cubelinux-kernel/tools/testing/selftests/namespaces/siocgskns_test.c

// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <sched.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <linux/if.h>
#include <linux/sockios.h>
#include <linux/nsfs.h>
#include <arpa/inet.h>
#include "../kselftest_harness.h"
#include "../filesystems/utils.h"
#include "wrappers.h"

#ifndef SIOCGSKNS
#define SIOCGSKNS 0x894C
#endif

#ifndef FD_NSFS_ROOT
#define FD_NSFS_ROOT -10003
#endif

#ifndef FILEID_NSFS
#define FILEID_NSFS 0xf1
#endif

/*
 * Test basic SIOCGSKNS functionality.
 * Create a socket and verify SIOCGSKNS returns the correct network namespace.
 */
TEST(siocgskns_basic)
{
	int sock_fd, netns_fd, current_netns_fd;
	struct stat st1, st2;

	/* Create a TCP socket */
	sock_fd = socket(AF_INET, SOCK_STREAM, 0);
	ASSERT_GE(sock_fd, 0);

	/* Use SIOCGSKNS to get network namespace */
	netns_fd = ioctl(sock_fd, SIOCGSKNS);
	if (netns_fd < 0) {
		close(sock_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(netns_fd, 0);
	}

	/* Get current network namespace */
	current_netns_fd = open("/proc/self/ns/net", O_RDONLY);
	ASSERT_GE(current_netns_fd, 0);

	/* Verify they match */
	ASSERT_EQ(fstat(netns_fd, &st1), 0);
	ASSERT_EQ(fstat(current_netns_fd, &st2), 0);
	ASSERT_EQ(st1.st_ino, st2.st_ino);

	close(sock_fd);
	close(netns_fd);
	close(current_netns_fd);
}

/*
 * Test that socket file descriptors keep network namespaces active.
 * Create a network namespace, create a socket in it, then exit the namespace.
 * The namespace should remain active while the socket FD is held.
 */
TEST(siocgskns_keeps_netns_active)
{
	int sock_fd, netns_fd, test_fd;
	int ipc_sockets[2];
	pid_t pid;
	int status;
	struct stat st;

	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) {
			TH_LOG("unshare(CLONE_NEWNET) failed: %s", strerror(errno));
			close(ipc_sockets[1]);
			exit(1);
		}

		/* Create a socket in the new network namespace */
		sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
		if (sock_fd < 0) {
			TH_LOG("socket() failed: %s", strerror(errno));
			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);
	ASSERT_EQ(cmsg->cmsg_type, SCM_RIGHTS);

	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) {
		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);

	/*
	 * Namespace should still be active because socket FD keeps it alive.
	 * Try to access it via /proc/self/fd/<fd>.
	 */
	char path[64];
	snprintf(path, sizeof(path), "/proc/self/fd/%d", netns_fd);
	test_fd = open(path, O_RDONLY);
	ASSERT_GE(test_fd, 0);
	close(test_fd);
	close(netns_fd);

	/* Close socket - namespace should become inactive */
	close(sock_fd);

	/* Try SIOCGSKNS again - should fail since socket is closed */
	ASSERT_LT(ioctl(sock_fd, SIOCGSKNS), 0);
}

/*
 * Test SIOCGSKNS with different socket types (TCP, UDP, RAW).
 */
TEST(siocgskns_socket_types)
{
	int sock_tcp, sock_udp, sock_raw;
	int netns_tcp, netns_udp, netns_raw;
	struct stat st_tcp, st_udp, st_raw;

	/* TCP socket */
	sock_tcp = socket(AF_INET, SOCK_STREAM, 0);
	ASSERT_GE(sock_tcp, 0);

	/* UDP socket */
	sock_udp = socket(AF_INET, SOCK_DGRAM, 0);
	ASSERT_GE(sock_udp, 0);

	/* RAW socket (may require privileges) */
	sock_raw = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
	if (sock_raw < 0 && (errno == EPERM || errno == EACCES)) {
		sock_raw = -1; /* Skip raw socket test */
	}

