[PATCH net-next v3 3/3] selftests/net: Add sk_bind_sendto_listen test

[Joanne Koong <joannelkoong@gmail.com>]

This patch adds a new test called sk_bind_sendto_listen.

This test exercises the path where a socket's rcv saddr changes after it
has been added to the binding tables, and then a listen() on the socket
is invoked. The listen() should succeed.

This test is copied over from one of syzbot's tests:
https://syzkaller.appspot.com/x/repro.c?x=1673a38df00000

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 tools/testing/selftests/net/.gitignore        |  1 +
 tools/testing/selftests/net/Makefile          |  1 +
 .../selftests/net/sk_bind_sendto_listen.c     | 82 +++++++++++++++++++
 3 files changed, 84 insertions(+)
 create mode 100644 tools/testing/selftests/net/sk_bind_sendto_listen.c

diff --git a/tools/testing/selftests/net/.gitignore b/tools/testing/selftests/net/.gitignore
index b984f8c8d523..69f1a2aafde4 100644
--- a/tools/testing/selftests/net/.gitignore
+++ b/tools/testing/selftests/net/.gitignore
@@ -38,3 +38,4 @@ ioam6_parser
 toeplitz
 cmsg_sender
 bind_bhash_test
+sk_bind_sendto_listen
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 464df13831f2..45f4f57bf1f4 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -60,6 +60,7 @@ TEST_GEN_FILES += cmsg_sender
 TEST_GEN_FILES += stress_reuseport_listen
 TEST_PROGS += test_vxlan_vnifiltering.sh
 TEST_GEN_FILES += bind_bhash_test
+TEST_GEN_FILES += sk_bind_sendto_listen
 
 TEST_FILES := settings
 
diff --git a/tools/testing/selftests/net/sk_bind_sendto_listen.c b/tools/testing/selftests/net/sk_bind_sendto_listen.c
new file mode 100644
index 000000000000..3e09c5631997
--- /dev/null
+++ b/tools/testing/selftests/net/sk_bind_sendto_listen.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include <arpa/inet.h>
+#include <error.h>
+#include <errno.h>
+#include <unistd.h>
+
+int main(void)
+{
+	int fd1, fd2, one = 1;
+	struct sockaddr_in6 bind_addr = {
+		.sin6_family = AF_INET6,
+		.sin6_port = htons(20000),
+		.sin6_flowinfo = htonl(0),
+		.sin6_addr = {},
+		.sin6_scope_id = 0,
+	};
+
+	inet_pton(AF_INET6, "::", &bind_addr.sin6_addr);
+
+	fd1 = socket(AF_INET6, SOCK_STREAM, IPPROTO_IP);
+	if (fd1 < 0) {
+		error(1, errno, "socket fd1");
+		return -1;
+	}
+
+	if (setsockopt(fd1, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one))) {
+		error(1, errno, "setsockopt(SO_REUSEADDR) fd1");
+		goto out_err1;
+	}
+
+	if (bind(fd1, (struct sockaddr *)&bind_addr, sizeof(bind_addr))) {
+		error(1, errno, "bind fd1");
+		goto out_err1;
+	}
+
+	if (sendto(fd1, NULL, 0, MSG_FASTOPEN, (struct sockaddr *)&bind_addr,
+		   sizeof(bind_addr))) {
+		error(1, errno, "sendto fd1");
+		goto out_err1;
+	}
+
+	fd2 = socket(AF_INET6, SOCK_STREAM, IPPROTO_IP);
+	if (fd2 < 0) {
+		error(1, errno, "socket fd2");
+		goto out_err1;
+	}
+
+	if (setsockopt(fd2, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one))) {
+		error(1, errno, "setsockopt(SO_REUSEADDR) fd2");
+		goto out_err2;
+	}
+
+	if (bind(fd2, (struct sockaddr *)&bind_addr, sizeof(bind_addr))) {
+		error(1, errno, "bind fd2");
+		goto out_err2;
+	}
+
+	if (sendto(fd2, NULL, 0, MSG_FASTOPEN, (struct sockaddr *)&bind_addr,
+		   sizeof(bind_addr)) != -1) {
+		error(1, errno, "sendto fd2");
+		goto out_err2;
+	}
+
+	if (listen(fd2, 0)) {
+		error(1, errno, "listen");
+		goto out_err2;
+	}
+
+	close(fd2);
+	close(fd1);
+	return 0;
+
+out_err2:
+	close(fd2);
+
+out_err1:
+	close(fd1);
+	return -1;
+}
-- 
2.30.2