netdev - Re: [patch net-next] net: sched: choke: remove dead filter classify code

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Message-Id: <20170324.124638.1229066743314753196.davem@davemloft.net>
Date:   Fri, 24 Mar 2017 12:46:38 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     xiyou.wangcong@...il.com
Cc:     jiri@...nulli.us, netdev@...r.kernel.org, jhs@...atatu.com,
        mlxsw@...lanox.com
Subject: Re: [patch net-next] net: sched: choke: remove dead filter
 classify code

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Fri, 24 Mar 2017 10:59:15 -0700

> On Thu, Mar 23, 2017 at 9:02 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>> From: Jiri Pirko <jiri@...lanox.com>
>>
>> sch_choke is classless qdisc so it does not define cl_ops. Therefore
>> filter_list cannot be ever changed, being NULL all the time.
>> Reason is this check in tc_ctl_tfilter:
> 
> Are you sure? According to the definition in comments:
> 
>    CHOKe (CHOose and Keep for responsive flows, CHOose and Kill for
>    unresponsive flows) is a variant of RED that penalizes misbehaving flows but
>    maintains no flow state. The difference from RED is an additional step
>    during the enqueuing process. If average queue size is over the
>    low threshold (qmin), a packet is chosen at random from the queue.
>    If both the new and chosen packet are from the same flow, both
>    are dropped. Unlike RED, CHOKe is not really a "classful" qdisc because it
>    needs to access packets in queue randomly. It has a minimal class
>    interface to allow overriding the builtin flow classifier with
>    filters.
> 
> It should implement filters otherwise how to classify flows in
> its definition?

The flows are matched by hand using the flow dissector.

Jiri is right, this is all dead code and should be removed.