pptpd/pptpctrl.c

/*
 * pptpctrl.c
 *
 * PPTP control connection between PAC-PNS pair
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef __linux__
#define _GNU_SOURCE 1           /* kill() prototype, broken arpa/inet.h */
#endif

#include "our_syslog.h"

#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#ifdef HAVE_OPENPTY
#ifdef HAVE_PTY_H
#include <pty.h>
#include <termios.h>
#endif
#ifdef HAVE_LIBUTIL_H
#include <libutil.h>
#endif
#endif

#ifdef __UCLIBC__
#define socklen_t int
#endif

#include "compat.h"
#include "pptpctrl.h"
#include "pptpgre.h"
#include "pptpdefs.h"
#include "ctrlpacket.h"
#include "defaults.h"
// placing net/if.h here fixes build on Solaris
#include <net/if.h>

#ifdef VRF
char *vrf = NULL;
#endif
static char *ppp_binary = PPP_BINARY;
static int pptp_logwtmp;
static int noipparam;                   /* if true, don't send ipparam to ppp */
static char speed[32];
static char pppdxfig[256];
static pid_t pppfork;                   /* so we can kill it after disconnect */

/*
 * Global to handle dying
 *
 * I'd be nice if someone could figure out a way to do it 
 * without the global, but i don't think you can.. -tmk
 */
#define clientSocket 0          /* in case it changes back to a variable */
static u_int32_t call_id_pair;  /* call id (to terminate call) */

/* Needed by this and ctrlpacket.c */
int pptpctrl_debug = 0;         /* specifies if debugging is on or off */
uint16_t unique_call_id = 0xFFFF;       /* Start value for our call IDs on this TCP link */

int gargc;                     /* Command line argument count */
char **gargv;                  /* Command line argument vector */

/* Local function prototypes */
static void bail(int sigraised);
static void pptp_handle_ctrl_connection(char **pppaddrs, struct in_addr *inetaddrs);

static int startCall(char **pppaddrs, struct in_addr *inetaddrs);
static void launch_pppd(char **pppaddrs, struct in_addr *inetaddrs);

/* Oh the horror.. lets hope this covers all the ones we have to handle */
#if defined(O_NONBLOCK) && !defined(__sun__) && !defined(__sun)
#define OUR_NB_MODE O_NONBLOCK
#else
#define OUR_NB_MODE O_NDELAY
#endif

/* read a command line argument, a flag alone */
#define GETARG_INT(X) \
        X = atoi(argv[arg++])

/* read a command line argument, a string alone */
#define GETARG_STRING(X) \
        X = strdup(argv[arg++])

/* read a command line argument, a presence flag followed by string */
#define GETARG_VALUE(X) \
        if(atoi(argv[arg++]) != 0) \
                strlcpy(X, argv[arg++], sizeof(X)); \
        else \
                *X = '\0'

int main(int argc, char **argv)
{
        char pppLocal[16];              /* local IP to pass to pppd */
        char pppRemote[16];             /* remote IP address to pass to pppd */
        struct sockaddr_in addr;        /* client address */
        socklen_t addrlen;
        int arg = 1;
        int flags;
        struct in_addr inetaddrs[2];
        char *pppaddrs[2] = { pppLocal, pppRemote };

        gargc = argc;
        gargv = argv;

        /* fail if argument count invalid */
        if (argc < 7) {
                fprintf(stderr, "pptpctrl: insufficient arguments, see man pptpctrl\n");
                exit(2);
        }

        /* open a connection to the syslog daemon */
        openlog("pptpd", LOG_PID, PPTP_FACILITY);

        /* autoreap if supported */
        signal(SIGCHLD, SIG_IGN);

        /* note: update pptpctrl.8 if the argument list format is changed */
        GETARG_INT(pptpctrl_debug);
        GETARG_INT(noipparam);
#ifdef VRF
        GETARG_STRING(vrf);
#endif
        GETARG_VALUE(pppdxfig);
        GETARG_VALUE(speed);
        GETARG_VALUE(pppLocal);
        GETARG_VALUE(pppRemote);
        if (arg < argc) GETARG_INT(unique_call_id);
        if (arg < argc) GETARG_STRING(ppp_binary);
        if (arg < argc) GETARG_INT(pptp_logwtmp);