	/* Test SIOCGSKNS on TCP */
	netns_tcp = ioctl(sock_tcp, SIOCGSKNS);
	if (netns_tcp < 0) {
		close(sock_tcp);
		close(sock_udp);
		if (sock_raw >= 0) close(sock_raw);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(netns_tcp, 0);
	}

	/* Test SIOCGSKNS on UDP */
	netns_udp = ioctl(sock_udp, SIOCGSKNS);
	ASSERT_GE(netns_udp, 0);

	/* Test SIOCGSKNS on RAW (if available) */
	if (sock_raw >= 0) {
		netns_raw = ioctl(sock_raw, SIOCGSKNS);
		ASSERT_GE(netns_raw, 0);
	}

	/* Verify all return the same network namespace */
	ASSERT_EQ(fstat(netns_tcp, &st_tcp), 0);
	ASSERT_EQ(fstat(netns_udp, &st_udp), 0);
	ASSERT_EQ(st_tcp.st_ino, st_udp.st_ino);

	if (sock_raw >= 0) {
		ASSERT_EQ(fstat(netns_raw, &st_raw), 0);
		ASSERT_EQ(st_tcp.st_ino, st_raw.st_ino);
		close(netns_raw);
		close(sock_raw);
	}

	close(netns_tcp);
	close(netns_udp);
	close(sock_tcp);
	close(sock_udp);
}

/*
 * Test SIOCGSKNS across setns.
 * Create a socket in netns A, switch to netns B, verify SIOCGSKNS still
 * returns netns A.
 */
TEST(siocgskns_across_setns)
{
	int sock_fd, netns_a_fd, netns_b_fd, result_fd;
	struct stat st_a;

	/* Get current netns (A) */
	netns_a_fd = open("/proc/self/ns/net", O_RDONLY);
	ASSERT_GE(netns_a_fd, 0);
	ASSERT_EQ(fstat(netns_a_fd, &st_a), 0);

	/* Create socket in netns A */
	sock_fd = socket(AF_INET, SOCK_STREAM, 0);
	ASSERT_GE(sock_fd, 0);

	/* Create new netns (B) */
	ASSERT_EQ(unshare(CLONE_NEWNET), 0);

	netns_b_fd = open("/proc/self/ns/net", O_RDONLY);
	ASSERT_GE(netns_b_fd, 0);

	/* Get netns from socket created in A */
	result_fd = ioctl(sock_fd, SIOCGSKNS);
	if (result_fd < 0) {
		close(sock_fd);
		setns(netns_a_fd, CLONE_NEWNET);
		close(netns_a_fd);
		close(netns_b_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(result_fd, 0);
	}

	/* Verify it still points to netns A */
	struct stat st_result_stat;
	ASSERT_EQ(fstat(result_fd, &st_result_stat), 0);
	ASSERT_EQ(st_a.st_ino, st_result_stat.st_ino);

	close(result_fd);
	close(sock_fd);
	close(netns_b_fd);

	/* Restore original netns */
	ASSERT_EQ(setns(netns_a_fd, CLONE_NEWNET), 0);
	close(netns_a_fd);
}

/*
 * Test SIOCGSKNS fails on non-socket file descriptors.
 */
TEST(siocgskns_non_socket)
{
	int fd;
	int pipefd[2];

	/* Test on regular file */
	fd = open("/dev/null", O_RDONLY);
	ASSERT_GE(fd, 0);

	ASSERT_LT(ioctl(fd, SIOCGSKNS), 0);
	ASSERT_TRUE(errno == ENOTTY || errno == EINVAL);
	close(fd);

	/* Test on pipe */
	ASSERT_EQ(pipe(pipefd), 0);

