[ppp.git] / pppd / main.c

/*
 * main.c - Point-to-Point Protocol main module
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#define RCSID   "$Id: main.c,v 1.92 2000/04/04 07:06:51 paulus Exp $"

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <syslog.h>
#include <netdb.h>
#include <utmp.h>
#include <pwd.h>
#include <setjmp.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "pppd.h"
#include "magic.h"
#include "fsm.h"
#include "lcp.h"
#include "ipcp.h"
#ifdef INET6
#include "ipv6cp.h"
#endif
#include "upap.h"
#include "chap.h"
#include "ccp.h"
#include "pathnames.h"
#include "patchlevel.h"
#include "tdb.h"

#ifdef CBCP_SUPPORT
#include "cbcp.h"
#endif

#ifdef IPX_CHANGE
#include "ipxcp.h"
#endif /* IPX_CHANGE */
#ifdef AT_CHANGE
#include "atcp.h"
#endif

static const char rcsid[] = RCSID;

/* interface vars */
char ifname[32];                /* Interface name */
int ifunit;                     /* Interface unit number */

char *progname;                 /* Name of this program */
char hostname[MAXNAMELEN];      /* Our hostname */
static char pidfilename[MAXPATHLEN];    /* name of pid file */
static char linkpidfile[MAXPATHLEN];    /* name of linkname pid file */
static char ppp_devnam[MAXPATHLEN]; /* name of PPP tty (maybe ttypx) */
static uid_t uid;               /* Our real user-id */
static int conn_running;        /* we have a [dis]connector running */

int ttyfd;                      /* Serial port file descriptor */
mode_t tty_mode = -1;           /* Original access permissions to tty */
int baud_rate;                  /* Actual bits/second for serial device */
int hungup;                     /* terminal has been hung up */
int privileged;                 /* we're running as real uid root */
int need_holdoff;               /* need holdoff period before restarting */
int detached;                   /* have detached from terminal */
struct stat devstat;            /* result of stat() on devnam */
int prepass = 0;                /* doing prepass to find device name */
int devnam_fixed;               /* set while in options.ttyxx file */
volatile int status;            /* exit status for pppd */
int unsuccess;                  /* # unsuccessful connection attempts */
int do_callback;                /* != 0 if we should do callback next */
int doing_callback;             /* != 0 if we are doing callback */
char *callback_script;          /* script for doing callback */
TDB_CONTEXT *pppdb;             /* database for storing status etc. */
char db_key[32];

int (*holdoff_hook) __P((void)) = NULL;
int (*new_phase_hook) __P((int)) = NULL;

static int fd_ppp = -1;         /* fd for talking PPP */
static int fd_loop;             /* fd for getting demand-dial packets */
static int pty_master;          /* fd for master side of pty */
static int pty_slave;           /* fd for slave side of pty */
static int real_ttyfd;          /* fd for actual serial port (not pty) */

int phase;                      /* where the link is at */
int kill_link;
int open_ccp_flag;

static int waiting;
static sigjmp_buf sigjmp;

char **script_env;              /* Env. variable values for scripts */
int s_env_nalloc;               /* # words avail at script_env */

u_char outpacket_buf[PPP_MRU+PPP_HDRLEN]; /* buffer for outgoing packet */
u_char inpacket_buf[PPP_MRU+PPP_HDRLEN]; /* buffer for incoming packet */

static int n_children;          /* # child processes still running */
static int got_sigchld;         /* set if we have received a SIGCHLD */

static int locked;              /* lock() has succeeded */
static int privopen;            /* don't lock, open device as root */

char *no_ppp_msg = "Sorry - this system lacks PPP kernel support\n";

GIDSET_TYPE groups[NGROUPS_MAX];/* groups the user is in */
int ngroups;                    /* How many groups valid in groups */

static struct timeval start_time;       /* Time when link was started. */

struct pppd_stats link_stats;
int link_connect_time;
int link_stats_valid;

static int charshunt_pid;       /* Process ID for charshunt */

/*
 * We maintain a list of child process pids and
 * functions to call when they exit.
 */
struct subprocess {
    pid_t       pid;
    char        *prog;
    void        (*done) __P((void *));
    void        *arg;
    struct subprocess *next;
};

static struct subprocess *children;

/* Prototypes for procedures local to this file. */

static void setup_signals __P((void));
static void create_pidfile __P((void));
static void create_linkpidfile __P((void));
static void cleanup __P((void));
static void close_tty __P((void));
static void get_input __P((void));
static void calltimeout __P((void));
static struct timeval *timeleft __P((struct timeval *));
static void kill_my_pg __P((int));
static void hup __P((int));
static void term __P((int));
static void chld __P((int));
static void toggle_debug __P((int));
static void open_ccp __P((int));
static void bad_signal __P((int));
static void holdoff_end __P((void *));
static int device_script __P((char *, int, int, int));
static int reap_kids __P((int waitfor));
static void record_child __P((int, char *, void (*) (void *), void *));
static void update_db_entry __P((void));
static void add_db_key __P((const char *));
static void delete_db_key __P((const char *));
static int open_socket __P((char *));
static int start_charshunt __P((int, int));
static void charshunt_done __P((void *));
static void charshunt __P((int, int, char *));
static int record_write __P((FILE *, int code, u_char *buf, int nb,
                             struct timeval *));

extern  char    *ttyname __P((int));
extern  char    *getlogin __P((void));
int main __P((int, char *[]));

#ifdef ultrix
#undef  O_NONBLOCK
#define O_NONBLOCK      O_NDELAY
#endif

#ifdef ULTRIX
#define setlogmask(x)
#endif

/*
 * PPP Data Link Layer "protocol" table.
 * One entry per supported protocol.
 * The last entry must be NULL.
 */
struct protent *protocols[] = {
    &lcp_protent,
    &pap_protent,
    &chap_protent,
#ifdef CBCP_SUPPORT
    &cbcp_protent,
#endif
    &ipcp_protent,
#ifdef INET6
    &ipv6cp_protent,
#endif
    &ccp_protent,
#ifdef IPX_CHANGE
    &ipxcp_protent,
#endif
#ifdef AT_CHANGE
    &atcp_protent,
#endif
    NULL
};

int
main(argc, argv)
    int argc;
    char *argv[];
{
    int i, fdflags, t;
    char *p, *connector;
    struct passwd *pw;
    struct timeval timo;
    sigset_t mask;
    struct protent *protp;
    struct stat statbuf;
    char numbuf[16];

    new_phase(PHASE_INITIALIZE);

    /*
     * Ensure that fds 0, 1, 2 are open, to /dev/null if nowhere else.
     * This way we can close 0, 1, 2 in detach() without clobbering
     * a fd that we are using.
     */
    if ((i = open("/dev/null", O_RDWR)) >= 0) {
        while (0 <= i && i <= 2)
            i = dup(i);
        if (i >= 0)
            close(i);
    }

    script_env = NULL;

    /* Initialize syslog facilities */
    reopen_log();

    if (gethostname(hostname, MAXNAMELEN) < 0 ) {
        option_error("Couldn't get hostname: %m");
        exit(1);
    }
    hostname[MAXNAMELEN-1] = 0;

    /* make sure we don't create world or group writable files. */
    umask(umask(0777) | 022);

    uid = getuid();
    privileged = uid == 0;
    slprintf(numbuf, sizeof(numbuf), "%d", uid);
    script_setenv("ORIG_UID", numbuf, 0);

    ngroups = getgroups(NGROUPS_MAX, groups);

    /*
     * Initialize magic number generator now so that protocols may
     * use magic numbers in initialization.
     */
    magic_init();

    /*
     * Initialize to the standard option set, then parse, in order,
     * the system options file, the user's options file,
     * the tty's options file, and the command line arguments.
     */
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
        (*protp->init)(0);

    progname = *argv;

    prepass = 0;
    if (!options_from_file(_PATH_SYSOPTIONS, !privileged, 0, 1)
        || !options_from_user())
        exit(EXIT_OPTION_ERROR);

    /* scan command line and options files to find device name */
    prepass = 1;
    parse_args(argc-1, argv+1);
    prepass = 0;

    /*
     * Work out the device name, if it hasn't already been specified.
     */
    using_pty = notty || ptycommand != NULL || pty_socket != NULL;
    if (!using_pty && default_device) {
        char *p;
        if (!isatty(0) || (p = ttyname(0)) == NULL) {
            option_error("no device specified and stdin is not a tty");
            exit(EXIT_OPTION_ERROR);
        }
        strlcpy(devnam, p, sizeof(devnam));
        if (stat(devnam, &devstat) < 0)
            fatal("Couldn't stat default device %s: %m", devnam);
    }

    /*
     * Parse the tty options file and the command line.
     * The per-tty options file should not change
     * ptycommand, pty_socket, notty or devnam.
     */
    devnam_fixed = 1;
    if (!using_pty) {
        if (!options_for_tty())
            exit(EXIT_OPTION_ERROR);
    }

    devnam_fixed = 0;
    if (!parse_args(argc-1, argv+1))
        exit(EXIT_OPTION_ERROR);

