diff --git a/Documentation/netlink/specs/handshake.yaml b/Documentation/netlink/specs/handshake.yaml
new file mode 100644
index 000000000000..7da79aab0b8d
--- /dev/null
+++ b/Documentation/netlink/specs/handshake.yaml
@@ -0,0 +1,122 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+#
+# Author: Chuck Lever <chuck.lever@oracle.com>
+#
+# Copyright (c) 2023, Oracle and/or its affiliates.
+#
+
+name: handshake
+
+protocol: genetlink
+
+doc: Netlink protocol to request a transport layer security handshake.
+
+definitions:
+  -
+    type: enum
+    name: handler-class
+    value-start: 0
+    entries: [ none ]
+  -
+    type: enum
+    name: msg-type
+    value-start: 0
+    entries: [ unspec, clienthello, serverhello ]
+  -
+    type: enum
+    name: auth
+    value-start: 0
+    entries: [ unspec, unauth, psk, x509 ]
+
+attribute-sets:
+  -
+    name: x509
+    attributes:
+      -
+        name: cert
+        type: u32
+      -
+        name: privkey
+        type: u32
+  -
+    name: accept
+    attributes:
+      -
+        name: sockfd
+        type: u32
+      -
+        name: handler-class
+        type: u32
+        enum: handler-class
+      -
+        name: message-type
+        type: u32
+        enum: msg-type
+      -
+        name: timeout
+        type: u32
+      -
+        name: auth-mode
+        type: u32
+        enum: auth
+      -
+        name: peer-identity
+        type: u32
+        multi-attr: true
+      -
+        name: certificate
+        type: nest
+        nested-attributes: x509
+        multi-attr: true
+  -
+    name: done
+    attributes:
+      -
+        name: status
+        type: u32
+      -
+        name: sockfd
+        type: u32
+      -
+        name: remote-auth
+        type: u32
+        multi-attr: true
+
+operations:
+  list:
+    -
+      name: ready
+      doc: Notify handlers that a new handshake request is waiting
+      notify: accept
+    -
+      name: accept
+      doc: Handler retrieves next queued handshake request
+      attribute-set: accept
+      flags: [ admin-perm ]
+      do:
+        request:
+          attributes:
+            - handler-class
+        reply:
+          attributes:
+            - sockfd
+            - message-type
+            - timeout
+            - auth-mode
+            - peer-identity
+            - certificate
+    -
+      name: done
+      doc: Handler reports handshake completion
+      attribute-set: done
+      do:
+        request:
+          attributes:
+            - status
+            - sockfd
+            - remote-auth
+
+mcast-groups:
+  list:
+    -
+      name: none
diff --git a/MAINTAINERS b/MAINTAINERS
index 9faef5784c03..ff6314b4f0d7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8939,6 +8939,14 @@ Q:	http://patchwork.linuxtv.org/project/linux-media/list/
 T:	git git://linuxtv.org/anttip/media_tree.git
 F:	drivers/media/usb/hackrf/
 
+HANDSHAKE UPCALL FOR TRANSPORT LAYER SECURITY
+M:	Chuck Lever <chuck.lever@oracle.com>
+L:	netdev@vger.kernel.org
+S:	Maintained
+F:	Documentation/netlink/specs/handshake.yaml
+F:	include/trace/events/handshake.h
+F:	net/handshake/
+
 HANTRO VPU CODEC DRIVER
 M:	Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
 M:	Philipp Zabel <p.zabel@pengutronix.de>
diff --git a/include/trace/events/handshake.h b/include/trace/events/handshake.h
