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>

2 files changed, 37 insertions, 0 deletions

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index f88dc6bb17c7..2735c332ddb7 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -256,6 +256,8 @@ int sunrpc_cache_requests_snapshot(struct cache_detail *cd,
 				   struct cache_head **items,
 				   u64 *seqnos, int max,
 				   u64 min_seqno);
+int sunrpc_cache_notify(struct cache_detail *cd, struct cache_head *h,
+			u32 cache_type);
 
 /* Must store cache_detail in seq_file->private if using next three functions */
 extern void *cache_seq_start_rcu(struct seq_file *file, loff_t *pos);
diff --git a/include/uapi/linux/sunrpc_netlink.h b/include/uapi/linux/sunrpc_netlink.h
new file mode 100644
index 000000000000..6135d9b3eef1
--- /dev/null
+++ b/include/uapi/linux/sunrpc_netlink.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/sunrpc_cache.yaml */
+/* YNL-GEN uapi header */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#ifndef _UAPI_LINUX_SUNRPC_NETLINK_H
+#define _UAPI_LINUX_SUNRPC_NETLINK_H
+
+#define SUNRPC_FAMILY_NAME	"sunrpc"
+#define SUNRPC_FAMILY_VERSION	1
+
+enum sunrpc_cache_type {
+	SUNRPC_CACHE_TYPE_IP_MAP = 1,
+	SUNRPC_CACHE_TYPE_UNIX_GID = 2,
+};
+
+enum {
+	SUNRPC_A_CACHE_NOTIFY_CACHE_TYPE = 1,
+
+	__SUNRPC_A_CACHE_NOTIFY_MAX,
+	SUNRPC_A_CACHE_NOTIFY_MAX = (__SUNRPC_A_CACHE_NOTIFY_MAX - 1)
+};
+
+enum {
+	SUNRPC_CMD_CACHE_NOTIFY = 1,
+
+	__SUNRPC_CMD_MAX,
+	SUNRPC_CMD_MAX = (__SUNRPC_CMD_MAX - 1)
+};
+
+#define SUNRPC_MCGRP_NONE	"none"
+#define SUNRPC_MCGRP_EXPORTD	"exportd"
+
+#endif /* _UAPI_LINUX_SUNRPC_NETLINK_H */