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Tidy up the terminal detection and feature code and add named sets of
terminal features, each of which are defined in one place and map to a
builtin set of terminfo(5) capabilities. Features can be specified based
on TERM with a new terminal-features option or with the -T flag when
running tmux. tmux will also detect a few common terminals from the DA
and DSR responses.

This is intended to make it easier to configure tmux's use of
terminfo(5) even in the presence of outdated ncurses(3) or terminfo(5)
databases or for features which do not yet have a terminfo(5) entry.
Instead of having to grok terminfo(5) capability names and what they
should be set to in the terminal-overrides option, the user can
hopefully just give tmux a feature name and let it do the right thing.

The terminal-overrides option remains both for backwards compatibility
and to allow tweaks of individual capabilities.

tmux already did much of this already, this makes it tidier and simpler
to configure.

/* $OpenBSD: client.c,v 1.142 2020/04/20 13:25:36 nicm Exp $ */

/*
 * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
 *
 * 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/socket.h>
#include <sys/un.h>
#include <sys/wait.h>

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

#include "tmux.h"

static struct tmuxproc	*client_proc;
static struct tmuxpeer	*client_peer;
static int		 client_flags;
static 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;
static int		 client_exitflag;
static int		 client_exitval;
static enum msgtype	 client_exittype;
static const char	*client_exitsession;
static const char	*client_execshell;
static const char	*client_execcmd;
static int		 client_attached;
static struct client_files client_files = RB_INITIALIZER(&client_files);

static __dead void	 client_exec(const char *,const char *);
static int		 client_get_lock(char *);
static int		 client_connect(struct event_base *, const char *, int);
static void		 client_send_identify(const char *, const char *, int);
static void		 client_signal(int);
static void		 client_dispatch(struct imsg *, void *);
static void		 client_dispatch_attached(struct imsg *);
static void		 client_dispatch_wait(struct imsg *);
static 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 -2 to
 * retry. Return -1 on failure to continue and start the server anyway.
 */
static int
client_get_lock(char *lockfile)
{
	int lockfd;

	log_debug("lock file is %s", lockfile);

	if ((lockfd = open(lockfile, O_WRONLY|O_CREAT, 0600)) == -1) {
		log_debug("open failed: %s", strerror(errno));
		return (-1);
	}

	if (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
		log_debug("flock failed: %s", strerror(errno));
		if (errno != EAGAIN)
			return (lockfd);
		while (flock(lockfd, LOCK_EX) == -1 && errno == EINTR)
			/* nothing */;
		close(lockfd);
		return (-2);
	}
	log_debug("flock succeeded");

	return (lockfd);
}

/* Connect client to server. */
static int
client_connect(struct event_base *base, const char *path, int flags)
{
	struct sockaddr_un	sa;
	size_t			size;
	int			fd, lockfd = -1, locked = 0;
	char		       *lockfile = NULL;

	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);
	}
	log_debug("socket is %s", path);

retry:
	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
		return (-1);

	log_debug("trying connect");
	if (connect(fd, (struct sockaddr *)&sa, sizeof sa) == -1) {
		log_debug("connect failed: %s", strerror(errno));
		if (errno != ECONNREFUSED && errno != ENOENT)
			goto failed;
		if (~flags & CLIENT_STARTSERVER)
			goto failed;
		close(fd);

		if (!locked) {
			xasprintf(&lockfile, "%s.lock", path);
			if ((lockfd = client_get_lock(lockfile)) < 0) {
				log_debug("didn't get lock (%d)", lockfd);

				free(lockfile);
				lockfile = NULL;

				if (lockfd == -2)
					goto retry;
			}
			log_debug("got lock (%d)", lockfd);

			/*
			 * Always retry at least once, even if we got the lock,
			 * because another client could have taken the lock,
			 * started the server and released the lock between our
			 * connect() and flock().
			 */
			locked = 1;
			goto retry;
		}

		if (lockfd >= 0 && unlink(path) != 0 && errno != ENOENT) {
			free(lockfile);
			close(lockfd);
			return (-1);
		}
		fd = server_start(client_proc, flags, base, lockfd, lockfile);
	}

	if (locked && lockfd >= 0) {
		free(lockfile);
		close(lockfd);
	}
	setblocking(fd, 0);
	return (fd);

failed:
	if (locked) {
		free(lockfile);
		close(lockfd);
	}
	close(fd);
	return (-1);
}

