[ppp.git] / pppd / ipcp.c

/*
 * ipcp.c - PPP IP Control Protocol.
 *
 * 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
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 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.
 */

/*
 * TODO:
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <netdb.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>

#include "pppd.h"
#include "fsm.h"
#include "ipcp.h"
#include "pathnames.h"


/* global vars */
ipcp_options ipcp_wantoptions[NUM_PPP]; /* Options that we want to request */
ipcp_options ipcp_gotoptions[NUM_PPP];  /* Options that peer ack'd */
ipcp_options ipcp_allowoptions[NUM_PPP]; /* Options we allow peer to request */
ipcp_options ipcp_hisoptions[NUM_PPP];  /* Options that we ack'd */

u_int32_t netmask = 0;          /* IP netmask to set on interface */

bool    disable_defaultip = 0;  /* Don't use hostname for default IP adrs */
bool    noremoteip = 0;         /* Let him have no IP address */

/* Hook for a plugin to know when IP protocol has come up */
void (*ip_up_hook)(void) = NULL;

/* Hook for a plugin to know when IP protocol has come down */
void (*ip_down_hook)(void) = NULL;

/* Hook for a plugin to choose the remote IP address */
void (*ip_choose_hook)(u_int32_t *) = NULL;

/* Notifiers for when IPCP goes up and down */
struct notifier *ip_up_notifier = NULL;
struct notifier *ip_down_notifier = NULL;

/* local vars */
static int default_route_set[NUM_PPP];  /* Have set up a default route */
static int proxy_arp_set[NUM_PPP];      /* Have created proxy arp entry */
static bool usepeerdns;                 /* Ask peer for DNS addrs */
static int ipcp_is_up;                  /* have called np_up() */
static int ipcp_is_open;                /* haven't called np_finished() */
static bool ask_for_local;              /* request our address from peer */
static char vj_value[8];                /* string form of vj option value */
static char netmask_str[20];            /* string form of netmask value */

/*
 * Callbacks for fsm code.  (CI = Configuration Information)
 */
static void ipcp_resetci (fsm *);       /* Reset our CI */
static int  ipcp_cilen (fsm *);         /* Return length of our CI */
static void ipcp_addci (fsm *, u_char *, int *); /* Add our CI */
static int  ipcp_ackci (fsm *, u_char *, int);  /* Peer ack'd our CI */
static int  ipcp_nakci (fsm *, u_char *, int, int);/* Peer nak'd our CI */
static int  ipcp_rejci (fsm *, u_char *, int);  /* Peer rej'd our CI */
static int  ipcp_reqci (fsm *, u_char *, int *, int); /* Rcv CI */
static void ipcp_up (fsm *);            /* We're UP */
static void ipcp_down (fsm *);          /* We're DOWN */
static void ipcp_finished (fsm *);      /* Don't need lower layer */

fsm ipcp_fsm[NUM_PPP];          /* IPCP fsm structure */

static fsm_callbacks ipcp_callbacks = { /* IPCP callback routines */
    ipcp_resetci,               /* Reset our Configuration Information */
    ipcp_cilen,                 /* Length of our Configuration Information */
    ipcp_addci,                 /* Add our Configuration Information */
    ipcp_ackci,                 /* ACK our Configuration Information */
    ipcp_nakci,                 /* NAK our Configuration Information */
    ipcp_rejci,                 /* Reject our Configuration Information */
    ipcp_reqci,                 /* Request peer's Configuration Information */
    ipcp_up,                    /* Called when fsm reaches OPENED state */
    ipcp_down,                  /* Called when fsm leaves OPENED state */
    NULL,                       /* Called when we want the lower layer up */
    ipcp_finished,              /* Called when we want the lower layer down */
    NULL,                       /* Called when Protocol-Reject received */
    NULL,                       /* Retransmission is necessary */
    NULL,                       /* Called to handle protocol-specific codes */
    "IPCP"                      /* String name of protocol */
};

/*
 * Command-line options.
 */
static int setvjslots (char **);
static int setdnsaddr (char **);
static int setwinsaddr (char **);
static int setnetmask (char **);
int setipaddr (char *, char **, int);
static void printipaddr (option_t *, void (*)(void *, char *,...),void *);

static option_t ipcp_option_list[] = {
    { "noip", o_bool, &ipcp_protent.enabled_flag,
      "Disable IP and IPCP" },
    { "-ip", o_bool, &ipcp_protent.enabled_flag,
      "Disable IP and IPCP", OPT_ALIAS },

    { "novj", o_bool, &ipcp_wantoptions[0].neg_vj,
      "Disable VJ compression", OPT_A2CLR, &ipcp_allowoptions[0].neg_vj },
    { "-vj", o_bool, &ipcp_wantoptions[0].neg_vj,
      "Disable VJ compression", OPT_ALIAS | OPT_A2CLR,
      &ipcp_allowoptions[0].neg_vj },

    { "novjccomp", o_bool, &ipcp_wantoptions[0].cflag,
      "Disable VJ connection-ID compression", OPT_A2CLR,
      &ipcp_allowoptions[0].cflag },
    { "-vjccomp", o_bool, &ipcp_wantoptions[0].cflag,
      "Disable VJ connection-ID compression", OPT_ALIAS | OPT_A2CLR,
      &ipcp_allowoptions[0].cflag },

    { "vj-max-slots", o_special, (void *)setvjslots,
      "Set maximum VJ header slots",
      OPT_PRIO | OPT_A2STRVAL | OPT_STATIC, vj_value },

    { "ipcp-accept-local", o_bool, &ipcp_wantoptions[0].accept_local,
      "Accept peer's address for us", 1 },
    { "ipcp-accept-remote", o_bool, &ipcp_wantoptions[0].accept_remote,
      "Accept peer's address for it", 1 },

    { "ipparam", o_string, &ipparam,
      "Set ip script parameter", OPT_PRIO },

    { "noipdefault", o_bool, &disable_defaultip,
      "Don't use name for default IP adrs", 1 },

    { "ms-dns", o_special, (void *)setdnsaddr,
      "DNS address for the peer's use", OPT_A2LIST },
    { "ms-wins", o_special, (void *)setwinsaddr,
      "Nameserver for SMB over TCP/IP for peer", OPT_A2LIST },

    { "ipcp-restart", o_int, &ipcp_fsm[0].timeouttime,
      "Set timeout for IPCP", OPT_PRIO },
    { "ipcp-max-terminate", o_int, &ipcp_fsm[0].maxtermtransmits,
      "Set max #xmits for term-reqs", OPT_PRIO },
    { "ipcp-max-configure", o_int, &ipcp_fsm[0].maxconfreqtransmits,
      "Set max #xmits for conf-reqs", OPT_PRIO },
    { "ipcp-max-failure", o_int, &ipcp_fsm[0].maxnakloops,
      "Set max #conf-naks for IPCP", OPT_PRIO },

    { "defaultroute", o_bool, &ipcp_wantoptions[0].default_route,
      "Add default route", OPT_ENABLE|1, &ipcp_allowoptions[0].default_route },
    { "nodefaultroute", o_bool, &ipcp_allowoptions[0].default_route,
      "disable defaultroute option", OPT_A2CLR,
      &ipcp_wantoptions[0].default_route },
    { "-defaultroute", o_bool, &ipcp_allowoptions[0].default_route,
      "disable defaultroute option", OPT_ALIAS | OPT_A2CLR,
      &ipcp_wantoptions[0].default_route },

#ifdef __linux__
    { "replacedefaultroute", o_bool,
                                &ipcp_wantoptions[0].replace_default_route,
      "Replace default route", OPT_PRIV | 1
    },
    { "noreplacedefaultroute", o_bool,
                                &ipcp_wantoptions[0].replace_default_route,
      "Do not replace default route", 0 },
#endif
    { "proxyarp", o_bool, &ipcp_wantoptions[0].proxy_arp,
      "Add proxy ARP entry", OPT_ENABLE|1, &ipcp_allowoptions[0].proxy_arp },
    { "noproxyarp", o_bool, &ipcp_allowoptions[0].proxy_arp,
      "disable proxyarp option", OPT_A2CLR,
      &ipcp_wantoptions[0].proxy_arp },
    { "-proxyarp", o_bool, &ipcp_allowoptions[0].proxy_arp,
      "disable proxyarp option", OPT_ALIAS | OPT_A2CLR,
      &ipcp_wantoptions[0].proxy_arp },

    { "usepeerdns", o_bool, &usepeerdns,
      "Ask peer for DNS address(es)", 1 },

    { "netmask", o_special, (void *)setnetmask,
      "set netmask", OPT_PRIO | OPT_A2STRVAL | OPT_STATIC, netmask_str },

    { "ipcp-no-addresses", o_bool, &ipcp_wantoptions[0].old_addrs,
      "Disable old-style IP-Addresses usage", OPT_A2CLR,
      &ipcp_allowoptions[0].old_addrs },
    { "ipcp-no-address", o_bool, &ipcp_wantoptions[0].neg_addr,
      "Disable IP-Address usage", OPT_A2CLR,
      &ipcp_allowoptions[0].neg_addr },
#ifdef __linux__
    { "noremoteip", o_bool, &noremoteip,
      "Allow peer to have no IP address", 1 },
#endif
    { "nosendip", o_bool, &ipcp_wantoptions[0].neg_addr,
      "Don't send our IP address to peer", OPT_A2CLR,
      &ipcp_wantoptions[0].old_addrs},

