netdev - RE: [patch net-next v2 5/8] Introduce sample tc action

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Date:   Wed, 4 Jan 2017 11:01:46 +0000
From:   Yotam Gigi <yotamg@...lanox.com>
To:     Simon Horman <simon.horman@...ronome.com>
CC:     Roopa Prabhu <roopa@...ulusnetworks.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Ido Schimmel <idosch@...lanox.com>,
        Elad Raz <eladr@...lanox.com>,
        Nogah Frankel <nogahf@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "linux@...ck-us.net" <linux@...ck-us.net>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>
Subject: RE: [patch net-next v2 5/8] Introduce sample tc action

>-----Original Message-----
>From: Simon Horman [mailto:simon.horman@...ronome.com]
>Sent: Wednesday, January 04, 2017 12:43 PM
>To: Yotam Gigi <yotamg@...lanox.com>
>Cc: Roopa Prabhu <roopa@...ulusnetworks.com>; Jiri Pirko <jiri@...nulli.us>;
>netdev@...r.kernel.org; davem@...emloft.net; Ido Schimmel
><idosch@...lanox.com>; Elad Raz <eladr@...lanox.com>; Nogah Frankel
><nogahf@...lanox.com>; Or Gerlitz <orlitz@...lanox.com>;
>jhs@...atatu.com; geert+renesas@...der.be; stephen@...workplumber.org;
>xiyou.wangcong@...il.com; linux@...ck-us.net; john.fastabend@...il.com
>Subject: Re: [patch net-next v2 5/8] Introduce sample tc action
>
>On Wed, Nov 16, 2016 at 04:26:44PM +0000, Yotam Gigi wrote:
>> >-----Original Message-----
>> >From: Roopa Prabhu [mailto:roopa@...ulusnetworks.com]
>> >Sent: Wednesday, November 16, 2016 6:15 PM
>> >To: Jiri Pirko <jiri@...nulli.us>
>> >Cc: netdev@...r.kernel.org; davem@...emloft.net; Yotam Gigi
>> ><yotamg@...lanox.com>; Ido Schimmel <idosch@...lanox.com>; Elad Raz
>> ><eladr@...lanox.com>; Nogah Frankel <nogahf@...lanox.com>; Or Gerlitz
>> ><ogerlitz@...lanox.com>; jhs@...atatu.com; geert+renesas@...der.be;
>> >stephen@...workplumber.org; xiyou.wangcong@...il.com; linux@...ck-
>us.net;
>> >john.fastabend@...il.com; simon.horman@...ronome.com
>> >Subject: Re: [patch net-next v2 5/8] Introduce sample tc action
>> >
>> >On 11/14/16, 7:00 AM, Jiri Pirko wrote:
>> >> From: Yotam Gigi <yotamg@...lanox.com>
>> >>
>> >> This action allow the user to sample traffic matched by tc classifier.
>> >> The sampling consists of choosing packets randomly, truncating them,
>> >> adding some informative metadata regarding the interface and the original
>> >> packet size and mark them with specific mark, to allow further tc rules to
>> >> match and process. The marked sample packets are then injected into the
>> >> device ingress qdisc using netif_receive_skb.
>> >>
>> >> The packets metadata is packed using the ife encapsulation protocol, and
>> >> the outer packet's ethernet dest, source and eth_type, along with the
>> >> rate, mark and the optional truncation size can be configured from
>> >> userspace.
>> >>
>> >> Example:
>> >> To sample ingress traffic from interface eth1, and redirect the sampled
>> >> the sampled packets to interface dummy0, one may use the commands:
>> >>
>> >> tc qdisc add dev eth1 handle ffff: ingress
>> >>
>> >> tc filter add dev eth1 parent ffff: \
>> >> 	   matchall action sample rate 12 mark 17
>> >
>> >Yotham, I am guessing in the future if one does not want to use mark,
>> >the sample api is extensible to allow for other actions to be added.
>> >This is from the general concern we had on using mark: some may not want to
>use
>> >mark.
>> >As long as the api is extensible to allow an alternate way in the future,
>> > we should be good. (We would prefer to not go down the path of having to
>> >introduce
>> >a new  'action sample' if this limits us in some way).
>>
>> The code is extensible  - if one does want to add another action to sample, he
>> totally can :)
>>
>> By the way, one of the reasons we removed the patches for now is that we
>> consider adding mirroring functionality to it instead of heaving two tc-rules.
>
>Hi Yotham,
>
>I see that this action combines several discrete sub-actions, some of which
>duplicate functionality present in existing actions:
>
>* sample
>* truncate
>* IFE encapsulation with metadata
>* mark
>* output (proposed)
>
>I wonder if it would make sense to provided a mechanism whereby sampled
>packets can be passed on to other actions. Something similar to the
>existing pipe mechanism but allowing for the sampled and the original packets
>to continue to be processed separately.
>
>If so, it may be worth white-listing actions for which sampled packets are
>known to work well to limit the scope for unforseen side effects.

Hi Simon,

The patches were removed and we intend to propose a different implementation for
that, using a dedicated sampling netlink channel, thus removing the need to
mark, mirror and IFE-pack the packets.

We intend to send in the next few weeks, so I guess you can comment on the new
version.

Thanks!