new file mode 100644
index 000000000000..97f0f160393b
--- /dev/null
+++ b/include/trace/events/handshake.h
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM handshake
+
+#if !defined(_TRACE_HANDSHAKE_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_HANDSHAKE_H
+
+#include <linux/net.h>
+#include <linux/tracepoint.h>
+
+DECLARE_EVENT_CLASS(handshake_event_class,
+	TP_PROTO(
+		const struct net *net,
+		const struct handshake_req *req,
+		const struct sock *sk
+	),
+	TP_ARGS(net, req, sk),
+	TP_STRUCT__entry(
+		__field(const void *, req)
+		__field(const void *, sk)
+		__field(unsigned int, netns_ino)
+	),
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->sk = sk;
+		__entry->netns_ino = net->ns.inum;
+	),
+	TP_printk("req=%p sk=%p",
+		__entry->req, __entry->sk
+	)
+);
+#define DEFINE_HANDSHAKE_EVENT(name)				\
+	DEFINE_EVENT(handshake_event_class, name,		\
+		TP_PROTO(					\
+			const struct net *net,			\
+			const struct handshake_req *req,	\
+			const struct sock *sk			\
+		),						\
+		TP_ARGS(net, req, sk))
+
+DECLARE_EVENT_CLASS(handshake_fd_class,
+	TP_PROTO(
+		const struct net *net,
+		const struct handshake_req *req,
+		const struct sock *sk,
+		int fd
+	),
+	TP_ARGS(net, req, sk, fd),
+	TP_STRUCT__entry(
+		__field(const void *, req)
+		__field(const void *, sk)
+		__field(int, fd)
+		__field(unsigned int, netns_ino)
+	),
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->sk = req->hr_sk;
+		__entry->fd = fd;
+		__entry->netns_ino = net->ns.inum;
+	),
+	TP_printk("req=%p sk=%p fd=%d",
+		__entry->req, __entry->sk, __entry->fd
+	)
+);
+#define DEFINE_HANDSHAKE_FD_EVENT(name)				\
+	DEFINE_EVENT(handshake_fd_class, name,			\
+		TP_PROTO(					\
+			const struct net *net,			\
+			const struct handshake_req *req,	\
+			const struct sock *sk,			\
+			int fd					\
+		),						\
+		TP_ARGS(net, req, sk, fd))
+
+DECLARE_EVENT_CLASS(handshake_error_class,
+	TP_PROTO(
+		const struct net *net,
+		const struct handshake_req *req,
+		const struct sock *sk,
+		int err
+	),
+	TP_ARGS(net, req, sk, err),
+	TP_STRUCT__entry(
+		__field(const void *, req)
+		__field(const void *, sk)
+		__field(int, err)
+		__field(unsigned int, netns_ino)
+	),
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->sk = sk;
+		__entry->err = err;
+		__entry->netns_ino = net->ns.inum;
+	),
+	TP_printk("req=%p sk=%p err=%d",
+		__entry->req, __entry->sk, __entry->err
+	)
+);
+#define DEFINE_HANDSHAKE_ERROR(name)				\
+	DEFINE_EVENT(handshake_error_class, name,		\
+		TP_PROTO(					\
+			const struct net *net,			\
+			const struct handshake_req *req,	\
+			const struct sock *sk,			\
+			int err					\
+		),						\
+		TP_ARGS(net, req, sk, err))
+
+
+/**
+ ** Request lifetime events
+ **/
+
+DEFINE_HANDSHAKE_EVENT(handshake_submit);
+DEFINE_HANDSHAKE_ERROR(handshake_submit_err);
+DEFINE_HANDSHAKE_EVENT(handshake_cancel);
+DEFINE_HANDSHAKE_EVENT(handshake_cancel_none);
+DEFINE_HANDSHAKE_EVENT(handshake_cancel_busy);
+DEFINE_HANDSHAKE_EVENT(handshake_destruct);
+
+
+TRACE_EVENT(handshake_complete,
+	TP_PROTO(
+		const struct net *net,
+		const struct handshake_req *req,
+		const struct sock *sk,
+		int status
+	),
+	TP_ARGS(net, req, sk, status),
+	TP_STRUCT__entry(
+		__field(const void *, req)
+		__field(const void *, sk)
+		__field(int, status)
