Re: [PATCH 0/3][v2] tcp: fix ICMP-RTO war

David Miller
2010-02-01T07:33:25Z

From: Damian Lukowski <damian@tvk.rwth-aachen.de>
Date: Fri, 29 Jan 2010 23:15:51 +0100

> This patches fix the current RTO calculation routine, when
> srtt and rttvar are zero, yielding an RTO of zero
> Under some circumstances, TCPs srtt and rttvar are zero,
> yielding a calculated RTO of zero.
> This is particularly unfortunate for ICMP based RTO recalculation
> as introduced in f1ecd5d9e736660 (Revert Backoff [v3]: Revert RTO
> on ICMP destination unreachable), as it results in RTO retransmission
> flooding.
>
> Thanks to Ilpo Jarvinen for providing debug patches and to
> Denys Fedoryshchenko for reporting and testing.
>
> Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de>

I still haven't seen a detailed enough analysis of why these
tiny RTOs can come to exist in the first place.

Please show me a list of events, function by function, the value of
relevant variables and per-socket TCP state, in the TCP stack, that
show how this ends up happening.

Thanks for all of your work on this so far.