    /*
     * Check that we are running as root.
     */
    if (geteuid() != 0) {
        option_error("must be root to run %s, since it is not setuid-root",
                     argv[0]);
        exit(EXIT_NOT_ROOT);
    }

    if (!ppp_available()) {
        option_error(no_ppp_msg);
        exit(EXIT_NO_KERNEL_SUPPORT);
    }

    /*
     * Check that the options given are valid and consistent.
     */
    if (!sys_check_options())
        exit(EXIT_OPTION_ERROR);
    auth_check_options();
#ifdef HAVE_MULTILINK
    mp_check_options();
#endif
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
        if (protp->check_options != NULL)
            (*protp->check_options)();
    if (demand && connect_script == 0) {
        option_error("connect script is required for demand-dialling\n");
        exit(EXIT_OPTION_ERROR);
    }
    /* default holdoff to 0 if no connect script has been given */
    if (connect_script == 0 && !holdoff_specified)
        holdoff = 0;

    if (using_pty) {
        if (!default_device) {
            option_error("%s option precludes specifying device name",
                         notty? "notty": "pty");
            exit(EXIT_OPTION_ERROR);
        }
        if (ptycommand != NULL && notty) {
            option_error("pty option is incompatible with notty option");
            exit(EXIT_OPTION_ERROR);
        }
        if (pty_socket != NULL && (ptycommand != NULL || notty)) {
            option_error("socket option is incompatible with pty and notty");
            exit(EXIT_OPTION_ERROR);
        }
        default_device = notty;
        lockflag = 0;
        modem = 0;
        if (notty && log_to_fd <= 1)
            log_to_fd = -1;
    } else {
        /*
         * If the user has specified a device which is the same as
         * the one on stdin, pretend they didn't specify any.
         * If the device is already open read/write on stdin,
         * we assume we don't need to lock it, and we can open it as root.
         */
        if (fstat(0, &statbuf) >= 0 && S_ISCHR(statbuf.st_mode)
            && statbuf.st_rdev == devstat.st_rdev) {
            default_device = 1;
            fdflags = fcntl(0, F_GETFL);
            if (fdflags != -1 && (fdflags & O_ACCMODE) == O_RDWR)
                privopen = 1;
        }
    }
    if (default_device)
        nodetach = 1;

    /*
     * Don't send log messages to the serial port, it tends to
     * confuse the peer. :-)
     */
    if (log_to_fd >= 0 && fstat(log_to_fd, &statbuf) >= 0
        && S_ISCHR(statbuf.st_mode) && statbuf.st_rdev == devstat.st_rdev)
        log_to_fd = -1;

    /*
     * Initialize system-dependent stuff.
     */
    sys_init();
    if (debug)
        setlogmask(LOG_UPTO(LOG_DEBUG));

    pppdb = tdb_open(_PATH_PPPDB, 0, TDB_CLEAR_IF_FIRST, O_RDWR|O_CREAT, 0644);
    if (pppdb != NULL) {
        slprintf(db_key, sizeof(db_key), "pppd%d", getpid());
        update_db_entry();
    } else {
        warn("Warning: couldn't open ppp database %s", _PATH_PPPDB);
        if (multilink) {
            warn("Warning: disabling multilink");
            multilink = 0;
        }
    }

    /*
     * Detach ourselves from the terminal, if required,
     * and identify who is running us.
     */
    if (!nodetach && !updetach)
        detach();
    p = getlogin();
    if (p == NULL) {
        pw = getpwuid(uid);
        if (pw != NULL && pw->pw_name != NULL)
            p = pw->pw_name;
        else
            p = "(unknown)";
    }
    syslog(LOG_NOTICE, "pppd %s.%d%s started by %s, uid %d",
           VERSION, PATCHLEVEL, IMPLEMENTATION, p, uid);
    script_setenv("PPPLOGNAME", p, 0);

    if (devnam[0])
        script_setenv("DEVICE", devnam, 1);

    setup_signals();

    waiting = 0;

    create_linkpidfile();

    /*
     * If we're doing dial-on-demand, set up the interface now.
     */
    if (demand) {
        /*
         * Open the loopback channel and set it up to be the ppp interface.
         */
        fd_loop = open_ppp_loopback();
        set_ifunit(1);

        /*
         * Configure the interface and mark it up, etc.
         */
        demand_conf();
    }

    do_callback = 0;
    for (;;) {

        need_holdoff = 1;
        ttyfd = -1;
        real_ttyfd = -1;
        status = EXIT_OK;
        ++unsuccess;
        doing_callback = do_callback;
        do_callback = 0;

        if (demand && !doing_callback) {
            /*
             * Don't do anything until we see some activity.
             */
            kill_link = 0;
            new_phase(PHASE_DORMANT);
            demand_unblock();
            add_fd(fd_loop);
            for (;;) {
                if (sigsetjmp(sigjmp, 1) == 0) {
                    sigprocmask(SIG_BLOCK, &mask, NULL);
                    if (kill_link || got_sigchld) {
                        sigprocmask(SIG_UNBLOCK, &mask, NULL);
                    } else {
                        waiting = 1;
                        sigprocmask(SIG_UNBLOCK, &mask, NULL);
                        wait_input(timeleft(&timo));
                    }
                }
                waiting = 0;
                calltimeout();
                if (kill_link) {
                    if (!persist)
                        break;
                    kill_link = 0;
                }
                if (get_loop_output())
                    break;
                if (got_sigchld)
                    reap_kids(0);
            }
            remove_fd(fd_loop);
            if (kill_link && !persist)
                break;

            /*
             * Now we want to bring up the link.
             */
            demand_block();
            info("Starting link");
        }

        new_phase(PHASE_SERIALCONN);

        /*
         * Get a pty master/slave pair if the pty, notty, socket,
         * or record options were specified.
         */
        strlcpy(ppp_devnam, devnam, sizeof(ppp_devnam));
        pty_master = -1;
        pty_slave = -1;
        if (using_pty || record_file != NULL) {
            if (!get_pty(&pty_master, &pty_slave, ppp_devnam, uid)) {
                error("Couldn't allocate pseudo-tty");
                status = EXIT_FATAL_ERROR;
                goto fail;
            }
            set_up_tty(pty_slave, 1);
        }

        /*
         * Lock the device if we've been asked to.
         */
        status = EXIT_LOCK_FAILED;
        if (lockflag && !privopen) {
            if (lock(devnam) < 0)
                goto fail;
            locked = 1;
        }

        /*
         * Open the serial device and set it up to be the ppp interface.
         * First we open it in non-blocking mode so we can set the
         * various termios flags appropriately.  If we aren't dialling
         * out and we want to use the modem lines, we reopen it later
         * in order to wait for the carrier detect signal from the modem.
         */
        hungup = 0;
        kill_link = 0;
        connector = doing_callback? callback_script: connect_script;
        if (devnam[0] != 0) {
            for (;;) {
                /* If the user specified the device name, become the
                   user before opening it. */
                int err;
                if (!devnam_info.priv && !privopen)
                    seteuid(uid);
                ttyfd = open(devnam, O_NONBLOCK | O_RDWR, 0);
                err = errno;
                if (!devnam_info.priv && !privopen)
                    seteuid(0);
                if (ttyfd >= 0)
                    break;
                errno = err;
                if (err != EINTR) {
                    error("Failed to open %s: %m", devnam);
                    status = EXIT_OPEN_FAILED;
                }
                if (!persist || err != EINTR)
                    goto fail;
            }
            if ((fdflags = fcntl(ttyfd, F_GETFL)) == -1
                || fcntl(ttyfd, F_SETFL, fdflags & ~O_NONBLOCK) < 0)
                warn("Couldn't reset non-blocking mode on device: %m");

            /*
             * Do the equivalent of `mesg n' to stop broadcast messages.
             */
            if (fstat(ttyfd, &statbuf) < 0
                || fchmod(ttyfd, statbuf.st_mode & ~(S_IWGRP | S_IWOTH)) < 0) {
                warn("Couldn't restrict write permissions to %s: %m", devnam);
            } else
                tty_mode = statbuf.st_mode;

            /*
             * Set line speed, flow control, etc.
             * If we have a non-null connection or initializer script,
             * on most systems we set CLOCAL for now so that we can talk
             * to the modem before carrier comes up.  But this has the
             * side effect that we might miss it if CD drops before we
             * get to clear CLOCAL below.  On systems where we can talk
             * successfully to the modem with CLOCAL clear and CD down,
             * we could clear CLOCAL at this point.
             */
            set_up_tty(ttyfd, ((connector != NULL && connector[0] != 0)
                               || initializer != NULL));
            real_ttyfd = ttyfd;
        }