+		__field(unsigned int, netns_ino)
+	),
+	TP_fast_assign(
+		__entry->req = req;
+		__entry->sk = sk;
+		__entry->status = status;
+		__entry->netns_ino = net->ns.inum;
+	),
+	TP_printk("req=%p sk=%p status=%d",
+		__entry->req, __entry->sk, __entry->status
+	)
+);
+
+/**
+ ** Netlink events
+ **/
+
+DEFINE_HANDSHAKE_ERROR(handshake_notify_err);
+DEFINE_HANDSHAKE_FD_EVENT(handshake_cmd_accept);
+DEFINE_HANDSHAKE_ERROR(handshake_cmd_accept_err);
+DEFINE_HANDSHAKE_FD_EVENT(handshake_cmd_done);
+DEFINE_HANDSHAKE_ERROR(handshake_cmd_done_err);
+
+#endif /* _TRACE_HANDSHAKE_H */
+
+#include <trace/define_trace.h>
diff --git a/include/uapi/linux/handshake.h b/include/uapi/linux/handshake.h
new file mode 100644
index 000000000000..519d91c50039
--- /dev/null
+++ b/include/uapi/linux/handshake.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/handshake.yaml */
+/* YNL-GEN uapi header */
+
+#ifndef _UAPI_LINUX_HANDSHAKE_H
+#define _UAPI_LINUX_HANDSHAKE_H
+
+#define HANDSHAKE_FAMILY_NAME		"handshake"
+#define HANDSHAKE_FAMILY_VERSION	1
+
+enum handshake_handler_class {
+	HANDSHAKE_HANDLER_CLASS_NONE,
+};
+
+enum handshake_msg_type {
+	HANDSHAKE_MSG_TYPE_UNSPEC,
+	HANDSHAKE_MSG_TYPE_CLIENTHELLO,
+	HANDSHAKE_MSG_TYPE_SERVERHELLO,
+};
+
+enum handshake_auth {
+	HANDSHAKE_AUTH_UNSPEC,
+	HANDSHAKE_AUTH_UNAUTH,
+	HANDSHAKE_AUTH_PSK,
+	HANDSHAKE_AUTH_X509,
+};
+
+enum {
+	HANDSHAKE_A_X509_CERT = 1,
+	HANDSHAKE_A_X509_PRIVKEY,
+
+	__HANDSHAKE_A_X509_MAX,
+	HANDSHAKE_A_X509_MAX = (__HANDSHAKE_A_X509_MAX - 1)
+};
+
+enum {
+	HANDSHAKE_A_ACCEPT_SOCKFD = 1,
+	HANDSHAKE_A_ACCEPT_HANDLER_CLASS,
+	HANDSHAKE_A_ACCEPT_MESSAGE_TYPE,
+	HANDSHAKE_A_ACCEPT_TIMEOUT,
+	HANDSHAKE_A_ACCEPT_AUTH_MODE,
+	HANDSHAKE_A_ACCEPT_PEER_IDENTITY,
+	HANDSHAKE_A_ACCEPT_CERTIFICATE,
+
+	__HANDSHAKE_A_ACCEPT_MAX,
+	HANDSHAKE_A_ACCEPT_MAX = (__HANDSHAKE_A_ACCEPT_MAX - 1)
+};
+
+enum {
+	HANDSHAKE_A_DONE_STATUS = 1,
+	HANDSHAKE_A_DONE_SOCKFD,
+	HANDSHAKE_A_DONE_REMOTE_AUTH,
+
+	__HANDSHAKE_A_DONE_MAX,
+	HANDSHAKE_A_DONE_MAX = (__HANDSHAKE_A_DONE_MAX - 1)
+};
+
+enum {
+	HANDSHAKE_CMD_READY = 1,
+	HANDSHAKE_CMD_ACCEPT,
+	HANDSHAKE_CMD_DONE,
+
+	__HANDSHAKE_CMD_MAX,
+	HANDSHAKE_CMD_MAX = (__HANDSHAKE_CMD_MAX - 1)
+};
+
+#define HANDSHAKE_MCGRP_NONE	"none"
+
+#endif /* _UAPI_LINUX_HANDSHAKE_H */
diff --git a/net/Kconfig b/net/Kconfig
index 48c33c222199..f9962506dd9e 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -68,6 +68,11 @@ source "net/iucv/Kconfig"
 source "net/smc/Kconfig"
 source "net/xdp/Kconfig"
 
+config NET_HANDSHAKE
+	bool
+	depends on SUNRPC || NVME_TARGET_TCP || NVME_TCP
+	default y
+
 config INET
 	bool "TCP/IP networking"
 	help
diff --git a/net/Makefile b/net/Makefile
index 0914bea9c335..bfee380efb46 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -79,3 +79,4 @@ obj-$(CONFIG_NET_NCSI)		+= ncsi/
 obj-$(CONFIG_XDP_SOCKETS)	+= xdp/
 obj-$(CONFIG_MPTCP)		+= mptcp/
 obj-$(CONFIG_MCTP)		+= mctp/
+obj-$(CONFIG_NET_HANDSHAKE)	+= handshake/
diff --git a/net/handshake/Makefile b/net/handshake/Makefile
new file mode 100644
index 000000000000..d38736de45da
--- /dev/null
+++ b/net/handshake/Makefile
@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the Generic HANDSHAKE service
+#
+# Author: Chuck Lever <chuck.lever@oracle.com>
+#
+# Copyright (c) 2023, Oracle and/or its affiliates.
