linux-kernel - Re: [PATCH] xfrm: Add pre-encap fragmentation for packet offload

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Message-ID: <CA+5LGR2n-jCyGbLy9X5wQoUT5OXPkAc3nOr9bURO6=9ObEZVnA@mail.gmail.com>
Date: Mon, 25 Nov 2024 11:26:14 +0200
From: Ilia Lin <ilia.lin@...nel.org>
To: Leon Romanovsky <leon@...nel.org>
Cc: Ilia Lin <ilia.lin@...nel.org>, steffen.klassert@...unet.com, 
	herbert@...dor.apana.org.au, davem@...emloft.net, dsahern@...nel.org, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfrm: Add pre-encap fragmentation for packet offload

On Sun, Nov 24, 2024 at 2:04 PM Leon Romanovsky <leon@...nel.org> wrote:
>
> On Sun, Nov 24, 2024 at 11:35:31AM +0200, Ilia Lin wrote:
> > In packet offload mode the raw packets will be sent to the NiC,
> > and will not return to the Network Stack. In event of crossing
> > the MTU size after the encapsulation, the NiC HW may not be
> > able to fragment the final packet.
>
> Yes, HW doesn't know how to handle these packets.
>
> > Adding mandatory pre-encapsulation fragmentation for both
> > IPv4 and IPv6, if tunnel mode with packet offload is configured
> > on the state.
>
> I was under impression is that xfrm_dev_offload_ok() is responsible to
> prevent fragmentation.
> https://elixir.bootlin.com/linux/v6.12/source/net/xfrm/xfrm_device.c#L410

With my change we can both support inner fragmentation or prevent it,
depending on the network device driver implementation.

>
> Thanks