linux-kernel - Re: [PATCH 4/5] sock, cgroup: add sock->sk

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Date:	Tue, 17 Nov 2015 22:46:30 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Tejun Heo <tj@...nel.org>, davem@...emloft.net,
	pablo@...filter.org, kaber@...sh.net, kadlec@...ckhole.kfki.hu,
	lizefan@...wei.com, hannes@...xchg.org
CC:	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	coreteam@...filter.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-team@...com,
	daniel.wagner@...-carit.de, nhorman@...driver.com
Subject: Re: [PATCH 4/5] sock, cgroup: add sock->sk_cgroup

Hi Tejun,

On 11/17/2015 08:40 PM, Tejun Heo wrote:
...
> While it is possible to solve these issues from controller side by
> implementing hierarchical allowable ranges in both controllers, it
> would involve quite a bit of complexity in the controllers and further
> obfuscate network configuration as it becomes even more difficult to
> tell what's actually being configured looking from the network side.
> While not much can be done for v1 at this point, as membership
> handling is sane on cgroup v2, it'd be better to make cgroup matching
> behave like other network matches and classifiers than introducing
> further complications.
>
> In preparation, this patch adds sock->sk_cgroup which points to the
> associated cgroup.  A sock is associated on creation and stays
> associated to the same cgroup until freed; unfortunately, this ends up
> adding another cgroup field to struct sock on top of sk_cgrp_prioidx
> and sk_classid.  I tried to think of a way to somehow overload the
> existing fields but couldn't come up with a reasonable one.  For the
> longer term, the fields can be rearranged so that disabling prio and
> cls controllers reduce the size of the struct.

Do you see a way forward where the new behavior could be enabled f.e.
as an extra mount option (that long-term would be made default, while
deprecating the current behavior) on net_cls et al? There are various
more users at least on the net_cls side (nft and tc as well). Would be
really great, if sk_cgroup could abstract that somehow away for all of
them w/o adding a second version to all users.

Best,
Daniel
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