pending media state being empty is due to the T.38 implementation. For session refresh it is not empty.

> res_pjsip_session: Re-INVITE collisions aren't handled correctly
> ----------------------------------------------------------------
>
>                 Key: ASTERISK-29014
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-29014
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Resources/res_pjsip_session
>    Affects Versions: 13.35.0, GIT, 16.12.0, 17.6.0
>            Reporter: George Joseph
>            Assignee: George Joseph
>
> When both Asterisk and a UA send re-invites at the same time, both send 491 "Transaction in progress" responses to each other and back off a specified amount of time before retrying.   When Asterisk prepared to send its re-invite, it set up the session's pending media state with the new topology it wanted, then sent the re-invite.  When it received the re-invite from the UA, it partially processed the media in the re-invite and reset the pending media state _before_ sending the 491 losing the state it set in _its_ re-invite.   When the backoff timer expires and Asterisk it re-sends the re-invite it originally sent, the pending media state is empty and the re-invite's sdp shows the streams as dropped.
> Asterisk needs to do 2 things...
> * Respond with a 491 _before_ making any changes to the session and media state.
> * Save the media state when it queues the retry.



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