tmp.c

/*
 * main.c - Point-to-Point Protocol main module
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      [phone], fax: [phone]
 *      [e-mail]
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF 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.
 *
 * Copyright (c) 1999-2004 Paul Mackerras. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. The name(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 3. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <[e-mail]>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
 * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF 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.
 */

#define RCSID "$Id: main.c,v 1.156 2008/06/23 11:47:18 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-new.h"
#include "eap.h"
#include "ccp.h"
#include "ecp.h"
#include "pathnames.h"

#ifdef USE_TDB
#include "tdb.h"
#endif

#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 */

struct channel *the_channel;

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 */
char ppp_devnam[MAXPATHLEN]; /* name of PPP tty (maybe ttypx) */
uid_t uid;   /* Our real user-id */
struct notifier *pidchange = NULL;
struct notifier *phasechange = NULL;
struct notifier *exitnotify = NULL;
struct notifier *sigreceived = NULL;
struct notifier *fork_notifier = NULL;

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 */
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 */
int ppp_session_number;  /* Session number, for channels with such a
       concept (eg PPPoE) */
int childwait_done;  /* have timed out waiting for children */

#ifdef USE_TDB
TDB_CONTEXT *pppdb;  /* database for storing status etc. */
#endif

char db_key[32];

int ( *holdoff_hook ) __P ( ( void ) ) = NULL;
int ( *new_phase_hook ) __P ( ( int ) ) = NULL;
void ( *snoop_recv_hook ) __P ( ( unsigned char *p, int len ) ) = NULL;
void ( *snoop_send_hook ) __P ( ( unsigned char *p, int len ) ) = NULL;

static int conn_running; /* we have a [dis]connector running */
static int fd_loop;  /* fd for getting demand-dial packets */

int fd_devnull;   /* fd for /dev/null */
int devfd = -1;   /* fd of underlying device */
int fd_ppp = -1;  /* fd for talking PPP */
int phase;   /* where the link is at */
int kill_link;
int asked_to_quit;
int open_ccp_flag;
int listen_time;
int got_sigusr2;
int got_sigterm;
int got_sighup;

static sigset_t signals_handled;
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 */

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. */

static struct pppd_stats old_link_stats;
struct pppd_stats link_stats;
unsigned link_connect_time;
int link_stats_valid;

int error_count;

bool bundle_eof;
bool bundle_terminating;

/*
 * 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;
    int  killable;
    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 ( ( int pid ) );
static void create_linkpidfile __P ( ( int pid ) );
static void cleanup __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 void forget_child __P ( ( int pid, int status ) );
static int reap_kids __P ( ( void ) );
static void childwait_end __P ( ( void * ) );

#ifdef USE_TDB
static void update_db_entry __P ( ( void ) );
static void add_db_key __P ( ( const char * ) );
static void delete_db_key __P ( ( const char * ) );
static void cleanup_db __P ( ( void ) );
#endif

static void handle_events __P ( ( void ) );
void print_link_stats __P ( ( void ) );

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,
    &ecp_protent,
#ifdef IPX_CHANGE
    &ipxcp_protent,
#endif
#ifdef AT_CHANGE
    &atcp_protent,
#endif
    &eap_protent,
    NULL
};

/*
 * If PPP_DRV_NAME is not defined, use the default "ppp" as the device name.
 */
#if !defined(PPP_DRV_NAME)
#define PPP_DRV_NAME "ppp"
#endif /* !defined(PPP_DRV_NAME) */

int main ( int argc, char *argv[] )
{
    int i, t;
    char *p;
    struct passwd *pw;
    struct protent *protp;
    char numbuf[16];

    link_stats_valid = 0;
    new_phase ( PHASE_INITIALIZE );

    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 each protocol.
    */
    for ( i = 0; ( protp = protocols[i] ) != NULL; ++i )
    {
        ( *protp->init ) ( 0 );
    }

    /*
    * Initialize the default channel.
    */
    tty_init();

    progname = *argv;

    /*
    * Parse, in order, the system options file, the user's options file,
    * and the command line arguments.
    */
    if ( !options_from_file ( _PATH_SYSOPTIONS, !privileged, 0, 1 ) || !options_from_user() || !parse_args ( argc - 1, argv + 1 ) )
    {
        exit ( EXIT_OPTION_ERROR );
    }

    /* add by wangchenxi */
    getchar();

    devnam_fixed = 1;  /* can no longer change device name */

    /*
    * Work out the device name, if it hasn't already been specified,
    * and parse the tty's options file.
    */
    if ( the_channel->process_extra_options )
    {
        ( *the_channel->process_extra_options ) ();
    }

    if ( debug )
    {
        setlogmask ( LOG_UPTO ( LOG_DEBUG ) );
    }

    /*
    * 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 ( "%s", no_ppp_msg );
        exit ( EXIT_NO_KERNEL_SUPPORT );
    }

    /*
    * Check that the options given are valid and consistent.
    */
    check_options();

    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 ( the_channel->check_options )
    {
        ( *the_channel->check_options ) ();
    }

    if ( dump_options || dryrun )
    {
        init_pr_log ( NULL, LOG_INFO );
        print_options ( pr_log, NULL );
        end_pr_log();
    }

    if ( dryrun )
    {
        die ( 0 );
    }

    /* Make sure fds 0, 1, 2 are open to somewhere. */
    fd_devnull = open ( _PATH_DEVNULL, O_RDWR );

    if ( fd_devnull < 0 )
    {
        fatal ( "Couldn't open %s: %m", _PATH_DEVNULL );
    }

    while ( fd_devnull <= 2 )
    {
        i = dup ( fd_devnull );

        if ( i < 0 )
            fatal ( "Critical shortage of file descriptors: dup failed: %m" );

        fd_devnull = i;
    }

    /*
    * Initialize system-dependent stuff.
    */
    sys_init();

#ifdef USE_TDB
    pppdb = tdb_open ( _PATH_PPPDB, 0, 0, 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;
        }
    }

#endif

    /*
    * 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 started by %s, uid %d", VERSION, p, uid );
    script_setenv ( "PPPLOGNAME", p, 0 );

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

    slprintf ( numbuf, sizeof ( numbuf ), "%d", getpid() );
    script_setenv ( "PPPD_PID", numbuf, 1 );

    setup_signals();

    create_linkpidfile ( getpid() );

    waiting = 0;

    /*
    * 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 ( ;; )
    {
        bundle_eof = 0;
        bundle_terminating = 0;
        listen_time = 0;
        need_holdoff = 1;
        devfd = -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.
            */
            new_phase ( PHASE_DORMANT );
            demand_unblock();
            add_fd ( fd_loop );

            for ( ;; )
            {
                handle_events();

                if ( asked_to_quit )
                    break;

                if ( get_loop_output() )
                    break;
            }

            remove_fd ( fd_loop );

            if ( asked_to_quit )
                break;

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

        gettimeofday ( &start_time, NULL );
        script_unsetenv ( "CONNECT_TIME" );
        script_unsetenv ( "BYTES_SENT" );
        script_unsetenv ( "BYTES_RCVD" );

        lcp_open ( 0 );  /* Start protocol */
        start_link ( 0 );

        while ( phase != PHASE_DEAD )
        {
            handle_events();
            get_input();

            if ( kill_link )
                lcp_close ( 0, "User request" );

            if ( asked_to_quit )
            {
                bundle_terminating = 1;

                if ( phase == PHASE_MASTER )
                    mp_bundle_terminated();
            }

            if ( open_ccp_flag )
            {
                if ( phase == PHASE_NETWORK || phase == PHASE_RUNNING )
                {
                    ccp_fsm[0].flags = OPT_RESTART; /* clears OPT_SILENT */
                    ( *ccp_protent.open ) ( 0 );
                }
            }
        }

        /* restore FSMs to original state */
        lcp_close ( 0, "" );

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

        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
            {
                handle_events();

                if ( kill_link )
                    new_phase ( PHASE_DORMANT ); /* allow signal to end holdoff */
            }
            while ( phase == PHASE_HOLDOFF );

            if ( !persist )
                break;
        }
    }

    /* Wait for scripts to finish */
    reap_kids();

    if ( n_children > 0 )
    {
        if ( child_wait > 0 )
            TIMEOUT ( childwait_end, NULL, child_wait );

        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 );
        }

        while ( n_children > 0 && !childwait_done )
        {
            handle_events();

            if ( kill_link && !childwait_done )
                childwait_end ( NULL );
        }
    }

    die ( status );
    return 0;
}

/*
 * handle_events - wait for something to happen and respond to it.
 */
static void handle_events()
{
    struct timeval timo;

    kill_link = open_ccp_flag = 0;

    if ( sigsetjmp ( sigjmp, 1 ) == 0 )
    {
        sigprocmask ( SIG_BLOCK, &signals_handled, NULL );

        if ( got_sighup || got_sigterm || got_sigusr2 || got_sigchld )
        {
            sigprocmask ( SIG_UNBLOCK, &signals_handled, NULL );
        }
        else
        {
            waiting = 1;
            sigprocmask ( SIG_UNBLOCK, &signals_handled, NULL );
            wait_input ( timeleft ( &timo ) );
        }
    }

    waiting = 0;
    calltimeout();

    if ( got_sighup )
    {
        info ( "Hangup (SIGHUP)" );
        kill_link = 1;
        got_sighup = 0;

        if ( status != EXIT_HANGUP )
            status = EXIT_USER_REQUEST;
    }

    if ( got_sigterm )
    {
        info ( "Terminating on signal %d", got_sigterm );
        kill_link = 1;
        asked_to_quit = 1;
        persist = 0;
        status = EXIT_USER_REQUEST;
        got_sigterm = 0;
    }

    if ( got_sigchld )
    {
        got_sigchld = 0;
        reap_kids(); /* Don't leave dead kids lying around */
    }

    if ( got_sigusr2 )
    {
        open_ccp_flag = 1;
        got_sigusr2 = 0;
    }
}

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

    /*
     * 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 ( &signals_handled );
    sigaddset ( &signals_handled, SIGHUP );
    sigaddset ( &signals_handled, SIGINT );
    sigaddset ( &signals_handled, SIGTERM );
    sigaddset ( &signals_handled, SIGCHLD );
    sigaddset ( &signals_handled, 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 = signals_handled;
    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 ( int iskey )
{
    info ( "Using interface %s%d", PPP_DRV_NAME, ifunit );
    slprintf ( ifname, sizeof ( ifname ), "%s%d", PPP_DRV_NAME, ifunit );
    script_setenv ( "IFNAME", ifname, iskey );

    if ( iskey )
    {
        create_pidfile ( getpid() ); /* write pid to file */
        create_linkpidfile ( getpid() );
    }
}

/*
 * detach - detach us from the controlling terminal.
 */
void detach()
{
    int pid;
    char numbuf[16];
    int pipefd[2];

    if ( detached )
        return;

    if ( pipe ( pipefd ) == -1 )
        pipefd[0] = pipefd[1] = -1;

    if ( ( pid = fork() ) < 0 )
    {
        error ( "Couldn't detach (fork failed: %m)" );
        die ( 1 );   /* or just return? */
    }

    if ( pid != 0 )
    {
        /* parent */
        notify ( pidchange, pid );

        /* update pid files if they have been written already */
        if ( pidfilename[0] )
            create_pidfile ( pid );

        if ( linkpidfile[0] )
            create_linkpidfile ( pid );

        exit ( 0 );  /* parent dies */
    }

    setsid();
    chdir ( "/" );
    dup2 ( fd_devnull, 0 );
    dup2 ( fd_devnull, 1 );
    dup2 ( fd_devnull, 2 );
    detached = 1;

    if ( log_default )
        log_to_fd = -1;

    slprintf ( numbuf, sizeof ( numbuf ), "%d", getpid() );
    script_setenv ( "PPPD_PID", numbuf, 1 );

    /* wait for parent to finish updating pid & lock files and die */
    close ( pipefd[1] );
    complete_read ( pipefd[0], numbuf, 1 );
    close ( pipefd[0] );
}

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

/*
 * Create a file containing our process ID.
 */
static void create_pidfile ( pid )
int pid;
{
    FILE *pidfile;

    slprintf ( pidfilename, sizeof ( pidfilename ), "%s%s.pid",
               _PATH_VARRUN, ifname );

    if ( ( pidfile = fopen ( pidfilename, "w" ) ) != NULL )
    {
        fprintf ( pidfile, "%d/n", pid );
        ( void ) fclose ( pidfile );
    }
    else
    {
        error ( "Failed to create pid file %s: %m", pidfilename );
        pidfilename[0] = 0;
    }
}

void create_linkpidfile ( pid )
int pid;
{
    FILE *pidfile;

    if ( linkname[0] == 0 )
        return;

    script_setenv ( "LINKNAME", linkname, 1 );
    slprintf ( linkpidfile, sizeof ( linkpidfile ), "%sppp-%s.pid",
               _PATH_VARRUN, linkname );

    if ( ( pidfile = fopen ( linkpidfile, "w" ) ) != NULL )
    {
        fprintf ( pidfile, "%d/n", pid );

        if ( ifname[0] )
            fprintf ( pidfile, "%s/n", ifname );

        ( void ) fclose ( pidfile );
    }
    else
    {
        error ( "Failed to create pid file %s: %m", linkpidfile );
        linkpidfile[0] = 0;
    }
}

