Re: [PATCH bpf-next 1/2] bpf: Add flag BPF_F_NO_TUNNEL_KEY to bpf_skb_set_tunnel_key()

[Jakub Sitnicki]

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@xxxxxxxxxxxxxx>
> ---

Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>