fsm.c

/*****************************************************************************
* fsm.c - Network Control Protocol Finite State Machine program file.
*
* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
* portions Copyright (c) 1997 by Global Election Systems Inc.
*
* The authors hereby grant permission to use, copy, modify, distribute,
* and license this software and its documentation for any purpose, provided
* that existing copyright notices are retained in all copies and that this
* notice and the following disclaimer are included verbatim in any 
* distributions. No written agreement, license, or royalty fee is required
* for any of the authorized uses.
*
* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
******************************************************************************
* REVISION HISTORY
*
* 03-01-01 Marc Boucher <marc@mbsi.ca>
*   Ported to lwIP.
* 97-12-01 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
*   Original based on BSD fsm.c.
*****************************************************************************/
/*
 * fsm.c - {Link, IP} Control Protocol Finite State Machine.
 *
 * 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.
 */

/*
 * TODO:
 * Randomize fsm id on link/init.
 * Deal with variable outgoing MTU.
 */

#include "lwip/opt.h"

#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */

#include "ppp.h"
#include "pppdebug.h"

#include "fsm.h"

#include <string.h>


/*************************/
/*** LOCAL DEFINITIONS ***/
/*************************/

#if PPP_DEBUG

static const char *ppperr_strerr[] = {
           "LS_INITIAL",  /* LS_INITIAL  0 */
           "LS_STARTING", /* LS_STARTING 1 */
           "LS_CLOSED",   /* LS_CLOSED   2 */
           "LS_STOPPED",  /* LS_STOPPED  3 */
           "LS_CLOSING",  /* LS_CLOSING  4 */
           "LS_STOPPING", /* LS_STOPPING 5 */
           "LS_REQSENT",  /* LS_REQSENT  6 */
           "LS_ACKRCVD",  /* LS_ACKRCVD  7 */
           "LS_ACKSENT",  /* LS_ACKSENT  8 */
           "LS_OPENED"    /* LS_OPENED   9 */
};

#endif /* PPP_DEBUG */

/************************/
/*** LOCAL DATA TYPES ***/
/************************/


/***********************************/
/*** LOCAL FUNCTION DECLARATIONS ***/
/***********************************/
static void fsm_timeout (void *);
static void fsm_rconfreq (fsm *, u_char, u_char *, int);
static void fsm_rconfack (fsm *, int, u_char *, int);
static void fsm_rconfnakrej (fsm *, int, int, u_char *, int);
static void fsm_rtermreq (fsm *, int, u_char *, int);
static void fsm_rtermack (fsm *);
static void fsm_rcoderej (fsm *, u_char *, int);
static void fsm_sconfreq (fsm *, int);

#define PROTO_NAME(f) ((f)->callbacks->proto_name)


/******************************/
/*** PUBLIC DATA STRUCTURES ***/
/******************************/


/*****************************/
/*** LOCAL DATA STRUCTURES ***/
/*****************************/
int peer_mru[NUM_PPP];


/***********************************/
/*** PUBLIC FUNCTION DEFINITIONS ***/
/***********************************/

/*
 * fsm_init - Initialize fsm.
 *
 * Initialize fsm state.
 */
void
fsm_init(fsm *f)
{
  f->state = LS_INITIAL;
  f->flags = 0;
  f->id = 0;        /* XXX Start with random id? */
  f->timeouttime = FSM_DEFTIMEOUT;
  f->maxconfreqtransmits = FSM_DEFMAXCONFREQS;
  f->maxtermtransmits = FSM_DEFMAXTERMREQS;
  f->maxnakloops = FSM_DEFMAXNAKLOOPS;
  f->term_reason_len = 0;
}


/*
 * fsm_lowerup - The lower layer is up.
 */
void
fsm_lowerup(fsm *f)
{
  int oldState = f->state;

  LWIP_UNUSED_ARG(oldState);

  switch( f->state ) {
    case LS_INITIAL:
      f->state = LS_CLOSED;
      break;

    case LS_STARTING:
      if( f->flags & OPT_SILENT ) {
        f->state = LS_STOPPED;
      } else {
        /* Send an initial configure-request */
        fsm_sconfreq(f, 0);
        f->state = LS_REQSENT;
      }
    break;

    default:
      FSMDEBUG((LOG_INFO, "%s: Up event in state %d (%s)!\n",
          PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
  }
  
  FSMDEBUG((LOG_INFO, "%s: lowerup state %d (%s) -> %d (%s)\n",
      PROTO_NAME(f), oldState, ppperr_strerr[oldState], f->state, ppperr_strerr[f->state]));
}


