/*
 * test_mkfds - make various file descriptors
 *
 * Written by Masatake YAMATO <yamato@redhat.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include "c.h"
#include "xalloc.h"
#include "test_mkfds.h"
#include "exitcodes.h"
#include "pidfd-utils.h"

#include <arpa/inet.h>
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/file.h>
#include <getopt.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/if_tun.h>
#include <linux/netlink.h>
#include <linux/sock_diag.h>
# include <linux/unix_diag.h> /* for UNIX domain sockets */
#include <linux/sockios.h>  /* SIOCGSKNS */
#include <linux/vm_sockets.h>
#include <linux/vm_sockets_diag.h> /* vsock_diag_req/vsock_diag_msg */
#include <mqueue.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <poll.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/eventfd.h>
#include <sys/inotify.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/select.h>
#include <sys/signalfd.h>
#include <sys/socket.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/timerfd.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/user.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#define EXIT_EPERM  18
#define EXIT_ENOPROTOOPT 19
#define EXIT_EPROTONOSUPPORT 20
#define EXIT_EACCES 21
#define EXIT_ENOENT 22
#define EXIT_ENOSYS 23
#define EXIT_EADDRNOTAVAIL 24
#define EXIT_ENODEV 25

#define _U_ __attribute__((__unused__))

static void do_nothing(int signum _U_);

static void __attribute__((__noreturn__)) usage(FILE *out, int status)
{
	fputs("\nUsage:\n", out);
	fprintf(out, " %s [options] FACTORY FD... [PARAM=VAL...]\n", program_invocation_short_name);

	fputs("\nOptions:\n", out);
	fputs(" -a, --is-available <factory>  exit 0 if the factory is available\n", out);
	fputs(" -l, --list                    list available file descriptor factories and exit\n", out);
	fputs(" -I, --parameters <factory>    list parameters the factory takes\n", out);
	fputs(" -O, --output-values <factory> list output values the factory prints\n", out);
	fputs(" -r, --comm <name>             rename self\n", out);
	fputs(" -q, --quiet                   don't print pid(s)\n", out);
	fputs(" -X, --dont-monitor-stdin      don't monitor stdin when pausing\n", out);
	fputs(" -c, --dont-pause              don't pause after making fd(s)\n", out);
	fputs(" -w, --wait-with <multiplexer> use MULTIPLEXER for waiting events\n", out);
	fputs(" -W, --multiplexers            list multiplexers\n", out);

	fputs("\n", out);
	fputs("Examples:\n", out);
	fprintf(out, "Using 3, open /etc/group:\n\n	$ %s ro-regular-file 3 file=/etc/group\n\n",
		program_invocation_short_name);
	fprintf(out, "Using 3 and 4, make a pipe:\n\n	$ %s pipe-no-fork 3 4\n\n",
		program_invocation_short_name);

	exit(status);
}

union value {
	const char *string;
	long integer;
	unsigned long uinteger;
	bool boolean;
};

enum ptype {
	PTYPE_STRING,
	PTYPE_INTEGER,
	PTYPE_UINTEGER,
	PTYPE_BOOLEAN,
};

struct ptype_class {
	const char *name;

	/* Covert to a string representation.
	 * A caller must free the returned value with free(3) after using. */
	char *(*sprint)(const union value *value);

	/* Convert from a string. If ARG is NULL, use DEFV instead.
	 * A caller must free the returned value with the free method
	 * after using. */
	union value (*read)(const char *arg, const union value *defv);

	/* Free the value returned from the read method. */
	void (*free)(union value value);
};

#define ARG_STRING(A) (A.v.string)
#define ARG_INTEGER(A) (A.v.integer)
#define ARG_UINTEGER(A) (A.v.uinteger)
#define ARG_BOOLEAN(A) (A.v.boolean)
struct arg {
	union value v;
	void (*free)(union value value);
};

struct parameter {
	const char *name;
	const enum ptype type;
	const char *desc;
	union value defv;	/* Default value */
};

static char *string_sprint(const union value *value)
{
	return xstrdup(value->string);
}

static union value string_read(const char *arg, const union value *defv)
{
	return (union value){ .string = xstrdup(arg?: defv->string) };
}

static void string_free(union value value)
{
	free((void *)value.string);
}

static char *integer_sprint(const union value *value)
{
	char *str = NULL;
	xasprintf(&str, "%ld", value->integer);
	return str;
}

static union value integer_read(const char *arg, const union value *defv)
{
	char *ep;
	union value r;

	if (!arg)
		return *defv;

	errno = 0;
	r.integer = strtol(arg, &ep, 10);
	if (errno)
		err(EXIT_FAILURE, "fail to make a number from %s", arg);
	else if (*ep != '\0')
		errx(EXIT_FAILURE, "garbage at the end of number: %s", arg);
	return r;
}

static void integer_free(union value value _U_)
{
	/* Do nothing */
}

static char *uinteger_sprint(const union value *value)
{
	char *str = NULL;
	xasprintf(&str, "%lu", value->uinteger);
	return str;
}

static union value uinteger_read(const char *arg, const union value *defv)
{
	char *ep;
	union value r;

	if (!arg)
		return *defv;

	errno = 0;
	r.uinteger = strtoul(arg, &ep, 10);
	if (errno)
		err(EXIT_FAILURE, "fail to make a number from %s", arg);
	else if (*ep != '\0')
		errx(EXIT_FAILURE, "garbage at the end of number: %s", arg);
	return r;
}

static void uinteger_free(union value value _U_)
{
	/* Do nothing */
}

static char *boolean_sprint(const union value *value)
{
	return xstrdup(value->boolean? "true": "false");
}

static union value boolean_read(const char *arg, const union value *defv)
{
	union value r;

	if (!arg)
		return *defv;

	if (strcasecmp(arg, "true") == 0
	    || strcmp(arg, "1") == 0
	    || strcasecmp(arg, "yes") == 0
	    || strcasecmp(arg, "y") == 0)
		r.boolean = true;
	else
		r.boolean = false;
	return r;
}

static void boolean_free(union value value _U_)
{
	/* Do nothing */
}

struct ptype_class ptype_classes [] = {
	[PTYPE_STRING] = {
		.name = "string",
		.sprint = string_sprint,
		.read   = string_read,
		.free   = string_free,
	},
	[PTYPE_INTEGER] = {
		.name = "integer",
		.sprint = integer_sprint,
		.read   = integer_read,
		.free   = integer_free,
	},
	[PTYPE_UINTEGER] = {
		.name = "uinteger",
		.sprint = uinteger_sprint,
		.read   = uinteger_read,
		.free   = uinteger_free,
	},
	[PTYPE_BOOLEAN] = {
		.name = "boolean",
		.sprint = boolean_sprint,
		.read   = boolean_read,
		.free   = boolean_free,
	},
};

static struct arg decode_arg(const char *pname,
			     const struct parameter *parameters,
			     int argc, char **argv)
{
	char *v = NULL;
	size_t len = strlen(pname);
	const struct parameter *p = NULL;
	struct arg arg;

	while (parameters->name) {
		if (strcmp(pname, parameters->name) == 0) {
			p = parameters;
			break;
		}
		parameters++;
	}
	if (p == NULL)
		errx(EXIT_FAILURE, "no such parameter: %s", pname);

	for (int i = 0; i < argc; i++) {
		if (strncmp(pname, argv[i], len) == 0) {
			v = argv[i] + len;
			if (*v == '=') {
				v++;
				break;
			} else if (*v == '\0')
				errx(EXIT_FAILURE,
				     "no value given for \"%s\" parameter",
				     pname);
			else
				v = NULL;
		}
	}
	arg.v = ptype_classes [p->type].read(v, &p->defv);
	arg.free = ptype_classes [p->type].free;
	return arg;
}

static void free_arg(struct arg *arg)
{
	arg->free(arg->v);
}

struct factory {
	const char *name;	/* [-a-zA-Z0-9_]+ */
	const char *desc;
	bool priv;		/* the root privilege is needed to make fd(s) */
#define MAX_N 13
	int  N;			/* the number of fds this factory makes */
	int  EX_N;		/* fds made optionally */
	int  EX_O;		/* the number of extra words printed to stdout. */
	void *(*make)(const struct factory *, struct fdesc[], int, char **);
	void (*free)(const struct factory *, void *);
	void (*report)(const struct factory *, int, void *, FILE *);
	const struct parameter * params;
	const char **o_descs;	/* string array describing values printed
				 * to stdout. Used in -O option.
				 * EX_O elements are expected. */
};

static void close_fdesc(int fd, void *data _U_)
{
	close(fd);
}

volatile ssize_t unused_result_ok;
static void abort_with_child_death_message(int signum _U_)
{
	const char msg[] = "the child process exits unexpectedly";
	unused_result_ok = write(2, msg, sizeof(msg));
	_exit(EXIT_FAILURE);
}

static void reserve_fd(int fd)
{
	(void)close(fd);
	if (dup2(0, fd) < 0)
		errx(EXIT_FAILURE,
		     "faild to reserve fd with dup2(%d, %d)", 0, fd);
}

static void *open_ro_regular_file(const struct factory *factory, struct fdesc fdescs[],
				  int argc, char ** argv)
{
	struct arg file = decode_arg("file", factory->params, argc, argv);
	struct arg offset = decode_arg("offset", factory->params, argc, argv);
	struct arg lease_r = decode_arg("read-lease", factory->params, argc, argv);

	int fd = open(ARG_STRING(file), O_RDONLY);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to open: %s", ARG_STRING(file));
	free_arg(&file);

	if (ARG_INTEGER(offset) != 0) {
		if (lseek(fd, (off_t)ARG_INTEGER(offset), SEEK_CUR) < 0) {
			err(EXIT_FAILURE, "failed to seek 0 -> %ld", ARG_INTEGER(offset));
		}
	}
	free_arg(&offset);

	if (ARG_BOOLEAN(lease_r)) {
		if (fcntl(fd, F_SETLEASE, F_RDLCK) < 0) {
			err(EXIT_FAILURE, "failed to take out a read lease");
		}
	}
	free_arg(&lease_r);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void unlink_and_close_fdesc(int fd, void *data)
{
	char *fname = data;

	unlink(fname);
	close(fd);
}

typedef void (*lockFn)(int fd, const char *fname);

static void lock_fn_none(int fd _U_, const char *fname _U_)
{
	/* Do nothing */
}

static void lock_fn_flock_sh(int fd, const char *fname)
{
	if (flock(fd, LOCK_SH) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_flock_ex(int fd, const char *fname)
{
	if (flock(fd, LOCK_EX) < 0)  {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_posix_r_(int fd, const char *fname)
{
	struct flock r = {
		.l_type = F_RDLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
	};
	if (fcntl(fd, F_SETLK, &r) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_posix__w(int fd, const char *fname)
{
	struct flock w = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
	};
	if (fcntl(fd, F_SETLK, &w) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_posix_rw(int fd, const char *fname)
{
	struct flock r = {
		.l_type = F_RDLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
	};
	struct flock w = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_SET,
		.l_start = 2,
		.l_len = 1,
	};
	if (fcntl(fd, F_SETLK, &r) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock(read)");
	}
	if (fcntl(fd, F_SETLK, &w) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock(write)");
	}
}

#ifdef F_OFD_SETLK
static void lock_fn_ofd_r_(int fd, const char *fname)
{
	struct flock r = {
		.l_type = F_RDLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
		.l_pid = 0,
	};
	if (fcntl(fd, F_OFD_SETLK, &r) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_ofd__w(int fd, const char *fname)
{
	struct flock w = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
		.l_pid = 0,
	};
	if (fcntl(fd, F_OFD_SETLK, &w) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock");
	}
}

static void lock_fn_ofd_rw(int fd, const char *fname)
{
	struct flock r = {
		.l_type = F_RDLCK,
		.l_whence = SEEK_SET,
		.l_start = 0,
		.l_len = 1,
		.l_pid = 0,
	};
	struct flock w = {
		.l_type = F_WRLCK,
		.l_whence = SEEK_SET,
		.l_start = 2,
		.l_len = 1,
		.l_pid = 0,
	};
	if (fcntl(fd, F_OFD_SETLK, &r) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock(read)");
	}
	if (fcntl(fd, F_OFD_SETLK, &w) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to lock(write)");
	}
}
#endif	/* F_OFD_SETLK */

static void lock_fn_lease_w(int fd, const char *fname)
{
	if (fcntl(fd, F_SETLEASE, F_WRLCK) < 0) {
		int e = errno;
		if (fname)
			unlink(fname);
		errno = e;
		err(EXIT_FAILURE, "failed to take out a write lease");
	}
}


static void *make_w_regular_file(const struct factory *factory, struct fdesc fdescs[],
				 int argc, char ** argv)
{
	int fd;

	struct arg file = decode_arg("file", factory->params, argc, argv);
	char *fname = xstrdup(ARG_STRING(file));

	struct arg delete = decode_arg("delete", factory->params, argc, argv);
	bool bDelete = ARG_BOOLEAN(delete);

	struct arg write_bytes = decode_arg("write-bytes", factory->params, argc, argv);
	int iWrite_bytes = ARG_INTEGER(write_bytes);

	struct arg readable = decode_arg("readable", factory->params, argc, argv);
	bool bReadable = ARG_BOOLEAN(readable);

	struct arg lock = decode_arg("lock", factory->params, argc, argv);
	const char *sLock = ARG_STRING(lock);
	lockFn lock_fn;

	struct arg dupfd = decode_arg("dupfd", factory->params, argc, argv);
	int iDupfd = ARG_INTEGER(dupfd);

	void *data = NULL;

	if (iWrite_bytes < 0)
		errx(EXIT_FAILURE, "write-bytes must be a positive number or zero.");

	if (strcmp(sLock, "none") == 0)
		lock_fn = lock_fn_none;
	else if (strcmp(sLock, "flock-sh") == 0)
		lock_fn = lock_fn_flock_sh;
	else if (strcmp(sLock, "flock-ex") == 0)
		lock_fn = lock_fn_flock_ex;
	else if (strcmp(sLock, "posix-r-") == 0) {
		bReadable = true;
		if (iWrite_bytes < 1)
			iWrite_bytes = 1;
		lock_fn = lock_fn_posix_r_;
	} else if (strcmp(sLock, "posix--w") == 0) {
		if (iWrite_bytes < 1)
			iWrite_bytes = 1;
		lock_fn = lock_fn_posix__w;
	} else if (strcmp(sLock, "posix-rw") == 0) {
		bReadable = true;
		if (iWrite_bytes < 3)
			iWrite_bytes = 3;
		lock_fn = lock_fn_posix_rw;
#ifdef F_OFD_SETLK
	} else if (strcmp(sLock, "ofd-r-") == 0) {
		bReadable = true;
		if (iWrite_bytes < 1)
			iWrite_bytes = 1;
		lock_fn = lock_fn_ofd_r_;
	} else if (strcmp(sLock, "ofd--w") == 0) {
		if (iWrite_bytes < 1)
			iWrite_bytes = 1;
		lock_fn = lock_fn_ofd__w;
	} else if (strcmp(sLock, "ofd-rw") == 0) {
		bReadable = true;
		if (iWrite_bytes < 3)
			iWrite_bytes = 3;
		lock_fn = lock_fn_ofd_rw;
#else
	} else if (strcmp(sLock, "ofd-r-") == 0
	      || strcmp(sLock, "ofd--w") == 0
	      || strcmp(sLock, "ofd-rw") == 0) {
		errx(EXIT_ENOSYS, "no availability for ofd lock");
#endif	/* F_OFD_SETLK */
	} else if (strcmp(sLock, "lease-w") == 0)
		lock_fn = lock_fn_lease_w;
	else
		errx(EXIT_FAILURE, "unexpected value for lock parameter: %s", sLock);

	free_arg(&dupfd);
	free_arg(&lock);
	free_arg(&readable);
	free_arg(&write_bytes);
	free_arg(&delete);
	free_arg(&file);

	fd = open(fname, O_CREAT|O_EXCL|(bReadable? O_RDWR: O_WRONLY), S_IWUSR);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to make: %s", fname);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			int e = errno;
			unlink(fname);
			errno = e;
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
		fd = fdescs[0].fd;
	}

	if (bDelete) {
		if (unlink(fname) < 0) {
			err(EXIT_FAILURE, "failed to unlink %s", fname);
		}
		free(fname);
		fname = NULL;
	}

	for (int i = 0; i < iWrite_bytes; i++) {
		if (write(fd, "z", 1) != 1) {
			int e = errno;
			if (fname)
				unlink(fname);
			errno = e;
			err(EXIT_FAILURE, "failed to write");
		}
	}

	if (iDupfd >= 0) {
		if (dup2(fd, iDupfd) < 0) {
			int e = errno;
			if (fname)
				unlink(fname);
			errno = e;
			err(EXIT_FAILURE, "failed in dup2");
		}
		data = xmemdup(&iDupfd, sizeof(iDupfd));
	}

	lock_fn(fd, fname);

