[PATCH v2 07/13] sunrpc: add a generic netlink family for cache upcalls

Jeff Layton
2026-03-25T14:41:02Z

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>
---
Documentation/netlink/specs/sunrpc_cache.yaml | 40 ++++++++++++++++++++++++
include/linux/sunrpc/cache.h | 2 ++
include/uapi/linux/sunrpc_netlink.h | 35 +++++++++++++++++++++
net/sunrpc/Makefile | 2 +-
net/sunrpc/cache.c | 44 +++++++++++++++++++++++++++
net/sunrpc/netlink.c | 34 +++++++++++++++++++++
net/sunrpc/netlink.h | 22 ++++++++++++++
net/sunrpc/sunrpc_syms.c | 10 ++++++
8 files changed, 188 insertions(+), 1 deletion(-)

diff --git a/Documentation/netlink/specs/sunrpc_cache.yaml b/Documentation/netlink/specs/sunrpc_cache.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..f4aa699598bca9ce0215bbc418d9ddcae25c0110
--- /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
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index f88dc6bb17c7078781b3cf7e0371f369eddcb563..2735c332ddb736ef043f811b5e9e6ad2f57c9ce7 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 0000000000000000000000000000000000000000..6135d9b3eef155a9192d9710c8c690283ec49073
--- /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 */
diff --git a/net/sunrpc/Makefile b/net/sunrpc/Makefile
index f89c10fe7e6acc71d47273200d85425a2891a08a..96727df3aa85435a2de63a8483eab9d75d5b3495 100644
--- a/net/sunrpc/Makefile
+++ b/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
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 1282c61030d35efd924072e2739109cfae3472e2..d477b19dbfa15fdff71f946ade2643b56c35d491 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
@@ -1960,3 +1962,45 @@ 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);
diff --git a/net/sunrpc/netlink.c b/net/sunrpc/netlink.c
new file mode 100644
index 0000000000000000000000000000000000000000..952de6de85e3f647ef9bc9c1e99651a247649abb
--- /dev/null
+++ b/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),
+};
diff --git a/net/sunrpc/netlink.h b/net/sunrpc/netlink.h
new file mode 100644
index 0000000000000000000000000000000000000000..74cf5183d745d778174abbbfed9514c4b6693e30
--- /dev/null
+++ b/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 */
diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index bab6cab2940524a970422b62b3fa4212c61c4f43..ab88ce46afb556cb0a397fe5c9df3901813ad01e 100644
--- a/net/sunrpc/sunrpc_syms.c
+++ b/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 @@ init_sunrpc(void)
static void __exit
cleanup_sunrpc(void)
{
+ genl_unregister_family(&sunrpc_nl_family);
rpc_sysfs_exit();
rpc_cleanup_clids();
xprt_cleanup_ids();

--
2.53.0