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lcp.c

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

#ifndef lint
static char rcsid[] = "$FreeBSD: src/usr.sbin/pppd/lcp.c,v 1.11.30.1 2008/11/25 02:59:29 kensmith Exp $";
#endif

/*
 * TODO:
 */

#include <stdio.h>
#include <string.h>
#include <syslog.h>
#include <assert.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>

#include "pppd.h"
#include "fsm.h"
#include "lcp.h"
#include "chap.h"
#include "magic.h"

/* global vars */
fsm lcp_fsm[NUM_PPP];               /* LCP fsm structure (global)*/
lcp_options lcp_wantoptions[NUM_PPP];     /* Options that we want to request */
lcp_options lcp_gotoptions[NUM_PPP];      /* Options that peer ack'd */
lcp_options lcp_allowoptions[NUM_PPP];    /* Options we allow peer to request */
lcp_options lcp_hisoptions[NUM_PPP];      /* Options that we ack'd */
u_int32_t xmit_accm[NUM_PPP][8];          /* extended transmit ACCM */

static u_int32_t lcp_echos_pending = 0;   /* Number of outstanding echo msgs */
static u_int32_t lcp_echo_number   = 0;   /* ID number of next echo frame */
static u_int32_t lcp_echo_timer_running = 0;  /* TRUE if a timer is running */

static u_char nak_buffer[PPP_MRU];  /* where we construct a nak packet */

/*
 * Callbacks for fsm code.  (CI = Configuration Information)
 */
static void lcp_resetci __P((fsm *));     /* Reset our CI */
static int  lcp_cilen __P((fsm *));       /* Return length of our CI */
static void lcp_addci __P((fsm *, u_char *, int *)); /* Add our CI to pkt */
static int  lcp_ackci __P((fsm *, u_char *, int)); /* Peer ack'd our CI */
static int  lcp_nakci __P((fsm *, u_char *, int)); /* Peer nak'd our CI */
static int  lcp_rejci __P((fsm *, u_char *, int)); /* Peer rej'd our CI */
static int  lcp_reqci __P((fsm *, u_char *, int *, int)); /* Rcv peer CI */
static void lcp_up __P((fsm *));          /* We're UP */
static void lcp_down __P((fsm *));        /* We're DOWN */
static void lcp_starting __P((fsm *));    /* We need lower layer up */
static void lcp_finished __P((fsm *));    /* We need lower layer down */
static int  lcp_extcode __P((fsm *, int, int, u_char *, int));
static void lcp_rprotrej __P((fsm *, u_char *, int));

/*
 * routines to send LCP echos to peer
 */

static void lcp_echo_lowerup __P((int));
static void lcp_echo_lowerdown __P((int));
static void LcpEchoTimeout __P((void *));
static void lcp_received_echo_reply __P((fsm *, int, u_char *, int));
static void LcpSendEchoRequest __P((fsm *));
static void LcpLinkFailure __P((fsm *));
static void LcpEchoCheck __P((fsm *));

static fsm_callbacks lcp_callbacks = {    /* LCP callback routines */
    lcp_resetci,        /* Reset our Configuration Information */
    lcp_cilen,                /* Length of our Configuration Information */
    lcp_addci,                /* Add our Configuration Information */
    lcp_ackci,                /* ACK our Configuration Information */
    lcp_nakci,                /* NAK our Configuration Information */
    lcp_rejci,                /* Reject our Configuration Information */
    lcp_reqci,                /* Request peer's Configuration Information */
    lcp_up,             /* Called when fsm reaches OPENED state */
    lcp_down,                 /* Called when fsm leaves OPENED state */
    lcp_starting,       /* Called when we want the lower layer up */
    lcp_finished,       /* Called when we want the lower layer down */
    NULL,               /* Called when Protocol-Reject received */
    NULL,               /* Retransmission is necessary */
    lcp_extcode,        /* Called to handle LCP-specific codes */
    "LCP"               /* String name of protocol */
};

/*
 * Protocol entry points.
 * Some of these are called directly.
 */

static void lcp_init __P((int));
static void lcp_input __P((int, u_char *, int));
static void lcp_protrej __P((int));
static int  lcp_printpkt __P((u_char *, int,
                        void (*) __P((void *, char *, ...)), void *));

struct protent lcp_protent = {
    PPP_LCP,
    lcp_init,
    lcp_input,
    lcp_protrej,
    lcp_lowerup,
    lcp_lowerdown,
    lcp_open,
    lcp_close,
    lcp_printpkt,
    NULL,
    1,
    "LCP",
    NULL,
    NULL,
    NULL
};

int lcp_loopbackfail = DEFLOOPBACKFAIL;

/*
 * Length of each type of configuration option (in octets)
 */
#define CILEN_VOID      2
#define CILEN_CHAR      3
#define CILEN_SHORT     4     /* CILEN_VOID + sizeof(short) */
#define CILEN_CHAP      5     /* CILEN_VOID + sizeof(short) + 1 */
#define CILEN_LONG      6     /* CILEN_VOID + sizeof(long) */
#define CILEN_LQR 8     /* CILEN_VOID + sizeof(short) + sizeof(long) */
#define CILEN_CBCP      3

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


/*
 * lcp_init - Initialize LCP.
 */
static void
lcp_init(unit)
    int unit;
{
    fsm *f = &lcp_fsm[unit];
    lcp_options *wo = &lcp_wantoptions[unit];
    lcp_options *ao = &lcp_allowoptions[unit];

    f->unit = unit;
    f->protocol = PPP_LCP;
    f->callbacks = &lcp_callbacks;

    fsm_init(f);

    wo->passive = 0;
    wo->silent = 0;
    wo->restart = 0;                /* Set to 1 in kernels or multi-line
                                 implementations */
    wo->neg_mru = 1;
    wo->mru = DEFMRU;
    wo->neg_asyncmap = 0;
    wo->asyncmap = 0;
    wo->neg_chap = 0;               /* Set to 1 on server */
    wo->neg_upap = 0;               /* Set to 1 on server */
    wo->chap_mdtype = CHAP_DIGEST_MD5;
    wo->neg_magicnumber = 1;
    wo->neg_pcompression = 1;
    wo->neg_accompression = 1;
    wo->neg_lqr = 0;                /* no LQR implementation yet */
    wo->neg_cbcp = 0;

    ao->neg_mru = 1;
    ao->mru = MAXMRU;
    ao->neg_asyncmap = 1;
    ao->asyncmap = 0;
    ao->neg_chap = 1;
    ao->chap_mdtype = CHAP_DIGEST_MD5;
    ao->neg_upap = 1;
    ao->neg_magicnumber = 1;
    ao->neg_pcompression = 1;
    ao->neg_accompression = 1;
    ao->neg_lqr = 0;                /* no LQR implementation yet */
#ifdef CBCP_SUPPORT
    ao->neg_cbcp = 1;
#else
    ao->neg_cbcp = 0;
#endif

    memset(xmit_accm[unit], 0, sizeof(xmit_accm[0]));
    xmit_accm[unit][3] = 0x60000000;
}