	ASSERT_LT(ioctl(pipefd[0], SIOCGSKNS), 0);
	ASSERT_TRUE(errno == ENOTTY || errno == EINVAL);

	close(pipefd[0]);
	close(pipefd[1]);
}

/*
 * Test multiple sockets keep the same network namespace active.
 * Create multiple sockets, verify closing some doesn't affect others.
 */
TEST(siocgskns_multiple_sockets)
{
	int socks[5];
	int netns_fds[5];
	int i;
	struct stat st;
	ino_t netns_ino;

	/* Create new network namespace */
	ASSERT_EQ(unshare(CLONE_NEWNET), 0);

	/* Create multiple sockets */
	for (i = 0; i < 5; i++) {
		socks[i] = socket(AF_INET, SOCK_STREAM, 0);
		ASSERT_GE(socks[i], 0);
	}

	/* Get netns from all sockets */
	for (i = 0; i < 5; i++) {
		netns_fds[i] = ioctl(socks[i], SIOCGSKNS);
		if (netns_fds[i] < 0) {
			int j;
			for (j = 0; j <= i; j++) {
				close(socks[j]);
				if (j < i && netns_fds[j] >= 0)
					close(netns_fds[j]);
			}
			if (errno == ENOTTY || errno == EINVAL)
				SKIP(return, "SIOCGSKNS not supported");
			ASSERT_GE(netns_fds[i], 0);
		}
	}

	/* Verify all point to same netns */
	ASSERT_EQ(fstat(netns_fds[0], &st), 0);
	netns_ino = st.st_ino;

	for (i = 1; i < 5; i++) {
		ASSERT_EQ(fstat(netns_fds[i], &st), 0);
		ASSERT_EQ(st.st_ino, netns_ino);
	}

	/* Close some sockets */
	for (i = 0; i < 3; i++) {
		close(socks[i]);
	}

	/* Remaining netns FDs should still be valid */
	for (i = 3; i < 5; i++) {
		char path[64];
		snprintf(path, sizeof(path), "/proc/self/fd/%d", netns_fds[i]);
		int test_fd = open(path, O_RDONLY);
		ASSERT_GE(test_fd, 0);
		close(test_fd);
	}

	/* Cleanup */
	for (i = 0; i < 5; i++) {
		if (i >= 3)
			close(socks[i]);
		close(netns_fds[i]);
	}
}

/*
 * Test socket keeps netns active after creating process exits.
 * Verify that as long as the socket FD exists, the namespace remains active.
 */
TEST(siocgskns_netns_lifecycle)
{
	int sock_fd, netns_fd;
	int ipc_sockets[2];
	int syncpipe[2];
	pid_t pid;
	int status;
	char sync_byte;
	struct stat st;
	ino_t netns_ino;

	EXPECT_EQ(socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_sockets), 0);

	ASSERT_EQ(pipe(syncpipe), 0);

	pid = fork();
	ASSERT_GE(pid, 0);

	if (pid == 0) {
		/* Child */
		close(ipc_sockets[0]);
		close(syncpipe[1]);

		if (unshare(CLONE_NEWNET) < 0) {
			close(ipc_sockets[1]);
			close(syncpipe[0]);
			exit(1);
		}

		sock_fd = socket(AF_INET, SOCK_STREAM, 0);
		if (sock_fd < 0) {
			close(ipc_sockets[1]);
			close(syncpipe[0]);
			exit(1);
		}

		/* Send socket to parent */
		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]);
			close(syncpipe[0]);
			exit(1);
		}

		close(sock_fd);
		close(ipc_sockets[1]);

		/* Wait for parent signal */
		read(syncpipe[0], &sync_byte, 1);
		close(syncpipe[0]);
		exit(0);
	}

	/* Parent */
	close(ipc_sockets[1]);
	close(syncpipe[0]);

	/* Receive socket FD */
	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));

	/* Get netns from socket while child is alive */
	netns_fd = ioctl(sock_fd, SIOCGSKNS);
	if (netns_fd < 0) {
		sync_byte = 'G';
		write(syncpipe[1], &sync_byte, 1);
		close(syncpipe[1]);
		close(sock_fd);
		waitpid(pid, NULL, 0);
		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;

