linux-kernel - Re: [PATCH RESEND net-next 1/2] br_netfilter: add struct netns

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Date:   Fri, 7 Jun 2019 16:28:58 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        davem@...emloft.net, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        bridge@...ts.linux-foundation.org, tyhicks@...onical.com,
        kadlec@...ckhole.kfki.hu, fw@...len.de, roopa@...ulusnetworks.com,
        nikolay@...ulusnetworks.com, linux-kernel@...r.kernel.org,
        richardrose@...gle.com, vapier@...omium.org, bhthompson@...gle.com,
        smbarber@...omium.org, joelhockey@...omium.org,
        ueberall@...menzentrisch.de
Subject: Re: [PATCH RESEND net-next 1/2] br_netfilter: add struct netns_brnf

On Fri, Jun 07, 2019 at 03:25:16PM +0200, Christian Brauner wrote:
> On Thu, Jun 06, 2019 at 06:30:35PM +0200, Pablo Neira Ayuso wrote:
> > On Thu, Jun 06, 2019 at 05:19:39PM +0200, Christian Brauner wrote:
> > > On Thu, Jun 06, 2019 at 08:14:40AM -0700, Stephen Hemminger wrote:
> > > > On Thu,  6 Jun 2019 13:41:41 +0200
> > > > Christian Brauner <christian@...uner.io> wrote:
> > > > 
> > > > > +struct netns_brnf {
> > > > > +#ifdef CONFIG_SYSCTL
> > > > > +	struct ctl_table_header *ctl_hdr;
> > > > > +#endif
> > > > > +
> > > > > +	/* default value is 1 */
> > > > > +	int call_iptables;
> > > > > +	int call_ip6tables;
> > > > > +	int call_arptables;
> > > > > +
> > > > > +	/* default value is 0 */
> > > > > +	int filter_vlan_tagged;
> > > > > +	int filter_pppoe_tagged;
> > > > > +	int pass_vlan_indev;
> > > > > +};
> > > > 
> > > > Do you really need to waste four bytes for each
> > > > flag value. If you use a u8 that would work just as well.
> > > 
> > > I think we had discussed something like this but the problem why we
> > > can't do this stems from how the sysctl-table stuff is implemented.
> > > I distinctly remember that it couldn't be done with a flag due to that.
> > 
> > Could you define a pernet_operations object? I mean, define the id and size
> > fields, then pass it to register_pernet_subsys() for registration.
> > Similar to what we do in net/ipv4/netfilter/ipt_CLUSTER.c, see
> > clusterip_net_ops and clusterip_pernet() for instance.
> 
> Hm, I don't think that would work. The sysctls for br_netfilter are
> located in /proc/sys/net/bridge under /proc/sys/net which is tightly
> integrated with the sysctls infrastructure for all of net/ and all the
> folder underneath it including "core", "ipv4" and "ipv6".
> I don't think creating and managing files manually in /proc/sys/net is
> going to fly. It also doesn't seem very wise from a consistency and
> complexity pov. I'm also not sure if this would work at all wrt to file
> creation and reference counting if there are two different ways of
> managing them in the same subfolder...
> (clusterip creates files manually underneath /proc/net which probably is
> the reason why it gets away with it.)

br_netfilter is now a module, and br_netfilter_hooks.c is part of it
IIRC, this file registers these sysctl entries from the module __init
path.

It would be a matter of adding a new .init callback to the existing
brnf_net_ops object in br_netfilter_hooks.c. Then, call
register_net_sysctl() from this .init callback to register the sysctl
entries per netns.

There is already a brnf_net area that you can reuse for this purpose,
to place these pernetns flags...

struct brnf_net {
        bool enabled;
};

which is going to be glad to have more fields (under the #ifdef
CONFIG_SYSCTL) there.