    { "IP addresses", o_wild, (void *) &setipaddr,
      "set local and remote IP addresses",
      OPT_NOARG | OPT_A2PRINTER, (void *) &printipaddr },

    { NULL }
};

/*
 * Protocol entry points from main code.
 */
static void ipcp_init (int);
static void ipcp_open (int);
static void ipcp_close (int, char *);
static void ipcp_lowerup (int);
static void ipcp_lowerdown (int);
static void ipcp_input (int, u_char *, int);
static void ipcp_protrej (int);
static int  ipcp_printpkt (u_char *, int,
                           void (*) (void *, char *, ...), void *);
static void ip_check_options (void);
static int  ip_demand_conf (int);
static int  ip_active_pkt (u_char *, int);
static void create_resolv (u_int32_t, u_int32_t);

struct protent ipcp_protent = {
    PPP_IPCP,
    ipcp_init,
    ipcp_input,
    ipcp_protrej,
    ipcp_lowerup,
    ipcp_lowerdown,
    ipcp_open,
    ipcp_close,
    ipcp_printpkt,
    NULL,
    1,
    "IPCP",
    "IP",
    ipcp_option_list,
    ip_check_options,
    ip_demand_conf,
    ip_active_pkt
};

static void ipcp_clear_addrs (int, u_int32_t, u_int32_t, bool);
static void ipcp_script (char *, int);  /* Run an up/down script */
static void ipcp_script_done (void *);

/*
 * Lengths of configuration options.
 */
#define CILEN_VOID      2
#define CILEN_COMPRESS  4       /* min length for compression protocol opt. */
#define CILEN_VJ        6       /* length for RFC1332 Van-Jacobson opt. */
#define CILEN_ADDR      6       /* new-style single address option */
#define CILEN_ADDRS     10      /* old-style dual address option */


#define CODENAME(x)     ((x) == CONFACK ? "ACK" : \
                         (x) == CONFNAK ? "NAK" : "REJ")

/*
 * This state variable is used to ensure that we don't
 * run an ipcp-up/down script while one is already running.
 */
static enum script_state {
    s_down,
    s_up,
} ipcp_script_state;
static pid_t ipcp_script_pid;

/*
 * Make a string representation of a network IP address.
 */
char *
ip_ntoa(u_int32_t ipaddr)
{
    static char b[64];

    slprintf(b, sizeof(b), "%I", ipaddr);
    return b;
}

/*
 * Option parsing.
 */

/*
 * setvjslots - set maximum number of connection slots for VJ compression
 */
static int
setvjslots(char **argv)
{
    int value;

    if (!int_option(*argv, &value))
        return 0;
    if (value < 2 || value > 16) {
        option_error("vj-max-slots value must be between 2 and 16");
        return 0;
    }
    ipcp_wantoptions [0].maxslotindex =
        ipcp_allowoptions[0].maxslotindex = value - 1;
    slprintf(vj_value, sizeof(vj_value), "%d", value);
    return 1;
}

/*
 * setdnsaddr - set the dns address(es)
 */
static int
setdnsaddr(char **argv)
{
    u_int32_t dns;
    struct hostent *hp;

    dns = inet_addr(*argv);
    if (dns == (u_int32_t) -1) {
        if ((hp = gethostbyname(*argv)) == NULL) {
            option_error("invalid address parameter '%s' for ms-dns option",
                         *argv);
            return 0;
        }
        dns = *(u_int32_t *)hp->h_addr;
    }

    /* We take the last 2 values given, the 2nd-last as the primary
       and the last as the secondary.  If only one is given it
       becomes both primary and secondary. */
    if (ipcp_allowoptions[0].dnsaddr[1] == 0)
        ipcp_allowoptions[0].dnsaddr[0] = dns;
    else
        ipcp_allowoptions[0].dnsaddr[0] = ipcp_allowoptions[0].dnsaddr[1];

    /* always set the secondary address value. */
    ipcp_allowoptions[0].dnsaddr[1] = dns;

    return (1);
}

/*
 * setwinsaddr - set the wins address(es)
 * This is primrarly used with the Samba package under UNIX or for pointing
 * the caller to the existing WINS server on a Windows NT platform.
 */
static int
setwinsaddr(char **argv)
{
    u_int32_t wins;
    struct hostent *hp;

    wins = inet_addr(*argv);
    if (wins == (u_int32_t) -1) {
        if ((hp = gethostbyname(*argv)) == NULL) {
            option_error("invalid address parameter '%s' for ms-wins option",
                         *argv);
            return 0;
        }
        wins = *(u_int32_t *)hp->h_addr;
    }

    /* We take the last 2 values given, the 2nd-last as the primary
       and the last as the secondary.  If only one is given it
       becomes both primary and secondary. */
    if (ipcp_allowoptions[0].winsaddr[1] == 0)
        ipcp_allowoptions[0].winsaddr[0] = wins;
    else
        ipcp_allowoptions[0].winsaddr[0] = ipcp_allowoptions[0].winsaddr[1];

    /* always set the secondary address value. */
    ipcp_allowoptions[0].winsaddr[1] = wins;

    return (1);
}

/*
 * setipaddr - Set the IP address
 * If doit is 0, the call is to check whether this option is
 * potentially an IP address specification.
 * Not static so that plugins can call it to set the addresses
 */
int
setipaddr(char *arg, char **argv, int doit)
{
    struct hostent *hp;
    char *colon;
    u_int32_t local, remote;
    ipcp_options *wo = &ipcp_wantoptions[0];
    static int prio_local = 0, prio_remote = 0;

    /*
     * IP address pair separated by ":".
     */
    if ((colon = strchr(arg, ':')) == NULL)
        return 0;
    if (!doit)
        return 1;
  
    /*
     * If colon first character, then no local addr.
     */
    if (colon != arg && option_priority >= prio_local) {
        *colon = '\0';
        if ((local = inet_addr(arg)) == (u_int32_t) -1) {
            if ((hp = gethostbyname(arg)) == NULL) {
                option_error("unknown host: %s", arg);
                return 0;
            }
            local = *(u_int32_t *)hp->h_addr;
        }
        if (bad_ip_adrs(local)) {
            option_error("bad local IP address %s", ip_ntoa(local));
            return 0;
        }
        if (local != 0)
            wo->ouraddr = local;
        *colon = ':';
        prio_local = option_priority;
    }
  
    /*
     * If colon last character, then no remote addr.
     */
    if (*++colon != '\0' && option_priority >= prio_remote) {
        if ((remote = inet_addr(colon)) == (u_int32_t) -1) {
            if ((hp = gethostbyname(colon)) == NULL) {
                option_error("unknown host: %s", colon);
                return 0;
            }
            remote = *(u_int32_t *)hp->h_addr;
            if (remote_name[0] == 0)
                strlcpy(remote_name, colon, sizeof(remote_name));
        }
        if (bad_ip_adrs(remote)) {
            option_error("bad remote IP address %s", ip_ntoa(remote));
            return 0;
        }
        if (remote != 0)
            wo->hisaddr = remote;
        prio_remote = option_priority;
    }

    return 1;
}

static void
printipaddr(option_t *opt, void (*printer) (void *, char *, ...), void *arg)
{
        ipcp_options *wo = &ipcp_wantoptions[0];

        if (wo->ouraddr != 0)
                printer(arg, "%I", wo->ouraddr);
        printer(arg, ":");
        if (wo->hisaddr != 0)
                printer(arg, "%I", wo->hisaddr);
}

/*
 * setnetmask - set the netmask to be used on the interface.
 */
static int
setnetmask(char **argv)
{
    u_int32_t mask;
    int n;
    char *p;

    /*
     * Unfortunately, if we use inet_addr, we can't tell whether
     * a result of all 1s is an error or a valid 255.255.255.255.
     */
    p = *argv;
    n = parse_dotted_ip(p, &mask);

    mask = htonl(mask);

    if (n == 0 || p[n] != 0 || (netmask & ~mask) != 0) {
        option_error("invalid netmask value '%s'", *argv);
        return 0;
    }

    netmask = mask;
    slprintf(netmask_str, sizeof(netmask_str), "%I", mask);

    return (1);
}

int
parse_dotted_ip(char *p, u_int32_t *vp)
{
    int n;
    u_int32_t v, b;
    char *endp, *p0 = p;

    v = 0;
    for (n = 3;; --n) {
        b = strtoul(p, &endp, 0);
        if (endp == p)
            return 0;
        if (b > 255) {
            if (n < 3)
                return 0;
            /* accept e.g. 0xffffff00 */
            *vp = b;
            return endp - p0;
        }
        v |= b << (n * 8);
        p = endp;
        if (n == 0)
            break;
        if (*p != '.')
            return 0;
        ++p;
    }
    *vp = v;
    return p - p0;
}


/*
 * ipcp_init - Initialize IPCP.
 */
static void
ipcp_init(int unit)
{
    fsm *f = &ipcp_fsm[unit];
    ipcp_options *wo = &ipcp_wantoptions[unit];
    ipcp_options *ao = &ipcp_allowoptions[unit];

    f->unit = unit;
    f->protocol = PPP_IPCP;
    f->callbacks = &ipcp_callbacks;
    fsm_init(&ipcp_fsm[unit]);

    /*
     * Some 3G modems use repeated IPCP NAKs as a way of stalling
     * until they can contact a server on the network, so we increase
     * the default number of NAKs we accept before we start treating
     * them as rejects.
     */
    f->maxnakloops = 100;

    memset(wo, 0, sizeof(*wo));
    memset(ao, 0, sizeof(*ao));

    wo->neg_addr = wo->old_addrs = 1;
    wo->neg_vj = 1;
    wo->vj_protocol = IPCP_VJ_COMP;
    wo->maxslotindex = MAX_STATES - 1; /* really max index */
    wo->cflag = 1;


    /* max slots and slot-id compression are currently hardwired in */
    /* ppp_if.c to 16 and 1, this needs to be changed (among other */
    /* things) gmc */

    ao->neg_addr = ao->old_addrs = 1;
    ao->neg_vj = 1;
    ao->maxslotindex = MAX_STATES - 1;
    ao->cflag = 1;

    /*
     * XXX These control whether the user may use the proxyarp
     * and defaultroute options.
     */
    ao->proxy_arp = 1;
    ao->default_route = 1;
}


/*
 * ipcp_open - IPCP is allowed to come up.
 */
static void
ipcp_open(int unit)
{
    fsm_open(&ipcp_fsm[unit]);
    ipcp_is_open = 1;
}


/*
 * ipcp_close - Take IPCP down.
 */
static void
ipcp_close(int unit, char *reason)
{
    fsm_close(&ipcp_fsm[unit], reason);
}


/*
 * ipcp_lowerup - The lower layer is up.
 */
static void
ipcp_lowerup(int unit)
{
    fsm_lowerup(&ipcp_fsm[unit]);
}


/*
 * ipcp_lowerdown - The lower layer is down.
 */
static void
ipcp_lowerdown(int unit)
{
    fsm_lowerdown(&ipcp_fsm[unit]);
}


/*
 * ipcp_input - Input IPCP packet.
 */
static void
ipcp_input(int unit, u_char *p, int len)
{
    fsm_input(&ipcp_fsm[unit], p, len);
}


/*
 * ipcp_protrej - A Protocol-Reject was received for IPCP.
 *
 * Pretend the lower layer went down, so we shut up.
 */
static void
ipcp_protrej(int unit)
{
    fsm_lowerdown(&ipcp_fsm[unit]);
}


/*
 * ipcp_resetci - Reset our CI.
 * Called by fsm_sconfreq, Send Configure Request.
 */
static void
ipcp_resetci(fsm *f)
{
    ipcp_options *wo = &ipcp_wantoptions[f->unit];
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    ipcp_options *ao = &ipcp_allowoptions[f->unit];

    wo->req_addr = ((wo->neg_addr || wo->old_addrs) &&
        (ao->neg_addr || ao->old_addrs)) ||
        (wo->hisaddr && !wo->accept_remote);
    if (wo->ouraddr == 0)
        wo->accept_local = 1;
    if (wo->hisaddr == 0)
        wo->accept_remote = 1;
    wo->req_dns1 = usepeerdns;  /* Request DNS addresses from the peer */
    wo->req_dns2 = usepeerdns;
    *go = *wo;
    if (!ask_for_local)
        go->ouraddr = 0;
    if (ip_choose_hook) {
        ip_choose_hook(&wo->hisaddr);
        if (wo->hisaddr) {
            wo->accept_remote = 0;
        }
    }
    BZERO(&ipcp_hisoptions[f->unit], sizeof(ipcp_options));
}


/*
 * ipcp_cilen - Return length of our CI.
 * Called by fsm_sconfreq, Send Configure Request.
 */
static int
ipcp_cilen(fsm *f)
{
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    ipcp_options *wo = &ipcp_wantoptions[f->unit];
    ipcp_options *ho = &ipcp_hisoptions[f->unit];

#define LENCIADDRS(neg)         (neg ? CILEN_ADDRS : 0)
#define LENCIVJ(neg, old)       (neg ? (old? CILEN_COMPRESS : CILEN_VJ) : 0)
#define LENCIADDR(neg)          (neg ? CILEN_ADDR : 0)
#define LENCIDNS(neg)           LENCIADDR(neg)
#define LENCIWINS(neg)          LENCIADDR(neg)

    /*
     * First see if we want to change our options to the old
     * forms because we have received old forms from the peer.
     */
    if (go->neg_addr && go->old_addrs && !ho->neg_addr && ho->old_addrs)
        go->neg_addr = 0;
    if (wo->neg_vj && !go->neg_vj && !go->old_vj) {
        /* try an older style of VJ negotiation */
        /* use the old style only if the peer did */
        if (ho->neg_vj && ho->old_vj) {
            go->neg_vj = 1;
            go->old_vj = 1;
            go->vj_protocol = ho->vj_protocol;
        }
    }

    return (LENCIADDRS(!go->neg_addr && go->old_addrs) +
            LENCIVJ(go->neg_vj, go->old_vj) +
            LENCIADDR(go->neg_addr) +
            LENCIDNS(go->req_dns1) +
            LENCIDNS(go->req_dns2) +
            LENCIWINS(go->winsaddr[0]) +
            LENCIWINS(go->winsaddr[1])) ;
}


/*
 * ipcp_addci - Add our desired CIs to a packet.
 * Called by fsm_sconfreq, Send Configure Request.
 */
static void
ipcp_addci(fsm *f, u_char *ucp, int *lenp)
{
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    int len = *lenp;

#define ADDCIADDRS(opt, neg, val1, val2) \
    if (neg) { \
        if (len >= CILEN_ADDRS) { \
            u_int32_t l; \
            PUTCHAR(opt, ucp); \
            PUTCHAR(CILEN_ADDRS, ucp); \
            l = ntohl(val1); \
            PUTLONG(l, ucp); \
            l = ntohl(val2); \
            PUTLONG(l, ucp); \
            len -= CILEN_ADDRS; \
        } else \
            go->old_addrs = 0; \
    }

#define ADDCIVJ(opt, neg, val, old, maxslotindex, cflag) \
    if (neg) { \
        int vjlen = old? CILEN_COMPRESS : CILEN_VJ; \
        if (len >= vjlen) { \
            PUTCHAR(opt, ucp); \
            PUTCHAR(vjlen, ucp); \
            PUTSHORT(val, ucp); \
            if (!old) { \
                PUTCHAR(maxslotindex, ucp); \
                PUTCHAR(cflag, ucp); \
            } \
            len -= vjlen; \
        } else \
            neg = 0; \
    }

#define ADDCIADDR(opt, neg, val) \
    if (neg) { \
        if (len >= CILEN_ADDR) { \
            u_int32_t l; \
            PUTCHAR(opt, ucp); \
            PUTCHAR(CILEN_ADDR, ucp); \
            l = ntohl(val); \
            PUTLONG(l, ucp); \
            len -= CILEN_ADDR; \
        } else \
            neg = 0; \
    }

#define ADDCIDNS(opt, neg, addr) \
    if (neg) { \
        if (len >= CILEN_ADDR) { \
            u_int32_t l; \
            PUTCHAR(opt, ucp); \
            PUTCHAR(CILEN_ADDR, ucp); \
            l = ntohl(addr); \
            PUTLONG(l, ucp); \
            len -= CILEN_ADDR; \
        } else \
            neg = 0; \
    }

#define ADDCIWINS(opt, addr) \
    if (addr) { \
        if (len >= CILEN_ADDR) { \
            u_int32_t l; \
            PUTCHAR(opt, ucp); \
            PUTCHAR(CILEN_ADDR, ucp); \
            l = ntohl(addr); \
            PUTLONG(l, ucp); \
            len -= CILEN_ADDR; \
        } else \
            addr = 0; \
    }

    ADDCIADDRS(CI_ADDRS, !go->neg_addr && go->old_addrs, go->ouraddr,
               go->hisaddr);

    ADDCIVJ(CI_COMPRESSTYPE, go->neg_vj, go->vj_protocol, go->old_vj,
            go->maxslotindex, go->cflag);

    ADDCIADDR(CI_ADDR, go->neg_addr, go->ouraddr);

    ADDCIDNS(CI_MS_DNS1, go->req_dns1, go->dnsaddr[0]);

    ADDCIDNS(CI_MS_DNS2, go->req_dns2, go->dnsaddr[1]);

    ADDCIWINS(CI_MS_WINS1, go->winsaddr[0]);

    ADDCIWINS(CI_MS_WINS2, go->winsaddr[1]);
    
    *lenp -= len;
}


/*
 * ipcp_ackci - Ack our CIs.
 * Called by fsm_rconfack, Receive Configure ACK.
 *
 * Returns:
 *      0 - Ack was bad.
 *      1 - Ack was good.
 */
static int
ipcp_ackci(fsm *f, u_char *p, int len)
{
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    u_short cilen, citype, cishort;
    u_int32_t cilong;
    u_char cimaxslotindex, cicflag;

    /*
     * CIs must be in exactly the same order that we sent...
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */

#define ACKCIADDRS(opt, neg, val1, val2) \
    if (neg) { \
        u_int32_t l; \
        if ((len -= CILEN_ADDRS) < 0) \
            goto bad; \
        GETCHAR(citype, p); \
        GETCHAR(cilen, p); \
        if (cilen != CILEN_ADDRS || \
            citype != opt) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        if (val1 != cilong) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        if (val2 != cilong) \
            goto bad; \
    }

#define ACKCIVJ(opt, neg, val, old, maxslotindex, cflag) \
    if (neg) { \
        int vjlen = old? CILEN_COMPRESS : CILEN_VJ; \
        if ((len -= vjlen) < 0) \
            goto bad; \
        GETCHAR(citype, p); \
        GETCHAR(cilen, p); \
        if (cilen != vjlen || \
            citype != opt)  \
            goto bad; \
        GETSHORT(cishort, p); \
        if (cishort != val) \
            goto bad; \
        if (!old) { \
            GETCHAR(cimaxslotindex, p); \
            if (cimaxslotindex != maxslotindex) \
                goto bad; \
            GETCHAR(cicflag, p); \
            if (cicflag != cflag) \
                goto bad; \
        } \
    }

#define ACKCIADDR(opt, neg, val) \
    if (neg) { \
        u_int32_t l; \
        if ((len -= CILEN_ADDR) < 0) \
            goto bad; \
        GETCHAR(citype, p); \
        GETCHAR(cilen, p); \
        if (cilen != CILEN_ADDR || \
            citype != opt) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        if (val != cilong) \
            goto bad; \
    }

#define ACKCIDNS(opt, neg, addr) \
    if (neg) { \
        u_int32_t l; \
        if ((len -= CILEN_ADDR) < 0) \
            goto bad; \
        GETCHAR(citype, p); \
        GETCHAR(cilen, p); \
        if (cilen != CILEN_ADDR || citype != opt) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        if (addr != cilong) \
            goto bad; \
    }

#define ACKCIWINS(opt, addr) \
    if (addr) { \
        u_int32_t l; \
        if ((len -= CILEN_ADDR) < 0) \
            goto bad; \
        GETCHAR(citype, p); \
        GETCHAR(cilen, p); \
        if (cilen != CILEN_ADDR || citype != opt) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        if (addr != cilong) \
            goto bad; \
    }

    ACKCIADDRS(CI_ADDRS, !go->neg_addr && go->old_addrs, go->ouraddr,
               go->hisaddr);

    ACKCIVJ(CI_COMPRESSTYPE, go->neg_vj, go->vj_protocol, go->old_vj,
            go->maxslotindex, go->cflag);

    ACKCIADDR(CI_ADDR, go->neg_addr, go->ouraddr);

    ACKCIDNS(CI_MS_DNS1, go->req_dns1, go->dnsaddr[0]);

    ACKCIDNS(CI_MS_DNS2, go->req_dns2, go->dnsaddr[1]);

    ACKCIWINS(CI_MS_WINS1, go->winsaddr[0]);

    ACKCIWINS(CI_MS_WINS2, go->winsaddr[1]);

    /*
     * If there are any remaining CIs, then this packet is bad.
     */
    if (len != 0)
        goto bad;
    return (1);

bad:
    IPCPDEBUG(("ipcp_ackci: received bad Ack!"));
    return (0);
}

/*
 * ipcp_nakci - Peer has sent a NAK for some of our CIs.
 * This should not modify any state if the Nak is bad
 * or if IPCP is in the OPENED state.
 * Calback from fsm_rconfnakrej - Receive Configure-Nak or Configure-Reject.
 *
 * Returns:
 *      0 - Nak was bad.
 *      1 - Nak was good.
 */
static int
ipcp_nakci(fsm *f, u_char *p, int len, int treat_as_reject)
{
    ipcp_options *wo = &ipcp_wantoptions[f->unit];
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    u_char cimaxslotindex, cicflag;
    u_char citype, cilen, *next;
    u_short cishort;
    u_int32_t ciaddr1, ciaddr2, l, cidnsaddr;
    ipcp_options no;            /* options we've seen Naks for */
    ipcp_options try;           /* options to request next time */

    BZERO(&no, sizeof(no));
    try = *go;

    /*
     * Any Nak'd CIs must be in exactly the same order that we sent.
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */
#define NAKCIADDRS(opt, neg, code) \
    if ((neg) && \
        (cilen = p[1]) == CILEN_ADDRS && \
        len >= cilen && \
        p[0] == opt) { \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        ciaddr1 = htonl(l); \
        GETLONG(l, p); \
        ciaddr2 = htonl(l); \
        no.old_addrs = 1; \
        code \
    }

#define NAKCIVJ(opt, neg, code) \
    if (go->neg && \
        ((cilen = p[1]) == CILEN_COMPRESS || cilen == CILEN_VJ) && \
        len >= cilen && \
        p[0] == opt) { \
        len -= cilen; \
        INCPTR(2, p); \
        GETSHORT(cishort, p); \
        no.neg = 1; \
        code \
    }

#define NAKCIADDR(opt, neg, code) \
    if (go->neg && \
        (cilen = p[1]) == CILEN_ADDR && \
        len >= cilen && \
        p[0] == opt) { \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        ciaddr1 = htonl(l); \
        no.neg = 1; \
        code \
    }

#define NAKCIDNS(opt, neg, code) \
    if (go->neg && \
        ((cilen = p[1]) == CILEN_ADDR) && \
        len >= cilen && \
        p[0] == opt) { \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        cidnsaddr = htonl(l); \
        no.neg = 1; \
        code \
    }

    /*
     * Accept the peer's idea of {our,his} address, if different
     * from our idea, only if the accept_{local,remote} flag is set.
     */
    NAKCIADDRS(CI_ADDRS, !go->neg_addr && go->old_addrs,
               if (treat_as_reject) {
                   try.old_addrs = 0;
               } else {
                   if (go->accept_local && ciaddr1) {
                       /* take his idea of our address */
                       try.ouraddr = ciaddr1;
                   }
                   if (go->accept_remote && ciaddr2) {
                       /* take his idea of his address */
                       try.hisaddr = ciaddr2;
                   }
               }
        );

    /*
     * Accept the peer's value of maxslotindex provided that it
     * is less than what we asked for.  Turn off slot-ID compression
     * if the peer wants.  Send old-style compress-type option if
     * the peer wants.
     */
    NAKCIVJ(CI_COMPRESSTYPE, neg_vj,
            if (treat_as_reject) {
                try.neg_vj = 0;
            } else if (cilen == CILEN_VJ) {
                GETCHAR(cimaxslotindex, p);
                GETCHAR(cicflag, p);
                if (cishort == IPCP_VJ_COMP) {
                    try.old_vj = 0;
                    if (cimaxslotindex < go->maxslotindex)
                        try.maxslotindex = cimaxslotindex;
                    if (!cicflag)
                        try.cflag = 0;
                } else {
                    try.neg_vj = 0;
                }
            } else {
                if (cishort == IPCP_VJ_COMP || cishort == IPCP_VJ_COMP_OLD) {
                    try.old_vj = 1;
                    try.vj_protocol = cishort;
                } else {
                    try.neg_vj = 0;
                }
            }
            );

    NAKCIADDR(CI_ADDR, neg_addr,
              if (treat_as_reject) {
                  try.neg_addr = 0;
                  try.old_addrs = 0;
              } else if (go->accept_local && ciaddr1) {
                  /* take his idea of our address */
                  try.ouraddr = ciaddr1;
              }
              );

    NAKCIDNS(CI_MS_DNS1, req_dns1,
             if (treat_as_reject) {
                 try.req_dns1 = 0;
             } else {
                 try.dnsaddr[0] = cidnsaddr;
             }
             );

    NAKCIDNS(CI_MS_DNS2, req_dns2,
             if (treat_as_reject) {
                 try.req_dns2 = 0;
             } else {
                 try.dnsaddr[1] = cidnsaddr;
             }
             );