	/* Signal child to exit */
	sync_byte = 'G';
	write(syncpipe[1], &sync_byte, 1);
	close(syncpipe[1]);

	waitpid(pid, &status, 0);
	ASSERT_TRUE(WIFEXITED(status));

	/*
	 * Socket FD should still keep namespace active even after
	 * the creating process exited.
	 */
	int test_fd = ioctl(sock_fd, SIOCGSKNS);
	ASSERT_GE(test_fd, 0);

	struct stat st_test;
	ASSERT_EQ(fstat(test_fd, &st_test), 0);
	ASSERT_EQ(st_test.st_ino, netns_ino);

	close(test_fd);
	close(netns_fd);

	/* Close socket - namespace should become inactive */
	close(sock_fd);
}

/*
 * Test IPv6 sockets also work with SIOCGSKNS.
 */
TEST(siocgskns_ipv6)
{
	int sock_fd, netns_fd, current_netns_fd;
	struct stat st1, st2;

	/* Create an IPv6 TCP socket */
	sock_fd = socket(AF_INET6, SOCK_STREAM, 0);
	ASSERT_GE(sock_fd, 0);

	/* Use SIOCGSKNS */
	netns_fd = ioctl(sock_fd, SIOCGSKNS);
	if (netns_fd < 0) {
		close(sock_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(netns_fd, 0);
	}

	/* Verify it matches current namespace */
	current_netns_fd = open("/proc/self/ns/net", O_RDONLY);
	ASSERT_GE(current_netns_fd, 0);

	ASSERT_EQ(fstat(netns_fd, &st1), 0);
	ASSERT_EQ(fstat(current_netns_fd, &st2), 0);
	ASSERT_EQ(st1.st_ino, st2.st_ino);

	close(sock_fd);
	close(netns_fd);
	close(current_netns_fd);
}

/*
 * Test that socket-kept netns appears in listns() output.
 * Verify that a network namespace kept alive by a socket FD appears in
 * listns() output even after the creating process exits, and that it
 * disappears when the socket is closed.
 */
TEST(siocgskns_listns_visibility)
{
	int sock_fd, netns_fd, owner_fd;
	int ipc_sockets[2];
	pid_t pid;
	int status;
	__u64 netns_id, owner_id;
	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[256];
	int ret, i;
	bool found_netns = false;

	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) {
		close(sock_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(netns_fd, 0);
	}

	/* Get namespace ID */
	ret = ioctl(netns_fd, NS_GET_ID, &netns_id);
	if (ret < 0) {
		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 */
	owner_fd = ioctl(netns_fd, NS_GET_USERNS);
	if (owner_fd < 0) {
		close(sock_fd);
		close(netns_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "NS_GET_USERNS not supported");
		ASSERT_GE(owner_fd, 0);
	}

	/* Get owner namespace ID */
	ret = ioctl(owner_fd, NS_GET_ID, &owner_id);
	if (ret < 0) {
		close(owner_fd);
		close(sock_fd);
		close(netns_fd);
		ASSERT_EQ(ret, 0);
	}
	close(owner_fd);

	/* Namespace should appear in listns() output */
	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	if (ret < 0) {
		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);
	}

	/* Search for our network namespace in the list */
	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_id) {
			found_netns = true;
			break;
		}
	}

	ASSERT_TRUE(found_netns);
	TH_LOG("Found netns %llu in listns() output (kept alive by socket)", netns_id);

	/* Now verify with owner filtering */
	req.user_ns_id = owner_id;
	found_netns = false;

	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	ASSERT_GE(ret, 0);

	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_id) {
			found_netns = true;
			break;
		}
	}

	ASSERT_TRUE(found_netns);
	TH_LOG("Found netns %llu owned by userns %llu", netns_id, owner_id);

	/* Close socket - namespace should become inactive and disappear from listns() */
	close(sock_fd);
	close(netns_fd);

