netdev - Re: [PATCH net-next,v3 0/4] flow_offload: update mangle action representation

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Message-ID: <679ced4b-8bcd-5479-2773-7c75452c2a32@solarflare.com>
Date:   Fri, 6 Sep 2019 11:02:18 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        <netfilter-devel@...r.kernel.org>
CC:     <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <jakub.kicinski@...ronome.com>, <jiri@...nulli.us>,
        <saeedm@...lanox.com>, <vishal@...lsio.com>, <vladbu@...lanox.com>
Subject: Re: [PATCH net-next,v3 0/4] flow_offload: update mangle action
 representation

On 06/09/2019 01:03, Pablo Neira Ayuso wrote:
> This patch updates the mangle action representation:
>
> Patch 1) Undo bitwise NOT operation on the mangle mask (coming from tc
>          pedit userspace).
>
> Patch 2) mangle value &= mask from the front-end side.
>
> Patch 3) adjust offset, length and coalesce consecutive pedit keys into
>          one single action.
>
> Patch 4) add support for payload mangling for netfilter.
>
> After this patchset:
>
> * Offset to payload does not need to be on the 32-bits boundaries anymore.
>   This patchset adds front-end code to adjust the offset and length coming
>   from the tc pedit representation, so drivers get an exact header field
>   offset and length.
>
> * This new front-end code coalesces consecutive pedit actions into one
>   single action, so drivers can mangle IPv6 and ethernet address fields
>   in one go, instead once for each 32-bit word.
>
> On the driver side, diffstat -t shows that drivers code to deal with
> payload mangling gets simplified:
>
>         INSERTED,DELETED,MODIFIED,FILENAME
>         46,116,0,drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c (-70 LOC)
>         12,28,0,drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.h (-16 LOC)
> 	26,54,0,drivers/net/ethernet/mellanox/mlx5/core/en_tc.c (-27 LOC)
>         89,111,0,drivers/net/ethernet/netronome/nfp/flower/action.c (-17 LOC)
>
> While, on the front-end side the balance is the following:
>
>         123,22,0,net/sched/cls_api.c (+101 LOC)
>
> Changes since v2:
>
> * Fix is_action_keys_supported() breakage in mlx5 reported by Vlad Buslov.
Still NAK for the same reasons as three versions ago (when it was called
 "netfilter: payload mangling offload support"), you've never managed to
 explain why this extra API complexity is useful.  (Reducing LOC does not
 mean you've reduced complexity.)

As Jakub said, 'We suffered through enough haphazard "updates"'.  Please
 can you fix the problems your previous API changes caused (I still haven't
 had an answer about the flow block changes since sending you my driver code
 two weeks ago) before trying to ram new ones through.

-Ed