#ifdef VRF
        if (!*vrf) {
                free(vrf);
                vrf = NULL;
        }
#endif
        if (pptpctrl_debug) {
#ifdef VRF
                syslog(LOG_DEBUG, "CTRL: VRF used = %s", vrf ? vrf : "NONE");
#endif
                if (*pppLocal)
                        syslog(LOG_DEBUG, "CTRL: local address = %s", pppLocal);
                if (*pppRemote)
                        syslog(LOG_DEBUG, "CTRL: remote address = %s", pppRemote);
                if (*speed)
                        syslog(LOG_DEBUG, "CTRL: pppd speed = %s", speed);
                if (*pppdxfig)
                        syslog(LOG_DEBUG, "CTRL: pppd options file = %s", pppdxfig);
        }

        addrlen = sizeof(addr);
        if (getsockname(clientSocket, (struct sockaddr *) &addr, &addrlen) != 0) {
                syslog(LOG_ERR, "CTRL: getsockname() failed");
                syslog_perror("getsockname");
                close(clientSocket);
                bail(0);        /* NORETURN */
        }
        inetaddrs[0] = addr.sin_addr;

        addrlen = sizeof(addr);
        if (getpeername(clientSocket, (struct sockaddr *) &addr, &addrlen) != 0) {
                syslog(LOG_ERR, "CTRL: getpeername() failed");
                syslog_perror("getpeername");
                close(clientSocket);
                bail(0);        /* NORETURN */
        }
        inetaddrs[1] = addr.sin_addr;

        /* Set non-blocking */
        if ((flags = fcntl(clientSocket, F_GETFL, arg /* ignored */)) == -1 ||
            fcntl(clientSocket, F_SETFL, flags|OUR_NB_MODE) == -1) {
                syslog(LOG_ERR, "CTRL: Failed to set client socket non-blocking");
                syslog_perror("fcntl");
                close(clientSocket);
                bail(0);        /* NORETURN */
        }

        
        /* Fiddle with argv */
        my_setproctitle(gargc, gargv, "pptpd [%s]%20c",
            inet_ntoa(addr.sin_addr), ' ');

        /* be ready for a grisly death */
        sigpipe_create();
        sigpipe_assign(SIGTERM);
        NOTE_VALUE(PAC, call_id_pair, htons(-1));
        NOTE_VALUE(PNS, call_id_pair, htons(-1));

        syslog(LOG_INFO, "CTRL: Client %s control connection started", inet_ntoa(addr.sin_addr));
        pptp_handle_ctrl_connection(pppaddrs, inetaddrs);
        syslog(LOG_DEBUG, "CTRL: Reaping child PPP[%i]", pppfork);
        if (pppfork > 0)
                waitpid(pppfork, NULL, 0);
        syslog(LOG_INFO, "CTRL: Client %s control connection finished", inet_ntoa(addr.sin_addr));

        bail(0);                /* NORETURN */
        return 1;               /* make gcc happy */
}


/*
 * Local functions only below
 */

/*
 * pptp_handle_ctrl_connection
 *
 * 1. read a packet (should be start_ctrl_conn_rqst)
 * 2. reply to packet (send a start_ctrl_conn_rply)
 * 3. proceed with GRE and CTRL connections
 *
 * args: pppaddrs - ppp local and remote addresses (strings)
 *       inetaddrs - local and client socket address
 * retn: 0 success, -1 failure
 */
static void pptp_handle_ctrl_connection(char **pppaddrs, struct in_addr *inetaddrs)
{

        /* For echo requests used to check link is alive */
        int echo_wait = FALSE;          /* Waiting for echo? */
        u_int32_t echo_count = 0;       /* Sequence # of echo */
        time_t echo_time = 0;           /* Time last echo req sent */
        time_t last_time = time(NULL);  /* Time last received data */
        struct timeval idleTime;        /* How long to select() */

