tcp: improve consistency of syncache_respond() failure handling
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Authored by tuexen on Aug 24 2024, 3:16 PM.

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Reviewers

rrs
rscheff
cc
lstewart
peter.lei_ieee.org
glebius

Group Reviewers

transport

Commits

rG0567f7cc1a46: tcp: improve consistency of syncache_respond() failure handling
rG003f1ebcbce1: tcp: improve consistency of syncache_respond() failure handling
rGef438f7706be: tcp: improve consistency of syncache_respond() failure handling

Summary

When the initial sending of the SYN ACK segment using syncache_respond() fails, it is handled as a permanent error. To improve consistency, apply this policy in all cases, where syncache_respond() is called. These include

timer based retransmissions of the SYN ACK
retransmitting a SYN ACK in response to a SYN retransmission
sending of challenge ACKs in response to received RST segments

In these cases, fall back to SYN cookies, if enabled. While there, also improve consistency of the TCP stats counters.
This was discussed at the last FreeBSD transport VC.

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Repository

rG FreeBSD src repository

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Event Timeline

tuexen created this revision.Aug 24 2024, 3:16 PM

Herald added a reviewer: transport. · View Herald TranscriptAug 24 2024, 3:16 PM

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

tuexen requested review of this revision.Aug 24 2024, 3:16 PM

glebius accepted this revision.Sep 3 2024, 10:49 PM

Besides, I am wondering if TCPSTAT_INC(tcps_sndacks) and TCPSTAT_INC(tcps_sndtotal) consistency can also be improved after successful syncache_respond().

This revision is now accepted and ready to land.Sep 4 2024, 7:20 PM

Improve consistency of the TCP stats counters as suggested by cc@.

This revision now requires review to proceed.Sep 4 2024, 10:57 PM

tuexen edited the summary of this revision. (Show Details)Sep 4 2024, 10:58 PM

In D46428#1060788, @cc wrote:

Besides, I am wondering if TCPSTAT_INC(tcps_sndacks) and TCPSTAT_INC(tcps_sndtotal) consistency can also be improved after successful syncache_respond().

Thanks for the suggestion. Done in the latest version of the patch.

cc accepted this revision.Sep 4 2024, 11:46 PM

This revision is now accepted and ready to land.Sep 4 2024, 11:46 PM

Closed by commit rGef438f7706be: tcp: improve consistency of syncache_respond() failure handling (authored by tuexen). · Explain WhySep 5 2024, 7:21 AM

This revision was automatically updated to reflect the committed changes.

tuexen added a commit: rGef438f7706be: tcp: improve consistency of syncache_respond() failure handling.

tuexen added a commit: rG003f1ebcbce1: tcp: improve consistency of syncache_respond() failure handling.Oct 31 2024, 1:40 PM

tuexen added a commit: rG0567f7cc1a46: tcp: improve consistency of syncache_respond() failure handling.Oct 31 2024, 4:37 PM