Merge branch 'bpf-fib-lookup-helper'

David Ahern says:

====================
Provide a helper for doing a FIB and neighbor lookup in the kernel
tables from an XDP program. The helper provides a fastpath for forwarding
packets. If the packet is a local delivery or for any reason is not a
simple lookup and forward, the packet is expected to continue up the stack
for full processing.

The response from a FIB and neighbor lookup is either the egress index
with the bpf_fib_lookup struct filled in with dmac and gateway or
0 meaning the packet should continue up the stack. In time we can
revisit this to return the FIB lookup result errno if it is one of the
special RTN_'s such as RTN_BLACKHOLE (-EINVAL) so that the XDP
programs can do an early drop if desired.

Patches 1-6 do some more refactoring to IPv6 with the end goal of
extracting a FIB lookup function that aligns with fib_lookup for IPv4,
basically returning a fib6_info without creating a dst based entry.

Patch 7 adds lookup functions to the ipv6 stub. These are needed since
bpf is built into the kernel and ipv6 may not be built or loaded.

Patch 8 adds the bpf helper and 9 adds a sample program.

v3
- remove ETH_ALEN and in6_addr from uapi header

v2
- removed pkt_access from bpf_func_proto as noticed by Daniel
- added check in that IPv6 forwarding is enabled
- added DaveM's ack on patches 1-7 and 9 based on v1 response and
  fact that no changes were made to them in v2

v1
- updated commit messages and cover letter
- added comment to sample program noting lack of verification on
  egress device supporting XDP

RFC v2
- fixed use of foward helper from cls_act as noted by Daniel
- in patch 1 rename fib6_lookup_1 as well for consistency
====================

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index 265f8e0e8ada..2375d06c706b 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -103,6 +103,9 @@ static int (*bpf_skb_get_xfrm_state)(void *ctx, int index, void *state,
 	(void *) BPF_FUNC_skb_get_xfrm_state;
 static int (*bpf_get_stack)(void *ctx, void *buf, int size, int flags) =
 	(void *) BPF_FUNC_get_stack;
+static int (*bpf_fib_lookup)(void *ctx, struct bpf_fib_lookup *params,
+			     int plen, __u32 flags) =
+	(void *) BPF_FUNC_fib_lookup;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions