client.c - tmux - Rivoreo Source Code Repositories

 /* $OpenBSD$ */

 /*
  * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
  * copyright notice and this permission notice appear in all copies.
  *
  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
  * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */

 #include <sys/types.h>
 #include <sys/file.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/un.h>
 #include <sys/wait.h>

 #include <errno.h>
 #include <event.h>
 #include <fcntl.h>
 #include <pwd.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>

 #include "tmux.h"

 struct imsgbuf	client_ibuf;
 struct event	client_event;
 struct event	client_stdin;
 enum {
 	CLIENT_EXIT_NONE,
 	CLIENT_EXIT_DETACHED,
 	CLIENT_EXIT_DETACHED_HUP,
 	CLIENT_EXIT_LOST_TTY,
 	CLIENT_EXIT_TERMINATED,
 	CLIENT_EXIT_LOST_SERVER,
 	CLIENT_EXIT_EXITED,
 	CLIENT_EXIT_SERVER_EXITED,
 } client_exitreason = CLIENT_EXIT_NONE;
 int		client_exitval;
 enum msgtype	client_exittype;
 int		client_attached;

 int		client_get_lock(char *);
 int		client_connect(char *, int);
 void		client_send_identify(int);
 void		client_send_environ(void);
 void		client_write_server(enum msgtype, void *, size_t);
 void		client_update_event(void);
 void		client_signal(int, short, void *);
 void		client_stdin_callback(int, short, void *);
 void		client_write(int, const char *, size_t);
 void		client_callback(int, short, void *);
 int		client_dispatch_attached(void);
 int		client_dispatch_wait(void *);
 const char     *client_exit_message(void);

 /*
  * Get server create lock. If already held then server start is happening in
  * another client, so block until the lock is released and return -1 to
  * retry. Ignore other errors - just continue and start the server without the
  * lock.
  */
 int
 client_get_lock(char *lockfile)
 {
 	int lockfd;

 	if ((lockfd = open(lockfile, O_WRONLY|O_CREAT, 0600)) == -1)
 		fatal("open failed");

 	if (lockf(lockfd, F_TLOCK, 0) == -1 && errno == EAGAIN) {
 		while (lockf(lockfd, F_LOCK, 0) == -1 && errno == EINTR)
 			/* nothing */;
 		close(lockfd);
 		return (-1);
 	}

 	return (lockfd);
 }

 /* Connect client to server. */
 int
 client_connect(char *path, int start_server)
 {
 	struct sockaddr_un	sa;
 	size_t			size;
 	int			fd, lockfd;
 	char		       *lockfile;

 	memset(&sa, 0, sizeof sa);
 	sa.sun_family = AF_UNIX;
 	size = strlcpy(sa.sun_path, path, sizeof sa.sun_path);
 	if (size >= sizeof sa.sun_path) {
 		errno = ENAMETOOLONG;
 		return (-1);
 	}

 retry:
 	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
 		fatal("socket failed");

 	if (connect(fd, (struct sockaddr *) &sa, SUN_LEN(&sa)) == -1) {
 		if (errno != ECONNREFUSED && errno != ENOENT)
 			goto failed;
 		if (!start_server)
 			goto failed;
 		close(fd);

 		xasprintf(&lockfile, "%s.lock", path);
 		if ((lockfd = client_get_lock(lockfile)) == -1)
 			goto retry;
 		if (unlink(path) != 0 && errno != ENOENT)
 			return (-1);
 		fd = server_start(lockfd, lockfile);
 		free(lockfile);
 		close(lockfd);
 	}

 	setblocking(fd, 0);
 	return (fd);

 failed:
 	close(fd);
 	return (-1);
 }

 /* Get exit string from reason number. */
 const char *
 client_exit_message(void)
 {
 	switch (client_exitreason) {
 	case CLIENT_EXIT_NONE:
 		break;
 	case CLIENT_EXIT_DETACHED:
 		return ("detached");
 	case CLIENT_EXIT_DETACHED_HUP:
 		return ("detached and SIGHUP");
 	case CLIENT_EXIT_LOST_TTY:
 		return ("lost tty");
 	case CLIENT_EXIT_TERMINATED:
 		return ("terminated");
 	case CLIENT_EXIT_LOST_SERVER:
 		return ("lost server");
 	case CLIENT_EXIT_EXITED:
 		return ("exited");
 	case CLIENT_EXIT_SERVER_EXITED:
 		return ("server exited");
 	}
 	return ("unknown reason");
 }

 /* Client main loop. */
 int
 client_main(int argc, char **argv, int flags)
 {
 	struct cmd		*cmd;
 	struct cmd_list		*cmdlist;
 	struct msg_command_data	 cmddata;
 	int			 cmdflags, fd;
 	pid_t			 ppid;
 	enum msgtype		 msg;
 	char			*cause;
 	struct termios		 tio, saved_tio;

 	/* Set up the initial command. */
 	cmdflags = 0;
 	if (shell_cmd != NULL) {
 		msg = MSG_SHELL;
 		cmdflags = CMD_STARTSERVER;
 	} else if (argc == 0) {
 		msg = MSG_COMMAND;
 		cmdflags = CMD_STARTSERVER|CMD_SENDENVIRON|CMD_CANTNEST;
 	} else {
 		msg = MSG_COMMAND;

