Merge branch 'Get ingress_ifindex in BPF_SK_LOOKUP prog type'

Mark Pashmfouroush says:

====================

BPF_SK_LOOKUP users may want to have access to the ifindex of the skb
which triggered the socket lookup. This may be useful for selectively
applying programmable socket lookup logic to packets that arrive on a
specific interface, or excluding packets from an interface.

v3:
- Rename ifindex field to ingress_ifindex for consistency. (Yonghong)

v2:
- Fix inaccurate comment (Alexei)
- Add more details to commit messages (John)
====================

Revieview-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>