        /*
         * If the pty, socket, notty and/or record option was specified,
         * start up the character shunt now.
         */
        status = EXIT_PTYCMD_FAILED;
        if (ptycommand != NULL) {
            if (record_file != NULL) {
                int ipipe[2], opipe[2], ok;

                if (pipe(ipipe) < 0 || pipe(opipe) < 0)
                    fatal("Couldn't create pipes for record option: %m");
                ok = device_script(ptycommand, opipe[0], ipipe[1], 1) == 0
                    && start_charshunt(ipipe[0], opipe[1]);
                close(ipipe[0]);
                close(ipipe[1]);
                close(opipe[0]);
                close(opipe[1]);
                if (!ok)
                    goto fail;
            } else {
                if (device_script(ptycommand, pty_master, pty_master, 1) < 0)
                    goto fail;
                ttyfd = pty_slave;
                close(pty_master);
                pty_master = -1;
            }
        } else if (pty_socket != NULL) {
            int fd = open_socket(pty_socket);
            if (fd < 0)
                goto fail;
            if (!start_charshunt(fd, fd))
                goto fail;
        } else if (notty) {
            if (!start_charshunt(0, 1))
                goto fail;
        } else if (record_file != NULL) {
            if (!start_charshunt(ttyfd, ttyfd))
                goto fail;
        }

        /* run connection script */
        if ((connector && connector[0]) || initializer) {
            if (real_ttyfd != -1) {
                /* XXX do this if doing_callback == CALLBACK_DIALIN? */
                if (!default_device && modem) {
                    setdtr(real_ttyfd, 0);      /* in case modem is off hook */
                    sleep(1);
                    setdtr(real_ttyfd, 1);
                }
            }

            if (initializer && initializer[0]) {
                if (device_script(initializer, ttyfd, ttyfd, 0) < 0) {
                    error("Initializer script failed");
                    status = EXIT_INIT_FAILED;
                    goto fail;
                }
                if (kill_link)
                    goto disconnect;

                info("Serial port initialized.");
            }

            if (connector && connector[0]) {
                if (device_script(connector, ttyfd, ttyfd, 0) < 0) {
                    error("Connect script failed");
                    status = EXIT_CONNECT_FAILED;
                    goto fail;
                }
                if (kill_link)
                    goto disconnect;

                info("Serial connection established.");
            }

            /* set line speed, flow control, etc.;
               clear CLOCAL if modem option */
            if (real_ttyfd != -1)
                set_up_tty(real_ttyfd, 0);

            if (doing_callback == CALLBACK_DIALIN)
                connector = NULL;
        }

        /* reopen tty if necessary to wait for carrier */
        if (connector == NULL && modem && devnam[0] != 0) {
            for (;;) {
                if ((i = open(devnam, O_RDWR)) >= 0)
                    break;
                if (errno != EINTR) {
                    error("Failed to reopen %s: %m", devnam);
                    status = EXIT_OPEN_FAILED;
                }
                if (!persist || errno != EINTR || hungup || kill_link)
                    goto fail;
            }
            close(i);
        }

        slprintf(numbuf, sizeof(numbuf), "%d", baud_rate);
        script_setenv("SPEED", numbuf, 0);

        /* run welcome script, if any */
        if (welcomer && welcomer[0]) {
            if (device_script(welcomer, ttyfd, ttyfd, 0) < 0)
                warn("Welcome script failed");
        }

        /* set up the serial device as a ppp interface */
        fd_ppp = establish_ppp(ttyfd);
        if (fd_ppp < 0) {
            status = EXIT_FATAL_ERROR;
            goto disconnect;
        }

        if (!demand && ifunit >= 0)
            set_ifunit(1);

        /*
         * Start opening the connection and wait for
         * incoming events (reply, timeout, etc.).
         */
        notice("Connect: %s <--> %s", ifname, ppp_devnam);
        gettimeofday(&start_time, NULL);
        link_stats_valid = 0;
        script_unsetenv("CONNECT_TIME");
        script_unsetenv("BYTES_SENT");
        script_unsetenv("BYTES_RCVD");
        lcp_lowerup(0);

        /*
         * If we are initiating this connection, wait for a short
         * time for something from the peer.  This can avoid bouncing
         * our packets off his tty before he has it set up.
         */
        add_fd(fd_ppp);
        if (connect_delay != 0 && (connector != NULL || ptycommand != NULL)) {
            struct timeval t;
            t.tv_sec = connect_delay / 1000;
            t.tv_usec = connect_delay % 1000;
            wait_input(&t);
        }

        lcp_open(0);            /* Start protocol */
        open_ccp_flag = 0;
        status = EXIT_NEGOTIATION_FAILED;
        new_phase(PHASE_ESTABLISH);
        while (phase != PHASE_DEAD) {
            if (sigsetjmp(sigjmp, 1) == 0) {
                sigprocmask(SIG_BLOCK, &mask, NULL);
                if (kill_link || open_ccp_flag || got_sigchld) {
                    sigprocmask(SIG_UNBLOCK, &mask, NULL);
                } else {
                    waiting = 1;
                    sigprocmask(SIG_UNBLOCK, &mask, NULL);
                    wait_input(timeleft(&timo));
                }
            }
            waiting = 0;
            calltimeout();
            get_input();
            if (kill_link) {
                lcp_close(0, "User request");
                kill_link = 0;
            }
            if (open_ccp_flag) {
                if (phase == PHASE_NETWORK || phase == PHASE_RUNNING) {
                    ccp_fsm[0].flags = OPT_RESTART; /* clears OPT_SILENT */
                    (*ccp_protent.open)(0);
                }
                open_ccp_flag = 0;
            }
            if (got_sigchld)
                reap_kids(0);   /* Don't leave dead kids lying around */
        }

        /*
         * Print connect time and statistics.
         */
        if (link_stats_valid) {
            int t = (link_connect_time + 5) / 6;    /* 1/10ths of minutes */
            info("Connect time %d.%d minutes.", t/10, t%10);
            info("Sent %d bytes, received %d bytes.",
                 link_stats.bytes_out, link_stats.bytes_in);
        }

        /*
         * Delete pid file before disestablishing ppp.  Otherwise it
         * can happen that another pppd gets the same unit and then
         * we delete its pid file.
         */
        if (!demand) {
            if (pidfilename[0] != 0
                && unlink(pidfilename) < 0 && errno != ENOENT) 
                warn("unable to delete pid file %s: %m", pidfilename);
            pidfilename[0] = 0;
        }

        /*
         * If we may want to bring the link up again, transfer
         * the ppp unit back to the loopback.  Set the
         * real serial device back to its normal mode of operation.
         */
        remove_fd(fd_ppp);
        clean_check();
        if (demand)
            restore_loop();
        disestablish_ppp(ttyfd);
        fd_ppp = -1;
        if (!hungup)
            lcp_lowerdown(0);

        /*
         * Run disconnector script, if requested.
         * XXX we may not be able to do this if the line has hung up!
         */
    disconnect:
        if (disconnect_script && !hungup) {
            new_phase(PHASE_DISCONNECT);
            if (real_ttyfd >= 0)
                set_up_tty(real_ttyfd, 1);
            if (device_script(disconnect_script, ttyfd, ttyfd, 0) < 0) {
                warn("disconnect script failed");
            } else {
                info("Serial link disconnected.");
            }
        }

    fail:
        if (pty_master >= 0)
            close(pty_master);
        if (pty_slave >= 0)
            close(pty_slave);
        if (real_ttyfd >= 0)
            close_tty();
        if (locked) {
            unlock();
            locked = 0;
        }

        if (!demand) {
            if (pidfilename[0] != 0
                && unlink(pidfilename) < 0 && errno != ENOENT) 
                warn("unable to delete pid file %s: %m", pidfilename);
            pidfilename[0] = 0;
        }

        if (!persist || (maxfail > 0 && unsuccess >= maxfail))
            break;

        kill_link = 0;
        if (demand)
            demand_discard();
        t = need_holdoff? holdoff: 0;
        if (holdoff_hook)
            t = (*holdoff_hook)();
        if (t > 0) {
            new_phase(PHASE_HOLDOFF);
            TIMEOUT(holdoff_end, NULL, t);
            do {
                if (sigsetjmp(sigjmp, 1) == 0) {
                    sigprocmask(SIG_BLOCK, &mask, NULL);
                    if (kill_link || got_sigchld) {
                        sigprocmask(SIG_UNBLOCK, &mask, NULL);
                    } else {
                        waiting = 1;
                        sigprocmask(SIG_UNBLOCK, &mask, NULL);
                        wait_input(timeleft(&timo));
                    }
                }
                waiting = 0;
                calltimeout();
                if (kill_link) {
                    kill_link = 0;
                    new_phase(PHASE_DORMANT); /* allow signal to end holdoff */
                }
                if (got_sigchld)
                    reap_kids(0);
            } while (phase == PHASE_HOLDOFF);
            if (!persist)
                break;
        }
    }

