netdev - Re: [PATCH bpf-next] bpf: test_tc_tunnel.sh needs reverse path filtering disabled

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Date:   Mon, 25 Mar 2019 09:17:02 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     Shuah Khan <shuah@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>, songliubraving@...com,
        yhs@...com, linux-kselftest@...r.kernel.org,
        Network Development <netdev@...r.kernel.org>,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next] bpf: test_tc_tunnel.sh needs reverse path
 filtering disabled

On Mon, Mar 25, 2019 at 5:36 AM Alan Maguire <alan.maguire@...cle.com> wrote:
>
> test_tc_tunnel.sh sets up a pair of namespaces connected by a
> veth pair to verify encap/decap using bpf_skb_adjust_room.  In
> testing this, it uses tunnel links as the peer of the bpf-based
> encap/decap.  However because the same IP header is used for inner
> and outer IP, when packets arrive at the tunnel interface they will
> be dropped by reverse path filtering as those packets are expected
> on the veth interface (where the destination IP of the decapped
> packet is configured).
>
> To avoid this, ensure reverse path filtering is disabled for the
> namespace using tunneling.
>
> Fixes: 98cdabcd0798 ("selftests/bpf: bpf tunnel encap test")
> Signed-off-by: Alan Maguire <alan.maguire@...cle.com>

Acked-by: Willem de Bruijn <willemb@...gle.com>

Thanks, Alan. Indeed, I had been developing on a platform with reverse
path filter off by default (debian stretch).