	/* Verify it's no longer in listns() output */
	req.user_ns_id = 0;
	found_netns = false;

	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	ASSERT_GE(ret, 0);

	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_id) {
			found_netns = true;
			break;
		}
	}

	ASSERT_FALSE(found_netns);
	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 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 multi-level namespace resurrection across three user namespace levels.
 *
 * This test creates a complex namespace hierarchy with three levels of user
 * namespaces and a network namespace at the deepest level. It verifies that
 * the resurrection semantics work correctly when SIOCGSKNS is called on a
 * socket from an inactive namespace tree, and that listns() and
 * open_by_handle_at() correctly respect visibility rules.
 *
 * Hierarchy after child processes exit (all with 0 active refcount):
 *
 *          net_L3A (0)                <- Level 3 network namespace
 *              |
 *              +
 *          userns_L3 (0)              <- Level 3 user namespace
 *              |
 *              +
 *          userns_L2 (0)              <- Level 2 user namespace
 *              |
 *              +
 *          userns_L1 (0)              <- Level 1 user namespace
 *              |
 *              x
 *          init_user_ns
 *
 * The test verifies:
 * 1. SIOCGSKNS on a socket from inactive net_L3A resurrects the entire chain
 * 2. After resurrection, all namespaces are visible in listns()
 * 3. Resurrected namespaces can be reopened via file handles
 * 4. Closing the netns FD cascades down: the entire ownership chain
 *    (userns_L3 -> userns_L2 -> userns_L1) becomes inactive again
 * 5. Inactive namespaces disappear from listns() and cannot be reopened
 * 6. Calling SIOCGSKNS again on the same socket resurrects the tree again
 * 7. After second resurrection, namespaces are visible and can be reopened
 */
TEST(siocgskns_multilevel_resurrection)
{
	int ipc_sockets[2];
	pid_t pid_l1, pid_l2, pid_l3;
	int status;

	/* Namespace file descriptors to be received from child */
	int sock_L3A_fd = -1;
	int netns_L3A_fd = -1;
	__u64 netns_L3A_id;
	__u64 userns_L1_id, userns_L2_id, userns_L3_id;

	/* For listns() and file handle testing */
	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;
	struct file_handle *handle;
	struct nsfs_file_handle *nsfs_fh;
	int reopened_fd;

	/* Allocate file handle for testing */
	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);

	/*
	 * Fork level 1 child that creates userns_L1
	 */
	pid_l1 = fork();
	ASSERT_GE(pid_l1, 0);

	if (pid_l1 == 0) {
		/* Level 1 child */
		int ipc_L2[2];
		close(ipc_sockets[0]);

		/* Create userns_L1 */
		if (setup_userns() < 0) {
			close(ipc_sockets[1]);
			exit(1);
		}

		/* Create socketpair for communicating with L2 child */
		if (socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_L2) < 0) {
			close(ipc_sockets[1]);
			exit(1);
		}

		/*
		 * Fork level 2 child that creates userns_L2
		 */
		pid_l2 = fork();
		if (pid_l2 < 0) {
			close(ipc_sockets[1]);
			close(ipc_L2[0]);
			close(ipc_L2[1]);
			exit(1);
		}

		if (pid_l2 == 0) {
			/* Level 2 child */
			int ipc_L3[2];
			close(ipc_L2[0]);

			/* Create userns_L2 (nested inside userns_L1) */
			if (setup_userns() < 0) {
				close(ipc_L2[1]);
				exit(1);
			}

			/* Create socketpair for communicating with L3 child */
			if (socketpair(AF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, ipc_L3) < 0) {
				close(ipc_L2[1]);
				exit(1);
			}

			/*
			 * Fork level 3 child that creates userns_L3 and network namespaces
			 */
			pid_l3 = fork();
			if (pid_l3 < 0) {
				close(ipc_L2[1]);
				close(ipc_L3[0]);
				close(ipc_L3[1]);
				exit(1);
			}

			if (pid_l3 == 0) {
				/* Level 3 child - the deepest level */
				int sock_fd;
				close(ipc_L3[0]);

