Re: [net-next,v2,1/5] vrf: add mac header for tunneled packets when sniffer is attached

From: Andrea Mayer <andrea.mayer@uniroma2.it>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>,
	David Ahern <dsahern@kernel.org>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.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,
	Stefano Salsano <stefano.salsano@uniroma2.it>,
	Paolo Lungaroni <paolo.lungaroni@cnit.it>,
	Ahmed Abdelsalam <ahabdels.dev@gmail.com>,
	Andrea Mayer <andrea.mayer@uniroma2.it>
Subject: Re: [net-next,v2,1/5] vrf: add mac header for tunneled packets when sniffer is attached
Date: Fri, 13 Nov 2020 01:37:52 +0100	[thread overview]
Message-ID: <20201113013752.ea050bf062d45744500d42d8@uniroma2.it> (raw)
In-Reply-To: <20201110145045.22dfd58e@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

Hi Jakub,

On Tue, 10 Nov 2020 14:50:45 -0800
Jakub Kicinski <kuba@kernel.org> wrote:

> On Sat,  7 Nov 2020 16:31:35 +0100 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>
> 
> Please keep David's review tag since you haven't changed the code.

I will keep David's review tag in v3.

Thanks,
Andrea