net/handshake: Add Kunit tests for the handshake consumer API

These verify the API contracts and help exercise lifetime rules for
consumer sockets and handshake_req structures.

One way to run these tests:

./tools/testing/kunit/kunit.py run --kunitconfig ./net/handshake/.kunitconfig

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/Kconfig

@@ -73,6 +73,21 @@ config NET_HANDSHAKE
 	depends on SUNRPC || NVME_TARGET_TCP || NVME_TCP
 	default y
 
+config NET_HANDSHAKE_KUNIT_TEST
+	tristate "KUnit tests for the handshake upcall mechanism" if !KUNIT_ALL_TESTS
+	default KUNIT_ALL_TESTS
+	depends on KUNIT
+	help
+	  This builds the KUnit tests for the handshake upcall mechanism.
+
+	  KUnit tests run during boot and output the results to the debug
+	  log in TAP format (https://testanything.org/). Only useful for
+	  kernel devs running KUnit test harness and are not for inclusion
+	  into a production build.
+
+	  For more information on KUnit and unit tests in general, refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
 config INET
 	bool "TCP/IP networking"
 	help

net/handshake/.kunitconfig

@@ -0,0 +1,11 @@
+CONFIG_KUNIT=y
+CONFIG_UBSAN=y
+CONFIG_STACKTRACE=y
+CONFIG_NET=y
+CONFIG_NETWORK_FILESYSTEMS=y
+CONFIG_INET=y
+CONFIG_MULTIUSER=y
+CONFIG_NFS_FS=y
+CONFIG_SUNRPC=y
+CONFIG_NET_HANDSHAKE=y
+CONFIG_NET_HANDSHAKE_KUNIT_TEST=y

net/handshake/Makefile

@@ -9,3 +9,5 @@
 
 obj-y += handshake.o
 handshake-y := genl.o netlink.o request.o tlshd.o trace.o
+
+obj-$(CONFIG_NET_HANDSHAKE_KUNIT_TEST) += handshake-test.o

net/handshake/handshake.h

@@ -49,6 +49,7 @@ enum hr_flags_bits {
 struct handshake_proto {
 	int			hp_handler_class;
 	size_t			hp_privsize;
+	unsigned long		hp_flags;
 
 	int			(*hp_accept)(struct handshake_req *req,
 					     struct genl_info *info, int fd);
@@ -58,6 +59,10 @@ struct handshake_proto {
 	void			(*hp_destroy)(struct handshake_req *req);
 };
 
+enum hp_flags_bits {
+	HANDSHAKE_F_PROTO_NOTIFY,
+};
+
 /* netlink.c */
 int handshake_genl_notify(struct net *net, const struct handshake_proto *proto,
 			  gfp_t flags);

net/handshake/netlink.c

@@ -18,6 +18,8 @@
 #include <net/genetlink.h>
 #include <net/netns/generic.h>
 
+#include <kunit/visibility.h>
+
 #include <uapi/linux/handshake.h>
 #include "handshake.h"
 #include "genl.h"
@@ -38,6 +40,10 @@ int handshake_genl_notify(struct net *net, const struct handshake_proto *proto,
 	struct sk_buff *msg;
 	void *hdr;
 
+	/* Disable notifications during unit testing */
+	if (!test_bit(HANDSHAKE_F_PROTO_NOTIFY, &proto->hp_flags))
+		return 0;
+
 	if (!genl_has_listeners(&handshake_nl_family, net,
 				proto->hp_handler_class))
 		return -ESRCH;
@@ -262,6 +268,7 @@ struct handshake_net *handshake_pernet(struct net *net)
 	return handshake_net_id ?
 		net_generic(net, handshake_net_id) : NULL;
 }
+EXPORT_SYMBOL_IF_KUNIT(handshake_pernet);
 
 static int __init handshake_init(void)
 {

net/handshake/request.c

@@ -20,6 +20,8 @@
 #include <net/genetlink.h>
 #include <net/netns/generic.h>
 
+#include <kunit/visibility.h>
+
 #include <uapi/linux/handshake.h>
 #include "handshake.h"
 
@@ -60,6 +62,7 @@ struct handshake_req *handshake_req_hash_lookup(struct sock *sk)
 	return rhashtable_lookup_fast(&handshake_rhashtbl, &sk,
 				      handshake_rhash_params);
 }
+EXPORT_SYMBOL_IF_KUNIT(handshake_req_hash_lookup);
 
 static bool handshake_req_hash_add(struct handshake_req *req)
 {
@@ -192,6 +195,7 @@ struct handshake_req *handshake_req_next(struct handshake_net *hn, int class)
 
 	return req;
 }
+EXPORT_SYMBOL_IF_KUNIT(handshake_req_next);
 
 /**
  * handshake_req_submit - Submit a handshake request
@@ -293,6 +297,7 @@ void handshake_complete(struct handshake_req *req, unsigned int status,
 		sock_put(sk);
 	}
 }
+EXPORT_SYMBOL_IF_KUNIT(handshake_complete);
 
 /**
  * handshake_req_cancel - Cancel an in-progress handshake

net/handshake/tlshd.c

@@ -249,6 +249,7 @@ out:
 static const struct handshake_proto tls_handshake_proto = {
 	.hp_handler_class	= HANDSHAKE_HANDLER_CLASS_TLSHD,
 	.hp_privsize		= sizeof(struct tls_handshake_req),
+	.hp_flags		= BIT(HANDSHAKE_F_PROTO_NOTIFY),
 
 	.hp_accept		= tls_handshake_accept,
 	.hp_done		= tls_handshake_done,