    /*
     * There may be remaining CIs, if the peer is requesting negotiation
     * on an option that we didn't include in our request packet.
     * If they want to negotiate about IP addresses, we comply.
     * If they want us to ask for compression, we refuse.
     * If they want us to ask for ms-dns, we do that, since some
     * peers get huffy if we don't.
     */
    while (len >= CILEN_VOID) {
        GETCHAR(citype, p);
        GETCHAR(cilen, p);
        if ( cilen < CILEN_VOID || (len -= cilen) < 0 )
            goto bad;
        next = p + cilen - 2;

        switch (citype) {
        case CI_COMPRESSTYPE:
            if (go->neg_vj || no.neg_vj ||
                (cilen != CILEN_VJ && cilen != CILEN_COMPRESS))
                goto bad;
            no.neg_vj = 1;
            break;
        case CI_ADDRS:
            if ((!go->neg_addr && go->old_addrs) || no.old_addrs
                || cilen != CILEN_ADDRS)
                goto bad;
            try.neg_addr = 0;
            GETLONG(l, p);
            ciaddr1 = htonl(l);
            if (ciaddr1 && go->accept_local)
                try.ouraddr = wo->old_addrs ? ciaddr1 : 0;
            GETLONG(l, p);
            ciaddr2 = htonl(l);
            if (ciaddr2 && go->accept_remote)
                try.hisaddr = ciaddr2;
            no.old_addrs = 1;
            break;
        case CI_ADDR:
            if (go->neg_addr || no.neg_addr || cilen != CILEN_ADDR)
                goto bad;
            try.old_addrs = 0;
            GETLONG(l, p);
            ciaddr1 = htonl(l);
            if (ciaddr1 && go->accept_local)
                try.ouraddr = ciaddr1;
            if (try.ouraddr != 0 && wo->neg_addr)
                try.neg_addr = 1;
            no.neg_addr = 1;
            break;
        case CI_MS_DNS1:
            if (go->req_dns1 || no.req_dns1 || cilen != CILEN_ADDR)
                goto bad;
            GETLONG(l, p);
            try.dnsaddr[0] = htonl(l);
            try.req_dns1 = 1;
            no.req_dns1 = 1;
            break;
        case CI_MS_DNS2:
            if (go->req_dns2 || no.req_dns2 || cilen != CILEN_ADDR)
                goto bad;
            GETLONG(l, p);
            try.dnsaddr[1] = htonl(l);
            try.req_dns2 = 1;
            no.req_dns2 = 1;
            break;
        case CI_MS_WINS1:
        case CI_MS_WINS2:
            if (cilen != CILEN_ADDR)
                goto bad;
            GETLONG(l, p);
            ciaddr1 = htonl(l);
            if (ciaddr1)
                try.winsaddr[citype == CI_MS_WINS2] = ciaddr1;
            break;
        }
        p = next;
    }

    /*
     * OK, the Nak is good.  Now we can update state.
     * If there are any remaining options, we ignore them.
     */
    if (f->state != OPENED)
        *go = try;

    return 1;

bad:
    IPCPDEBUG(("ipcp_nakci: received bad Nak!"));
    return 0;
}


/*
 * ipcp_rejci - Reject some of our CIs.
 * Callback from fsm_rconfnakrej.
 */
static int
ipcp_rejci(fsm *f, u_char *p, int len)
{
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    u_char cimaxslotindex, ciflag, cilen;
    u_short cishort;
    u_int32_t cilong;
    ipcp_options try;           /* options to request next time */

    try = *go;
    /*
     * Any Rejected CIs must be in exactly the same order that we sent.
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */
#define REJCIADDRS(opt, neg, val1, val2) \
    if ((neg) && \
        (cilen = p[1]) == CILEN_ADDRS && \
        len >= cilen && \
        p[0] == opt) { \
        u_int32_t l; \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        cilong = htonl(l); \
        /* Check rejected value. */ \
        if (cilong != val1) \
            goto bad; \
        GETLONG(l, p); \
        cilong = htonl(l); \
        /* Check rejected value. */ \
        if (cilong != val2) \
            goto bad; \
        try.old_addrs = 0; \
    }

#define REJCIVJ(opt, neg, val, old, maxslot, cflag) \
    if (go->neg && \
        p[1] == (old? CILEN_COMPRESS : CILEN_VJ) && \
        len >= p[1] && \
        p[0] == opt) { \
        len -= p[1]; \
        INCPTR(2, p); \
        GETSHORT(cishort, p); \
        /* Check rejected value. */  \
        if (cishort != val) \
            goto bad; \
        if (!old) { \
           GETCHAR(cimaxslotindex, p); \
           if (cimaxslotindex != maxslot) \
             goto bad; \
           GETCHAR(ciflag, p); \
           if (ciflag != cflag) \
             goto bad; \
        } \
        try.neg = 0; \
     }

#define REJCIADDR(opt, neg, val) \
    if (go->neg && \
        (cilen = p[1]) == CILEN_ADDR && \
        len >= cilen && \
        p[0] == opt) { \
        u_int32_t l; \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        cilong = htonl(l); \
        /* Check rejected value. */ \
        if (cilong != val) \
            goto bad; \
        try.neg = 0; \
    }

#define REJCIDNS(opt, neg, dnsaddr) \
    if (go->neg && \
        ((cilen = p[1]) == CILEN_ADDR) && \
        len >= cilen && \
        p[0] == opt) { \
        u_int32_t l; \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        cilong = htonl(l); \
        /* Check rejected value. */ \
        if (cilong != dnsaddr) \
            goto bad; \
        try.neg = 0; \
    }

#define REJCIWINS(opt, addr) \
    if (addr && \
        ((cilen = p[1]) == CILEN_ADDR) && \
        len >= cilen && \
        p[0] == opt) { \
        u_int32_t l; \
        len -= cilen; \
        INCPTR(2, p); \
        GETLONG(l, p); \
        cilong = htonl(l); \
        /* Check rejected value. */ \
        if (cilong != addr) \
            goto bad; \
        try.winsaddr[opt == CI_MS_WINS2] = 0; \
    }

    REJCIADDRS(CI_ADDRS, !go->neg_addr && go->old_addrs,
               go->ouraddr, go->hisaddr);

    REJCIVJ(CI_COMPRESSTYPE, neg_vj, go->vj_protocol, go->old_vj,
            go->maxslotindex, go->cflag);

    REJCIADDR(CI_ADDR, neg_addr, go->ouraddr);

    REJCIDNS(CI_MS_DNS1, req_dns1, go->dnsaddr[0]);

    REJCIDNS(CI_MS_DNS2, req_dns2, go->dnsaddr[1]);

    REJCIWINS(CI_MS_WINS1, go->winsaddr[0]);

    REJCIWINS(CI_MS_WINS2, go->winsaddr[1]);

    /*
     * If there are any remaining CIs, then this packet is bad.
     */
    if (len != 0)
        goto bad;
    /*
     * Now we can update state.
     */
    if (f->state != OPENED)
        *go = try;
    return 1;

bad:
    IPCPDEBUG(("ipcp_rejci: received bad Reject!"));
    return 0;
}


/*
 * ipcp_reqci - Check the peer's requested CIs and send appropriate response.
 * Callback from fsm_rconfreq, Receive Configure Request
 *
 * Returns: CONFACK, CONFNAK or CONFREJ and input packet modified
 * appropriately.  If reject_if_disagree is non-zero, doesn't return
 * CONFNAK; returns CONFREJ if it can't return CONFACK.
 */
static int
ipcp_reqci(fsm *f, u_char *inp, int *len, int reject_if_disagree)
{
    ipcp_options *wo = &ipcp_wantoptions[f->unit];
    ipcp_options *ho = &ipcp_hisoptions[f->unit];
    ipcp_options *ao = &ipcp_allowoptions[f->unit];
    u_char *cip, *next;         /* Pointer to current and next CIs */
    u_short cilen, citype;      /* Parsed len, type */
    u_short cishort;            /* Parsed short value */
    u_int32_t tl, ciaddr1, ciaddr2;/* Parsed address values */
    int rc = CONFACK;           /* Final packet return code */
    int orc;                    /* Individual option return code */
    u_char *p;                  /* Pointer to next char to parse */
    u_char *ucp = inp;          /* Pointer to current output char */
    int l = *len;               /* Length left */
    u_char maxslotindex, cflag;
    int d;

    /*
     * Reset all his options.
     */
    BZERO(ho, sizeof(*ho));
    
    /*
     * Process all his options.
     */
    next = inp;
    while (l) {
        orc = CONFACK;                  /* Assume success */
        cip = p = next;                 /* Remember begining of CI */
        if (l < 2 ||                    /* Not enough data for CI header or */
            p[1] < 2 ||                 /*  CI length too small or */
            p[1] > l) {                 /*  CI length too big? */
            IPCPDEBUG(("ipcp_reqci: bad CI length!"));
            orc = CONFREJ;              /* Reject bad CI */
            cilen = l;                  /* Reject till end of packet */
            l = 0;                      /* Don't loop again */
            goto endswitch;
        }
        GETCHAR(citype, p);             /* Parse CI type */
        GETCHAR(cilen, p);              /* Parse CI length */
        l -= cilen;                     /* Adjust remaining length */
        next += cilen;                  /* Step to next CI */

        switch (citype) {               /* Check CI type */
        case CI_ADDRS:
            if (!ao->old_addrs || ho->neg_addr ||
                cilen != CILEN_ADDRS) { /* Check CI length */
                orc = CONFREJ;          /* Reject CI */
                break;
            }

            /*
             * If he has no address, or if we both have his address but
             * disagree about it, then NAK it with our idea.
             * In particular, if we don't know his address, but he does,
             * then accept it.
             */
            GETLONG(tl, p);             /* Parse source address (his) */
            ciaddr1 = htonl(tl);
            if (ciaddr1 != wo->hisaddr
                && (ciaddr1 == 0 || !wo->accept_remote)) {
                orc = CONFNAK;
                if (!reject_if_disagree) {
                    DECPTR(sizeof(u_int32_t), p);
                    tl = ntohl(wo->hisaddr);
                    PUTLONG(tl, p);
                }
            } else if (ciaddr1 == 0 && wo->hisaddr == 0) {
                /*
                 * If neither we nor he knows his address, reject the option.
                 */
                orc = CONFREJ;
                wo->req_addr = 0;       /* don't NAK with 0.0.0.0 later */
                break;
            }

