Merge branch 'bpf-ancestor-cgroup-id'

Andrey Ignatov says:

====================
This patch set adds new BPF helper bpf_skb_ancestor_cgroup_id that returns
id of cgroup v2 that is ancestor of cgroup associated with the skb at the
ancestor_level.

The helper is useful to implement policies in TC based on cgroups that are
upper in hierarchy than immediate cgroup associated with skb.

v1->v2:
- more reliable check for testing IPv6 to become ready in selftest.
====================

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