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Differential D20908

Fixing the DSACK code to properly clean up after sending a DSACK.
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Authored by rrs on Jul 10 2019, 9:13 PM.
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rscheff

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Reviewers
tuexen
rscheff
Group Reviewers
transport
Commits
rS349987: This is the second in a number of patches needed to
Summary

The DSACK RFC is quite clear that you only send a DSACK block
once for every received packet. The current implementation of DSACK
on FreeBSD has a flaw in that it only uses new data from a client to
drive it to clean up a DSACK block. This is incorrect, and instead
after a successful transmit any DSACK blocks should be purged.

wIthout this fix once you receive (as a server) a DSACK block
you may get it multiple times.

Test Plan

We have been now running with this at NF for at least a week and
validated that we no longer see the same DSACK sent out multiple
times without having received the same data multiple times.

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Repository
rS FreeBSD src repository - subversion
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Event Timeline

rrs created this revision.Jul 10 2019, 9:13 PM
rscheff accepted this revision.Jul 11 2019, 4:18 AM
rscheff added a subscriber: rscheff.

Sorry for the oversight; Indeed I tested this with continous data from the receiver only, not when the data direction changes :(

This revision is now accepted and ready to land.Jul 11 2019, 4:18 AM
tuexen accepted this revision.Jul 11 2019, 6:11 AM
Closed by commit rS349987: This is the second in a number of patches needed to (authored by rrs). · Explain WhyJul 14 2019, 4:06 PM
This revision was automatically updated to reflect the committed changes.
rrs added a commit: rS349987: This is the second in a number of patches needed to.
Herald added a subscriber: imp. · View Herald TranscriptJul 14 2019, 4:06 PM
tuexen mentioned this in rS360282: Improve the TCP SACK generation by reporting DSACKs.Apr 24 2020, 9:30 PM

Revision Contents
Changeset List

PathSize
head/
sys/
netinet/
8 lines
39 lines
tcp_stacks/
7 lines
1 line

Diff 59737

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head/sys/netinet/tcp_output.c

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head/sys/netinet/tcp_sack.c

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head/sys/netinet/tcp_stacks/rack.c

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head/sys/netinet/tcp_var.h

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