            /*
             * If he doesn't know our address, or if we both have our address
             * but disagree about it, then NAK it with our idea.
             */
            GETLONG(tl, p);             /* Parse desination address (ours) */
            ciaddr2 = htonl(tl);
            if (ciaddr2 != wo->ouraddr) {
                if (ciaddr2 == 0 || !wo->accept_local) {
                    orc = CONFNAK;
                    if (!reject_if_disagree && wo->old_addrs) {
                        DECPTR(sizeof(u_int32_t), p);
                        tl = ntohl(wo->ouraddr);
                        PUTLONG(tl, p);
                    }
                } else {
                    wo->ouraddr = ciaddr2;      /* accept peer's idea */
                }
            }

            ho->old_addrs = 1;
            ho->hisaddr = ciaddr1;
            ho->ouraddr = ciaddr2;
            break;

        case CI_ADDR:
            if (!ao->neg_addr || ho->old_addrs ||
                cilen != CILEN_ADDR) {  /* Check CI length */
                orc = CONFREJ;          /* Reject CI */
                break;
            }

            /*
             * If he has no address, or if we both have his address but
             * disagree about it, then NAK it with our idea.
             * In particular, if we don't know his address, but he does,
             * then accept it.
             */
            GETLONG(tl, p);     /* Parse source address (his) */
            ciaddr1 = htonl(tl);
            if (ciaddr1 != wo->hisaddr
                && (ciaddr1 == 0 || !wo->accept_remote)) {
                orc = CONFNAK;
                if (!reject_if_disagree) {
                    DECPTR(sizeof(u_int32_t), p);
                    tl = ntohl(wo->hisaddr);
                    PUTLONG(tl, p);
                }
            } else if (ciaddr1 == 0 && wo->hisaddr == 0) {
                /*
                 * Don't ACK an address of 0.0.0.0 - reject it instead.
                 */
                orc = CONFREJ;
                wo->req_addr = 0;       /* don't NAK with 0.0.0.0 later */
                break;
            }
        
            ho->neg_addr = 1;
            ho->hisaddr = ciaddr1;
            break;

        case CI_MS_DNS1:
        case CI_MS_DNS2:
            /* Microsoft primary or secondary DNS request */
            d = citype == CI_MS_DNS2;

            /* If we do not have a DNS address then we cannot send it */
            if (ao->dnsaddr[d] == 0 ||
                cilen != CILEN_ADDR) {  /* Check CI length */
                orc = CONFREJ;          /* Reject CI */
                break;
            }
            GETLONG(tl, p);
            if (htonl(tl) != ao->dnsaddr[d]) {
                DECPTR(sizeof(u_int32_t), p);
                tl = ntohl(ao->dnsaddr[d]);
                PUTLONG(tl, p);
                orc = CONFNAK;
            }
            break;

        case CI_MS_WINS1:
        case CI_MS_WINS2:
            /* Microsoft primary or secondary WINS request */
            d = citype == CI_MS_WINS2;

            /* If we do not have a DNS address then we cannot send it */
            if (ao->winsaddr[d] == 0 ||
                cilen != CILEN_ADDR) {  /* Check CI length */
                orc = CONFREJ;          /* Reject CI */
                break;
            }
            GETLONG(tl, p);
            if (htonl(tl) != ao->winsaddr[d]) {
                DECPTR(sizeof(u_int32_t), p);
                tl = ntohl(ao->winsaddr[d]);
                PUTLONG(tl, p);
                orc = CONFNAK;
            }
            break;
        
        case CI_COMPRESSTYPE:
            if (!ao->neg_vj ||
                (cilen != CILEN_VJ && cilen != CILEN_COMPRESS)) {
                orc = CONFREJ;
                break;
            }
            GETSHORT(cishort, p);

            if (!(cishort == IPCP_VJ_COMP ||
                  (cishort == IPCP_VJ_COMP_OLD && cilen == CILEN_COMPRESS))) {
                orc = CONFREJ;
                break;
            }

            ho->neg_vj = 1;
            ho->vj_protocol = cishort;
            if (cilen == CILEN_VJ) {
                GETCHAR(maxslotindex, p);
                if (maxslotindex > ao->maxslotindex) { 
                    orc = CONFNAK;
                    if (!reject_if_disagree){
                        DECPTR(1, p);
                        PUTCHAR(ao->maxslotindex, p);
                    }
                }
                GETCHAR(cflag, p);
                if (cflag && !ao->cflag) {
                    orc = CONFNAK;
                    if (!reject_if_disagree){
                        DECPTR(1, p);
                        PUTCHAR(wo->cflag, p);
                    }
                }
                ho->maxslotindex = maxslotindex;
                ho->cflag = cflag;
            } else {
                ho->old_vj = 1;
                ho->maxslotindex = MAX_STATES - 1;
                ho->cflag = 1;
            }
            break;

        default:
            orc = CONFREJ;
            break;
        }
endswitch:
        if (orc == CONFACK &&           /* Good CI */
            rc != CONFACK)              /*  but prior CI wasnt? */
            continue;                   /* Don't send this one */

        if (orc == CONFNAK) {           /* Nak this CI? */
            if (reject_if_disagree)     /* Getting fed up with sending NAKs? */
                orc = CONFREJ;          /* Get tough if so */
            else {
                if (rc == CONFREJ)      /* Rejecting prior CI? */
                    continue;           /* Don't send this one */
                if (rc == CONFACK) {    /* Ack'd all prior CIs? */
                    rc = CONFNAK;       /* Not anymore... */
                    ucp = inp;          /* Backup */
                }
            }
        }

        if (orc == CONFREJ &&           /* Reject this CI */
            rc != CONFREJ) {            /*  but no prior ones? */
            rc = CONFREJ;
            ucp = inp;                  /* Backup */
        }

        /* Need to move CI? */
        if (ucp != cip)
            BCOPY(cip, ucp, cilen);     /* Move it */

        /* Update output pointer */
        INCPTR(cilen, ucp);
    }

    /*
     * If we aren't rejecting this packet, and we want to negotiate
     * their address, and they didn't send their address, then we
     * send a NAK with a CI_ADDR option appended.  We assume the
     * input buffer is long enough that we can append the extra
     * option safely.
     */
    if (rc != CONFREJ && !ho->neg_addr && !ho->old_addrs &&
        wo->req_addr && !reject_if_disagree &&
        ((wo->hisaddr && !wo->accept_remote) || !noremoteip)) {
        if (rc == CONFACK) {
            rc = CONFNAK;
            ucp = inp;                  /* reset pointer */
            wo->req_addr = 0;           /* don't ask again */
        }
        PUTCHAR(CI_ADDR, ucp);
        PUTCHAR(CILEN_ADDR, ucp);
        tl = ntohl(wo->hisaddr);
        PUTLONG(tl, ucp);
    }

    *len = ucp - inp;                   /* Compute output length */
    IPCPDEBUG(("ipcp: returning Configure-%s", CODENAME(rc)));
    return (rc);                        /* Return final code */
}


/*
 * ip_check_options - check that any IP-related options are OK,
 * and assign appropriate defaults.
 */
static void
ip_check_options(void)
{
    struct hostent *hp;
    u_int32_t local;
    ipcp_options *wo = &ipcp_wantoptions[0];

    /*
     * Default our local IP address based on our hostname.
     * If local IP address already given, don't bother.
     */
    if (wo->ouraddr == 0 && !disable_defaultip) {
        /*
         * Look up our hostname (possibly with domain name appended)
         * and take the first IP address as our local IP address.
         * If there isn't an IP address for our hostname, too bad.
         */
        wo->accept_local = 1;   /* don't insist on this default value */
        if ((hp = gethostbyname(hostname)) != NULL) {
            local = *(u_int32_t *)hp->h_addr;
            if (local != 0 && !bad_ip_adrs(local))
                wo->ouraddr = local;
        }
    }
    ask_for_local = wo->ouraddr != 0 || !disable_defaultip;
}


/*
 * ip_demand_conf - configure the interface as though
 * IPCP were up, for use with dial-on-demand.
 */
static int
ip_demand_conf(int u)
{
    ipcp_options *wo = &ipcp_wantoptions[u];

    if (wo->hisaddr == 0 && !noremoteip) {
        /* make up an arbitrary address for the peer */
        wo->hisaddr = htonl(0x0a707070 + ifunit);
        wo->accept_remote = 1;
    }
    if (wo->ouraddr == 0) {
        /* make up an arbitrary address for us */
        wo->ouraddr = htonl(0x0a404040 + ifunit);
        wo->accept_local = 1;
        ask_for_local = 0;      /* don't tell the peer this address */
    }
    if (!sifaddr(u, wo->ouraddr, wo->hisaddr, GetMask(wo->ouraddr)))
        return 0;
    ipcp_script(_PATH_IPPREUP, 1);
    if (!sifup(u))
        return 0;
    if (!sifnpmode(u, PPP_IP, NPMODE_QUEUE))
        return 0;
    if (wo->default_route)
        if (sifdefaultroute(u, wo->ouraddr, wo->hisaddr,
                                            wo->replace_default_route))
            default_route_set[u] = 1;
    if (wo->proxy_arp)
        if (sifproxyarp(u, wo->hisaddr))
            proxy_arp_set[u] = 1;

    notice("local  IP address %I", wo->ouraddr);
    if (wo->hisaddr)
        notice("remote IP address %I", wo->hisaddr);

    return 1;
}


/*
 * ipcp_up - IPCP has come UP.
 *
 * Configure the IP network interface appropriately and bring it up.
 */
static void
ipcp_up(fsm *f)
{
    u_int32_t mask;
    ipcp_options *ho = &ipcp_hisoptions[f->unit];
    ipcp_options *go = &ipcp_gotoptions[f->unit];
    ipcp_options *wo = &ipcp_wantoptions[f->unit];
    int ifindex;