/*
 * remove_pidfile - remove our pid files
 */
void remove_pidfiles()
{
    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;
}

/*
 * holdoff_end - called via a timeout when the holdoff period ends.
 */
static void holdoff_end ( 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" },
    { 0x51, "KNX Bridging Data" },
    { 0x53, "Encryption" },
    { 0x55, "Individual Link Encryption" },
    { 0x57, "IPv6" },
    { 0x59, "PPP Muxing" },
    { 0x5b, "Vendor-Specific Network Protocol" },
    { 0x61, "RTP IPHC Full Header" },
    { 0x63, "RTP IPHC Compressed TCP" },
    { 0x65, "RTP IPHC Compressed non-TCP" },
    { 0x67, "RTP IPHC Compressed UDP 8" },
    { 0x69, "RTP IPHC Compressed RTP 8" },
    { 0x6f, "Stampede Bridging" },
    { 0x73, "MP+" },
    { 0xc1, "NTCITS IPI" },
    { 0xfb, "single-link compression" },
    { 0xfd, "Compressed Datagram" },
    { 0x0201, "802.1d Hello Packets" },
    { 0x0203, "IBM Source Routing BPDU" },
    { 0x0205, "DEC LANBridge100 Spanning Tree" },
    { 0x0207, "Cisco Discovery Protocol" },
    { 0x0209, "Netcs Twin Routing" },
    { 0x020b, "STP - Scheduled Transfer Protocol" },
    { 0x020d, "EDP - Extreme Discovery Protocol" },
    { 0x0211, "Optical Supervisory Channel Protocol" },
    { 0x0213, "Optical Supervisory Channel Protocol" },
    { 0x0231, "Luxcom" },
    { 0x0233, "Sigma Network Systems" },
    { 0x0235, "Apple Client Server Protocol" },
    { 0x0281, "MPLS Unicast" },
    { 0x0283, "MPLS Multicast" },
    { 0x0285, "IEEE p1284.4 standard - data packets" },
    { 0x0287, "ETSI TETRA Network Protocol Type 1" },
    { 0x0289, "Multichannel Flow Treatment Protocol" },
    { 0x2063, "RTP IPHC Compressed TCP No Delta" },
    { 0x2065, "RTP IPHC Context State" },
    { 0x2067, "RTP IPHC Compressed UDP 16" },
    { 0x2069, "RTP IPHC Compressed RTP 16" },
    { 0x4001, "Cray Communications Control Protocol" },
    { 0x4003, "CDPD Mobile Network Registration Protocol" },
    { 0x4005, "Expand accelerator protocol" },
    { 0x4007, "ODSICP NCP" },
    { 0x4009, "DOCSIS DLL" },
    { 0x400B, "Cetacean Network Detection Protocol" },
    { 0x4021, "Stacker LZS" },
    { 0x4023, "RefTek Protocol" },
    { 0x4025, "Fibre Channel" },
    { 0x4027, "EMIT Protocols" },
    { 0x405b, "Vendor-Specific Protocol (VSP)" },
    { 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" },
    { 0x8051, "KNX Bridging Control Protocol" },
    { 0x8053, "Encryption Control Protocol" },
    { 0x8055, "Individual Link Encryption Control Protocol" },
    { 0x8057, "IPv6 Control Protocol" },
    { 0x8059, "PPP Muxing Control Protocol" },
    { 0x805b, "Vendor-Specific Network Control Protocol (VSNCP)" },
    { 0x806f, "Stampede Bridging Control Protocol" },
    { 0x8073, "MP+ Control Protocol" },
    { 0x80c1, "NTCITS IPI Control Protocol" },
    { 0x80fb, "Single Link Compression Control Protocol" },
    { 0x80fd, "Compression Control Protocol" },
    { 0x8207, "Cisco Discovery Protocol Control" },
    { 0x8209, "Netcs Twin Routing" },
    { 0x820b, "STP - Control Protocol" },
    { 0x820d, "EDPCP - Extreme Discovery Protocol Ctrl Prtcl" },
    { 0x8235, "Apple Client Server Protocol Control" },
    { 0x8281, "MPLSCP" },
    { 0x8285, "IEEE p1284.4 standard - Protocol Control" },
    { 0x8287, "ETSI TETRA TNP1 Control Protocol" },
    { 0x8289, "Multichannel Flow Treatment Protocol" },
    { 0xc021, "Link Control Protocol" },
    { 0xc023, "Password Authentication Protocol" },
    { 0xc025, "Link Quality Report" },
    { 0xc027, "Shiva Password Authentication Protocol" },
    { 0xc029, "CallBack Control Protocol (CBCP)" },
    { 0xc02b, "BACP Bandwidth Allocation Control Protocol" },
    { 0xc02d, "BAP" },
    { 0xc05b, "Vendor-Specific Authentication Protocol (VSAP)" },
    { 0xc081, "Container Control Protocol" },
    { 0xc223, "Challenge Handshake Authentication Protocol" },
    { 0xc225, "RSA Authentication Protocol" },
    { 0xc227, "Extensible Authentication Protocol" },
    { 0xc229, "Mitsubishi Security Info Exch Ptcl (SIEP)" },
    { 0xc26f, "Stampede Bridging Authorization Protocol" },
    { 0xc281, "Proprietary Authentication Protocol" },
    { 0xc283, "Proprietary Authentication Protocol" },
    { 0xc481, "Proprietary Node ID Authentication Protocol" },
    { 0, NULL },
};