/*
 * fsm_lowerdown - The lower layer is down.
 *
 * Cancel all timeouts and inform upper layers.
 */
void
fsm_lowerdown(fsm *f)
{
  int oldState = f->state;

  LWIP_UNUSED_ARG(oldState);

  switch( f->state ) {
    case LS_CLOSED:
      f->state = LS_INITIAL;
      break;

    case LS_STOPPED:
      f->state = LS_STARTING;
      if( f->callbacks->starting ) {
        (*f->callbacks->starting)(f);
      }
      break;

    case LS_CLOSING:
      f->state = LS_INITIAL;
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      break;

    case LS_STOPPING:
    case LS_REQSENT:
    case LS_ACKRCVD:
    case LS_ACKSENT:
      f->state = LS_STARTING;
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      break;

    case LS_OPENED:
      if( f->callbacks->down ) {
        (*f->callbacks->down)(f);
      }
      f->state = LS_STARTING;
      break;

    default:
      FSMDEBUG((LOG_INFO, "%s: Down event in state %d (%s)!\n",
          PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
  }

  FSMDEBUG((LOG_INFO, "%s: lowerdown state %d (%s) -> %d (%s)\n",
      PROTO_NAME(f), oldState, ppperr_strerr[oldState], f->state, ppperr_strerr[f->state]));
}


/*
 * fsm_open - Link is allowed to come up.
 */
void
fsm_open(fsm *f)
{
  int oldState = f->state;

  LWIP_UNUSED_ARG(oldState);

  switch( f->state ) {
    case LS_INITIAL:
      f->state = LS_STARTING;
      if( f->callbacks->starting ) {
        (*f->callbacks->starting)(f);
      }
      break;

    case LS_CLOSED:
      if( f->flags & OPT_SILENT ) {
        f->state = LS_STOPPED;
      } else {
        /* Send an initial configure-request */
        fsm_sconfreq(f, 0);
        f->state = LS_REQSENT;
      }
      break;
  
    case LS_CLOSING:
      f->state = LS_STOPPING;
      /* fall through */
    case LS_STOPPED:
    case LS_OPENED:
      if( f->flags & OPT_RESTART ) {
        fsm_lowerdown(f);
        fsm_lowerup(f);
      }
      break;
  }

  FSMDEBUG((LOG_INFO, "%s: open state %d (%s) -> %d (%s)\n",
      PROTO_NAME(f), oldState, ppperr_strerr[oldState], f->state, ppperr_strerr[f->state]));
}


/*
 * fsm_close - Start closing connection.
 *
 * Cancel timeouts and either initiate close or possibly go directly to
 * the LS_CLOSED state.
 */
void
fsm_close(fsm *f, char *reason)
{
  int oldState = f->state;

  LWIP_UNUSED_ARG(oldState);

  f->term_reason = reason;
  f->term_reason_len = (reason == NULL? 0: strlen(reason));
  switch( f->state ) {
    case LS_STARTING:
      f->state = LS_INITIAL;
      break;
    case LS_STOPPED:
      f->state = LS_CLOSED;
      break;
    case LS_STOPPING:
      f->state = LS_CLOSING;
      break;

    case LS_REQSENT:
    case LS_ACKRCVD:
    case LS_ACKSENT:
    case LS_OPENED:
      if( f->state != LS_OPENED ) {
        UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      } else if( f->callbacks->down ) {
        (*f->callbacks->down)(f);  /* Inform upper layers we're down */
      }
      /* Init restart counter, send Terminate-Request */
      f->retransmits = f->maxtermtransmits;
      fsm_sdata(f, TERMREQ, f->reqid = ++f->id,
            (u_char *) f->term_reason, f->term_reason_len);
      TIMEOUT(fsm_timeout, f, f->timeouttime);
      --f->retransmits;

      f->state = LS_CLOSING;
      break;
  }

  FSMDEBUG((LOG_INFO, "%s: close reason=%s state %d (%s) -> %d (%s)\n",
      PROTO_NAME(f), reason, oldState, ppperr_strerr[oldState], f->state, ppperr_strerr[f->state]));
}


/*
 * fsm_sdata - Send some data.
 *
 * Used for all packets sent to our peer by this module.
 */
void
fsm_sdata( fsm *f, u_char code, u_char id, u_char *data, int datalen)
{
  u_char *outp;
  int outlen;

