PRR: Avoid accounting left-edge twice in partial ACK.
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Authored by rscheff on Feb 20 2021, 6:39 PM.

Details

Reviewers

kbowling
tuexen
jtl
rrs
thj

Group Reviewers

transport

Commits

rG25fb4c363b29: PRR: Avoid accounting left-edge twice in partial ACK.
rG31d7a27c6e88: PRR: Avoid accounting left-edge twice in partial ACK.

Summary

After D18624, accounting the advance of the left edge
in a partial ack is already included in
sackhint.delivered_data.

Therefore this is a cumulative error of the
prr_delivered bytes, over the course of multiple
partial acks while lost packets get acknowledged in
sequence.

Test Plan

Corrected behavior, maximum of 2 segments per ACK:

prr-partialack-fixed.pkt3 KBDownload

Incorrect behavior due to double-accounting (counterintutively, being more agressive pushing data out - 3 segments per ACK):

prr-partialack.pkt3 KBDownload

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

rscheff created this revision.Feb 20 2021, 6:39 PM

Herald added 1 blocking reviewer(s): transport. · View Herald TranscriptFeb 20 2021, 6:39 PM

Herald added subscribers: melifaro, imp. · View Herald Transcript

rscheff requested review of this revision.Feb 20 2021, 6:39 PM

Harbormaster completed remote builds in B37222: Diff 84337.Feb 20 2021, 6:39 PM

rscheff edited the test plan for this revision. (Show Details)Feb 20 2021, 7:07 PM

rebase to HEAD

Harbormaster completed remote builds in B37226: Diff 84349.Feb 20 2021, 7:37 PM

rscheff retitled this revision from PRR: avoid accounting left-edge twice in parital ack to PRR: Avoid accounting left-edge twice in partial ACK..Feb 20 2021, 7:42 PM

kbowling accepted this revision.Feb 21 2021, 12:01 AM

This revision is now accepted and ready to land.Feb 21 2021, 12:01 AM

Closed by commit rG31d7a27c6e88: PRR: Avoid accounting left-edge twice in partial ACK. (authored by rscheff). · Explain WhyFeb 25 2021, 6:09 PM

This revision was automatically updated to reflect the committed changes.

rscheff added a commit: rG31d7a27c6e88: PRR: Avoid accounting left-edge twice in partial ACK..

rscheff added a commit: rG25fb4c363b29: PRR: Avoid accounting left-edge twice in partial ACK..Feb 28 2021, 8:11 AM

rscheff mentioned this in rGb8ffda0a37e1: tcp: various improvements and fixes to PRR.Mar 4 2021, 12:01 PM