netdev - Re: [PATCH net-next 1/2] br_netfilter: add struct netns

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Date:   Tue, 27 Nov 2018 01:20:47 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...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
Subject: Re: [PATCH net-next 1/2] br_netfilter: add struct netns_brnf

Hi,

On Wed, Nov 07, 2018 at 02:48:58PM +0100, Christian Brauner wrote:
[...]
> diff --git a/include/net/netns/netfilter.h b/include/net/netns/netfilter.h
> index ca043342c0eb..eedbd1ac940e 100644
> --- a/include/net/netns/netfilter.h
> +++ b/include/net/netns/netfilter.h
> @@ -35,4 +35,20 @@ struct netns_nf {
>  	bool			defrag_ipv6;
>  #endif
>  };
> +
> +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;
> +};

I have spun on this several times, wondering if there's a way to avoid
scratching these many bytes per netns to expose these sysctl entries
that are plain on/off toggles... You said this:

>Currently, the /proc/sys/net/bridge folder is only created in the
>initial network namespace

I think we can add one single sysctl to expose these as flags from net
namespaces. Idea is to keep the existing (legacy) sysctl entries for
init_net only, and add a new single new one that exposes these as flags
(should be also available for consistency in init_net I'd suggest).
Flags could be map in this way, eg.

        0x1     call_iptables
        0x2     call_ip6tables
        0x4     call_arptables
        0x8     filter_vlan_tagged
        ...

Also documentation would be good to have for this.

Would this idea fly for you? Thanks.