selftests/namespaces: fifth listns() test

Test that listns() only returns active namespaces.
Create a namespace, let it become inactive, verify it's not listed.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-43-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/listns_test.c b/tools/testing/selftests/namespaces/listns_test.c
index 457298cb4c64ad944df134ae7528a4b531c1d5c4..a04ebe11ce2ce0d0512b2877e398b8d163d4e5fe 100644 (file)
--- a/tools/testing/selftests/namespaces/listns_test.c
+++ b/tools/testing/selftests/namespaces/listns_test.c
@@ -201,4 +201,127 @@ TEST(listns_current_user)
                TH_LOG("  [%zd] ns_id: %llu", i, (unsigned long long)ns_ids[i]);
 }
 
+/*
+ * Test that listns() only returns active namespaces.
+ * Create a namespace, let it become inactive, verify it's not listed.
+ */
+TEST(listns_only_active)
+{
+       struct ns_id_req req = {
+               .size = sizeof(req),
+               .spare = 0,
+               .ns_id = 0,
+               .ns_type = CLONE_NEWNET,
+               .spare2 = 0,
+               .user_ns_id = 0,
+       };
+       __u64 ns_ids_before[100], ns_ids_after[100];
+       ssize_t ret_before, ret_after;
+       int pipefd[2];
+       pid_t pid;
+       __u64 new_ns_id = 0;
+       int status;
+
+       /* Get initial list */
+       ret_before = sys_listns(&req, ns_ids_before, ARRAY_SIZE(ns_ids_before), 0);
+       if (ret_before < 0) {
+               if (errno == ENOSYS)
+                       SKIP(return, "listns() not supported");
+               TH_LOG("listns failed: %s (errno=%d)", strerror(errno), errno);
+               ASSERT_TRUE(false);
+       }
+       ASSERT_GE(ret_before, 0);
+
+       TH_LOG("Before: %zd active network namespaces", ret_before);
+
+       /* Create a new namespace in a child process and get its ID */
+       ASSERT_EQ(pipe(pipefd), 0);
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               int fd;
+               __u64 ns_id;
+
+               close(pipefd[0]);
+
+               /* Create new network namespace */
+               if (unshare(CLONE_NEWNET) < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               /* Get its ID */
+               fd = open("/proc/self/ns/net", O_RDONLY);
+               if (fd < 0) {
+                       close(pipefd[1]);
+                       exit(1);
+               }
+
+               if (ioctl(fd, NS_GET_ID, &ns_id) < 0) {
+                       close(fd);
+                       close(pipefd[1]);
+                       exit(1);
+               }
+               close(fd);
+
+               /* Send ID to parent */
+               write(pipefd[1], &ns_id, sizeof(ns_id));
+               close(pipefd[1]);
+
+               /* Keep namespace active briefly */
+               usleep(100000);
+               exit(0);
+       }
+
+       /* Parent reads the new namespace ID */
+       {
+               int bytes;
+
+               close(pipefd[1]);
+               bytes = read(pipefd[0], &new_ns_id, sizeof(new_ns_id));
+               close(pipefd[0]);
+
+               if (bytes == sizeof(new_ns_id)) {
+                       __u64 ns_ids_during[100];
+                       int ret_during;
+
+                       TH_LOG("Child created namespace with ID %llu", (unsigned long long)new_ns_id);
+
+                       /* List namespaces while child is still alive - should see new one */
+                       ret_during = sys_listns(&req, ns_ids_during, ARRAY_SIZE(ns_ids_during), 0);
+                       ASSERT_GE(ret_during, 0);
+                       TH_LOG("During: %d active network namespaces", ret_during);
+
+                       /* Should have more namespaces than before */
+                       ASSERT_GE(ret_during, ret_before);
+               }
+       }
+
+       /* Wait for child to exit */
+       waitpid(pid, &status, 0);
+
+       /* Give time for namespace to become inactive */
+       usleep(100000);
+
+       /* List namespaces after child exits - should not see new one */
+       ret_after = sys_listns(&req, ns_ids_after, ARRAY_SIZE(ns_ids_after), 0);
+       ASSERT_GE(ret_after, 0);
+       TH_LOG("After: %zd active network namespaces", ret_after);
+
+       /* Verify the new namespace ID is not in the after list */
+       if (new_ns_id != 0) {
+               bool found = false;
+
+               for (ssize_t i = 0; i < ret_after; i++) {
+                       if (ns_ids_after[i] == new_ns_id) {
+                               found = true;
+                               break;
+                       }
+               }
+               ASSERT_FALSE(found);
+       }
+}
+
 TEST_HARNESS_MAIN