				/* Create userns_L3 (nested inside userns_L2) */
				if (setup_userns() < 0) {
					close(ipc_L3[1]);
					exit(1);
				}

				/* Create network namespace at level 3 */
				if (unshare(CLONE_NEWNET) < 0) {
					close(ipc_L3[1]);
					exit(1);
				}

				/* Create socket in net_L3A */
				sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
				if (sock_fd < 0) {
					close(ipc_L3[1]);
					exit(1);
				}

				/* Send socket FD to L2 parent */
				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_L3[1], &msg, 0) < 0) {
					close(sock_fd);
					close(ipc_L3[1]);
					exit(1);
				}

				close(sock_fd);
				close(ipc_L3[1]);
				exit(0);
			}

			/* Level 2 child - receive from L3 and forward to L1 */
			close(ipc_L3[1]);

			struct msghdr msg = {0};
			struct iovec iov = {0};
			char buf[1];
			char cmsg_buf[CMSG_SPACE(sizeof(int))];
			int received_fd;

			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_L3[0], &msg, 0);
			close(ipc_L3[0]);

			if (n != 1) {
				close(ipc_L2[1]);
				waitpid(pid_l3, NULL, 0);
				exit(1);
			}

			struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
			if (!cmsg) {
				close(ipc_L2[1]);
				waitpid(pid_l3, NULL, 0);
				exit(1);
			}
			memcpy(&received_fd, CMSG_DATA(cmsg), sizeof(int));

			/* Wait for L3 child */
			waitpid(pid_l3, NULL, 0);

			/* Forward the socket FD to L1 parent */
			memset(&msg, 0, sizeof(msg));
			buf[0] = 'Y';
			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);

			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), &received_fd, sizeof(int));

			if (sendmsg(ipc_L2[1], &msg, 0) < 0) {
				close(received_fd);
				close(ipc_L2[1]);
				exit(1);
			}

			close(received_fd);
			close(ipc_L2[1]);
			exit(0);
		}

		/* Level 1 child - receive from L2 and forward to parent */
		close(ipc_L2[1]);

		struct msghdr msg = {0};
		struct iovec iov = {0};
		char buf[1];
		char cmsg_buf[CMSG_SPACE(sizeof(int))];
		int received_fd;

		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_L2[0], &msg, 0);
		close(ipc_L2[0]);

		if (n != 1) {
			close(ipc_sockets[1]);
			waitpid(pid_l2, NULL, 0);
			exit(1);
		}

		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
		if (!cmsg) {
			close(ipc_sockets[1]);
			waitpid(pid_l2, NULL, 0);
			exit(1);
		}
		memcpy(&received_fd, CMSG_DATA(cmsg), sizeof(int));

		/* Wait for L2 child */
		waitpid(pid_l2, NULL, 0);

		/* Forward the socket FD to parent */
		memset(&msg, 0, sizeof(msg));
		buf[0] = 'Z';
		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);

		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), &received_fd, sizeof(int));

		if (sendmsg(ipc_sockets[1], &msg, 0) < 0) {
			close(received_fd);
			close(ipc_sockets[1]);
			exit(1);
		}

		close(received_fd);
		close(ipc_sockets[1]);
		exit(0);
	}

	/* Parent - receive the socket from the deepest level */
	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]);

	if (n != 1) {
		free(handle);
		waitpid(pid_l1, NULL, 0);
		SKIP(return, "Failed to receive socket from child");
	}

	struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
	if (!cmsg) {
		free(handle);
		waitpid(pid_l1, NULL, 0);
		SKIP(return, "Failed to receive socket from child");
	}
	memcpy(&sock_L3A_fd, CMSG_DATA(cmsg), sizeof(int));

