[PATCH v2 62/63] selftests/namespaces: eleventh inactive namespace resurrection test

[Christian Brauner <brauner@kernel.org>]

Test combined listns() and file handle operations with socket-kept
netns. Create a netns, keep it alive with a socket, verify it appears in
listns(), then reopen it via file handle obtained from listns() entry.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 .../testing/selftests/namespaces/siocgskns_test.c  | 291 +++++++++++++++++++++
 1 file changed, 291 insertions(+)

diff --git a/tools/testing/selftests/namespaces/siocgskns_test.c b/tools/testing/selftests/namespaces/siocgskns_test.c
index 0ea5241f2b6f..a5a96509661e 100644
--- a/tools/testing/selftests/namespaces/siocgskns_test.c
+++ b/tools/testing/selftests/namespaces/siocgskns_test.c
@@ -984,4 +984,295 @@ TEST(siocgskns_file_handle)
 	free(handle);
 }
 
+/*
+ * Test combined listns() and file handle operations with socket-kept netns.
+ * Create a netns, keep it alive with a socket, verify it appears in listns(),
+ * then reopen it via file handle obtained from listns() entry.
+ */
+TEST(siocgskns_listns_and_file_handle)
+{
+	int sock_fd, netns_fd, userns_fd, reopened_fd;
+	int ipc_sockets[2];
+	pid_t pid;
+	int status;
+	struct stat st;
+	ino_t netns_ino;
+	__u64 netns_id, userns_id;
+	struct ns_id_req req = {
+		.size = sizeof(req),
+		.spare = 0,
+		.ns_id = 0,
+		.ns_type = CLONE_NEWNET | CLONE_NEWUSER,
+		.spare2 = 0,
+		.user_ns_id = 0,
+	};
+	__u64 ns_ids[256];
+	int ret, i;
+	bool found_netns = false, found_userns = false;
+	struct file_handle *handle;
+	struct nsfs_file_handle *nsfs_fh;
+
+	/* 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 userns and netns with socket */
+		close(ipc_sockets[0]);
+
+		if (setup_userns() < 0) {
+			close(ipc_sockets[1]);
+			exit(1);
+		}
+
+		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));
+	if (WEXITSTATUS(status) != 0) {
+		free(handle);
+		SKIP(close(sock_fd); return, "Child failed to create namespace");
+	}
+
+	/* 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, &st), 0);
+	netns_ino = st.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);
+	}
+
+	/* Get owner user namespace */
+	userns_fd = ioctl(netns_fd, NS_GET_USERNS);
+	if (userns_fd < 0) {
+		free(handle);
+		close(sock_fd);
+		close(netns_fd);
+		if (errno == ENOTTY || errno == EINVAL)
+			SKIP(return, "NS_GET_USERNS not supported");
+		ASSERT_GE(userns_fd, 0);
+	}
+
+	/* Get owner namespace ID */
+	ret = ioctl(userns_fd, NS_GET_ID, &userns_id);
+	if (ret < 0) {
+		close(userns_fd);
+		free(handle);
+		close(sock_fd);
+		close(netns_fd);
+		ASSERT_EQ(ret, 0);
+	}
+	close(userns_fd);
+
+	TH_LOG("Testing netns %lu (id=%llu) owned by userns id=%llu", netns_ino, netns_id, userns_id);
+
+	/* Verify namespace appears in listns() */
+	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+	if (ret < 0) {
+		free(handle);
+		close(sock_fd);
+		close(netns_fd);
+		if (errno == ENOSYS)
+			SKIP(return, "listns() not supported");
+		TH_LOG("listns failed: %s", strerror(errno));
+		ASSERT_GE(ret, 0);
+	}
+
+	found_netns = false;
+	found_userns = false;
+	for (i = 0; i < ret; i++) {
+		if (ns_ids[i] == netns_id)
+			found_netns = true;
+		if (ns_ids[i] == userns_id)
+			found_userns = true;
+	}
+	ASSERT_TRUE(found_netns);
+	ASSERT_TRUE(found_userns);
+	TH_LOG("Found netns %llu in listns() output", netns_id);
+
+	/* 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;
+	nsfs_fh->ns_inum = 0;
+
+	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);
+	}
+
+	struct stat reopened_st;
+	ASSERT_EQ(fstat(reopened_fd, &reopened_st), 0);
+	ASSERT_EQ(reopened_st.st_ino, netns_ino);
+
+	TH_LOG("Successfully reopened netns %lu via file handle (socket-kept)", netns_ino);
+
+	close(reopened_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);
+	if (reopened_fd >= 0) {
+		/* This might succeed if there's still a reference somewhere */
+		TH_LOG("Warning: reopened netns after socket closed (fd=%d)", reopened_fd);
+		close(reopened_fd);
+	} else {
+		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);
+	}
+
+	/* Verify namespace appears in listns() */
+	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+	if (ret < 0) {
+		free(handle);
+		close(sock_fd);
+		close(netns_fd);
+		if (errno == ENOSYS)
+			SKIP(return, "listns() not supported");
+		TH_LOG("listns failed: %s", strerror(errno));
+		ASSERT_GE(ret, 0);
+	}
+
+	found_netns = false;
+	found_userns = false;
+	for (i = 0; i < ret; i++) {
+		if (ns_ids[i] == netns_id)
+			found_netns = true;
+		if (ns_ids[i] == userns_id)
+			found_userns = true;
+	}
+	ASSERT_TRUE(found_netns);
+	ASSERT_TRUE(found_userns);
+	TH_LOG("Found netns %llu in listns() output", netns_id);
+
+	close(netns_fd);
+
+	/* Verify namespace appears in listns() */
+	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
+	if (ret < 0) {
+		free(handle);
+		close(sock_fd);
+		close(netns_fd);
+		if (errno == ENOSYS)
+			SKIP(return, "listns() not supported");
+		TH_LOG("listns failed: %s", strerror(errno));
+		ASSERT_GE(ret, 0);
+	}
+
+	found_netns = false;
+	found_userns = false;
+	for (i = 0; i < ret; i++) {
+		if (ns_ids[i] == netns_id)
+			found_netns = true;
+		if (ns_ids[i] == userns_id)
+			found_userns = true;
+	}
+	ASSERT_FALSE(found_netns);
+	ASSERT_FALSE(found_userns);
+	TH_LOG("Netns %llu correctly disappeared from listns() after socket closed", netns_id);
+
+	close(sock_fd);
+	free(handle);
+}
+
 TEST_HARNESS_MAIN

-- 
2.47.3