Tweak previous - find end of style correctly.

[tmux-openbsd.git] / client.c

/* $OpenBSD$ */

/*
 * 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/uio.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 uint64_t          client_flags;
static int               client_suspended;
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_EXIT_MESSAGE_PROVIDED
} client_exitreason = CLIENT_EXIT_NONE;
static int               client_exitflag;
static int               client_exitval;
static enum msgtype      client_exittype;
static const char       *client_exitsession;
static char             *client_exitmessage;
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 *,
                             uint64_t);
static void              client_send_identify(const char *, const char *,
                             char **, u_int, 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, uint64_t 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_NOSTARTSERVER)
                        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");
        case CLIENT_EXIT_MESSAGE_PROVIDED:
                return (client_exitmessage);
        }
        return ("unknown reason");
}

/* Exit if all streams flushed. */
static void
client_exit(void)
{
        if (!file_write_left(&client_files))
                proc_exit(client_proc);
}

/* Client main loop. */
int
client_main(struct event_base *base, int argc, char **argv, uint64_t flags,
    int feat)
{
        struct cmd_parse_result *pr;
        struct msg_command      *data;
        int                      fd, i;
        const char              *ttynam, *termname, *cwd;
        pid_t                    ppid;
        enum msgtype             msg;
        struct termios           tio, saved_tio;
        size_t                   size, linesize = 0;
        ssize_t                  linelen;
        char                    *line = NULL, **caps = NULL, *cause;
        u_int                    ncaps = 0;
        struct args_value       *values;

        /* 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's annoying parsing the command string twice (in client
                 * and later in server) but it is necessary to get the start
                 * server flag.
                 */
                values = args_from_vector(argc, argv);
                pr = cmd_parse_from_arguments(values, argc, 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);
                args_free_values(values, argc);
                free(values);
        }

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

        /* Save the flags. */
        client_flags = flags;
        log_debug("flags are %#llx", (unsigned long long)client_flags);

        /* 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 = "";
        if ((termname = getenv("TERM")) == NULL)
                termname = "";

        /*
         * 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");

        /* Load terminfo entry if any. */
        if (isatty(STDIN_FILENO) &&
            *termname != '\0' &&
            tty_term_read_list(termname, STDIN_FILENO, &caps, &ncaps,
            &cause) != 0) {
                fprintf(stderr, "%s\n", cause);
                free(cause);
                return (1);
        }

        /* 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, termname, caps, ncaps, cwd, feat);
        tty_term_free_list(caps, ncaps);
        proc_flush_peer(client_peer);

        /* 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);
        }

        /* Restore streams to blocking. */
        setblocking(STDIN_FILENO, 1);
        setblocking(STDOUT_FILENO, 1);
        setblocking(STDERR_FILENO, 1);

        /* 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_CONTROL) {
                if (client_exitreason != CLIENT_EXIT_NONE)
                        printf("%%exit %s\n", client_exit_message());
                else
                        printf("%%exit\n");
                fflush(stdout);
                if (client_flags & CLIENT_CONTROL_WAITEXIT) {
                        setvbuf(stdin, NULL, _IOLBF, 0);
                        for (;;) {
                                linelen = getline(&line, &linesize, stdin);
                                if (linelen <= 1)
                                        break;
                        }
                        free(line);
                }
                if (client_flags & CLIENT_CONTROLCONTROL) {
                        printf("\033\\");
                        fflush(stdout);
                        tcsetattr(STDOUT_FILENO, TCSAFLUSH, &saved_tio);
                }
        } else if (client_exitreason != CLIENT_EXIT_NONE)
                fprintf(stderr, "%s\n", client_exit_message());
        return (client_exitval);
}

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

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

        proc_send(client_peer, MSG_IDENTIFY_TERM, -1, termname,
            strlen(termname) + 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);

        for (i = 0; i < ncaps; i++) {
                proc_send(client_peer, MSG_IDENTIFY_TERMINFO, -1,
                    caps[i], strlen(caps[i]) + 1);
        }

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

/* 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;

        log_debug("%s: %s", __func__, strsignal(sig));
        if (sig == SIGCHLD)
                waitpid(WAIT_ANY, &status, WNOHANG);
        else if (!client_attached) {
                if (sig == SIGTERM || sig == SIGHUP)
                        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:
                        if (!client_suspended)
                                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);
                        client_suspended = 0;
                        break;
                }
        }
}

/* Callback for file write error or close. */
static void
client_file_check_cb(__unused struct client *c, __unused const char *path,
    __unused int error, __unused int closed, __unused struct evbuffer *buffer,
    __unused void *data)
{
        if (client_exitflag)
                client_exit();
}

/* Callback for client read events. */
static void
client_dispatch(struct imsg *imsg, __unused void *arg)
{
        if (imsg == NULL) {
                if (!client_exitflag) {
                        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);
}

/* Process an exit message. */
static void
client_dispatch_exit_message(char *data, size_t datalen)
{
        int     retval;

        if (datalen < sizeof retval && datalen != 0)
                fatalx("bad MSG_EXIT size");

        if (datalen >= sizeof retval) {
                memcpy(&retval, data, sizeof retval);
                client_exitval = retval;
        }

        if (datalen > sizeof retval) {
                datalen -= sizeof retval;
                data += sizeof retval;

                client_exitmessage = xmalloc(datalen);
                memcpy(client_exitmessage, data, datalen);
                client_exitmessage[datalen - 1] = '\0';

                client_exitreason = CLIENT_EXIT_MESSAGE_PROVIDED;
        }
}

/* Dispatch imsgs when in wait state (before MSG_READY). */
static void
client_dispatch_wait(struct imsg *imsg)
{
        char            *data;
        ssize_t          datalen;
        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:
                client_dispatch_exit_message(data, datalen);
                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_FLAGS:
                if (datalen != sizeof client_flags)
                        fatalx("bad MSG_FLAGS string");

                memcpy(&client_flags, data, sizeof client_flags);
                log_debug("new flags are %#llx",
                    (unsigned long long)client_flags);
                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:
                file_read_open(&client_files, client_peer, imsg, 1,
                    !(client_flags & CLIENT_CONTROL), client_file_check_cb,
                    NULL);
                break;
        case MSG_WRITE_OPEN:
                file_write_open(&client_files, client_peer, imsg, 1,
                    !(client_flags & CLIENT_CONTROL), client_file_check_cb,
                    NULL);
                break;
        case MSG_WRITE:
                file_write_data(&client_files, imsg);
                break;
        case MSG_WRITE_CLOSE:
                file_write_close(&client_files, imsg);
                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_FLAGS:
                if (datalen != sizeof client_flags)
                        fatalx("bad MSG_FLAGS string");

                memcpy(&client_flags, data, sizeof client_flags);
                log_debug("new flags are %#llx",
                    (unsigned long long)client_flags);
                break;
        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:
                client_dispatch_exit_message(data, datalen);
                if (client_exitreason == CLIENT_EXIT_NONE)
                        client_exitreason = CLIENT_EXIT_EXITED;
                proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
                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");
                client_suspended = 1;
                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;
        }
}