	/* Wait for L1 child */
	waitpid(pid_l1, &status, 0);
	ASSERT_TRUE(WIFEXITED(status));
	ASSERT_EQ(WEXITSTATUS(status), 0);

	/*
	 * At this point, all child processes have exited. The socket itself
	 * doesn't keep the namespace active - we need to call SIOCGSKNS which
	 * will resurrect the entire namespace tree by taking active references.
	 */

	/* Get network namespace from socket - this resurrects the tree */
	netns_L3A_fd = ioctl(sock_L3A_fd, SIOCGSKNS);
	if (netns_L3A_fd < 0) {
		free(handle);
		close(sock_L3A_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "SIOCGSKNS not supported");
		ASSERT_GE(netns_L3A_fd, 0);
	}

	/* Get namespace ID for net_L3A */
	ret = ioctl(netns_L3A_fd, NS_GET_ID, &netns_L3A_id);
	if (ret < 0) {
		free(handle);
		close(sock_L3A_fd);
		close(netns_L3A_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "NS_GET_ID not supported");
		ASSERT_EQ(ret, 0);
	}

	/* Get owner user namespace chain: userns_L3 -> userns_L2 -> userns_L1 */
	int userns_L3_fd = ioctl(netns_L3A_fd, NS_GET_USERNS);
	if (userns_L3_fd < 0) {
		free(handle);
		close(sock_L3A_fd);
		close(netns_L3A_fd);
		if (errno == ENOTTY || errno == EINVAL)
			SKIP(return, "NS_GET_USERNS not supported");
		ASSERT_GE(userns_L3_fd, 0);
	}

	ret = ioctl(userns_L3_fd, NS_GET_ID, &userns_L3_id);
	ASSERT_EQ(ret, 0);

	int userns_L2_fd = ioctl(userns_L3_fd, NS_GET_USERNS);
	ASSERT_GE(userns_L2_fd, 0);
	ret = ioctl(userns_L2_fd, NS_GET_ID, &userns_L2_id);
	ASSERT_EQ(ret, 0);

	int userns_L1_fd = ioctl(userns_L2_fd, NS_GET_USERNS);
	ASSERT_GE(userns_L1_fd, 0);
	ret = ioctl(userns_L1_fd, NS_GET_ID, &userns_L1_id);
	ASSERT_EQ(ret, 0);

	close(userns_L1_fd);
	close(userns_L2_fd);
	close(userns_L3_fd);

	TH_LOG("Multi-level hierarchy: net_L3A (id=%llu) -> userns_L3 (id=%llu) -> userns_L2 (id=%llu) -> userns_L1 (id=%llu)",
	       netns_L3A_id, userns_L3_id, userns_L2_id, userns_L1_id);

	/*
	 * Test 1: Verify net_L3A is visible in listns() after resurrection.
	 * The entire ownership chain should be resurrected and visible.
	 */
	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	if (ret < 0) {
		free(handle);
		close(sock_L3A_fd);
		close(netns_L3A_fd);
		if (errno == ENOSYS)
			SKIP(return, "listns() not supported");
		ASSERT_GE(ret, 0);
	}

	bool found_netns_L3A = false;
	bool found_userns_L1 = false;
	bool found_userns_L2 = false;
	bool found_userns_L3 = false;

	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_L3A_id)
			found_netns_L3A = true;
		if (ns_ids[i] == userns_L1_id)
			found_userns_L1 = true;
		if (ns_ids[i] == userns_L2_id)
			found_userns_L2 = true;
		if (ns_ids[i] == userns_L3_id)
			found_userns_L3 = true;
	}

	ASSERT_TRUE(found_netns_L3A);
	ASSERT_TRUE(found_userns_L1);
	ASSERT_TRUE(found_userns_L2);
	ASSERT_TRUE(found_userns_L3);
	TH_LOG("Resurrection verified: all namespaces in hierarchy visible in listns()");

