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Subject: Re: [net-next,v1,1/5] vrf: add mac header for tunneled packets when
 sniffer is attached
To:     Andrea Mayer <andrea.mayer@uniroma2.it>,
        "David S. Miller" <davem@davemloft.net>,
        David Ahern <dsahern@kernel.org>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Shrijeet Mukherjee <shrijeet@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@chromium.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org
Cc:     Stefano Salsano <stefano.salsano@uniroma2.it>,
        Paolo Lungaroni <paolo.lungaroni@cnit.it>,
        Ahmed Abdelsalam <ahabdels.dev@gmail.com>
References: <20201103125242.11468-1-andrea.mayer@uniroma2.it>
 <20201103125242.11468-2-andrea.mayer@uniroma2.it>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <bf69c702-db2f-b9f2-148e-17a325a3cbda@gmail.com>
Date:   Tue, 3 Nov 2020 15:39:50 -0700
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On 11/3/20 5:52 AM, Andrea Mayer wrote:
> Before this patch, a sniffer attached to a VRF used as the receiving
> interface of L3 tunneled packets detects them as malformed packets and
> it complains about that (i.e.: tcpdump shows bogus packets).
> 
> The reason is that a tunneled L3 packet does not carry any L2
> information and when the VRF is set as the receiving interface of a
> decapsulated L3 packet, no mac header is currently set or valid.
> Therefore, the purpose of this patch consists of adding a MAC header to
> any packet which is directly received on the VRF interface ONLY IF:
> 
>  i) a sniffer is attached on the VRF and ii) the mac header is not set.
> 
> In this case, the mac address of the VRF is copied in both the
> destination and the source address of the ethernet header. The protocol
> type is set either to IPv4 or IPv6, depending on which L3 packet is
> received.
> 
> Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
> ---
>  drivers/net/vrf.c | 78 +++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 72 insertions(+), 6 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>