  /* Adjust length to be smaller than MTU */
  outp = outpacket_buf[f->unit];
  if (datalen > peer_mru[f->unit] - (int)HEADERLEN) {
    datalen = peer_mru[f->unit] - HEADERLEN;
  }
  if (datalen && data != outp + PPP_HDRLEN + HEADERLEN) {
    BCOPY(data, outp + PPP_HDRLEN + HEADERLEN, datalen);
  }
  outlen = datalen + HEADERLEN;
  MAKEHEADER(outp, f->protocol);
  PUTCHAR(code, outp);
  PUTCHAR(id, outp);
  PUTSHORT(outlen, outp);
  pppWrite(f->unit, outpacket_buf[f->unit], outlen + PPP_HDRLEN);
  FSMDEBUG((LOG_INFO, "fsm_sdata(%s): Sent code %d,%d,%d.\n",
        PROTO_NAME(f), code, id, outlen));
}


/*
 * fsm_input - Input packet.
 */
void
fsm_input(fsm *f, u_char *inpacket, int l)
{
  u_char *inp = inpacket;
  u_char code, id;
  int len;

  /*
  * Parse header (code, id and length).
  * If packet too short, drop it.
  */
  if (l < HEADERLEN) {
    FSMDEBUG((LOG_WARNING, "fsm_input(%x): Rcvd short header.\n",
          f->protocol));
    return;
  }
  GETCHAR(code, inp);
  GETCHAR(id, inp);
  GETSHORT(len, inp);
  if (len < HEADERLEN) {
    FSMDEBUG((LOG_INFO, "fsm_input(%x): Rcvd illegal length.\n",
        f->protocol));
    return;
  }
  if (len > l) {
    FSMDEBUG((LOG_INFO, "fsm_input(%x): Rcvd short packet.\n",
        f->protocol));
    return;
  }
  len -= HEADERLEN;    /* subtract header length */

  if( f->state == LS_INITIAL || f->state == LS_STARTING ) {
    FSMDEBUG((LOG_INFO, "fsm_input(%x): Rcvd packet in state %d (%s).\n",
        f->protocol, f->state, ppperr_strerr[f->state]));
    return;
  }
  FSMDEBUG((LOG_INFO, "fsm_input(%s):%d,%d,%d\n", PROTO_NAME(f), code, id, l));
  /*
   * Action depends on code.
   */
  switch (code) {
    case CONFREQ:
      fsm_rconfreq(f, id, inp, len);
      break;
    
    case CONFACK:
      fsm_rconfack(f, id, inp, len);
      break;
    
    case CONFNAK:
    case CONFREJ:
      fsm_rconfnakrej(f, code, id, inp, len);
      break;
    
    case TERMREQ:
      fsm_rtermreq(f, id, inp, len);
      break;
    
    case TERMACK:
      fsm_rtermack(f);
      break;
    
    case CODEREJ:
      fsm_rcoderej(f, inp, len);
      break;
    
    default:
      if( !f->callbacks->extcode ||
          !(*f->callbacks->extcode)(f, code, id, inp, len) ) {
        fsm_sdata(f, CODEREJ, ++f->id, inpacket, len + HEADERLEN);
      }
      break;
  }
}


/*
 * fsm_protreject - Peer doesn't speak this protocol.
 *
 * Treat this as a catastrophic error (RXJ-).
 */
void
fsm_protreject(fsm *f)
{
  switch( f->state ) {
    case LS_CLOSING:
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      /* fall through */
    case LS_CLOSED:
      f->state = LS_CLOSED;
      if( f->callbacks->finished ) {
        (*f->callbacks->finished)(f);
      }
      break;

    case LS_STOPPING:
    case LS_REQSENT:
    case LS_ACKRCVD:
    case LS_ACKSENT:
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      /* fall through */
    case LS_STOPPED:
      f->state = LS_STOPPED;
      if( f->callbacks->finished ) {
        (*f->callbacks->finished)(f);
      }
      break;
    
    case LS_OPENED:
      if( f->callbacks->down ) {
        (*f->callbacks->down)(f);
      }
      /* Init restart counter, send Terminate-Request */
      f->retransmits = f->maxtermtransmits;
      fsm_sdata(f, TERMREQ, f->reqid = ++f->id,
            (u_char *) f->term_reason, f->term_reason_len);
      TIMEOUT(fsm_timeout, f, f->timeouttime);
      --f->retransmits;
      
      f->state = LS_STOPPING;
      break;
    
    default:
      FSMDEBUG((LOG_INFO, "%s: Protocol-reject event in state %d (%s)!\n",
            PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
    }
}





