linux-kernel - Re: nf_conntrack: falling back to vmalloc.

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Date:	Fri, 17 Jul 2015 12:10:09 +0200
From:	Florian Westphal <fw@...len.de>
To:	Toralf Förster <toralf.foerster@....de>
Cc:	netfilter-devel@...r.kernel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Pablo Neira Ayuso <pablo@...filter.org>, kaber@...sh.net,
	Marcelo Leitner <mleitner@...hat.com>
Subject: Re: nf_conntrack: falling back to vmalloc.

Toralf Förster <toralf.foerster@....de> wrote:
> I do run a server with a 64 bit hardened Gentoo Linux (kernel currently 4.0.8).
> Around 12th of July it started to spew those messages into kern.log :
> 
> /var/log/kern.log:Jul 12 15:26:07 tor-relay kernel: [538360.650490] nf_conntrack: falling back to vmalloc.
> /var/log/kern.log:Jul 12 15:26:07 tor-relay kernel: [538360.650615] nf_conntrack: falling back to vmalloc.
> /var/log/kern.log:Jul 12 15:26:08 tor-relay kernel: [538361.673649] nf_conntrack: falling back to vmalloc.
> /var/log/kern.log:Jul 12 15:26:08 tor-relay kernel: [538361.673786] nf_conntrack: falling back to vmalloc.
> 
> I read https://bugzilla.openvz.org/show_bug.cgi?id=3092 but a reboot did not help.
> I got 1-2 thousends of those lines per day.

Most likely result of 88eab472ec21f01d3e36ff ("netfilter: conntrack:
adjust nf_conntrack_buckets default value".

Do you run containers?

This message can only be printed when a new network namespace is created
(or something is rmmod/modprobing nf_conntrack module all the time).

I wonder if this is caused by some program creating netns for
sandboxing?

Pablo, Patrick -- any idea on how to stop conntrack from becoming active
in a newly created netns automatically without breaking anything?

With upcoming per netns hooks, we might be able to delay registering
conntrack, defrag etc.  until after a -m conntrack rule has been added.
Dou you think that could work?

For nft we could create an expression to configure conntrack explicitly
(inverse NOTRACK).

[ obviously we can also add that for xtables but that would break
  setups if we suddently move to "you must ask for conntrack via
  ruleset" model. ]
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