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = bDelete? close_fdesc: unlink_and_close_fdesc,
		.data  = fname,
	};

	return data;
}

static void free_after_closing_duplicated_fd(const struct factory * factory _U_, void *data)
{
	if (data) {
		int *fdp = data;
		close(*fdp);
		free(data);
	}
}

static void *make_pipe(const struct factory *factory, struct fdesc fdescs[],
		       int argc, char ** argv)
{
	int pd[2];
	int nonblock_flags[2] = {0, 0};
	struct arg nonblock = decode_arg("nonblock", factory->params, argc, argv);
	if (strlen(ARG_STRING(nonblock)) != 2) {
		errx(EXIT_FAILURE, "string value for %s has unexpected length: %s",
		     "nonblock", ARG_STRING(nonblock));
	}

	/* Make extra pipe descriptors for making pipe objects connected
	 * with fds more than 2.
	 * See https://github.com/util-linux/util-linux/pull/1622
	 * about the background of the requirement. */
	struct arg rdup = decode_arg("rdup", factory->params, argc, argv);
	struct arg wdup = decode_arg("wdup", factory->params, argc, argv);
	int xpd[2];
	xpd [0] = ARG_INTEGER(rdup);
	xpd [1] = ARG_INTEGER(wdup);

	/* Reserve the fd */
	for (int i = 0; i < 2; i++) {
		if (xpd[i] < 0)
			continue;
		reserve_fd(xpd[i]);
	}

	for (int i = 0; i < 2; i++) {
		if (ARG_STRING(nonblock)[i] == '-')
			continue;
		if ((i == 0 && ARG_STRING(nonblock)[i] == 'r')
		    || (i == 1 && ARG_STRING(nonblock)[i] == 'w'))
			nonblock_flags[i] = 1;
		else
			errx(EXIT_FAILURE, "unexpected value %c for the %s fd of %s",
			     ARG_STRING(nonblock)[i],
			     (i == 0)? "read": "write",
			     "nonblock");
	}
	free_arg(&nonblock);

	if (pipe(pd) < 0)
		err(EXIT_FAILURE, "failed to make pipe");

	for (int i = 0; i < 2; i++) {
		if (nonblock_flags[i]) {
			int flags = fcntl(pd[i], F_GETFL);
			if (fcntl(pd[i], F_SETFL, flags|O_NONBLOCK) < 0) {
				errx(EXIT_FAILURE, "failed to set NONBLOCK flag to the %s fd",
				     (i == 0)? "read": "write");
			}
		}
	}

	for (int i = 0; i < 2; i++) {
		if (pd[i] != fdescs[i].fd) {
			if (dup2(pd[i], fdescs[i].fd) < 0) {
				err(EXIT_FAILURE, "failed to dup %d -> %d",
				    pd[i], fdescs[i].fd);
			}
			close(pd[i]);
		}
		fdescs[i] = (struct fdesc){
			.fd    = fdescs[i].fd,
			.close = close_fdesc,
			.data  = NULL
		};
	}

	/* Make extra pipe descriptors. */
	for (int i = 0; i < 2; i++) {
		if (xpd[i] >= 0) {
			if (dup2(fdescs[i].fd, xpd[i]) < 0) {
				err(EXIT_FAILURE, "failed to dup %d -> %d",
				    fdescs[i].fd, xpd[i]);
			}
			fdescs[i + 2] = (struct fdesc){
				.fd = xpd[i],
				.close = close_fdesc,
				.data = NULL
			};
		}
	}

	return NULL;
}

static void close_dir(int fd, void *data)
{
	DIR *dp = data;
	if (dp)
		closedir(dp);
	else
		close_fdesc(fd, NULL);
}

static void *open_directory(const struct factory *factory, struct fdesc fdescs[],
			    int argc, char ** argv)
{
	struct arg dir = decode_arg("dir", factory->params, argc, argv);
	struct arg dentries = decode_arg("dentries", factory->params, argc, argv);
	DIR *dp = NULL;

	int fd = open(ARG_STRING(dir), O_RDONLY|O_DIRECTORY);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to open: %s", ARG_STRING(dir));
	free_arg(&dir);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	if (ARG_INTEGER(dentries) > 0) {
		dp = fdopendir(fdescs[0].fd);
		if (dp == NULL) {
			err(EXIT_FAILURE, "failed to make DIR* from fd: %s", ARG_STRING(dir));
		}
		for (int i = 0; i < ARG_INTEGER(dentries); i++) {
			struct dirent *d = readdir(dp);
			if (!d) {
				err(EXIT_FAILURE, "failed in readdir(3)");
			}
		}
	}
	free_arg(&dentries);

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_dir,
		.data  = dp
	};

	return NULL;
}

static void *open_rw_chrdev(const struct factory *factory, struct fdesc fdescs[],
			    int argc, char ** argv)
{
	struct arg chrdev = decode_arg("chrdev", factory->params, argc, argv);
	int fd = open(ARG_STRING(chrdev), O_RDWR);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to open: %s", ARG_STRING(chrdev));
	free_arg(&chrdev);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_socketpair(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv)
{
	int sd[2];
	struct arg socktype = decode_arg("socktype", factory->params, argc, argv);
	int isocktype;
	struct arg halfclose = decode_arg("halfclose", factory->params, argc, argv);
	bool bhalfclose;

	bhalfclose = ARG_BOOLEAN(halfclose);
	free_arg(&halfclose);

	if (strcmp(ARG_STRING(socktype), "STREAM") == 0)
		isocktype = SOCK_STREAM;
	else if (strcmp(ARG_STRING(socktype), "DGRAM") == 0)
		isocktype = SOCK_DGRAM;
	else if (strcmp(ARG_STRING(socktype), "SEQPACKET") == 0)
		isocktype = SOCK_SEQPACKET;
	else
		errx(EXIT_FAILURE,
		     "unknown socket type for socketpair(AF_UNIX,...): %s",
		     ARG_STRING(socktype));
	free_arg(&socktype);

	if (socketpair(AF_UNIX, isocktype, 0, sd) < 0)
		err(EXIT_FAILURE, "failed to make socket pair");

	if (bhalfclose) {
		if (shutdown(sd[0], SHUT_RD) < 0)
			err(EXIT_FAILURE,
			    "failed to shutdown the read end of the 1st socket");
		if (shutdown(sd[1], SHUT_WR) < 0)
			err(EXIT_FAILURE,
			    "failed to shutdown the write end of the 2nd socket");
	}

	for (int i = 0; i < 2; i++) {
		if (sd[i] != fdescs[i].fd) {
			if (dup2(sd[i], fdescs[i].fd) < 0) {
				err(EXIT_FAILURE, "failed to dup %d -> %d",
				    sd[i], fdescs[i].fd);
			}
			close(sd[i]);
		}
		fdescs[i] = (struct fdesc){
			.fd    = fdescs[i].fd,
			.close = close_fdesc,
			.data  = NULL
		};
	}

	return NULL;
}

static void *open_with_opath(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv)
{
	struct arg path = decode_arg("path", factory->params, argc, argv);
	int fd = open(ARG_STRING(path), O_PATH|O_NOFOLLOW);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to open with O_PATH: %s", ARG_STRING(path));
	free_arg(&path);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *open_ro_blkdev(const struct factory *factory, struct fdesc fdescs[],
			    int argc, char ** argv)
{
	struct arg blkdev = decode_arg("blkdev", factory->params, argc, argv);
	int fd = open(ARG_STRING(blkdev), O_RDONLY);
	if (fd < 0)
		err(EXIT_FAILURE, "failed to open: %s", ARG_STRING(blkdev));
	free_arg(&blkdev);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	return NULL;
}

static int make_packet_socket(int socktype, const char *interface)
{
	int sd;
	struct sockaddr_ll addr;

	sd = socket(AF_PACKET, socktype, htons(ETH_P_ALL));
	if (sd < 0)
		err(EXIT_FAILURE, "failed to make a socket with AF_PACKET");

	if (interface == NULL)
		return sd;	/* Just making a socket */

	memset(&addr, 0, sizeof(addr));
	addr.sll_family = AF_PACKET;
	addr.sll_ifindex = if_nametoindex(interface);
	if (addr.sll_ifindex == 0) {
		err(EXIT_FAILURE,
		    "failed to get the interface index for %s", interface);
	}
	if (bind(sd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
		err(EXIT_FAILURE,
		    "failed to get the interface index for %s", interface);
	}

	return sd;
}

struct munmap_data {
	void *ptr;
	size_t len;
};

static void close_fdesc_after_munmap(int fd, void *data)
{
	struct munmap_data *munmap_data = data;
	munmap(munmap_data->ptr, munmap_data->len);
	free(data);
	close(fd);
}

static void *make_mmapped_packet_socket(const struct factory *factory, struct fdesc fdescs[],
					int argc, char ** argv)
{
	int sd;
	struct arg socktype = decode_arg("socktype", factory->params, argc, argv);
	struct arg interface = decode_arg("interface", factory->params, argc, argv);

	int isocktype;
	const char *sinterface;
	struct tpacket_req req;
	struct munmap_data *munmap_data;

	if (strcmp(ARG_STRING(socktype), "DGRAM") == 0)
		isocktype = SOCK_DGRAM;
	else if (strcmp(ARG_STRING(socktype), "RAW") == 0)
		isocktype = SOCK_RAW;
	else
		errx(EXIT_FAILURE,
		     "unknown socket type for socket(AF_PACKET,...): %s",
		     ARG_STRING(socktype));
	free_arg(&socktype);

	sinterface = ARG_STRING(interface);
	sd = make_packet_socket(isocktype, sinterface);
	free_arg(&interface);

	/* Specify the spec of ring buffers.
	 *
	 * ref.
	 * - linux/Documentation/networking/packet_mmap.rst
	 * - https://sites.google.com/site/packetmmap/home
	 */
	req.tp_block_size = getpagesize();
	req.tp_frame_size = getpagesize();
	req.tp_block_nr = 1;
	req.tp_frame_nr = 1;
	if (setsockopt(sd, SOL_PACKET, PACKET_TX_RING, (char *)&req, sizeof(req)) < 0) {
		err((errno == ENOPROTOOPT? EXIT_ENOPROTOOPT: EXIT_FAILURE),
		    "failed to specify a buffer spec to a packet socket");
	}

	munmap_data = xmalloc(sizeof(*munmap_data));
	munmap_data->len = (size_t) req.tp_block_size * req.tp_block_nr;
	munmap_data->ptr = mmap(NULL, munmap_data->len, PROT_WRITE, MAP_SHARED, sd, 0);
	if (munmap_data->ptr == MAP_FAILED) {
		err(EXIT_FAILURE, "failed to do mmap a packet socket");
	}

	if (sd != fdescs[0].fd) {
		if (dup2(sd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", sd, fdescs[0].fd);
		}
		close(sd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc_after_munmap,
		.data  = munmap_data,
	};

	return NULL;
}

static void *make_pidfd(const struct factory *factory, struct fdesc fdescs[],
			int argc, char ** argv)
{
	struct arg target_pid = decode_arg("target-pid", factory->params, argc, argv);
	pid_t pid = ARG_INTEGER(target_pid);

	int fd = pidfd_open(pid, 0);
	if (fd < 0)
		err_nosys(EXIT_FAILURE, "failed in pidfd_open(%d)", (int)pid);
	free_arg(&target_pid);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_inotify_fd(const struct factory *factory _U_, struct fdesc fdescs[],
			     int argc _U_, char ** argv _U_)
{
	struct arg dir = decode_arg("dir", factory->params, argc, argv);
	const char *sdir = ARG_STRING(dir);
	struct arg file = decode_arg("file", factory->params, argc, argv);
	const char *sfile = ARG_STRING(file);

	int fd = inotify_init();
	if (fd < 0)
		err(EXIT_FAILURE, "failed in inotify_init()");

	if (inotify_add_watch(fd, sdir, IN_DELETE) < 0) {
		err(EXIT_FAILURE, "failed in inotify_add_watch(\"%s\")", sdir);
	}
	free_arg(&dir);

	if (inotify_add_watch(fd, sfile, IN_DELETE) < 0) {
		err(EXIT_FAILURE, "failed in inotify_add_watch(\"%s\")", sfile);
	}
	free_arg(&file);

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void close_unix_socket(int fd, void *data)
{
	char *path = data;
	close(fd);
	if (path) {
		unlink(path);
		free(path);
	}
}

static void *make_unix_stream_core(const struct factory *factory, struct fdesc fdescs[],
				   int argc, char ** argv, int type, const char *typestr)
{
	struct arg path = decode_arg("path", factory->params, argc, argv);
	const char *spath = ARG_STRING(path);

	struct arg backlog = decode_arg("backlog", factory->params, argc, argv);
	int ibacklog = ARG_INTEGER(path);

	struct arg abstract = decode_arg("abstract", factory->params, argc, argv);
	bool babstract = ARG_BOOLEAN(abstract);

	struct arg server_shutdown = decode_arg("server-shutdown", factory->params, argc, argv);
	int iserver_shutdown = ARG_INTEGER(server_shutdown);
	struct arg client_shutdown = decode_arg("client-shutdown", factory->params, argc, argv);
	int iclient_shutdown = ARG_INTEGER(client_shutdown);

	int ssd, csd, asd;	/* server, client, and accepted socket descriptors */
	struct sockaddr_un un;
	size_t un_len = sizeof(un);

	memset(&un, 0, sizeof(un));
	un.sun_family = AF_UNIX;
	if (babstract) {
		strncpy(un.sun_path + 1, spath, sizeof(un.sun_path) - 1 - 1);
		size_t pathlen = strlen(spath);
		if (sizeof(un.sun_path) - 1 > pathlen)
			un_len = sizeof(un) - sizeof(un.sun_path) + 1 + pathlen;
	} else
		strncpy(un.sun_path,     spath, sizeof(un.sun_path) - 1    );

	free_arg(&client_shutdown);
	free_arg(&server_shutdown);
	free_arg(&abstract);
	free_arg(&backlog);
	free_arg(&path);

	if (iserver_shutdown < 0 || iserver_shutdown > 3)
		errx(EXIT_FAILURE, "the server shudown specification in unexpected range");
	if (iclient_shutdown < 0 || iclient_shutdown > 3)
		errx(EXIT_FAILURE, "the client shudown specification in unexpected range");

	ssd = socket(AF_UNIX, type, 0);
	if (ssd < 0)
		err(EXIT_FAILURE,
		    "failed to make a socket with AF_UNIX + SOCK_%s (server side)", typestr);
	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_unix_socket,
		.data  = NULL,
	};

	if (!babstract)
		unlink(un.sun_path);
	if (bind(ssd, (const struct sockaddr *)&un, un_len) < 0) {
		err(EXIT_FAILURE, "failed to bind a socket for listening");
	}

	if (!babstract)
		fdescs[0].data = xstrdup(un.sun_path);
	if (listen(ssd, ibacklog) < 0) {
		int e = errno;
		close_unix_socket(ssd, fdescs[0].data);
		errno = e;
		err(EXIT_FAILURE, "failed to listen a socket");
	}

