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Message-ID: <87edsvjdaz.fsf@cloudflare.com>
Date: Mon, 19 Dec 2022 22:24:39 +0100
From: Jakub Sitnicki <jakub@...udflare.com>
To: Christian Ehrig <cehrig@...udflare.com>
Cc: bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
Joanne Koong <joannelkoong@...il.com>,
Kui-Feng Lee <kuifeng@...com>,
Maxim Mikityanskiy <maximmi@...dia.com>,
Kaixi Fan <fankaixi.li@...edance.com>,
Shmulik Ladkani <shmulik@...anetworks.com>,
Paul Chaignon <paul@...valent.com>,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next 1/2] bpf: Add flag BPF_F_NO_TUNNEL_KEY to
bpf_skb_set_tunnel_key()
On Sun, Dec 18, 2022 at 06:17 AM +01, Christian Ehrig wrote:
> This patch allows to remove TUNNEL_KEY from the tunnel flags bitmap
> when using bpf_skb_set_tunnel_key by providing a BPF_F_NO_TUNNEL_KEY
> flag. On egress, the resulting tunnel header will not contain a tunnel
> key if the protocol and implementation supports it.
>
> At the moment bpf_tunnel_key wants a user to specify a numeric tunnel
> key. This will wrap the inner packet into a tunnel header with the key
> bit and value set accordingly. This is problematic when using a tunnel
> protocol that supports optional tunnel keys and a receiving tunnel
> device that is not expecting packets with the key bit set. The receiver
> won't decapsulate and drop the packet.
>
> RFC 2890 and RFC 2784 GRE tunnels are examples where this flag is
> useful. It allows for generating packets, that can be decapsulated by
> a GRE tunnel device not operating in collect metadata mode or not
> expecting the key bit set.
>
> Signed-off-by: Christian Ehrig <cehrig@...udflare.com>
> ---
Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>
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