Re: [PATCH bpf-next V3 2/6] bpf: bpf_fib_lookup return MTU value as output when looked up

David Ahern
2020-10-09T04:05:58Z

On 10/8/20 7:09 AM, Jesper Dangaard Brouer wrote:
> The BPF-helpers for FIB lookup (bpf_xdp_fib_lookup and bpf_skb_fib_lookup)
> can perform MTU check and return BPF_FIB_LKUP_RET_FRAG_NEEDED. The BPF-prog
> don't know the MTU value that caused this rejection.
>
> If the BPF-prog wants to implement PMTU (Path MTU Discovery) (rfc1191) it
> need to know this MTU value for the ICMP packet.
>
> Patch change lookup and result struct bpf_fib_lookup, to contain this MTU
> value as output via a union with 'tot_len' as this is the value used for
> the MTU lookup.
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
> ---
> include/uapi/linux/bpf.h | 11 +++++++++--
> net/core/filter.c | 17 ++++++++++++-----
> tools/include/uapi/linux/bpf.h | 11 +++++++++--
> 3 files changed, 30 insertions(+), 9 deletions(-)
>

Reviewed-by: David Ahern <dsahern@gmail.com>