+#
+
+obj-y += handshake.o
+handshake-y := genl.o netlink.o request.o trace.o
diff --git a/net/handshake/genl.c b/net/handshake/genl.c
new file mode 100644
index 000000000000..2a9872ee3647
--- /dev/null
+++ b/net/handshake/genl.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/handshake.yaml */
+/* YNL-GEN kernel source */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "genl.h"
+
+#include <linux/handshake.h>
+
+/* HANDSHAKE_CMD_ACCEPT - do */
+static const struct nla_policy handshake_accept_nl_policy[HANDSHAKE_A_ACCEPT_HANDLER_CLASS + 1] = {
+	[HANDSHAKE_A_ACCEPT_HANDLER_CLASS] = NLA_POLICY_MAX(NLA_U32, 0),
+};
+
+/* HANDSHAKE_CMD_DONE - do */
+static const struct nla_policy handshake_done_nl_policy[HANDSHAKE_A_DONE_REMOTE_AUTH + 1] = {
+	[HANDSHAKE_A_DONE_STATUS] = { .type = NLA_U32, },
+	[HANDSHAKE_A_DONE_SOCKFD] = { .type = NLA_U32, },
+	[HANDSHAKE_A_DONE_REMOTE_AUTH] = { .type = NLA_U32, },
+};
+
+/* Ops table for handshake */
+static const struct genl_split_ops handshake_nl_ops[2] = {
+	{
+		.cmd		= HANDSHAKE_CMD_ACCEPT,
+		.doit		= handshake_nl_accept_doit,
+		.policy		= handshake_accept_nl_policy,
+		.maxattr	= HANDSHAKE_A_ACCEPT_HANDLER_CLASS,
+		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd		= HANDSHAKE_CMD_DONE,
+		.doit		= handshake_nl_done_doit,
+		.policy		= handshake_done_nl_policy,
+		.maxattr	= HANDSHAKE_A_DONE_REMOTE_AUTH,
+		.flags		= GENL_CMD_CAP_DO,
+	},
+};
+
+static const struct genl_multicast_group handshake_nl_mcgrps[] = {
+	[HANDSHAKE_NLGRP_NONE] = { "none", },
+};
+
+struct genl_family handshake_nl_family __ro_after_init = {
+	.name		= HANDSHAKE_FAMILY_NAME,
+	.version	= HANDSHAKE_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= handshake_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(handshake_nl_ops),
+	.mcgrps		= handshake_nl_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(handshake_nl_mcgrps),
+};
diff --git a/net/handshake/genl.h b/net/handshake/genl.h
new file mode 100644
index 000000000000..a1eb7ccccc7f
--- /dev/null
+++ b/net/handshake/genl.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/handshake.yaml */
+/* YNL-GEN kernel header */
+
+#ifndef _LINUX_HANDSHAKE_GEN_H
+#define _LINUX_HANDSHAKE_GEN_H
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include <linux/handshake.h>
+
+int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info);
+int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info);
+
+enum {
+	HANDSHAKE_NLGRP_NONE,
+};
+
+extern struct genl_family handshake_nl_family;
+
+#endif /* _LINUX_HANDSHAKE_GEN_H */
diff --git a/net/handshake/handshake.h b/net/handshake/handshake.h
new file mode 100644
index 000000000000..0841b05ec76c
--- /dev/null
+++ b/net/handshake/handshake.h
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Generic netlink handshake service
+ *
+ * Author: Chuck Lever <chuck.lever@oracle.com>
+ *
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ */
+
+#ifndef _INTERNAL_HANDSHAKE_H
+#define _INTERNAL_HANDSHAKE_H
+
+/* Per-net namespace context */
+struct handshake_net {
+	spinlock_t		hn_lock;	/* protects next 3 fields */
+	int			hn_pending;
+	int			hn_pending_max;
+	struct list_head	hn_requests;
+
+	unsigned long		hn_flags;
+};
+
+enum hn_flags_bits {
+	HANDSHAKE_F_NET_DRAINING,
+};
+
+struct handshake_proto;
+
+/* One handshake request */
+struct handshake_req {
+	struct list_head		hr_list;
+	struct rhash_head		hr_rhash;
+	unsigned long			hr_flags;
+	const struct handshake_proto	*hr_proto;
+	struct sock			*hr_sk;
+	void				(*hr_odestruct)(struct sock *sk);
+
+	/* Always the last field */
+	char				hr_priv[];
+};
+
+enum hr_flags_bits {
+	HANDSHAKE_F_REQ_COMPLETED,
+};
+
+/* Invariants for all handshake requests for one transport layer
+ * security protocol
+ */
+struct handshake_proto {
+	int			hp_handler_class;
+	size_t			hp_privsize;
+
+	int			(*hp_accept)(struct handshake_req *req,
+					     struct genl_info *info, int fd);
+	void			(*hp_done)(struct handshake_req *req,
+					   unsigned int status,
+					   struct genl_info *info);
+	void			(*hp_destroy)(struct handshake_req *req);
+};
+
+/* netlink.c */
+int handshake_genl_notify(struct net *net, int handler_class, gfp_t flags);
+struct nlmsghdr *handshake_genl_put(struct sk_buff *msg,
+				    struct genl_info *info);
+struct handshake_net *handshake_pernet(struct net *net);
+
+/* request.c */
+struct handshake_req *
+handshake_req_alloc(struct socket *sock, const struct handshake_proto *proto,
+		    gfp_t flags);
+int handshake_req_hash_init(void);
+void handshake_req_hash_destroy(void);
+void *handshake_req_private(struct handshake_req *req);
+struct handshake_req *handshake_req_hash_lookup(struct sock *sk);
+void __remove_pending_locked(struct handshake_net *hn,
+			     struct handshake_req *req);
+int handshake_req_submit(struct handshake_req *req, gfp_t flags);
+void handshake_complete(struct handshake_req *req, unsigned int status,
+			struct genl_info *info);
+bool handshake_req_cancel(struct socket *sock);
+
+#endif /* _INTERNAL_HANDSHAKE_H */
diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c
new file mode 100644
index 000000000000..627d4d890bac
--- /dev/null
+++ b/net/handshake/netlink.c
@@ -0,0 +1,316 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic netlink handshake service
+ *
+ * Author: Chuck Lever <chuck.lever@oracle.com>
+ *
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ */
+
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/mm.h>
+
+#include <net/sock.h>
+#include <net/genetlink.h>
+#include <net/netns/generic.h>
+
+#include <uapi/linux/handshake.h>
+#include "handshake.h"
+#include "genl.h"
+
+#include <trace/events/handshake.h>
+
+/**
+ * handshake_genl_notify - Notify handlers that a request is waiting
+ * @net: target network namespace
+ * @handler_class: target handler
+ * @flags: memory allocation control flags
+ *
+ * Returns zero on success or a negative errno if notification failed.
