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>

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

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);

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 */

net/sunrpc/Makefile

@@ -14,7 +14,7 @@ sunrpc-y := clnt.o xprt.o socklib.o xprtsock.o sched.o \
 	    addr.o rpcb_clnt.o timer.o xdr.o \
 	    sunrpc_syms.o cache.o rpc_pipe.o sysfs.o \
 	    svc_xprt.o \
-	    xprtmultipath.o
+	    xprtmultipath.o netlink.o
 sunrpc-$(CONFIG_SUNRPC_DEBUG) += debugfs.o
 sunrpc-$(CONFIG_SUNRPC_BACKCHANNEL) += backchannel_rqst.o
 sunrpc-$(CONFIG_PROC_FS) += stats.o

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);

net/sunrpc/netlink.c

@@ -0,0 +1,34 @@
+// 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 kernel source */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+#include <linux/sunrpc/cache.h>
+
+#include "netlink.h"
+
+#include <uapi/linux/sunrpc_netlink.h>
+
+/* Ops table for sunrpc */
+static const struct genl_split_ops sunrpc_nl_ops[] = {
+};
+
+static const struct genl_multicast_group sunrpc_nl_mcgrps[] = {
+	[SUNRPC_NLGRP_NONE] = { "none", },
+	[SUNRPC_NLGRP_EXPORTD] = { "exportd", },
+};
+
+struct genl_family sunrpc_nl_family __ro_after_init = {
+	.name		= SUNRPC_FAMILY_NAME,
+	.version	= SUNRPC_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= sunrpc_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(sunrpc_nl_ops),
+	.mcgrps		= sunrpc_nl_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(sunrpc_nl_mcgrps),
+};

net/sunrpc/netlink.h

@@ -0,0 +1,22 @@
+/* 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 kernel header */
+/* To regenerate run: tools/net/ynl/ynl-regen.sh */
+
+#ifndef _LINUX_SUNRPC_GEN_H
+#define _LINUX_SUNRPC_GEN_H
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include <uapi/linux/sunrpc_netlink.h>
+
+enum {
+	SUNRPC_NLGRP_NONE,
+	SUNRPC_NLGRP_EXPORTD,
+};
+
+extern struct genl_family sunrpc_nl_family;
+
+#endif /* _LINUX_SUNRPC_GEN_H */

net/sunrpc/sunrpc_syms.c

@@ -23,9 +23,12 @@
 #include <linux/sunrpc/rpc_pipe_fs.h>
 #include <linux/sunrpc/xprtsock.h>
 
+#include <net/genetlink.h>
+
 #include "sunrpc.h"
 #include "sysfs.h"
 #include "netns.h"
+#include "netlink.h"
 
 unsigned int sunrpc_net_id;
 EXPORT_SYMBOL_GPL(sunrpc_net_id);
@@ -108,6 +111,10 @@ init_sunrpc(void)
 	if (err)
 		goto out5;
 
+	err = genl_register_family(&sunrpc_nl_family);
+	if (err)
+		goto out6;
+
 	sunrpc_debugfs_init();
 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 	rpc_register_sysctl();
@@ -116,6 +123,8 @@ init_sunrpc(void)
 	init_socket_xprt();	/* clnt sock transport */
 	return 0;
 
+out6:
+	rpc_sysfs_exit();
 out5:
 	unregister_rpc_pipefs();
 out4:
@@ -131,6 +140,7 @@ out:
 static void __exit
 cleanup_sunrpc(void)
 {
+	genl_unregister_family(&sunrpc_nl_family);
 	rpc_sysfs_exit();
 	rpc_cleanup_clids();
 	xprt_cleanup_ids();