/**********************************/
/*** LOCAL FUNCTION DEFINITIONS ***/
/**********************************/

/*
 * fsm_timeout - Timeout expired.
 */
static void
fsm_timeout(void *arg)
{
  fsm *f = (fsm *) arg;

  switch (f->state) {
    case LS_CLOSING:
    case LS_STOPPING:
      if( f->retransmits <= 0 ) {
        FSMDEBUG((LOG_WARNING, "%s: timeout sending Terminate-Request state=%d (%s)\n",
             PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
        /*
         * We've waited for an ack long enough.  Peer probably heard us.
         */
        f->state = (f->state == LS_CLOSING)? LS_CLOSED: LS_STOPPED;
        if( f->callbacks->finished ) {
          (*f->callbacks->finished)(f);
        }
      } else {
        FSMDEBUG((LOG_WARNING, "%s: timeout resending Terminate-Requests state=%d (%s)\n",
             PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
        /* Send Terminate-Request */
        fsm_sdata(f, TERMREQ, f->reqid = ++f->id,
            (u_char *) f->term_reason, f->term_reason_len);
        TIMEOUT(fsm_timeout, f, f->timeouttime);
        --f->retransmits;
      }
      break;

    case LS_REQSENT:
    case LS_ACKRCVD:
    case LS_ACKSENT:
      if (f->retransmits <= 0) {
        FSMDEBUG((LOG_WARNING, "%s: timeout sending Config-Requests state=%d (%s)\n",
         PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
        f->state = LS_STOPPED;
        if( (f->flags & OPT_PASSIVE) == 0 && f->callbacks->finished ) {
          (*f->callbacks->finished)(f);
        }
      } else {
        FSMDEBUG((LOG_WARNING, "%s: timeout resending Config-Request state=%d (%s)\n",
         PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
        /* Retransmit the configure-request */
        if (f->callbacks->retransmit) {
          (*f->callbacks->retransmit)(f);
        }
        fsm_sconfreq(f, 1);    /* Re-send Configure-Request */
        if( f->state == LS_ACKRCVD ) {
          f->state = LS_REQSENT;
        }
      }
      break;

    default:
      FSMDEBUG((LOG_INFO, "%s: UNHANDLED timeout event in state %d (%s)!\n",
          PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
  }
}


/*
 * fsm_rconfreq - Receive Configure-Request.
 */
static void
fsm_rconfreq(fsm *f, u_char id, u_char *inp, int len)
{
  int code, reject_if_disagree;

  FSMDEBUG((LOG_INFO, "fsm_rconfreq(%s): Rcvd id %d state=%d (%s)\n", 
        PROTO_NAME(f), id, f->state, ppperr_strerr[f->state]));
  switch( f->state ) {
    case LS_CLOSED:
      /* Go away, we're closed */
      fsm_sdata(f, TERMACK, id, NULL, 0);
      return;
    case LS_CLOSING:
    case LS_STOPPING:
      return;

    case LS_OPENED:
      /* Go down and restart negotiation */
      if( f->callbacks->down ) {
        (*f->callbacks->down)(f);  /* Inform upper layers */
      }
      fsm_sconfreq(f, 0);    /* Send initial Configure-Request */
      break;

    case LS_STOPPED:
      /* Negotiation started by our peer */
      fsm_sconfreq(f, 0);    /* Send initial Configure-Request */
      f->state = LS_REQSENT;
      break;
  }
  
  /*
  * Pass the requested configuration options
  * to protocol-specific code for checking.
  */
  if (f->callbacks->reqci) {    /* Check CI */
    reject_if_disagree = (f->nakloops >= f->maxnakloops);
    code = (*f->callbacks->reqci)(f, inp, &len, reject_if_disagree);
  } else if (len) {
    code = CONFREJ;      /* Reject all CI */
  } else {
    code = CONFACK;
  }
  
  /* send the Ack, Nak or Rej to the peer */
  fsm_sdata(f, (u_char)code, id, inp, len);
  
  if (code == CONFACK) {
    if (f->state == LS_ACKRCVD) {
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      f->state = LS_OPENED;
      if (f->callbacks->up) {
        (*f->callbacks->up)(f);  /* Inform upper layers */
      }
    } else {
      f->state = LS_ACKSENT;
    }
    f->nakloops = 0;
  } else {
    /* we sent CONFACK or CONFREJ */
    if (f->state != LS_ACKRCVD) {
      f->state = LS_REQSENT;
    }
    if( code == CONFNAK ) {
      ++f->nakloops;
    }
  }
}


