[PATCH bpf-next v4 0/4] bpf: support cloning sk storage on accept()

[Stanislav Fomichev <sdf@google.com>]

Currently there is no way to propagate sk storage from the listener
socket to a newly accepted one. Consider the following use case:

        fd = socket();
        setsockopt(fd, SOL_IP, IP_TOS,...);
        /* ^^^ setsockopt BPF program triggers here and saves something
         * into sk storage of the listener.
         */
        listen(fd, ...);
        while (client = accept(fd)) {
                /* At this point all association between listener
                 * socket and newly accepted one is gone. New
                 * socket will not have any sk storage attached.
                 */
        }

Let's add new BPF_F_CLONE flag that can be specified when creating
a socket storage map. This new flag indicates that map contents
should be cloned when the socket is cloned.

v4:
* drop 'goto err' in bpf_sk_storage_clone (Yonghong Song)
* add comment about race with bpf_sk_storage_map_free to the
  bpf_sk_storage_clone side as well (Daniel Borkmann)

v3:
* make sure BPF_F_NO_PREALLOC is always present when creating
  a map (Martin KaFai Lau)
* don't call bpf_sk_storage_free explicitly, rely on
  sk_free_unlock_clone to do the cleanup (Martin KaFai Lau)

v2:
* remove spinlocks around selem_link_map/sk (Martin KaFai Lau)
* BPF_F_CLONE on a map, not selem (Martin KaFai Lau)
* hold a map while cloning (Martin KaFai Lau)
* use BTF maps in selftests (Yonghong Song)
* do proper cleanup selftests; don't call close(-1) (Yonghong Song)
* export bpf_map_inc_not_zero

Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Yonghong Song <yhs@fb.com>

Stanislav Fomichev (4):
  bpf: export bpf_map_inc_not_zero
  bpf: support cloning sk storage on accept()
  bpf: sync bpf.h to tools/
  selftests/bpf: add sockopt clone/inheritance test

 include/linux/bpf.h                           |   2 +
 include/net/bpf_sk_storage.h                  |  10 +
 include/uapi/linux/bpf.h                      |   3 +
 kernel/bpf/syscall.c                          |  16 +-
 net/core/bpf_sk_storage.c                     | 104 ++++++-
 net/core/sock.c                               |   9 +-
 tools/include/uapi/linux/bpf.h                |   3 +
 tools/testing/selftests/bpf/.gitignore        |   1 +
 tools/testing/selftests/bpf/Makefile          |   3 +-
 .../selftests/bpf/progs/sockopt_inherit.c     |  97 +++++++
 .../selftests/bpf/test_sockopt_inherit.c      | 253 ++++++++++++++++++
 11 files changed, 491 insertions(+), 10 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/sockopt_inherit.c
 create mode 100644 tools/testing/selftests/bpf/test_sockopt_inherit.c

-- 
2.23.0.rc1.153.gdeed80330f-goog