/* Get exit string from reason number. */
const char *
client_exit_message(void)
{
	static char msg[256];

	switch (client_exitreason) {
	case CLIENT_EXIT_NONE:
		break;
	case CLIENT_EXIT_DETACHED:
		if (client_exitsession != NULL) {
			xsnprintf(msg, sizeof msg, "detached "
			    "(from session %s)", client_exitsession);
			return (msg);
		}
		return ("detached");
	case CLIENT_EXIT_DETACHED_HUP:
		if (client_exitsession != NULL) {
			xsnprintf(msg, sizeof msg, "detached and SIGHUP "
			    "(from session %s)", client_exitsession);
			return (msg);
		}
		return ("detached and SIGHUP");
	case CLIENT_EXIT_LOST_TTY:
		return ("lost tty");
	case CLIENT_EXIT_TERMINATED:
		return ("terminated");
	case CLIENT_EXIT_LOST_SERVER:
		return ("server exited unexpectedly");
	case CLIENT_EXIT_EXITED:
		return ("exited");
	case CLIENT_EXIT_SERVER_EXITED:
		return ("server exited");
	}
	return ("unknown reason");
}

/* Exit if all streams flushed. */
static void
client_exit(void)
{
	struct client_file	*cf;
	size_t 			 left;
	int			 waiting = 0;

	RB_FOREACH (cf, client_files, &client_files) {
		if (cf->event == NULL)
			continue;
		left = EVBUFFER_LENGTH(cf->event->output);
		if (left != 0) {
			waiting++;
			log_debug("file %u %zu bytes left", cf->stream, left);
		}
	}
	if (waiting == 0)
		proc_exit(client_proc);
}

/* Client main loop. */
int
client_main(struct event_base *base, int argc, char **argv, int flags, int feat)
{
	struct cmd_parse_result	*pr;
	struct msg_command	*data;
	int			 fd, i;
	const char		*ttynam, *cwd;
	pid_t			 ppid;
	enum msgtype		 msg;
	struct termios		 tio, saved_tio;
	size_t			 size;

	/* Ignore SIGCHLD now or daemon() in the server will leave a zombie. */
	signal(SIGCHLD, SIG_IGN);

	/* Set up the initial command. */
	if (shell_command != NULL) {
		msg = MSG_SHELL;
		flags |= CLIENT_STARTSERVER;
	} else if (argc == 0) {
		msg = MSG_COMMAND;
		flags |= CLIENT_STARTSERVER;
	} 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.
		 */
		pr = cmd_parse_from_arguments(argc, argv, NULL);
		if (pr->status == CMD_PARSE_SUCCESS) {
			if (cmd_list_any_have(pr->cmdlist, CMD_STARTSERVER))
				flags |= CLIENT_STARTSERVER;
			cmd_list_free(pr->cmdlist);
		} else
			free(pr->error);
	}

	/* Save the flags. */
	client_flags = flags;

	/* Create client process structure (starts logging). */
	client_proc = proc_start("client");
	proc_set_signals(client_proc, client_signal);

	/* Initialize the client socket and start the server. */
	fd = client_connect(base, socket_path, client_flags);
	if (fd == -1) {
		if (errno == ECONNREFUSED) {
			fprintf(stderr, "no server running on %s\n",
			    socket_path);
		} else {
			fprintf(stderr, "error connecting to %s (%s)\n",
			    socket_path, strerror(errno));
		}
		return (1);
	}
	client_peer = proc_add_peer(client_proc, fd, client_dispatch, NULL);

	/* Save these before pledge(). */
	if ((cwd = find_cwd()) == NULL && (cwd = find_home()) == NULL)
		cwd = "/";
	if ((ttynam = ttyname(STDIN_FILENO)) == NULL)
		ttynam = "";

	/*
	 * Drop privileges for client. "proc exec" is needed for -c and for
	 * locking (which uses system(3)).
	 *
	 * "tty" is needed to restore termios(4) and also for some reason -CC
	 * does not work properly without it (input is not recognised).
	 *
	 * "sendfd" is dropped later in client_dispatch_wait().
	 */
	if (pledge(
	    "stdio rpath wpath cpath unix sendfd proc exec tty",
	    NULL) != 0)
		fatal("pledge failed");

	/* Free stuff that is not used in the client. */
	if (ptm_fd != -1)
		close(ptm_fd);
	options_free(global_options);
	options_free(global_s_options);
	options_free(global_w_options);
	environ_free(global_environ);

