netdev - Re: "xfrm: Fix the gc threshold value for ipv4" broke my IPSec connections

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Date:	Tue, 15 Oct 2013 14:02:37 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Damian Pietras <damianp@...er.net>
Cc:	netdev@...r.kernel.org
Subject: Re: "xfrm: Fix the gc threshold value for ipv4" broke my IPSec
 connections

On Tue, 2013-10-15 at 22:40 +0200, Damian Pietras wrote:
> I've recently upgraded from 3.4.x to 3.10.x and this broke my IPSec
> setup in transport mode. The simplest test case is to setup few such
> connections with few boxes like this:
> 
> spdadd 192.168.1.100 192.168.2.100 any -P out ipsec
>            esp/transport//require
>            ah/transport//require;
> 
> spdadd 192.168.2.100 192.168.1.100 any -P in ipsec
>            esp/transport//require
>            ah/transport//require;
> 
> Then set up an HTTP server on one box and run ab on the other box to
> create come TCP connections:
> 
> ab -n 10000 -c 50 http://192.168.1.100/
> 
> Then the connect() call will very quickly start returning ENOBUFS. I
> haven't seen anything wrong with my simple setup (just copy of
> ipsec-howto.org in transport mode and pre shared keys) and started
> bisecting. That way I found this commit to break my case:
> 
> 703fb94ec58e0e8769380c2877a8a34aeb5b6c97
> xfrm: Fix the gc threshold value for ipv4
> 
> Reverting it on 3.10.15 fixes my issue. This seems to be there from 3.7
> and I don't really believe such simple case stayed broken for so long.
> Em I missing something or there is really a bug?
> 
> If smeone is interested in details of this configuration and commands
> I'm running, just let me know. This was reproduced with few VMs under XEN.
> 

It looks like you need to tune /proc/sys/net/ipv4/xfrm4_gc_thresh to a
sensible value given your workload.

try :

echo 65536 >/proc/sys/net/ipv4/xfrm4_gc_thresh

Presumably the 1024 default is really too small...



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