+ */
+int handshake_genl_notify(struct net *net, int handler_class, gfp_t flags)
+{
+	struct sk_buff *msg;
+	void *hdr;
+
+	if (!genl_has_listeners(&handshake_nl_family, net, handler_class))
+		return -ESRCH;
+
+	msg = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_put(msg, 0, 0, &handshake_nl_family, 0,
+			  HANDSHAKE_CMD_READY);
+	if (!hdr)
+		goto out_free;
+
+	if (nla_put_u32(msg, HANDSHAKE_A_ACCEPT_HANDLER_CLASS,
+			handler_class) < 0) {
+		genlmsg_cancel(msg, hdr);
+		goto out_free;
+	}
+
+	genlmsg_end(msg, hdr);
+	return genlmsg_multicast_netns(&handshake_nl_family, net, msg,
+				       0, handler_class, flags);
+
+out_free:
+	nlmsg_free(msg);
+	return -EMSGSIZE;
+}
+
+/**
+ * handshake_genl_put - Create a generic netlink message header
+ * @msg: buffer in which to create the header
+ * @info: generic netlink message context
+ *
+ * Returns a ready-to-use header, or NULL.
+ */
+struct nlmsghdr *handshake_genl_put(struct sk_buff *msg,
+				    struct genl_info *info)
+{
+	return genlmsg_put(msg, info->snd_portid, info->snd_seq,
+			   &handshake_nl_family, 0, info->genlhdr->cmd);
+}
+EXPORT_SYMBOL(handshake_genl_put);
+
+/*
+ * dup() a kernel socket for use as a user space file descriptor
+ * in the current process. The kernel socket must have an
+ * instatiated struct file.
+ *
+ * Implicit argument: "current()"
+ */
+static int handshake_dup(struct socket *sock)
+{
+	struct file *file;
+	int newfd;
+
+	if (!sock->file)
+		return -EBADF;
+
+	file = get_file(sock->file);
+	newfd = get_unused_fd_flags(O_CLOEXEC);
+	if (newfd < 0) {
+		fput(file);
+		return newfd;
+	}
+
+	fd_install(newfd, file);
+	return newfd;
+}
+
+int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct net *net = sock_net(skb->sk);
+	struct handshake_net *hn = handshake_pernet(net);
+	struct handshake_req *pos, *req = NULL;
+	struct socket *sock;
+	int class, fd, err;
+
+	err = -EOPNOTSUPP;
+	if (!hn)
+		goto out_status;
+
+	err = -EINVAL;
+	if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_ACCEPT_HANDLER_CLASS))
+		goto out_status;
+	class = nla_get_u32(info->attrs[HANDSHAKE_A_ACCEPT_HANDLER_CLASS]);
+
+	req = NULL;
+	spin_lock(&hn->hn_lock);
+	list_for_each_entry(pos, &hn->hn_requests, hr_list) {
+		if (pos->hr_proto->hp_handler_class != class)
+			continue;
+		__remove_pending_locked(hn, pos);
+		req = pos;
+		break;
+	}
+	spin_unlock(&hn->hn_lock);
+	if (!req)
+		goto out_status;
+
+	sock = req->hr_sk->sk_socket;
+	fd = handshake_dup(sock);
+	if (fd < 0) {
+		err = fd;
+		goto out_complete;
+	}
+	err = req->hr_proto->hp_accept(req, info, fd);
+	if (err)
+		goto out_complete;
+
+	trace_handshake_cmd_accept(net, req, req->hr_sk, fd);
+	return 0;
+
+out_complete:
+	handshake_complete(req, -EIO, NULL);
+	fput(sock->file);
+out_status:
+	trace_handshake_cmd_accept_err(net, req, NULL, err);
+	return err;
+}
+
+int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct net *net = sock_net(skb->sk);
+	struct socket *sock = NULL;
+	struct handshake_req *req;
+	int fd, status, err;
+
+	if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_DONE_SOCKFD))
+		return -EINVAL;
+	fd = nla_get_u32(info->attrs[HANDSHAKE_A_DONE_SOCKFD]);
+
+	err = 0;
+	sock = sockfd_lookup(fd, &err);
+	if (err) {
+		err = -EBADF;
+		goto out_status;
+	}
+
+	req = handshake_req_hash_lookup(sock->sk);
+	if (!req) {
+		err = -EBUSY;
+		goto out_status;
+	}
+
+	trace_handshake_cmd_done(net, req, sock->sk, fd);
+
+	status = -EIO;
+	if (info->attrs[HANDSHAKE_A_DONE_STATUS])
+		status = nla_get_u32(info->attrs[HANDSHAKE_A_DONE_STATUS]);
+
+	handshake_complete(req, status, info);
+	fput(sock->file);
+	return 0;
+
+out_status:
+	trace_handshake_cmd_done_err(net, req, sock->sk, err);
+	return err;
+}
+
+static unsigned int handshake_net_id;
+
+static int __net_init handshake_net_init(struct net *net)
+{
+	struct handshake_net *hn = net_generic(net, handshake_net_id);
+	unsigned long tmp;
+	struct sysinfo si;
+
+	/*
+	 * Arbitrary limit to prevent handshakes that do not make
+	 * progress from clogging up the system.
