netdev - [PATCH RFC bpf-next 0/2] bpf: Rework bpf_redirect_neigh() to allow supplying nexthop from caller

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Date:   Thu, 15 Oct 2020 17:46:47 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH RFC bpf-next 0/2] bpf: Rework bpf_redirect_neigh() to allow
 supplying nexthop from caller

Based on previous discussion[0], we determined that it would be beneficial to
rework bpf_redirect_neigh() so the caller can supply the nexthop information
(e.g., from a previous call to bpf_fib_lookup()). This way, the two helpers can
be combined without incurring a second FIB lookup to find the nexthop, and
bpf_fib_lookup() becomes usable even if no nexthop entry currently exists.

This patch (and accompanying selftest update) accomplishes this by way of an
optional paramter to bpf_redirect_neigh(). This is an API change, and so should
really be merged into the bpf tree to be part of the 5.10 cycle; however, since
bpf-next has not yet been merged into bpf, I'm sending this as an RFC against
bpf-next for discussion, and will repost against bpf once that merge happens
(Daniel, unless you have a better way of doing this, of course).

-Toke

[0] https://lore.kernel.org/bpf/393e17fc-d187-3a8d-2f0d-a627c7c63fca@iogearbox.net/

---

Toke Høiland-Jørgensen (2):
      bpf_redirect_neigh: Support supplying the nexthop as a helper parameter
      selftests: Update test_tc_neigh to use the modified bpf_redirect_neigh()

 .../selftests/bpf/progs/test_tc_neigh.c       | 83 ++++++++++++++++---
 .../testing/selftests/bpf/test_tc_redirect.sh |  8 +-
 2 files changed, 78 insertions(+), 13 deletions(-)