linux-kernel - Re: [PATCH] Periodically flow expire from flow offload tables

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Message-Id: <F754AC3A-D89A-4CF7-97AE-CA59B18A758E@gmail.com>
Date:   Tue, 25 Oct 2022 15:32:51 +0200
From:   Michael Lilja <michael.lilja@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org
Subject: Re: [PATCH] Periodically flow expire from flow offload tables

Hi, 

Thanks for the optimisation suggestions, my nft is a rough conversion from iptables, I will look into using maps.

The ingress chain will work fine for SW OFFLOAD but HW OFFLOAD is not solved by this, at least what I see is that once a flow is offloaded to HW the driver doesn’t see the packets?

If I use the ingress chain I guess I don’t have access to ‘ct mark’ yet? I could think of a use-case where schedules should only some ‘flow type’:
 meta mask != 0x12340000/16 meta day “Tuesday" meta hour >= "06:00" meta hour < "07:00" drop 

I have more advanced rules that check the ct mark and will need to drop if mark == something. These mark == something rules are applied ‘runtime’ and flowables doesn’t seem to be flushed on nft load, which is also a reason for my ‘flow retire’ from the tables.

So my overall goal is to receive packets, mark them with a value depending on 'flow type' and then for the flows that are allowed to be forwarded offload them to the ingress flow table for either HW or SW offload. Once in a while I will change the verdict of a ‘flow type’ and will need that to apply for all existing flows and future flows, besides the fixed schedules, and it should work both for SW OFFLOAD and HW OFFLOAD.

I only have the M7621 device to play with for HW OFFLOAD, but it works fine with my patch.

Thanks

> 
> 
> I suggest to move your 'forward' chain to netdev/ingress using priority
> 
>      filter - 1
> 
> so the time schedule evaluation is always done before the flowtable
> lookup, that is, schedules rules will be always evaluated.
> 
> In your example, you are using a linear ruleset, which might defeat
> the purpose of the flowtable. So I'm attaching a new ruleset
> transformed to use maps and the ingress chain as suggested.
> <schedules.nft>