netdev - Re: [patch net-next v2 1/4] net: Introduce psample, a new genetlink channel for packet sampling

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Date:   Tue, 24 Jan 2017 09:32:05 +0100
From:   Simon Horman <simon.horman@...ronome.com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, yotamg@...lanox.com,
        idosch@...lanox.com, eladr@...lanox.com, nogahf@...lanox.com,
        ogerlitz@...lanox.com, jhs@...atatu.com, geert+renesas@...der.be,
        stephen@...workplumber.org, xiyou.wangcong@...il.com,
        linux@...ck-us.net, roopa@...ulusnetworks.com,
        john.fastabend@...il.com, mrv@...atatu.com
Subject: Re: [patch net-next v2 1/4] net: Introduce psample, a new genetlink
 channel for packet sampling

On Mon, Jan 23, 2017 at 11:07:08AM +0100, Jiri Pirko wrote:
> From: Yotam Gigi <yotamg@...lanox.com>
> 
> Add a general way for kernel modules to sample packets, without being tied
> to any specific subsystem. This netlink channel can be used by tc,
> iptables, etc. and allow to standardize packet sampling in the kernel.
> 
> For every sampled packet, the psample module adds the following metadata
> fields:
> 
> PSAMPLE_ATTR_IIFINDEX - the packets input ifindex, if applicable
> 
> PSAMPLE_ATTR_OIFINDEX - the packet output ifindex, if applicable
> 
> PSAMPLE_ATTR_ORIGSIZE - the packet's original size, in case it has been
>    truncated during sampling
> 
> PSAMPLE_ATTR_SAMPLE_GROUP - the packet's sample group, which is set by the
>    user who initiated the sampling. This field allows the user to
>    differentiate between several samplers working simultaneously and
>    filter packets relevant to him
> 
> PSAMPLE_ATTR_GROUP_SEQ - sequence counter of last sent packet. The
>    sequence is kept for each group
> 
> PSAMPLE_ATTR_SAMPLE_RATE - the sampling rate used for sampling the packets
> 
> PSAMPLE_ATTR_DATA - the actual packet bits
> 
> The sampled packets are sent to the PSAMPLE_NL_MCGRP_SAMPLE multicast
> group. In addition, add the GET_GROUPS netlink command which allows the
> user to see the current sample groups, their refcount and sequence number.
> This command currently supports only netlink dump mode.
> 
> Signed-off-by: Yotam Gigi <yotamg@...lanox.com>
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>

Hi Jiri, Hi Yotam,

this looks good to me.

Reviewed-by: Simon Horman <simon.horman@...ronome.com>

I do, however, have one question: what is your feeling about allowing
the per-action cooking which Jamal has proposed[1] to be emited as
metadata as another PSAMPLE_ATTR_* attribute? For one thing I think it
would allow for smooth integration with OvS user-space which makes use of a
cookie.

[1] "[PATCH net-next v6 1/1] net sched actions: Add support for user cookies"