 		/*
 		 * It sucks parsing the command string twice (in client and
 		 * later in server) but it is necessary to get the start server
 		 * flag.
 		 */
 		cmdlist = cmd_list_parse(argc, argv, NULL, 0, &cause);
 		if (cmdlist == NULL) {
 			fprintf(stderr, "%s\n", cause);
 			return (1);
 		}
 		cmdflags &= ~CMD_STARTSERVER;
 		TAILQ_FOREACH(cmd, &cmdlist->list, qentry) {
 			if (cmd->entry->flags & CMD_STARTSERVER)
 				cmdflags |= CMD_STARTSERVER;
 			if (cmd->entry->flags & CMD_SENDENVIRON)
 				cmdflags |= CMD_SENDENVIRON;
 			if (cmd->entry->flags & CMD_CANTNEST)
 				cmdflags |= CMD_CANTNEST;
 		}
 		cmd_list_free(cmdlist);
 	}

 	/*
 	 * Check if this could be a nested session, if the command can't nest:
 	 * if the socket path matches $TMUX, this is probably the same server.
 	 */
 	if (shell_cmd == NULL && environ_path != NULL &&
 	    (cmdflags & CMD_CANTNEST) &&
 	    strcmp(socket_path, environ_path) == 0) {
 		fprintf(stderr, "sessions should be nested with care, "
 		    "unset $TMUX to force\n");
 		return (1);
 	}

 	/* Initialise the client socket and start the server. */
 	fd = client_connect(socket_path, cmdflags & CMD_STARTSERVER);
 	if (fd == -1) {
 		fprintf(stderr, "failed to connect to server\n");
 		return (1);
 	}

 	/* Set process title, log and signals now this is the client. */
 	setproctitle("client (%s)", socket_path);
 	logfile("client");

 	/* Create imsg. */
 	imsg_init(&client_ibuf, fd);
 	event_set(&client_event, fd, EV_READ, client_callback, shell_cmd);

 	/* Create stdin handler. */
 	setblocking(STDIN_FILENO, 0);
 	event_set(&client_stdin, STDIN_FILENO, EV_READ|EV_PERSIST,
 	    client_stdin_callback, NULL);
 	if (flags & IDENTIFY_TERMIOS) {
 		if (tcgetattr(STDIN_FILENO, &saved_tio) != 0) {
 			fprintf(stderr, "tcgetattr failed: %s\n",
 			    strerror(errno));
 			return (1);
 		}
 		cfmakeraw(&tio);
 		tio.c_iflag = ICRNL|IXANY;
 		tio.c_oflag = OPOST|ONLCR;
 		tio.c_lflag = NOKERNINFO;
 		tio.c_cflag = CREAD|CS8|HUPCL;
 		tio.c_cc[VMIN] = 1;
 		tio.c_cc[VTIME] = 0;
 		cfsetispeed(&tio, cfgetispeed(&saved_tio));
 		cfsetospeed(&tio, cfgetospeed(&saved_tio));
 		tcsetattr(STDIN_FILENO, TCSANOW, &tio);
 	}

 	/* Establish signal handlers. */
 	set_signals(client_signal);

 	/* Send initial environment. */
 	if (cmdflags & CMD_SENDENVIRON)
 		client_send_environ();
 	client_send_identify(flags);

 	/* Send first command. */
 	if (msg == MSG_COMMAND) {
 		/* Fill in command line arguments. */
 		cmddata.pid = environ_pid;
 		cmddata.session_id = environ_session_id;

 		/* Prepare command for server. */
 		cmddata.argc = argc;
 		if (cmd_pack_argv(
 		    argc, argv, cmddata.argv, sizeof cmddata.argv) != 0) {
 			fprintf(stderr, "command too long\n");
 			return (1);
 		}

 		client_write_server(msg, &cmddata, sizeof cmddata);
 	} else if (msg == MSG_SHELL)
 		client_write_server(msg, NULL, 0);

 	/* Set the event and dispatch. */
 	client_update_event();
 	event_dispatch();

 	/* Print the exit message, if any, and exit. */
 	if (client_attached) {
 		if (client_exitreason != CLIENT_EXIT_NONE && !login_shell)
 			printf("[%s]\n", client_exit_message());

 		ppid = getppid();
 		if (client_exittype == MSG_DETACHKILL && ppid > 1)
 			kill(ppid, SIGHUP);
 	} else if (flags & IDENTIFY_TERMIOS) {
 		if (flags & IDENTIFY_CONTROL) {
 			if (client_exitreason != CLIENT_EXIT_NONE)
 			    printf("%%exit %s\n", client_exit_message());
 			else
 			    printf("%%exit\n");
 			printf("\033\\");
 		}
 		tcsetattr(STDOUT_FILENO, TCSAFLUSH, &saved_tio);
 	}
 	setblocking(STDIN_FILENO, 1);
 	return (client_exitval);
 }

