netdev - Re: [PATCH bpf-next] net-bpf: bpf_skb_change_proto()

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Date:   Fri, 26 Nov 2021 18:32:10 -0800
From:   Song Liu <song@...nel.org>
To:     Maciej Żenczykowski <zenczykowski@...il.com>
Cc:     Maciej Żenczykowski <maze@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Linux Network Development Mailing List 
        <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        BPF Mailing List <bpf@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH bpf-next] net-bpf: bpf_skb_change_proto() - add support
 for ipv6 fragments

On Tue, Nov 23, 2021 at 3:06 PM Maciej Żenczykowski
<zenczykowski@...il.com> wrote:
>
> From: Maciej Żenczykowski <maze@...gle.com>
>
> IPv4 fragments (20 byte IPv4 header) need to be translated to/from
> IPv6 fragments (40 byte IPv6 header with additional 8 byte IPv6
> fragmentation header).
>
> This allows this to be done by adding an extra flag BPF_F_IPV6_FRAGMENT
> to bpf_skb_change_proto().
>
> I think this is already technically achievable via the use of
> bpf_skb_adjust_room() which was added in v4.12 commit 2be7e212d541,
> but this is far easier to use and eliminates the need to call two
> helper functions, so it's also faster.
>
> Cc: Lorenzo Colitti <lorenzo@...gle.com>
> Signed-off-by: Maciej Żenczykowski <maze@...gle.com>

Please add a selftest to exercise the new flag.

Thanks,
Song