selftests/namespaces: tenth inactive namespace resurrection test

Test that socket-kept netns can be reopened via file handle.
Verify that a network namespace kept alive by a socket FD can be
reopened using file handles even after the creating process exits.

Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-64-2e6f823ebdc0@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/tools/testing/selftests/namespaces/siocgskns_test.c b/tools/testing/selftests/namespaces/siocgskns_test.c
index 98f6a0e1b9dd16d22a570fbc769e10ac4da9d5b7..a909232dba365ff7f0d287c4ef958e27809d57ae 100644 (file)
--- a/tools/testing/selftests/namespaces/siocgskns_test.c
+++ b/tools/testing/selftests/namespaces/siocgskns_test.c
@@ -779,4 +779,199 @@ TEST(siocgskns_listns_visibility)
        TH_LOG("Netns %llu correctly disappeared from listns() after socket closed", netns_id);
 }
 
+/*
+ * Test that socket-kept netns can be reopened via file handle.
+ * Verify that a network namespace kept alive by a socket FD can be
+ * reopened using file handles even after the creating process exits.
+ */
+TEST(siocgskns_file_handle)
+{
+       int sock_fd, netns_fd, reopened_fd;
+       int ipc_sockets[2];
+       pid_t pid;
+       int status;
+       struct stat st1, st2;
+       ino_t netns_ino;
+       __u64 netns_id;
+       struct file_handle *handle;
+       struct nsfs_file_handle *nsfs_fh;
+       int ret;
+
+       /* Allocate file_handle structure for nsfs */
+       handle = malloc(sizeof(struct file_handle) + sizeof(struct nsfs_file_handle));
+       ASSERT_NE(handle, NULL);
+       handle->handle_bytes = sizeof(struct nsfs_file_handle);
+       handle->handle_type = FILEID_NSFS;
+
+       EXPECT_EQ(socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets), 0);
+
+       pid = fork();
+       ASSERT_GE(pid, 0);
+
+       if (pid == 0) {
+               /* Child: create new netns and socket */
+               close(ipc_sockets[0]);
+
+               if (unshare(CLONE_NEWNET) < 0) {
+                       close(ipc_sockets[1]);
+                       exit(1);
+               }
+
+               sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
+               if (sock_fd < 0) {
+                       close(ipc_sockets[1]);
+                       exit(1);
+               }
+
+               /* Send socket FD to parent via SCM_RIGHTS */
+               struct msghdr msg = {0};
+               struct iovec iov = {0};
+               char buf[1] = {'X'};
+               char cmsg_buf[CMSG_SPACE(sizeof(int))];
+
+               iov.iov_base = buf;
+               iov.iov_len = 1;
+               msg.msg_iov = &iov;
+               msg.msg_iovlen = 1;
+               msg.msg_control = cmsg_buf;
+               msg.msg_controllen = sizeof(cmsg_buf);
+
+               struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+               cmsg->cmsg_level = SOL_SOCKET;
+               cmsg->cmsg_type = SCM_RIGHTS;
+               cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+               memcpy(CMSG_DATA(cmsg), &sock_fd, sizeof(int));
+
+               if (sendmsg(ipc_sockets[1], &msg, 0) < 0) {
+                       close(sock_fd);
+                       close(ipc_sockets[1]);
+                       exit(1);
+               }
+
+               close(sock_fd);
+               close(ipc_sockets[1]);
+               exit(0);
+       }
+
+       /* Parent: receive socket FD */
+       close(ipc_sockets[1]);
+
+       struct msghdr msg = {0};
+       struct iovec iov = {0};
+       char buf[1];
+       char cmsg_buf[CMSG_SPACE(sizeof(int))];
+
+       iov.iov_base = buf;
+       iov.iov_len = 1;
+       msg.msg_iov = &iov;
+       msg.msg_iovlen = 1;
+       msg.msg_control = cmsg_buf;
+       msg.msg_controllen = sizeof(cmsg_buf);
+
+       ssize_t n = recvmsg(ipc_sockets[0], &msg, 0);
+       close(ipc_sockets[0]);
+       ASSERT_EQ(n, 1);
+
