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

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 <redacted>
---
 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 */
+ };