commit 9700d88b1ae9406410c42c244cd7f7aedfec15dd
author Victor Boivie <boivie@webrtc.org> Sat May 22 20:25:17 2021
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> Thu May 27 07:40:11 2021
tree 91118d7919c0f460d8038bdd7b4f4db6f4bde593
parent 36ad60613d21c697b6b6363a860a1646a75e81ba

dcsctp: Avoid recalculation of outstanding bytes

Recalculating outstanding bytes is expensive when the congestion window
is large, as it iterates over all inflight data chunks. By doing it
incrementally, it will be a constant operation in most cases, and
in the remaining cases, a function of the number of chunks acked in a
single SACK, which is typically just a few chunks.

Implementing this fix required some refactoring to calculate it
correctly (and to be honest, it was likely done incorrectly previously).

Previously, the state of an item in the retransmission queue was
simplified as "in flight", "acked", "nacked", "abandoned", but these
were not completely orthogonal. A chunk could be abandoned while it was
in-flight or it could be abandoned because it was lost. The difference
between these if that chunk should be accounted for in
outstanding_bytes() or not.

Unit tests have been added to verify this.

Bug: webrtc:12799
Change-Id: I72341538bb0c4f8f89555b08f0c8a28815f0f828
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219623
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34139}