	csd = socket(AF_UNIX, type, 0);
	if (csd < 0)
		err(EXIT_FAILURE,
		    "failed to make a socket with AF_UNIX + SOCK_%s (client side)", typestr);
	if (csd != fdescs[1].fd) {
		if (dup2(csd, fdescs[1].fd) < 0) {
			int e = errno;
			close_unix_socket(ssd, fdescs[0].data);
			errno = e;
			err(EXIT_FAILURE, "failed to dup %d -> %d", csd, fdescs[1].fd);
		}
		close(csd);
		csd = fdescs[1].fd;
	}

	fdescs[1] = (struct fdesc){
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	if (connect(csd, (const struct sockaddr *)&un, un_len) < 0) {
		int e = errno;
		close_unix_socket(ssd, fdescs[0].data);
		errno = e;
		err(EXIT_FAILURE, "failed to connect a socket to the listening socket");
	}

	if (!babstract)
		unlink(un.sun_path);

	asd = accept(ssd, NULL, NULL);
	if (asd < 0) {
		int e = errno;
		close_unix_socket(ssd, fdescs[0].data);
		errno = e;
		err(EXIT_FAILURE, "failed to accept a socket from the listening socket");
	}
	if (asd != fdescs[2].fd) {
		if (dup2(asd, fdescs[2].fd) < 0) {
			int e = errno;
			close_unix_socket(ssd, fdescs[0].data);
			errno = e;
			err(EXIT_FAILURE, "failed to dup %d -> %d", asd, fdescs[2].fd);
		}
		close(asd);
		asd = fdescs[2].fd;
	}

	if (iserver_shutdown & (1 << 0))
		shutdown(asd, SHUT_RD);
	if (iserver_shutdown & (1 << 1))
		shutdown(asd, SHUT_WR);
	if (iclient_shutdown & (1 << 0))
		shutdown(csd, SHUT_RD);
	if (iclient_shutdown & (1 << 1))
		shutdown(csd, SHUT_WR);

	return NULL;
}

static void *make_unix_stream(const struct factory *factory, struct fdesc fdescs[],
			      int argc, char ** argv)
{
	struct arg type = decode_arg("type", factory->params, argc, argv);
	const char *stype = ARG_STRING(type);

	int typesym;
	const char *typestr;

	if (strcmp(stype, "stream") == 0) {
		typesym = SOCK_STREAM;
		typestr = "STREAM";
	} else if (strcmp(stype, "seqpacket") == 0) {
		typesym = SOCK_SEQPACKET;
		typestr = "SEQPACKET";
	} else
		errx(EXIT_FAILURE, "unknown unix socket type: %s", stype);

	free_arg(&type);

	return make_unix_stream_core(factory, fdescs, argc, argv, typesym, typestr);
}

static void *make_unix_dgram(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv)
{
	struct arg path = decode_arg("path", factory->params, argc, argv);
	const char *spath = ARG_STRING(path);

	struct arg abstract = decode_arg("abstract", factory->params, argc, argv);
	bool babstract = ARG_BOOLEAN(abstract);

	int ssd, csd;	/* server and client socket descriptors */

	struct sockaddr_un un;
	size_t un_len = sizeof(un);

	memset(&un, 0, sizeof(un));
	un.sun_family = AF_UNIX;
	if (babstract) {
		strncpy(un.sun_path + 1, spath, sizeof(un.sun_path) - 1 - 1);
		size_t pathlen = strlen(spath);
		if (sizeof(un.sun_path) - 1 > pathlen)
			un_len = sizeof(un) - sizeof(un.sun_path) + 1 + pathlen;
	} else
		strncpy(un.sun_path,     spath, sizeof(un.sun_path) - 1    );

	free_arg(&abstract);
	free_arg(&path);

	ssd = socket(AF_UNIX, SOCK_DGRAM, 0);
	if (ssd < 0)
		err(EXIT_FAILURE,
		    "failed to make a socket with AF_UNIX + SOCK_DGRAM (server side)");
	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_unix_socket,
		.data  = NULL,
	};

	if (!babstract)
		unlink(un.sun_path);
	if (bind(ssd, (const struct sockaddr *)&un, un_len) < 0) {
		err(EXIT_FAILURE, "failed to bind a socket for server");
	}

	if (!babstract)
		fdescs[0].data = xstrdup(un.sun_path);
	csd = socket(AF_UNIX, SOCK_DGRAM, 0);
	if (csd < 0)
		err(EXIT_FAILURE,
		    "failed to make a socket with AF_UNIX + SOCK_DGRAM (client side)");
	if (csd != fdescs[1].fd) {
		if (dup2(csd, fdescs[1].fd) < 0) {
			int e = errno;
			close_unix_socket(ssd, fdescs[0].data);
			errno = e;
			err(EXIT_FAILURE, "failed to dup %d -> %d", csd, fdescs[1].fd);
		}
		close(csd);
		csd = fdescs[1].fd;
	}

	fdescs[1] = (struct fdesc){
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	if (connect(csd, (const struct sockaddr *)&un, un_len) < 0) {
		int e = errno;
		close_unix_socket(ssd, fdescs[0].data);
		errno = e;
		err(EXIT_FAILURE, "failed to connect a socket to the server socket");
	}

	if (!babstract)
		unlink(un.sun_path);

	return NULL;
}

static void *make_unix_in_new_netns(const struct factory *factory, struct fdesc fdescs[],
				    int argc, char ** argv)
{
	struct arg type = decode_arg("type", factory->params, argc, argv);
	const char *stype = ARG_STRING(type);

	struct arg path = decode_arg("path", factory->params, argc, argv);
	const char *spath = ARG_STRING(path);

	struct arg abstract = decode_arg("abstract", factory->params, argc, argv);
	bool babstract = ARG_BOOLEAN(abstract);

	int typesym;
	const char *typestr;

	struct sockaddr_un un;
	size_t un_len = sizeof(un);

	int self_netns, tmp_netns, sd;

	if (strcmp(stype, "stream") == 0) {
		typesym = SOCK_STREAM;
		typestr = "STREAM";
	} else if (strcmp(stype, "seqpacket") == 0) {
		typesym = SOCK_SEQPACKET;
		typestr = "SEQPACKET";
	} else if (strcmp(stype, "dgram") == 0) {
		typesym = SOCK_DGRAM;
		typestr = "DGRAM";
	} else {
		errx(EXIT_FAILURE, "unknown unix socket type: %s", stype);
	}

	memset(&un, 0, sizeof(un));
	un.sun_family = AF_UNIX;
	if (babstract) {
		strncpy(un.sun_path + 1, spath, sizeof(un.sun_path) - 1 - 1);
		size_t pathlen = strlen(spath);
		if (sizeof(un.sun_path) - 1 > pathlen)
			un_len = sizeof(un) - sizeof(un.sun_path) + 1 + pathlen;
	} else
		strncpy(un.sun_path,     spath, sizeof(un.sun_path) - 1    );

	free_arg(&abstract);
	free_arg(&path);
	free_arg(&type);

	self_netns = open("/proc/self/ns/net", O_RDONLY);
	if (self_netns < 0)
		err(EXIT_FAILURE, "failed to open /proc/self/ns/net");
	if (self_netns != fdescs[0].fd) {
		if (dup2(self_netns, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", self_netns, fdescs[0].fd);
		}
		close(self_netns);
		self_netns = fdescs[0].fd;
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	if (unshare(CLONE_NEWNET) < 0) {
		err((errno == EPERM? EXIT_EPERM: EXIT_FAILURE),
		    "failed in unshare");
	}

	tmp_netns = open("/proc/self/ns/net", O_RDONLY);
	if (tmp_netns < 0) {
		err(EXIT_FAILURE, "failed to open /proc/self/ns/net for the new netns");
	}
	if (tmp_netns != fdescs[1].fd) {
		if (dup2(tmp_netns, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", tmp_netns, fdescs[1].fd);
		}
		close(tmp_netns);
		tmp_netns = fdescs[1].fd;
	}

	fdescs[1] = (struct fdesc){
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	sd = socket(AF_UNIX, typesym, 0);
	if (sd < 0) {
		err(EXIT_FAILURE,
		    "failed to make a socket with AF_UNIX + SOCK_%s",
		    typestr);
	}

	if (sd != fdescs[2].fd) {
		if (dup2(sd, fdescs[2].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", sd, fdescs[2].fd);
		}
		close(sd);
		sd = fdescs[2].fd;
	}

	fdescs[2] = (struct fdesc){
		.fd    = fdescs[2].fd,
		.close = close_unix_socket,
		.data  = NULL,
	};

	if (!babstract)
		unlink(un.sun_path);
	if (bind(sd, (const struct sockaddr *)&un, un_len) < 0) {
		err(EXIT_FAILURE, "failed to bind a socket");
	}

	if (!babstract)
		fdescs[2].data = xstrdup(un.sun_path);

	if (typesym != SOCK_DGRAM) {
		if (listen(sd, 1) < 0) {
			int e = errno;
			close_unix_socket(sd, fdescs[2].data);
			errno = e;
			err(EXIT_FAILURE, "failed to listen a socket");
		}
	}

	if (setns(self_netns, CLONE_NEWNET) < 0) {
		int e = errno;
		close_unix_socket(sd, fdescs[2].data);
		errno = e;
		err(EXIT_FAILURE, "failed to switch back to the original net namespace");
	}

	return NULL;
}

static void *make_tcp_common(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv,
			     int family,
			     void (*init_addr)(struct sockaddr *, unsigned short),
			     size_t addr_size,
			     struct sockaddr * sin, struct sockaddr * cin)
{
	struct arg server_port = decode_arg("server-port", factory->params, argc, argv);
	unsigned short iserver_port = (unsigned short)ARG_INTEGER(server_port);
	struct arg client_port = decode_arg("client-port", factory->params, argc, argv);
	unsigned short iclient_port = (unsigned short)ARG_INTEGER(client_port);

	int ssd, csd, asd;

	const int y = 1;

	free_arg(&server_port);
	free_arg(&client_port);

	ssd = socket(family, SOCK_STREAM, 0);
	if (ssd < 0)
		err(EXIT_FAILURE,
		    "failed to make a tcp socket for listening");

	if (setsockopt(ssd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	init_addr(sin, iserver_port);
	if (bind(ssd, sin, addr_size) < 0) {
		err(EXIT_FAILURE, "failed to bind a listening socket");
	}

	if (listen(ssd, 1) < 0) {
		err(EXIT_FAILURE, "failed to listen a socket");
	}

	csd = socket(family, SOCK_STREAM, 0);
	if (csd < 0) {
		err(EXIT_FAILURE,
		    "failed to make a tcp client socket");
	}

	if (setsockopt(csd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (csd != fdescs[1].fd) {
		if (dup2(csd, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", csd, fdescs[1].fd);
		}
		close(csd);
		csd = fdescs[1].fd;
	}

	init_addr(cin, iclient_port);
	if (bind(csd, cin, addr_size) < 0) {
		err(EXIT_FAILURE, "failed to bind a client socket");
	}

	if (connect(csd, sin, addr_size) < 0) {
		err(EXIT_FAILURE, "failed to connect a client socket to the server socket");
	}

	asd = accept(ssd, NULL, NULL);
	if (asd < 0) {
		err(EXIT_FAILURE, "failed to accept a socket from the listening socket");
	}
	if (asd != fdescs[2].fd) {
		if (dup2(asd, fdescs[2].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", asd, fdescs[2].fd);
		}
		close(asd);
		asd = fdescs[2].fd;
	}

	fdescs[0] = (struct fdesc) {
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};
	fdescs[1] = (struct fdesc) {
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};
	fdescs[2] = (struct fdesc) {
		.fd    = fdescs[2].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	return NULL;
}

static void tcp_init_addr(struct sockaddr *addr, unsigned short port)
{
	struct sockaddr_in *in = (struct sockaddr_in *)addr;
	memset(in, 0, sizeof(*in));
	in->sin_family = AF_INET;
	in->sin_port = htons(port);
	in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
}

static void *make_tcp(const struct factory *factory, struct fdesc fdescs[],
				    int argc, char ** argv)
{
	struct sockaddr_in sin, cin;
	return make_tcp_common(factory, fdescs, argc, argv,
			       AF_INET,
			       tcp_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin, (struct sockaddr *)&cin);
}

static void *make_udp_common(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv,
			     int family,
			     void (*init_addr)(struct sockaddr *, unsigned short),
			     size_t addr_size,
			     struct sockaddr * sin, struct sockaddr * cin)
{
	struct arg lite = decode_arg("lite", factory->params, argc, argv);
	bool blite = ARG_BOOLEAN(lite);

	struct arg server_port = decode_arg("server-port", factory->params, argc, argv);
	unsigned short iserver_port = (unsigned short)ARG_INTEGER(server_port);
	struct arg client_port = decode_arg("client-port", factory->params, argc, argv);
	unsigned short iclient_port = (unsigned short)ARG_INTEGER(client_port);

	struct arg server_do_bind = decode_arg("server-do-bind", factory->params, argc, argv);
	bool bserver_do_bind = ARG_BOOLEAN(server_do_bind);
	struct arg client_do_bind = decode_arg("client-do-bind", factory->params, argc, argv);
	bool bclient_do_bind = ARG_BOOLEAN(client_do_bind);
	struct arg client_do_connect = decode_arg("client-do-connect", factory->params, argc, argv);
	bool bclient_do_connect = ARG_BOOLEAN(client_do_connect);

	int ssd, csd;

	const int y = 1;

	free_arg(&client_do_connect);
	free_arg(&client_do_bind);
	free_arg(&server_do_bind);
	free_arg(&server_port);
	free_arg(&client_port);
	free_arg(&lite);

	ssd = socket(family, SOCK_DGRAM, blite? IPPROTO_UDPLITE: 0);
	if (ssd < 0)
		err(EXIT_FAILURE,
		    "failed to make a udp socket for server");

	if (setsockopt(ssd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	init_addr(sin, iserver_port);
	if (bserver_do_bind) {
		if (bind(ssd, sin, addr_size) < 0) {
			err(EXIT_FAILURE, "failed to bind a server socket");
		}
	}

	csd = socket(family, SOCK_DGRAM, blite? IPPROTO_UDPLITE: 0);
	if (csd < 0) {
		err(EXIT_FAILURE,
		    "failed to make a udp client socket");
	}

	if (setsockopt(csd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (csd != fdescs[1].fd) {
		if (dup2(csd, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", csd, fdescs[1].fd);
		}
		close(csd);
		csd = fdescs[1].fd;
	}

	if (bclient_do_bind) {
		init_addr(cin, iclient_port);
		if (bind(csd, cin, addr_size) < 0) {
			err(EXIT_FAILURE, "failed to bind a client socket");
		}
	}

	if (bclient_do_connect) {
		if (connect(csd, sin, addr_size) < 0) {
			err(EXIT_FAILURE, "failed to connect a client socket to the server socket");
		}
	}

	fdescs[0] = (struct fdesc) {
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};
	fdescs[1] = (struct fdesc) {
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	return NULL;
}

static void *make_udp(const struct factory *factory, struct fdesc fdescs[],
				    int argc, char ** argv)
{
	struct sockaddr_in sin, cin;
	return make_udp_common(factory, fdescs, argc, argv,
			       AF_INET,
			       tcp_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin, (struct sockaddr *)&cin);
}

static void *make_raw_common(const struct factory *factory, struct fdesc fdescs[],
			     int argc, char ** argv,
			     int family,
			     void (*init_addr)(struct sockaddr *, bool),
			     size_t addr_size,
			     struct sockaddr * sin)
{
	struct arg protocol = decode_arg("protocol", factory->params, argc, argv);
	int iprotocol = ARG_INTEGER(protocol);
	int ssd;

	free_arg(&protocol);

	ssd = socket(family, SOCK_RAW, iprotocol);
	if (ssd < 0)
		err(EXIT_FAILURE,
		    "failed to make a udp socket for server");

