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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.
 */

#ifndef lint
static char rcsid[] = "$FreeBSD: src/usr.sbin/pppd/fsm.c,v 1.10.30.1 2008/11/25 02:59:29 kensmith Exp $";
#endif

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

#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <syslog.h>

#include "pppd.h"
#include "fsm.h"

static void fsm_timeout __P((void *));
static void fsm_rconfreq __P((fsm *, int, u_char *, int));
static void fsm_rconfack __P((fsm *, int, u_char *, int));
static void fsm_rconfnakrej __P((fsm *, int, int, u_char *, int));
static void fsm_rtermreq __P((fsm *, int, u_char *, int));
static void fsm_rtermack __P((fsm *));
static void fsm_rcoderej __P((fsm *, u_char *, int));
static void fsm_sconfreq __P((fsm *, int));

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

int peer_mru[NUM_PPP];


/*
 * fsm_init - Initialize fsm.
 *
 * Initialize fsm state.
 */
void
fsm_init(f)
    fsm *f;
{
    f->state = INITIAL;
    f->flags = 0;
    f->id = 0;                      /* XXX Start with random id? */
    f->timeouttime = DEFTIMEOUT;
    f->maxconfreqtransmits = DEFMAXCONFREQS;
    f->maxtermtransmits = DEFMAXTERMREQS;
    f->maxnakloops = DEFMAXNAKLOOPS;
    f->term_reason_len = 0;
}


/*
 * fsm_lowerup - The lower layer is up.
 */
void
fsm_lowerup(f)
    fsm *f;
{
    switch( f->state ){
    case INITIAL:
      f->state = CLOSED;
      break;

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

    default:
      FSMDEBUG((LOG_INFO, "%s: Up event in state %d!",
              PROTO_NAME(f), f->state));
    }
}


/*
 * fsm_lowerdown - The lower layer is down.
 *
 * Cancel all timeouts and inform upper layers.
 */
void
fsm_lowerdown(f)
    fsm *f;
{
    switch( f->state ){
    case CLOSED:
      f->state = INITIAL;
      break;

    case STOPPED:
      f->state = STARTING;
      if( f->callbacks->starting )
          (*f->callbacks->starting)(f);
      break;

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

    case STOPPING:
    case REQSENT:
    case ACKRCVD:
    case ACKSENT:
      f->state = STARTING;
      UNTIMEOUT(fsm_timeout, f);    /* Cancel timeout */
      break;

    case OPENED:
      if( f->callbacks->down )
          (*f->callbacks->down)(f);
      f->state = STARTING;
      break;

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


/*
 * fsm_open - Link is allowed to come up.
 */
void
fsm_open(f)
    fsm *f;
{
    switch( f->state ){
    case INITIAL:
      f->state = STARTING;
      if( f->callbacks->starting )
          (*f->callbacks->starting)(f);
      break;

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

    case CLOSING:
      f->state = STOPPING;
      /* FALLTHROUGH */
    case STOPPED:
    case OPENED:
      if( f->flags & OPT_RESTART ){
          fsm_lowerdown(f);
          fsm_lowerup(f);
      }
      break;
    }
}


/*
 * fsm_close - Start closing connection.
 *
 * Cancel timeouts and either initiate close or possibly go directly to
 * the CLOSED state.
 */
void
fsm_close(f, reason)
    fsm *f;
    char *reason;
{
    f->term_reason = reason;
    f->term_reason_len = (reason == NULL? 0: strlen(reason));
    switch( f->state ){
    case STARTING:
      f->state = INITIAL;
      break;
    case STOPPED:
      f->state = CLOSED;
      break;
    case STOPPING:
      f->state = CLOSING;
      break;

    case REQSENT:
    case ACKRCVD:
    case ACKSENT:
    case OPENED:
      if( f->state != 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 = CLOSING;
      break;
    }
}


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

    switch (f->state) {
    case CLOSING:
    case STOPPING:
      if( f->retransmits <= 0 ){
          /*
           * We've waited for an ack long enough.  Peer probably heard us.
           */
          f->state = (f->state == CLOSING)? CLOSED: STOPPED;
          if( f->callbacks->finished )
            (*f->callbacks->finished)(f);
      } else {
          /* 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 REQSENT:
    case ACKRCVD:
    case ACKSENT:
      if (f->retransmits <= 0) {
          syslog(LOG_WARNING, "%s: timeout sending Config-Requests",
               PROTO_NAME(f));
          f->state = STOPPED;
          if( (f->flags & OPT_PASSIVE) == 0 && f->callbacks->finished )
            (*f->callbacks->finished)(f);

      } else {
          /* Retransmit the configure-request */
          if (f->callbacks->retransmit)
            (*f->callbacks->retransmit)(f);
          fsm_sconfreq(f, 1);       /* Re-send Configure-Request */
          if( f->state == ACKRCVD )
            f->state = REQSENT;
      }
      break;

    default:
      FSMDEBUG((LOG_INFO, "%s: Timeout event in state %d!",
              PROTO_NAME(f), f->state));
    }
}


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

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

    if( f->state == INITIAL || f->state == STARTING ){
      FSMDEBUG((LOG_INFO, "fsm_input(%x): Rcvd packet in state %d.",
              f->protocol, f->state));
      return;
    }