 /* Send identify message to server with the file descriptors. */
 void
 client_send_identify(int flags)
 {
 	struct msg_identify_data	data;
 	char			       *term;
 	int				fd;

 	data.flags = flags;

 	if (getcwd(data.cwd, sizeof data.cwd) == NULL)
 		*data.cwd = '\0';

 	term = getenv("TERM");
 	if (term == NULL ||
 	    strlcpy(data.term, term, sizeof data.term) >= sizeof data.term)
 		*data.term = '\0';

 	if ((fd = dup(STDIN_FILENO)) == -1)
 		fatal("dup failed");
 	imsg_compose(&client_ibuf,
 	    MSG_IDENTIFY, PROTOCOL_VERSION, -1, fd, &data, sizeof data);
 	client_update_event();
 }

 /* Forward entire environment to server. */
 void
 client_send_environ(void)
 {
 	struct msg_environ_data	data;
 	char		      **var;

 	for (var = environ; *var != NULL; var++) {
 		if (strlcpy(data.var, *var, sizeof data.var) >= sizeof data.var)
 			continue;
 		client_write_server(MSG_ENVIRON, &data, sizeof data);
 	}
 }

 /* Write a message to the server without a file descriptor. */
 void
 client_write_server(enum msgtype type, void *buf, size_t len)
 {
 	imsg_compose(&client_ibuf, type, PROTOCOL_VERSION, -1, -1, buf, len);
 	client_update_event();
 }

 /* Update client event based on whether it needs to read or read and write. */
 void
 client_update_event(void)
 {
 	short	events;

 	event_del(&client_event);
 	events = EV_READ;
 	if (client_ibuf.w.queued > 0)
 		events |= EV_WRITE;
 	event_set(
 	    &client_event, client_ibuf.fd, events, client_callback, shell_cmd);
 	event_add(&client_event, NULL);
 }

 /* Callback to handle signals in the client. */
 void
 client_signal(int sig, unused short events, unused void *data)
 {
 	struct sigaction sigact;
 	int		 status;

 	if (!client_attached) {
 		switch (sig) {
 		case SIGCHLD:
 			waitpid(WAIT_ANY, &status, WNOHANG);
 			break;
 		case SIGTERM:
 			event_loopexit(NULL);
 			break;
 		}
 	} else {
 		switch (sig) {
 		case SIGHUP:
 			client_exitreason = CLIENT_EXIT_LOST_TTY;
 			client_exitval = 1;
 			client_write_server(MSG_EXITING, NULL, 0);
 			break;
 		case SIGTERM:
 			client_exitreason = CLIENT_EXIT_TERMINATED;
 			client_exitval = 1;
 			client_write_server(MSG_EXITING, NULL, 0);
 			break;
 		case SIGWINCH:
 			client_write_server(MSG_RESIZE, NULL, 0);
 			break;
 		case SIGCONT:
 			memset(&sigact, 0, sizeof sigact);
 			sigemptyset(&sigact.sa_mask);
 			sigact.sa_flags = SA_RESTART;
 			sigact.sa_handler = SIG_IGN;
 			if (sigaction(SIGTSTP, &sigact, NULL) != 0)
 				fatal("sigaction failed");
 			client_write_server(MSG_WAKEUP, NULL, 0);
 			break;
 		}
 	}

 	client_update_event();
 }

 /* Callback for client imsg read events. */
 void
 client_callback(unused int fd, short events, void *data)
 {
 	ssize_t	n;
 	int	retval;

 	if (events & EV_READ) {
 		if ((n = imsg_read(&client_ibuf)) == -1 || n == 0)
 			goto lost_server;
 		if (client_attached)
 			retval = client_dispatch_attached();
 		else
 			retval = client_dispatch_wait(data);
 		if (retval != 0) {
 			event_loopexit(NULL);
 			return;
 		}
 	}

 	if (events & EV_WRITE) {
 		if (msgbuf_write(&client_ibuf.w) < 0)
 			goto lost_server;
 	}

 	client_update_event();
 	return;

 lost_server:
 	client_exitreason = CLIENT_EXIT_LOST_SERVER;
 	client_exitval = 1;
 	event_loopexit(NULL);
 }

 /* Callback for client stdin read events. */
 void
 client_stdin_callback(unused int fd, unused short events, unused void *data1)
 {
 	struct msg_stdin_data	data;

 	data.size = read(STDIN_FILENO, data.data, sizeof data.data);
 	if (data.size < 0 && (errno == EINTR || errno == EAGAIN))
 		return;

 	client_write_server(MSG_STDIN, &data, sizeof data);
 	if (data.size <= 0)
 		event_del(&client_stdin);
 	client_update_event();
 }

 /* Force write to file descriptor. */
 void
 client_write(int fd, const char *data, size_t size)
 {
 	ssize_t	used;

 	while (size != 0) {
 		used = write(fd, data, size);
 		if (used == -1) {
 			if (errno == EINTR || errno == EAGAIN)
 				continue;
 			break;
 		}
 		data += used;
 		size -= used;
 	}
 }