	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	init_addr(sin, false);
	if (bind(ssd, sin, addr_size) < 0) {
		err(EXIT_FAILURE, "failed in bind(2)");
	}

	init_addr(sin, true);
	if (connect(ssd, sin, addr_size) < 0) {
		err(EXIT_FAILURE, "failed in connect(2)");
	}

	fdescs[0] = (struct fdesc) {
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	return NULL;
}

static void raw_init_addr(struct sockaddr * addr, bool remote_addr)
{
	struct sockaddr_in *in = (struct sockaddr_in *)addr;
	memset(in, 0, sizeof(*in));
	in->sin_family = AF_INET;
	in->sin_addr.s_addr = htonl(INADDR_LOOPBACK + (remote_addr? 1: 0));
}

static void *make_raw(const struct factory *factory, struct fdesc fdescs[],
				    int argc, char ** argv)
{
	struct sockaddr_in sin;
	return make_raw_common(factory, fdescs, argc, argv,
			       AF_INET,
			       raw_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin);
}

static void *make_ping_common(const struct factory *factory, struct fdesc fdescs[],
			      int argc, char ** argv,
			      int family, int protocol,
			      void (*init_addr)(struct sockaddr *, unsigned short),
			      size_t addr_size,
			      struct sockaddr *sin)
{
	struct arg connect_ = decode_arg("connect", factory->params, argc, argv);
	bool bconnect = ARG_BOOLEAN(connect_);

	struct arg bind_ = decode_arg("bind", factory->params, argc, argv);
	bool bbind = ARG_BOOLEAN(bind_);

	struct arg id = decode_arg("id", factory->params, argc, argv);
	unsigned short iid = (unsigned short)ARG_INTEGER(id);

	int sd;

	free_arg(&id);
	free_arg(&bind_);
	free_arg(&connect_);

	sd = socket(family, SOCK_DGRAM, protocol);
	if (sd < 0)
		err((errno == EACCES? EXIT_EACCES: EXIT_FAILURE),
		    "failed to make an icmp socket");

	if (sd != fdescs[0].fd) {
		if (dup2(sd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", sd, fdescs[0].fd);
		}
		close(sd);
		sd = fdescs[0].fd;
	}

	if (bbind) {
		init_addr(sin, iid);
		if (bind(sd, sin, addr_size) < 0) {
			err((errno == EACCES? EXIT_EACCES: EXIT_FAILURE),
			    "failed in bind(2)");
		}
	}

	if (bconnect) {
		init_addr(sin, 0);
		if (connect(sd, sin, addr_size) < 0) {
			err(EXIT_FAILURE, "failed in connect(2)");
		}
	}

	fdescs[0] = (struct fdesc) {
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	return NULL;
}

static void ping_init_addr(struct sockaddr *addr, unsigned short id)
{
	struct sockaddr_in *in = (struct sockaddr_in *)addr;
	memset(in, 0, sizeof(*in));
	in->sin_family = AF_INET;
	in->sin_port = htons(id);
	in->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
}

static void *make_ping(const struct factory *factory, struct fdesc fdescs[],
		       int argc, char ** argv)
{
	struct sockaddr_in in;
	return make_ping_common(factory, fdescs, argc, argv,
				AF_INET, IPPROTO_ICMP,
				ping_init_addr,
				sizeof(in),
				(struct sockaddr *)&in);
}

static void tcp6_init_addr(struct sockaddr *addr, unsigned short port)
{
	struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)addr;
	memset(in6, 0, sizeof(*in6));
	in6->sin6_family = AF_INET6;
	in6->sin6_flowinfo = 0;
	in6->sin6_port = htons(port);
	in6->sin6_addr = in6addr_loopback;
}

static void *make_tcp6(const struct factory *factory, struct fdesc fdescs[],
		       int argc, char ** argv)
{
	struct sockaddr_in6 sin, cin;
	return make_tcp_common(factory, fdescs, argc, argv,
			       AF_INET6,
			       tcp6_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin, (struct sockaddr *)&cin);
}

static void *make_udp6(const struct factory *factory, struct fdesc fdescs[],
		       int argc, char ** argv)
{
	struct sockaddr_in6 sin, cin;
	return make_udp_common(factory, fdescs, argc, argv,
			       AF_INET6,
			       tcp6_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin, (struct sockaddr *)&cin);
}

static void raw6_init_addr(struct sockaddr *addr, bool remote_addr)
{
	struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)addr;
	memset(in6, 0, sizeof(*in6));
	in6->sin6_family = AF_INET6;
	in6->sin6_flowinfo = 0;

	if (remote_addr) {
		/* ::ffff:127.0.0.1 */
		in6->sin6_addr.s6_addr16[5] = 0xffff;
		in6->sin6_addr.s6_addr32[3] = htonl(INADDR_LOOPBACK);
	} else
		in6->sin6_addr = in6addr_loopback;
}

static void *make_raw6(const struct factory *factory, struct fdesc fdescs[],
		       int argc, char ** argv)
{
	struct sockaddr_in6 sin;
	return make_raw_common(factory, fdescs, argc, argv,
			       AF_INET6,
			       raw6_init_addr, sizeof(sin),
			       (struct sockaddr *)&sin);
}

static void ping6_init_addr(struct sockaddr *addr, unsigned short id)
{
	struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)addr;
	memset(in6, 0, sizeof(*in6));
	in6->sin6_family = AF_INET6;
	in6->sin6_port = htons(id);
	in6->sin6_addr = in6addr_loopback;
}

static void *make_ping6(const struct factory *factory, struct fdesc fdescs[],
			int argc, char ** argv)
{
	struct sockaddr_in6 in6;
	return make_ping_common(factory, fdescs, argc, argv,
				AF_INET6, IPPROTO_ICMPV6,
				ping6_init_addr,
				sizeof(in6),
				(struct sockaddr *)&in6);
}

#if HAVE_DECL_VMADDR_CID_LOCAL
static void *make_vsock(const struct factory *factory, struct fdesc fdescs[],
			int argc, char ** argv)
{
	struct sockaddr_vm svm;
	struct sockaddr_vm cvm;

	struct arg server_port = decode_arg("server-port", factory->params, argc, argv);
	unsigned short iserver_port = (unsigned short)ARG_INTEGER(server_port);
	struct arg client_port = decode_arg("client-port", factory->params, argc, argv);
	unsigned short iclient_port = (unsigned short)ARG_INTEGER(client_port);
	struct arg socktype = decode_arg("socktype", factory->params, argc, argv);
	int isocktype;
	int ssd, csd, asd = -1;

	const int y = 1;

	free_arg(&server_port);
	free_arg(&client_port);

	if (strcmp(ARG_STRING(socktype), "STREAM") == 0)
		isocktype = SOCK_STREAM;
	else if (strcmp(ARG_STRING(socktype), "DGRAM") == 0)
		isocktype = SOCK_DGRAM;
	else if (strcmp(ARG_STRING(socktype), "SEQPACKET") == 0)
		isocktype = SOCK_SEQPACKET;
	else
		errx(EXIT_FAILURE,
		     "unknown socket type for socket(AF_VSOCK,...): %s",
		     ARG_STRING(socktype));
	free_arg(&socktype);

	ssd = socket(AF_VSOCK, isocktype, 0);
	if (ssd < 0) {
		if (errno == ENODEV)
			err(EXIT_ENODEV, "failed to make a vsock socket for listening (maybe `modprobe vmw_vsock_vmci_transport'?)");
		err(EXIT_FAILURE,
		    "failed to make a vsock socket for listening");
	}

	if (setsockopt(ssd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (ssd != fdescs[0].fd) {
		if (dup2(ssd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ssd, fdescs[0].fd);
		}
		close(ssd);
		ssd = fdescs[0].fd;
	}

	memset(&svm, 0, sizeof(svm));
	svm.svm_family = AF_VSOCK;
	svm.svm_port = iserver_port;
	svm.svm_cid = VMADDR_CID_LOCAL;

	memset(&cvm, 0, sizeof(svm));
	cvm.svm_family = AF_VSOCK;
	cvm.svm_port = iclient_port;
	cvm.svm_cid = VMADDR_CID_LOCAL;

	if (bind(ssd, (struct sockaddr *)&svm, sizeof(svm)) < 0) {
		if (errno == EADDRNOTAVAIL)
			err(EXIT_EADDRNOTAVAIL, "failed to bind a listening socket (maybe `modprobe vsock_loopback'?)");
		err(EXIT_FAILURE, "failed to bind a listening socket");
	}


	if (isocktype == SOCK_DGRAM) {
		if (connect(ssd, (struct sockaddr *)&cvm, sizeof(cvm)) < 0)
			err(EXIT_FAILURE, "failed to connect the server socket to a client socket");
	} else {
		if (listen(ssd, 1) < 0)
			err(EXIT_FAILURE, "failed to listen a socket");
	}

	csd = socket(AF_VSOCK, isocktype, 0);
	if (csd < 0) {
		err(EXIT_FAILURE,
		    "failed to make a vsock client socket");
	}

	if (setsockopt(csd, SOL_SOCKET,
		       SO_REUSEADDR, (const char *)&y, sizeof(y)) < 0) {
		err(EXIT_FAILURE, "failed to setsockopt(SO_REUSEADDR)");
	}

	if (csd != fdescs[1].fd) {
		if (dup2(csd, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", csd, fdescs[1].fd);
		}
		close(csd);
		csd = fdescs[1].fd;
	}

	if (bind(csd, (struct sockaddr *)&cvm, sizeof(cvm)) < 0) {
		err(EXIT_FAILURE, "failed to bind a client socket");
	}

	if (connect(csd, (struct sockaddr *)&svm, sizeof(svm)) < 0) {
		err(EXIT_FAILURE, "failed to connect a client socket to the server socket");
	}

	if (isocktype != SOCK_DGRAM) {
		asd = accept(ssd, NULL, NULL);
		if (asd < 0) {
			err(EXIT_FAILURE, "failed to accept a socket from the listening socket");
		}
		if (asd != fdescs[2].fd) {
			if (dup2(asd, fdescs[2].fd) < 0) {
				err(EXIT_FAILURE, "failed to dup %d -> %d", asd, fdescs[2].fd);
			}
			close(asd);
			asd = fdescs[2].fd;
		}
	}

	fdescs[0] = (struct fdesc) {
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL,
	};
	fdescs[1] = (struct fdesc) {
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL,
	};

	fdescs[2] = (struct fdesc) {
		.fd    = (iserver_port == SOCK_DGRAM)? -1: fdescs[2].fd,
		.close = close_fdesc,
		.data  = NULL,
	};
	return NULL;
}
#endif	/* HAVE_DECL_VMADDR_CID_LOCAL */

#ifdef SIOCGSKNS
static void *make_netns(const struct factory *factory _U_, struct fdesc fdescs[],
			int argc _U_, char ** argv _U_)
{
	int sd = socket(AF_UNIX, SOCK_STREAM, 0);
	if (sd < 0)
		err(EXIT_FAILURE, "failed in socket()");

	int ns = ioctl(sd, SIOCGSKNS);
	if (ns < 0)
		err_nosys(EXIT_FAILURE, "failed in ioctl(SIOCGSKNS)");
	close(sd);

	if (ns != fdescs[0].fd) {
		if (dup2(ns, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ns, fdescs[0].fd);
		}
		close(ns);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}
#endif	/* SIOCGSKNS */

static void *make_netlink(const struct factory *factory, struct fdesc fdescs[],
			  int argc, char ** argv)
{
	struct arg protocol = decode_arg("protocol", factory->params, argc, argv);
	int iprotocol = ARG_INTEGER(protocol);
	struct arg groups = decode_arg("groups", factory->params, argc, argv);
	unsigned int ugroups = ARG_UINTEGER(groups);
	int sd;

	free_arg(&protocol);

	sd = socket(AF_NETLINK, SOCK_RAW, iprotocol);
	if (sd < 0)
		err((errno == EPROTONOSUPPORT)? EXIT_EPROTONOSUPPORT: EXIT_FAILURE,
		    "failed in socket()");

	if (sd != fdescs[0].fd) {
		if (dup2(sd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", sd, fdescs[0].fd);
		}
		close(sd);
		sd = fdescs[0].fd;
	}

	struct sockaddr_nl nl;
	memset(&nl, 0, sizeof(nl));
	nl.nl_family = AF_NETLINK;
	nl.nl_groups = ugroups;
	if (bind(sd, (struct sockaddr*)&nl, sizeof(nl)) < 0) {
		err(EXIT_FAILURE, "failed in bind(2)");
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_eventfd(const struct factory *factory _U_, struct fdesc fdescs[],
			  int argc _U_, char ** argv _U_)
{
	int fd;
	pid_t *pid = xcalloc(1, sizeof(*pid));

	if (fdescs[0].fd == fdescs[1].fd)
		errx(EXIT_FAILURE, "specify three different numbers as file descriptors");

	fd = eventfd(0, 0);
	if (fd < 0)
		err(EXIT_FAILURE, "failed in eventfd(2)");

	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	if (dup2(fdescs[0].fd, fdescs[1].fd) < 0) {
		err(EXIT_FAILURE, "failed to dup %d -> %d", fdescs[0].fd, fdescs[1].fd);
	}

	signal(SIGCHLD, abort_with_child_death_message);
	*pid = fork();
	if (*pid < 0) {
		err(EXIT_FAILURE, "failed in fork()");
	} else if (*pid == 0) {
		uint64_t v = 1;

		free(pid);
		close(fdescs[0].fd);

		signal(SIGCONT, do_nothing);
		/* Notify the parent that I'm ready. */
		if (write(fdescs[1].fd, &v, sizeof(v)) != sizeof(v)) {
			err(EXIT_FAILURE,
			    "failed in write() to notify the readiness to the prent");
		}
		/* Wait till the parent lets me go. */
		pause();

		close(fdescs[1].fd);
		exit(0);
	} else {
		uint64_t v;

		/* The child owns fdescs[1]. */
		close(fdescs[1].fd);
		fdescs[1].fd = -1;

		/* Wait till the child is ready. */
		if (read(fdescs[0].fd, &v, sizeof(uint64_t)) != sizeof(v)) {
			err(EXIT_FAILURE,
			    "failed in read() the readiness notification from the child");
		}
		signal(SIGCHLD, SIG_DFL);
	}

	return pid;
}

static void report_eventfd(const struct factory *factory _U_,
			   int nth, void *data, FILE *fp)
{
	if (nth == 0) {
		pid_t *child = data;
		fprintf(fp, "%d", *child);
	}
}

static void free_eventfd(const struct factory * factory _U_, void *data)
{
	pid_t child = *(pid_t *)data;
	int wstatus;

	free(data);

	kill(child, SIGCONT);
	if (waitpid(child, &wstatus, 0) < 0)
		err(EXIT_FAILURE, "failed in waitpid()");

	if (WIFEXITED(wstatus)) {
		int s = WEXITSTATUS(wstatus);
		if (s != 0)
			err(EXIT_FAILURE, "the child process got an error: %d", s);
	} else if (WIFSIGNALED(wstatus)) {
		int s = WTERMSIG(wstatus);
		if (WTERMSIG(wstatus) != 0)
			err(EXIT_FAILURE, "the child process got a signal: %d", s);
	}
}

struct mqueue_data {
	pid_t pid;
	const char *path;
	bool created;
};

static void mqueue_data_free(struct mqueue_data *data)
{
	if (data->created)
		mq_unlink(data->path);
	free((void *)data->path);
	free(data);
}

static void report_mqueue(const struct factory *factory _U_,
			  int nth, void *data, FILE *fp)
{
	if (nth == 0) {
		fprintf(fp, "%d", ((struct mqueue_data *)data)->pid);
	}
}

static void close_mqueue(int fd, void *data _U_)
{
	mq_close(fd);
}

static void free_mqueue(const struct factory * factory _U_, void *data)
{
	struct mqueue_data *mqueue_data = data;
	pid_t child = mqueue_data->pid;
	int wstatus;

	mqueue_data_free(mqueue_data);

	kill(child, SIGCONT);
	if (waitpid(child, &wstatus, 0) < 0)
		err(EXIT_FAILURE, "failed in waitpid()");

	if (WIFEXITED(wstatus)) {
		int s = WEXITSTATUS(wstatus);
		if (s != 0)
			err(EXIT_FAILURE, "the child process got an error: %d", s);
	} else if (WIFSIGNALED(wstatus)) {
		int s = WTERMSIG(wstatus);
		if (WTERMSIG(wstatus) != 0)
			err(EXIT_FAILURE, "the child process got a signal: %d", s);
	}
}