+	 */
+	si_meminfo(&si);
+	tmp = si.totalram / (25 * si.mem_unit);
+	hn->hn_pending_max = clamp(tmp, 3UL, 25UL);
+
+	spin_lock_init(&hn->hn_lock);
+	hn->hn_pending = 0;
+	hn->hn_flags = 0;
+	INIT_LIST_HEAD(&hn->hn_requests);
+	return 0;
+}
+
+static void __net_exit handshake_net_exit(struct net *net)
+{
+	struct handshake_net *hn = net_generic(net, handshake_net_id);
+	struct handshake_req *req;
+	LIST_HEAD(requests);
+
+	/*
+	 * Drain the net's pending list. Requests that have been
+	 * accepted and are in progress will be destroyed when
+	 * the socket is closed.
+	 */
+	spin_lock(&hn->hn_lock);
+	set_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags);
+	list_splice_init(&requests, &hn->hn_requests);
+	spin_unlock(&hn->hn_lock);
+
+	while (!list_empty(&requests)) {
+		req = list_first_entry(&requests, struct handshake_req, hr_list);
+		list_del(&req->hr_list);
+
+		/*
+		 * Requests on this list have not yet been
+		 * accepted, so they do not have an fd to put.
+		 */
+
+		handshake_complete(req, -ETIMEDOUT, NULL);
+	}
+}
+
+static struct pernet_operations __net_initdata handshake_genl_net_ops = {
+	.init		= handshake_net_init,
+	.exit		= handshake_net_exit,
+	.id		= &handshake_net_id,
+	.size		= sizeof(struct handshake_net),
+};
+
+/**
+ * handshake_pernet - Get the handshake private per-net structure
+ * @net: network namespace
+ *
+ * Returns a pointer to the net's private per-net structure for the
+ * handshake module, or NULL if handshake_init() failed.
+ */
+struct handshake_net *handshake_pernet(struct net *net)
+{
+	return handshake_net_id ?
+		net_generic(net, handshake_net_id) : NULL;
+}
+
+static int __init handshake_init(void)
+{
+	int ret;
+
+	ret = handshake_req_hash_init();
+	if (ret) {
+		pr_warn("handshake: hash initialization failed (%d)\n", ret);
+		return ret;
+	}
+
+	ret = genl_register_family(&handshake_nl_family);
+	if (ret) {
+		pr_warn("handshake: netlink registration failed (%d)\n", ret);
+		handshake_req_hash_destroy();
+		return ret;
+	}
+
+	/*
+	 * ORDER: register_pernet_subsys must be done last.
+	 *
+	 *	If initialization does not make it past pernet_subsys
+	 *	registration, then handshake_net_id will remain 0. That
+	 *	shunts the handshake consumer API to return ENOTSUPP
+	 *	to prevent it from dereferencing something that hasn't
+	 *	been allocated.
+	 */
+	ret = register_pernet_subsys(&handshake_genl_net_ops);
+	if (ret) {
+		pr_warn("handshake: pernet registration failed (%d)\n", ret);
+		genl_unregister_family(&handshake_nl_family);
+		handshake_req_hash_destroy();
+	}
+
+	return ret;
+}
+
+static void __exit handshake_exit(void)
+{
+	unregister_pernet_subsys(&handshake_genl_net_ops);
+	handshake_net_id = 0;
+
+	handshake_req_hash_destroy();
+	genl_unregister_family(&handshake_nl_family);
+}
+
+module_init(handshake_init);
+module_exit(handshake_exit);
diff --git a/net/handshake/request.c b/net/handshake/request.c
new file mode 100644
index 000000000000..3f8ae9e990d2
--- /dev/null
+++ b/net/handshake/request.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Handshake request lifetime events
+ *
+ * Author: Chuck Lever <chuck.lever@oracle.com>
+ *
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ */
+
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/inet.h>
+#include <linux/fdtable.h>
+#include <linux/rhashtable.h>
+
+#include <net/sock.h>
+#include <net/genetlink.h>
+#include <net/netns/generic.h>
+
+#include <uapi/linux/handshake.h>
+#include "handshake.h"
+
+#include <trace/events/handshake.h>
+
+/*
+ * We need both a handshake_req -> sock mapping, and a sock ->
+ * handshake_req mapping. Both are one-to-one.
