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, 44 insertions, 0 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 302bd7ccb39b..391037f15292 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -33,9 +33,11 @@
 #include <linux/sunrpc/cache.h>
 #include <linux/sunrpc/stats.h>
 #include <linux/sunrpc/rpc_pipe_fs.h>
+#include <net/genetlink.h>
 #include <trace/events/sunrpc.h>
 
 #include "netns.h"
+#include "netlink.h"
 #include "fail.h"
 
 #define	 RPCDBG_FACILITY RPCDBG_CACHE
@@ -1963,3 +1965,45 @@ int sunrpc_cache_requests_snapshot(struct cache_detail *cd,
 	return i;
 }
 EXPORT_SYMBOL_GPL(sunrpc_cache_requests_snapshot);
+
+/**
+ * sunrpc_cache_notify - send a netlink notification for a cache event
+ * @cd: cache_detail for the cache
+ * @h: cache_head entry (unused, reserved for future use)
+ * @cache_type: cache type identifier (e.g. SUNRPC_CACHE_TYPE_UNIX_GID)
+ *
+ * Sends a SUNRPC_CMD_CACHE_NOTIFY multicast message on the "exportd"
+ * group if any listeners are present. Returns 0 on success or a
+ * negative errno.
+ */
+int sunrpc_cache_notify(struct cache_detail *cd, struct cache_head *h,
+			u32 cache_type)
+{
+	struct genlmsghdr *hdr;
+	struct sk_buff *msg;
+
+	if (!genl_has_listeners(&sunrpc_nl_family, cd->net,
+				SUNRPC_NLGRP_EXPORTD))
+		return -ENOLINK;
+
+	msg = genlmsg_new(nla_total_size(sizeof(u32)), GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &sunrpc_nl_family, 0,
+			  SUNRPC_CMD_CACHE_NOTIFY);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return -ENOMEM;
+	}
+
+	if (nla_put_u32(msg, SUNRPC_A_CACHE_NOTIFY_CACHE_TYPE, cache_type)) {
+		nlmsg_free(msg);
+		return -ENOMEM;
+	}
+
+	genlmsg_end(msg, hdr);
+	return genlmsg_multicast_netns(&sunrpc_nl_family, cd->net, msg, 0,
+				       SUNRPC_NLGRP_EXPORTD, GFP_KERNEL);
+}
+EXPORT_SYMBOL_GPL(sunrpc_cache_notify);