static void *make_mqueue(const struct factory *factory, struct fdesc fdescs[],
			 int argc, char ** argv)
{
	struct mqueue_data *mqueue_data;
	struct arg path = decode_arg("path", factory->params, argc, argv);
	const char *spath = ARG_STRING(path);

	struct mq_attr attr = {
		.mq_maxmsg = 1,
		.mq_msgsize = 1,
	};

	int fd;

	if (spath[0] != '/')
		errx(EXIT_FAILURE, "the path for mqueue must start with '/': %s", spath);

	if (spath[0] == '\0')
		err(EXIT_FAILURE, "the path should not be empty");

	if (fdescs[0].fd == fdescs[1].fd)
		errx(EXIT_FAILURE, "specify three different numbers as file descriptors");

	mqueue_data = xmalloc(sizeof(*mqueue_data));
	mqueue_data->pid = 0;
	mqueue_data->path = xstrdup(spath);
	mqueue_data->created = false;

	free_arg(&path);

	fd = mq_open(mqueue_data->path, O_CREAT|O_EXCL | O_RDONLY, S_IRUSR | S_IWUSR, &attr);
	if (fd < 0) {
		int e = errno;
		mqueue_data_free(mqueue_data);
		errno = e;
		err(EXIT_FAILURE, "failed in mq_open(3) for reading");
	}

	mqueue_data->created = true;
	if (fd != fdescs[0].fd) {
		if (dup2(fd, fdescs[0].fd) < 0) {
			int e = errno;
			mqueue_data_free(mqueue_data);
			errno = e;
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[0].fd);
		}
		mq_close(fd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_mqueue,
		.data  = NULL
	};

	fd = mq_open(mqueue_data->path, O_WRONLY, S_IRUSR | S_IWUSR, NULL);
	if (fd < 0) {
		int e = errno;
		mqueue_data_free(mqueue_data);
		errno = e;
		err(EXIT_FAILURE, "failed in mq_open(3) for writing");
	}

	if (fd != fdescs[1].fd) {
		if (dup2(fd, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", fd, fdescs[1].fd);
		}
		mq_close(fd);
	}
	fdescs[1] = (struct fdesc){
		.fd    = fdescs[1].fd,
		.close = close_mqueue,
		.data  = NULL
	};

	signal(SIGCHLD, abort_with_child_death_message);
	mqueue_data->pid = fork();
	if (mqueue_data->pid < 0) {
		int e = errno;
		mqueue_data_free(mqueue_data);
		errno = e;
		err(EXIT_FAILURE, "failed in fork()");
	} else if (mqueue_data->pid == 0) {
		mqueue_data->created = false;
		mqueue_data_free(mqueue_data);
		mq_close(fdescs[0].fd);

		signal(SIGCONT, do_nothing);
		/* Notify the parent that I'm ready. */
		if (mq_send(fdescs[1].fd, "", 0, 0) < 0)
			err(EXIT_FAILURE,
			    "failed in mq_send() to notify the readiness to the prent");
		/* Wait till the parent lets me go. */
		pause();

		mq_close(fdescs[1].fd);
		exit(0);
	} else {
		char c;

		/* The child owns fdescs[1]. */
		mq_close(fdescs[1].fd);
		fdescs[1].fd = -1;

		/* Wait till the child is ready. */
		if (mq_receive(fdescs[0].fd, &c, 1, NULL) < 0) {
			int e = errno;
			mqueue_data_free(mqueue_data);
			errno = e;
			err(EXIT_FAILURE,
			    "failed in mq_receive() the readiness notification from the child");
		}
		signal(SIGCHLD, SIG_DFL);
	}

	return mqueue_data;
}

struct sysvshm_data {
	void *addr;
	int id;
};

static void *make_sysvshm(const struct factory *factory _U_, struct fdesc fdescs[] _U_,
			  int argc _U_, char ** argv _U_)
{
	size_t pagesize = getpagesize();
	struct sysvshm_data *sysvshm_data;
	int id = shmget(IPC_PRIVATE, pagesize, IPC_CREAT | 0600);
	void *start;

	if (id == -1)
		err(EXIT_FAILURE, "failed to do shmget(.., %zu, ...)",
		    pagesize);

	start = shmat(id, NULL, SHM_RDONLY);
	if (start == (void *) -1) {
		int e = errno;
		shmctl(id, IPC_RMID, NULL);
		errno = e;
		err(EXIT_FAILURE, "failed to do shmat(%d,...)", id);
	}

	sysvshm_data = xmalloc(sizeof(*sysvshm_data));
	sysvshm_data->addr = start;
	sysvshm_data->id = id;
	return sysvshm_data;
}

static void free_sysvshm(const struct factory *factory _U_, void *data)
{
	struct sysvshm_data *sysvshm_data = data;

	shmdt(sysvshm_data->addr);
	shmctl(sysvshm_data->id, IPC_RMID, NULL);
}

static void *make_eventpoll(const struct factory *factory _U_, struct fdesc fdescs[],
			    int argc _U_, char ** argv _U_)
{
	int efd;
	struct spec {
		const char *file;
		int flag;
		uint32_t events;
	} specs [] = {
		{
			.file = "DUMMY, DONT'USE THIS"
		}, {
			.file = "/dev/random",
			.flag = O_RDONLY,
			.events = EPOLLIN,
		}, {
			.file = "/dev/random",
			.flag = O_WRONLY,
			.events = EPOLLOUT,
		},
	};

	efd = epoll_create(1);
	if (efd < 0)
		err(EXIT_FAILURE, "failed in epoll_create(2)");
	if (efd != fdescs[0].fd) {
		if (dup2(efd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", efd, fdescs[0].fd);
		}
		close(efd);
		efd = fdescs[0].fd;
	}
	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	for (size_t i = 1; i < ARRAY_SIZE(specs); i++) {
		int fd = open(specs[i].file, specs[i].flag);
		if (fd < 0) {
			err(EXIT_FAILURE, "failed in open(\"%s\",...)",
			    specs[i].file);
		}
		if (fd != fdescs[i].fd) {
			if (dup2(fd, fdescs[i].fd) < 0) {
				err(EXIT_FAILURE, "failed to dup %d -> %d",
				    fd, fdescs[i].fd);
			}
			close(fd);
		}
		fdescs[i] = (struct fdesc) {
			.fd = fdescs[i].fd,
			.close = close_fdesc,
			.data = NULL
		};
		if (epoll_ctl(efd, EPOLL_CTL_ADD, fdescs[i].fd,
			      &(struct epoll_event) {
				      .events = specs[i].events,
				      .data = {.ptr = NULL,}
			      }) < 0) {
			err(EXIT_FAILURE,
			    "failed to add fd %d to the eventpoll fd with epoll_ctl",
			    fdescs[i].fd);
		}
	}

	return NULL;
}

static bool decode_clockid(const char *sclockid, clockid_t *clockid)
{
	if (sclockid == NULL)
		return false;
	if (sclockid[0] == '\0')
		return false;

	if (strcmp(sclockid, "realtime") == 0)
		*clockid = CLOCK_REALTIME;
	else if (strcmp(sclockid, "monotonic") == 0)
		*clockid = CLOCK_MONOTONIC;
	else if (strcmp(sclockid, "boottime") == 0)
		*clockid = CLOCK_BOOTTIME;
	else if (strcmp(sclockid, "realtime-alarm") == 0)
		*clockid = CLOCK_REALTIME_ALARM;
	else if (strcmp(sclockid, "boottime-alarm") == 0)
		*clockid = CLOCK_BOOTTIME_ALARM;
	else
		return false;
	return true;
}

static void *make_timerfd(const struct factory *factory, struct fdesc fdescs[],
			  int argc, char ** argv)
{
	int tfd;
	struct timespec now;
	struct itimerspec tspec;

	struct arg abstime = decode_arg("abstime", factory->params, argc, argv);
	bool babstime = ARG_BOOLEAN(abstime);

	struct arg remaining = decode_arg("remaining", factory->params, argc, argv);
	unsigned int uremaining = ARG_UINTEGER(remaining);

	struct arg interval = decode_arg("interval", factory->params, argc, argv);
	unsigned int uinterval = ARG_UINTEGER(interval);

	struct arg interval_frac = decode_arg("interval-nanofrac", factory->params, argc, argv);
	unsigned int uinterval_frac = ARG_UINTEGER(interval_frac);

	struct arg clockid_ = decode_arg("clockid", factory->params, argc, argv);
	const char *sclockid = ARG_STRING(clockid_);
	clockid_t clockid;

	if (decode_clockid(sclockid, &clockid) == false)
		err(EXIT_FAILURE, "unknown clockid: %s", sclockid);

	free_arg(&clockid_);
	free_arg(&interval_frac);
	free_arg(&interval);
	free_arg(&remaining);
	free_arg(&abstime);

	if (babstime && (clock_gettime(clockid, &now) == -1))
		err(EXIT_FAILURE, "failed in clock_gettime(2)");

	tfd = timerfd_create(clockid, 0);
	if (tfd < 0)
		err(EXIT_FAILURE, "failed in timerfd_create(2)");

	tspec.it_value.tv_sec = (babstime? now.tv_sec: 0) + uremaining;
	tspec.it_value.tv_nsec = (babstime? now.tv_nsec: 0);

	tspec.it_interval.tv_sec = uinterval;
	tspec.it_interval.tv_nsec = uinterval_frac;

	if (timerfd_settime(tfd, babstime? TFD_TIMER_ABSTIME: 0, &tspec, NULL) < 0) {
		err(EXIT_FAILURE, "failed in timerfd_settime(2)");
	}

	if (tfd != fdescs[0].fd) {
		if (dup2(tfd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", tfd, fdescs[0].fd);
		}
		close(tfd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_signalfd(const struct factory *factory _U_, struct fdesc fdescs[],
			   int argc _U_, char ** argv _U_)
{
	sigset_t mask;
	int numsig = 42;

	if (sigemptyset(&mask) < 0)
		err(EXIT_FAILURE, "failed in sigemptyset()");
	if (sigaddset(&mask, SIGFPE) < 0)
		err(EXIT_FAILURE, "failed in sigaddset(FPE)");
	if (sigaddset(&mask, SIGUSR1) < 0)
		err(EXIT_FAILURE, "failed in sigaddset(USR1)");
	if (sigaddset(&mask, numsig) < 0)
		err(EXIT_FAILURE, "failed in sigaddset(%d)", numsig);

	int sfd= signalfd(-1, &mask, 0);
	if (sfd < 0)
		err(EXIT_FAILURE, "failed in signalfd(2)");

	if (sfd != fdescs[0].fd) {
		if (dup2(sfd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", sfd, fdescs[0].fd);
		}
		close(sfd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}


/* ref. linux/Documentation/networking/tuntap.rst */
static void *make_cdev_tun(const struct factory *factory _U_, struct fdesc fdescs[],
			   int argc _U_, char ** argv _U_)
{
	int tfd = open("/dev/net/tun", O_RDWR);
	struct ifreq ifr;

	if (tfd < 0)
		err(EXIT_FAILURE, "failed in opening /dev/net/tun");

	memset(&ifr, 0, sizeof(ifr));

	ifr.ifr_flags = IFF_TUN;
	strcpy(ifr.ifr_name, "mkfds%d");

	if (ioctl(tfd, TUNSETIFF, (void *) &ifr) < 0) {
		err(EXIT_FAILURE, "failed in setting \"lo\" to the tun device");
	}

	if (tfd != fdescs[0].fd) {
		if (dup2(tfd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", tfd, fdescs[0].fd);
		}
		close(tfd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return xstrdup(ifr.ifr_name);
}

static void report_cdev_tun(const struct factory *factory _U_,
			    int nth, void *data, FILE *fp)
{
	if (nth == 0) {
		char *devname = data;
		fprintf(fp, "%s", devname);
	}
}

static void free_cdev_tun(const struct factory * factory _U_, void *data)
{
	free(data);
}

static void *make_bpf_prog(const struct factory *factory, struct fdesc fdescs[],
			   int argc, char ** argv)
{
	struct arg prog_type_id = decode_arg("prog-type-id", factory->params, argc, argv);
	int iprog_type_id = ARG_INTEGER(prog_type_id);

	struct arg name = decode_arg("name", factory->params, argc, argv);
	const char *sname = ARG_STRING(name);

	int bfd;
	union bpf_attr attr;
	/* Just doing exit with 0. */
	struct bpf_insn insns[] = {
		[0] = {
			.code  = BPF_ALU64 | BPF_MOV | BPF_K,
			.dst_reg = BPF_REG_0, .src_reg = 0, .off   = 0, .imm   = 0
		},
		[1] = {
			.code  = BPF_JMP | BPF_EXIT,
			.dst_reg = 0, .src_reg = 0, .off   = 0, .imm   = 0
		},
	};

	struct bpf_prog_info info = {};

	memset(&attr, 0, sizeof(attr));
	attr.prog_type = iprog_type_id;
	attr.insns = (uint64_t)(unsigned long)insns;
	attr.insn_cnt = ARRAY_SIZE(insns);
	attr.license = (int64_t)(unsigned long)"GPL";
	strncpy(attr.prog_name, sname, sizeof(attr.prog_name) - 1);

	free_arg(&name);
	free_arg(&prog_type_id);

	bfd = syscall(SYS_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
	if (bfd < 0)
		err_nosys(EXIT_FAILURE, "failed in bpf(BPF_PROG_LOAD)");


	memset(&attr, 0, sizeof(attr));
	attr.info.bpf_fd = bfd;
	attr.info.info_len = sizeof(info);
	attr.info.info = (uint64_t)(unsigned long)&info;
	if (syscall(SYS_bpf, BPF_OBJ_GET_INFO_BY_FD, &attr, sizeof(attr)) < 0)
		err_nosys(EXIT_FAILURE, "failed in bpf(BPF_OBJ_GET_INFO_BY_FD)");

	if (bfd != fdescs[0].fd) {
		if (dup2(bfd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", bfd, fdescs[0].fd);
		}
		close(bfd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return xmemdup(&info, sizeof(info));
}

enum ritem_bpf_prog {
	RITEM_BPF_PROG_ID,
	RITEM_BPF_PROG_TAG,
};

static void report_bpf_prog(const struct factory *factory _U_,
			    int nth, void *data, FILE *fp)
{
	struct bpf_prog_info *info = data;

	switch (nth) {
	case RITEM_BPF_PROG_ID:
		fprintf(fp, "%u", info->id);
		break;
	case RITEM_BPF_PROG_TAG:
		for (size_t i = 0; i < BPF_TAG_SIZE; i++) {
			unsigned char ch = (info->tag[i] >> 4);
			unsigned char cl = info->tag[i] & 0x0f;

			fprintf(fp, "%x", (unsigned int)ch);
			fprintf(fp, "%x", (unsigned int)cl);
		}
		break;
	}
}

static void free_bpf_prog(const struct factory * factory _U_, void *data)
{
	free(data);
}

static void *make_some_pipes(const struct factory *factory _U_, struct fdesc fdescs[],
			     int argc _U_, char ** argv _U_)
{
	/* Reserver fds before making pipes */
	for (int i = 0; i < factory->N; i++) {
		close(fdescs[i].fd);
		if (dup2(0, fdescs[0].fd) < 0)
			err(EXIT_FAILURE, "failed to reserve fd %d with dup2", fdescs[0].fd);
	}

	for (int i = 0; i < (factory->N) / 2; i++) {
		int pd[2];
		unsigned int mode;
		int r = 0, w = 1;

		mode = 1 << (i % 3);
		if (mode == MX_WRITE) {
			r = 1;
			w = 0;
		}

		if (pipe(pd) < 0)
			err(EXIT_FAILURE, "failed to make pipe");

		if (dup2(pd[0], fdescs[2 * i + r].fd) < 0)
			err(EXIT_FAILURE, "failed to dup %d -> %d", pd[0], fdescs[2 * i + r].fd);
		close(pd[0]);
		fdescs[2 * 1 + r].close = close_fdesc;

		if (dup2(pd[1], fdescs[2 * i + w].fd) < 0)
			err(EXIT_FAILURE, "failed to dup %d -> %d", pd[1], fdescs[2 * i + 2].fd);
		close(pd[1]);
		fdescs[2 * 1 + w].close = close_fdesc;

		fdescs[2 * i].mx_modes |= mode;