 /* Dispatch imsgs when in wait state (before MSG_READY). */
 int
 client_dispatch_wait(void *data)
 {
 	struct imsg		imsg;
 	ssize_t			n, datalen;
 	struct msg_shell_data	shelldata;
 	struct msg_exit_data	exitdata;
 	struct msg_stdout_data	stdoutdata;
 	struct msg_stderr_data	stderrdata;
 	const char             *shellcmd = data;

 	for (;;) {
 		if ((n = imsg_get(&client_ibuf, &imsg)) == -1)
 			fatalx("imsg_get failed");
 		if (n == 0)
 			return (0);
 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;

 		log_debug("got %d from server", imsg.hdr.type);
 		switch (imsg.hdr.type) {
 		case MSG_EXIT:
 		case MSG_SHUTDOWN:
 			if (datalen != sizeof exitdata) {
 				if (datalen != 0)
 					fatalx("bad MSG_EXIT size");
 			} else {
 				memcpy(&exitdata, imsg.data, sizeof exitdata);
 				client_exitval = exitdata.retcode;
 			}
 			imsg_free(&imsg);
 			return (-1);
 		case MSG_READY:
 			if (datalen != 0)
 				fatalx("bad MSG_READY size");

 			event_del(&client_stdin);
 			client_attached = 1;
 			client_write_server(MSG_RESIZE, NULL, 0);
 			break;
 		case MSG_STDIN:
 			if (datalen != 0)
 				fatalx("bad MSG_STDIN size");

 			event_add(&client_stdin, NULL);
 			break;
 		case MSG_STDOUT:
 			if (datalen != sizeof stdoutdata)
 				fatalx("bad MSG_STDOUT");
 			memcpy(&stdoutdata, imsg.data, sizeof stdoutdata);

 			client_write(STDOUT_FILENO, stdoutdata.data, stdoutdata.size);
 			break;
 		case MSG_STDERR:
 			if (datalen != sizeof stderrdata)
 				fatalx("bad MSG_STDERR");
 			memcpy(&stderrdata, imsg.data, sizeof stderrdata);

 			client_write(STDERR_FILENO, stderrdata.data, stderrdata.size);
 			break;
 		case MSG_VERSION:
 			if (datalen != 0)
 				fatalx("bad MSG_VERSION size");

 			fprintf(stderr, "protocol version mismatch "
 			    "(client %u, server %u)\n", PROTOCOL_VERSION,
 			    imsg.hdr.peerid);
 			client_exitval = 1;

 			imsg_free(&imsg);
 			return (-1);
 		case MSG_SHELL:
 			if (datalen != sizeof shelldata)
 				fatalx("bad MSG_SHELL size");
 			memcpy(&shelldata, imsg.data, sizeof shelldata);
 			shelldata.shell[(sizeof shelldata.shell) - 1] = '\0';

 			clear_signals(0);

 			shell_exec(shelldata.shell, shellcmd);
 			/* NOTREACHED */
 		case MSG_DETACH:
 			client_write_server(MSG_EXITING, NULL, 0);
 			break;
 		case MSG_EXITED:
 			imsg_free(&imsg);
 			return (-1);
 		default:
 			fatalx("unexpected message");
 		}

 		imsg_free(&imsg);
 	}
 }

 /* Dispatch imsgs in attached state (after MSG_READY). */
 int
 client_dispatch_attached(void)
 {
 	struct imsg		imsg;
 	struct msg_lock_data	lockdata;
 	struct sigaction	sigact;
 	ssize_t			n, datalen;

 	for (;;) {
 		if ((n = imsg_get(&client_ibuf, &imsg)) == -1)
 			fatalx("imsg_get failed");
 		if (n == 0)
 			return (0);
 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;

 		log_debug("got %d from server", imsg.hdr.type);
 		switch (imsg.hdr.type) {
 		case MSG_DETACHKILL:
 		case MSG_DETACH:
 			if (datalen != 0)
 				fatalx("bad MSG_DETACH size");

 			client_exittype = imsg.hdr.type;
 			if (imsg.hdr.type == MSG_DETACHKILL)
 				client_exitreason = CLIENT_EXIT_DETACHED_HUP;
 			else
 				client_exitreason = CLIENT_EXIT_DETACHED;
 			client_write_server(MSG_EXITING, NULL, 0);
 			break;
 		case MSG_EXIT:
 			if (datalen != 0 &&
 			    datalen != sizeof (struct msg_exit_data))
 				fatalx("bad MSG_EXIT size");

 			client_write_server(MSG_EXITING, NULL, 0);
 			client_exitreason = CLIENT_EXIT_EXITED;
 			break;
 		case MSG_EXITED:
 			if (datalen != 0)
 				fatalx("bad MSG_EXITED size");

 			imsg_free(&imsg);
 			return (-1);
 		case MSG_SHUTDOWN:
 			if (datalen != 0)
 				fatalx("bad MSG_SHUTDOWN size");

 			client_write_server(MSG_EXITING, NULL, 0);
 			client_exitreason = CLIENT_EXIT_SERVER_EXITED;
 			client_exitval = 1;
 			break;
 		case MSG_SUSPEND:
 			if (datalen != 0)
 				fatalx("bad MSG_SUSPEND size");

 			memset(&sigact, 0, sizeof sigact);
 			sigemptyset(&sigact.sa_mask);
 			sigact.sa_flags = SA_RESTART;
 			sigact.sa_handler = SIG_DFL;
 			if (sigaction(SIGTSTP, &sigact, NULL) != 0)
 				fatal("sigaction failed");
 			kill(getpid(), SIGTSTP);
 			break;
 		case MSG_LOCK:
 			if (datalen != sizeof lockdata)
 				fatalx("bad MSG_LOCK size");
 			memcpy(&lockdata, imsg.data, sizeof lockdata);

 			lockdata.cmd[(sizeof lockdata.cmd) - 1] = '\0';
 			system(lockdata.cmd);
 			client_write_server(MSG_UNLOCK, NULL, 0);
 			break;
 		default:
 			fatalx("unexpected message");
 		}

 		imsg_free(&imsg);
 	}
 }
	/* $OpenBSD$ */

	/*
	* Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
	*
	* Permission to use, copy, modify, and distribute this software for any
	* purpose with or without fee is hereby granted, provided that the above
	* copyright notice and this permission notice appear in all copies.
	*
	* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
	* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
	* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
	* WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
	* IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
	* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
	*/

