[PATCH 0/3] 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
and 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 implement the SOCKET_URING_OP_GETSOCKOPT
case.

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.

This patch was tested with a new test[1] in liburing.
This patch depends on "io_uring: Add io_uring command support for sockets"[2]

[1] Link: https://github.com/leitao/liburing/blob/getsock/test/socket-getsetsock-cmd.c
[2] Link: https://lore.kernel.org/all/20230627134424.2784797-1-leitao@debian.org/

Changes from RFC:
	* Copy user memory at io_uring subsystem, and call proto_ops
	  callbacks using kernel memory
	* Implement all the cases for SOCKET_URING_OP_SETSOCKOPT

Breno Leitao (4):
  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

 include/linux/net.h           |  5 +++
 include/uapi/linux/io_uring.h |  8 ++++
 io_uring/uring_cmd.c          | 81 +++++++++++++++++++++++++++++++++++
 net/socket.c                  |  5 ---
 4 files changed, 94 insertions(+), 5 deletions(-)

-- 
2.34.1