/*
 * lcp_open - LCP is allowed to come up.
 */
void
lcp_open(unit)
    int unit;
{
    fsm *f = &lcp_fsm[unit];
    lcp_options *wo = &lcp_wantoptions[unit];

    f->flags = 0;
    if (wo->passive)
      f->flags |= OPT_PASSIVE;
    if (wo->silent)
      f->flags |= OPT_SILENT;
    fsm_open(f);
}


/*
 * lcp_close - Take LCP down.
 */
void
lcp_close(unit, reason)
    int unit;
    char *reason;
{
    fsm *f = &lcp_fsm[unit];

    if (phase != PHASE_DEAD)
      phase = PHASE_TERMINATE;
    if (f->state == STOPPED && f->flags & (OPT_PASSIVE|OPT_SILENT)) {
      /*
       * This action is not strictly according to the FSM in RFC1548,
       * but it does mean that the program terminates if you do a
       * lcp_close() in passive/silent mode when a connection hasn't
       * been established.
       */
      f->state = CLOSED;
      lcp_finished(f);

    } else
      fsm_close(&lcp_fsm[unit], reason);
}


/*
 * lcp_lowerup - The lower layer is up.
 */
void
lcp_lowerup(unit)
    int unit;
{
    lcp_options *wo = &lcp_wantoptions[unit];

    /*
     * Don't use A/C or protocol compression on transmission,
     * but accept A/C and protocol compressed packets
     * if we are going to ask for A/C and protocol compression.
     */
    ppp_set_xaccm(unit, xmit_accm[unit]);
    ppp_send_config(unit, PPP_MRU, 0xffffffff, 0, 0);
    ppp_recv_config(unit, PPP_MRU, 0xffffffff,
                wo->neg_pcompression, wo->neg_accompression);
    peer_mru[unit] = PPP_MRU;
    lcp_allowoptions[unit].asyncmap = xmit_accm[unit][0];

    fsm_lowerup(&lcp_fsm[unit]);
}


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


/*
 * lcp_input - Input LCP packet.
 */
static void
lcp_input(unit, p, len)
    int unit;
    u_char *p;
    int len;
{
    fsm *f = &lcp_fsm[unit];

    fsm_input(f, p, len);
}


/*
 * lcp_extcode - Handle a LCP-specific code.
 */
static int
lcp_extcode(f, code, id, inp, len)
    fsm *f;
    int code, id;
    u_char *inp;
    int len;
{
    u_char *magp;

    switch( code ){
    case PROTREJ:
      lcp_rprotrej(f, inp, len);
      break;
    
    case ECHOREQ:
      if (f->state != OPENED)
          break;
      LCPDEBUG((LOG_INFO, "lcp: Echo-Request, Rcvd id %d", id));
      magp = inp;
      PUTLONG(lcp_gotoptions[f->unit].magicnumber, magp);
      fsm_sdata(f, ECHOREP, id, inp, len);
      break;
    
    case ECHOREP:
      lcp_received_echo_reply(f, id, inp, len);
      break;

    case DISCREQ:
      break;

    default:
      return 0;
    }
    return 1;
}

    
/*
 * lcp_rprotrej - Receive a Protocol-Reject.
 *
 * Figure out which protocol is rejected and inform it.
 */
static void
lcp_rprotrej(f, inp, len)
    fsm *f;
    u_char *inp;
    int len;
{
    int i;
    struct protent *protp;
    u_short prot;

    LCPDEBUG((LOG_INFO, "lcp_rprotrej."));

    if (len < sizeof (u_short)) {
      LCPDEBUG((LOG_INFO,
              "lcp_rprotrej: Rcvd short Protocol-Reject packet!"));
      return;
    }

    GETSHORT(prot, inp);

    LCPDEBUG((LOG_INFO,
            "lcp_rprotrej: Rcvd Protocol-Reject packet for %x!",
            prot));

    /*
     * Protocol-Reject packets received in any state other than the LCP
     * OPENED state SHOULD be silently discarded.
     */
    if( f->state != OPENED ){
      LCPDEBUG((LOG_INFO, "Protocol-Reject discarded: LCP in state %d",
              f->state));
      return;
    }

    /*
     * Upcall the proper Protocol-Reject routine.
     */
    for (i = 0; (protp = protocols[i]) != NULL; ++i)
      if (protp->protocol == prot && protp->enabled_flag) {
          (*protp->protrej)(f->unit);
          return;
      }

    syslog(LOG_WARNING, "Protocol-Reject for unsupported protocol 0x%x",
         prot);
}


/*
 * lcp_protrej - A Protocol-Reject was received.
 */
/*ARGSUSED*/
static void
lcp_protrej(unit)
    int unit;
{
    /*
     * Can't reject LCP!
     */
    LCPDEBUG((LOG_WARNING,
            "lcp_protrej: Received Protocol-Reject for LCP!"));
    fsm_protreject(&lcp_fsm[unit]);
}


/*
 * lcp_sprotrej - Send a Protocol-Reject for some protocol.
 */
void
lcp_sprotrej(unit, p, len)
    int unit;
    u_char *p;
    int len;
{
    /*
     * Send back the protocol and the information field of the
     * rejected packet.  We only get here if LCP is in the OPENED state.
     */
    p += 2;
    len -= 2;

    fsm_sdata(&lcp_fsm[unit], PROTREJ, ++lcp_fsm[unit].id,
            p, len);
}


/*
 * lcp_resetci - Reset our CI.
 */
static void
lcp_resetci(f)
    fsm *f;
{
    lcp_wantoptions[f->unit].magicnumber = magic();
    lcp_wantoptions[f->unit].numloops = 0;
    lcp_gotoptions[f->unit] = lcp_wantoptions[f->unit];
    peer_mru[f->unit] = PPP_MRU;
    auth_reset(f->unit);
}


/*
 * lcp_cilen - Return length of our CI.
 */
static int
lcp_cilen(f)
    fsm *f;
{
    lcp_options *go = &lcp_gotoptions[f->unit];