/*
 * protocol_name - find a name for a PPP protocol.
 */
const char * protocol_name ( 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 )
    {
        if ( bundle_eof && multilink_master )
        {
            notice ( "Last channel has disconnected" );
            mp_bundle_terminated();
            return;
        }

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

    if ( len < PPP_HDRLEN )
    {
        dbglog ( "received short packet:%.*B", len, p );
        return;
    }

    dump_packet ( "rcvd", p, len );

    if ( snoop_recv_hook ) snoop_recv_hook ( p, len );

    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 )
    {
        dbglog ( "Discarded 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 ||
                   protocol == PPP_EAP ) )
    {
        dbglog ( "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 );
}

/*
 * ppp_send_config - configure the transmit-side characteristics of
 * the ppp interface.  Returns -1, indicating an error, if the channel
 * send_config procedure called error() (or incremented error_count
 * itself), otherwise 0.
 */
int ppp_send_config ( int unit, int mtu, u_int32_t accm, int pcomp, int accomp )
{
    int errs;

    if ( the_channel->send_config == NULL )
        return 0;

    errs = error_count;
    ( *the_channel->send_config ) ( mtu, accm, pcomp, accomp );
    return ( error_count != errs ) ? -1 : 0;
}

/*
 * ppp_recv_config - configure the receive-side characteristics of
 * the ppp interface.  Returns -1, indicating an error, if the channel
 * recv_config procedure called error() (or incremented error_count
 * itself), otherwise 0.
 */
int ppp_recv_config ( int unit, int mru, u_int32_t accm, int pcomp, int accomp )
{
    int errs;

    if ( the_channel->recv_config == NULL )
        return 0;

    errs = error_count;
    ( *the_channel->recv_config ) ( mru, accm, pcomp, accomp );
    return ( error_count != errs ) ? -1 : 0;
}

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

    if ( new_phase_hook )
        ( *new_phase_hook ) ( p );

    notify ( phasechange, p );
}

/*
 * die - clean up state and exit with the specified status.
 */
void die ( int status )
{
    if ( !doing_multilink || multilink_master )
        print_link_stats();

    cleanup();
    notify ( exitnotify, status );
    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 )
        the_channel->disestablish_ppp ( devfd );

    if ( the_channel->cleanup )
        ( *the_channel->cleanup ) ();

    remove_pidfiles();

#ifdef USE_TDB

    if ( pppdb != NULL )
        cleanup_db();

#endif

}

void print_link_stats()
{
    /*
    * 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 %u bytes, received %u bytes.",
               link_stats.bytes_out, link_stats.bytes_in );
        link_stats_valid = 0;
    }
}

/*
 * reset_link_stats - "reset" stats when link goes up.
 */
void reset_link_stats ( int u )
{
    if ( !get_ppp_stats ( u, &old_link_stats ) )
        return;

    gettimeofday ( &start_time, NULL );
}

/*
 * update_link_stats - get stats at link termination.
 */
void update_link_stats ( 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;

    link_stats.bytes_in  -= old_link_stats.bytes_in;
    link_stats.bytes_out -= old_link_stats.bytes_out;
    link_stats.pkts_in   -= old_link_stats.pkts_in;
    link_stats.pkts_out  -= old_link_stats.pkts_out;

    slprintf ( numbuf, sizeof ( numbuf ), "%u", link_connect_time );
    script_setenv ( "CONNECT_TIME", numbuf, 0 );
    slprintf ( numbuf, sizeof ( numbuf ), "%u", link_stats.bytes_out );
    script_setenv ( "BYTES_SENT", numbuf, 0 );
    slprintf ( numbuf, sizeof ( numbuf ), "%u", 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.
 */
void timeout ( void ( *func ) __P ( ( void * ) ), void *arg, int secs, int usecs )
{
    struct callout *newp, *p, **pp;