/*
 * fsm_rconfack - Receive Configure-Ack.
 */
static void
fsm_rconfack(fsm *f, int id, u_char *inp, int len)
{
  FSMDEBUG((LOG_INFO, "fsm_rconfack(%s): Rcvd id %d state=%d (%s)\n",
        PROTO_NAME(f), id, f->state, ppperr_strerr[f->state]));
  
  if (id != f->reqid || f->seen_ack) {   /* Expected id? */
    return; /* Nope, toss... */
  }
  if( !(f->callbacks->ackci? (*f->callbacks->ackci)(f, inp, len): (len == 0)) ) {
    /* Ack is bad - ignore it */
    FSMDEBUG((LOG_INFO, "%s: received bad Ack (length %d)\n",
          PROTO_NAME(f), len));
    return;
  }
  f->seen_ack = 1;
  
  switch (f->state) {
    case LS_CLOSED:
    case LS_STOPPED:
      fsm_sdata(f, TERMACK, (u_char)id, NULL, 0);
      break;
    
    case LS_REQSENT:
      f->state = LS_ACKRCVD;
      f->retransmits = f->maxconfreqtransmits;
      break;
    
    case LS_ACKRCVD:
      /* Huh? an extra valid Ack? oh well... */
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      fsm_sconfreq(f, 0);
      f->state = LS_REQSENT;
      break;
    
    case LS_ACKSENT:
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      f->state = LS_OPENED;
      f->retransmits = f->maxconfreqtransmits;
      if (f->callbacks->up) {
        (*f->callbacks->up)(f);  /* Inform upper layers */
      }
      break;
    
    case LS_OPENED:
      /* Go down and restart negotiation */
      if (f->callbacks->down) {
        (*f->callbacks->down)(f);  /* Inform upper layers */
      }
      fsm_sconfreq(f, 0);    /* Send initial Configure-Request */
      f->state = LS_REQSENT;
      break;
  }
}


/*
 * fsm_rconfnakrej - Receive Configure-Nak or Configure-Reject.
 */
static void
fsm_rconfnakrej(fsm *f, int code, int id, u_char *inp, int len)
{
  int (*proc) (fsm *, u_char *, int);
  int ret;

  FSMDEBUG((LOG_INFO, "fsm_rconfnakrej(%s): Rcvd id %d state=%d (%s)\n",
        PROTO_NAME(f), id, f->state, ppperr_strerr[f->state]));

  if (id != f->reqid || f->seen_ack) { /* Expected id? */
    return;        /* Nope, toss... */
  }
  proc = (code == CONFNAK)? f->callbacks->nakci: f->callbacks->rejci;
  if (!proc || !((ret = proc(f, inp, len)))) {
    /* Nak/reject is bad - ignore it */
    FSMDEBUG((LOG_INFO, "%s: received bad %s (length %d)\n",
          PROTO_NAME(f), (code==CONFNAK? "Nak": "reject"), len));
    return;
  }
  f->seen_ack = 1;

  switch (f->state) {
    case LS_CLOSED:
    case LS_STOPPED:
      fsm_sdata(f, TERMACK, (u_char)id, NULL, 0);
      break;
    
    case LS_REQSENT:
    case LS_ACKSENT:
      /* They didn't agree to what we wanted - try another request */
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      if (ret < 0) {
        f->state = LS_STOPPED;    /* kludge for stopping CCP */
      } else {
        fsm_sconfreq(f, 0);    /* Send Configure-Request */
      }
      break;
    
    case LS_ACKRCVD:
      /* Got a Nak/reject when we had already had an Ack?? oh well... */
      UNTIMEOUT(fsm_timeout, f);  /* Cancel timeout */
      fsm_sconfreq(f, 0);
      f->state = LS_REQSENT;
      break;
    
    case LS_OPENED:
      /* Go down and restart negotiation */
      if (f->callbacks->down) {
        (*f->callbacks->down)(f);  /* Inform upper layers */
      }
      fsm_sconfreq(f, 0);    /* Send initial Configure-Request */
      f->state = LS_REQSENT;
      break;
  }
}


/*
 * fsm_rtermreq - Receive Terminate-Req.
 */
static void
fsm_rtermreq(fsm *f, int id, u_char *p, int len)
{
  LWIP_UNUSED_ARG(p);

