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

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Message-ID: <CAM_iQpVJrhXp3-LH94tEf-Z9y0nQ=9DHG0MTxg6i0Xg6bZd=Xw@mail.gmail.com>
Date:   Fri, 24 Mar 2017 13:02:12 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>, mlxsw@...lanox.com
Subject: Re: [patch net-next] net: sched: choke: remove dead filter classify code

On Fri, Mar 24, 2017 at 12:46 PM, David Miller <davem@...emloft.net> wrote:
> 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.

Hmm, sch_choke has a (kinda) built-in cls_flower...