#define LENCIVOID(neg)  ((neg) ? CILEN_VOID : 0)
#define LENCICHAP(neg)  ((neg) ? CILEN_CHAP : 0)
#define LENCISHORT(neg) ((neg) ? CILEN_SHORT : 0)
#define LENCILONG(neg)  ((neg) ? CILEN_LONG : 0)
#define LENCILQR(neg)   ((neg) ? CILEN_LQR: 0)
#define LENCICBCP(neg)  ((neg) ? CILEN_CBCP: 0)
    /*
     * NB: we only ask for one of CHAP and UPAP, even if we will
     * accept either.
     */
    return (LENCISHORT(go->neg_mru && go->mru != DEFMRU) +
          LENCILONG(go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF) +
          LENCICHAP(go->neg_chap) +
          LENCISHORT(!go->neg_chap && go->neg_upap) +
          LENCILQR(go->neg_lqr) +
          LENCICBCP(go->neg_cbcp) +
          LENCILONG(go->neg_magicnumber) +
          LENCIVOID(go->neg_pcompression) +
          LENCIVOID(go->neg_accompression));
}


/*
 * lcp_addci - Add our desired CIs to a packet.
 */
static void
lcp_addci(f, ucp, lenp)
    fsm *f;
    u_char *ucp;
    int *lenp;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    u_char *start_ucp = ucp;

#define ADDCIVOID(opt, neg) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_VOID, ucp); \
    }
#define ADDCISHORT(opt, neg, val) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_SHORT, ucp); \
      PUTSHORT(val, ucp); \
    }
#define ADDCICHAP(opt, neg, val, digest) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_CHAP, ucp); \
      PUTSHORT(val, ucp); \
      PUTCHAR(digest, ucp); \
    }
#define ADDCILONG(opt, neg, val) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_LONG, ucp); \
      PUTLONG(val, ucp); \
    }
#define ADDCILQR(opt, neg, val) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_LQR, ucp); \
      PUTSHORT(PPP_LQR, ucp); \
      PUTLONG(val, ucp); \
    }
#define ADDCICHAR(opt, neg, val) \
    if (neg) { \
      PUTCHAR(opt, ucp); \
      PUTCHAR(CILEN_CHAR, ucp); \
      PUTCHAR(val, ucp); \
    }

    ADDCISHORT(CI_MRU, go->neg_mru && go->mru != DEFMRU, go->mru);
    ADDCILONG(CI_ASYNCMAP, go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF,
            go->asyncmap);
    ADDCICHAP(CI_AUTHTYPE, go->neg_chap, PPP_CHAP, go->chap_mdtype);
    ADDCISHORT(CI_AUTHTYPE, !go->neg_chap && go->neg_upap, PPP_PAP);
    ADDCILQR(CI_QUALITY, go->neg_lqr, go->lqr_period);
    ADDCICHAR(CI_CALLBACK, go->neg_cbcp, CBCP_OPT);
    ADDCILONG(CI_MAGICNUMBER, go->neg_magicnumber, go->magicnumber);
    ADDCIVOID(CI_PCOMPRESSION, go->neg_pcompression);
    ADDCIVOID(CI_ACCOMPRESSION, go->neg_accompression);

    if (ucp - start_ucp != *lenp) {
      /* this should never happen, because peer_mtu should be 1500 */
      syslog(LOG_ERR, "Bug in lcp_addci: wrong length");
    }
}


/*
 * lcp_ackci - Ack our CIs.
 * This should not modify any state if the Ack is bad.
 *
 * Returns:
 *    0 - Ack was bad.
 *    1 - Ack was good.
 */
static int
lcp_ackci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    u_char cilen, citype, cichar;
    u_short cishort;
    u_int32_t cilong;

    /*
     * 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 ACKCIVOID(opt, neg) \
    if (neg) { \
      if ((len -= CILEN_VOID) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_VOID || \
          citype != opt) \
          goto bad; \
    }
#define ACKCISHORT(opt, neg, val) \
    if (neg) { \
      if ((len -= CILEN_SHORT) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_SHORT || \
          citype != opt) \
          goto bad; \
      GETSHORT(cishort, p); \
      if (cishort != val) \
          goto bad; \
    }
#define ACKCICHAR(opt, neg, val) \
    if (neg) { \
      if ((len -= CILEN_CHAR) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_CHAR || \
          citype != opt) \
          goto bad; \
      GETCHAR(cichar, p); \
      if (cichar != val) \
          goto bad; \
    }
#define ACKCICHAP(opt, neg, val, digest) \
    if (neg) { \
      if ((len -= CILEN_CHAP) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_CHAP || \
          citype != opt) \
          goto bad; \
      GETSHORT(cishort, p); \
      if (cishort != val) \
          goto bad; \
      GETCHAR(cichar, p); \
      if (cichar != digest) \
        goto bad; \
    }
#define ACKCILONG(opt, neg, val) \
    if (neg) { \
      if ((len -= CILEN_LONG) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_LONG || \
          citype != opt) \
          goto bad; \
      GETLONG(cilong, p); \
      if (cilong != val) \
          goto bad; \
    }
#define ACKCILQR(opt, neg, val) \
    if (neg) { \
      if ((len -= CILEN_LQR) < 0) \
          goto bad; \
      GETCHAR(citype, p); \
      GETCHAR(cilen, p); \
      if (cilen != CILEN_LQR || \
          citype != opt) \
          goto bad; \
      GETSHORT(cishort, p); \
      if (cishort != PPP_LQR) \
          goto bad; \
      GETLONG(cilong, p); \
      if (cilong != val) \
        goto bad; \
    }

    ACKCISHORT(CI_MRU, go->neg_mru && go->mru != DEFMRU, go->mru);
    ACKCILONG(CI_ASYNCMAP, go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF,
            go->asyncmap);
    ACKCICHAP(CI_AUTHTYPE, go->neg_chap, PPP_CHAP, go->chap_mdtype);
    ACKCISHORT(CI_AUTHTYPE, !go->neg_chap && go->neg_upap, PPP_PAP);
    ACKCILQR(CI_QUALITY, go->neg_lqr, go->lqr_period);
    ACKCICHAR(CI_CALLBACK, go->neg_cbcp, CBCP_OPT);
    ACKCILONG(CI_MAGICNUMBER, go->neg_magicnumber, go->magicnumber);
    ACKCIVOID(CI_PCOMPRESSION, go->neg_pcompression);
    ACKCIVOID(CI_ACCOMPRESSION, go->neg_accompression);