		/* Make the pipe for writing full. */
		if (fdescs[2 * i].mx_modes & MX_WRITE) {
			int n = fcntl(fdescs[2 * i].fd, F_GETPIPE_SZ);
			char *buf;

			if (n < 0)
				err(EXIT_FAILURE, "failed to get PIPE BUFFER SIZE from %d", fdescs[2 * i].fd);

			buf = xmalloc(n);
			if (write(fdescs[2 * i].fd, buf, n) != n)
				err(EXIT_FAILURE, "failed to fill the pipe buffer specified with %d",
				    fdescs[2 * i].fd);
			free(buf);
		}

	}

	return NULL;
}

static void *make_bpf_map(const struct factory *factory, struct fdesc fdescs[],
			  int argc, char ** argv)
{
	struct arg map_type_id = decode_arg("map-type-id", factory->params, argc, argv);
	int imap_type_id = ARG_INTEGER(map_type_id);

	struct arg name = decode_arg("name", factory->params, argc, argv);
	const char *sname = ARG_STRING(name);

	int bfd;
	union bpf_attr attr = {
		.map_type = imap_type_id,
		.key_size = 4,
		.value_size = 4,
		.max_entries = 10,
	};

	strncpy(attr.map_name, sname, sizeof(attr.map_name) - 1);

	free_arg(&name);
	free_arg(&map_type_id);

	bfd = syscall(SYS_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
	if (bfd < 0)
		err_nosys(EXIT_FAILURE, "failed in bpf(BPF_MAP_CREATE)");

	if (bfd != fdescs[0].fd) {
		if (dup2(bfd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", bfd, fdescs[0].fd);
		}
		close(bfd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_pty(const struct factory *factory _U_, struct fdesc fdescs[],
		      int argc _U_, char ** argv _U_)
{
	int index, *indexp;
	char *pts;
	int pts_fd;
	int ptmx_fd = posix_openpt(O_RDWR);
	if (ptmx_fd < 0)
		err(EXIT_FAILURE, "failed in opening /dev/ptmx");

	if (unlockpt(ptmx_fd) < 0) {
		err(EXIT_FAILURE, "failed in unlockpt()");
	}

	if (ioctl(ptmx_fd, TIOCGPTN, &index) < 0) {
		err(EXIT_FAILURE, "failed in ioctl(TIOCGPTN)");
	}

	pts = ptsname(ptmx_fd);
	if (pts == NULL) {
		err(EXIT_FAILURE, "failed in ptsname()");
	}

	if (ptmx_fd != fdescs[0].fd) {
		if (dup2(ptmx_fd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", ptmx_fd, fdescs[0].fd);
		}
		close(ptmx_fd);
		ptmx_fd = fdescs[0].fd;
	}

	pts_fd = open(pts, O_RDONLY);
	if (pts_fd < 0) {
		err(EXIT_FAILURE, "failed in opening %s", pts);
	}

	if (pts_fd != fdescs[1].fd) {
		if (dup2(pts_fd, fdescs[1].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", pts_fd, fdescs[1].fd);
		}
		close(pts_fd);
		pts_fd = fdescs[1].fd;
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};
	fdescs[1] = (struct fdesc){
		.fd    = fdescs[1].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	indexp = xmemdup(&index, sizeof(index));
	return indexp;
}

static void report_pty(const struct factory *factory _U_,
		       int nth, void *data, FILE *fp)
{
	if (nth == 0) {
		int *index = data;
		fprintf(fp, "%d", *index);
	}
}

static void free_pty(const struct factory * factory _U_, void *data)
{
	free(data);
}

struct mmap_data {
	char *addr;
	size_t len;
};

static void *make_mmap(const struct factory *factory, struct fdesc fdescs[] _U_,
		       int argc, char ** argv)
{
	struct arg file = decode_arg("file", factory->params, argc, argv);
	const char *sfile = ARG_STRING(file);

	int fd = open(sfile, O_RDONLY);
	if (fd < 0)
		err(EXIT_FAILURE, "failed in opening %s", sfile);
	free_arg(&file);

	struct stat sb;
	if (fstat(fd, &sb) < 0) {
		err(EXIT_FAILURE, "failed in fstat()");
	}
	char *addr = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
	if (addr == MAP_FAILED) {
		err(EXIT_FAILURE, "failed in mmap()");
	}
	close(fd);

	struct mmap_data *data = xmalloc(sizeof(*data));
	data->addr = addr;
	data->len = sb.st_size;

	return data;
}

/* Do as unshare --map-root-user. */
static void map_root_user(uid_t uid, uid_t gid)
{
	char buf[BUFSIZ];
	int n;
	int mapfd;
	int r;

	n = snprintf(buf, sizeof(buf), "0 %d 1", uid);
	mapfd = open("/proc/self/uid_map", O_WRONLY);
	if (mapfd < 0)
		err(EXIT_FAILURE,
		    "failed to open /proc/self/uid_map");
	r = write (mapfd, buf, n);
	if (r < 0)
		err((errno == EPERM? EXIT_EPERM: EXIT_FAILURE),
		    "failed to write to /proc/self/uid_map");
	if (r != n)
		errx(EXIT_FAILURE,
		     "failed to write to /proc/self/uid_map");
	close(mapfd);

	mapfd = open("/proc/self/setgroups", O_WRONLY);
	if (mapfd < 0)
		err(EXIT_FAILURE,
		    "failed to open /proc/self/setgroups");
	r = write (mapfd, "deny", 4);
	if (r < 0)
		err(EXIT_FAILURE,
		    "failed to write to /proc/self/setgroups");
	if (r != 4)
		errx(EXIT_FAILURE,
		     "failed to write to /proc/self/setgroups");
	close(mapfd);

	n = snprintf(buf, sizeof(buf), "0 %d 1", gid);
	mapfd = open("/proc/self/gid_map", O_WRONLY);
	if (mapfd < 0)
		err(EXIT_FAILURE,
		    "failed to open /proc/self/gid_map");
	r = write (mapfd, buf, n);
	if (r < 0)
		err(EXIT_FAILURE,
		    "failed to write to /proc/self/gid_map");
	if (r != n)
		errx(EXIT_FAILURE,
		     "failed to write to /proc/self/gid_map");
	close(mapfd);
}

static void *make_userns(const struct factory *factory _U_, struct fdesc fdescs[],
			 int argc _U_, char ** argv _U_)
{
	uid_t uid = geteuid();
	uid_t gid = getegid();

	if (unshare(CLONE_NEWUSER) < 0)
		err((errno == EPERM? EXIT_EPERM: EXIT_FAILURE),
		    "failed in the 1st unshare(2)");

	map_root_user(uid, gid);

	int userns = open("/proc/self/ns/user", O_RDONLY);
	if (userns < 0)
		err(EXIT_FAILURE, "failed to open /proc/self/ns/user for the new user ns");

	if (unshare(CLONE_NEWUSER) < 0) {
		err((errno == EPERM? EXIT_EPERM: EXIT_FAILURE),
		    "failed in the 2nd unshare(2)");
	}

	if (userns != fdescs[0].fd) {
		if (dup2(userns, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", userns, fdescs[0].fd);
		}
		close(userns);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void free_mmap(const struct factory * factory _U_, void *data)
{
	munmap(((struct mmap_data *)data)->addr,
	       ((struct mmap_data *)data)->len);
}

static int send_diag_request(int diagsd, void *req, size_t req_size)
{
	struct sockaddr_nl nladdr = {
		.nl_family = AF_NETLINK,
	};

	struct nlmsghdr nlh = {
		.nlmsg_len = sizeof(nlh) + req_size,
		.nlmsg_type = SOCK_DIAG_BY_FAMILY,
		.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP,
	};

	struct iovec iovecs[] = {
		{ &nlh, sizeof(nlh) },
		{ req, req_size },
	};

	const struct msghdr mhd = {
		.msg_namelen = sizeof(nladdr),
		.msg_name = &nladdr,
		.msg_iovlen = ARRAY_SIZE(iovecs),
		.msg_iov = iovecs,
	};

	if (sendmsg(diagsd, &mhd, 0) < 0)
		return errno;

	return 0;
}

static int recv_diag_request(int diagsd)
{
	__attribute__((aligned(sizeof(void *)))) uint8_t buf[8192];
	const struct nlmsghdr *h;
	int r = recvfrom(diagsd, buf, sizeof(buf), 0, NULL, NULL);;
	if (r < 0)
		return errno;

	h = (void *)buf;
	if (!NLMSG_OK(h, (size_t)r))
		return -1;

	if (h->nlmsg_type == NLMSG_ERROR) {
		struct nlmsgerr *e = (struct nlmsgerr *)NLMSG_DATA(h);
		return - e->error;
	}
	return 0;
}

static void *make_sockdiag(const struct factory *factory, struct fdesc fdescs[],
			   int argc, char ** argv)
{
	struct arg family = decode_arg("family", factory->params, argc, argv);
	const char *sfamily = ARG_STRING(family);
	int ifamily;
	struct arg type = decode_arg("type", factory->params, argc, argv);
	const char *stype = ARG_STRING(type);
	int itype;
	int diagsd;
	void *req = NULL;
	size_t reqlen = 0;
	int e;
	struct unix_diag_req udr;
	struct vsock_diag_req vdr;

	if (strcmp(sfamily, "unix") == 0)
		ifamily = AF_UNIX;
	else if (strcmp(sfamily, "vsock") == 0)
		ifamily = AF_VSOCK;
	else
		errx(EXIT_FAILURE, "unknown/unsupported family: %s", sfamily);

	if (strcmp(stype, "dgram") == 0)
		itype = SOCK_DGRAM;
	else if (strcmp(stype, "raw") == 0)
		itype = SOCK_RAW;
	else
		errx(EXIT_FAILURE, "unknown/unsupported type: %s", stype);


	diagsd = socket(AF_NETLINK, itype, NETLINK_SOCK_DIAG);
	if (diagsd < 0)
		err(errno == EPROTONOSUPPORT? EXIT_EPROTONOSUPPORT: EXIT_FAILURE,
		    "failed in socket(AF_NETLINK, %s, NETLINK_SOCK_DIAG)", stype);
	free_arg(&family);
	free_arg(&type);

	if (ifamily == AF_UNIX) {
		udr = (struct unix_diag_req) {
			.sdiag_family = AF_UNIX,
			.udiag_states = -1, /* set the all bits. */
			.udiag_show = UDIAG_SHOW_NAME | UDIAG_SHOW_PEER | UNIX_DIAG_SHUTDOWN,
		};
		req = &udr;
		reqlen = sizeof(udr);
	} else if (ifamily == AF_VSOCK) {
		vdr = (struct vsock_diag_req) {
			.sdiag_family = AF_VSOCK,
			.vdiag_states = ~(uint32_t)0,
		};
		req = &vdr;
		reqlen = sizeof(vdr);
	}

	e = send_diag_request(diagsd, req, reqlen);
	if (e) {
		close (diagsd);
		errno = e;
		if (errno == EACCES)
			err(EXIT_EACCES, "failed in sendmsg()");
		if (errno == ENOENT)
			err(EXIT_ENOENT, "failed in sendmsg()");
		err(EXIT_FAILURE, "failed in sendmsg()");
	}

	e = recv_diag_request(diagsd);
	if (e != 0) {
		close (diagsd);
		if (e == ENOENT)
			err(EXIT_ENOENT, "failed in recvfrom()");
		if (e > 0)
			err(EXIT_FAILURE, "failed in recvfrom()");
		if (e < 0)
			errx(EXIT_FAILURE, "failed in recvfrom() => -1");
	}

	if (diagsd != fdescs[0].fd) {
		if (dup2(diagsd, fdescs[0].fd) < 0) {
			err(EXIT_FAILURE, "failed to dup %d -> %d", diagsd, fdescs[0].fd);
		}
		close(diagsd);
	}

	fdescs[0] = (struct fdesc){
		.fd    = fdescs[0].fd,
		.close = close_fdesc,
		.data  = NULL
	};

	return NULL;
}

static void *make_foreign_sockets(const struct factory *factory _U_, struct fdesc fdescs[],
				  int argc _U_, char ** argv _U_)
{
	int foreign_sd[2];	/* These two */
	int original_ns;
	int foreign_ns;
	struct stat foreign_ns_sb;

	original_ns = open("/proc/self/ns/net", O_RDONLY);
	if (original_ns < 0)
		err(EXIT_FAILURE, "failed in open(/proc/self/ns/net) before unshare");

	if (unshare(CLONE_NEWNET) < 0)
		err((errno == EPERM? EXIT_EPERM: EXIT_FAILURE),
		    "failed in unshare()");

	foreign_ns = open("/proc/self/ns/net", O_RDONLY);
	if (foreign_ns < 0)
		err(EXIT_FAILURE, "failed in open(/proc/self/ns/net) after unshare");
	if (fstat(foreign_ns, &foreign_ns_sb) < 0)
			err(EXIT_FAILURE, "failed in fstat(NETNS)");

	if (socketpair(AF_UNIX, SOCK_STREAM, 0, foreign_sd) < 0)
		err(EXIT_FAILURE, "failed in socketpair(SOCK_STREAM)");

	if (setns(original_ns, CLONE_NEWNET) < 0)
		err(EXIT_FAILURE, "failed in setns()");

	close(foreign_ns);	/* Make the namespace unreadable. */
	close(original_ns);

	for (int i = 0; i < 2; i++) {
		if (foreign_sd[i] != fdescs[i].fd) {
			if (dup2(foreign_sd[i], fdescs[i].fd) < 0)
				err(EXIT_FAILURE, "failed to dup %d -> %d",
				    foreign_sd[i], fdescs[i].fd);
			close(foreign_sd[i]);
		}
		fdescs[i] = (struct fdesc){
			.fd    = fdescs[i].fd,
			.close = close_fdesc,
			.data  = NULL
		};
	}

	return xmemdup(&foreign_ns_sb.st_ino, sizeof(foreign_ns_sb.st_ino));
}

static void report_foreign_sockets(const struct factory *factory _U_,
				   int nth, void *data, FILE *fp)
{
	if (nth == 0) {
		long *netns_id = (long *)data;
		fprintf(fp, "%ld", *netns_id);
	}
}

static void free_foreign_sockets(const struct factory * factory _U_, void *data)
{
	free (data);
}

