Merge branch 'bpf-proto-fixes'

Willem de Bruijn says:

====================
Expand the tc tunnel encap support with protocols that convert the
network layer protocol, such as 6in4. This is analogous to existing
support in bpf_skb_proto_6_to_4.

Patch 1 implements the straightforward logic
Patch 2 tests it with a 6in4 tunnel

Changes v1->v2
  - improve documentation in test
====================

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