    /*
     * If there are any remaining CIs, then this packet is bad.
     */
    if (len != 0)
      goto bad;
    return (1);
bad:
    LCPDEBUG((LOG_WARNING, "lcp_acki: received bad Ack!"));
    return (0);
}


/*
 * lcp_nakci - Peer has sent a NAK for some of our CIs.
 * This should not modify any state if the Nak is bad
 * or if LCP is in the OPENED state.
 *
 * Returns:
 *    0 - Nak was bad.
 *    1 - Nak was good.
 */
static int
lcp_nakci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    lcp_options *wo = &lcp_wantoptions[f->unit];
    u_char citype, cichar, *next;
    u_short cishort;
    u_int32_t cilong;
    lcp_options no;           /* options we've seen Naks for */
    lcp_options try;          /* options to request next time */
    int looped_back = 0;
    int cilen;

    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 NAKCIVOID(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_VOID && \
      p[1] == CILEN_VOID && \
      p[0] == opt) { \
      len -= CILEN_VOID; \
      INCPTR(CILEN_VOID, p); \
      no.neg = 1; \
      code \
    }
#define NAKCICHAP(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_CHAP && \
      p[1] == CILEN_CHAP && \
      p[0] == opt) { \
      len -= CILEN_CHAP; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      GETCHAR(cichar, p); \
      no.neg = 1; \
      code \
    }
#define NAKCICHAR(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_CHAR && \
      p[1] == CILEN_CHAR && \
      p[0] == opt) { \
      len -= CILEN_CHAR; \
      INCPTR(2, p); \
      GETCHAR(cichar, p); \
      no.neg = 1; \
      code \
    }
#define NAKCISHORT(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_SHORT && \
      p[1] == CILEN_SHORT && \
      p[0] == opt) { \
      len -= CILEN_SHORT; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      no.neg = 1; \
      code \
    }
#define NAKCILONG(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_LONG && \
      p[1] == CILEN_LONG && \
      p[0] == opt) { \
      len -= CILEN_LONG; \
      INCPTR(2, p); \
      GETLONG(cilong, p); \
      no.neg = 1; \
      code \
    }
#define NAKCILQR(opt, neg, code) \
    if (go->neg && \
      len >= CILEN_LQR && \
      p[1] == CILEN_LQR && \
      p[0] == opt) { \
      len -= CILEN_LQR; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      GETLONG(cilong, p); \
      no.neg = 1; \
      code \
    }

    /*
     * We don't care if they want to send us smaller packets than
     * we want.  Therefore, accept any MRU less than what we asked for,
     * but then ignore the new value when setting the MRU in the kernel.
     * If they send us a bigger MRU than what we asked, accept it, up to
     * the limit of the default MRU we'd get if we didn't negotiate.
     */
    if (go->neg_mru && go->mru != DEFMRU) {
      NAKCISHORT(CI_MRU, neg_mru,
               if (cishort <= wo->mru || cishort <= DEFMRU)
                   try.mru = cishort;
               );
    }

    /*
     * Add any characters they want to our (receive-side) asyncmap.
     */
    if (go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF) {
      NAKCILONG(CI_ASYNCMAP, neg_asyncmap,
              try.asyncmap = go->asyncmap | cilong;
              );
    }

    /*
     * If they've nak'd our authentication-protocol, check whether
     * they are proposing a different protocol, or a different
     * hash algorithm for CHAP.
     */
    if ((go->neg_chap || go->neg_upap)
      && len >= CILEN_SHORT
      && p[0] == CI_AUTHTYPE && p[1] >= CILEN_SHORT && p[1] <= len) {
      cilen = p[1];
      len -= cilen;
      no.neg_chap = go->neg_chap;
      no.neg_upap = go->neg_upap;
      INCPTR(2, p);
        GETSHORT(cishort, p);
      if (cishort == PPP_PAP && cilen == CILEN_SHORT) {
          /*
           * If we were asking for CHAP, they obviously don't want to do it.
           * If we weren't asking for CHAP, then we were asking for PAP,
           * in which case this Nak is bad.
           */
          if (!go->neg_chap)
            goto bad;
          try.neg_chap = 0;

      } else if (cishort == PPP_CHAP && cilen == CILEN_CHAP) {
          GETCHAR(cichar, p);
          if (go->neg_chap) {
            /*
             * We were asking for CHAP/MD5; they must want a different
             * algorithm.  If they can't do MD5, we'll have to stop
             * asking for CHAP.
             */
            if (cichar != go->chap_mdtype)
                try.neg_chap = 0;
          } else {
            /*
             * Stop asking for PAP if we were asking for it.
             */
            try.neg_upap = 0;
          }

      } else {
          /*
           * We don't recognize what they're suggesting.
           * Stop asking for what we were asking for.
           */
          if (go->neg_chap)
            try.neg_chap = 0;
          else
            try.neg_upap = 0;
          p += cilen - CILEN_SHORT;
      }
    }

    /*
     * If they can't cope with our link quality protocol, we'll have
     * to stop asking for LQR.  We haven't got any other protocol.
     * If they Nak the reporting period, take their value XXX ?
     */
    NAKCILQR(CI_QUALITY, neg_lqr,
           if (cishort != PPP_LQR)
             try.neg_lqr = 0;
           else
             try.lqr_period = cilong;
           );

    /*
     * Only implementing CBCP...not the rest of the callback options
     */
    NAKCICHAR(CI_CALLBACK, neg_cbcp,
              try.neg_cbcp = 0;
              );

    /*
     * Check for a looped-back line.
     */
    NAKCILONG(CI_MAGICNUMBER, neg_magicnumber,
            try.magicnumber = magic();
            looped_back = 1;
            );

    /*
     * Peer shouldn't send Nak for protocol compression or
     * address/control compression requests; they should send
     * a Reject instead.  If they send a Nak, treat it as a Reject.
     */
    NAKCIVOID(CI_PCOMPRESSION, neg_pcompression,
            try.neg_pcompression = 0;
            );
    NAKCIVOID(CI_ACCOMPRESSION, neg_accompression,
            try.neg_accompression = 0;
            );

