Merge branch 'skb_sk-sk_fullsock-tcp_sock'

Martin KaFai Lau says:

====================
This series adds __sk_buff->sk, "struct bpf_tcp_sock",
BPF_FUNC_sk_fullsock and BPF_FUNC_tcp_sock.  Together, they provide
a common way to expose the members of "struct tcp_sock" and
"struct bpf_sock" for the bpf_prog to access.

The patch series first adds a bpf_sock pointer to __sk_buff
and a new helper BPF_FUNC_sk_fullsock.

It then adds BPF_FUNC_tcp_sock to get a bpf_tcp_sock
pointer from a bpf_sock pointer.

The current use case is to allow a cg_skb_bpf_prog to provide
per cgroup traffic policing/shaping.

Please see individual patch for details.

v2:
- Patch 1 depends on
  commit d623876646be ("bpf: Fix narrow load on a bpf_sock returned from sk_lookup()")
  in the bpf branch.
- Add sk_to_full_sk() to bpf_sk_fullsock() and bpf_tcp_sock()
  such that there is a way to access the listener's sk and tcp_sk
  when __sk_buff->sk is a request_sock.
  The comments in the uapi bpf.h is updated accordingly.
- bpf_ctx_range_till() is used in bpf_sock_common_is_valid_access()
  in patch 1.  Saved a few lines.
- Patch 2 is new in v2 and it adds "state", "dst_ip4", "dst_ip6" and
  "dst_port" to the bpf_sock.  Narrow load is allowed on them.
  The "state" (i.e. sk_state) has already been used in
  INET_DIAG (e.g. ss -t) and getsockopt(TCP_INFO).
- While at it in the new patch 2, also allow narrow load on some
  existing fields of the bpf_sock, which are "family", "type", "protocol"
  and "src_port".  Only allow loading from first byte for now.
  i.e. does not allow narrow load starting from the 2nd byte.
- Add some narrow load tests to the test_verifier's sock.c
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>