	#include <sys/types.h>
	#include <sys/file.h>
	#include <sys/socket.h>
	#include <sys/stat.h>
	#include <sys/un.h>
	#include <sys/wait.h>

	#include <errno.h>
	#include <event.h>
	#include <fcntl.h>
	#include <pwd.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>

	#include "tmux.h"

	struct imsgbuf client_ibuf;
	struct event client_event;
	struct event client_stdin;
	enum {
	CLIENT_EXIT_NONE,
	CLIENT_EXIT_DETACHED,
	CLIENT_EXIT_DETACHED_HUP,
	CLIENT_EXIT_LOST_TTY,
	CLIENT_EXIT_TERMINATED,
	CLIENT_EXIT_LOST_SERVER,
	CLIENT_EXIT_EXITED,
	CLIENT_EXIT_SERVER_EXITED,
	} client_exitreason = CLIENT_EXIT_NONE;
	int client_exitval;
	enum msgtype client_exittype;
	int client_attached;

	int client_get_lock(char *);
	int client_connect(char *, int);
	void client_send_identify(int);
	void client_send_environ(void);
	void client_write_server(enum msgtype, void *, size_t);
	void client_update_event(void);
	void client_signal(int, short, void *);
	void client_stdin_callback(int, short, void *);
	void client_write(int, const char *, size_t);
	void client_callback(int, short, void *);
	int client_dispatch_attached(void);
	int client_dispatch_wait(void *);
	const char *client_exit_message(void);

	/*
	* Get server create lock. If already held then server start is happening in
	* another client, so block until the lock is released and return -1 to
	* retry. Ignore other errors - just continue and start the server without the
	* lock.
	*/
	int
	client_get_lock(char *lockfile)
	{
	int lockfd;

	if ((lockfd = open(lockfile, O_WRONLY\|O_CREAT, 0600)) == -1)
	fatal("open failed");

	if (lockf(lockfd, F_TLOCK, 0) == -1 && errno == EAGAIN) {
	while (lockf(lockfd, F_LOCK, 0) == -1 && errno == EINTR)
	/* nothing */;
	close(lockfd);
	return (-1);
	}

	return (lockfd);
	}

	/* Connect client to server. */
	int
	client_connect(char *path, int start_server)
	{
	struct sockaddr_un sa;
	size_t size;
	int fd, lockfd;
	char *lockfile;

	memset(&sa, 0, sizeof sa);
	sa.sun_family = AF_UNIX;
	size = strlcpy(sa.sun_path, path, sizeof sa.sun_path);
	if (size >= sizeof sa.sun_path) {
	errno = ENAMETOOLONG;
	return (-1);
	}

	retry:
	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
	fatal("socket failed");

	if (connect(fd, (struct sockaddr *) &sa, SUN_LEN(&sa)) == -1) {
	if (errno != ECONNREFUSED && errno != ENOENT)
	goto failed;
	if (!start_server)
	goto failed;
	close(fd);

	xasprintf(&lockfile, "%s.lock", path);
	if ((lockfd = client_get_lock(lockfile)) == -1)
	goto retry;
	if (unlink(path) != 0 && errno != ENOENT)
	return (-1);
	fd = server_start(lockfd, lockfile);
	free(lockfile);
	close(lockfd);
	}

	setblocking(fd, 0);
	return (fd);

	failed:
	close(fd);
	return (-1);
	}

	/* Get exit string from reason number. */
	const char *
	client_exit_message(void)
	{
	switch (client_exitreason) {
	case CLIENT_EXIT_NONE:
	break;
	case CLIENT_EXIT_DETACHED:
	return ("detached");
	case CLIENT_EXIT_DETACHED_HUP:
	return ("detached and SIGHUP");
	case CLIENT_EXIT_LOST_TTY:
	return ("lost tty");
	case CLIENT_EXIT_TERMINATED:
	return ("terminated");
	case CLIENT_EXIT_LOST_SERVER:
	return ("lost server");
	case CLIENT_EXIT_EXITED:
	return ("exited");
	case CLIENT_EXIT_SERVER_EXITED:
	return ("server exited");
	}
	return ("unknown reason");
	}

	/* Client main loop. */
	int
	client_main(int argc, char **argv, int flags)
	{
	struct cmd *cmd;
	struct cmd_list *cmdlist;
	struct msg_command_data cmddata;
	int cmdflags, fd;
	pid_t ppid;
	enum msgtype msg;
	char *cause;
	struct termios tio, saved_tio;

