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Message-Id: <20251024-work-namespace-nstree-listns-v3-63-b6241981b72b@kernel.org>
Date: Fri, 24 Oct 2025 12:53:32 +0200
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>,
Jeff Layton <jlayton@...nel.org>
Cc: Jann Horn <jannh@...gle.com>, Mike Yuan <me@...dnzj.com>,
Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
Lennart Poettering <mzxreary@...inter.de>,
Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>,
Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>,
Johannes Weiner <hannes@...xchg.org>, Thomas Gleixner <tglx@...utronix.de>,
Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, bpf@...r.kernel.org,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
Christian Brauner <brauner@...nel.org>
Subject: [PATCH v3 63/70] selftests/namespaces: eleventh inactive namespace
resurrection test
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@...nel.org>
---
.../testing/selftests/namespaces/siocgskns_test.c | 283 +++++++++++++++++++++
1 file changed, 283 insertions(+)
diff --git a/tools/testing/selftests/namespaces/siocgskns_test.c b/tools/testing/selftests/namespaces/siocgskns_test.c
index a909232dba36..706049768d52 100644
--- a/tools/testing/selftests/namespaces/siocgskns_test.c
+++ b/tools/testing/selftests/namespaces/siocgskns_test.c
@@ -974,4 +974,287 @@ 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));
+ 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, &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);
+ 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);
+ }
+
+ /* 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
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