#define PARAM_END { .name = NULL, }
static const struct factory factories[] = {
	{
		.name = "ro-regular-file",
		.desc = "read-only regular file",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = open_ro_regular_file,
		.params = (struct parameter []) {
			{
				.name = "file",
				.type = PTYPE_STRING,
				.desc = "file to be opened",
				.defv.string = "/etc/passwd",
			},
			{
				.name = "offset",
				.type = PTYPE_INTEGER,
				.desc = "seek bytes after open with SEEK_CUR",
				.defv.integer = 0,
			},
			{
				.name = "read-lease",
				.type = PTYPE_BOOLEAN,
				.desc = "taking out read lease for the file",
				.defv.boolean = false,
			},
			PARAM_END
		},
	},
	{
		.name = "make-regular-file",
		.desc = "regular file for writing",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_w_regular_file,
		.free = free_after_closing_duplicated_fd,
		.params = (struct parameter []) {
			{
				.name = "file",
				.type = PTYPE_STRING,
				.desc = "file to be made",
				.defv.string = "./test_mkfds_make_regular_file",
			},
			{
				.name = "delete",
				.type = PTYPE_BOOLEAN,
				.desc = "delete the file just after making it",
				.defv.boolean = false,
			},
			{
				.name = "write-bytes",
				.type = PTYPE_INTEGER,
				.desc = "write something (> 0)",
				.defv.integer = 0,
			},
			{
				.name = "readable",
				.type = PTYPE_BOOLEAN,
				.desc = "open the new file readable way",
				.defv.boolean = false,
			},
			{
				.name = "lock",
				.type = PTYPE_STRING,
				.desc = "the way for file locking: [none]|flock-sh|flock-ex|posix-r-|posix--w|posix-rw|ofd-r-|ofd--w|ofd-rw|lease-w",
				.defv.string = "none",
			},
			{
				.name = "dupfd",
				.type = PTYPE_INTEGER,
				.desc = "the number for the fd duplicated from the original fd",
				.defv.integer = -1,
			},
			PARAM_END
		},
	},
	{
		.name = "pipe-no-fork",
		.desc = "making pair of fds with pipe(2)",
		.priv = false,
		.N    = 2,
		.EX_N = 2,
		.make = make_pipe,
		.params = (struct parameter []) {
			{
				.name = "nonblock",
				.type = PTYPE_STRING,
				.desc = "set nonblock flag (\"--\", \"r-\", \"-w\", or \"rw\")",
				.defv.string = "--",
			},
			{
				.name = "rdup",
				.type = PTYPE_INTEGER,
				.desc = "file descriptor for duplicating the pipe input",
				.defv.integer = -1,
			},
			{
				.name = "wdup",
				.type = PTYPE_INTEGER,
				.desc = "file descriptor for duplicating the pipe output",
				.defv.integer = -1,
			},
			PARAM_END
		},
	},
	{
		.name = "directory",
		.desc = "directory",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = open_directory,
		.params = (struct parameter []) {
			{
				.name = "dir",
				.type = PTYPE_STRING,
				.desc = "directory to be opened",
				.defv.string = "/",
			},
			{
				.name = "dentries",
				.type = PTYPE_INTEGER,
				.desc = "read the number of dentries after open with readdir(3)",
				.defv.integer = 0,
			},
			PARAM_END
		},
	},
	{
		.name = "rw-character-device",
		.desc = "character device with O_RDWR flag",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = open_rw_chrdev,
		.params = (struct parameter []) {
			{
				.name = "chrdev",
				.type = PTYPE_STRING,
				.desc = "character device node to be opened",
				.defv.string = "/dev/zero",
			},
			PARAM_END
		},
	},
	{
		.name = "socketpair",
		.desc = "AF_UNIX socket pair created with socketpair(2)",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.make = make_socketpair,
		.params = (struct parameter []) {
			{
				.name = "socktype",
				.type = PTYPE_STRING,
				.desc = "STREAM, DGRAM, or SEQPACKET",
				.defv.string = "STREAM",
			},
			{
				.name = "halfclose",
				.type = PTYPE_BOOLEAN,
				.desc = "Shutdown the read end of the 1st socket, the write end of the 2nd socket",
				.defv.boolean = false,
			},
			PARAM_END
		},
	},
	{
		.name = "symlink",
		.desc = "symbolic link itself opened with O_PATH",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = open_with_opath,
		.params = (struct parameter []) {
			{
				.name = "path",
				.type = PTYPE_STRING,
				.desc = "path to a symbolic link",
				.defv.string = "/dev/stdin",
			},
			PARAM_END
		},
	},
	{
		.name = "ro-block-device",
		.desc = "block device with O_RDONLY flag",
		.priv = true,
		.N = 1,
		.EX_N = 0,
		.make = open_ro_blkdev,
		.params = (struct parameter []) {
			{
				.name = "blkdev",
				.type = PTYPE_STRING,
				.desc = "block device node to be opened",
				.defv.string = "/dev/nullb0",
			},
			PARAM_END
		},
	},
	{
		.name = "mapped-packet-socket",
		.desc = "mmap'ed AF_PACKET socket",
		.priv = true,
		.N = 1,
		.EX_N = 0,
		.make = make_mmapped_packet_socket,
		.params = (struct parameter []) {
			{
				.name = "socktype",
				.type = PTYPE_STRING,
				.desc = "DGRAM or RAW",
				.defv.string = "RAW",
			},
			{
				.name = "interface",
				.type = PTYPE_STRING,
				.desc = "a name of network interface like eth0 or lo",
				.defv.string = "lo",
			},
			PARAM_END
		},
	},
	{
		.name = "pidfd",
		.desc = "pidfd returned from pidfd_open(2)",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_pidfd,
		.params = (struct parameter []) {
			{
				.name = "target-pid",
				.type = PTYPE_INTEGER,
				.desc = "the pid of the target process",
				.defv.integer = 1,
			},
			PARAM_END
		},
	},
	{
		.name = "inotify",
		.desc = "inotify fd returned from inotify_init(2)",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_inotify_fd,
		.params = (struct parameter []) {
			{
				.name = "dir",
				.type = PTYPE_STRING,
				.desc = "the directory that the inotify monitors",
				.defv.string = "/",
			},
			{
				.name = "file",
				.type = PTYPE_STRING,
				.desc = "the file that the inotify monitors",
				.defv.string = "/etc/fstab",
			},
			PARAM_END
		},
	},
	{
		.name = "unix-stream",
		.desc = "AF_UNIX+SOCK_STREAM sockets",
		.priv = false,
		.N    = 3,
		.EX_N = 0,
		.make = make_unix_stream,
		.params = (struct parameter []) {
			{
				.name = "path",
				.type = PTYPE_STRING,
				.desc = "path for listening-socket bound to",
				.defv.string = "/tmp/test_mkfds-unix-stream",
			},
			{
				.name = "backlog",
				.type = PTYPE_INTEGER,
				.desc = "backlog passed to listen(2)",
				.defv.integer = 5,
			},
			{
				.name = "abstract",
				.type = PTYPE_BOOLEAN,
				.desc = "use PATH as an abstract socket address",
				.defv.boolean = false,
			},
			{
				.name = "server-shutdown",
				.type = PTYPE_INTEGER,
				.desc = "shutdown the accepted socket; 1: R, 2: W, 3: RW",
				.defv.integer = 0,
			},
			{
				.name = "client-shutdown",
				.type = PTYPE_INTEGER,
				.desc = "shutdown the client socket; 1: R, 2: W, 3: RW",
				.defv.integer = 0,
			},
			{
				.name = "type",
				.type = PTYPE_STRING,
				.desc = "stream or seqpacket",
				.defv.string = "stream",
			},
			PARAM_END
		},
	},
	{
		.name = "unix-dgram",
		.desc = "AF_UNIX+SOCK_DGRAM sockets",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.make = make_unix_dgram,
		.params = (struct parameter []) {
			{
				.name = "path",
				.type = PTYPE_STRING,
				.desc = "path for unix non-stream bound to",
				.defv.string = "/tmp/test_mkfds-unix-dgram",
			},
			{
				.name = "abstract",
				.type = PTYPE_BOOLEAN,
				.desc = "use PATH as an abstract socket address",
				.defv.boolean = false,
			},
			PARAM_END
		},
	},
	{
		.name = "unix-in-netns",
		.desc = "make a unix socket in a new network namespace",
		.priv = true,
		.N    = 3,
		.EX_N = 0,
		.make = make_unix_in_new_netns,
		.params = (struct parameter []) {
			{
				.name = "type",
				.type = PTYPE_STRING,
				.desc = "dgram, stream, or seqpacket",
				.defv.string = "stream",
			},
			{
				.name = "path",
				.type = PTYPE_STRING,
				.desc = "path for unix non-stream bound to",
				.defv.string = "/tmp/test_mkfds-unix-in-netns",
			},
			{
				.name = "abstract",
				.type = PTYPE_BOOLEAN,
				.desc = "use PATH as an abstract socket address",
				.defv.boolean = false,
			},
			PARAM_END
		},
	},
	{
		.name = "tcp",
		.desc = "AF_INET+SOCK_STREAM sockets",
		.priv = false,
		.N    = 3,
		.EX_N = 0,
		.make = make_tcp,
		.params = (struct parameter []) {
			{
				.name = "server-port",
				.type = PTYPE_INTEGER,
				.desc = "TCP port the server may listen",
				.defv.integer = 12345,
			},
			{
				.name = "client-port",
				.type = PTYPE_INTEGER,
				.desc = "TCP port the client may bind",
				.defv.integer = 23456,
			},
			PARAM_END
		}
	},
	{
		.name = "udp",
		.desc = "AF_INET+SOCK_DGRAM sockets",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.make = make_udp,
		.params = (struct parameter []) {
			{
				.name = "lite",
				.type = PTYPE_BOOLEAN,
				.desc = "Use UDPLITE instead of UDP",
				.defv.boolean = false,
			},
			{
				.name = "server-port",
				.type = PTYPE_INTEGER,
				.desc = "UDP port the server may listen",
				.defv.integer = 12345,
			},
			{
				.name = "client-port",
				.type = PTYPE_INTEGER,
				.desc = "UDP port the client may bind",
				.defv.integer = 23456,
			},
			{
				.name = "server-do-bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind with the server socket",
				.defv.boolean = true,
			},
			{
				.name = "client-do-bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind with the client socket",
				.defv.boolean = true,
			},
			{
				.name = "client-do-connect",
				.type = PTYPE_BOOLEAN,
				.desc = "call connect with the client socket",
				.defv.boolean = true,
			},
			PARAM_END
		}
	},
	{
		.name = "raw",
		.desc = "AF_INET+SOCK_RAW sockets",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.make = make_raw,
		.params = (struct parameter []) {
			{
				.name = "protocol",
				.type = PTYPE_INTEGER,
				.desc = "protocol passed to socket(AF_INET, SOCK_RAW, protocol)",
				.defv.integer = IPPROTO_IPIP,
			},
			PARAM_END
		}

	},
	{
		.name = "ping",
		.desc = "AF_INET+SOCK_DGRAM+IPPROTO_ICMP sockets",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_ping,
		.params = (struct parameter []) {
			{
				.name = "connect",
				.type = PTYPE_BOOLEAN,
				.desc = "call connect(2) with the socket",
				.defv.boolean = true,
			},
			{
				.name = "bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind(2) with the socket",
				.defv.boolean = true,
			},
			{
				.name = "id",
				.type = PTYPE_INTEGER,
				.desc = "ICMP echo request id",
				.defv.integer = 0,
			},
			PARAM_END
		}
	},
	{
		.name = "tcp6",
		.desc = "AF_INET6+SOCK_STREAM sockets",
		.priv = false,
		.N    = 3,
		.EX_N = 0,
		.make = make_tcp6,
		.params = (struct parameter []) {
			{
				.name = "server-port",
				.type = PTYPE_INTEGER,
				.desc = "TCP port the server may listen",
				.defv.integer = 12345,
			},
			{
				.name = "client-port",
				.type = PTYPE_INTEGER,
				.desc = "TCP port the client may bind",
				.defv.integer = 23456,
			},
			PARAM_END
		}
	},
	{
		.name = "udp6",
		.desc = "AF_INET6+SOCK_DGRAM sockets",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.make = make_udp6,
		.params = (struct parameter []) {
			{
				.name = "lite",
				.type = PTYPE_BOOLEAN,
				.desc = "Use UDPLITE instead of UDP",
				.defv.boolean = false,
			},
			{
				.name = "server-port",
				.type = PTYPE_INTEGER,
				.desc = "UDP port the server may listen",
				.defv.integer = 12345,
			},
			{
				.name = "client-port",
				.type = PTYPE_INTEGER,
				.desc = "UDP port the client may bind",
				.defv.integer = 23456,
			},
			{
				.name = "server-do-bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind with the server socket",
				.defv.boolean = true,
			},
			{
				.name = "client-do-bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind with the client socket",
				.defv.boolean = true,
			},
			{
				.name = "client-do-connect",
				.type = PTYPE_BOOLEAN,
				.desc = "call connect with the client socket",
				.defv.boolean = true,
			},
			PARAM_END
		}
	},
	{
		.name = "raw6",
		.desc = "AF_INET6+SOCK_RAW sockets",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.make = make_raw6,
		.params = (struct parameter []) {
			{
				.name = "protocol",
				.type = PTYPE_INTEGER,
				.desc = "protocol passed to socket(AF_INET6, SOCK_RAW, protocol)",
				.defv.integer = IPPROTO_IPIP,
			},
			PARAM_END
		}

	},
	{
		.name = "ping6",
		.desc = "AF_INET6+SOCK_DGRAM+IPPROTO_ICMPV6 sockets",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_ping6,
		.params = (struct parameter []) {
			{
				.name = "connect",
				.type = PTYPE_BOOLEAN,
				.desc = "call connect(2) with the socket",
				.defv.boolean = true,
			},
			{
				.name = "bind",
				.type = PTYPE_BOOLEAN,
				.desc = "call bind(2) with the socket",
				.defv.boolean = true,
			},
			{
				.name = "id",
				.type = PTYPE_INTEGER,
				.desc = "ICMP echo request id",
				.defv.integer = 0,
			},
			PARAM_END
		}
	},
#if HAVE_DECL_VMADDR_CID_LOCAL
	{
		"vsock",
		.desc = "AF_VSOCK sockets",
		.priv = false,
		.N    = 3,	/* NOTE: The 3rd one is not used if socktype is DGRAM. */
		.EX_N = 0,
		.make = make_vsock,
		.params = (struct parameter []) {
			{
				.name = "socktype",
				.type = PTYPE_STRING,
				.desc = "STREAM, DGRAM, or SEQPACKET",
				.defv.string = "STREAM",
			},
			{
				.name = "server-port",
				.type = PTYPE_INTEGER,
				.desc = "VSOCK port the server may listen",
				.defv.integer = 12345,
			},
			{
				.name = "client-port",
				.type = PTYPE_INTEGER,
				.desc = "VSOCK port the client may bind",
				.defv.integer = 23456,
			},
			PARAM_END
		}
	},
#endif	/* HAVE_DECL_VMADDR_CID_LOCAL */
#ifdef SIOCGSKNS
	{
		.name = "netns",
		.desc = "open a file specifying a netns",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.make = make_netns,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
#endif
	{
		.name = "netlink",
		.desc = "AF_NETLINK sockets",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_netlink,
		.params = (struct parameter []) {
			{
				.name = "protocol",
				.type = PTYPE_INTEGER,
				.desc = "protocol passed to socket(AF_NETLINK, SOCK_RAW, protocol)",
				.defv.integer = NETLINK_USERSOCK,
			},
			{
				.name = "groups",
				.type = PTYPE_UINTEGER,
				.desc = "multicast groups of netlink communication (requires CAP_NET_ADMIN)",
				.defv.uinteger = 0,
			},
			PARAM_END
		}
	},
	{
		.name = "eventfd",
		.desc = "make an eventfd connecting two processes",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.EX_O = 1,
		.make = make_eventfd,
		.report = report_eventfd,
		.free = free_eventfd,
		.params = (struct parameter []) {
			PARAM_END
		},
		.o_descs = (const char *[]){
			"the pid of child process",
		},
	},
	{
		.name = "mqueue",
		.desc = "make a mqueue connecting two processes",
		.priv = false,
		.N    = 2,
		.EX_N = 0,
		.EX_O = 1,
		.make = make_mqueue,
		.report = report_mqueue,
		.free = free_mqueue,
		.params = (struct parameter []) {
			{
				.name = "path",
				.type = PTYPE_STRING,
				.desc = "path for mqueue",
				.defv.string = "/test_mkfds-mqueue",
			},
			PARAM_END
		},
		.o_descs = (const char *[]){
			"the pid of the child process",
		},
	},
	{
		.name = "sysvshm",
		.desc = "shared memory mapped with SYSVIPC shmem syscalls",
		.priv = false,
		.N = 0,
		.EX_N = 0,
		.make = make_sysvshm,
		.free = free_sysvshm,
		.params = (struct parameter []) {
			PARAM_END
		},
	},
	{
		.name = "eventpoll",
		.desc = "make eventpoll (epoll) file",
		.priv = false,
		.N    = 3,
		.EX_N = 0,
		.make = make_eventpoll,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
	{
		.name = "timerfd",
		.desc = "make timerfd",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_timerfd,
		.params = (struct parameter []) {
			{
				.name = "clockid",
				.type = PTYPE_STRING,
				.desc = "ID: realtime, monotonic, boottime, realtime-alarm, or boottime-alarm",
				.defv.string = "realtime",
			},
			{
				.name = "abstime",
				.type = PTYPE_BOOLEAN,
				.desc = "use TFD_TIMER_ABSTIME flag",
				.defv.boolean = false,
			},
			{
				.name = "remaining",
				.type = PTYPE_UINTEGER,
				.desc = "remaining seconds for expiration",
				.defv.uinteger = 99,
			},
			{
				.name = "interval",
				.type = PTYPE_UINTEGER,
				.desc = "interval in seconds",
				.defv.uinteger = 10,
			},
			{
				.name = "interval-nanofrac",
				.type = PTYPE_UINTEGER,
				.desc = "nsec part of interval",
				.defv.uinteger = 0,
			},