    /*
     * There may be remaining CIs, if the peer is requesting negotiation
     * on an option that we didn't include in our request packet.
     * If we see an option that we requested, or one we've already seen
     * in this packet, then this packet is bad.
     * If we wanted to respond by starting to negotiate on the requested
     * option(s), we could, but we don't, because except for the
     * authentication type and quality protocol, if we are not negotiating
     * an option, it is because we were told not to.
     * For the authentication type, the Nak from the peer means
     * `let me authenticate myself with you' which is a bit pointless.
     * For the quality protocol, the Nak means `ask me to send you quality
     * reports', but if we didn't ask for them, we don't want them.
     * An option we don't recognize represents the peer asking to
     * negotiate some option we don't support, so ignore it.
     */
    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_MRU:
          if ((go->neg_mru && go->mru != DEFMRU)
            || no.neg_mru || cilen != CILEN_SHORT)
            goto bad;
          GETSHORT(cishort, p);
          if (cishort < DEFMRU)
            try.mru = cishort;
          break;
      case CI_ASYNCMAP:
          if ((go->neg_asyncmap && go->asyncmap != 0xFFFFFFFF)
            || no.neg_asyncmap || cilen != CILEN_LONG)
            goto bad;
          break;
      case CI_AUTHTYPE:
          if (go->neg_chap || no.neg_chap || go->neg_upap || no.neg_upap)
            goto bad;
          break;
      case CI_MAGICNUMBER:
          if (go->neg_magicnumber || no.neg_magicnumber ||
            cilen != CILEN_LONG)
            goto bad;
          break;
      case CI_PCOMPRESSION:
          if (go->neg_pcompression || no.neg_pcompression
            || cilen != CILEN_VOID)
            goto bad;
          break;
      case CI_ACCOMPRESSION:
          if (go->neg_accompression || no.neg_accompression
            || cilen != CILEN_VOID)
            goto bad;
          break;
      case CI_QUALITY:
          if (go->neg_lqr || no.neg_lqr || cilen != CILEN_LQR)
            goto bad;
          break;
      }
      p = next;
    }

    /* If there is still anything left, this packet is bad. */
    if (len != 0)
      goto bad;

    /*
     * OK, the Nak is good.  Now we can update state.
     */
    if (f->state != OPENED) {
      if (looped_back) {
          if (++try.numloops >= lcp_loopbackfail) {
            syslog(LOG_NOTICE, "Serial line is looped back.");
            lcp_close(f->unit, "Loopback detected");
          }
      } else
          try.numloops = 0;
      *go = try;
    }

    return 1;

bad:
    LCPDEBUG((LOG_WARNING, "lcp_nakci: received bad Nak!"));
    return 0;
}


/*
 * lcp_rejci - Peer has Rejected some of our CIs.
 * This should not modify any state if the Reject is bad
 * or if LCP is in the OPENED state.
 *
 * Returns:
 *    0 - Reject was bad.
 *    1 - Reject was good.
 */
static int
lcp_rejci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    u_char cichar;
    u_short cishort;
    u_int32_t cilong;
    lcp_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 REJCIVOID(opt, neg) \
    if (go->neg && \
      len >= CILEN_VOID && \
      p[1] == CILEN_VOID && \
      p[0] == opt) { \
      len -= CILEN_VOID; \
      INCPTR(CILEN_VOID, p); \
      try.neg = 0; \
      LCPDEBUG((LOG_INFO, "lcp_rejci rejected void opt %d", opt)); \
    }
#define REJCISHORT(opt, neg, val) \
    if (go->neg && \
      len >= CILEN_SHORT && \
      p[1] == CILEN_SHORT && \
      p[0] == opt) { \
      len -= CILEN_SHORT; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      /* Check rejected value. */ \
      if (cishort != val) \
          goto bad; \
      try.neg = 0; \
      LCPDEBUG((LOG_INFO,"lcp_rejci rejected short opt %d", opt)); \
    }
#define REJCICHAP(opt, neg, val, digest) \
    if (go->neg && \
      len >= CILEN_CHAP && \
      p[1] == CILEN_CHAP && \
      p[0] == opt) { \
      len -= CILEN_CHAP; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      GETCHAR(cichar, p); \
      /* Check rejected value. */ \
      if (cishort != val || cichar != digest) \
          goto bad; \
      try.neg = 0; \
      try.neg_upap = 0; \
      LCPDEBUG((LOG_INFO,"lcp_rejci rejected chap opt %d", opt)); \
    }
#define REJCILONG(opt, neg, val) \
    if (go->neg && \
      len >= CILEN_LONG && \
      p[1] == CILEN_LONG && \
      p[0] == opt) { \
      len -= CILEN_LONG; \
      INCPTR(2, p); \
      GETLONG(cilong, p); \
      /* Check rejected value. */ \
      if (cilong != val) \
          goto bad; \
      try.neg = 0; \
      LCPDEBUG((LOG_INFO,"lcp_rejci rejected long opt %d", opt)); \
    }
#define REJCILQR(opt, neg, val) \
    if (go->neg && \
      len >= CILEN_LQR && \
      p[1] == CILEN_LQR && \
      p[0] == opt) { \
      len -= CILEN_LQR; \
      INCPTR(2, p); \
      GETSHORT(cishort, p); \
      GETLONG(cilong, p); \
      /* Check rejected value. */ \
      if (cishort != PPP_LQR || cilong != val) \
          goto bad; \
      try.neg = 0; \
      LCPDEBUG((LOG_INFO,"lcp_rejci rejected LQR opt %d", opt)); \
    }
#define REJCICBCP(opt, neg, val) \
    if (go->neg && \
      len >= CILEN_CBCP && \
      p[1] == CILEN_CBCP && \
      p[0] == opt) { \
      len -= CILEN_CBCP; \
      INCPTR(2, p); \
      GETCHAR(cichar, p); \
      /* Check rejected value. */ \
      if (cichar != val) \
          goto bad; \
      try.neg = 0; \
      LCPDEBUG((LOG_INFO,"lcp_rejci rejected Callback opt %d", opt)); \
    }

    REJCISHORT(CI_MRU, neg_mru, go->mru);
    REJCILONG(CI_ASYNCMAP, neg_asyncmap, go->asyncmap);
    REJCICHAP(CI_AUTHTYPE, neg_chap, PPP_CHAP, go->chap_mdtype);
    if (!go->neg_chap) {
      REJCISHORT(CI_AUTHTYPE, neg_upap, PPP_PAP);
    }
    REJCILQR(CI_QUALITY, neg_lqr, go->lqr_period);
    REJCICBCP(CI_CALLBACK, neg_cbcp, CBCP_OPT);
    REJCILONG(CI_MAGICNUMBER, neg_magicnumber, go->magicnumber);
    REJCIVOID(CI_PCOMPRESSION, neg_pcompression);
    REJCIVOID(CI_ACCOMPRESSION, neg_accompression);