        /* General local variables */
        ssize_t rply_size;              /* Reply packet size */
        fd_set fds;                     /* For select() */
        int maxfd = clientSocket;       /* For select() */
        int send_packet;                /* Send a packet this time? */
#if BSDUSER_PPP || SLIRP
/* not needed by stuff which uses socketpair() in startCall() */
#define init 1
#else
        int init = 0;                   /* Has pppd initialized the pty? */
#endif
        int pty_fd = -1;                /* File descriptor of pty */
        int gre_fd = -1;                /* Network file descriptor */
        int sig_fd = sigpipe_fd();      /* Signal pipe descriptor       */

        struct pptp_echo_rply *packet = alloca(PPTP_MAX_CTRL_PCKT_SIZE);
        struct pptp_out_call_rply *rply_packet = alloca(PPTP_MAX_CTRL_PCKT_SIZE);

        for (;;) {

                FD_ZERO(&fds);
                FD_SET(sig_fd, &fds);
                FD_SET(clientSocket, &fds);
                if (pty_fd != -1)
                        FD_SET(pty_fd, &fds);
                if (gre_fd != -1 && init)
                        FD_SET(gre_fd, &fds);

                /* set timeout */
                if (encaps_gre(-1, NULL, 0) || decaps_hdlc(-1, NULL, 0)) {
                        idleTime.tv_sec = 0;
                        idleTime.tv_usec = 50000; /* don't ack immediately */
                } else {
                        idleTime.tv_sec = IDLE_WAIT;
                        idleTime.tv_usec = 0;
                }

                /* default: do nothing */
                send_packet = FALSE;

                switch (select(maxfd + 1, &fds, NULL, NULL, &idleTime)) {
                case -1:        /* Error with select() */
                        if (errno != EINTR)
                                syslog(LOG_ERR, "CTRL: Error with select(), quitting");
                        goto leave_clear_call;

                case 0:
                        if (decaps_hdlc(-1, NULL, 0)) {
                                if(decaps_hdlc(-1, encaps_gre, gre_fd))
                                        syslog(LOG_ERR, "CTRL: GRE re-xmit failed");
                        } else if (encaps_gre(-1, NULL, 0))
                                /* Pending ack and nothing else to do */
                                encaps_gre(gre_fd, NULL, 0);    /* send ack with no payload */
                        break;

                default:
                        break;
                }

                /* check for pending SIGTERM delivery */
                if (FD_ISSET(sig_fd, &fds)) {
                        if (sigpipe_read() == SIGTERM)
                                bail(SIGTERM);
                }

                /* detect startup of pppd */
#ifndef init
                if (!init && pty_fd != -1 && FD_ISSET(pty_fd, &fds))
                        init = 1;
#endif

                /* handle actual packets */

                /* send from pty off via GRE */
                if (pty_fd != -1 && FD_ISSET(pty_fd, &fds) && decaps_hdlc(pty_fd, encaps_gre, gre_fd) < 0) {
                        syslog(LOG_ERR, "CTRL: PTY read or GRE write failed (pty,gre)=(%d,%d)", pty_fd, gre_fd);
                        break;
                }
                /* send from GRE off to pty */
                if (gre_fd != -1 && FD_ISSET(gre_fd, &fds) && decaps_gre(gre_fd, encaps_hdlc, pty_fd) < 0) {
                        if (gre_fd == 6 && pty_fd == 5) {
                                syslog(LOG_ERR, "CTRL: GRE-tunnel has collapsed (GRE read or PTY write failed (gre,pty)=(%d,%d))", gre_fd, pty_fd);
                        } else {
                                syslog(LOG_ERR, "CTRL: GRE read or PTY write failed (gre,pty)=(%d,%d)", gre_fd, pty_fd);
                        }
                        break;
                }
                /* handle control messages */

                if (FD_ISSET(clientSocket, &fds)) {
                        time(&last_time);
                        send_packet = TRUE;
                        switch (read_pptp_packet(clientSocket, (unsigned char *) packet, rply_packet, &rply_size)) {
                        case 0:
                                syslog(LOG_ERR, "CTRL: CTRL read failed");
                                goto leave_drop_call;

                        case -1:
                                send_packet = FALSE;
                                break;

                        case STOP_CTRL_CONN_RQST:
                                if (pptpctrl_debug)
                                        syslog(LOG_DEBUG, "CTRL: Received STOP CTRL CONN request (disconnecting)");
                                if (gre_fd != -1 || pty_fd != -1)
                                        syslog(LOG_WARNING, "CTRL: Request to close control connection when call is open, closing");
                                send_pptp_packet(clientSocket, rply_packet, rply_size);
                                goto leave_drop_call;

