net: net_test: add tests for IP tunnel flags conversion helpers

Now that there are helpers for converting IP tunnel flags between the
old __be16 format and the bitmap format, make sure they work as expected
by adding a couple of tests to the networking testing suite. The helpers
are all inline, so no dependencies on the related CONFIG_* (or a
standalone module) are needed.

Cover three possible cases:

1. No bits past BIT(15) are set, VTI/SIT bits are not set. This
conversion is almost a direct assignment.
2. No bits past BIT(15) are set, but VTI/SIT bit is set. During the
conversion, it must be transformed into BIT(16) in the bitmap,
but still compatible with the __be16 format.
3. The bitmap has bits past BIT(15) set (not the VTI/SIT one). The
result will be truncated.
Note that currently __IP_TUNNEL_FLAG_NUM is 17 (incl. special),
which means that the result of this case is currently
semi-false-positive. When BIT(17) is finally here, it will be
adjusted accordingly.

Signed-off-by: Alexander Lobakin <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/Makefile

···
 obj-$(CONFIG_BPF_SYSCALL) += sock_map.o
 obj-$(CONFIG_BPF_SYSCALL) += bpf_sk_storage.o
 obj-$(CONFIG_OF)	+= of_net.o
-obj-$(CONFIG_NET_TEST) += gso_test.o
+obj-$(CONFIG_NET_TEST) += net_test.o

net/core/gso_test.c net/core/net_test.c

···
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include <kunit/test.h>
+
+/* GSO */
+
 #include <linux/skbuff.h>
 
 static const char hdr[] = "abcdefgh";
···
 	consume_skb(skb);
 }
 
-static struct kunit_case gso_test_cases[] = {
+/* IP tunnel flags */
+
+#include <net/ip_tunnels.h>
+
+struct ip_tunnel_flags_test {
+	const char	*name;
+
+	const u16	*src_bits;
+	const u16	*exp_bits;
+	u8		src_num;
+	u8		exp_num;
+
+	__be16		exp_val;
+	bool		exp_comp;
+};
+
+#define IP_TUNNEL_FLAGS_TEST(n, src, comp, eval, exp) {	\
+	.name		= (n),				\
+	.src_bits	= (src),			\
+	.src_num	= ARRAY_SIZE(src),		\
+	.exp_comp	= (comp),			\
+	.exp_val	= (eval),			\
+	.exp_bits	= (exp),			\
+	.exp_num	= ARRAY_SIZE(exp),		\
+}
+
+/* These are __be16-compatible and can be compared as is */
+static const u16 ip_tunnel_flags_1[] = {
+	IP_TUNNEL_KEY_BIT,
+	IP_TUNNEL_STRICT_BIT,
+	IP_TUNNEL_ERSPAN_OPT_BIT,
+};
+
+/* Due to the previous flags design limitation, setting either
+ * ``IP_TUNNEL_CSUM_BIT`` (on Big Endian) or ``IP_TUNNEL_DONT_FRAGMENT_BIT``
+ * (on Little) also sets VTI/ISATAP bit. In the bitmap implementation, they
+ * correspond to ``BIT(16)``, which is bigger than ``U16_MAX``, but still is
+ * backward-compatible.
+ */
+#ifdef __LITTLE_ENDIAN
+#define IP_TUNNEL_CONFLICT_BIT	IP_TUNNEL_DONT_FRAGMENT_BIT
+#else
+#define IP_TUNNEL_CONFLICT_BIT	IP_TUNNEL_CSUM_BIT
+#endif
+
+static const u16 ip_tunnel_flags_2_src[] = {
+	IP_TUNNEL_CONFLICT_BIT,
+};
+
+static const u16 ip_tunnel_flags_2_exp[] = {
+	IP_TUNNEL_CONFLICT_BIT,
+	IP_TUNNEL_SIT_ISATAP_BIT,
+};
+
+/* Bits 17 and higher are not compatible with __be16 flags */
+static const u16 ip_tunnel_flags_3_src[] = {
+	IP_TUNNEL_VXLAN_OPT_BIT,
+	17,
+	18,
+	20,
+};
+
+static const u16 ip_tunnel_flags_3_exp[] = {
+	IP_TUNNEL_VXLAN_OPT_BIT,
+};
+
+static const struct ip_tunnel_flags_test ip_tunnel_flags_test[] = {
+	IP_TUNNEL_FLAGS_TEST("compat", ip_tunnel_flags_1, true,
+			     cpu_to_be16(BIT(IP_TUNNEL_KEY_BIT) |
+					 BIT(IP_TUNNEL_STRICT_BIT) |
+					 BIT(IP_TUNNEL_ERSPAN_OPT_BIT)),
+			     ip_tunnel_flags_1),
+	IP_TUNNEL_FLAGS_TEST("conflict", ip_tunnel_flags_2_src, true,
+			     VTI_ISVTI, ip_tunnel_flags_2_exp),
+	IP_TUNNEL_FLAGS_TEST("new", ip_tunnel_flags_3_src,
+			     /* This must be set to ``false`` once
+			      * ``__IP_TUNNEL_FLAG_NUM`` goes above 17.
+			      */
+			     true, cpu_to_be16(BIT(IP_TUNNEL_VXLAN_OPT_BIT)),
+			     ip_tunnel_flags_3_exp),
+};
+
+static void
+ip_tunnel_flags_test_case_to_desc(const struct ip_tunnel_flags_test *t,
+				  char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+KUNIT_ARRAY_PARAM(ip_tunnel_flags_test, ip_tunnel_flags_test,
+		  ip_tunnel_flags_test_case_to_desc);
+
+static void ip_tunnel_flags_test_run(struct kunit *test)
+{
+	const struct ip_tunnel_flags_test *t = test->param_value;
+	IP_TUNNEL_DECLARE_FLAGS(src) = { };
+	IP_TUNNEL_DECLARE_FLAGS(exp) = { };
+	IP_TUNNEL_DECLARE_FLAGS(out);
+
+	for (u32 j = 0; j < t->src_num; j++)
+		__set_bit(t->src_bits[j], src);
+	for (u32 j = 0; j < t->exp_num; j++)
+		__set_bit(t->exp_bits[j], exp);
+
+	KUNIT_ASSERT_EQ(test, t->exp_comp,
+			ip_tunnel_flags_is_be16_compat(src));
+	KUNIT_ASSERT_EQ(test, (__force u16)t->exp_val,
+			(__force u16)ip_tunnel_flags_to_be16(src));
+
+	ip_tunnel_flags_from_be16(out, t->exp_val);
+	KUNIT_ASSERT_TRUE(test, __ipt_flag_op(bitmap_equal, exp, out));
+}
+
+static struct kunit_case net_test_cases[] = {
 	KUNIT_CASE_PARAM(gso_test_func, gso_test_gen_params),
-	{}
+	KUNIT_CASE_PARAM(ip_tunnel_flags_test_run,
+			 ip_tunnel_flags_test_gen_params),
+	{ },
 };
 
-static struct kunit_suite gso_test_suite = {
-	.name = "net_core_gso",
-	.test_cases = gso_test_cases,
+static struct kunit_suite net_test_suite = {
+	.name		= "net_core",
+	.test_cases	= net_test_cases,
 };
+kunit_test_suite(net_test_suite);
 
-kunit_test_suite(gso_test_suite);
-
+MODULE_DESCRIPTION("KUnit tests for networking core");
 MODULE_LICENSE("GPL");
-MODULE_DESCRIPTION("KUnit tests for segmentation offload");