netdev - Re: [net-next PATCH] net: sched: cls_flower: Classify packets using port ranges

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Date:   Thu, 18 Oct 2018 00:22:15 -0700
From:   "Nambiar, Amritha" <amritha.nambiar@...el.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        sridhar.samudrala@...el.com, Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [net-next PATCH] net: sched: cls_flower: Classify packets using
 port ranges

On 10/17/2018 10:41 PM, Cong Wang wrote:
> On Wed, Oct 17, 2018 at 9:42 PM David Miller <davem@...emloft.net> wrote:
>>
>> From: Amritha Nambiar <amritha.nambiar@...el.com>
>> Date: Fri, 12 Oct 2018 06:53:30 -0700
>>
>>> Added support in tc flower for filtering based on port ranges.
>>> This is a rework of the RFC patch at:
>>> https://patchwork.ozlabs.org/patch/969595/
>>
>> You never addressed Cong's feedback asking you to explain why this
>> can't be simply built using existing generic filtering facilities that
>> exist already.
>>
>> I appreciate that you addressed Jiri's feedback, but Cong's feedback is
>> just as, if not more, important.
>>
> 
> My objection is against introducing a new filter just for port range, now
> it is built on top of flower filter, so it is much better now.
> 
> u32 filter can do the nearly same, but requires a power-of-two, so it is
> not completely duplicated.
> 
> Therefore, I think the idea of building it on top of flower is fine. But I don't
> read into any code, only the description.
> 
> Thanks!
> 

Sorry for not clarifying it out, this reworked patch addresses both
Jiri's and Cong's concerns. The previous RFC patch introduced a new
special-purpose classifier called 'range' for port-range based
filtering, that as Cong pointed out had overlaps with other existing
classifiers. The reason I added a new classifier was because u32 does
not support ranges that are not power-of-2 and flower uses mask-key
based rhashtable lookup which was not suited for range based keys. Based
on the feedback for the RFC, this patch adds port-range support to
cls_flower by separating out range comparison from the rhashtable
lookup. Since this adds to cls_flower, overlaps with other
general-purpose classifiers are avoided.

-Amritha