                        case CALL_CLR_RQST:
                                if(pptpctrl_debug)
                                        syslog(LOG_DEBUG, "CTRL: Received CALL CLR request (closing call)");
                                if (gre_fd == -1 || pty_fd == -1)
                                        syslog(LOG_WARNING, "CTRL: Request to close call but call not open");
                                if (gre_fd != -1) {
                                        FD_CLR(gre_fd, &fds);
                                        close(gre_fd);
                                        gre_fd = -1;
                                }
                                if (pty_fd != -1) {
                                        FD_CLR(pty_fd, &fds);
                                        close(pty_fd);
                                        pty_fd = -1;
                                }
                                /* violating RFC */
                                goto leave_drop_call;

                        case OUT_CALL_RQST:
                                /* for killing off the link later (ugly) */
                                NOTE_VALUE(PAC, call_id_pair, rply_packet->call_id);
                                NOTE_VALUE(PNS, call_id_pair, rply_packet->call_id_peer);
                                if (gre_fd != -1 || pty_fd != -1) {
                                        syslog(LOG_WARNING, "CTRL: Request to open call when call is already open, closing");
                                        if (gre_fd != -1) {
                                                FD_CLR(gre_fd, &fds);
                                                close(gre_fd);
                                                gre_fd = -1;
                                        }
                                        if (pty_fd != -1) {
                                                FD_CLR(pty_fd, &fds);
                                                close(pty_fd);
                                                pty_fd = -1;
                                        }
                                }
                                /* change process title for accounting and status scripts */
                                my_setproctitle(gargc, gargv,
                                      "pptpd [%s:%04X - %04X]",
                                      inet_ntoa(inetaddrs[1]),
                                      ntohs(rply_packet->call_id_peer),
                                      ntohs(rply_packet->call_id));
                                /* start the call, by launching pppd */
                                syslog(LOG_INFO, "CTRL: Starting call (launching pppd, opening GRE)");
                                pty_fd = startCall(pppaddrs, inetaddrs);
                                if (pty_fd > maxfd) maxfd = pty_fd;
                                if ((gre_fd = pptp_gre_init(call_id_pair, pty_fd, inetaddrs)) > maxfd)
                                        maxfd = gre_fd;
                                break;

                        case ECHO_RPLY:
                                if (echo_wait == TRUE && packet->identifier == echo_count)
                                        echo_wait = FALSE;
                                else
                                        syslog(LOG_WARNING, "CTRL: Unexpected ECHO REPLY packet");
                                /* FALLTHRU */
                        case SET_LINK_INFO:
                                send_packet = FALSE;
                                break;

#ifdef PNS_MODE
                        case IN_CALL_RQST:
                        case IN_CALL_RPLY:
                        case IN_CALL_CONN:
#endif

                        case CALL_DISCONN_NTFY:
                        case STOP_CTRL_CONN_RPLY:
                                /* These don't generate replies.  Also they come from things we don't send in this section. */
                                syslog(LOG_WARNING, "CTRL: Got a reply to a packet we didn't send");
                                send_packet = FALSE;
                                break;

                        /* Otherwise, the already-formed reply will do fine, so send it */
                        }
                /* send echo request packet if we have not heard from the TCP socket in IDLE_TIME */
                } else if (echo_wait != TRUE && (time(NULL) - last_time) > IDLE_WAIT) {
                        echo_count++;
                        if (pptpctrl_debug)
                                syslog(LOG_DEBUG, "CTRL: Sending ECHO REQ id %d", echo_count);
                        time(&echo_time);
                        make_echo_req_packet(rply_packet, &rply_size, echo_count);
                        echo_wait = TRUE;
                        send_packet = TRUE;
                }

                /* send reply packet - this may block, but it should be very rare */
                if (send_packet == TRUE && send_pptp_packet(clientSocket, rply_packet, rply_size) < 0) {
                        syslog(LOG_ERR, "CTRL: Error sending GRE, aborting call");
                        goto leave_clear_call;
                }