    /* Wait for scripts to finish */
    /* XXX should have a timeout here */
    while (n_children > 0) {
        if (debug) {
            struct subprocess *chp;
            dbglog("Waiting for %d child processes...", n_children);
            for (chp = children; chp != NULL; chp = chp->next)
                dbglog("  script %s, pid %d", chp->prog, chp->pid);
        }
        if (reap_kids(1) < 0)
            break;
    }

    die(status);
    return 0;
}

/*
 * setup_signals - initialize signal handling.
 */
static void
setup_signals()
{
    struct sigaction sa;
    sigset_t mask;

    /*
     * Compute mask of all interesting signals and install signal handlers
     * for each.  Only one signal handler may be active at a time.  Therefore,
     * all other signals should be masked when any handler is executing.
     */
    sigemptyset(&mask);
    sigaddset(&mask, SIGHUP);
    sigaddset(&mask, SIGINT);
    sigaddset(&mask, SIGTERM);
    sigaddset(&mask, SIGCHLD);
    sigaddset(&mask, SIGUSR2);

#define SIGNAL(s, handler)      do { \
        sa.sa_handler = handler; \
        if (sigaction(s, &sa, NULL) < 0) \
            fatal("Couldn't establish signal handler (%d): %m", s); \
    } while (0)

    sa.sa_mask = mask;
    sa.sa_flags = 0;
    SIGNAL(SIGHUP, hup);                /* Hangup */
    SIGNAL(SIGINT, term);               /* Interrupt */
    SIGNAL(SIGTERM, term);              /* Terminate */
    SIGNAL(SIGCHLD, chld);

    SIGNAL(SIGUSR1, toggle_debug);      /* Toggle debug flag */
    SIGNAL(SIGUSR2, open_ccp);          /* Reopen CCP */

    /*
     * Install a handler for other signals which would otherwise
     * cause pppd to exit without cleaning up.
     */
    SIGNAL(SIGABRT, bad_signal);
    SIGNAL(SIGALRM, bad_signal);
    SIGNAL(SIGFPE, bad_signal);
    SIGNAL(SIGILL, bad_signal);
    SIGNAL(SIGPIPE, bad_signal);
    SIGNAL(SIGQUIT, bad_signal);
    SIGNAL(SIGSEGV, bad_signal);
#ifdef SIGBUS
    SIGNAL(SIGBUS, bad_signal);
#endif
#ifdef SIGEMT
    SIGNAL(SIGEMT, bad_signal);
#endif
#ifdef SIGPOLL
    SIGNAL(SIGPOLL, bad_signal);
#endif
#ifdef SIGPROF
    SIGNAL(SIGPROF, bad_signal);
#endif
#ifdef SIGSYS
    SIGNAL(SIGSYS, bad_signal);
#endif
#ifdef SIGTRAP
    SIGNAL(SIGTRAP, bad_signal);
#endif
#ifdef SIGVTALRM
    SIGNAL(SIGVTALRM, bad_signal);
#endif
#ifdef SIGXCPU
    SIGNAL(SIGXCPU, bad_signal);
#endif
#ifdef SIGXFSZ
    SIGNAL(SIGXFSZ, bad_signal);
#endif

    /*
     * Apparently we can get a SIGPIPE when we call syslog, if
     * syslogd has died and been restarted.  Ignoring it seems
     * be sufficient.
     */
    signal(SIGPIPE, SIG_IGN);
}

/*
 * set_ifunit - do things we need to do once we know which ppp
 * unit we are using.
 */
void
set_ifunit(iskey)
    int iskey;
{
    info("Using interface ppp%d", ifunit);
    slprintf(ifname, sizeof(ifname), "ppp%d", ifunit);
    script_setenv("IFNAME", ifname, iskey);
    create_pidfile();   /* write pid to file */
    create_linkpidfile();
}

/*
 * detach - detach us from the controlling terminal.
 */
void
detach()
{
    int pid;

    if (detached)
        return;
    if ((pid = fork()) < 0) {
        error("Couldn't detach (fork failed: %m)");
        die(1);                 /* or just return? */
    }
    if (pid != 0) {
        /* parent */
        if (locked)
            relock(pid);
        exit(0);                /* parent dies */
    }
    setsid();
    chdir("/");
    close(0);
    close(1);
    close(2);
    detached = 1;
    log_to_fd = -1;
    /* update pid files if they have been written already */
    if (pidfilename[0])
        create_pidfile();
    if (linkpidfile[0])
        create_linkpidfile();
}

/*
 * reopen_log - (re)open our connection to syslog.
 */
void
reopen_log()
{
#ifdef ULTRIX
    openlog("pppd", LOG_PID);
#else
    openlog("pppd", LOG_PID | LOG_NDELAY, LOG_PPP);
    setlogmask(LOG_UPTO(LOG_INFO));
#endif
}

/*
 * Create a file containing our process ID.
 */
static void
create_pidfile()
{
    FILE *pidfile;
    char numbuf[16];

    slprintf(pidfilename, sizeof(pidfilename), "%s%s.pid",
             _PATH_VARRUN, ifname);
    if ((pidfile = fopen(pidfilename, "w")) != NULL) {
        fprintf(pidfile, "%d\n", getpid());
        (void) fclose(pidfile);
    } else {
        error("Failed to create pid file %s: %m", pidfilename);
        pidfilename[0] = 0;
    }
    slprintf(numbuf, sizeof(numbuf), "%d", getpid());
    script_setenv("PPPD_PID", numbuf, 1);
}

static void
create_linkpidfile()
{
    FILE *pidfile;

    if (linkname[0] == 0)
        return;
    slprintf(linkpidfile, sizeof(linkpidfile), "%sppp-%s.pid",
             _PATH_VARRUN, linkname);
    if ((pidfile = fopen(linkpidfile, "w")) != NULL) {
        fprintf(pidfile, "%d\n", getpid());
        if (ifname[0])
            fprintf(pidfile, "%s\n", ifname);
        (void) fclose(pidfile);
    } else {
        error("Failed to create pid file %s: %m", linkpidfile);
        linkpidfile[0] = 0;
    }
    script_setenv("LINKNAME", linkname, 1);
}

/*
 * holdoff_end - called via a timeout when the holdoff period ends.
 */
static void
holdoff_end(arg)
    void *arg;
{
    new_phase(PHASE_DORMANT);
}

/* List of protocol names, to make our messages a little more informative. */
struct protocol_list {
    u_short     proto;
    const char  *name;
} protocol_list[] = {
    { 0x21,     "IP" },
    { 0x23,     "OSI Network Layer" },
    { 0x25,     "Xerox NS IDP" },
    { 0x27,     "DECnet Phase IV" },
    { 0x29,     "Appletalk" },
    { 0x2b,     "Novell IPX" },
    { 0x2d,     "VJ compressed TCP/IP" },
    { 0x2f,     "VJ uncompressed TCP/IP" },
    { 0x31,     "Bridging PDU" },
    { 0x33,     "Stream Protocol ST-II" },
    { 0x35,     "Banyan Vines" },
    { 0x39,     "AppleTalk EDDP" },
    { 0x3b,     "AppleTalk SmartBuffered" },
    { 0x3d,     "Multi-Link" },
    { 0x3f,     "NETBIOS Framing" },
    { 0x41,     "Cisco Systems" },
    { 0x43,     "Ascom Timeplex" },
    { 0x45,     "Fujitsu Link Backup and Load Balancing (LBLB)" },
    { 0x47,     "DCA Remote Lan" },
    { 0x49,     "Serial Data Transport Protocol (PPP-SDTP)" },
    { 0x4b,     "SNA over 802.2" },
    { 0x4d,     "SNA" },
    { 0x4f,     "IP6 Header Compression" },
    { 0x6f,     "Stampede Bridging" },
    { 0xfb,     "single-link compression" },
    { 0xfd,     "1st choice compression" },
    { 0x0201,   "802.1d Hello Packets" },
    { 0x0203,   "IBM Source Routing BPDU" },
    { 0x0205,   "DEC LANBridge100 Spanning Tree" },
    { 0x0231,   "Luxcom" },
    { 0x0233,   "Sigma Network Systems" },
    { 0x8021,   "Internet Protocol Control Protocol" },
    { 0x8023,   "OSI Network Layer Control Protocol" },
    { 0x8025,   "Xerox NS IDP Control Protocol" },
    { 0x8027,   "DECnet Phase IV Control Protocol" },
    { 0x8029,   "Appletalk Control Protocol" },
    { 0x802b,   "Novell IPX Control Protocol" },
    { 0x8031,   "Bridging NCP" },
    { 0x8033,   "Stream Protocol Control Protocol" },
    { 0x8035,   "Banyan Vines Control Protocol" },
    { 0x803d,   "Multi-Link Control Protocol" },
    { 0x803f,   "NETBIOS Framing Control Protocol" },
    { 0x8041,   "Cisco Systems Control Protocol" },
    { 0x8043,   "Ascom Timeplex" },
    { 0x8045,   "Fujitsu LBLB Control Protocol" },
    { 0x8047,   "DCA Remote Lan Network Control Protocol (RLNCP)" },
    { 0x8049,   "Serial Data Control Protocol (PPP-SDCP)" },
    { 0x804b,   "SNA over 802.2 Control Protocol" },
    { 0x804d,   "SNA Control Protocol" },
    { 0x804f,   "IP6 Header Compression Control Protocol" },
    { 0x006f,   "Stampede Bridging Control Protocol" },
    { 0x80fb,   "Single Link Compression Control Protocol" },
    { 0x80fd,   "Compression Control Protocol" },
    { 0xc021,   "Link Control Protocol" },
    { 0xc023,   "Password Authentication Protocol" },
    { 0xc025,   "Link Quality Report" },
    { 0xc027,   "Shiva Password Authentication Protocol" },
    { 0xc029,   "CallBack Control Protocol (CBCP)" },
    { 0xc081,   "Container Control Protocol" },
    { 0xc223,   "Challenge Handshake Authentication Protocol" },
    { 0xc281,   "Proprietary Authentication Protocol" },
    { 0,        NULL },
};

