selftests/namespaces: third active reference count tests

Test that a namespace remains active while a process is using it,
even after the creating process exits.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-25-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/ns_active_ref_test.c b/tools/testing/selftests/namespaces/ns_active_ref_test.c
index 7cade298c754ddc522eb76ec4da1c16273f5888c..c2e34de7a3a9b0db396ee2e69473fdd93cc7d150 100644 (file)
--- a/tools/testing/selftests/namespaces/ns_active_ref_test.c
+++ b/tools/testing/selftests/namespaces/ns_active_ref_test.c
@@ -152,4 +152,128 @@ TEST(ns_inactive_after_exit)
        ASSERT_TRUE(errno == ENOENT || errno == ESTALE);
 }
 
+/*
+ * Test that a namespace remains active while a process is using it,
+ * even after the creating process exits.
+ */
+TEST(ns_active_with_multiple_processes)
+{
+       struct file_handle *handle;
+       int mount_id;
+       int ret;
+       int fd;
+       int pipefd[2];
+       int syncpipe[2];
+       pid_t pid1, pid2;
+       int status;
+       char buf[sizeof(*handle) + MAX_HANDLE_SZ];
+       char sync_byte;
+
+       /* Create pipes for communication */
+       ASSERT_EQ(pipe(pipefd), 0);
+       ASSERT_EQ(pipe(syncpipe), 0);
+
+       pid1 = fork();
+       ASSERT_GE(pid1, 0);
+
+       if (pid1 == 0) {
+               /* First child - creates namespace */
+               close(pipefd[0]);
+               close(syncpipe[1]);
+
+               /* Create new network namespace */
+               ret = unshare(CLONE_NEWNET);
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       close(syncpipe[0]);
+                       exit(1);
+               }
+
+               /* Open and get handle */
+               fd = open("/proc/self/ns/net", O_RDONLY);
+               if (fd < 0) {
+                       close(pipefd[1]);
+                       close(syncpipe[0]);
+                       exit(1);
+               }
+
+               handle = (struct file_handle *)buf;
+               handle->handle_bytes = MAX_HANDLE_SZ;
+               ret = name_to_handle_at(fd, "", handle, &mount_id, AT_EMPTY_PATH);
+               close(fd);
+
+               if (ret < 0) {
+                       close(pipefd[1]);
+                       close(syncpipe[0]);
+                       exit(1);
+               }
+
+               /* Send handle to parent */
+               write(pipefd[1], buf, sizeof(*handle) + handle->handle_bytes);
+               close(pipefd[1]);
+
+               /* Wait for signal before exiting */
+               read(syncpipe[0], &sync_byte, 1);
+               close(syncpipe[0]);
+               exit(0);
+       }
+
+       /* Parent reads handle */
+       close(pipefd[1]);
+       ret = read(pipefd[0], buf, sizeof(buf));
+       close(pipefd[0]);
+       ASSERT_GT(ret, 0);
+
+       handle = (struct file_handle *)buf;
+
+       /* Create second child that will keep namespace active */
+       pid2 = fork();
+       ASSERT_GE(pid2, 0);
+
+       if (pid2 == 0) {
+               /* Second child - reopens the namespace */
+               close(syncpipe[0]);
+               close(syncpipe[1]);
+
+               /* Open the namespace via handle */
+               fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+               if (fd < 0) {
+                       exit(1);
+               }
+
+               /* Join the namespace */
+               ret = setns(fd, CLONE_NEWNET);
+               close(fd);
+               if (ret < 0) {
+                       exit(1);
+               }
+
+               /* Sleep to keep namespace active */
+               sleep(1);
+               exit(0);
+       }
+
+       /* Let second child enter the namespace */
+       usleep(100000); /* 100ms */
+
+       /* Signal first child to exit */
+       close(syncpipe[0]);
+       sync_byte = 'X';
+       write(syncpipe[1], &sync_byte, 1);
+       close(syncpipe[1]);
+
+       /* Wait for first child */
+       waitpid(pid1, &status, 0);
+       ASSERT_TRUE(WIFEXITED(status));
+
+       /* Namespace should still be active because second child is using it */
+       fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       ASSERT_GE(fd, 0);
+       close(fd);
+
+       /* Wait for second child */
+       waitpid(pid2, &status, 0);
+       ASSERT_TRUE(WIFEXITED(status));
+}
+
 TEST_HARNESS_MAIN