From: Christian Brauner <brauner@kernel.org>

Add tests for SO_PEERPIDFD_THREAD.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>
Signed-off-by: Andrew Halaney <andrew@amutable.com>
---
 tools/testing/selftests/net/af_unix/scm_pidfd.c | 97 +++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

diff --git a/tools/testing/selftests/net/af_unix/scm_pidfd.c b/tools/testing/selftests/net/af_unix/scm_pidfd.c
index d73ae9d27a48..cbe53fab44fc 100644
--- a/tools/testing/selftests/net/af_unix/scm_pidfd.c
+++ b/tools/testing/selftests/net/af_unix/scm_pidfd.c
@@ -36,6 +36,10 @@
 #define SO_PASSPIDFD_THREAD 86
 #endif
 
+#ifndef SO_PEERPIDFD_THREAD
+#define SO_PEERPIDFD_THREAD 87
+#endif
+
 #define CHILD_EXIT_CODE_OK 123
 
 static void child_die()
@@ -1058,4 +1062,97 @@ TEST(scm_pidfd_thread_creds)
 	EXPECT_EQ(msg.ids.pid, msg.thread_info.tgid);
 }
 
+static void *peer_connect_thread(void *arg)
+{
+	struct sock_addr *sa = arg;
+	struct thread_ids ids = {
+		.pid = getpid(),
+		.tid = gettid(),
+	};
+	int fd;
+	char sync;
+
+	fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (fd < 0)
+		return (void *)1;
+
+	if (connect(fd, (struct sockaddr *)&sa->listen_addr, sa->addrlen))
+		return (void *)1;
+
+	if (send(fd, &ids, sizeof(ids), 0) != sizeof(ids))
+		return (void *)1;
+
+	/* stay alive until the server has looked at our pidfd */
+	if (read(fd, &sync, 1) != 1)
+		return (void *)1;
+
+	close(fd);
+	return NULL;
+}
+
+static int peer_pidfd_info(int fd, int optname, struct pidfd_info *info)
+{
+	int pidfd;
+	socklen_t len = sizeof(pidfd);
+
+	if (getsockopt(fd, SOL_SOCKET, optname, &pidfd, &len)) {
+		log_err("getsockopt(SO_PEERPIDFD*)");
+		return -1;
+	}
+
+	info->mask = PIDFD_INFO_PID;
+	if (ioctl(pidfd, PIDFD_GET_INFO, info)) {
+		log_err("ioctl(PIDFD_GET_INFO)");
+		close(pidfd);
+		return -1;
+	}
+
+	close(pidfd);
+	return 0;
+}
+
+/* SO_PEERPIDFD_THREAD returns a pidfd for the peer's connecting thread. */
+TEST(so_peerpidfd_thread)
+{
+	struct sock_addr sa;
+	struct thread_ids ids;
+	struct pidfd_info info;
+	pthread_t thread;
+	void *tret;
+	int server, cfd;
+
+	server = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, server);
+
+	fill_sockaddr(&sa, true);
+	ASSERT_EQ(0, bind(server, (struct sockaddr *)&sa.listen_addr, sa.addrlen));
+	ASSERT_EQ(0, listen(server, 1));
+
+	ASSERT_EQ(0, pthread_create(&thread, NULL, peer_connect_thread, &sa));
+
+	cfd = accept(server, NULL, NULL);
+	ASSERT_LE(0, cfd);
+
+	ASSERT_EQ(sizeof(ids), recv(cfd, &ids, sizeof(ids), MSG_WAITALL));
+	ASSERT_NE(ids.pid, ids.tid);
+
+	/* SO_PEERPIDFD refers to the peer's thread-group. */
+	ASSERT_EQ(0, peer_pidfd_info(cfd, SO_PEERPIDFD, &info));
+	EXPECT_EQ(ids.pid, info.pid);
+	EXPECT_EQ(ids.pid, info.tgid);
+
+	/* SO_PEERPIDFD_THREAD refers to the connecting thread. */
+	ASSERT_EQ(0, peer_pidfd_info(cfd, SO_PEERPIDFD_THREAD, &info));
+	EXPECT_EQ(ids.tid, info.pid);
+	EXPECT_EQ(ids.pid, info.tgid);
+
+	/* release the connecting thread */
+	ASSERT_EQ(1, write(cfd, "x", 1));
+	ASSERT_EQ(0, pthread_join(thread, &tret));
+	ASSERT_EQ(NULL, tret);
+
+	close(cfd);
+	close(server);
+}
+
 TEST_HARNESS_MAIN

-- 
2.55.0