/*
 * protocol_name - find a name for a PPP protocol.
 */
const char *
protocol_name(proto)
    int proto;
{
    struct protocol_list *lp;

    for (lp = protocol_list; lp->proto != 0; ++lp)
        if (proto == lp->proto)
            return lp->name;
    return NULL;
}

/*
 * get_input - called when incoming data is available.
 */
static void
get_input()
{
    int len, i;
    u_char *p;
    u_short protocol;
    struct protent *protp;

    p = inpacket_buf;   /* point to beginning of packet buffer */

    len = read_packet(inpacket_buf);
    if (len < 0)
        return;

    if (len == 0) {
        notice("Modem hangup");
        hungup = 1;
        status = EXIT_HANGUP;
        lcp_lowerdown(0);       /* serial link is no longer available */
        link_terminated(0);
        return;
    }

    if (debug /*&& (debugflags & DBG_INPACKET)*/)
        dbglog("rcvd %P", p, len);

    if (len < PPP_HDRLEN) {
        MAINDEBUG(("io(): Received short packet."));
        return;
    }

    p += 2;                             /* Skip address and control */
    GETSHORT(protocol, p);
    len -= PPP_HDRLEN;

    /*
     * Toss all non-LCP packets unless LCP is OPEN.
     */
    if (protocol != PPP_LCP && lcp_fsm[0].state != OPENED) {
        MAINDEBUG(("get_input: Received non-LCP packet when LCP not open."));
        return;
    }

    /*
     * Until we get past the authentication phase, toss all packets
     * except LCP, LQR and authentication packets.
     */
    if (phase <= PHASE_AUTHENTICATE
        && !(protocol == PPP_LCP || protocol == PPP_LQR
             || protocol == PPP_PAP || protocol == PPP_CHAP)) {
        MAINDEBUG(("get_input: discarding proto 0x%x in phase %d",
                   protocol, phase));
        return;
    }

    /*
     * Upcall the proper protocol input routine.
     */
    for (i = 0; (protp = protocols[i]) != NULL; ++i) {
        if (protp->protocol == protocol && protp->enabled_flag) {
            (*protp->input)(0, p, len);
            return;
        }
        if (protocol == (protp->protocol & ~0x8000) && protp->enabled_flag
            && protp->datainput != NULL) {
            (*protp->datainput)(0, p, len);
            return;
        }
    }

    if (debug) {
        const char *pname = protocol_name(protocol);
        if (pname != NULL)
            warn("Unsupported protocol '%s' (0x%x) received", pname, protocol);
        else
            warn("Unsupported protocol 0x%x received", protocol);
    }
    lcp_sprotrej(0, p - PPP_HDRLEN, len + PPP_HDRLEN);
}

/*
 * new_phase - signal the start of a new phase of pppd's operation.
 */
void
new_phase(p)
    int p;
{
    phase = p;
    if (new_phase_hook)
        (*new_phase_hook)(p);
}

/*
 * die - clean up state and exit with the specified status.
 */
void
die(status)
    int status;
{
    cleanup();
    syslog(LOG_INFO, "Exit.");
    exit(status);
}

/*
 * cleanup - restore anything which needs to be restored before we exit
 */
/* ARGSUSED */
static void
cleanup()
{
    sys_cleanup();

    if (fd_ppp >= 0)
        disestablish_ppp(ttyfd);
    if (real_ttyfd >= 0)
        close_tty();

    if (pidfilename[0] != 0 && unlink(pidfilename) < 0 && errno != ENOENT) 
        warn("unable to delete pid file %s: %m", pidfilename);
    pidfilename[0] = 0;
    if (linkpidfile[0] != 0 && unlink(linkpidfile) < 0 && errno != ENOENT) 
        warn("unable to delete pid file %s: %m", linkpidfile);
    linkpidfile[0] = 0;

    if (locked)
        unlock();

    if (pppdb != NULL) {
        TDB_DATA key;

        key.dptr = db_key;
        key.dsize = strlen(db_key);
        tdb_delete(pppdb, key);
    }
}

/*
 * close_tty - restore the terminal device and close it.
 */
static void
close_tty()
{
    /* drop dtr to hang up */
    if (!default_device && modem) {
        setdtr(real_ttyfd, 0);
        /*
         * This sleep is in case the serial port has CLOCAL set by default,
         * and consequently will reassert DTR when we close the device.
         */
        sleep(1);
    }

    restore_tty(real_ttyfd);

    if (tty_mode != (mode_t) -1) {
        if (fchmod(real_ttyfd, tty_mode) != 0) {
            /* XXX if devnam is a symlink, this will change the link */
            chmod(devnam, tty_mode);
        }
    }

    close(real_ttyfd);
    real_ttyfd = -1;
}

/*
 * update_link_stats - get stats at link termination.
 */
void
update_link_stats(u)
    int u;
{
    struct timeval now;
    char numbuf[32];

    if (!get_ppp_stats(u, &link_stats)
        || gettimeofday(&now, NULL) < 0)
        return;
    link_connect_time = now.tv_sec - start_time.tv_sec;
    link_stats_valid = 1;

    slprintf(numbuf, sizeof(numbuf), "%d", link_connect_time);
    script_setenv("CONNECT_TIME", numbuf, 0);
    slprintf(numbuf, sizeof(numbuf), "%d", link_stats.bytes_out);
    script_setenv("BYTES_SENT", numbuf, 0);
    slprintf(numbuf, sizeof(numbuf), "%d", link_stats.bytes_in);
    script_setenv("BYTES_RCVD", numbuf, 0);
}


struct  callout {
    struct timeval      c_time;         /* time at which to call routine */
    void                *c_arg;         /* argument to routine */
    void                (*c_func) __P((void *)); /* routine */
    struct              callout *c_next;
};

static struct callout *callout = NULL;  /* Callout list */
static struct timeval timenow;          /* Current time */

/*
 * timeout - Schedule a timeout.
 *
 * Note that this timeout takes the number of seconds, NOT hz (as in
 * the kernel).
 */
void
timeout(func, arg, time)
    void (*func) __P((void *));
    void *arg;
    int time;
{
    struct callout *newp, *p, **pp;
  
    MAINDEBUG(("Timeout %p:%p in %d seconds.", func, arg, time));
  
    /*
     * Allocate timeout.
     */
    if ((newp = (struct callout *) malloc(sizeof(struct callout))) == NULL)
        fatal("Out of memory in timeout()!");
    newp->c_arg = arg;
    newp->c_func = func;
    gettimeofday(&timenow, NULL);
    newp->c_time.tv_sec = timenow.tv_sec + time;
    newp->c_time.tv_usec = timenow.tv_usec;
  
    /*
     * Find correct place and link it in.
     */
    for (pp = &callout; (p = *pp); pp = &p->c_next)
        if (newp->c_time.tv_sec < p->c_time.tv_sec
            || (newp->c_time.tv_sec == p->c_time.tv_sec
                && newp->c_time.tv_usec < p->c_time.tv_usec))
            break;
    newp->c_next = p;
    *pp = newp;
}


/*
 * untimeout - Unschedule a timeout.
 */
void
untimeout(func, arg)
    void (*func) __P((void *));
    void *arg;
{
    struct callout **copp, *freep;
  
    MAINDEBUG(("Untimeout %p:%p.", func, arg));
  
    /*
     * Find first matching timeout and remove it from the list.
     */
    for (copp = &callout; (freep = *copp); copp = &freep->c_next)
        if (freep->c_func == func && freep->c_arg == arg) {
            *copp = freep->c_next;
            free((char *) freep);
            break;
        }
}