    IPCPDEBUG(("ipcp: up"));

    /*
     * We must have a non-zero IP address for both ends of the link.
     */

    if (wo->hisaddr && !wo->accept_remote && (!(ho->neg_addr || ho->old_addrs) || ho->hisaddr != wo->hisaddr)) {
        error("Peer refused to agree to his IP address");
        ipcp_close(f->unit, "Refused his IP address");
        return;
    }
    if (!ho->neg_addr && !ho->old_addrs)
        ho->hisaddr = wo->hisaddr;

    if (!(go->neg_addr || go->old_addrs) && (wo->neg_addr || wo->old_addrs)
        && wo->ouraddr != 0) {
        error("Peer refused to agree to our IP address");
        ipcp_close(f->unit, "Refused our IP address");
        return;
    }
    if (go->ouraddr == 0) {
        error("Could not determine local IP address");
        ipcp_close(f->unit, "Could not determine local IP address");
        return;
    }
    if (ho->hisaddr == 0 && !noremoteip) {
        ho->hisaddr = htonl(0x0a404040 + ifunit);
        warn("Could not determine remote IP address: defaulting to %I",
             ho->hisaddr);
    }
    script_setenv("IPLOCAL", ip_ntoa(go->ouraddr), 0);
    if (ho->hisaddr != 0)
        script_setenv("IPREMOTE", ip_ntoa(ho->hisaddr), 1);

    if (!go->req_dns1)
            go->dnsaddr[0] = 0;
    if (!go->req_dns2)
            go->dnsaddr[1] = 0;
    if (go->dnsaddr[0])
        script_setenv("DNS1", ip_ntoa(go->dnsaddr[0]), 0);
    if (go->dnsaddr[1])
        script_setenv("DNS2", ip_ntoa(go->dnsaddr[1]), 0);
    if (usepeerdns && (go->dnsaddr[0] || go->dnsaddr[1])) {
        script_setenv("USEPEERDNS", "1", 0);
        create_resolv(go->dnsaddr[0], go->dnsaddr[1]);
    }

    /*
     * Check that the peer is allowed to use the IP address it wants.
     */
    if (ho->hisaddr != 0 && !auth_ip_addr(f->unit, ho->hisaddr)) {
        error("Peer is not authorized to use remote address %I", ho->hisaddr);
        ipcp_close(f->unit, "Unauthorized remote IP address");
        return;
    }

    /* set tcp compression */
    sifvjcomp(f->unit, ho->neg_vj, ho->cflag, ho->maxslotindex);

    /*
     * If we are doing dial-on-demand, the interface is already
     * configured, so we put out any saved-up packets, then set the
     * interface to pass IP packets.
     */
    if (demand) {
        if (go->ouraddr != wo->ouraddr || ho->hisaddr != wo->hisaddr) {
            ipcp_clear_addrs(f->unit, wo->ouraddr, wo->hisaddr,
                                      wo->replace_default_route);
            if (go->ouraddr != wo->ouraddr) {
                warn("Local IP address changed to %I", go->ouraddr);
                script_setenv("OLDIPLOCAL", ip_ntoa(wo->ouraddr), 0);
                wo->ouraddr = go->ouraddr;
            } else
                script_unsetenv("OLDIPLOCAL");
            if (ho->hisaddr != wo->hisaddr) {
                warn("Remote IP address changed to %I", ho->hisaddr);
                if (wo->hisaddr != 0)
                    script_setenv("OLDIPREMOTE", ip_ntoa(wo->hisaddr), 0);
                wo->hisaddr = ho->hisaddr;
            } else
                script_unsetenv("OLDIPREMOTE");

            /* Set the interface to the new addresses */
            mask = GetMask(go->ouraddr);
            if (!sifaddr(f->unit, go->ouraddr, ho->hisaddr, mask)) {
                if (debug)
                    warn("Interface configuration failed");
                ipcp_close(f->unit, "Interface configuration failed");
                return;
            }

            /* assign a default route through the interface if required */
            if (ipcp_wantoptions[f->unit].default_route) 
                if (sifdefaultroute(f->unit, go->ouraddr, ho->hisaddr,
                                             wo->replace_default_route))
                    default_route_set[f->unit] = 1;

            /* Make a proxy ARP entry if requested. */
            if (ho->hisaddr != 0 && ipcp_wantoptions[f->unit].proxy_arp)
                if (sifproxyarp(f->unit, ho->hisaddr))
                    proxy_arp_set[f->unit] = 1;

        }
        demand_rexmit(PPP_IP);
        sifnpmode(f->unit, PPP_IP, NPMODE_PASS);

    } else {
        /*
         * Set IP addresses and (if specified) netmask.
         */
        mask = GetMask(go->ouraddr);

#if !(defined(SVR4) && (defined(SNI) || defined(__USLC__)))
        if (!sifaddr(f->unit, go->ouraddr, ho->hisaddr, mask)) {
            if (debug)
                warn("Interface configuration failed");
            ipcp_close(f->unit, "Interface configuration failed");
            return;
        }
#endif

        ifindex = if_nametoindex(ifname);

        /* run the pre-up script, if any, and wait for it to finish */
        ipcp_script(_PATH_IPPREUP, 1);

        /* check if preup script renamed the interface */
        if (!if_indextoname(ifindex, ifname)) {
            error("Interface index %d failed to get renamed by a pre-up script", ifindex);
            ipcp_close(f->unit, "Interface configuration failed");
            return;
        }

        /* bring the interface up for IP */
        if (!sifup(f->unit)) {
            if (debug)
                warn("Interface failed to come up");
            ipcp_close(f->unit, "Interface configuration failed");
            return;
        }

#if (defined(SVR4) && (defined(SNI) || defined(__USLC__)))
        if (!sifaddr(f->unit, go->ouraddr, ho->hisaddr, mask)) {
            if (debug)
                warn("Interface configuration failed");
            ipcp_close(f->unit, "Interface configuration failed");
            return;
        }
#endif
        sifnpmode(f->unit, PPP_IP, NPMODE_PASS);

        /* assign a default route through the interface if required */
        if (ipcp_wantoptions[f->unit].default_route) 
            if (sifdefaultroute(f->unit, go->ouraddr, ho->hisaddr,
                                         wo->replace_default_route))
                default_route_set[f->unit] = 1;

        /* Make a proxy ARP entry if requested. */
        if (ho->hisaddr != 0 && ipcp_wantoptions[f->unit].proxy_arp)
            if (sifproxyarp(f->unit, ho->hisaddr))
                proxy_arp_set[f->unit] = 1;

        ipcp_wantoptions[0].ouraddr = go->ouraddr;

        notice("local  IP address %I", go->ouraddr);
        if (ho->hisaddr != 0)
            notice("remote IP address %I", ho->hisaddr);
        if (go->dnsaddr[0])
            notice("primary   DNS address %I", go->dnsaddr[0]);
        if (go->dnsaddr[1])
            notice("secondary DNS address %I", go->dnsaddr[1]);
    }

    reset_link_stats(f->unit);

    np_up(f->unit, PPP_IP);
    ipcp_is_up = 1;

    notify(ip_up_notifier, 0);
    if (ip_up_hook)
        ip_up_hook();

    /*
     * Execute the ip-up script, like this:
     *  /etc/ppp/ip-up interface tty speed local-IP remote-IP
     */
    if (ipcp_script_state == s_down && ipcp_script_pid == 0) {
        ipcp_script_state = s_up;
        ipcp_script(path_ipup, 0);
    }
}


/*
 * ipcp_down - IPCP has gone DOWN.
 *
 * Take the IP network interface down, clear its addresses
 * and delete routes through it.
 */
static void
ipcp_down(fsm *f)
{
    IPCPDEBUG(("ipcp: down"));
    /* XXX a bit IPv4-centric here, we only need to get the stats
     * before the interface is marked down. */
    /* XXX more correct: we must get the stats before running the notifiers,
     * at least for the radius plugin */
    update_link_stats(f->unit);
    notify(ip_down_notifier, 0);
    if (ip_down_hook)
        ip_down_hook();
    if (ipcp_is_up) {
        ipcp_is_up = 0;
        np_down(f->unit, PPP_IP);
    }
    sifvjcomp(f->unit, 0, 0, 0);

    print_link_stats(); /* _after_ running the notifiers and ip_down_hook(),
                         * because print_link_stats() sets link_stats_valid
                         * to 0 (zero) */

