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

[Ilia Lin]

On Sun, Nov 24, 2024 at 2:04 PM Leon Romanovsky <leon@xxxxxxxxxx> 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