                /* waiting for echo reply and curtime - echo_time > max wait */
                if (echo_wait == TRUE && (time(NULL) - echo_time) > MAX_ECHO_WAIT) {
                        syslog(LOG_INFO, "CTRL: Session timed out, ending call");
                        goto leave_clear_call;
                }
        }
        /* Finished! :-) */
leave_drop_call:
        NOTE_VALUE(PAC, call_id_pair, htons(-1));
        NOTE_VALUE(PNS, call_id_pair, htons(-1));
        close(clientSocket);
leave_clear_call:
        /* leave clientSocket and call_id_pair alone for bail() */
        if (gre_fd != -1)
                close(gre_fd);
        gre_fd = -1;
        if (pty_fd != -1)
                close(pty_fd);
        pty_fd = -1;
        return;
#ifdef init
#undef init
#endif
}


/*
 * This is the custom exit() for this program.
 *
 * Updated to also be the default SIGTERM handler, and if
 * the link is going down for unnatural reasons, we will close it
 * right now, it's only been tested for win98, other tests would be nice
 * -tmk
 */
static void bail(int sigraised)
{
        if (sigraised)
                syslog(LOG_INFO, "CTRL: Exiting on signal %d", sigraised);

        /* send a disconnect to the other end */
        /* ignore any errors */
        if (GET_VALUE(PAC, call_id_pair) != htons(-1)) {
                fd_set connSet;         /* fd_set for select() */
                struct timeval tv;      /* time to wait for reply */
                unsigned char packet[PPTP_MAX_CTRL_PCKT_SIZE];
                struct pptp_out_call_rply *rply_packet = alloca(PPTP_MAX_CTRL_PCKT_SIZE);
                ssize_t rply_size;      /* reply packet size */
                int pkt;
                int retry = 0;

                if (pptpctrl_debug)
                        syslog(LOG_DEBUG, "CTRL: Exiting with active call");

                make_call_admin_shutdown(rply_packet, &rply_size);
                if(send_pptp_packet(clientSocket, rply_packet, rply_size) < 0)
                        goto skip;

                make_stop_ctrl_req(rply_packet, &rply_size);
                if(send_pptp_packet(clientSocket, rply_packet, rply_size) < 0)
                        goto skip;

                FD_ZERO(&connSet);
                FD_SET(clientSocket, &connSet);
                tv.tv_sec = 5;  /* wait 5 secs for a reply then quit */
                tv.tv_usec = 0;

                /* Wait for STOP CTRL CONN RQST or RPLY */
                while (select(clientSocket + 1, &connSet, NULL, NULL, &tv) == 1) {
                        switch((pkt = read_pptp_packet(clientSocket, packet, rply_packet, &rply_size))) {
                        case STOP_CTRL_CONN_RQST:
                                send_pptp_packet(clientSocket, rply_packet, rply_size);
                                goto skip;
                        case CALL_CLR_RQST:
                                syslog(LOG_WARNING, "CTRL: Got call clear request after call manually shutdown - buggy client");
                                break;
                        case STOP_CTRL_CONN_RPLY:
                                goto skip;
                        case -1:
                                syslog(LOG_WARNING, "CTRL: Retryable error in disconnect sequence");
                                retry++;
                                break;
                        case 0:
                                syslog(LOG_WARNING, "CTRL: Fatal error reading control message in disconnect sequence");
                                goto skip;
                        default:
                                syslog(LOG_WARNING, "CTRL: Unexpected control message %d in disconnect sequence", pkt);
                                retry++;
                                break;
                        }
                        tv.tv_sec = 5;  /* wait 5 secs for another reply then quit */
                        tv.tv_usec = 0;
                        if (retry > 100) {
                                syslog(LOG_WARNING, "CTRL: Too many retries (%d) - giving up", retry);
                                break;
                        }
                }

        skip:
                close(clientSocket);
        }

        if (pptpctrl_debug)
                syslog(LOG_DEBUG, "CTRL: Exiting now");
}

/*
 * startCall
 *
 * Launches PPPD for the call.
 *
 * args:        pppaddrs - local/remote IPs or "" for either/both if none
 * retn:        pty file descriptor
 *
 */
static int startCall(char **pppaddrs, struct in_addr *inetaddrs)
{
        /* PTY/TTY pair for talking to PPPd */
        int pty_fd, tty_fd;
        /* register pids of children */
#if BSDUSER_PPP || SLIRP
        int sockfd[2];

