netdev - Re: [PATCH net-next v5 6/7] net/sched: act

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Message-ID: <87edree9uu.fsf@nvidia.com>
Date:   Sat, 28 Jan 2023 21:28:34 +0200
From:   Vlad Buslov <vladbu@...dia.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
CC:     <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
        <jhs@...atatu.com>, <xiyou.wangcong@...il.com>, <jiri@...nulli.us>,
        <ozsh@...dia.com>, <marcelo.leitner@...il.com>,
        <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v5 6/7] net/sched: act_ct: offload UDP NEW
 connections


On Sat 28 Jan 2023 at 20:09, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> On Sat, Jan 28, 2023 at 05:31:40PM +0200, Vlad Buslov wrote:
>> 
>> On Sat 28 Jan 2023 at 16:26, Pablo Neira Ayuso <pablo@...filter.org> wrote:
>> > Hi Vlad,
>> >
>> > On Fri, Jan 27, 2023 at 07:38:44PM +0100, Vlad Buslov wrote:
>> >> Modify the offload algorithm of UDP connections to the following:
>> >> 
>> >> - Offload NEW connection as unidirectional.
>> >> 
>> >> - When connection state changes to ESTABLISHED also update the hardware
>> >> flow. However, in order to prevent act_ct from spamming offload add wq for
>> >> every packet coming in reply direction in this state verify whether
>> >> connection has already been updated to ESTABLISHED in the drivers. If that
>> >> it the case, then skip flow_table and let conntrack handle such packets
>> >> which will also allow conntrack to potentially promote the connection to
>> >> ASSURED.
>> >> 
>> >> - When connection state changes to ASSURED set the flow_table flow
>> >> NF_FLOW_HW_BIDIRECTIONAL flag which will cause refresh mechanism to offload
>> >> the reply direction.
>> >> 
>> >> All other protocols have their offload algorithm preserved and are always
>> >> offloaded as bidirectional.
>> >> 
>> >> Note that this change tries to minimize the load on flow_table add
>> >> workqueue. First, it tracks the last ctinfo that was offloaded by using new
>> >> flow 'ext_data' field and doesn't schedule the refresh for reply direction
>> >> packets when the offloads have already been updated with current ctinfo.
>> >> Second, when 'add' task executes on workqueue it always update the offload
>> >> with current flow state (by checking 'bidirectional' flow flag and
>> >> obtaining actual ctinfo/cookie through meta action instead of caching any
>> >> of these from the moment of scheduling the 'add' work) preventing the need
>> >> from scheduling more updates if state changed concurrently while the 'add'
>> >> work was pending on workqueue.
>> >
>> > Could you use a flag to achieve what you need instead of this ext_data
>> > field? Better this ext_data and the flag, I prefer the flags.
>> 
>> Sure, np. Do you prefer the functionality to be offloaded to gc (as in
>> earlier versions of this series) or leverage 'refresh' code as in
>> versions 4-5?
>
> No, I prefer generic gc/refresh mechanism is not used for this.
>
> What I mean is: could you replace this new ->ext_data generic pointer
> by a flag to annotate what you need?

Yes, will do.

> Between this generic pointer and a flag, I prefer a flag.

Got it.