	/* Set up the initial command. */
	cmdflags = 0;
	if (shell_cmd != NULL) {
	msg = MSG_SHELL;
	cmdflags = CMD_STARTSERVER;
	} else if (argc == 0) {
	msg = MSG_COMMAND;
	cmdflags = CMD_STARTSERVER\|CMD_SENDENVIRON\|CMD_CANTNEST;
	} else {
	msg = MSG_COMMAND;

	/*
	* It sucks parsing the command string twice (in client and
	* later in server) but it is necessary to get the start server
	* flag.
	*/
	cmdlist = cmd_list_parse(argc, argv, NULL, 0, &cause);
	if (cmdlist == NULL) {
	fprintf(stderr, "%s\n", cause);
	return (1);
	}
	cmdflags &= ~CMD_STARTSERVER;
	TAILQ_FOREACH(cmd, &cmdlist->list, qentry) {
	if (cmd->entry->flags & CMD_STARTSERVER)
	cmdflags \|= CMD_STARTSERVER;
	if (cmd->entry->flags & CMD_SENDENVIRON)
	cmdflags \|= CMD_SENDENVIRON;
	if (cmd->entry->flags & CMD_CANTNEST)
	cmdflags \|= CMD_CANTNEST;
	}
	cmd_list_free(cmdlist);
	}

	/*
	* Check if this could be a nested session, if the command can't nest:
	* if the socket path matches $TMUX, this is probably the same server.
	*/
	if (shell_cmd == NULL && environ_path != NULL &&
	(cmdflags & CMD_CANTNEST) &&
	strcmp(socket_path, environ_path) == 0) {
	fprintf(stderr, "sessions should be nested with care, "
	"unset $TMUX to force\n");
	return (1);
	}

	/* Initialise the client socket and start the server. */
	fd = client_connect(socket_path, cmdflags & CMD_STARTSERVER);
	if (fd == -1) {
	fprintf(stderr, "failed to connect to server\n");
	return (1);
	}

	/* Set process title, log and signals now this is the client. */
	setproctitle("client (%s)", socket_path);
	logfile("client");

	/* Create imsg. */
	imsg_init(&client_ibuf, fd);
	event_set(&client_event, fd, EV_READ, client_callback, shell_cmd);

	/* Create stdin handler. */
	setblocking(STDIN_FILENO, 0);
	event_set(&client_stdin, STDIN_FILENO, EV_READ\|EV_PERSIST,
	client_stdin_callback, NULL);
	if (flags & IDENTIFY_TERMIOS) {
	if (tcgetattr(STDIN_FILENO, &saved_tio) != 0) {
	fprintf(stderr, "tcgetattr failed: %s\n",
	strerror(errno));
	return (1);
	}
	cfmakeraw(&tio);
	tio.c_iflag = ICRNL\|IXANY;
	tio.c_oflag = OPOST\|ONLCR;
	tio.c_lflag = NOKERNINFO;
	tio.c_cflag = CREAD\|CS8\|HUPCL;
	tio.c_cc[VMIN] = 1;
	tio.c_cc[VTIME] = 0;
	cfsetispeed(&tio, cfgetispeed(&saved_tio));
	cfsetospeed(&tio, cfgetospeed(&saved_tio));
	tcsetattr(STDIN_FILENO, TCSANOW, &tio);
	}

	/* Establish signal handlers. */
	set_signals(client_signal);

	/* Send initial environment. */
	if (cmdflags & CMD_SENDENVIRON)
	client_send_environ();
	client_send_identify(flags);

	/* Send first command. */
	if (msg == MSG_COMMAND) {
	/* Fill in command line arguments. */
	cmddata.pid = environ_pid;
	cmddata.session_id = environ_session_id;

	/* Prepare command for server. */
	cmddata.argc = argc;
	if (cmd_pack_argv(
	argc, argv, cmddata.argv, sizeof cmddata.argv) != 0) {
	fprintf(stderr, "command too long\n");
	return (1);
	}

	client_write_server(msg, &cmddata, sizeof cmddata);
	} else if (msg == MSG_SHELL)
	client_write_server(msg, NULL, 0);

	/* Set the event and dispatch. */
	client_update_event();
	event_dispatch();

	/* Print the exit message, if any, and exit. */
	if (client_attached) {
	if (client_exitreason != CLIENT_EXIT_NONE && !login_shell)
	printf("[%s]\n", client_exit_message());

	ppid = getppid();
	if (client_exittype == MSG_DETACHKILL && ppid > 1)
	kill(ppid, SIGHUP);
	} else if (flags & IDENTIFY_TERMIOS) {
	if (flags & IDENTIFY_CONTROL) {
	if (client_exitreason != CLIENT_EXIT_NONE)
	printf("%%exit %s\n", client_exit_message());
	else
	printf("%%exit\n");
	printf("\033\\");
	}
	tcsetattr(STDOUT_FILENO, TCSAFLUSH, &saved_tio);
	}
	setblocking(STDIN_FILENO, 1);
	return (client_exitval);
	}