+ *
+ * To avoid adding another pointer field to struct sock, net/handshake
+ * maintains a hash table, indexed by the memory address of @sock, to
+ * find the struct handshake_req outstanding for that socket. The
+ * reverse direction uses a simple pointer field in the handshake_req
+ * struct.
+ */
+
+static struct rhashtable handshake_rhashtbl ____cacheline_aligned_in_smp;
+
+static const struct rhashtable_params handshake_rhash_params = {
+	.key_len		= sizeof_field(struct handshake_req, hr_sk),
+	.key_offset		= offsetof(struct handshake_req, hr_sk),
+	.head_offset		= offsetof(struct handshake_req, hr_rhash),
+	.automatic_shrinking	= true,
+};
+
+int handshake_req_hash_init(void)
+{
+	return rhashtable_init(&handshake_rhashtbl, &handshake_rhash_params);
+}
+
+void handshake_req_hash_destroy(void)
+{
+	rhashtable_destroy(&handshake_rhashtbl);
+}
+
+struct handshake_req *handshake_req_hash_lookup(struct sock *sk)
+{
+	return rhashtable_lookup_fast(&handshake_rhashtbl, &sk,
+				      handshake_rhash_params);
+}
+
+static noinline bool handshake_req_hash_add(struct handshake_req *req)
+{
+	int ret;
+
+	ret = rhashtable_lookup_insert_fast(&handshake_rhashtbl,
+					    &req->hr_rhash,
+					    handshake_rhash_params);
+	return ret == 0;
+}
+
+static noinline void handshake_req_destroy(struct handshake_req *req)
+{
+	if (req->hr_proto->hp_destroy)
+		req->hr_proto->hp_destroy(req);
+	rhashtable_remove_fast(&handshake_rhashtbl, &req->hr_rhash,
+			       handshake_rhash_params);
+	kfree(req);
+}
+
+static void handshake_sk_destruct(struct sock *sk)
+{
+	void (*sk_destruct)(struct sock *sk);
+	struct handshake_req *req;
+
+	req = handshake_req_hash_lookup(sk);
+	if (!req)
+		return;
+
+	trace_handshake_destruct(sock_net(sk), req, sk);
+	sk_destruct = req->hr_odestruct;
+	handshake_req_destroy(req);
+	if (sk_destruct)
+		sk_destruct(sk);
+}
+
+/**
+ * handshake_req_alloc - consumer API to allocate a request
+ * @sock: open socket on which to perform a handshake
+ * @proto: security protocol
+ * @flags: memory allocation flags
+ *
+ * Returns an initialized handshake_req or NULL.
+ */
+struct handshake_req *handshake_req_alloc(struct socket *sock,
+					  const struct handshake_proto *proto,
+					  gfp_t flags)
+{
+	struct sock *sk = sock->sk;
+	struct net *net = sock_net(sk);
+	struct handshake_net *hn = handshake_pernet(net);
+	struct handshake_req *req;
+
+	if (!hn)
+		return NULL;
+
+	req = kzalloc(struct_size(req, hr_priv, proto->hp_privsize), flags);
+	if (!req)
+		return NULL;
+
+	sock_hold(sk);
+
+	INIT_LIST_HEAD(&req->hr_list);
+	req->hr_sk = sk;
+	req->hr_proto = proto;
+	return req;
+}
+EXPORT_SYMBOL(handshake_req_alloc);
+
+/**
+ * handshake_req_private - consumer API to return per-handshake private data
+ * @req: handshake arguments
+ *
+ */
+void *handshake_req_private(struct handshake_req *req)
+{
+	return (void *)&req->hr_priv;
+}
+EXPORT_SYMBOL(handshake_req_private);
+
+static bool __add_pending_locked(struct handshake_net *hn,
+				 struct handshake_req *req)
+{
+	if (!list_empty(&req->hr_list))
+		return false;
+	hn->hn_pending++;
+	list_add_tail(&req->hr_list, &hn->hn_requests);
+	return true;
+}
+
+void __remove_pending_locked(struct handshake_net *hn,
+			     struct handshake_req *req)
+{
+	hn->hn_pending--;
+	list_del_init(&req->hr_list);
+}
+
+/*
+ * Returns %true if the request was found on @net's pending list,
+ * otherwise %false.
+ *
+ * If @req was on a pending list, it has not yet been accepted.