    /*
     * 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:
    LCPDEBUG((LOG_WARNING, "lcp_rejci: received bad Reject!"));
    return 0;
}


/*
 * lcp_reqci - Check the peer's requested CIs and send appropriate response.
 *
 * 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
lcp_reqci(f, inp, lenp, reject_if_disagree)
    fsm *f;
    u_char *inp;        /* Requested CIs */
    int *lenp;                /* Length of requested CIs */
    int reject_if_disagree;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    lcp_options *ho = &lcp_hisoptions[f->unit];
    lcp_options *ao = &lcp_allowoptions[f->unit];
    u_char *cip, *next;       /* Pointer to current and next CIs */
    int cilen, citype, cichar;      /* Parsed len, type, char value */
    u_short cishort;          /* Parsed short value */
    u_int32_t cilong;         /* Parse long value */
    int rc = CONFACK;         /* Final packet return code */
    int orc;                  /* Individual option return code */
    u_char *p;                /* Pointer to next char to parse */
    u_char *rejp;       /* Pointer to next char in reject frame */
    u_char *nakp;       /* Pointer to next char in Nak frame */
    int l = *lenp;            /* Length left */

    /*
     * Reset all his options.
     */
    BZERO(ho, sizeof(*ho));

    /*
     * Process all his options.
     */
    next = inp;
    nakp = nak_buffer;
    rejp = 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? */
          LCPDEBUG((LOG_WARNING, "lcp_reqci: bad CI length!"));
          orc = CONFREJ;            /* Reject bad CI */
          cilen = l;                /* Reject till end of packet */
          l = 0;              /* Don't loop again */
          citype = 0;
          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_MRU:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd MRU"));
          if (!ao->neg_mru ||       /* Allow option? */
            cilen != CILEN_SHORT) { /* Check CI length */
            orc = CONFREJ;          /* Reject CI */
            break;
          }
          GETSHORT(cishort, p);     /* Parse MRU */
          LCPDEBUG((LOG_INFO, "(%d)", cishort));

          /*
           * He must be able to receive at least our minimum.
           * No need to check a maximum.  If he sends a large number,
           * we'll just ignore it.
           */
          if (cishort < MINMRU) {
            orc = CONFNAK;          /* Nak CI */
            PUTCHAR(CI_MRU, nakp);
            PUTCHAR(CILEN_SHORT, nakp);
            PUTSHORT(MINMRU, nakp); /* Give him a hint */
            break;
          }
          ho->neg_mru = 1;          /* Remember he sent MRU */
          ho->mru = cishort;        /* And remember value */
          break;

      case CI_ASYNCMAP:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd ASYNCMAP"));
          if (!ao->neg_asyncmap ||
            cilen != CILEN_LONG) {
            orc = CONFREJ;
            break;
          }
          GETLONG(cilong, p);
          LCPDEBUG((LOG_INFO, "(%x)", (unsigned int) cilong));

          /*
           * Asyncmap must have set at least the bits
           * which are set in lcp_allowoptions[unit].asyncmap.
           */
          if ((ao->asyncmap & ~cilong) != 0) {
            orc = CONFNAK;
            PUTCHAR(CI_ASYNCMAP, nakp);
            PUTCHAR(CILEN_LONG, nakp);
            PUTLONG(ao->asyncmap | cilong, nakp);
            break;
          }
          ho->neg_asyncmap = 1;
          ho->asyncmap = cilong;
          break;

      case CI_AUTHTYPE:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd AUTHTYPE"));
          if (cilen < CILEN_SHORT ||
            !(ao->neg_upap || ao->neg_chap)) {
            /*
             * Reject the option if we're not willing to authenticate.
             */
            orc = CONFREJ;
            break;
          }
          GETSHORT(cishort, p);
          LCPDEBUG((LOG_INFO, "(%x)", cishort));

          /*
           * Authtype must be UPAP or CHAP.
           *
           * Note: if both ao->neg_upap and ao->neg_chap are set,
           * and the peer sends a Configure-Request with two
           * authenticate-protocol requests, one for CHAP and one
           * for UPAP, then we will reject the second request.
           * Whether we end up doing CHAP or UPAP depends then on
           * the ordering of the CIs in the peer's Configure-Request.
           */

          if (cishort == PPP_PAP) {
            if (ho->neg_chap ||     /* we've already accepted CHAP */
                cilen != CILEN_SHORT) {
                LCPDEBUG((LOG_WARNING,
                        "lcp_reqci: rcvd AUTHTYPE PAP, rejecting..."));
                orc = CONFREJ;
                break;
            }
            if (!ao->neg_upap) {    /* we don't want to do PAP */
                orc = CONFNAK;      /* NAK it and suggest CHAP */
                PUTCHAR(CI_AUTHTYPE, nakp);
                PUTCHAR(CILEN_CHAP, nakp);
                PUTSHORT(PPP_CHAP, nakp);
                PUTCHAR(ao->chap_mdtype, nakp);
                break;
            }
            ho->neg_upap = 1;
            break;
          }
          if (cishort == PPP_CHAP) {
            if (ho->neg_upap ||     /* we've already accepted PAP */
                cilen != CILEN_CHAP) {
                LCPDEBUG((LOG_INFO,
                        "lcp_reqci: rcvd AUTHTYPE CHAP, rejecting..."));
                orc = CONFREJ;
                break;
            }
            if (!ao->neg_chap) {    /* we don't want to do CHAP */
                orc = CONFNAK;      /* NAK it and suggest PAP */
                PUTCHAR(CI_AUTHTYPE, nakp);
                PUTCHAR(CILEN_SHORT, nakp);
                PUTSHORT(PPP_PAP, nakp);
                break;
            }
            GETCHAR(cichar, p);     /* get digest type*/
            if (cichar != CHAP_DIGEST_MD5
#ifdef CHAPMS
                && cichar != CHAP_MICROSOFT
#endif
                ) {
                orc = CONFNAK;
                PUTCHAR(CI_AUTHTYPE, nakp);
                PUTCHAR(CILEN_CHAP, nakp);
                PUTSHORT(PPP_CHAP, nakp);
                PUTCHAR(ao->chap_mdtype, nakp);
                break;
            }
            ho->chap_mdtype = cichar; /* save md type */
            ho->neg_chap = 1;
            break;
          }