    /*
     * 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 + secs;
    newp->c_time.tv_usec = timenow.tv_usec + usecs;

    if ( newp->c_time.tv_usec >= 1000000 )
    {
        newp->c_time.tv_sec += newp->c_time.tv_usec / 1000000;
        newp->c_time.tv_usec %= 1000000;
    }

    /*
     * 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 ( void ( *func ) __P ( ( void * ) ), void *arg )
{
    struct callout **copp, *freep;

    /*
     * 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 ( 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.
 * We assume that sig is currently blocked.
 */
static void kill_my_pg ( int sig )
{
    struct sigaction act, oldact;
    struct subprocess *chp;

    if ( !detached )
    {
        /*
        * There might be other things in our process group that we
        * didn't start that would get hit if we did a kill(0), so
        * just send the signal individually to our children.
        */
        for ( chp = children; chp != NULL; chp = chp->next )
            if ( chp->killable )
                kill ( chp->pid, sig );

        return;
    }

    /* We've done a setsid(), so we can just use a kill(0) */
    sigemptyset ( &act.sa_mask );  /* unnecessary in fact */
    act.sa_handler = SIG_IGN;
    act.sa_flags = 0;
    kill ( 0, sig );
    /*
    * The kill() above made the signal pending for us, as well as
    * the rest of our process group, but we don't want it delivered
    * to us.  It is blocked at the moment.  Setting it to be ignored
    * will cause the pending signal to be discarded.  If we did the
    * kill() after setting the signal to be ignored, it is unspecified
    * (by POSIX) whether the signal is immediately discarded or left
    * pending, and in fact Linux would leave it pending, and so it
    * would be delivered after the current signal handler exits,
    * leading to an infinite loop.
    */
    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 ( int sig )
{
    /* can't log a message here, it can deadlock */
    got_sighup = 1;

    if ( conn_running )
    {
        /* Send the signal to the [dis]connector process(es) also */
        kill_my_pg ( sig );
    }

    notify ( sigreceived, 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 ( int sig )
{
    /* can't log a message here, it can deadlock */
    got_sigterm = sig;

    if ( conn_running )
    {
        /* Send the signal to the [dis]connector process(es) also */
        kill_my_pg ( sig );
    }

    notify ( sigreceived, 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 ( int sig )
{
    got_sigchld = 1;

    if ( waiting )
        siglongjmp ( sigjmp, 1 );
}

/*
 * toggle_debug - Catch SIGUSR1 signal.
 *
 * Toggle debug flag.
 */
/*ARGSUSED*/
static void toggle_debug ( 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 ( int sig )
{
    got_sigusr2 = 1;

    if ( waiting )
        siglongjmp ( sigjmp, 1 );
}

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

    if ( crashed )
        _exit ( 127 );

    crashed = 1;
    error ( "Fatal signal %d", sig );

    if ( conn_running )
        kill_my_pg ( SIGTERM );

    notify ( sigreceived, sig );
    die ( 127 );
}

/*
 * safe_fork - Create a child process.  The child closes all the
 * file descriptors that we don't want to leak to a script.
 * The parent waits for the child to do this before returning.
 * This also arranges for the specified fds to be dup'd to
 * fds 0, 1, 2 in the child.
 */
pid_t safe_fork ( int infd, int outfd, int errfd )
{
    pid_t pid;
    int fd, pipefd[2];
    char buf[1];

    /* make sure fds 0, 1, 2 are occupied (probably not necessary) */
    while ( ( fd = dup ( fd_devnull ) ) >= 0 )
    {
        if ( fd > 2 )
        {
            close ( fd );
            break;
        }
    }

    if ( pipe ( pipefd ) == -1 )
        pipefd[0] = pipefd[1] = -1;

    pid = fork();

    if ( pid < 0 )
    {
        error ( "fork failed: %m" );
        return -1;
    }

    if ( pid > 0 )
    {
        /* parent */
        close ( pipefd[1] );
        /* this read() blocks until the close(pipefd[1]) below */
        complete_read ( pipefd[0], buf, 1 );
        close ( pipefd[0] );
        return pid;
    }

    /* Executing in the child */
    sys_close();
#ifdef USE_TDB
    tdb_close ( pppdb );
#endif