#ifndef AF_LOCAL
#ifdef AF_UNIX
#define AF_LOCAL AF_UNIX /* Old BSD */
#else
#define AF_LOCAL AF_FILE /* POSIX */
#endif
#endif

        /* userspace ppp doesn't need to waste a real pty/tty pair */
        if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sockfd)) {
                syslog(LOG_ERR, "CTRL: socketpair() error");
                syslog_perror("socketpair");
                exit(1);
        }
        tty_fd = sockfd[0];
        pty_fd = sockfd[1];
#else
        /* Finds an open pty/tty pair */
        if (openpty(&pty_fd, &tty_fd, NULL, NULL, NULL) != 0) {
                syslog(LOG_ERR, "CTRL: openpty() error");
                syslog_perror("openpty");
                exit(1);
        } else {
                struct termios tios;

                /* Turn off echo in the slave - to prevent loopback.
                   pppd will do this, but might not do it before we
                   try to send data. */
                if (tcgetattr(tty_fd, &tios) < 0) {
                        syslog(LOG_ERR, "CTRL: tcgetattr() error");
                        syslog_perror("tcgetattr");
                        exit(1);
                }
                tios.c_lflag &= ~(ECHO | ECHONL);
                if (tcsetattr(tty_fd, TCSAFLUSH, &tios) < 0) {
                        syslog(LOG_ERR, "CTRL: tcsetattr() error");
                        syslog_perror("tcsetattr");
                        exit(1);
                }
        }
#endif
        if (pptpctrl_debug) {
                syslog(LOG_DEBUG, "CTRL: pty_fd = %d", pty_fd);
                syslog(LOG_DEBUG, "CTRL: tty_fd = %d", tty_fd);
        }
        /* Launch the PPPD  */
#ifndef HAVE_FORK
        switch(pppfork=vfork()){
#else
        switch(pppfork=fork()){
#endif
        case -1:        /* fork() error */
                syslog(LOG_ERR, "CTRL: Error forking to exec pppd");
                _exit(1);

        case 0:         /* child */
                if (dup2(tty_fd, 0) == -1) {
                  syslog(LOG_ERR, "CTRL: child tty_fd dup2 to stdin, %s",
                         strerror(errno));
                  exit(1);
                }
                if (dup2(tty_fd, 1) == -1) {
                  syslog(LOG_ERR, "CTRL: child tty_fd dup2 to stdout, %s",
                         strerror(errno));
                  exit(1);
                }
#if 0
                /* This must never be used if !HAVE_SYSLOG since that logs to stderr.
                 * Trying just never using it to see if it causes anyone else problems.
                 * It may let people see the pppd errors, which would be good.
                 */
                dup2(tty_fd, 2);
#endif
                if (tty_fd > 1)
                        close(tty_fd);
                if (pty_fd > 1)
                        close(pty_fd);
/* In case we move clientSocket back off stdin */
#ifndef clientSocket
                if (clientSocket > 1)
                        close(clientSocket);
#elif clientSocket > 1
                close(clientSocket);
#endif
                launch_pppd(pppaddrs, inetaddrs);
                syslog(LOG_ERR, "CTRL: PPPD launch failed! (launch_pppd did not fork)");
                _exit(1);
        }
        
        close(tty_fd);
        return pty_fd;
}

/*
 * launch_pppd
 *
 * Launches the PPP daemon. The PPP daemon is responsible for assigning the
 * PPTP client its IP address.. These values are assigned via the command
 * line.
 *
 * Add return of connected ppp interface
 *
 * retn: 0 on success, -1 on failure.
 *
 */
static void launch_pppd(char **pppaddrs, struct in_addr *inetaddrs)
{
        char *pppd_argv[16];
        int an = 0;
        sigset_t sigs;
        char pppInterfaceIPs[33];

        pppd_argv[an++] = ppp_binary;

        if (pptpctrl_debug) {
                syslog(LOG_DEBUG, 
                       "CTRL (PPPD Launcher): program binary = %s", 
                       pppd_argv[an - 1]);
        }

