netdev - Re: [patch net-next RFC 4/6] Introduce sample tc action

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Date:   Wed, 19 Oct 2016 00:33:19 -0700
From:   Roopa Prabhu <roopa@...ulusnetworks.com>
To:     Yotam Gigi <yotamg@...lanox.com>
CC:     Jamal Hadi Salim <jhs@...atatu.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>,
        "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>,
        Shrijeet Mukherjee <shm@...ulusnetworks.com>,
        Yotam Gigi <yotam.gi@...il.com>
Subject: Re: [patch net-next RFC 4/6] Introduce sample tc action

On 10/18/16, 3:58 AM, Yotam Gigi wrote:

> On 16-10-15 12:34 PM, Roopa Prabhu wrote:
[snip]

>> The OVS implementation is a good example, the metadata includes all the
>> actions applied
>>>> to the packet in the kernel data path.
>>>>
>>> Again not sure what the use case would be (and why waste such space
>>> especially when you are sending over the wire with such details).
>> All this is being used currently.., But, this can be other api's sflow uses
>> for monitoring.
>> http://openvswitch.org/support/ovscon2014/17/1400-ovs-sflow.pdf
>> 	
>> Does not have to be part of the main/basic sampling api...
>> it was just an example.
>>
> I guess that making the API extensible solves this, isn't it?

yes, that might help...

Just wanted to bring up the question/clarification on using mark again

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 172 0xff
           action mirred egress redirect dev dummy0

Like we discussed @ netdev, mark can be used by other things in the system.
A request to sample on an interface cannot be disruptive.
Does this require mark to be not used elsewhere in the system when sampling is enabled on an interface ?