/*
 * calltimeout - Call any timeout routines which are now due.
 */
static void
calltimeout()
{
    struct callout *p;

    while (callout != NULL) {
        p = callout;

        if (gettimeofday(&timenow, NULL) < 0)
            fatal("Failed to get time of day: %m");
        if (!(p->c_time.tv_sec < timenow.tv_sec
              || (p->c_time.tv_sec == timenow.tv_sec
                  && p->c_time.tv_usec <= timenow.tv_usec)))
            break;              /* no, it's not time yet */

        callout = p->c_next;
        (*p->c_func)(p->c_arg);

        free((char *) p);
    }
}


/*
 * timeleft - return the length of time until the next timeout is due.
 */
static struct timeval *
timeleft(tvp)
    struct timeval *tvp;
{
    if (callout == NULL)
        return NULL;

    gettimeofday(&timenow, NULL);
    tvp->tv_sec = callout->c_time.tv_sec - timenow.tv_sec;
    tvp->tv_usec = callout->c_time.tv_usec - timenow.tv_usec;
    if (tvp->tv_usec < 0) {
        tvp->tv_usec += 1000000;
        tvp->tv_sec -= 1;
    }
    if (tvp->tv_sec < 0)
        tvp->tv_sec = tvp->tv_usec = 0;

    return tvp;
}


/*
 * kill_my_pg - send a signal to our process group, and ignore it ourselves.
 */
static void
kill_my_pg(sig)
    int sig;
{
    struct sigaction act, oldact;

    act.sa_handler = SIG_IGN;
    act.sa_flags = 0;
    kill(0, sig);
    sigaction(sig, &act, &oldact);
    sigaction(sig, &oldact, NULL);
}


/*
 * hup - Catch SIGHUP signal.
 *
 * Indicates that the physical layer has been disconnected.
 * We don't rely on this indication; if the user has sent this
 * signal, we just take the link down.
 */
static void
hup(sig)
    int sig;
{
    info("Hangup (SIGHUP)");
    kill_link = 1;
    if (status != EXIT_HANGUP)
        status = EXIT_USER_REQUEST;
    if (conn_running)
        /* Send the signal to the [dis]connector process(es) also */
        kill_my_pg(sig);
    if (charshunt_pid)
        kill(charshunt_pid, sig);
    if (waiting)
        siglongjmp(sigjmp, 1);
}


/*
 * term - Catch SIGTERM signal and SIGINT signal (^C/del).
 *
 * Indicates that we should initiate a graceful disconnect and exit.
 */
/*ARGSUSED*/
static void
term(sig)
    int sig;
{
    info("Terminating on signal %d.", sig);
    persist = 0;                /* don't try to restart */
    kill_link = 1;
    status = EXIT_USER_REQUEST;
    if (conn_running)
        /* Send the signal to the [dis]connector process(es) also */
        kill_my_pg(sig);
    if (charshunt_pid)
        kill(charshunt_pid, sig);
    if (waiting)
        siglongjmp(sigjmp, 1);
}


/*
 * chld - Catch SIGCHLD signal.
 * Sets a flag so we will call reap_kids in the mainline.
 */
static void
chld(sig)
    int sig;
{
    got_sigchld = 1;
    if (waiting)
        siglongjmp(sigjmp, 1);
}


/*
 * toggle_debug - Catch SIGUSR1 signal.
 *
 * Toggle debug flag.
 */
/*ARGSUSED*/
static void
toggle_debug(sig)
    int sig;
{
    debug = !debug;
    if (debug) {
        setlogmask(LOG_UPTO(LOG_DEBUG));
    } else {
        setlogmask(LOG_UPTO(LOG_WARNING));
    }
}


/*
 * open_ccp - Catch SIGUSR2 signal.
 *
 * Try to (re)negotiate compression.
 */
/*ARGSUSED*/
static void
open_ccp(sig)
    int sig;
{
    open_ccp_flag = 1;
    if (waiting)
        siglongjmp(sigjmp, 1);
}


/*
 * bad_signal - We've caught a fatal signal.  Clean up state and exit.
 */
static void
bad_signal(sig)
    int sig;
{
    static int crashed = 0;

    if (crashed)
        _exit(127);
    crashed = 1;
    error("Fatal signal %d", sig);
    if (conn_running)
        kill_my_pg(SIGTERM);
    if (charshunt_pid)
        kill(charshunt_pid, SIGTERM);
    die(127);
}


/*
 * device_script - run a program to talk to the serial device
 * (e.g. to run the connector or disconnector script).
 */
static int
device_script(program, in, out, dont_wait)
    char *program;
    int in, out;
    int dont_wait;
{
    int pid;
    int status = -1;
    int errfd;

    ++conn_running;
    pid = fork();

    if (pid < 0) {
        --conn_running;
        error("Failed to create child process: %m");
        return -1;
    }

    if (pid == 0) {
        sys_close();
        closelog();
        if (in == 2) {
            /* aargh!!! */
            int newin = dup(in);
            if (in == out)
                out = newin;
            in = newin;
        } else if (out == 2) {
            out = dup(out);
        }
        if (log_to_fd >= 0) {
            if (log_to_fd != 2)
                dup2(log_to_fd, 2);
        } else {
            close(2);
            errfd = open(_PATH_CONNERRS, O_WRONLY | O_APPEND | O_CREAT, 0600);
            if (errfd >= 0 && errfd != 2) {
                dup2(errfd, 2);
                close(errfd);
            }
        }
        if (in != 0) {
            if (out == 0)
                out = dup(out);
            dup2(in, 0);
        }
        if (out != 1) {
            dup2(out, 1);
        }
        if (real_ttyfd > 2)
            close(real_ttyfd);
        if (pty_master > 2)
            close(pty_master);
        if (pty_slave > 2)
            close(pty_slave);
        setuid(uid);
        if (getuid() != uid) {
            error("setuid failed");
            exit(1);
        }
        setgid(getgid());
        execl("/bin/sh", "sh", "-c", program, (char *)0);
        error("could not exec /bin/sh: %m");
        exit(99);
        /* NOTREACHED */
    }

    if (dont_wait) {
        record_child(pid, program, NULL, NULL);
        status = 0;
    } else {
        while (waitpid(pid, &status, 0) < 0) {
            if (errno == EINTR)
                continue;
            fatal("error waiting for (dis)connection process: %m");
        }
        --conn_running;
    }

    return (status == 0 ? 0 : -1);
}


/*
 * run-program - execute a program with given arguments,
 * but don't wait for it.
 * If the program can't be executed, logs an error unless
 * must_exist is 0 and the program file doesn't exist.
 * Returns -1 if it couldn't fork, 0 if the file doesn't exist
 * or isn't an executable plain file, or the process ID of the child.
 * If done != NULL, (*done)(arg) will be called later (within
 * reap_kids) iff the return value is > 0.
 */
pid_t
run_program(prog, args, must_exist, done, arg)
    char *prog;
    char **args;
    int must_exist;
    void (*done) __P((void *));
    void *arg;
{
    int pid;
    struct stat sbuf;

    /*
     * First check if the file exists and is executable.
     * We don't use access() because that would use the
     * real user-id, which might not be root, and the script
     * might be accessible only to root.
     */
    errno = EINVAL;
    if (stat(prog, &sbuf) < 0 || !S_ISREG(sbuf.st_mode)
        || (sbuf.st_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) == 0) {
        if (must_exist || errno != ENOENT)
            warn("Can't execute %s: %m", prog);
        return 0;
    }

    pid = fork();
    if (pid == -1) {
        error("Failed to create child process for %s: %m", prog);
        return -1;
    }
    if (pid == 0) {
        int new_fd;

        /* Leave the current location */
        (void) setsid();        /* No controlling tty. */
        (void) umask (S_IRWXG|S_IRWXO);
        (void) chdir ("/");     /* no current directory. */
        setuid(0);              /* set real UID = root */
        setgid(getegid());

        /* Ensure that nothing of our device environment is inherited. */
        sys_close();
        closelog();
        close (0);
        close (1);
        close (2);
        close (ttyfd);  /* tty interface to the ppp device */
        if (real_ttyfd >= 0)
            close(real_ttyfd);

        /* Don't pass handles to the PPP device, even by accident. */
        new_fd = open (_PATH_DEVNULL, O_RDWR);
        if (new_fd >= 0) {
            if (new_fd != 0) {
                dup2  (new_fd, 0); /* stdin <- /dev/null */
                close (new_fd);
            }
            dup2 (0, 1); /* stdout -> /dev/null */
            dup2 (0, 2); /* stderr -> /dev/null */
        }

#ifdef BSD
        /* Force the priority back to zero if pppd is running higher. */
        if (setpriority (PRIO_PROCESS, 0, 0) < 0)
            warn("can't reset priority to 0: %m"); 
#endif

