Re: [PATCH 1/3] bpf: Add support for mark with bpf_fib_lookup

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jun 29, 2021 at 10:37:34AM -0700, Rumen Telbizov wrote:
> Add support for policy routing via marks to the bpf_fib_lookup
> helper. The bpf_fib_lookup struct is constrained to 64B for
> performance. Since the smac and dmac entries are used only for
> output, put them in an anonymous struct and then add a union
> around a second struct that contains the mark to use in the FIB
> lookup.
> 
> Signed-off-by: David Ahern <dsahern@kernel.org>
> Signed-off-by: Rumen Telbizov <telbizov@gmail.com>
> ---
>  include/uapi/linux/bpf.h | 16 ++++++++++++++--
>  net/core/filter.c        |  4 ++--
>  2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index ec6d85a81744..6c78cc9c3c75 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -5925,8 +5925,20 @@ struct bpf_fib_lookup {
>   /* output */
>   __be16 h_vlan_proto;
>   __be16 h_vlan_TCI;
> - __u8 smac[6];     /* ETH_ALEN */
> - __u8 dmac[6];     /* ETH_ALEN */
> +
> + union {
> + /* input */
> + struct {
> + __u32 mark;   /* fwmark for policy routing */
> + /* 2 4-byte holes for input */
> + };

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