	/* Set up control mode. */
	if (client_flags & CLIENT_CONTROLCONTROL) {
		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);
	}

	/* Send identify messages. */
	client_send_identify(ttynam, cwd, feat);

	/* Send first command. */
	if (msg == MSG_COMMAND) {
		/* How big is the command? */
		size = 0;
		for (i = 0; i < argc; i++)
			size += strlen(argv[i]) + 1;
		if (size > MAX_IMSGSIZE - (sizeof *data)) {
			fprintf(stderr, "command too long\n");
			return (1);
		}
		data = xmalloc((sizeof *data) + size);

		/* Prepare command for server. */
		data->argc = argc;
		if (cmd_pack_argv(argc, argv, (char *)(data + 1), size) != 0) {
			fprintf(stderr, "command too long\n");
			free(data);
			return (1);
		}
		size += sizeof *data;

		/* Send the command. */
		if (proc_send(client_peer, msg, -1, data, size) != 0) {
			fprintf(stderr, "failed to send command\n");
			free(data);
			return (1);
		}
		free(data);
	} else if (msg == MSG_SHELL)
		proc_send(client_peer, msg, -1, NULL, 0);

	/* Start main loop. */
	proc_loop(client_proc, NULL);

	/* Run command if user requested exec, instead of exiting. */
	if (client_exittype == MSG_EXEC) {
		if (client_flags & CLIENT_CONTROLCONTROL)
			tcsetattr(STDOUT_FILENO, TCSAFLUSH, &saved_tio);
		client_exec(client_execshell, client_execcmd);
	}

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

		ppid = getppid();
		if (client_exittype == MSG_DETACHKILL && ppid > 1)
			kill(ppid, SIGHUP);
	} else if (client_flags & CLIENT_CONTROLCONTROL) {
		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);
	} else if (client_exitreason != CLIENT_EXIT_NONE)
		fprintf(stderr, "%s\n", client_exit_message());
	setblocking(STDIN_FILENO, 1);
	return (client_exitval);
}

/* Send identify messages to server. */
static void
client_send_identify(const char *ttynam, const char *cwd, int feat)
{
	const char	 *s;
	char		**ss;
	size_t		  sslen;
	int		  fd, flags = client_flags;
	pid_t		  pid;

	proc_send(client_peer, MSG_IDENTIFY_FLAGS, -1, &flags, sizeof flags);

	if ((s = getenv("TERM")) == NULL)
		s = "";
	proc_send(client_peer, MSG_IDENTIFY_TERM, -1, s, strlen(s) + 1);
	proc_send(client_peer, MSG_IDENTIFY_FEATURES, -1, &feat, sizeof feat);

	proc_send(client_peer, MSG_IDENTIFY_TTYNAME, -1, ttynam,
	    strlen(ttynam) + 1);
	proc_send(client_peer, MSG_IDENTIFY_CWD, -1, cwd, strlen(cwd) + 1);

	if ((fd = dup(STDIN_FILENO)) == -1)
		fatal("dup failed");
	proc_send(client_peer, MSG_IDENTIFY_STDIN, fd, NULL, 0);

	pid = getpid();
	proc_send(client_peer, MSG_IDENTIFY_CLIENTPID, -1, &pid, sizeof pid);

	for (ss = environ; *ss != NULL; ss++) {
		sslen = strlen(*ss) + 1;
		if (sslen > MAX_IMSGSIZE - IMSG_HEADER_SIZE)
			continue;
		proc_send(client_peer, MSG_IDENTIFY_ENVIRON, -1, *ss, sslen);
	}

	proc_send(client_peer, MSG_IDENTIFY_DONE, -1, NULL, 0);
}

/* File write error callback. */
static void
client_write_error_callback(__unused struct bufferevent *bev,
    __unused short what, void *arg)
{
	struct client_file	*cf = arg;

	log_debug("write error file %d", cf->stream);

	bufferevent_free(cf->event);
	cf->event = NULL;

	close(cf->fd);
	cf->fd = -1;

	if (client_exitflag)
		client_exit();
}

/* File write callback. */
static void
client_write_callback(__unused struct bufferevent *bev, void *arg)
{
	struct client_file	*cf = arg;

	if (cf->closed && EVBUFFER_LENGTH(cf->event->output) == 0) {
		bufferevent_free(cf->event);
		close(cf->fd);
		RB_REMOVE(client_files, &client_files, cf);
		file_free(cf);
	}