        /* SysV recommends a second fork at this point. */

        /* run the program */
        execve(prog, args, script_env);
        if (must_exist || errno != ENOENT) {
            /* have to reopen the log, there's nowhere else
               for the message to go. */
            reopen_log();
            syslog(LOG_ERR, "Can't execute %s: %m", prog);
            closelog();
        }
        _exit(-1);
    }

    if (debug)
        dbglog("Script %s started (pid %d)", prog, pid);
    record_child(pid, prog, done, arg);

    return pid;
}


/*
 * record_child - add a child process to the list for reap_kids
 * to use.
 */
static void
record_child(pid, prog, done, arg)
    int pid;
    char *prog;
    void (*done) __P((void *));
    void *arg;
{
    struct subprocess *chp;

    ++n_children;

    chp = (struct subprocess *) malloc(sizeof(struct subprocess));
    if (chp == NULL) {
        warn("losing track of %s process", prog);
    } else {
        chp->pid = pid;
        chp->prog = prog;
        chp->done = done;
        chp->arg = arg;
        chp->next = children;
        children = chp;
    }
}


/*
 * reap_kids - get status from any dead child processes,
 * and log a message for abnormal terminations.
 */
static int
reap_kids(waitfor)
    int waitfor;
{
    int pid, status;
    struct subprocess *chp, **prevp;

    got_sigchld = 0;
    if (n_children == 0)
        return 0;
    while ((pid = waitpid(-1, &status, (waitfor? 0: WNOHANG))) != -1
           && pid != 0) {
        for (prevp = &children; (chp = *prevp) != NULL; prevp = &chp->next) {
            if (chp->pid == pid) {
                --n_children;
                *prevp = chp->next;
                break;
            }
        }
        if (WIFSIGNALED(status)) {
            warn("Child process %s (pid %d) terminated with signal %d",
                 (chp? chp->prog: "??"), pid, WTERMSIG(status));
        } else if (debug)
            dbglog("Script %s finished (pid %d), status = 0x%x",
                   (chp? chp->prog: "??"), pid, status);
        if (chp && chp->done)
            (*chp->done)(chp->arg);
        if (chp)
            free(chp);
    }
    if (pid == -1) {
        if (errno == ECHILD)
            return -1;
        if (errno != EINTR)
            error("Error waiting for child process: %m");
    }
    return 0;
}


/*
 * novm - log an error message saying we ran out of memory, and die.
 */
void
novm(msg)
    char *msg;
{
    fatal("Virtual memory exhausted allocating %s\n", msg);
}

/*
 * script_setenv - set an environment variable value to be used
 * for scripts that we run (e.g. ip-up, auth-up, etc.)
 */
void
script_setenv(var, value, iskey)
    char *var, *value;
    int iskey;
{
    size_t varl = strlen(var);
    size_t vl = varl + strlen(value) + 2;
    int i;
    char *p, *newstring;

    newstring = (char *) malloc(vl);
    if (newstring == 0)
        return;
    slprintf(newstring, vl, "%s=%s", var, value);

    /* check if this variable is already set */
    if (script_env != 0) {
        for (i = 0; (p = script_env[i]) != 0; ++i) {
            if (strncmp(p, var, varl) == 0 && p[varl] == '=') {
                if (iskey && pppdb != NULL) {
                    delete_db_key(p);
                    add_db_key(newstring);
                }
                free(p);
                script_env[i] = newstring;
                return;
            }
        }
    } else {
        /* no space allocated for script env. ptrs. yet */
        i = 0;
        script_env = (char **) malloc(16 * sizeof(char *));
        if (script_env == 0)
            return;
        s_env_nalloc = 16;
    }

    /* reallocate script_env with more space if needed */
    if (i + 1 >= s_env_nalloc) {
        int new_n = i + 17;
        char **newenv = (char **) realloc((void *)script_env,
                                          new_n * sizeof(char *));
        if (newenv == 0)
            return;
        script_env = newenv;
        s_env_nalloc = new_n;
    }

    script_env[i] = newstring;
    script_env[i+1] = 0;

    if (pppdb != NULL) {
        if (iskey)
            add_db_key(newstring);
        update_db_entry();
    }
}

/*
 * script_unsetenv - remove a variable from the environment
 * for scripts.
 */
void
script_unsetenv(var)
    char *var;
{
    int vl = strlen(var);
    int i;
    char *p;

    if (script_env == 0)
        return;
    for (i = 0; (p = script_env[i]) != 0; ++i) {
        if (strncmp(p, var, vl) == 0 && p[vl] == '=') {
            free(p);
            while ((script_env[i] = script_env[i+1]) != 0)
                ++i;
            break;
        }
    }
    if (pppdb != NULL)
        update_db_entry();
}

/*
 * update_db_entry - update our entry in the database.
 */
static void
update_db_entry()
{
    TDB_DATA key, dbuf;
    int vlen, i;
    char *p, *q, *vbuf;

    if (script_env == NULL)
        return;
    vlen = 0;
    for (i = 0; (p = script_env[i]) != 0; ++i)
        vlen += strlen(p) + 1;
    vbuf = malloc(vlen);
    if (vbuf == 0)
        novm("database entry");
    q = vbuf;
    for (i = 0; (p = script_env[i]) != 0; ++i)
        q += slprintf(q, vbuf + vlen - q, "%s;", p);

    key.dptr = db_key;
    key.dsize = strlen(db_key);
    dbuf.dptr = vbuf;
    dbuf.dsize = vlen;
    if (tdb_store(pppdb, key, dbuf, TDB_REPLACE))
        error("tdb_store failed: %s", tdb_error(pppdb));

}

/*
 * add_db_key - add a key that we can use to look up our database entry.
 */
static void
add_db_key(str)
    const char *str;
{
    TDB_DATA key, dbuf;

    key.dptr = (char *) str;
    key.dsize = strlen(str);
    dbuf.dptr = db_key;
    dbuf.dsize = strlen(db_key);
    if (tdb_store(pppdb, key, dbuf, TDB_REPLACE))
        error("tdb_store key failed: %s", tdb_error(pppdb));
}

/*
 * delete_db_key - delete a key for looking up our database entry.
 */
static void
delete_db_key(str)
    const char *str;
{
    TDB_DATA key;

    key.dptr = (char *) str;
    key.dsize = strlen(str);
    tdb_delete(pppdb, key);
}

/*
 * open_socket - establish a stream socket connection to the nominated
 * host and port.
 */
static int
open_socket(dest)
    char *dest;
{
    char *sep, *endp = NULL;
    int sock, port = -1;
    u_int32_t host;
    struct hostent *hent;
    struct sockaddr_in sad;

    /* parse host:port and resolve host to an IP address */
    sep = strchr(dest, ':');
    if (sep != NULL)
        port = strtol(sep+1, &endp, 10);
    if (port < 0 || endp == sep+1 || sep == dest) {
        error("Can't parse host:port for socket destination");
        return -1;
    }
    *sep = 0;
    host = inet_addr(dest);
    if (host == (u_int32_t) -1) {
        hent = gethostbyname(dest);
        if (hent == NULL) {
            error("%s: unknown host in socket option", dest);
            *sep = ':';
            return -1;
        }
        host = *(u_int32_t *)(hent->h_addr_list[0]);
    }
    *sep = ':';

    /* get a socket and connect it to the other end */
    sock = socket(PF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
        error("Can't create socket: %m");
        return -1;
    }
    memset(&sad, 0, sizeof(sad));
    sad.sin_family = AF_INET;
    sad.sin_port = htons(port);
    sad.sin_addr.s_addr = host;
    if (connect(sock, &sad, sizeof(sad)) < 0) {
        error("Can't connect to %s: %m", dest);
        close(sock);
        return -1;
    }

    return sock;
}

/*
 * start_charshunt - create a child process to run the character shunt.
 */
static int
start_charshunt(ifd, ofd)
    int ifd, ofd;
{
    int cpid;

    cpid = fork();
    if (cpid == -1) {
        error("Can't fork process for character shunt: %m");
        return 0;
    }
    if (cpid == 0) {
        /* child */
        close(pty_slave);
        setuid(uid);
        if (getuid() != uid)
            fatal("setuid failed");
        setgid(getgid());
        if (!nodetach)
            log_to_fd = -1;
        charshunt(ifd, ofd, record_file);
        exit(0);
    }
    charshunt_pid = cpid;
    close(pty_master);
    pty_master = -1;
    ttyfd = pty_slave;
    record_child(cpid, "pppd (charshunt)", charshunt_done, NULL);
    return 1;
}

static void
charshunt_done(arg)
    void *arg;
{
    charshunt_pid = 0;
}

/*
 * charshunt - the character shunt, which passes characters between
 * the pty master side and the serial port (or stdin/stdout).
 * This runs as the user (not as root).
 * (We assume ofd >= ifd which is true the way this gets called. :-).
 */
static void
charshunt(ifd, ofd, record_file)
    int ifd, ofd;
    char *record_file;
{
    int n, nfds;
    fd_set ready, writey;
    u_char *ibufp, *obufp;
    int nibuf, nobuf;
    int flags;
    int pty_readable, stdin_readable;
    struct timeval lasttime;
    FILE *recordf = NULL;
    int ilevel, olevel, max_level;
    struct timeval levelt, tout, *top;

