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Address panic with PRR due to missed initialization of recover_fs
Needs ReviewPublic

Authored by rscheff on Tue, Jan 12, 11:28 AM.

Details

Summary

When using the base stack in conjunction with RACK, it appears that
infrequently, ++tp->t_dupacks is instantly larger than tcprexmtthresh.

This leaves the recover flightsize (sackhint.recover_fs) uninitialized,
leading to a div/0 panic.

Address this by properly initializing the variable just prior to first
use, if it is not properly initialized.

In order to prevent stale information from a prior recovery to
negatively impact the PRR calculations in this event, also clear
recover_fs once loss recovery is finished.

Finally, improve the readability of the initialization of recover_fs
when t_dupacks == tcprexmtthresh by adjusting the indentation and
using the max(1, snd_nxt - snd_una) macro.

Diff Detail

Repository
rS FreeBSD src repository - subversion
Lint
Lint OK
Unit
No Unit Test Coverage
Build Status
Buildable 36198
Build 33087: arc lint + arc unit

Event Timeline

This revision is now accepted and ready to land.Tue, Jan 12, 6:52 PM
  • init recover_fs in tcp_default_fb_init() if switching stacks during fastrecovery
This revision now requires review to proceed.Thu, Jan 14, 3:19 PM

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