	/*
	 * Test 2: Verify net_L3A can be reopened via file handle.
	 */
	nsfs_fh = (struct nsfs_file_handle *)handle->f_handle;
	nsfs_fh->ns_id = netns_L3A_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_L3A_fd);
		close(netns_L3A_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);
	}

	close(reopened_fd);
	TH_LOG("File handle test passed: net_L3A can be reopened");

	/*
	 * Test 3: Verify that when we close the netns FD (dropping the last
	 * active reference), the entire tree becomes inactive and disappears
	 * from listns(). The cascade goes: net_L3A drops -> userns_L3 drops ->
	 * userns_L2 drops -> userns_L1 drops.
	 */
	close(netns_L3A_fd);

	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	ASSERT_GE(ret, 0);

	found_netns_L3A = false;
	found_userns_L1 = false;
	found_userns_L2 = false;
	found_userns_L3 = false;

	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_L3A_id)
			found_netns_L3A = true;
		if (ns_ids[i] == userns_L1_id)
			found_userns_L1 = true;
		if (ns_ids[i] == userns_L2_id)
			found_userns_L2 = true;
		if (ns_ids[i] == userns_L3_id)
			found_userns_L3 = true;
	}

	ASSERT_FALSE(found_netns_L3A);
	ASSERT_FALSE(found_userns_L1);
	ASSERT_FALSE(found_userns_L2);
	ASSERT_FALSE(found_userns_L3);
	TH_LOG("Cascade test passed: all namespaces disappeared after netns FD closed");

	/*
	 * Test 4: Verify file handle no longer works for inactive namespace.
	 */
	reopened_fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
	if (reopened_fd >= 0) {
		close(reopened_fd);
		free(handle);
		ASSERT_TRUE(false); /* Should have failed */
	}
	TH_LOG("Inactive namespace correctly cannot be reopened via file handle");

	/*
	 * Test 5: Verify that calling SIOCGSKNS again resurrects the tree again.
	 * The socket is still valid, so we can call SIOCGSKNS on it to resurrect
	 * the namespace tree once more.
	 */
	netns_L3A_fd = ioctl(sock_L3A_fd, SIOCGSKNS);
	ASSERT_GE(netns_L3A_fd, 0);

	TH_LOG("Called SIOCGSKNS again to resurrect the namespace tree");

	/* Verify the namespace tree is resurrected and visible in listns() */
	ret = sys_listns(&req, ns_ids, ARRAY_SIZE(ns_ids), 0);
	ASSERT_GE(ret, 0);

	found_netns_L3A = false;
	found_userns_L1 = false;
	found_userns_L2 = false;
	found_userns_L3 = false;

	for (i = 0; i < ret; i++) {
		if (ns_ids[i] == netns_L3A_id)
			found_netns_L3A = true;
		if (ns_ids[i] == userns_L1_id)
			found_userns_L1 = true;
		if (ns_ids[i] == userns_L2_id)
			found_userns_L2 = true;
		if (ns_ids[i] == userns_L3_id)
			found_userns_L3 = true;
	}

	ASSERT_TRUE(found_netns_L3A);
	ASSERT_TRUE(found_userns_L1);
	ASSERT_TRUE(found_userns_L2);
	ASSERT_TRUE(found_userns_L3);
	TH_LOG("Second resurrection verified: all namespaces in hierarchy visible in listns() again");

	/* Verify we can reopen via file handle again */
	reopened_fd = open_by_handle_at(FD_NSFS_ROOT, handle, O_RDONLY);
	if (reopened_fd < 0) {
		free(handle);
		close(sock_L3A_fd);
		close(netns_L3A_fd);
		TH_LOG("open_by_handle_at failed after second resurrection: %s", strerror(errno));
		ASSERT_GE(reopened_fd, 0);
	}

	close(reopened_fd);
	TH_LOG("File handle test passed: net_L3A can be reopened after second resurrection");

	/* Final cleanup */
	close(sock_L3A_fd);
	close(netns_L3A_fd);
	free(handle);
}

TEST_HARNESS_MAIN