    /* make sure infd, outfd and errfd won't get tromped on below */
    if ( infd == 1 || infd == 2 )
        infd = dup ( infd );

    if ( outfd == 0 || outfd == 2 )
        outfd = dup ( outfd );

    if ( errfd == 0 || errfd == 1 )
        errfd = dup ( errfd );

    closelog();

    /* dup the in, out, err fds to 0, 1, 2 */
    if ( infd != 0 )
        dup2 ( infd, 0 );

    if ( outfd != 1 )
        dup2 ( outfd, 1 );

    if ( errfd != 2 )
        dup2 ( errfd, 2 );

    if ( log_to_fd > 2 )
        close ( log_to_fd );

    if ( the_channel->close )
        ( *the_channel->close ) ();
    else
        close ( devfd ); /* some plugins don't have a close function */

    close ( fd_ppp );
    close ( fd_devnull );

    if ( infd != 0 )
        close ( infd );

    if ( outfd != 1 )
        close ( outfd );

    if ( errfd != 2 )
        close ( errfd );

    notify ( fork_notifier, 0 );
    close ( pipefd[0] );
    /* this close unblocks the read() call above in the parent */
    close ( pipefd[1] );

    return 0;
}

/*
 * device_script - run a program to talk to the specified fds
 * (e.g. to run the connector or disconnector script).
 * stderr gets connected to the log fd or to the _PATH_CONNERRS file.
 */
int device_script ( char *program, int in, int out, int dont_wait )
{
    int pid;
    int status = -1;
    int errfd;

    if ( log_to_fd >= 0 )
        errfd = log_to_fd;
    else
        errfd = open ( _PATH_CONNERRS, O_WRONLY | O_APPEND | O_CREAT, 0600 );

    ++conn_running;
    pid = safe_fork ( in, out, errfd );

    if ( pid != 0 && log_to_fd < 0 )
        close ( errfd );

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

    if ( pid != 0 )
    {
        record_child ( pid, program, NULL, NULL, 1 );
        status = 0;

        if ( !dont_wait )
        {
            while ( waitpid ( pid, &status, 0 ) < 0 )
            {
                if ( errno == EINTR )
                    continue;

                fatal ( "error waiting for (dis)connection process: %m" );
            }

            forget_child ( pid, status );
            --conn_running;
        }

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

    /* here we are executing in the child */

    setgid ( getgid() );
    setuid ( uid );

    if ( getuid() != uid )
    {
        fprintf ( stderr, "pppd: setuid failed/n" );
        exit ( 1 );
    }

    execl ( "/bin/sh", "sh", "-c", program, ( char * ) 0 );
    perror ( "pppd: could not exec /bin/sh" );
    exit ( 99 );
    /* NOTREACHED */
}

/*
 * run_program - execute a program with given arguments,
 * but don't wait for it unless wait is non-zero.
 * 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 ( char *prog, char **args, int must_exist, void ( *done ) __P ( ( void * ) ), void *arg, int wait )
{
    int pid, status;
    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 = safe_fork ( fd_devnull, fd_devnull, fd_devnull );

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

    if ( pid != 0 )
    {
        if ( debug )
            dbglog ( "Script %s started (pid %d)", prog, pid );

        record_child ( pid, prog, done, arg, 0 );

        if ( wait )
        {
            while ( waitpid ( pid, &status, 0 ) < 0 )
            {
                if ( errno == EINTR )
                    continue;

                fatal ( "error waiting for script %s: %m", prog );
            }

            forget_child ( pid, status );
        }

        return pid;
    }

    /* 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() );

#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

    /* 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 );
}

/*
 * record_child - add a child process to the list for reap_kids
 * to use.
 */
void record_child ( int pid, char *prog, void ( *done ) __P ( ( void * ) ), void *arg, int killable )
//int pid;
//char *prog;
//void ( *done ) __P ( ( void * ) );
//void *arg;
//int killable;
{
    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;
        chp->killable = killable;
        children = chp;
    }
}

/*
 * childwait_end - we got fed up waiting for the child processes to
 * exit, send them all a SIGTERM.
 */
static void childwait_end ( void *arg )
{
    struct subprocess *chp;

    for ( chp = children; chp != NULL; chp = chp->next )
    {
        if ( debug )
            dbglog ( "sending SIGTERM to process %d", chp->pid );

        kill ( chp->pid, SIGTERM );
    }

    childwait_done = 1;
}

/*
 * forget_child - clean up after a dead child
 */
static void forget_child ( int pid, int status )
{
    struct subprocess *chp, **prevp;

