netdev - Re: [PATCH bpf-next v2 4/4] bpf: more lenient bpf_skb_net_shrink() with BPF_F_ADJ_ROOM_FIXED

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Message-ID: <919e8f26-4b82-9d4c-8973-b2ab2b4bc5bf@iogearbox.net>
Date:   Thu, 24 Jun 2021 16:05:35 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Maciej Żenczykowski <zenczykowski@...il.com>,
        Maciej Żenczykowski <maze@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>
Cc:     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>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH bpf-next v2 4/4] bpf: more lenient bpf_skb_net_shrink()
 with BPF_F_ADJ_ROOM_FIXED_GSO

On 6/17/21 2:09 AM, Maciej Żenczykowski wrote:
> From: Maciej Żenczykowski <maze@...gle.com>
> 
> This is to more closely match behaviour of bpf_skb_change_proto()
> which now does not adjust gso_size, and thus thoretically supports
> all gso types, and does not need to set SKB_GSO_DODGY nor reset
> gso_segs to zero.
> 
> Something similar should probably be done with bpf_skb_net_grow(),
> but that code scares me.

Took in all except this one, would be good to have a complete solution for
both bpf_skb_net_{shrink,grow}(). If you don't have the cycles, I'll look
into it.

Thanks,
Daniel