tree cd9c975fb54665236daf367f7453bac0e6bb4739
parent 4e18a1fff3b34e2fab4c8f3e1fc2402716b54117
author Victor Boivie <boivie@webrtc.org> 1625855091 +0200
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> 1626130071 +0000

dcsctp: Abandon chunks consistently

The previous logic to abandon chunks when partial reliability was used
was a bit too eager and trigger happy.

 * Chunks with limited retransmissions should only be abandoned when a
   chunk is really considered lost. It should follow the same rules as
   for retransmitting chunks - that it must be nacked three times or
   due to a T3-RTX expiration. Before this change, a single SACK not
   referencing it would be enough to abandon it. This resulted in a lot
   of unnecessary sent FORWARD-TSN and undelivered messages - especially
   if running with zero retransmissions.

   The logic to expire chunks by limited retransmissions will now only
   be applied when a chunk is actually nacked.

 * The second partial reliability trigger - expiration time - wasn't
   evaluated when producing a middle chunk of a larger message.

A number of test cases were added and updated as chunks will now be
abandoned immediately instead of first scheduled for retransmission and
later abandoned.

Bug: webrtc:12961
Change-Id: I0ae17b2672568bdbdc32073a99d4c24b09ff5fe9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/225548
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34458}