	/* Send identify message to server with the file descriptors. */
	void
	client_send_identify(int flags)
	{
	struct msg_identify_data data;
	char *term;
	int fd;

	data.flags = flags;

	if (getcwd(data.cwd, sizeof data.cwd) == NULL)
	*data.cwd = '\0';

	term = getenv("TERM");
	if (term == NULL \|\|
	strlcpy(data.term, term, sizeof data.term) >= sizeof data.term)
	*data.term = '\0';

	if ((fd = dup(STDIN_FILENO)) == -1)
	fatal("dup failed");
	imsg_compose(&client_ibuf,
	MSG_IDENTIFY, PROTOCOL_VERSION, -1, fd, &data, sizeof data);
	client_update_event();
	}

	/* Forward entire environment to server. */
	void
	client_send_environ(void)
	{
	struct msg_environ_data data;
	char **var;

	for (var = environ; *var != NULL; var++) {
	if (strlcpy(data.var, *var, sizeof data.var) >= sizeof data.var)
	continue;
	client_write_server(MSG_ENVIRON, &data, sizeof data);
	}
	}

	/* Write a message to the server without a file descriptor. */
	void
	client_write_server(enum msgtype type, void *buf, size_t len)
	{
	imsg_compose(&client_ibuf, type, PROTOCOL_VERSION, -1, -1, buf, len);
	client_update_event();
	}

	/* Update client event based on whether it needs to read or read and write. */
	void
	client_update_event(void)
	{
	short events;

	event_del(&client_event);
	events = EV_READ;
	if (client_ibuf.w.queued > 0)
	events \|= EV_WRITE;
	event_set(
	&client_event, client_ibuf.fd, events, client_callback, shell_cmd);
	event_add(&client_event, NULL);
	}

	/* Callback to handle signals in the client. */
	void
	client_signal(int sig, unused short events, unused void *data)
	{
	struct sigaction sigact;
	int status;

	if (!client_attached) {
	switch (sig) {
	case SIGCHLD:
	waitpid(WAIT_ANY, &status, WNOHANG);
	break;
	case SIGTERM:
	event_loopexit(NULL);
	break;
	}
	} else {
	switch (sig) {
	case SIGHUP:
	client_exitreason = CLIENT_EXIT_LOST_TTY;
	client_exitval = 1;
	client_write_server(MSG_EXITING, NULL, 0);
	break;
	case SIGTERM:
	client_exitreason = CLIENT_EXIT_TERMINATED;
	client_exitval = 1;
	client_write_server(MSG_EXITING, NULL, 0);
	break;
	case SIGWINCH:
	client_write_server(MSG_RESIZE, NULL, 0);
	break;
	case SIGCONT:
	memset(&sigact, 0, sizeof sigact);
	sigemptyset(&sigact.sa_mask);
	sigact.sa_flags = SA_RESTART;
	sigact.sa_handler = SIG_IGN;
	if (sigaction(SIGTSTP, &sigact, NULL) != 0)
	fatal("sigaction failed");
	client_write_server(MSG_WAKEUP, NULL, 0);
	break;
	}
	}

	client_update_event();
	}

	/* Callback for client imsg read events. */
	void
	client_callback(unused int fd, short events, void *data)
	{
	ssize_t n;
	int retval;

	if (events & EV_READ) {
	if ((n = imsg_read(&client_ibuf)) == -1 \|\| n == 0)
	goto lost_server;
	if (client_attached)
	retval = client_dispatch_attached();
	else
	retval = client_dispatch_wait(data);
	if (retval != 0) {
	event_loopexit(NULL);
	return;
	}
	}

	if (events & EV_WRITE) {
	if (msgbuf_write(&client_ibuf.w) < 0)
	goto lost_server;
	}

	client_update_event();
	return;

	lost_server:
	client_exitreason = CLIENT_EXIT_LOST_SERVER;
	client_exitval = 1;
	event_loopexit(NULL);
	}

	/* Callback for client stdin read events. */
	void
	client_stdin_callback(unused int fd, unused short events, unused void *data1)
	{
	struct msg_stdin_data data;

	data.size = read(STDIN_FILENO, data.data, sizeof data.data);
	if (data.size < 0 && (errno == EINTR \|\| errno == EAGAIN))
	return;

	client_write_server(MSG_STDIN, &data, sizeof data);
	if (data.size <= 0)
	event_del(&client_stdin);
	client_update_event();
	}

	/* Force write to file descriptor. */
	void
	client_write(int fd, const char *data, size_t size)
	{
	ssize_t used;

	while (size != 0) {
	used = write(fd, data, size);
	if (used == -1) {
	if (errno == EINTR \|\| errno == EAGAIN)
	continue;
	break;
	}
	data += used;
	size -= used;
	}
	}

