netdev - Re: [PATCH bpf] bpf: only adjust gso

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Message-ID: <20190211040056.zqgi5qii26wtfs7i@ast-mbp>
Date:   Sun, 10 Feb 2019 20:00:57 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     netdev@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        posk.devel@...il.com, dja@...ens.net,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH bpf] bpf: only adjust gso_size on bytestream protocols

On Thu, Feb 07, 2019 at 02:54:16PM -0500, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@...gle.com>
> 
> bpf_skb_change_proto and bpf_skb_adjust_room change skb header length.
> For GSO packets they adjust gso_size to maintain the same MTU.
> 
> The gso size can only be safely adjusted on bytestream protocols.
> Commit d02f51cbcf12 ("bpf: fix bpf_skb_adjust_net/bpf_skb_proto_xlat
> to deal with gso sctp skbs") excluded SKB_GSO_SCTP.
> 
> Since then type SKB_GSO_UDP_L4 has been added, whose contents are one
> gso_size unit per datagram. Also exclude these.
> 
> Move from a blacklist to a whitelist check to future proof against
> additional such new GSO types, e.g., for fraglist based GRO.
> 
> Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Applied to bpf tree.
I agree that whitelist approach is the most appropriate.