  FSMDEBUG((LOG_INFO, "fsm_rtermreq(%s): Rcvd id %d state=%d (%s)\n",
        PROTO_NAME(f), id, f->state, ppperr_strerr[f->state]));

  switch (f->state) {
    case LS_ACKRCVD:
    case LS_ACKSENT:
      f->state = LS_REQSENT;    /* Start over but keep trying */
      break;

    case LS_OPENED:
      if (len > 0) {
        FSMDEBUG((LOG_INFO, "%s terminated by peer (%x)\n", PROTO_NAME(f), p));
      } else {
        FSMDEBUG((LOG_INFO, "%s terminated by peer\n", PROTO_NAME(f)));
      }
      if (f->callbacks->down) {
        (*f->callbacks->down)(f);  /* Inform upper layers */
      }
      f->retransmits = 0;
      f->state = LS_STOPPING;
      TIMEOUT(fsm_timeout, f, f->timeouttime);
      break;
  }

  fsm_sdata(f, TERMACK, (u_char)id, NULL, 0);
}


/*
 * fsm_rtermack - Receive Terminate-Ack.
 */
static void
fsm_rtermack(fsm *f)
{
  FSMDEBUG((LOG_INFO, "fsm_rtermack(%s): state=%d (%s)\n", 
        PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
  
  switch (f->state) {
    case LS_CLOSING:
      UNTIMEOUT(fsm_timeout, f);
      f->state = LS_CLOSED;
      if( f->callbacks->finished ) {
        (*f->callbacks->finished)(f);
      }
      break;

    case LS_STOPPING:
      UNTIMEOUT(fsm_timeout, f);
      f->state = LS_STOPPED;
      if( f->callbacks->finished ) {
        (*f->callbacks->finished)(f);
      }
      break;
    
    case LS_ACKRCVD:
      f->state = LS_REQSENT;
      break;
    
    case LS_OPENED:
      if (f->callbacks->down) {
        (*f->callbacks->down)(f);  /* Inform upper layers */
      }
      fsm_sconfreq(f, 0);
      break;
  }
}


/*
 * fsm_rcoderej - Receive an Code-Reject.
 */
static void
fsm_rcoderej(fsm *f, u_char *inp, int len)
{
  u_char code, id;
  
  FSMDEBUG((LOG_INFO, "fsm_rcoderej(%s): state=%d (%s)\n", 
        PROTO_NAME(f), f->state, ppperr_strerr[f->state]));
  
  if (len < HEADERLEN) {
    FSMDEBUG((LOG_INFO, "fsm_rcoderej: Rcvd short Code-Reject packet!\n"));
    return;
  }
  GETCHAR(code, inp);
  GETCHAR(id, inp);
  FSMDEBUG((LOG_WARNING, "%s: Rcvd Code-Reject for code %d, id %d\n",
        PROTO_NAME(f), code, id));
  
  if( f->state == LS_ACKRCVD ) {
    f->state = LS_REQSENT;
  }
}


/*
 * fsm_sconfreq - Send a Configure-Request.
 */
static void
fsm_sconfreq(fsm *f, int retransmit)
{
  u_char *outp;
  int cilen;
  
  if( f->state != LS_REQSENT && f->state != LS_ACKRCVD && f->state != LS_ACKSENT ) {
    /* Not currently negotiating - reset options */
    if( f->callbacks->resetci ) {
      (*f->callbacks->resetci)(f);
    }
    f->nakloops = 0;
  }
  
  if( !retransmit ) {
    /* New request - reset retransmission counter, use new ID */
    f->retransmits = f->maxconfreqtransmits;
    f->reqid = ++f->id;
  }
  
  f->seen_ack = 0;
  
  /*
   * Make up the request packet
   */
  outp = outpacket_buf[f->unit] + PPP_HDRLEN + HEADERLEN;
  if( f->callbacks->cilen && f->callbacks->addci ) {
    cilen = (*f->callbacks->cilen)(f);
    if( cilen > peer_mru[f->unit] - (int)HEADERLEN ) {
      cilen = peer_mru[f->unit] - HEADERLEN;
    }
    if (f->callbacks->addci) {
      (*f->callbacks->addci)(f, outp, &cilen);
    }
  } else {
    cilen = 0;
  }

  /* send the request to our peer */
  fsm_sdata(f, CONFREQ, f->reqid, outp, cilen);
  
  /* start the retransmit timer */
  --f->retransmits;
  TIMEOUT(fsm_timeout, f, f->timeouttime);
  
  FSMDEBUG((LOG_INFO, "%s: sending Configure-Request, id %d\n",
        PROTO_NAME(f), f->reqid));
}

#endif /* PPP_SUPPORT */