	if (client_exitflag)
		client_exit();
}

/* Open write file. */
static void
client_write_open(void *data, size_t datalen)
{
	struct msg_write_open	*msg = data;
	const char		*path;
	struct msg_write_ready	 reply;
	struct client_file	 find, *cf;
	const int		 flags = O_NONBLOCK|O_WRONLY|O_CREAT;
	int			 error = 0;

	if (datalen < sizeof *msg)
		fatalx("bad MSG_WRITE_OPEN size");
	if (datalen == sizeof *msg)
		path = "-";
	else
		path = (const char *)(msg + 1);
	log_debug("open write file %d %s", msg->stream, path);

	find.stream = msg->stream;
	if ((cf = RB_FIND(client_files, &client_files, &find)) == NULL) {
		cf = file_create(NULL, msg->stream, NULL, NULL);
		RB_INSERT(client_files, &client_files, cf);
	} else {
		error = EBADF;
		goto reply;
	}
	if (cf->closed) {
		error = EBADF;
		goto reply;
	}

	cf->fd = -1;
	if (msg->fd == -1)
		cf->fd = open(path, msg->flags|flags, 0644);
	else {
		if (msg->fd != STDOUT_FILENO && msg->fd != STDERR_FILENO)
			errno = EBADF;
		else {
			cf->fd = dup(msg->fd);
			if (client_flags & CLIENT_CONTROL)
				close(msg->fd); /* can only be used once */
		}
	}
	if (cf->fd == -1) {
		error = errno;
		goto reply;
	}

	cf->event = bufferevent_new(cf->fd, NULL, client_write_callback,
	    client_write_error_callback, cf);
	bufferevent_enable(cf->event, EV_WRITE);
	goto reply;

reply:
	reply.stream = msg->stream;
	reply.error = error;
	proc_send(client_peer, MSG_WRITE_READY, -1, &reply, sizeof reply);
}

/* Write to client file. */
static void
client_write_data(void *data, size_t datalen)
{
	struct msg_write_data	*msg = data;
	struct client_file	 find, *cf;
	size_t			 size = datalen - sizeof *msg;

	if (datalen < sizeof *msg)
		fatalx("bad MSG_WRITE size");
	find.stream = msg->stream;
	if ((cf = RB_FIND(client_files, &client_files, &find)) == NULL)
		fatalx("unknown stream number");
	log_debug("write %zu to file %d", size, cf->stream);

	if (cf->event != NULL)
		bufferevent_write(cf->event, msg + 1, size);
}

/* Close client file. */
static void
client_write_close(void *data, size_t datalen)
{
	struct msg_write_close	*msg = data;
	struct client_file	 find, *cf;

	if (datalen != sizeof *msg)
		fatalx("bad MSG_WRITE_CLOSE size");
	find.stream = msg->stream;
	if ((cf = RB_FIND(client_files, &client_files, &find)) == NULL)
		fatalx("unknown stream number");
	log_debug("close file %d", cf->stream);

	if (cf->event == NULL || EVBUFFER_LENGTH(cf->event->output) == 0) {
		if (cf->event != NULL)
			bufferevent_free(cf->event);
		if (cf->fd != -1)
			close(cf->fd);
		RB_REMOVE(client_files, &client_files, cf);
		file_free(cf);
	}
}

/* File read callback. */
static void
client_read_callback(__unused struct bufferevent *bev, void *arg)
{
	struct client_file	*cf = arg;
	void			*bdata;
	size_t			 bsize;
	struct msg_read_data	*msg;
	size_t			 msglen;

	msg = xmalloc(sizeof *msg);
	for (;;) {
		bdata = EVBUFFER_DATA(cf->event->input);
		bsize = EVBUFFER_LENGTH(cf->event->input);

		if (bsize == 0)
			break;
		if (bsize > MAX_IMSGSIZE - IMSG_HEADER_SIZE - sizeof *msg)
			bsize = MAX_IMSGSIZE - IMSG_HEADER_SIZE - sizeof *msg;
		log_debug("read %zu from file %d", bsize, cf->stream);

		msglen = (sizeof *msg) + bsize;
		msg = xrealloc(msg, msglen);
		msg->stream = cf->stream;
		memcpy(msg + 1, bdata, bsize);
		proc_send(client_peer, MSG_READ, -1, msg, msglen);

		evbuffer_drain(cf->event->input, bsize);
	}
	free(msg);
}

/* File read error callback. */
static void
client_read_error_callback(__unused struct bufferevent *bev,
    __unused short what, void *arg)
{
	struct client_file	*cf = arg;
	struct msg_read_done	 msg;

	log_debug("read error file %d", cf->stream);

	msg.stream = cf->stream;
	msg.error = 0;
	proc_send(client_peer, MSG_READ_DONE, -1, &msg, sizeof msg);

	bufferevent_free(cf->event);
	close(cf->fd);
	RB_REMOVE(client_files, &client_files, cf);
	file_free(cf);
}

