netdev - Re: [PATCH net-next 1/2] net: flow_offload: mangle 128-bit packet field with one action

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Message-ID: <f4cf8a97-3322-d982-6068-d4c0ce997b1c@solarflare.com>
Date:   Tue, 20 Aug 2019 19:15:10 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
CC:     <netfilter-devel@...r.kernel.org>, <davem@...emloft.net>,
        <netdev@...r.kernel.org>, <jakub.kicinski@...ronome.com>,
        <jiri@...nulli.us>, <vladbu@...lanox.com>
Subject: Re: [PATCH net-next 1/2] net: flow_offload: mangle 128-bit packet
 field with one action

On 20/08/2019 18:33, Pablo Neira Ayuso wrote:
> I can update tc pedit to generate one single action for offset
> consecutive packet editions, if that is the concern, I'll send a v2.
IMHO the fix belongs in TC userland (i.e. iproute2), to turn a single action on the commandline for an ipv6 addr into four pedit actions before the kernel ever sees it.
Similarly if nftables wants to use this it should generate four separate pedit actions, probably in the kernel netfilter code as (I assume) your uAPI talks in terms of named fields rather than the u32ish offsets and masks of tc pedit.
The TC (well, flow_offload now I suppose) API should be kept narrow, not widened for things that can already be expressed adequately.  Your array of words inside a pedit action looks like a kind of loop unrolling but for data structures, which doesn't look sensible to me.

-Ed