+ */
+static bool remove_pending(struct handshake_net *hn, struct handshake_req *req)
+{
+	bool ret;
+
+	ret = false;
+
+	spin_lock(&hn->hn_lock);
+	if (!list_empty(&req->hr_list)) {
+		__remove_pending_locked(hn, req);
+		ret = true;
+	}
+	spin_unlock(&hn->hn_lock);
+
+	return ret;
+}
+
+/**
+ * handshake_req_submit - consumer API to submit a handshake request
+ * @req: handshake arguments
+ * @flags: memory allocation flags
+ *
+ * Return values:
+ *   %0: Request queued
+ *   %-EBUSY: A handshake is already under way for this socket
+ *   %-ESRCH: No handshake agent is available
+ *   %-EAGAIN: Too many pending handshake requests
+ *   %-ENOMEM: Failed to allocate memory
+ *   %-EMSGSIZE: Failed to construct notification message
+ *   %-EOPNOTSUPP: Handshake module not initialized
+ *
+ * A zero return value from handshake_request() means that
+ * exactly one subsequent completion callback is guaranteed.
+ *
+ * A negative return value from handshake_request() means that
+ * no completion callback will be done and that @req has been
+ * destroyed.
+ */
+int handshake_req_submit(struct handshake_req *req, gfp_t flags)
+{
+	struct sock *sk = req->hr_sk;
+	struct net *net = sock_net(sk);
+	struct handshake_net *hn = handshake_pernet(net);
+	int ret;
+
+	if (!hn)
+		return -EOPNOTSUPP;
+
+	ret = -EAGAIN;
+	if (READ_ONCE(hn->hn_pending) >= hn->hn_pending_max)
+		goto out_err;
+
+	req->hr_odestruct = sk->sk_destruct;
+	sk->sk_destruct = handshake_sk_destruct;
+	spin_lock(&hn->hn_lock);
+	ret = -EOPNOTSUPP;
+	if (test_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags))
+		goto out_unlock;
+	ret = -EBUSY;
+	if (!handshake_req_hash_add(req))
+		goto out_unlock;
+	if (!__add_pending_locked(hn, req))
+		goto out_unlock;
+	spin_unlock(&hn->hn_lock);
+
+	ret = handshake_genl_notify(net, req->hr_proto->hp_handler_class,
+				    flags);
+	if (ret) {
+		trace_handshake_notify_err(net, req, sk, ret);
+		if (remove_pending(hn, req))
+			goto out_err;
+	}
+
+	trace_handshake_submit(net, req, sk);
+	return 0;
+
+out_unlock:
+	spin_unlock(&hn->hn_lock);
+out_err:
+	trace_handshake_submit_err(net, req, sk, ret);
+	handshake_req_destroy(req);
+	return ret;
+}
+EXPORT_SYMBOL(handshake_req_submit);
+
+void handshake_complete(struct handshake_req *req, unsigned int status,
+			struct genl_info *info)
+{
+	struct sock *sk = req->hr_sk;
+	struct net *net = sock_net(sk);
+
+	if (!test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) {
+		trace_handshake_complete(net, req, sk, status);
+		req->hr_proto->hp_done(req, status, info);
+		__sock_put(sk);
+	}
+}
+
+/**
+ * handshake_req_cancel - consumer API to cancel an in-progress handshake
+ * @sock: socket on which there is an ongoing handshake
+ *
+ * XXX: Perhaps killing the user space agent might also be necessary?
+ *
+ * Request cancellation races with request completion. To determine
+ * who won, callers examine the return value from this function.
+ *
+ * Return values:
+ *   %true - Uncompleted handshake request was canceled or not found
+ *   %false - Handshake request already completed
+ */
+bool handshake_req_cancel(struct socket *sock)
+{
+	struct handshake_req *req;
+	struct handshake_net *hn;
+	struct sock *sk;
+	struct net *net;
+
+	sk = sock->sk;
+	net = sock_net(sk);
+	req = handshake_req_hash_lookup(sk);
+	if (!req) {
+		trace_handshake_cancel_none(net, req, sk);
+		return true;
+	}
+
+	hn = handshake_pernet(net);
+	if (hn && remove_pending(hn, req)) {
+		/* Request hadn't been accepted */
+		trace_handshake_cancel(net, req, sk);
+		return true;
+	}
+	if (test_and_set_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags)) {
+		/* Request already completed */
+		trace_handshake_cancel_busy(net, req, sk);
+		return false;
+	}
+
+	__sock_put(sk);
+	trace_handshake_cancel(net, req, sk);
+	return true;
+}
+EXPORT_SYMBOL(handshake_req_cancel);
diff --git a/net/handshake/trace.c b/net/handshake/trace.c
new file mode 100644
index 000000000000..1c4d8e27e17a
--- /dev/null
+++ b/net/handshake/trace.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Trace points for transport security layer handshakes.
+ *
+ * Author: Chuck Lever <chuck.lever@oracle.com>
+ *
+ * Copyright (c) 2023, Oracle and/or its affiliates.
+ */
+
+#include <linux/types.h>
+
+#include <net/sock.h>
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "handshake.h"
+
+#define CREATE_TRACE_POINTS
+
+#include <trace/events/handshake.h>