          /*
           * We don't recognize the protocol they're asking for.
           * Nak it with something we're willing to do.
           * (At this point we know ao->neg_upap || ao->neg_chap.)
           */
          orc = CONFNAK;
          PUTCHAR(CI_AUTHTYPE, nakp);
          if (ao->neg_chap) {
            PUTCHAR(CILEN_CHAP, nakp);
            PUTSHORT(PPP_CHAP, nakp);
            PUTCHAR(ao->chap_mdtype, nakp);
          } else {
            PUTCHAR(CILEN_SHORT, nakp);
            PUTSHORT(PPP_PAP, nakp);
          }
          break;

      case CI_QUALITY:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd QUALITY"));
          if (!ao->neg_lqr ||
            cilen != CILEN_LQR) {
            orc = CONFREJ;
            break;
          }

          GETSHORT(cishort, p);
          GETLONG(cilong, p);
          LCPDEBUG((LOG_INFO, "(%x %x)", cishort, (unsigned int) cilong));

          /*
           * Check the protocol and the reporting period.
           * XXX When should we Nak this, and what with?
           */
          if (cishort != PPP_LQR) {
            orc = CONFNAK;
            PUTCHAR(CI_QUALITY, nakp);
            PUTCHAR(CILEN_LQR, nakp);
            PUTSHORT(PPP_LQR, nakp);
            PUTLONG(ao->lqr_period, nakp);
            break;
          }
          break;

      case CI_MAGICNUMBER:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd MAGICNUMBER"));
          if (!(ao->neg_magicnumber || go->neg_magicnumber) ||
            cilen != CILEN_LONG) {
            orc = CONFREJ;
            break;
          }
          GETLONG(cilong, p);
          LCPDEBUG((LOG_INFO, "(%x)", (unsigned int) cilong));

          /*
           * He must have a different magic number.
           */
          if (go->neg_magicnumber &&
            cilong == go->magicnumber) {
            cilong = magic(); /* Don't put magic() inside macro! */
            orc = CONFNAK;
            PUTCHAR(CI_MAGICNUMBER, nakp);
            PUTCHAR(CILEN_LONG, nakp);
            PUTLONG(cilong, nakp);
            break;
          }
          ho->neg_magicnumber = 1;
          ho->magicnumber = cilong;
          break;


      case CI_PCOMPRESSION:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd PCOMPRESSION"));
          if (!ao->neg_pcompression ||
            cilen != CILEN_VOID) {
            orc = CONFREJ;
            break;
          }
          ho->neg_pcompression = 1;
          break;

      case CI_ACCOMPRESSION:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd ACCOMPRESSION"));
          if (!ao->neg_accompression ||
            cilen != CILEN_VOID) {
            orc = CONFREJ;
            break;
          }
          ho->neg_accompression = 1;
          break;

      default:
          LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd unknown option %d",
                  citype));
          orc = CONFREJ;
          break;
      }

endswitch:
      LCPDEBUG((LOG_INFO, " (%s)", CODENAME(orc)));
      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? */
            && citype != CI_MAGICNUMBER) {
            orc = CONFREJ;          /* Get tough if so */
          } else {
            if (rc == CONFREJ)      /* Rejecting prior CI? */
                continue;           /* Don't send this one */
            rc = CONFNAK;
          }
      }
      if (orc == CONFREJ) {         /* Reject this CI */
          rc = CONFREJ;
          if (cip != rejp)          /* Need to move rejected CI? */
            BCOPY(cip, rejp, cilen); /* Move it */
          INCPTR(cilen, rejp);      /* Update output pointer */
      }
    }

    /*
     * If we wanted to send additional NAKs (for unsent CIs), the
     * code would go here.  The extra NAKs would go at *nakp.
     * At present there are no cases where we want to ask the
     * peer to negotiate an option.
     */

    switch (rc) {
    case CONFACK:
      *lenp = next - inp;
      break;
    case CONFNAK:
      /*
       * Copy the Nak'd options from the nak_buffer to the caller's buffer.
       */
      *lenp = nakp - nak_buffer;
      BCOPY(nak_buffer, inp, *lenp);
      break;
    case CONFREJ:
      *lenp = rejp - inp;
      break;
    }

    LCPDEBUG((LOG_INFO, "lcp_reqci: returning CONF%s.", CODENAME(rc)));
    return (rc);              /* Return final code */
}


/*
 * lcp_up - LCP has come UP.
 */
static void
lcp_up(f)
    fsm *f;
{
    lcp_options *wo = &lcp_wantoptions[f->unit];
    lcp_options *ho = &lcp_hisoptions[f->unit];
    lcp_options *go = &lcp_gotoptions[f->unit];
    lcp_options *ao = &lcp_allowoptions[f->unit];

    if (!go->neg_magicnumber)
      go->magicnumber = 0;
    if (!ho->neg_magicnumber)
      ho->magicnumber = 0;

    /*
     * Set our MTU to the smaller of the MTU we wanted and
     * the MRU our peer wanted.  If we negotiated an MRU,
     * set our MRU to the larger of value we wanted and
     * the value we got in the negotiation.
     */
    ppp_send_config(f->unit, MIN(ao->mru, (ho->neg_mru? ho->mru: PPP_MRU)),
                (ho->neg_asyncmap? ho->asyncmap: 0xffffffff),
                ho->neg_pcompression, ho->neg_accompression);
    ppp_recv_config(f->unit, (go->neg_mru? MAX(wo->mru, go->mru): PPP_MRU),
                (go->neg_asyncmap? go->asyncmap: 0xffffffff),
                go->neg_pcompression, go->neg_accompression);

    if (ho->neg_mru)
      peer_mru[f->unit] = ho->mru;

    lcp_echo_lowerup(f->unit);  /* Enable echo messages */

    link_established(f->unit);
}


/*
 * lcp_down - LCP has gone DOWN.
 *
 * Alert other protocols.
 */
static void
lcp_down(f)
    fsm *f;
{
    lcp_options *go = &lcp_gotoptions[f->unit];

    lcp_echo_lowerdown(f->unit);

    link_down(f->unit);

    ppp_send_config(f->unit, PPP_MRU, 0xffffffff, 0, 0);
    ppp_recv_config(f->unit, PPP_MRU,
                (go->neg_asyncmap? go->asyncmap: 0xffffffff),
                go->neg_pcompression, go->neg_accompression);
    peer_mru[f->unit] = PPP_MRU;
}


/*
 * lcp_starting - LCP needs the lower layer up.
 */
static void
lcp_starting(f)
    fsm *f;
{
    link_required(f->unit);
}


/*
 * lcp_finished - LCP has finished with the lower layer.
 */
static void
lcp_finished(f)
    fsm *f;
{
    link_terminated(f->unit);
}


