selftest: Add test for bind() conflicts.

The test checks if (IPv4, IPv6) address pair properly conflict or not.

  * IPv4
    * 0.0.0.0
    * 127.0.0.1

  * IPv6
    * ::
    * ::1

If the IPv6 address is [::], the second bind() always fails.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 bind_bhash
 bind_timewait
+bind_wildcard
 csum
 cmsg_sender
 diag_uid

tools/testing/selftests/net/Makefile

@@ -80,6 +80,7 @@ TEST_GEN_FILES += sctp_hello
 TEST_GEN_FILES += csum
 TEST_GEN_FILES += nat6to4.o
 TEST_GEN_FILES += ip_local_port_range
+TEST_GEN_FILES += bind_wildcard
 
 TEST_FILES := settings
 

tools/testing/selftests/net/bind_wildcard.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright Amazon.com Inc. or its affiliates. */
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+
+#include "../kselftest_harness.h"
+
+FIXTURE(bind_wildcard)
+{
+	struct sockaddr_in addr4;
+	struct sockaddr_in6 addr6;
+	int expected_errno;
+};
+
+FIXTURE_VARIANT(bind_wildcard)
+{
+	const __u32 addr4_const;
+	const struct in6_addr *addr6_const;
+};
+
+FIXTURE_VARIANT_ADD(bind_wildcard, v4_any_v6_any)
+{
+	.addr4_const = INADDR_ANY,
+	.addr6_const = &in6addr_any,
+};
+
+FIXTURE_VARIANT_ADD(bind_wildcard, v4_any_v6_local)
+{
+	.addr4_const = INADDR_ANY,
+	.addr6_const = &in6addr_loopback,
+};
+
+FIXTURE_VARIANT_ADD(bind_wildcard, v4_local_v6_any)
+{
+	.addr4_const = INADDR_LOOPBACK,
+	.addr6_const = &in6addr_any,
+};
+
+FIXTURE_VARIANT_ADD(bind_wildcard, v4_local_v6_local)
+{
+	.addr4_const = INADDR_LOOPBACK,
+	.addr6_const = &in6addr_loopback,
+};
+
+FIXTURE_SETUP(bind_wildcard)
+{
+	self->addr4.sin_family = AF_INET;
+	self->addr4.sin_port = htons(0);
+	self->addr4.sin_addr.s_addr = htonl(variant->addr4_const);
+
+	self->addr6.sin6_family = AF_INET6;
+	self->addr6.sin6_port = htons(0);
+	self->addr6.sin6_addr = *variant->addr6_const;
+
+	if (variant->addr6_const == &in6addr_any)
+		self->expected_errno = EADDRINUSE;
+	else
+		self->expected_errno = 0;
+}
+
+FIXTURE_TEARDOWN(bind_wildcard)
+{
+}
+
+void bind_sockets(struct __test_metadata *_metadata,
+		  FIXTURE_DATA(bind_wildcard) *self,
+		  struct sockaddr *addr1, socklen_t addrlen1,
+		  struct sockaddr *addr2, socklen_t addrlen2)
+{
+	int fd[2];
+	int ret;
+
+	fd[0] = socket(addr1->sa_family, SOCK_STREAM, 0);
+	ASSERT_GT(fd[0], 0);
+
+	ret = bind(fd[0], addr1, addrlen1);
+	ASSERT_EQ(ret, 0);
+
+	ret = getsockname(fd[0], addr1, &addrlen1);
+	ASSERT_EQ(ret, 0);
+
+	((struct sockaddr_in *)addr2)->sin_port = ((struct sockaddr_in *)addr1)->sin_port;
+
+	fd[1] = socket(addr2->sa_family, SOCK_STREAM, 0);
+	ASSERT_GT(fd[1], 0);
+
+	ret = bind(fd[1], addr2, addrlen2);
+	if (self->expected_errno) {
+		ASSERT_EQ(ret, -1);
+		ASSERT_EQ(errno, self->expected_errno);
+	} else {
+		ASSERT_EQ(ret, 0);
+	}
+
+	close(fd[1]);
+	close(fd[0]);
+}
+
+TEST_F(bind_wildcard, v4_v6)
+{
+	bind_sockets(_metadata, self,
+		     (struct sockaddr *)&self->addr4, sizeof(self->addr6),
+		     (struct sockaddr *)&self->addr6, sizeof(self->addr6));
+}
+
+TEST_F(bind_wildcard, v6_v4)
+{
+	bind_sockets(_metadata, self,
+		     (struct sockaddr *)&self->addr6, sizeof(self->addr6),
+		     (struct sockaddr *)&self->addr4, sizeof(self->addr4));
+}
+
+TEST_HARNESS_MAIN