netdev - Re: [RFC net-next] net: sch_clsact: add support for global per-netns classifier mode

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Date:   Tue, 5 Sep 2017 21:09:27 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Ahern <dsa@...ulusnetworks.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [RFC net-next] net: sch_clsact: add support for global per-netns
 classifier mode

On Tue, Sep 5, 2017 at 3:25 PM, Jamal Hadi Salim <jhs@...atatu.com> wrote:
> On 17-09-05 06:01 PM, Roopa Prabhu wrote:
>
>>
>> yes, like Nikolay says we have been discussing this as well. Nikolay's
>> patch is a cleaver and most importantly non-invasive
>> way today given the anchor point for tc rules is a netdev. we have
>> also considered a separate implicit tc anchor device.
>>   lo seemed like a good fit for all global rules given it is already
>> available. And it is not uncommon to hang off global
>> network config on the loopback interface.
>>
>
> IMO, Jiri has done all the necessary work already with the concept of
> blocks. We dont really need the netdev to be the attachment point.
>
> You can add to a block in many locations in the kernel by
> constructing the proper "coordinates" in the tcmsg.
> i.e this:
>   tcmsg {
>         unsigned char   tcm_family;
>         unsigned char   tcm__pad1;
>         unsigned short  tcm__pad2;
>         int             tcm_ifindex;
>         __u32           tcm_handle;
>         __u32           tcm_parent;
> }
>
> If you were to set tcm_ifindex to -1 (since that is not a legit
> ifindex) then all we need to do is define a parent for a
> different location. Current locations tied to netdevs are:
> -----
> #define TC_H_ROOT       (0xFFFFFFFFU)
> #define TC_H_INGRESS    (0xFFFFFFF1U)
> #define TC_H_CLSACT     TC_H_INGRESS
>
> #define TC_H_MIN_INGRESS        0xFFF2U
> #define TC_H_MIN_EGRESS         0xFFF3U
> -----
>
> You should be able to say add a location which maps to a pre-routing
> or post-routing etc; and this would work as well...
>

ok, interesting. Jiri's examples still showed netdev as attachment point.
we will explore some more. thanks.