#if BSDUSER_PPP

        /* The way that Brian Somers' user-land ppp works is to use the
         * system name as a reference for most of the useful options. Hence
         * most things can't be defined on the command line. On OpenBSD at
         * least the file used for the systems is /etc/ppp/ppp.conf, where
         * the pptp stanza should look something like:

         pptp:
         set speed sync
         enable pap
         enable chap
         set dns a.a.a.a b.b.b.b
         set ndbs x.x.x.x y.y.y.y
         accept dns
         add 10.0.0/24

         * To be honest, at the time of writing, I haven't had the thing
         * working enough to understand :) I will update this comment and
         * make a sample config available when I get there.
         */

        /* options for BSDUSER_PPP
         *
         * ignores IP addresses, config file option, speed
         * fix usage info in pptpd.c and configure script if this changes
         *
         * IP addresses can be specified in /etc/ppp/ppp.secret per user
         */
        pppd_argv[an++] = "-direct";
        pppd_argv[an++] = "pptp";       /* XXX this is the system name */
        /* should be dynamic - PMG */

#elif SLIRP

        /* options for SLIRP
         *
         * ignores IP addresses from config - SLIRP handles this
         */
        pppd_argv[an++] = "-P";
        pppd_argv[an++] = "+chap";
        pppd_argv[an++] = "-b";

        /* If a speed has been specified, use it
         * if not, use "smart" default (defaults.h)
         */
        if (*speed) {
                pppd_argv[an++] = speed;
        } else {
                pppd_argv[an++] = PPP_SPEED_DEFAULT;
        }

        if (*pppdxfig) {
                pppd_argv[an++] = "-f";
                pppd_argv[an++] = pppdxfig;
        }

        if (pptpctrl_debug) {
                syslog(LOG_DEBUG, "CTRL (PPPD Launcher): Connection speed = %s", pppd_argv[an - 1]);
        }
#else

        /* options for 'normal' pppd */

        pppd_argv[an++] = "local";

        /* If a pppd option file is specified, use it
         * if not, pppd will default to /etc/ppp/options
         */
        if (*pppdxfig) {
                pppd_argv[an++] = "file";
                pppd_argv[an++] = pppdxfig;
        }
        
        /* If a speed has been specified, use it
         * if not, use "smart" default (defaults.h)
         */
        if (*speed) {
                pppd_argv[an++] = speed;
        } else {
                pppd_argv[an++] = PPP_SPEED_DEFAULT;
        }

        if (pptpctrl_debug) {
                if (*pppaddrs[0])
                        syslog(LOG_DEBUG, "CTRL (PPPD Launcher): local address = %s", pppaddrs[0]);
                if (*pppaddrs[1])
                        syslog(LOG_DEBUG, "CTRL (PPPD Launcher): remote address = %s", pppaddrs[1]);
        }
        
        if (*pppaddrs[0] || *pppaddrs[1]) {
                sprintf(pppInterfaceIPs, "%s:%s", pppaddrs[0], pppaddrs[1]);
                pppd_argv[an++] = pppInterfaceIPs;
        }

        if (!noipparam) {
                 pppd_argv[an++] = "ipparam";
                 pppd_argv[an++] = inet_ntoa(inetaddrs[1]);
        }

        if (pptp_logwtmp) {
                 pppd_argv[an++] = "plugin";
                 pppd_argv[an++] = "/usr/lib/pptpd/pptpd-logwtmp.so";
                 pppd_argv[an++] = "pptpd-original-ip";
                 pppd_argv[an++] = inet_ntoa(inetaddrs[1]);
        }
#endif

        pppd_argv[an++] = "remotenumber";
        pppd_argv[an++] = inet_ntoa(inetaddrs[1]);

        /* argv arrays must always be NULL terminated */
        pppd_argv[an++] = NULL;
        /* make sure SIGCHLD is unblocked, pppd does not expect it */
        sigfillset(&sigs);
        sigprocmask(SIG_UNBLOCK, &sigs, NULL);
        /* run pppd now */
        execvp(pppd_argv[0], pppd_argv);
        /* execvp() failed */
        syslog(LOG_ERR, 
               "CTRL (PPPD Launcher): Failed to launch PPP daemon. %s",
               strerror(errno));
}