netdev - Re: [PATCH bpf 1/2] bpf: udp: ipv6: Avoid running reuseport's bpf_prog from __udp6_lib

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Message-ID: <CAEfhGiyfydP4xggD-v5DCXyM0mtaEa5oPu39WLD7o8v_DgobAA@mail.gmail.com>
Date:   Mon, 3 Jun 2019 09:07:33 -0400
From:   Craig Gallek <kraig@...gle.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     bpf@...r.kernel.org, netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf 1/2] bpf: udp: ipv6: Avoid running reuseport's
 bpf_prog from __udp6_lib_err

On Fri, May 31, 2019 at 6:29 PM Martin KaFai Lau <kafai@...com> wrote:
>
> __udp6_lib_err() may be called when handling icmpv6 message. For example,
> the icmpv6 toobig(type=2).  __udp6_lib_lookup() is then called
> which may call reuseport_select_sock().  reuseport_select_sock() will
> call into a bpf_prog (if there is one).
>
> reuseport_select_sock() is expecting the skb->data pointing to the
> transport header (udphdr in this case).  For example, run_bpf_filter()
> is pulling the transport header.
>
> However, in the __udp6_lib_err() path, the skb->data is pointing to the
> ipv6hdr instead of the udphdr.
>
> One option is to pull and push the ipv6hdr in __udp6_lib_err().
> Instead of doing this, this patch follows how the original
> commit 538950a1b752 ("soreuseport: setsockopt SO_ATTACH_REUSEPORT_[CE]BPF")
> was done in IPv4, which has passed a NULL skb pointer to
> reuseport_select_sock().
>
> Fixes: 538950a1b752 ("soreuseport: setsockopt SO_ATTACH_REUSEPORT_[CE]BPF")
> Cc: Craig Gallek <kraig@...gle.com>
> Signed-off-by: Martin KaFai Lau <kafai@...com>

Acked-by: Craig Gallek <kraig@...gle.com>