    /*
     * Reset signal handlers.
     */
    signal(SIGHUP, SIG_IGN);            /* Hangup */
    signal(SIGINT, SIG_DFL);            /* Interrupt */
    signal(SIGTERM, SIG_DFL);           /* Terminate */
    signal(SIGCHLD, SIG_DFL);
    signal(SIGUSR1, SIG_DFL);
    signal(SIGUSR2, SIG_DFL);
    signal(SIGABRT, SIG_DFL);
    signal(SIGALRM, SIG_DFL);
    signal(SIGFPE, SIG_DFL);
    signal(SIGILL, SIG_DFL);
    signal(SIGPIPE, SIG_DFL);
    signal(SIGQUIT, SIG_DFL);
    signal(SIGSEGV, SIG_DFL);
#ifdef SIGBUS
    signal(SIGBUS, SIG_DFL);
#endif
#ifdef SIGEMT
    signal(SIGEMT, SIG_DFL);
#endif
#ifdef SIGPOLL
    signal(SIGPOLL, SIG_DFL);
#endif
#ifdef SIGPROF
    signal(SIGPROF, SIG_DFL);
#endif
#ifdef SIGSYS
    signal(SIGSYS, SIG_DFL);
#endif
#ifdef SIGTRAP
    signal(SIGTRAP, SIG_DFL);
#endif
#ifdef SIGVTALRM
    signal(SIGVTALRM, SIG_DFL);
#endif
#ifdef SIGXCPU
    signal(SIGXCPU, SIG_DFL);
#endif
#ifdef SIGXFSZ
    signal(SIGXFSZ, SIG_DFL);
#endif

    /*
     * Open the record file if required.
     */
    if (record_file != NULL) {
        recordf = fopen(record_file, "a");
        if (recordf == NULL)
            error("Couldn't create record file %s: %m", record_file);
    }

    /* set all the fds to non-blocking mode */
    flags = fcntl(pty_master, F_GETFL);
    if (flags == -1
        || fcntl(pty_master, F_SETFL, flags | O_NONBLOCK) == -1)
        warn("couldn't set pty master to nonblock: %m");
    flags = fcntl(ifd, F_GETFL);
    if (flags == -1
        || fcntl(ifd, F_SETFL, flags | O_NONBLOCK) == -1)
        warn("couldn't set %s to nonblock: %m", (ifd==0? "stdin": "tty"));
    if (ofd != ifd) {
        flags = fcntl(ofd, F_GETFL);
        if (flags == -1
            || fcntl(ofd, F_SETFL, flags | O_NONBLOCK) == -1)
            warn("couldn't set stdout to nonblock: %m");
    }

    nibuf = nobuf = 0;
    ibufp = obufp = NULL;
    pty_readable = stdin_readable = 1;

    ilevel = olevel = 0;
    gettimeofday(&levelt, NULL);
    if (max_data_rate) {
        max_level = max_data_rate / 10;
        if (max_level < 100)
            max_level = 100;
    } else
        max_level = sizeof(inpacket_buf) + 1;

    nfds = (ofd > pty_master? ofd: pty_master) + 1;
    if (recordf != NULL) {
        gettimeofday(&lasttime, NULL);
        putc(7, recordf);       /* put start marker */
        putc(lasttime.tv_sec >> 24, recordf);
        putc(lasttime.tv_sec >> 16, recordf);
        putc(lasttime.tv_sec >> 8, recordf);
        putc(lasttime.tv_sec, recordf);
        lasttime.tv_usec = 0;
    }

    while (nibuf != 0 || nobuf != 0 || pty_readable || stdin_readable) {
        top = 0;
        tout.tv_sec = 0;
        tout.tv_usec = 10000;
        FD_ZERO(&ready);
        FD_ZERO(&writey);
        if (nibuf != 0) {
            if (ilevel >= max_level)
                top = &tout;
            else
                FD_SET(pty_master, &writey);
        } else if (stdin_readable)
            FD_SET(ifd, &ready);
        if (nobuf != 0) {
            if (olevel >= max_level)
                top = &tout;
            else
                FD_SET(ofd, &writey);
        } else if (pty_readable)
            FD_SET(pty_master, &ready);
        if (select(nfds, &ready, &writey, NULL, top) < 0) {
            if (errno != EINTR)
                fatal("select");
            continue;
        }
        if (max_data_rate) {
            double dt;
            int nbt;
            struct timeval now;

            gettimeofday(&now, NULL);
            dt = (now.tv_sec - levelt.tv_sec
                  + (now.tv_usec - levelt.tv_usec) / 1e6);
            nbt = (int)(dt * max_data_rate);
            ilevel = (nbt < 0 || nbt > ilevel)? 0: ilevel - nbt;
            olevel = (nbt < 0 || nbt > olevel)? 0: olevel - nbt;
            levelt = now;
        } else
            ilevel = olevel = 0;
        if (FD_ISSET(ifd, &ready)) {
            ibufp = inpacket_buf;
            nibuf = read(ifd, ibufp, sizeof(inpacket_buf));
            if (nibuf < 0 && errno == EIO)
                nibuf = 0;
            if (nibuf < 0) {
                if (!(errno == EINTR || errno == EAGAIN)) {
                    error("Error reading standard input: %m");
                    break;
                }
                nibuf = 0;
            } else if (nibuf == 0) {
                /* end of file from stdin */
                stdin_readable = 0;
                /* do a 0-length write, hopefully this will generate
                   an EOF (hangup) on the slave side. */
                write(pty_master, inpacket_buf, 0);
                if (recordf)
                    if (!record_write(recordf, 4, NULL, 0, &lasttime))
                        recordf = NULL;
            } else {
                FD_SET(pty_master, &writey);
                if (recordf)
                    if (!record_write(recordf, 2, ibufp, nibuf, &lasttime))
                        recordf = NULL;
            }
        }
        if (FD_ISSET(pty_master, &ready)) {
            obufp = outpacket_buf;
            nobuf = read(pty_master, obufp, sizeof(outpacket_buf));
            if (nobuf < 0 && errno == EIO)
                nobuf = 0;
            if (nobuf < 0) {
                if (!(errno == EINTR || errno == EAGAIN)) {
                    error("Error reading pseudo-tty master: %m");
                    break;
                }
                nobuf = 0;
            } else if (nobuf == 0) {
                /* end of file from the pty - slave side has closed */
                pty_readable = 0;
                stdin_readable = 0;     /* pty is not writable now */
                nibuf = 0;
                close(ofd);
                if (recordf)
                    if (!record_write(recordf, 3, NULL, 0, &lasttime))
                        recordf = NULL;
            } else {
                FD_SET(ofd, &writey);
                if (recordf)
                    if (!record_write(recordf, 1, obufp, nobuf, &lasttime))
                        recordf = NULL;
            }
        }
        if (FD_ISSET(ofd, &writey)) {
            n = nobuf;
            if (olevel + n > max_level)
                n = max_level - olevel;
            n = write(ofd, obufp, n);
            if (n < 0) {
                if (errno != EIO) {
                    error("Error writing standard output: %m");
                    break;
                }
                pty_readable = 0;
                nobuf = 0;
            } else {
                obufp += n;
                nobuf -= n;
                olevel += n;
            }
        }
        if (FD_ISSET(pty_master, &writey)) {
            n = nibuf;
            if (ilevel + n > max_level)
                n = max_level - ilevel;
            n = write(pty_master, ibufp, n);
            if (n < 0) {
                if (errno != EIO) {
                    error("Error writing pseudo-tty master: %m");
                    break;
                }
                stdin_readable = 0;
                nibuf = 0;
            } else {
                ibufp += n;
                nibuf -= n;
                ilevel += n;
            }
        }
    }
    exit(0);
}

static int
record_write(f, code, buf, nb, tp)
    FILE *f;
    int code;
    u_char *buf;
    int nb;
    struct timeval *tp;
{
    struct timeval now;
    int diff;

    gettimeofday(&now, NULL);
    now.tv_usec /= 100000;      /* actually 1/10 s, not usec now */
    diff = (now.tv_sec - tp->tv_sec) * 10 + (now.tv_usec - tp->tv_usec);
    if (diff > 0) {
        if (diff > 255) {
            putc(5, f);
            putc(diff >> 24, f);
            putc(diff >> 16, f);
            putc(diff >> 8, f);
            putc(diff, f);
        } else {
            putc(6, f);
            putc(diff, f);
        }
        *tp = now;
    }
    putc(code, f);
    if (buf != NULL) {
        putc(nb >> 8, f);
        putc(nb, f);
        fwrite(buf, nb, 1, f);
    }
    fflush(f);
    if (ferror(f)) {
        error("Error writing record file: %m");
        return 0;
    }
    return 1;
}