tree a73b904cc39e4688a3f236a169fc0766bc31f10b
parent d4b087c6cf50f1843200b1514d20dfc23c7b81cc
author Taylor Brandstetter <deadbeef@webrtc.org> 1627000915 -0700
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> 1627078080 +0000

Fix bug where we assume new m= sections will always be bundled.

A recent change [1] assumes that all new m= sections will share the
first BUNDLE group (if one already exists), which avoids generating
ICE candidates that are ultimately unnecessary. This is fine for JSEP
endpoints, but it breaks the following scenarios for non-JSEP endpoints:

* Remote offer adding a new m= section that's not part of any BUNDLE
  group.
* Remote offer adding an m= section to the second BUNDLE group.

The latter is specifically problematic for any application that wants
to bundle all audio streams in one group and all video streams in
another group when using Unified Plan SDP, to replicate the behavior of
using Plan B without bundling. It may try to add a video stream only
for WebRTC to bundle it with audio.

This is fixed by doing some minor re-factoring, having BundleManager
update the bundle groups at offer time.

Also:
* Added some additional validation for multiple bundle groups in a
  subsequent offer, since that now becomes relevant.
* Improved rollback support, because now rolling back an offer may need
  to not only remove mid->transport mappings but alter them.

[1]: https://webrtc-review.googlesource.com/c/src/+/221601

Bug: webrtc:12906, webrtc:12999
Change-Id: I4c6e7020c0be33a782d3608dee88e4e2fceb1be1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/225642
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Taylor Brandstetter <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34544}