netlink: specs: add OVS packet family specification

Add YAML netlink spec for the OVS_PACKET_FAMILY (ovs_packet).
This completes the set of OVS genetlink family specs (ovs_datapath,
ovs_flow, ovs_vport already exist).

The spec defines three operations: MISS (event), ACTION (event),
and EXECUTE (do). MISS and ACTION are kernel-to-userspace upcalls
sent via genlmsg_unicast(); EXECUTE is the only registered genl
operation.

Key, actions, and egress-tun-key attributes are typed as binary
rather than nest because the nested attribute definitions belong
to the ovs_flow spec and cross-spec references are not supported
by the YNL framework.

Signed-off-by: Minxi Hou <houminxi@gmail.com>
Link: https://patch.msgid.link/20260522174154.720293-2-houminxi@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/ovs_packet.yaml

@@ -0,0 +1,130 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+---
+name: ovs_packet
+version: 1
+protocol: genetlink-legacy
+uapi-header: linux/openvswitch.h
+
+doc: |
+  OVS packet execution over generic netlink.
+
+  Only OVS_PACKET_CMD_EXECUTE is exposed as a genl operation.
+  OVS_PACKET_CMD_MISS and OVS_PACKET_CMD_ACTION are kernel-to-userspace
+  upcalls sent via genlmsg_unicast() to the vport's upcall_pid and have
+  no associated genl_ops or multicast group.
+
+  Several attributes in the attribute set (userdata, egress-tun-key, len)
+  exist for the upcall path and are not used by the EXECUTE operation.
+  For EXECUTE, packet, key, and actions are mandatory (kernel returns
+  -EINVAL without them).
+
+definitions:
+  -
+    name: ovs-header
+    type: struct
+    members:
+      -
+        name: dp-ifindex
+        type: u32
+
+attribute-sets:
+  -
+    name: packet
+    name-prefix: ovs-packet-attr-
+    enum-name: ovs-packet-attr
+    attributes:
+      -
+        name: packet
+        type: binary
+        doc: Packet data, from the start of the Ethernet header.
+        checks:
+          min-len: 14
+      -
+        name: key
+        type: binary
+        doc: |
+          Nested OVS_KEY_ATTR_* attributes, extracted flow key.
+          Defined as binary because the key attribute-set belongs to the
+          ovs_flow family spec; cross-spec references are not supported.
+      -
+        name: actions
+        type: binary
+        doc: |
+          Nested OVS_ACTION_ATTR_* attributes.
+          Defined as binary for the same reason as key.
+      -
+        name: userdata
+        type: binary
+        doc: Opaque userspace cookie from OVS_USERSPACE_ATTR_USERDATA.
+      -
+        name: egress-tun-key
+        type: binary
+        doc: Nested OVS_TUNNEL_KEY_ATTR_* for output tunnel metadata.
+      -
+        name: unused1
+        type: unused
+      -
+        name: unused2
+        type: unused
+      -
+        name: probe
+        type: flag
+        doc: Packet operation is a feature probe, error logging suppressed.
+      -
+        name: mru
+        type: u16
+        doc: Maximum received IP fragment size.
+      -
+        name: len
+        type: u32
+        doc: Packet size before truncation.
+      -
+        name: hash
+        type: u64
+        doc: Packet hash, low 32 bits are skb hash, upper bits are flags.
+      -
+        name: upcall-pid
+        type: u32
+        doc: Netlink PID to use for upcalls during EXECUTE processing.
+
+operations:
+  fixed-header: ovs-header
+  name-prefix: ovs-packet-cmd-
+  list:
+    -
+      name: miss
+      doc: Notify userspace of a flow table miss for a received packet.
+      value: 1
+      attribute-set: packet
+      event:
+        attributes: &event-attrs
+          - packet
+          - key
+          - userdata
+          - actions
+          - egress-tun-key
+          - mru
+          - len
+          - hash
+    -
+      name: action
+      doc: Notify userspace as requested by an OVS_ACTION_ATTR_USERSPACE action.
+      value: 2
+      attribute-set: packet
+      event:
+        attributes: *event-attrs
+    -
+      name: execute
+      doc: Apply actions to a packet.
+      value: 3
+      attribute-set: packet
+      do:
+        request:
+          attributes:
+            - packet
+            - key
+            - actions
+            - probe
+            - mru
+            - hash
+            - upcall-pid