netdev - Re: [PATCH iptables] libxt_cgroup2: add support for cgroup2 path matching

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Message-ID: <20151117230924.GL22864@mtj.duckdns.org>
Date:	Tue, 17 Nov 2015 18:09:24 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Jan Engelhardt <jengelh@...i.de>
Cc:	davem@...emloft.net, pablo@...filter.org, kaber@...sh.net,
	kadlec@...ckhole.kfki.hu, 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,
	daniel@...earbox.net, daniel.wagner@...-carit.de,
	nhorman@...driver.com
Subject: Re: [PATCH iptables] libxt_cgroup2: add support for cgroup2 path
 matching

Hello,

On Wed, Nov 18, 2015 at 12:02:01AM +0100, Jan Engelhardt wrote:
> On Tuesday 2015-11-17 20:42, Tejun Heo wrote:
> >+static void cgroup2_save(const void *ip, const struct xt_entry_match *match)
> >+{
> >+	const struct xt_cgroup2_info *info = (void *)match->data;
> >+
> >+	printf("%s --path %s", info->invert ? " !" : "", info->path);
> >+}
> 
> Can cgroup path names contain anything fancy, like spaces, backslashes, etc.?
> If so, xtables_save_string() will be needed here.

Will update.

> >+static struct xtables_match cgroup2_match = {
> >+	.family		= NFPROTO_UNSPEC,
> >+	.name		= "cgroup2",
> >+	.version	= XTABLES_VERSION,
> >+	.size		= XT_ALIGN(sizeof(struct xt_cgroup2_info)),
> >+	.userspacesize	= XT_ALIGN(sizeof(struct xt_cgroup2_info)),
> 
> userspacesize must not include xt_cgroup2_info.priv.
> Change to offsetof(...), cf. other .c modules which do this.

Ah, okay.

...
> >+\fBIMPORTANT\fP: when being used in the INPUT chain, the cgroup2
> >+matcher is currently only of limited functionality, meaning it
> >+will only match on packets that are processed for local sockets
> >+through early socket demuxing. Therefore, general usage on the
> >+INPUT chain is disadviced unless the implications are well
> 
> is disadviced (sic)  -> is not advised

Will update.  That's copied verbatim from xt_cgroup tho.  Will create
a patch to update that too.

Thanks.

-- 
tejun
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