blackhole_dev: convert self-test to KUnit

Convert this very simple smoke test to a KUnit test.

Add a missing `htons` call that was spotted[0] by kernel test robot
<lkp@intel.com> after initial conversion to KUnit.

Link: https://lore.kernel.org/oe-kbuild-all/202502090223.qCYMBjWT-lkp@intel.com/ [0]
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://patch.msgid.link/20250208-blackholedev-kunit-convert-v2-1-182db9bd56ec@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 28 insertions, 41 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af972a92d06..238321830993 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2557,15 +2557,6 @@ config TEST_BPF
 
 	  If unsure, say N.
 
-config TEST_BLACKHOLE_DEV
-	tristate "Test blackhole netdev functionality"
-	depends on m && NET
-	help
-	  This builds the "test_blackhole_dev" module that validates the
-	  data path through this blackhole netdev.
-
-	  If unsure, say N.
-
 config FIND_BIT_BENCHMARK
 	tristate "Test find_bit functions"
 	help
@@ -2888,6 +2879,17 @@ config USERCOPY_KUNIT_TEST
 	  on the copy_to/from_user infrastructure, making sure basic
 	  user/kernel boundary testing is working.
 
+config BLACKHOLE_DEV_KUNIT_TEST
+	tristate "Test blackhole netdev functionality" if !KUNIT_ALL_TESTS
+	depends on NET
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the "blackhole_dev_kunit" module that validates the
+	  data path through this blackhole netdev.
+
+	  If unsure, say N.
+
 config TEST_UDELAY
 	tristate "udelay test driver"
 	help
diff --git a/lib/Makefile b/lib/Makefile
index d5cfc7afbbb8..19ff6993c2bc 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -102,7 +102,6 @@ obj-$(CONFIG_TEST_RUNTIME) += tests/
 obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
 obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
 obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
-obj-$(CONFIG_TEST_BLACKHOLE_DEV) += test_blackhole_dev.o
 obj-$(CONFIG_TEST_MEMINIT) += test_meminit.o
 obj-$(CONFIG_TEST_LOCKUP) += test_lockup.o
 obj-$(CONFIG_TEST_HMM) += test_hmm.o
@@ -393,6 +392,7 @@ obj-$(CONFIG_FORTIFY_KUNIT_TEST) += fortify_kunit.o
 obj-$(CONFIG_CRC_KUNIT_TEST) += crc_kunit.o
 obj-$(CONFIG_SIPHASH_KUNIT_TEST) += siphash_kunit.o
 obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o
+obj-$(CONFIG_BLACKHOLE_DEV_KUNIT_TEST) += blackhole_dev_kunit.o
 
 obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
 
diff --git a/lib/test_blackhole_dev.c b/lib/blackhole_dev_kunit.c
index ec290ac2a0d9..06834ab35f43 100644
--- a/lib/test_blackhole_dev.c
+++ b/lib/blackhole_dev_kunit.c
@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * This module tests the blackhole_dev that is created during the
+ * This tests the blackhole_dev that is created during the
  * net subsystem initialization. The test this module performs is
  * by injecting an skb into the stack with skb->dev as the
  * blackhole_dev and expects kernel to behave in a sane manner
@@ -9,9 +9,8 @@
  * Copyright (c) 2018, Mahesh Bandewar <maheshb@google.com>
  */
 
-#include <linux/init.h>
+#include <kunit/test.h>
 #include <linux/module.h>
-#include <linux/printk.h>
 #include <linux/skbuff.h>
 #include <linux/netdevice.h>
 #include <linux/udp.h>
@@ -25,17 +24,15 @@
 
 #define UDP_PORT 1234
 
-static int __init test_blackholedev_init(void)
+static void test_blackholedev(struct kunit *test)
 {
 	struct ipv6hdr *ip6h;
 	struct sk_buff *skb;
 	struct udphdr *uh;
 	int data_len;
-	int ret;
 
 	skb = alloc_skb(SKB_SIZE, GFP_KERNEL);
-	if (!skb)
-		return -ENOMEM;
+	KUNIT_ASSERT_NOT_NULL(test, skb);
 
 	/* Reserve head-room for the headers */
 	skb_reserve(skb, HEAD_SIZE);
@@ -55,7 +52,7 @@ static int __init test_blackholedev_init(void)
 	ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));
 	skb_set_network_header(skb, 0);
 	ip6h->hop_limit = 32;
-	ip6h->payload_len = data_len + sizeof(struct udphdr);
+	ip6h->payload_len = htons(data_len + sizeof(struct udphdr));
 	ip6h->nexthdr = IPPROTO_UDP;
 	ip6h->saddr = in6addr_loopback;
 	ip6h->daddr = in6addr_loopback;
@@ -68,32 +65,20 @@ static int __init test_blackholedev_init(void)
 	skb->dev = blackhole_netdev;
 
 	/* Now attempt to send the packet */
-	ret = dev_queue_xmit(skb);
-
-	switch (ret) {
-	case NET_XMIT_SUCCESS:
-		pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");
-		break;
-	case NET_XMIT_DROP:
-		pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");
-		break;
-	case NET_XMIT_CN:
-		pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");
-		break;
-	default:
-		pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);
-	}
-
-	return 0;
+	KUNIT_EXPECT_EQ(test, dev_queue_xmit(skb), NET_XMIT_SUCCESS);
 }
 
-static void __exit test_blackholedev_exit(void)
-{
-	pr_warn("test_blackholedev module terminating.\n");
-}
+static struct kunit_case blackholedev_cases[] = {
+	KUNIT_CASE(test_blackholedev),
+	{},
+};
+
+static struct kunit_suite blackholedev_suite = {
+	.name = "blackholedev",
+	.test_cases = blackholedev_cases,
+};
 
-module_init(test_blackholedev_init);
-module_exit(test_blackholedev_exit);
+kunit_test_suite(blackholedev_suite);
 
 MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
 MODULE_DESCRIPTION("module test of the blackhole_dev");