			PARAM_END
		}
	},
	{
		.name = "signalfd",
		.desc = "make signalfd",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_signalfd,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
	{
		.name = "cdev-tun",
		.desc = "open /dev/net/tun",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.EX_O = 1,
		.make = make_cdev_tun,
		.report = report_cdev_tun,
		.free = free_cdev_tun,
		.params = (struct parameter []) {
			PARAM_END
		},
		.o_descs = (const char *[]){
			"the network device name",
		},
	},
	{
		.name = "bpf-prog",
		.desc = "make bpf-prog",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.EX_O = 2,
		.make = make_bpf_prog,
		.report = report_bpf_prog,
		.free = free_bpf_prog,
		.params = (struct parameter []) {
			{
				.name = "prog-type-id",
				.type = PTYPE_INTEGER,
				.desc = "program type by id",
				.defv.integer = 1,
			},
			{
				.name = "name",
				.type = PTYPE_STRING,
				.desc = "name assigned to bpf prog object",
				.defv.string = "mkfds_bpf_prog",
			},
			PARAM_END
		},
		.o_descs = (const char *[]) {
			[RITEM_BPF_PROG_ID]  = "the id of bpf prog object",
			[RITEM_BPF_PROG_TAG] = "the tag of bpf prog object",
		},
	},
	{
		.name = "multiplexing",
		.desc = "make pipes monitored by multiplexers",
		.priv =  false,
		.N    = 12,
		.EX_N = 0,
		.make = make_some_pipes,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
	{
		.name = "bpf-map",
		.desc = "make bpf-map",
		.priv = true,
		.N    = 1,
		.EX_N = 0,
		.make = make_bpf_map,
		.params = (struct parameter []) {
			{
				.name = "map-type-id",
				.type = PTYPE_INTEGER,
				.desc = "map type by id",
				.defv.integer = 1,
			},
			{
				.name = "name",
				.type = PTYPE_STRING,
				.desc = "name assigned to the bpf map object",
				.defv.string = "mkfds_bpf_map",
			},
			PARAM_END
		}
	},
	{
		.name = "pty",
		.desc = "make a pair of ptmx and pts",
		.priv = false,
		.N = 2,
		.EX_N = 0,
		.EX_O = 1,
		.make = make_pty,
		.report = report_pty,
		.free = free_pty,
		.params = (struct parameter []) {
			PARAM_END
		},
		.o_descs = (const char *[]){
			"the index of the slave device",
		},
	},
	{
		.name = "mmap",
		.desc = "do mmap the given file",
		.priv = false,
		.N    = 0,
		.EX_N = 0,
		.make = make_mmap,
		.free = free_mmap,
		.params = (struct parameter []) {
			{
				.name = "file",
				.type = PTYPE_STRING,
				.desc = "file to be opened",
				.defv.string = "/etc/passwd",
			},
			PARAM_END
		},
	},
	{
		.name = "userns",
		.desc = "open a user namespae",
		.priv = false,
		.N    = 1,
		.EX_N = 0,
		.make = make_userns,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
	{
		.name = "sockdiag",
		.desc = "make a sockdiag netlink socket",
		.priv = false,
		.N = 1,
		.EX_N = 0,
		.make = make_sockdiag,
		.params = (struct parameter []) {
			{
				.name = "type",
				.type = PTYPE_STRING,
				.desc = "dgram or raw",
				.defv.string = "dgram",
			},
			{
				.name = "family",
				.type = PTYPE_STRING,
				/* TODO: inet, inet6 */
				.desc = "name of a protocol family ([unix]|vsock)",
				.defv.string = "unix",
			},
			PARAM_END
		}
	},
	{
		.name = "foreign-sockets",
		.desc = "import sockets made in a foreign network namespaec",
		.priv = true,
		.N = 2,
		.EX_N = 0,
		.EX_O = 1,
		.make = make_foreign_sockets,
		.report = report_foreign_sockets,
		.free = free_foreign_sockets,
		.params = (struct parameter []) {
			PARAM_END
		}
	},
};

static int count_parameters(const struct factory *factory)
{

	const struct parameter *p = factory->params;
	if (!p)
		return 0;
	while (p->name)
		p++;
	return p - factory->params;
}

static void print_factory(const struct factory *factory)
{
	printf("%-20s %4s %5d %7d %6d %s\n",
	       factory->name,
	       factory->priv? "yes": "no",
	       factory->N,
	       factory->EX_O + 1,
	       count_parameters(factory),
	       factory->desc);
}

static void list_factories(void)
{
	printf("%-20s PRIV COUNT NRETURN NPARAM DESCRIPTION\n", "FACTORY");
	for (size_t i = 0; i < ARRAY_SIZE(factories); i++)
		print_factory(factories + i);
}

static const struct factory *find_factory(const char *name)
{
	for (size_t i = 0; i < ARRAY_SIZE(factories); i++)
		if (strcmp(factories[i].name, name) == 0)
			return factories + i;
	return NULL;
}

static void list_parameters(const char *factory_name)
{
	const struct factory *factory = find_factory(factory_name);
	const char *fmt = "%-15s %-8s %15s %s\n";

	if (!factory)
		errx(EXIT_FAILURE, "no such factory: %s", factory_name);

	if (!factory->params)
		return;

	printf(fmt, "PARAMETER", "TYPE", "DEFAULT_VALUE", "DESCRIPTION");
	for (const struct parameter *p = factory->params; p->name != NULL; p++) {
		char *defv = ptype_classes[p->type].sprint(&p->defv);
		printf(fmt, p->name, ptype_classes[p->type].name, defv, p->desc);
		free(defv);
	}
}

static void list_output_values(const char *factory_name)
{
	const struct factory *factory = find_factory(factory_name);
	const char *fmt = "%3d %s\n";
	const char **o;

	if (!factory)
		errx(EXIT_FAILURE, "no such factory: %s", factory_name);

	printf("%-3s %s\n", "NTH", "DESCRIPTION");
	printf(fmt, 0, "the pid owning the file descriptor(s)");

	o  = factory->o_descs;
	if (!o)
		return;
	for (int i = 0; i < factory->EX_O; i++)
		printf(fmt, i + 1, o[i]);
}

static void rename_self(const char *comm)
{
	if (prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0) < 0)
		err(EXIT_FAILURE, "failed to rename self via prctl: %s", comm);
}

static void do_nothing(int signum _U_)
{
}

/*
 * Multiplexers
 */
struct multiplexer {
	const char *name;
	void (*fn)(bool, struct fdesc *fdescs, size_t n_fdescs);
};

#if defined(__NR_select) || defined(__NR_poll)
static void sighandler_nop(int si _U_)
{
   /* Do nothing */
}
#endif

#define DEFUN_WAIT_EVENT_SELECT(NAME,SYSCALL,XDECLS,SETUP_SIG_HANDLER,SYSCALL_INVOCATION) \
	static void wait_event_##NAME(bool add_stdin, struct fdesc *fdescs, size_t n_fdescs) \
	{								\
		fd_set readfds;						\
		fd_set writefds;					\
		fd_set exceptfds;					\
		XDECLS							\
		int n = 0;						\
									\
		FD_ZERO(&readfds);					\
		FD_ZERO(&writefds);					\
		FD_ZERO(&exceptfds);					\
		/* Monitor the standard input only when the process	\
		 * is in foreground. */					\
		if (add_stdin) {					\
			n = 1;						\
			FD_SET(0, &readfds);				\
		}							\
									\
		for (size_t i = 0; i < n_fdescs; i++) {			\
			if (fdescs[i].mx_modes & MX_READ) {		\
				n = max(n, fdescs[i].fd + 1);		\
				FD_SET(fdescs[i].fd, &readfds);		\
			}						\
			if (fdescs[i].mx_modes & MX_WRITE) {		\
				n = max(n, fdescs[i].fd + 1);		\
				FD_SET(fdescs[i].fd, &writefds);	\
			}						\
			if (fdescs[i].mx_modes & MX_EXCEPT) {		\
				n = max(n, fdescs[i].fd + 1);		\
				FD_SET(fdescs[i].fd, &exceptfds);	\
			}						\
		}							\
									\
		SETUP_SIG_HANDLER					\
									\
		if (SYSCALL_INVOCATION < 0				\
		    && errno != EINTR)					\
			err(EXIT_FAILURE, "failed in " SYSCALL);	\
	}

DEFUN_WAIT_EVENT_SELECT(default,
			"pselect",
			sigset_t sigset;,
			sigemptyset(&sigset);,
			pselect(n, &readfds, &writefds, &exceptfds, NULL, &sigset))

#ifdef __NR_pselect6
DEFUN_WAIT_EVENT_SELECT(pselect6,
			"pselect6",
			sigset_t sigset;,
			sigemptyset(&sigset);,
			syscall(__NR_pselect6, n, &readfds, &writefds, &exceptfds, NULL, &sigset))
#endif

#ifdef __NR_select
DEFUN_WAIT_EVENT_SELECT(select,
			"select",
			,
			signal(SIGCONT,sighandler_nop);,
			syscall(__NR_select, n, &readfds, &writefds, &exceptfds, NULL))
#endif

#ifdef __NR_poll
static DEFUN_WAIT_EVENT_POLL(poll,
		      "poll",
		      ,
		      signal(SIGCONT,sighandler_nop);,
		      syscall(__NR_poll, pfds, n, -1))
#endif

#define DEFAULT_MULTIPLEXER 0
static struct multiplexer multiplexers [] = {
	{
		.name = "default",
		.fn = wait_event_default,
	},
#ifdef __NR_pselect6
	{
		.name = "pselect6",
		.fn = wait_event_pselect6,
	},
#endif
#ifdef __NR_select
	{
		.name = "select",
		.fn = wait_event_select,
	},
#endif
#ifdef __NR_poll
	{
		.name = "poll",
		.fn = wait_event_poll,
	},
#endif
#ifdef HAVE_SIGSET_T
#ifdef __NR_ppoll
	{
		.name = "ppoll",
		.fn = wait_event_ppoll,
	},
#endif
#endif	/* HAVE_SIGSET_T */
};

static struct multiplexer *lookup_multiplexer(const char *name)
{
	for (size_t i = 0; i < ARRAY_SIZE(multiplexers); i++)
		if (strcmp(name, multiplexers[i].name) == 0)
			return multiplexers + i;
	return NULL;
}

static void list_multiplexers(void)
{
	puts("NAME");
	for (size_t i = 0; i < ARRAY_SIZE(multiplexers); i++)
		puts(multiplexers[i].name);
}

static bool is_available(const char *factory)
{
	for (size_t i = 0; i < ARRAY_SIZE(factories); i++)
		if (strcmp(factories[i].name, factory) == 0)
			return true;

	return false;
}

int main(int argc, char **argv)
{
	int c;
	const struct factory *factory;
	struct fdesc fdescs[MAX_N];
	bool quiet = false;
	bool cont  = false;
	void *data;
	bool monitor_stdin = true;

	struct multiplexer *wait_event = NULL;

	static const struct option longopts[] = {
		{ "is-available",required_argument,NULL, 'a' },
		{ "list",	no_argument, NULL, 'l' },
		{ "parameters", required_argument, NULL, 'I' },
		{ "output-values", required_argument, NULL, 'O' },
		{ "comm",       required_argument, NULL, 'r' },
		{ "quiet",	no_argument, NULL, 'q' },
		{ "dont-monitor-stdin", no_argument, NULL, 'X' },
		{ "dont-pause", no_argument, NULL, 'c' },
		{ "wait-with",  required_argument, NULL, 'w' },
		{ "multiplexers",no_argument,NULL, 'W' },
		{ "help",	no_argument, NULL, 'h' },
		{ NULL, 0, NULL, 0 },
	};

	while ((c = getopt_long(argc, argv, "a:lhqcI:O:r:w:WX", longopts, NULL)) != -1) {
		switch (c) {
		case 'h':
			usage(stdout, EXIT_SUCCESS);
		case 'a':
			exit(is_available(optarg)? 0: 1);
		case 'l':
			list_factories();
			exit(EXIT_SUCCESS);
		case 'I':
			list_parameters(optarg);
			exit(EXIT_SUCCESS);
		case 'O':
			list_output_values(optarg);
			exit(EXIT_SUCCESS);
		case 'q':
			quiet = true;
			break;
		case 'c':
			cont = true;
			break;
		case 'w':
			wait_event = lookup_multiplexer(optarg);
			if (wait_event == NULL)
				errx(EXIT_FAILURE, "unknown multiplexer: %s", optarg);
			break;
		case 'W':
			list_multiplexers();
			exit(EXIT_SUCCESS);
		case 'r':
			rename_self(optarg);
			break;
		case 'X':
			monitor_stdin = false;
			break;
		default:
			usage(stderr, EXIT_FAILURE);
		}
	}

	if (optind == argc)
		errx(EXIT_FAILURE, "no file descriptor specification given");

	if (cont && wait_event)
		errx(EXIT_FAILURE, "don't specify both -c/--dont-puase and -w/--wait-with options");
	if (wait_event == NULL)
		wait_event = multiplexers + DEFAULT_MULTIPLEXER;

	factory = find_factory(argv[optind]);
	if (!factory)
		errx(EXIT_FAILURE, "no such factory: %s", argv[optind]);
	assert(factory->N + factory->EX_N < MAX_N);
	optind++;

	if ((optind + factory->N) > argc)
		errx(EXIT_FAILURE, "not enough file descriptors given for %s",
		     factory->name);

	if (factory->priv && getuid() != 0)
		errx(EXIT_FAILURE, "%s factory requires root privilege", factory->name);

	for (int i = 0; i < MAX_N; i++) {
		fdescs[i].fd = -1;
		fdescs[i].mx_modes = 0;
		fdescs[i].close = NULL;
	}

	for (int i = 0; i < factory->N; i++) {
		char *str = argv[optind + i];
		long fd;
		char *ep;

		errno = 0;
		fd = strtol(str, &ep, 10);
		if (errno)
			err(EXIT_FAILURE, "failed to convert fd number: %s", str);
		if (ep == str)
			errx(EXIT_FAILURE, "failed to convert fd number: %s", str);
		if (*ep != '\0')
			errx(EXIT_FAILURE, "garbage at the end of number: %s", str);
		if (fd < 0)
			errx(EXIT_FAILURE, "fd number should not be negative: %s", str);
		if (fd < 3)
			errx(EXIT_FAILURE, "fd 0, 1, 2 are reserved: %s", str);
		if (fd > INT_MAX)
			errx(EXIT_FAILURE, "too large fd number for INT: %s", str);

		reserve_fd(fd);
		fdescs[i].fd = fd;
	}
	optind += factory->N;

	data = factory->make(factory, fdescs, argc - optind, argv + optind);

	signal(SIGCONT, do_nothing);

	if (!quiet) {
		printf("%d", getpid());
		if (factory->report) {
			for (int i = 0; i < factory->EX_O; i++) {
				putchar(' ');
				factory->report(factory, i, data, stdout);
			}
		}
		putchar('\n');
		fflush(stdout);
	}

	if (!cont)
		wait_event->fn(monitor_stdin,
			       fdescs, factory->N + factory->EX_N);

	for (int i = 0; i < factory->N + factory->EX_N; i++)
		if (fdescs[i].fd >= 0 && fdescs[i].close)
			fdescs[i].close(fdescs[i].fd, fdescs[i].data);

	if (factory->free)
		factory->free(factory, data);

	exit(EXIT_SUCCESS);
}