+       struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+       ASSERT_NE(cmsg, NULL);
+       memcpy(&sock_fd, CMSG_DATA(cmsg), sizeof(int));
+
+       /* Wait for child to exit */
+       waitpid(pid, &status, 0);
+       ASSERT_TRUE(WIFEXITED(status));
+       ASSERT_EQ(WEXITSTATUS(status), 0);
+
+       /* Get network namespace from socket */
+       netns_fd = ioctl(sock_fd, SIOCGSKNS);
+       if (netns_fd < 0) {
+               free(handle);
+               close(sock_fd);
+               if (errno == ENOTTY || errno == EINVAL)
+                       SKIP(return, "SIOCGSKNS not supported");
+               ASSERT_GE(netns_fd, 0);
+       }
+
+       ASSERT_EQ(fstat(netns_fd, &st1), 0);
+       netns_ino = st1.st_ino;
+
+       /* Get namespace ID */
+       ret = ioctl(netns_fd, NS_GET_ID, &netns_id);
+       if (ret < 0) {
+               free(handle);
+               close(sock_fd);
+               close(netns_fd);
+               if (errno == ENOTTY || errno == EINVAL)
+                       SKIP(return, "NS_GET_ID not supported");
+               ASSERT_EQ(ret, 0);
+       }
+
+       /* Construct file handle from namespace ID */
+       nsfs_fh = (struct nsfs_file_handle *)handle->f_handle;
+       nsfs_fh->ns_id = netns_id;
+       nsfs_fh->ns_type = 0;  /* Type field not needed for reopening */
+       nsfs_fh->ns_inum = 0;  /* Inum field not needed for reopening */
+
+       TH_LOG("Constructed file handle for netns %lu (id=%llu)", netns_ino, netns_id);
+
+       /* Reopen namespace using file handle (while socket still keeps it alive) */
+       reopened_fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       if (reopened_fd < 0) {
+               free(handle);
+               close(sock_fd);
+               if (errno == EOPNOTSUPP || errno == ENOSYS || errno == EBADF)
+                       SKIP(return, "open_by_handle_at with FD_NSFS_ROOT not supported");
+               TH_LOG("open_by_handle_at failed: %s", strerror(errno));
+               ASSERT_GE(reopened_fd, 0);
+       }
+
+       /* Verify it's the same namespace */
+       ASSERT_EQ(fstat(reopened_fd, &st2), 0);
+       ASSERT_EQ(st1.st_ino, st2.st_ino);
+       ASSERT_EQ(st1.st_dev, st2.st_dev);
+
+       TH_LOG("Successfully reopened netns %lu via file handle", netns_ino);
+
+       close(reopened_fd);
+
+       /* Close the netns FD */
+       close(netns_fd);
+
+       /* Try to reopen via file handle - should fail since namespace is now inactive */
+       reopened_fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       ASSERT_LT(reopened_fd, 0);
+       TH_LOG("Correctly failed to reopen inactive netns: %s", strerror(errno));
+
+       /* Get network namespace from socket */
+       netns_fd = ioctl(sock_fd, SIOCGSKNS);
+       if (netns_fd < 0) {
+               free(handle);
+               close(sock_fd);
+               if (errno == ENOTTY || errno == EINVAL)
+                       SKIP(return, "SIOCGSKNS not supported");
+               ASSERT_GE(netns_fd, 0);
+       }
+
+       /* Reopen namespace using file handle (while socket still keeps it alive) */
+       reopened_fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
+       if (reopened_fd < 0) {
+               free(handle);
+               close(sock_fd);
+               if (errno == EOPNOTSUPP || errno == ENOSYS || errno == EBADF)
+                       SKIP(return, "open_by_handle_at with FD_NSFS_ROOT not supported");
+               TH_LOG("open_by_handle_at failed: %s", strerror(errno));
+               ASSERT_GE(reopened_fd, 0);
+       }
+
+       /* Verify it's the same namespace */
+       ASSERT_EQ(fstat(reopened_fd, &st2), 0);
+       ASSERT_EQ(st1.st_ino, st2.st_ino);
+       ASSERT_EQ(st1.st_dev, st2.st_dev);
+
+       TH_LOG("Successfully reopened netns %lu via file handle", netns_ino);
+
+       /* Close socket - namespace should become inactive */
+       close(sock_fd);
+       free(handle);
+}
+
 TEST_HARNESS_MAIN