	/* Dispatch imsgs when in wait state (before MSG_READY). */
	int
	client_dispatch_wait(void *data)
	{
	struct imsg imsg;
	ssize_t n, datalen;
	struct msg_shell_data shelldata;
	struct msg_exit_data exitdata;
	struct msg_stdout_data stdoutdata;
	struct msg_stderr_data stderrdata;
	const char *shellcmd = data;

	for (;;) {
	if ((n = imsg_get(&client_ibuf, &imsg)) == -1)
	fatalx("imsg_get failed");
	if (n == 0)
	return (0);
	datalen = imsg.hdr.len - IMSG_HEADER_SIZE;

	log_debug("got %d from server", imsg.hdr.type);
	switch (imsg.hdr.type) {
	case MSG_EXIT:
	case MSG_SHUTDOWN:
	if (datalen != sizeof exitdata) {
	if (datalen != 0)
	fatalx("bad MSG_EXIT size");
	} else {
	memcpy(&exitdata, imsg.data, sizeof exitdata);
	client_exitval = exitdata.retcode;
	}
	imsg_free(&imsg);
	return (-1);
	case MSG_READY:
	if (datalen != 0)
	fatalx("bad MSG_READY size");

	event_del(&client_stdin);
	client_attached = 1;
	client_write_server(MSG_RESIZE, NULL, 0);
	break;
	case MSG_STDIN:
	if (datalen != 0)
	fatalx("bad MSG_STDIN size");

	event_add(&client_stdin, NULL);
	break;
	case MSG_STDOUT:
	if (datalen != sizeof stdoutdata)
	fatalx("bad MSG_STDOUT");
	memcpy(&stdoutdata, imsg.data, sizeof stdoutdata);

	client_write(STDOUT_FILENO, stdoutdata.data, stdoutdata.size);
	break;
	case MSG_STDERR:
	if (datalen != sizeof stderrdata)
	fatalx("bad MSG_STDERR");
	memcpy(&stderrdata, imsg.data, sizeof stderrdata);

	client_write(STDERR_FILENO, stderrdata.data, stderrdata.size);
	break;
	case MSG_VERSION:
	if (datalen != 0)
	fatalx("bad MSG_VERSION size");

	fprintf(stderr, "protocol version mismatch "
	"(client %u, server %u)\n", PROTOCOL_VERSION,
	imsg.hdr.peerid);
	client_exitval = 1;

	imsg_free(&imsg);
	return (-1);
	case MSG_SHELL:
	if (datalen != sizeof shelldata)
	fatalx("bad MSG_SHELL size");
	memcpy(&shelldata, imsg.data, sizeof shelldata);
	shelldata.shell[(sizeof shelldata.shell) - 1] = '\0';

	clear_signals(0);

	shell_exec(shelldata.shell, shellcmd);
	/* NOTREACHED */
	case MSG_DETACH:
	client_write_server(MSG_EXITING, NULL, 0);
	break;
	case MSG_EXITED:
	imsg_free(&imsg);
	return (-1);
	default:
	fatalx("unexpected message");
	}

	imsg_free(&imsg);
	}
	}

	/* Dispatch imsgs in attached state (after MSG_READY). */
	int
	client_dispatch_attached(void)
	{
	struct imsg imsg;
	struct msg_lock_data lockdata;
	struct sigaction sigact;
	ssize_t n, datalen;

	for (;;) {
	if ((n = imsg_get(&client_ibuf, &imsg)) == -1)
	fatalx("imsg_get failed");
	if (n == 0)
	return (0);
	datalen = imsg.hdr.len - IMSG_HEADER_SIZE;

	log_debug("got %d from server", imsg.hdr.type);
	switch (imsg.hdr.type) {
	case MSG_DETACHKILL:
	case MSG_DETACH:
	if (datalen != 0)
	fatalx("bad MSG_DETACH size");

	client_exittype = imsg.hdr.type;
	if (imsg.hdr.type == MSG_DETACHKILL)
	client_exitreason = CLIENT_EXIT_DETACHED_HUP;
	else
	client_exitreason = CLIENT_EXIT_DETACHED;
	client_write_server(MSG_EXITING, NULL, 0);
	break;
	case MSG_EXIT:
	if (datalen != 0 &&
	datalen != sizeof (struct msg_exit_data))
	fatalx("bad MSG_EXIT size");

	client_write_server(MSG_EXITING, NULL, 0);
	client_exitreason = CLIENT_EXIT_EXITED;
	break;
	case MSG_EXITED:
	if (datalen != 0)
	fatalx("bad MSG_EXITED size");

	imsg_free(&imsg);
	return (-1);
	case MSG_SHUTDOWN:
	if (datalen != 0)
	fatalx("bad MSG_SHUTDOWN size");

	client_write_server(MSG_EXITING, NULL, 0);
	client_exitreason = CLIENT_EXIT_SERVER_EXITED;
	client_exitval = 1;
	break;
	case MSG_SUSPEND:
	if (datalen != 0)
	fatalx("bad MSG_SUSPEND size");

	memset(&sigact, 0, sizeof sigact);
	sigemptyset(&sigact.sa_mask);
	sigact.sa_flags = SA_RESTART;
	sigact.sa_handler = SIG_DFL;
	if (sigaction(SIGTSTP, &sigact, NULL) != 0)
	fatal("sigaction failed");
	kill(getpid(), SIGTSTP);
	break;
	case MSG_LOCK:
	if (datalen != sizeof lockdata)
	fatalx("bad MSG_LOCK size");
	memcpy(&lockdata, imsg.data, sizeof lockdata);

	lockdata.cmd[(sizeof lockdata.cmd) - 1] = '\0';
	system(lockdata.cmd);
	client_write_server(MSG_UNLOCK, NULL, 0);
	break;
	default:
	fatalx("unexpected message");
	}

	imsg_free(&imsg);
	}
	}