[Asterisk-code-review] bridges/bridge t38: Add a bridging module for managing T.38 ... (asterisk[13])

[Matt Jordan]

Matt Jordan has posted comments on this change.

Change subject: bridges/bridge_t38: Add a bridging module for managing T.38 state
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Patch Set 3:

> (1 comment)

When a channel receives an offer for T.38, it will transition into the negotiating state. (This will trigger a bridge reconfiguration.) At that moment, we have to be ready for the T.38 negotiation to fail - a CANCEL request could come in, someone could hang up the channel, etc.

The goal of the bridge is to make sure we get that cancellation information over to the other side of the bridge so that the channel can re-negotiate itself back.

So, say we have the following. We start off in audio:

   PJSIP/Alice    <=>    PJSIP/Bob
      Audio               Audio

And then Alice receives a T.38 offer:

   PJSIP/Alice    <=>    PJSIP/Bob
 T.38 Negotiating         Audio

At this point, a frame should be queued up from Alice to Bob to cause him to start his negotiation. That would change us to this state:

   PJSIP/Alice    <=>    PJSIP/Bob
 T.38 Negotiating       T.38 Negotiating

If we don't immediately switch to the T.38 bridge, we can't guarantee that if Alice leaves, Bob will be switched back to audio. That can leave Bob in a state where he's ejected from the dialplan, has no audio, and his far end send back a 200 OK for the T.38 session.

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Gerrit-MessageType: comment
Gerrit-Change-Id: If5b0bb478eb01c4607c9f4a7fc17c7957d260ea0
Gerrit-PatchSet: 3
Gerrit-Project: asterisk
Gerrit-Branch: 13
Gerrit-Owner: Matt Jordan <mjordan at digium.com>
Gerrit-Reviewer: Anonymous Coward #1000019
Gerrit-Reviewer: Joshua Colp <jcolp at digium.com>
Gerrit-Reviewer: Matt Jordan <mjordan at digium.com>
Gerrit-Reviewer: Richard Mudgett <rmudgett at digium.com>
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