    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,
                 WIFEXITED ( status ) ? WEXITSTATUS ( status ) : status );

    if ( chp && chp->done )
        ( *chp->done ) ( chp->arg );

    if ( chp )
        free ( chp );
}

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

    if ( n_children == 0 )
        return 0;

    while ( ( pid = waitpid ( -1, &status, WNOHANG ) ) != -1 && pid != 0 )
    {
        forget_child ( pid, status );
    }

    if ( pid == -1 )
    {
        if ( errno == ECHILD )
            return -1;

        if ( errno != EINTR )
            error ( "Error waiting for child process: %m" );
    }

    return 0;
}

/*
 * add_notifier - add a new function to be called when something happens.
 */
void add_notifier ( struct notifier **notif, notify_func func, void *arg )
{
    struct notifier *np;

    np = malloc ( sizeof ( struct notifier ) );

    if ( np == 0 )
    {
        novm ( "notifier struct" );
    }

    np->next = *notif;
    np->func = func;
    np->arg = arg;
    *notif = np;
}

/*
 * remove_notifier - remove a function from the list of things to
 * be called when something happens.
 */
void remove_notifier ( struct notifier **notif, notify_func func, void *arg )
{
    struct notifier *np;

    for ( ; ( np = *notif ) != 0; notif = &np->next )
    {
        if ( np->func == func && np->arg == arg )
        {
            *notif = np->next;
            free ( np );
            break;
        }
    }
}

/*
 * notify - call a set of functions registered with add_notifier.
 */
void notify ( struct notifier *notif, int val )
{
    struct notifier *np;

    while ( ( np = notif ) != 0 )
    {
        notif = np->next;
        ( *np->func ) ( np->arg, val );
    }
}

/*
 * novm - log an error message saying we ran out of memory, and die.
 */
void novm ( 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 ( char *var, char *value, int iskey )
{
    size_t varl = strlen ( var );
    size_t vl = varl + strlen ( value ) + 2;
    int i;
    char *p, *newstring;

    newstring = ( char * ) malloc ( vl + 1 );

    if ( newstring == 0 )
        return;

    *newstring++ = iskey;
    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] == '=' )
            {
#ifdef USE_TDB

                if ( p[-1] && pppdb != NULL )
                    delete_db_key ( p );

#endif
                free ( p - 1 );
                script_env[i] = newstring;
#ifdef USE_TDB

                if ( iskey && pppdb != NULL )
                    add_db_key ( newstring );

                update_db_entry();
#endif
                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;

#ifdef USE_TDB

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

        update_db_entry();
    }

#endif
}

/*
 * script_unsetenv - remove a variable from the environment
 * for scripts.
 */
void script_unsetenv ( 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] == '=' )
        {
#ifdef USE_TDB

            if ( p[-1] && pppdb != NULL )
                delete_db_key ( p );

#endif
            free ( p - 1 );

            while ( ( script_env[i] = script_env[i+1] ) != 0 )
                ++i;

            break;
        } // end if
    } // end for

#ifdef USE_TDB

    if ( pppdb != NULL )
        update_db_entry();

#endif
}

/*
 * Any arbitrary string used as a key for locking the database.
 * It doesn't matter what it is as long as all pppds use the same string.
 */
#define PPPD_LOCK_KEY "pppd lock"

/*
 * lock_db - get an exclusive lock on the TDB database.
 * Used to ensure atomicity of various lookup/modify operations.
 */
void lock_db()
{
#ifdef USE_TDB
    TDB_DATA key;

    key.dptr = PPPD_LOCK_KEY;
    key.dsize = strlen ( key.dptr );
    tdb_chainlock ( pppdb, key );
#endif
}

/*
 * unlock_db - remove the exclusive lock obtained by lock_db.
 */
void unlock_db()
{
#ifdef USE_TDB
    TDB_DATA key;

    key.dptr = PPPD_LOCK_KEY;
    key.dsize = strlen ( key.dptr );
    tdb_chainunlock ( pppdb, key );
#endif
}

#ifdef USE_TDB
/*
 * 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 + 1 );

    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_errorstr ( pppdb ) );

    if ( vbuf )
        free ( vbuf );

}

/*
 * add_db_key - add a key that we can use to look up our database entry.
 */
static void add_db_key ( 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_errorstr ( pppdb ) );
}

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

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

/*
 * cleanup_db - delete all the entries we put in the database.
 */
static void cleanup_db()
{
    TDB_DATA key;
    int i;
    char *p;

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

    for ( i = 0; ( p = script_env[i] ) != 0; ++i )
        if ( p[-1] )
            delete_db_key ( p );
}
#endif /* USE_TDB */