/* Open read file. */
static void
client_read_open(void *data, size_t datalen)
{
	struct msg_read_open	*msg = data;
	const char		*path;
	struct msg_read_done	 reply;
	struct client_file	 find, *cf;
	const int		 flags = O_NONBLOCK|O_RDONLY;
	int			 error;

	if (datalen < sizeof *msg)
		fatalx("bad MSG_READ_OPEN size");
	if (datalen == sizeof *msg)
		path = "-";
	else
		path = (const char *)(msg + 1);
	log_debug("open read file %d %s", msg->stream, path);

	find.stream = msg->stream;
	if ((cf = RB_FIND(client_files, &client_files, &find)) == NULL) {
		cf = file_create(NULL, msg->stream, NULL, NULL);
		RB_INSERT(client_files, &client_files, cf);
	} else {
		error = EBADF;
		goto reply;
	}
	if (cf->closed) {
		error = EBADF;
		goto reply;
	}

	cf->fd = -1;
	if (msg->fd == -1)
		cf->fd = open(path, flags);
	else {
		if (msg->fd != STDIN_FILENO)
			errno = EBADF;
		else {
			cf->fd = dup(msg->fd);
			close(msg->fd); /* can only be used once */
		}
	}
	if (cf->fd == -1) {
		error = errno;
		goto reply;
	}

	cf->event = bufferevent_new(cf->fd, client_read_callback, NULL,
	    client_read_error_callback, cf);
	bufferevent_enable(cf->event, EV_READ);
	return;

reply:
	reply.stream = msg->stream;
	reply.error = error;
	proc_send(client_peer, MSG_READ_DONE, -1, &reply, sizeof reply);
}

/* Run command in shell; used for -c. */
static __dead void
client_exec(const char *shell, const char *shellcmd)
{
	const char	*name, *ptr;
	char		*argv0;

	log_debug("shell %s, command %s", shell, shellcmd);

	ptr = strrchr(shell, '/');
	if (ptr != NULL && *(ptr + 1) != '\0')
		name = ptr + 1;
	else
		name = shell;
	if (client_flags & CLIENT_LOGIN)
		xasprintf(&argv0, "-%s", name);
	else
		xasprintf(&argv0, "%s", name);
	setenv("SHELL", shell, 1);

	proc_clear_signals(client_proc, 1);

	setblocking(STDIN_FILENO, 1);
	setblocking(STDOUT_FILENO, 1);
	setblocking(STDERR_FILENO, 1);
	closefrom(STDERR_FILENO + 1);

	execl(shell, argv0, "-c", shellcmd, (char *) NULL);
	fatal("execl failed");
}

/* Callback to handle signals in the client. */
static void
client_signal(int sig)
{
	struct sigaction sigact;
	int		 status;

	if (sig == SIGCHLD)
		waitpid(WAIT_ANY, &status, WNOHANG);
	else if (!client_attached) {
		if (sig == SIGTERM)
			proc_exit(client_proc);
	} else {
		switch (sig) {
		case SIGHUP:
			client_exitreason = CLIENT_EXIT_LOST_TTY;
			client_exitval = 1;
			proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
			break;
		case SIGTERM:
			client_exitreason = CLIENT_EXIT_TERMINATED;
			client_exitval = 1;
			proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
			break;
		case SIGWINCH:
			proc_send(client_peer, MSG_RESIZE, -1, 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");
			proc_send(client_peer, MSG_WAKEUP, -1, NULL, 0);
			break;
		}
	}
}

/* Callback for client read events. */
static void
client_dispatch(struct imsg *imsg, __unused void *arg)
{
	if (imsg == NULL) {
		client_exitreason = CLIENT_EXIT_LOST_SERVER;
		client_exitval = 1;
		proc_exit(client_proc);
		return;
	}

	if (client_attached)
		client_dispatch_attached(imsg);
	else
		client_dispatch_wait(imsg);
}

