[PATCH v2 0/8] io_uring: Initial support for {s,g}etsockopt commands

[Breno Leitao <leitao@debian.org>]

This patchset adds support for getsockopt (SOCKET_URING_OP_GETSOCKOPT)
and setsockopt (SOCKET_URING_OP_SETSOCKOPT) in io_uring commands.
SOCKET_URING_OP_SETSOCKOPT implements generic case, covering all levels
nad optnames. On the other hand, SOCKET_URING_OP_GETSOCKOPT just
implements level SOL_SOCKET case, which seems to be the
most common level parameter for get/setsockopt(2).

struct proto_ops->setsockopt() uses sockptr instead of userspace
pointers, which makes it easy to bind to io_uring. Unfortunately
proto_ops->getsockopt() callback uses userspace pointers, except for
SOL_SOCKET, which is handled by sk_getsockopt(). Thus, this patchset
leverages sk_getsockopt() to imlpement the SOCKET_URING_OP_GETSOCKOPT
case.

In order to support BPF hooks, I modified the hooks to use  sockptr, so,
it is flexible enough to accept user or kernel pointers for
optval/optlen.

PS1: For getsockopt command, the optlen field is not a userspace
pointers, but an absolute value, so this is slightly different from
getsockopt(2) behaviour. The new optlen value is returned in cqe->res.

PS2: The userspace pointers need to be alive until the operation is
completed.

These changes were tested with a new test[1] in liburing. On the BPF
side, I tested that no regression was introduced by running "test_progs"
self test using "sockopt" test case.

[1] Link: https://github.com/leitao/liburing/blob/getsock/test/socket-getsetsock-cmd.c

RFC -> V1:
	* Copy user memory at io_uring subsystem, and call proto_ops
	  callbacks using kernel memory
	* Implement all the cases for SOCKET_URING_OP_SETSOCKOPT
V1 -> V2
	* Implemented the BPF part
	* Using user pointers from optval to avoid kmalloc in io_uring part.

Breno Leitao (8):
  net: expose sock_use_custom_sol_socket
  io_uring/cmd: Introduce SOCKET_URING_OP_GETSOCKOPT
  io_uring/cmd: Introduce SOCKET_URING_OP_SETSOCKOPT
  io_uring/cmd: Extend support beyond SOL_SOCKET
  bpf: Leverage sockptr_t in BPF getsockopt hook
  bpf: Leverage sockptr_t in BPF setsockopt hook
  io_uring/cmd: BPF hook for getsockopt cmd
  io_uring/cmd: BPF hook for setsockopt cmd

 include/linux/bpf-cgroup.h    |  7 +--
 include/linux/net.h           |  5 +++
 include/uapi/linux/io_uring.h |  8 ++++
 io_uring/uring_cmd.c          | 82 +++++++++++++++++++++++++++++++++++
 kernel/bpf/cgroup.c           | 25 ++++++-----
 net/socket.c                  | 12 ++---
 6 files changed, 117 insertions(+), 22 deletions(-)

-- 
2.34.1