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

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Date:   Thu, 10 Nov 2016 19:58:33 +0000
From:   Yotam Gigi <yotamg@...lanox.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "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>,
        "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>
Subject: RE: [patch net-next 5/8] Introduce sample tc action



>-----Original Message-----
>From: John Fastabend [mailto:john.fastabend@...il.com]
>Sent: Thursday, November 10, 2016 9:38 PM
>To: Jiri Pirko <jiri@...nulli.us>; netdev@...r.kernel.org
>Cc: 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; roopa@...ulusnetworks.com
>Subject: Re: [patch net-next 5/8] Introduce sample tc action
>
>On 16-11-10 11:35 AM, John Fastabend wrote:
>> On 16-11-10 03:23 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
>>>
>>> tc filter add parent ffff: dev eth1 protocol all \
>>> 	   u32 match mark 17 0xff \
>>> 	   action mirred egress redirect dev dummy0
>>>
>>> Where the first command adds an ingress qdisc and the second starts
>>> sampling every 12'th packet on dev eth1 and marks the sampled packets with
>>> 17. The third command catches the sampled packets, which are marked with
>>> 17, and redirects them to dev dummy0.
>>
>> The sampling algorithm was not randomized based on the above commit
>> log? It really needs to be for all the reasons Roopa mentioned earlier.
>> Did I miss some email on why it didn't get implemented?
>>
>> Also there was an indication the already is actually implemented
>> correctly so don't we need the hw/sw to behave the same. The whole
>> argument about sw/hw parity, etc.
>
>sorry bit of a typo there corrected 2nd paragraph here...
>
>Also there was an indication the hardware is already implemented \
>correctly so don't we need the hw/sw to behave the same. The argument
>about sw/hw parity, etc.

Our hardware currently does not support sampling with random behavior, so 
we did implement it in software too. 

But, the API is extensible and it is possible to add a random keyword to 
the tc action to allow random sampling. In that case, the keyword will be
implemented in sw only and our driver will fail offloading it.

>
>>
>>>
>>> Signed-off-by: Yotam Gigi <yotamg@...lanox.com>
>>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>>> ---
>>