sunrpc: add a generic netlink family for cache upcalls

The auth.unix.ip and auth.unix.gid caches live in the sunrpc module,
so they cannot use the nfsd generic netlink family. Create a new
"sunrpc" generic netlink family with its own "exportd" multicast
group to support cache upcall notifications for sunrpc-resident
caches.

Define a YAML spec (sunrpc_cache.yaml) with a cache-type enum
(ip_map, unix_gid), a cache-notify multicast event, and the
corresponding uapi header.

Implement sunrpc_cache_notify() in cache.c, which checks for
listeners on the exportd multicast group, builds and sends a
SUNRPC_CMD_CACHE_NOTIFY message with the cache-type attribute.

Register/unregister the sunrpc_nl_family in init_sunrpc() and
cleanup_sunrpc().

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/Documentation/netlink/specs/sunrpc_cache.yaml b/Documentation/netlink/specs/sunrpc_cache.yaml
new file mode 100644
index 000000000000..f4aa699598bc
--- /dev/null
+++ b/Documentation/netlink/specs/sunrpc_cache.yaml
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+---
+name: sunrpc
+protocol: genetlink
+uapi-header: linux/sunrpc_netlink.h
+
+doc: SUNRPC cache upcall support over generic netlink.
+
+definitions:
+  -
+    type: flags
+    name: cache-type
+    entries: [ip_map, unix_gid]
+
+attribute-sets:
+  -
+    name: cache-notify
+    attributes:
+      -
+        name: cache-type
+        type: u32
+        enum: cache-type
+
+operations:
+  list:
+    -
+      name: cache-notify
+      doc: Notification that there are cache requests that need servicing
+      attribute-set: cache-notify
+      mcgrp: exportd
+      event:
+        attributes:
+          - cache-type
+
+mcast-groups:
+  list:
+    -
+      name: none
+    -
+      name: exportd