/* Dispatch imsgs when in wait state (before MSG_READY). */
static void
client_dispatch_wait(struct imsg *imsg)
{
	char		*data;
	ssize_t		 datalen;
	int		 retval;
	static int	 pledge_applied;

	/*
	 * "sendfd" is no longer required once all of the identify messages
	 * have been sent. We know the server won't send us anything until that
	 * point (because we don't ask it to), so we can drop "sendfd" once we
	 * get the first message from the server.
	 */
	if (!pledge_applied) {
		if (pledge(
		    "stdio rpath wpath cpath unix proc exec tty",
		    NULL) != 0)
			fatal("pledge failed");
		pledge_applied = 1;
	}

	data = imsg->data;
	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;

	switch (imsg->hdr.type) {
	case MSG_EXIT:
	case MSG_SHUTDOWN:
		if (datalen != sizeof retval && datalen != 0)
			fatalx("bad MSG_EXIT size");
		if (datalen == sizeof retval) {
			memcpy(&retval, data, sizeof retval);
			client_exitval = retval;
		}
		client_exitflag = 1;
		client_exit();
		break;
	case MSG_READY:
		if (datalen != 0)
			fatalx("bad MSG_READY size");

		client_attached = 1;
		proc_send(client_peer, MSG_RESIZE, -1, NULL, 0);
		break;
	case MSG_VERSION:
		if (datalen != 0)
			fatalx("bad MSG_VERSION size");

		fprintf(stderr, "protocol version mismatch "
		    "(client %d, server %u)\n", PROTOCOL_VERSION,
		    imsg->hdr.peerid & 0xff);
		client_exitval = 1;
		proc_exit(client_proc);
		break;
	case MSG_SHELL:
		if (datalen == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_SHELL string");

		client_exec(data, shell_command);
		/* NOTREACHED */
	case MSG_DETACH:
	case MSG_DETACHKILL:
		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		break;
	case MSG_EXITED:
		proc_exit(client_proc);
		break;
	case MSG_READ_OPEN:
		client_read_open(data, datalen);
		break;
	case MSG_WRITE_OPEN:
		client_write_open(data, datalen);
		break;
	case MSG_WRITE:
		client_write_data(data, datalen);
		break;
	case MSG_WRITE_CLOSE:
		client_write_close(data, datalen);
		break;
	case MSG_OLDSTDERR:
	case MSG_OLDSTDIN:
	case MSG_OLDSTDOUT:
		fprintf(stderr, "server version is too old for client\n");
		proc_exit(client_proc);
		break;
	}
}

/* Dispatch imsgs in attached state (after MSG_READY). */
static void
client_dispatch_attached(struct imsg *imsg)
{
	struct sigaction	 sigact;
	char			*data;
	ssize_t			 datalen;

	data = imsg->data;
	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;

	switch (imsg->hdr.type) {
	case MSG_DETACH:
	case MSG_DETACHKILL:
		if (datalen == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_DETACH string");

		client_exitsession = xstrdup(data);
		client_exittype = imsg->hdr.type;
		if (imsg->hdr.type == MSG_DETACHKILL)
			client_exitreason = CLIENT_EXIT_DETACHED_HUP;
		else
			client_exitreason = CLIENT_EXIT_DETACHED;
		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		break;
	case MSG_EXEC:
		if (datalen == 0 || data[datalen - 1] != '\0' ||
		    strlen(data) + 1 == (size_t)datalen)
			fatalx("bad MSG_EXEC string");
		client_execcmd = xstrdup(data);
		client_execshell = xstrdup(data + strlen(data) + 1);

		client_exittype = imsg->hdr.type;
		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		break;
	case MSG_EXIT:
		if (datalen != 0 && datalen != sizeof (int))
			fatalx("bad MSG_EXIT size");

		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		client_exitreason = CLIENT_EXIT_EXITED;
		break;
	case MSG_EXITED:
		if (datalen != 0)
			fatalx("bad MSG_EXITED size");

		proc_exit(client_proc);
		break;
	case MSG_SHUTDOWN:
		if (datalen != 0)
			fatalx("bad MSG_SHUTDOWN size");

		proc_send(client_peer, MSG_EXITING, -1, 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 == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_LOCK string");

		system(data);
		proc_send(client_peer, MSG_UNLOCK, -1, NULL, 0);
		break;
	}
}