[PATCH v2 bpf-next 0/4] bpf: tcp: Allow bpf-tcp-cc to call bpf_(get|set)sockopt

[Martin KaFai Lau <kafai@fb.com>]

This set allows the bpf-tcp-cc to call bpf_setsockopt.  One use
case is to allow a bpf-tcp-cc switching to another cc during init().
For example, when the tcp flow is not ecn ready, the bpf_dctcp
can switch to another cc by calling setsockopt(TCP_CONGESTION).

bpf_getsockopt() is also added to have a symmetrical API, so
less usage surprise.
    
v2:
- Not allow switching to kernel's tcp_cdg because it is the only
  kernel tcp-cc that stores a pointer to icsk_ca_priv.
  Please see the commit log in patch 1 for details.
  Test is added in patch 4 to check switching to tcp_cdg.
- Refactor the logic finding the offset of a func ptr
  in the "struct tcp_congestion_ops" to prog_ops_moff()
  in patch 1.
- bpf_setsockopt() has been disabled in release() since v1 (please
  see commit log in patch 1 for reason).  bpf_getsockopt() is
  also disabled together in release() in v2 to avoid usage surprise
  because both of them are usually expected to be available together.
  bpf-tcp-cc can already use PTR_TO_BTF_ID to read from tcp_sock.

Martin KaFai Lau (4):
  bpf: tcp: Allow bpf-tcp-cc to call bpf_(get|set)sockopt
  bpf: selftests: Add sk_state to bpf_tcp_helpers.h
  bpf: selftests: Add connect_to_fd_opts to network_helpers
  bpf: selftests: Add dctcp fallback test

 kernel/bpf/bpf_struct_ops.c                   |  22 +++-
 net/core/filter.c                             |   6 +
 net/ipv4/bpf_tcp_ca.c                         |  41 ++++++-
 tools/testing/selftests/bpf/bpf_tcp_helpers.h |   1 +
 tools/testing/selftests/bpf/network_helpers.c |  23 +++-
 tools/testing/selftests/bpf/network_helpers.h |   6 +
 .../selftests/bpf/prog_tests/bpf_tcp_ca.c     | 106 ++++++++++++++----
 .../selftests/bpf/prog_tests/kfunc_call.c     |   2 +-
 tools/testing/selftests/bpf/progs/bpf_dctcp.c |  25 +++++
 .../selftests/bpf/progs/bpf_dctcp_release.c   |  26 +++++
 .../bpf/progs/kfunc_call_test_subprog.c       |   4 +-
 11 files changed, 230 insertions(+), 32 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_dctcp_release.c

-- 
2.30.2