netdev - Re: [PATCH 9/9] netfilter: implement xt

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Date:	Sat, 21 Nov 2015 12:04:25 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Florian Westphal <fw@...len.de>
Cc:	davem@...emloft.net, pablo@...filter.org, kaber@...sh.net,
	kadlec@...ckhole.kfki.hu, daniel@...earbox.net,
	daniel.wagner@...-carit.de, nhorman@...driver.co,
	lizefan@...wei.com, hannes@...xchg.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...com, ninasc@...com,
	Neil Horman <nhorman@...driver.com>,
	Jan Engelhardt <jengelh@...i.de>
Subject: Re: [PATCH 9/9] netfilter: implement xt_cgroup cgroup2 path match

Hello,

On Sat, Nov 21, 2015 at 05:56:06PM +0100, Florian Westphal wrote:
> > +struct xt_cgroup_info_v1 {
> > +	__u8		has_path;
> > +	__u8		has_classid;
> > +	__u8		invert_path;
> > +	__u8		invert_classid;
> > +	char		path[PATH_MAX];
> > +	__u32		classid;
> > +
> > +	/* kernel internal data */
> > +	void		*priv __attribute__((aligned(8)));
> > +};
> 
> Ahem.  Am I reading this right? This struct is > 4k in size?
> If so -- Ugh.  Does sizeof(path) really have to be PATH_MAX?

Hmmm... yeap but would this be an acutual problem?  We can try to make
it shorter but idk it ultimately is a path.  Another solution would be
trying to pass inode around but that is problematic with showing and
printing rules as the only way to reverse-map inode to path is walking
the tree and the cgroup may already be gone at that point.  While >4k
struct isn't pretty, this looks like the path of least resistance.

Thanks.

-- 
tejun
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