Introduce a new helper function, `sk_set_prio_allowed`,
to centralize the logic for validating priority settings.
Add support for the `SO_PRIORITY` control message,
enabling user-space applications to set socket priority 
via control messages (cmsg).

Patch Overview:

Patch 1/3: Introduce `sk_set_prio_allowed` helper function.
Patch 2/3: Add support for setting `SO_PRIORITY` via control messages
Patch 3/3: Add test for SO_PRIORITY setting via control messages

v3:

- Updated cover letter text.
- Removed priority field from ipcm_cookie.
- Removed cork->tos value check from ip_setup_cork, so
  cork->priority will now take its value from ipc->sockc.priority.
- Replaced ipc->priority with ipc->sockc.priority
  in ip_cmsg_send().
- Modified the error handling for the SO_PRIORITY
  case in __sock_cmsg_send().
- Added missing initialization for ipc6.sockc.priority.
- Introduced cmsg_so_priority.sh test script.
- Modified cmsg_sender.c to set priority via control message (cmsg).
- Rebased on net-next

v2:

https://lore.kernel.org/netdev/20241102125136.5030-1-annaemesenyiri@gmail.com/ (local)
- Introduced sk_set_prio_allowed helper to check capability
  for setting priority.
- Removed new fields and changed sockcm_cookie::priority
  from char to u32 to align with sk_buff::priority.
- Moved the cork->tos value check for priority setting
  from __ip_make_skb() to ip_setup_cork().
- Rebased on net-next.

v1:

https://lore.kernel.org/all/20241029144142.31382-1-annaemesenyiri@gmail.com/ (local)


Anna Emese Nyiri (3):
  Introduce sk_set_prio_allowed helper function
  support SO_PRIORITY cmsg
  test SO_PRIORITY ancillary data with cmsg_sender

 include/net/inet_sock.h                       |   2 +-
 include/net/ip.h                              |   2 +-
 include/net/sock.h                            |   4 +-
 net/can/raw.c                                 |   2 +-
 net/core/sock.c                               |  18 ++-
 net/ipv4/ip_output.c                          |   4 +-
 net/ipv4/ip_sockglue.c                        |   2 +-
 net/ipv4/raw.c                                |   2 +-
 net/ipv6/ip6_output.c                         |   3 +-
 net/ipv6/raw.c                                |   3 +-
 net/ipv6/udp.c                                |   1 +
 net/packet/af_packet.c                        |   2 +-
 tools/testing/selftests/net/cmsg_sender.c     |  11 +-
 .../testing/selftests/net/cmsg_so_priority.sh | 115 ++++++++++++++++++
 14 files changed, 156 insertions(+), 15 deletions(-)
 create mode 100755 tools/testing/selftests/net/cmsg_so_priority.sh

-- 
2.43.0