    /*
     * If we are doing dial-on-demand, set the interface
     * to queue up outgoing packets (for now).
     */
    if (demand) {
        sifnpmode(f->unit, PPP_IP, NPMODE_QUEUE);
    } else {
        sifnpmode(f->unit, PPP_IP, NPMODE_DROP);
        sifdown(f->unit);
        ipcp_clear_addrs(f->unit, ipcp_gotoptions[f->unit].ouraddr,
                         ipcp_hisoptions[f->unit].hisaddr, 0);
    }

    /* Execute the ip-down script */
    if (ipcp_script_state == s_up && ipcp_script_pid == 0) {
        ipcp_script_state = s_down;
        ipcp_script(path_ipdown, 0);
    }
}


/*
 * ipcp_clear_addrs() - clear the interface addresses, routes,
 * proxy arp entries, etc.
 */
static void
ipcp_clear_addrs(int unit, u_int32_t ouraddr, u_int32_t hisaddr, bool replacedefaultroute)
{
    if (proxy_arp_set[unit]) {
        cifproxyarp(unit, hisaddr);
        proxy_arp_set[unit] = 0;
    }
    /* If replacedefaultroute, sifdefaultroute will be called soon
     * with replacedefaultroute set and that will overwrite the current
     * default route. This is the case only when doing demand, otherwise
     * during demand, this cifdefaultroute would restore the old default
     * route which is not what we want in this case. In the non-demand
     * case, we'll delete the default route and restore the old if there
     * is one saved by an sifdefaultroute with replacedefaultroute.
     */
    if (!replacedefaultroute && default_route_set[unit]) {
        cifdefaultroute(unit, ouraddr, hisaddr);
        default_route_set[unit] = 0;
    }
    cifaddr(unit, ouraddr, hisaddr);
}


/*
 * ipcp_finished - possibly shut down the lower layers.
 */
static void
ipcp_finished(fsm *f)
{
        if (ipcp_is_open) {
                ipcp_is_open = 0;
                np_finished(f->unit, PPP_IP);
        }
}


/*
 * ipcp_script_done - called when the ip-up or ip-down script
 * has finished.
 */
static void
ipcp_script_done(void *arg)
{
    ipcp_script_pid = 0;
    switch (ipcp_script_state) {
    case s_up:
        if (ipcp_fsm[0].state != OPENED) {
            ipcp_script_state = s_down;
            ipcp_script(path_ipdown, 0);
        }
        break;
    case s_down:
        if (ipcp_fsm[0].state == OPENED) {
            ipcp_script_state = s_up;
            ipcp_script(path_ipup, 0);
        }
        break;
    }
}


/*
 * ipcp_script - Execute a script with arguments
 * interface-name tty-name speed local-IP remote-IP.
 */
static void
ipcp_script(char *script, int wait)
{
    char strspeed[32], strlocal[32], strremote[32];
    char *argv[8];

    slprintf(strspeed, sizeof(strspeed), "%d", baud_rate);
    slprintf(strlocal, sizeof(strlocal), "%I", ipcp_gotoptions[0].ouraddr);
    slprintf(strremote, sizeof(strremote), "%I", ipcp_hisoptions[0].hisaddr);

    argv[0] = script;
    argv[1] = ifname;
    argv[2] = devnam;
    argv[3] = strspeed;
    argv[4] = strlocal;
    argv[5] = strremote;
    argv[6] = ipparam;
    argv[7] = NULL;
    if (wait)
        run_program(script, argv, 0, NULL, NULL, 1);
    else
        ipcp_script_pid = run_program(script, argv, 0, ipcp_script_done,
                                      NULL, 0);
}

/*
 * create_resolv - create the replacement resolv.conf file
 */
static void
create_resolv(u_int32_t peerdns1, u_int32_t peerdns2)
{
    FILE *f;

    f = fopen(_PATH_RESOLV, "w");
    if (f == NULL) {
        error("Failed to create %s: %m", _PATH_RESOLV);
        return;
    }

    if (peerdns1)
        fprintf(f, "nameserver %s\n", ip_ntoa(peerdns1));

    if (peerdns2)
        fprintf(f, "nameserver %s\n", ip_ntoa(peerdns2));

    if (ferror(f))
        error("Write failed to %s: %m", _PATH_RESOLV);

    fclose(f);
}

/*
 * ipcp_printpkt - print the contents of an IPCP packet.
 */
static char *ipcp_codenames[] = {
    "ConfReq", "ConfAck", "ConfNak", "ConfRej",
    "TermReq", "TermAck", "CodeRej"
};

static int
ipcp_printpkt(u_char *p, int plen,
              void (*printer) (void *, char *, ...), void *arg)
{
    int code, id, len, olen;
    u_char *pstart, *optend;
    u_short cishort;
    u_int32_t cilong;

    if (plen < HEADERLEN)
        return 0;
    pstart = p;
    GETCHAR(code, p);
    GETCHAR(id, p);
    GETSHORT(len, p);
    if (len < HEADERLEN || len > plen)
        return 0;

    if (code >= 1 && code <= sizeof(ipcp_codenames) / sizeof(char *))
        printer(arg, " %s", ipcp_codenames[code-1]);
    else
        printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= HEADERLEN;
    switch (code) {
    case CONFREQ:
    case CONFACK:
    case CONFNAK:
    case CONFREJ:
        /* print option list */
        while (len >= 2) {
            GETCHAR(code, p);
            GETCHAR(olen, p);
            p -= 2;
            if (olen < 2 || olen > len) {
                break;
            }
            printer(arg, " <");
            len -= olen;
            optend = p + olen;
            switch (code) {
            case CI_ADDRS:
                if (olen == CILEN_ADDRS) {
                    p += 2;
                    GETLONG(cilong, p);
                    printer(arg, "addrs %I", htonl(cilong));
                    GETLONG(cilong, p);
                    printer(arg, " %I", htonl(cilong));
                }
                break;
            case CI_COMPRESSTYPE:
                if (olen >= CILEN_COMPRESS) {
                    p += 2;
                    GETSHORT(cishort, p);
                    printer(arg, "compress ");
                    switch (cishort) {
                    case IPCP_VJ_COMP:
                        printer(arg, "VJ");
                        break;
                    case IPCP_VJ_COMP_OLD:
                        printer(arg, "old-VJ");
                        break;
                    default:
                        printer(arg, "0x%x", cishort);
                    }
                }
                break;
            case CI_ADDR:
                if (olen == CILEN_ADDR) {
                    p += 2;
                    GETLONG(cilong, p);
                    printer(arg, "addr %I", htonl(cilong));
                }
                break;
            case CI_MS_DNS1:
            case CI_MS_DNS2:
                p += 2;
                GETLONG(cilong, p);
                printer(arg, "ms-dns%d %I", (code == CI_MS_DNS1? 1: 2),
                        htonl(cilong));
                break;
            case CI_MS_WINS1:
            case CI_MS_WINS2:
                p += 2;
                GETLONG(cilong, p);
                printer(arg, "ms-wins %I", htonl(cilong));
                break;
            }
            while (p < optend) {
                GETCHAR(code, p);
                printer(arg, " %.2x", code);
            }
            printer(arg, ">");
        }
        break;

    case TERMACK:
    case TERMREQ:
        if (len > 0 && *p >= ' ' && *p < 0x7f) {
            printer(arg, " ");
            print_string((char *)p, len, printer, arg);
            p += len;
            len = 0;
        }
        break;
    }

    /* print the rest of the bytes in the packet */
    for (; len > 0; --len) {
        GETCHAR(code, p);
        printer(arg, " %.2x", code);
    }

    return p - pstart;
}

/*
 * ip_active_pkt - see if this IP packet is worth bringing the link up for.
 * We don't bring the link up for IP fragments or for TCP FIN packets
 * with no data.
 */
#define IP_HDRLEN       20      /* bytes */
#define IP_OFFMASK      0x1fff
#ifndef IPPROTO_TCP
#define IPPROTO_TCP     6
#endif
#define TCP_HDRLEN      20
#define TH_FIN          0x01

/*
 * We use these macros because the IP header may be at an odd address,
 * and some compilers might use word loads to get th_off or ip_hl.
 */

#define net_short(x)    (((x)[0] << 8) + (x)[1])
#define get_iphl(x)     (((unsigned char *)(x))[0] & 0xF)
#define get_ipoff(x)    net_short((unsigned char *)(x) + 6)
#define get_ipproto(x)  (((unsigned char *)(x))[9])
#define get_tcpoff(x)   (((unsigned char *)(x))[12] >> 4)
#define get_tcpflags(x) (((unsigned char *)(x))[13])

static int
ip_active_pkt(u_char *pkt, int len)
{
    u_char *tcp;
    int hlen;

    len -= PPP_HDRLEN;
    pkt += PPP_HDRLEN;
    if (len < IP_HDRLEN)
        return 0;
    if ((get_ipoff(pkt) & IP_OFFMASK) != 0)
        return 0;
    if (get_ipproto(pkt) != IPPROTO_TCP)
        return 1;
    hlen = get_iphl(pkt) * 4;
    if (len < hlen + TCP_HDRLEN)
        return 0;
    tcp = pkt + hlen;
    if ((get_tcpflags(tcp) & TH_FIN) != 0 && len == hlen + get_tcpoff(tcp) * 4)
        return 0;
    return 1;
}