/*
 * lcp_printpkt - print the contents of an LCP packet.
 */
static char *lcp_codenames[] = {
    "ConfReq", "ConfAck", "ConfNak", "ConfRej",
    "TermReq", "TermAck", "CodeRej", "ProtRej",
    "EchoReq", "EchoRep", "DiscReq"
};

static int
lcp_printpkt(p, plen, printer, arg)
    u_char *p;
    int plen;
    void (*printer) __P((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(lcp_codenames) / sizeof(char *))
      printer(arg, " %s", lcp_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_MRU:
            if (olen == CILEN_SHORT) {
                p += 2;
                GETSHORT(cishort, p);
                printer(arg, "mru %d", cishort);
            }
            break;
          case CI_ASYNCMAP:
            if (olen == CILEN_LONG) {
                p += 2;
                GETLONG(cilong, p);
                printer(arg, "asyncmap 0x%x", cilong);
            }
            break;
          case CI_AUTHTYPE:
            if (olen >= CILEN_SHORT) {
                p += 2;
                printer(arg, "auth ");
                GETSHORT(cishort, p);
                switch (cishort) {
                case PPP_PAP:
                  printer(arg, "pap");
                  break;
                case PPP_CHAP:
                  printer(arg, "chap");
                  break;
                default:
                  printer(arg, "0x%x", cishort);
                }
            }
            break;
          case CI_QUALITY:
            if (olen >= CILEN_SHORT) {
                p += 2;
                printer(arg, "quality ");
                GETSHORT(cishort, p);
                switch (cishort) {
                case PPP_LQR:
                  printer(arg, "lqr");
                  break;
                default:
                  printer(arg, "0x%x", cishort);
                }
            }
            break;
          case CI_CALLBACK:
            if (olen >= CILEN_CHAR) {
                p += 2;
                printer(arg, "callback ");
                GETSHORT(cishort, p);
                switch (cishort) {
                case CBCP_OPT:
                  printer(arg, "CBCP");
                  break;
                default:
                  printer(arg, "0x%x", cishort);
                }
            }
            break;
          case CI_MAGICNUMBER:
            if (olen == CILEN_LONG) {
                p += 2;
                GETLONG(cilong, p);
                printer(arg, "magic 0x%x", cilong);
            }
            break;
          case CI_PCOMPRESSION:
            if (olen == CILEN_VOID) {
                p += 2;
                printer(arg, "pcomp");
            }
            break;
          case CI_ACCOMPRESSION:
            if (olen == CILEN_VOID) {
                p += 2;
                printer(arg, "accomp");
            }
            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(p, len, printer, arg);
          p += len;
          len = 0;
      }
      break;

    case ECHOREQ:
    case ECHOREP:
    case DISCREQ:
      if (len >= 4) {
          GETLONG(cilong, p);
          printer(arg, " magic=0x%x", cilong);
          p += 4;
          len -= 4;
      }
      break;
    }

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

    return p - pstart;
}

/*
 * Time to shut down the link because there is nothing out there.
 */

static
void LcpLinkFailure (f)
    fsm *f;
{
    if (f->state == OPENED) {
      syslog(LOG_INFO, "No response to %d echo-requests", lcp_echos_pending);
        syslog(LOG_NOTICE, "Serial link appears to be disconnected.");
        lcp_close(f->unit, "Peer not responding");
    }
}

/*
 * Timer expired for the LCP echo requests from this process.
 */

static void
LcpEchoCheck (f)
    fsm *f;
{
    LcpSendEchoRequest (f);
    if (f->state != OPENED)
          return;

    /*
     * Start the timer for the next interval.
     */
    assert (lcp_echo_timer_running==0);
    TIMEOUT (LcpEchoTimeout, f, lcp_echo_interval);
    lcp_echo_timer_running = 1;
}

/*
 * LcpEchoTimeout - Timer expired on the LCP echo
 */

static void
LcpEchoTimeout (arg)
    void *arg;
{
    if (lcp_echo_timer_running != 0) {
        lcp_echo_timer_running = 0;
        LcpEchoCheck ((fsm *) arg);
    }
}

/*
 * LcpEchoReply - LCP has received a reply to the echo
 */

static void
lcp_received_echo_reply (f, id, inp, len)
    fsm *f;
    int id; u_char *inp; int len;
{
    u_int32_t magic;

    /* Check the magic number - don't count replies from ourselves. */
    if (len < 4) {
      syslog(LOG_DEBUG, "lcp: received short Echo-Reply, length %d", len);
      return;
    }
    GETLONG(magic, inp);
    if (lcp_gotoptions[f->unit].neg_magicnumber
      && magic == lcp_gotoptions[f->unit].magicnumber) {
      syslog(LOG_WARNING, "appear to have received our own echo-reply!");
      return;
    }

    /* Reset the number of outstanding echo frames */
    lcp_echos_pending = 0;
}

/*
 * LcpSendEchoRequest - Send an echo request frame to the peer
 */

static void
LcpSendEchoRequest (f)
    fsm *f;
{
    u_int32_t lcp_magic;
    u_char pkt[4], *pktp;

    /*
     * Detect the failure of the peer at this point.
     */
    if (lcp_echo_fails != 0) {
        if (lcp_echos_pending >= lcp_echo_fails) {
            LcpLinkFailure(f);
          lcp_echos_pending = 0;
      }
    }

    /*
     * Make and send the echo request frame.
     */
    if (f->state == OPENED) {
        lcp_magic = lcp_gotoptions[f->unit].magicnumber;
      pktp = pkt;
      PUTLONG(lcp_magic, pktp);
        fsm_sdata(f, ECHOREQ, lcp_echo_number++ & 0xFF, pkt, pktp - pkt);
      ++lcp_echos_pending;
    }
}

/*
 * lcp_echo_lowerup - Start the timer for the LCP frame
 */

static void
lcp_echo_lowerup (unit)
    int unit;
{
    fsm *f = &lcp_fsm[unit];

    /* Clear the parameters for generating echo frames */
    lcp_echos_pending      = 0;
    lcp_echo_number        = 0;
    lcp_echo_timer_running = 0;
  
    /* If a timeout interval is specified then start the timer */
    if (lcp_echo_interval != 0)
        LcpEchoCheck (f);
}

/*
 * lcp_echo_lowerdown - Stop the timer for the LCP frame
 */

static void
lcp_echo_lowerdown (unit)
    int unit;
{
    fsm *f = &lcp_fsm[unit];

    if (lcp_echo_timer_running != 0) {
        UNTIMEOUT (LcpEchoTimeout, f);
        lcp_echo_timer_running = 0;
    }
}

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