wifi: nl80211: introduce PROBE_PEER for AP and STA

From: Priyansha Tiwari <priyansha.tiwari@oss.qualcomm.com>

This series introduces a unified mechanism to probe connected peers.
It generalizes the legacy AP-only PROBE_CLIENT functionality by adding
NL80211_CMD_PROBE_PEER and enabling (feature-gated) STA-side probing.
With this, AP/GO continues to probe associated stations as before, and
STA/P2P-client can probe the connected AP for faster link health checks.
For MLO connections, mac80211 supports per-link STA probing to obtain
link-specific ACK information.

Patch 1 renames NL80211_CMD_PROBE_CLIENT to NL80211_CMD_PROBE_PEER in
the UAPI enum (keeping PROBE_CLIENT as a compatibility alias) and renames
the .probe_client cfg80211_ops callback to .probe_peer. All in-tree users
(wil6210, mwifiex, mac80211) are updated so the tree builds after this
patch. This is a pure rename with no behaviour change; documentation is
intentionally left unchanged.

Patch 2 updates the @probe_peer documentation in cfg80211_ops to describe
the STA-mode semantics, adds NL80211_EXT_FEATURE_PROBE_AP to advertise
STA-side support, extends cfg80211_probe_status() to carry an optional
peer address and a link_id (-1 for non-MLO), and extends the nl80211
handler to accept STA/P2P-client interfaces when the driver advertises
the feature (MAC attribute must be omitted; the AP is implied by the
association). All callers of cfg80211_probe_status() are updated.

Patch 3 adds per-link PROBE_PEER support in mac80211 for STA/P2P-client
mode. For STA/P2P-client, it uses IEEE80211_LINK_UNSPECIFIED together
with the associated AP/GO address and lets the driver select the link.
For non-MLO connections, mac80211 still fills info->band from the
current chanctx so legacy transmissions continue to carry the correct
band information. The link_valid/link_id bitfields in
ieee80211_tx_info.status are set before transmitting and read back in
ieee80211_report_ack_skb() to report the actual link_id to userspace.
AP/GO behaviour is unchanged.

Patch 4 makes mac80211_hwsim populate link_valid/link_id in TX status
for both the direct TX status path and the wmediumd/netlink TX status
path.

---
Changes in v5:
  - Patch 3:
    * Renamed peer_addr to dst_addr for clarity.
    * Reworked ieee80211_probe_peer() to share more logic between
      AP and STA modes by using ieee80211_vif_type_p2p(),
      overriding the STA peer to the associated AP/GO address,
      and pulling the common sta lookup/qos handling out of the
      switch.
    * Kept the remaining AP/STA difference limited to the DS bits,
      while preserving the existing MLO/non-MLO address and band
      handling.

Changes in v4:
  - Patch 3:
    * Dropped guard(rcu)() from ieee80211_probe_peer() and used
      wiphy_dereference() under the already held wiphy lock.
    * Simplified STA/P2P-client probing to use
      IEEE80211_LINK_UNSPECIFIED together with the associated
      AP/GO address for both MLO and non-MLO cases.
    * Kept the non-MLO band lookup via chanctx so legacy
      transmissions still carry the correct band.
    * Return -ENOLINK when the associated AP STA entry is missing,
      instead of falling back to non-QoS probing.

Changes in v3:
  - Restructured patch split:
    * Patch 1: pure rename (probe_client -> probe_peer), no doc changes
    * Patch 2: documentation update for STA-mode semantics +
               nl80211 API logic change + cfg80211_probe_status update
    * Patch 3: mac80211 implementation
  - Removed unnecessary bitfield padding (no pad2:3)
  - Moved MAC-omission check for STA mode into cfg80211/nl80211
    (not mac80211).
  - Used switch statement in both nl80211_probe_peer() and
    ieee80211_probe_peer().
  - Used guard(rcu)() instead of manual rcu_read_lock/unlock
  - Return -ENOLINK (not -ENOTCONN) for unconnected STA, consistent
    with cfg80211 conventions

Priyansha Tiwari (4):
  wifi: nl80211/cfg80211: rename probe_client to probe_peer
  wifi: cfg80211/nl80211: add STA-mode peer probing
  wifi: mac80211: implement STA-mode peer probing
  wifi: mac80211_hwsim: report TX status link_id

 drivers/net/wireless/ath/wil6210/cfg80211.c   |  10 +-
 .../net/wireless/marvell/mwifiex/cfg80211.c   |   8 +-
 .../wireless/virtual/mac80211_hwsim_main.c    |  43 ++++++-
 include/net/cfg80211.h                        |  18 +--
 include/net/mac80211.h                        |   2 +-
 include/uapi/linux/nl80211.h                  |  23 ++--
 net/mac80211/cfg.c                            | 117 +++++++++---------
 net/mac80211/status.c                         |   5 +-
 net/wireless/nl80211.c                        |  69 +++++++----
 net/wireless/rdev-ops.h                       |  10 +-
 net/wireless/trace.h                          |   2 +-
 11 files changed, 187 insertions(+), 120 deletions(-)

-- 
2.34.1