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    SubjectRe: [PATCH net-next 1/2] br_netfilter: add struct netns_brnf
    On Tue, Nov 27, 2018 at 03:20:45AM +0100, Christian Brauner wrote:
    > On Tue, Nov 27, 2018 at 01:20:47AM +0100, Pablo Neira Ayuso wrote:
    > > 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.
    >
    > My suggestion is to keep these files per network namespace but have a
    > single flag argument in struct netns_brnf:
    > +struct netns_brnf {
    > +#ifdef CONFIG_SYSCTL
    > + struct ctl_table_header *ctl_hdr;
    > +#endif
    > +
    > + /* default value is 1 */
    > + unsigned int filter_flags;
    > +};
    >
    > #define BRNF_CALL_IPTABLES 0x1
    > #define BRNF_CALL_IP6TABLES 0x2
    > #define BRNF_CALL_ARPTABLES 0x4
    > #define BRNF_CALL_VLAN_TAGGED 0x8
    >
    > a write to the corresponding file would then cause the flag to be set or
    > unset in filter_flags.
    > This way we are a) space-efficient internally not bloating struct net
    > while b) not breaking running tools in non-initial network namespaces
    > that expect the files to be there. b) is really the important bit here. :)

    OK, please, go explore this space-efficient approach. Thanks.

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