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

    FSMDEBUG((LOG_INFO, "fsm_rconfreq(%s): Rcvd id %d.", PROTO_NAME(f), id));
    switch( f->state ){
    case CLOSED:
      /* Go away, we're closed */
      fsm_sdata(f, TERMACK, id, NULL, 0);
      return;
    case CLOSING:
    case STOPPING:
      return;

    case 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 STOPPED:
      /* Negotiation started by our peer */
      fsm_sconfreq(f, 0);           /* Send initial Configure-Request */
      f->state = 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, code, id, inp, len);

    if (code == CONFACK) {
      if (f->state == ACKRCVD) {
          UNTIMEOUT(fsm_timeout, f);      /* Cancel timeout */
          f->state = OPENED;
          if (f->callbacks->up)
            (*f->callbacks->up)(f); /* Inform upper layers */
      } else
          f->state = ACKSENT;
      f->nakloops = 0;

    } else {
      /* we sent CONFACK or CONFREJ */
      if (f->state != ACKRCVD)
          f->state = REQSENT;
      if( code == CONFNAK )
          ++f->nakloops;
    }
}


/*
 * fsm_rconfack - Receive Configure-Ack.
 */
static void
fsm_rconfack(f, id, inp, len)
    fsm *f;
    int id;
    u_char *inp;
    int len;
{
    FSMDEBUG((LOG_INFO, "fsm_rconfack(%s): Rcvd id %d.",
            PROTO_NAME(f), id));

    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 */
      log_packet(inp, len, "Received bad configure-ack: ", LOG_ERR);
      FSMDEBUG((LOG_INFO, "%s: received bad Ack (length %d)",
              PROTO_NAME(f), len));
      return;
    }
    f->seen_ack = 1;

    switch (f->state) {
    case CLOSED:
    case STOPPED:
      fsm_sdata(f, TERMACK, id, NULL, 0);
      break;

    case REQSENT:
      f->state = ACKRCVD;
      f->retransmits = f->maxconfreqtransmits;
      break;

    case ACKRCVD:
      /* Huh? an extra valid Ack? oh well... */
      UNTIMEOUT(fsm_timeout, f);    /* Cancel timeout */
      fsm_sconfreq(f, 0);
      f->state = REQSENT;
      break;

    case ACKSENT:
      UNTIMEOUT(fsm_timeout, f);    /* Cancel timeout */
      f->state = OPENED;
      f->retransmits = f->maxconfreqtransmits;
      if (f->callbacks->up)
          (*f->callbacks->up)(f);   /* Inform upper layers */
      break;

    case 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 = REQSENT;
      break;
    }
}


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

    FSMDEBUG((LOG_INFO, "fsm_rconfnakrej(%s): Rcvd id %d.",
            PROTO_NAME(f), id));

    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 */
      log_packet(inp, len, "Received bad configure-nak/rej: ", LOG_ERR);
      FSMDEBUG((LOG_INFO, "%s: received bad %s (length %d)",
              PROTO_NAME(f), (code==CONFNAK? "Nak": "reject"), len));
      return;
    }
    f->seen_ack = 1;

    switch (f->state) {
    case CLOSED:
    case STOPPED:
      fsm_sdata(f, TERMACK, id, NULL, 0);
      break;

    case REQSENT:
    case ACKSENT:
      /* They didn't agree to what we wanted - try another request */
      UNTIMEOUT(fsm_timeout, f);    /* Cancel timeout */
      if (ret < 0)
          f->state = STOPPED;       /* kludge for stopping CCP */
      else
          fsm_sconfreq(f, 0);       /* Send Configure-Request */
      break;

    case 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 = REQSENT;
      break;

    case 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 = REQSENT;
      break;
    }
}


/*
 * fsm_rtermreq - Receive Terminate-Req.
 */
static void
fsm_rtermreq(f, id, p, len)
    fsm *f;
    int id;
    u_char *p;
    int len;
{
    char str[80];

    FSMDEBUG((LOG_INFO, "fsm_rtermreq(%s): Rcvd id %d.",
            PROTO_NAME(f), id));

    switch (f->state) {
    case ACKRCVD:
    case ACKSENT:
      f->state = REQSENT;           /* Start over but keep trying */
      break;

    case OPENED:
      if (len > 0) {
          fmtmsg(str, sizeof(str), "%0.*v", len, p);
          syslog(LOG_INFO, "%s terminated by peer (%s)", PROTO_NAME(f), str);
      } else
          syslog(LOG_INFO, "%s terminated by peer", PROTO_NAME(f));
      if (f->callbacks->down)
          (*f->callbacks->down)(f); /* Inform upper layers */
      f->retransmits = 0;
      f->state = STOPPING;
      TIMEOUT(fsm_timeout, f, f->timeouttime);
      break;
    }

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


/*
 * fsm_rtermack - Receive Terminate-Ack.
 */
static void
fsm_rtermack(f)
    fsm *f;
{
    FSMDEBUG((LOG_INFO, "fsm_rtermack(%s).", PROTO_NAME(f)));

    switch (f->state) {
    case CLOSING:
      UNTIMEOUT(fsm_timeout, f);
      f->state = CLOSED;
      if( f->callbacks->finished )
          (*f->callbacks->finished)(f);
      break;
    case STOPPING:
      UNTIMEOUT(fsm_timeout, f);
      f->state = STOPPED;
      if( f->callbacks->finished )
          (*f->callbacks->finished)(f);
      break;

    case ACKRCVD:
      f->state = REQSENT;
      break;

    case OPENED:
      if (f->callbacks->down)
          (*f->callbacks->down)(f); /* Inform upper layers */
      fsm_sconfreq(f, 0);
      break;
    }
}


/*
 * fsm_rcoderej - Receive a Code-Reject.
 */
static void
fsm_rcoderej(f, inp, len)
    fsm *f;
    u_char *inp;
    int len;
{
    u_char code, id;

    FSMDEBUG((LOG_INFO, "fsm_rcoderej(%s).", PROTO_NAME(f)));

    if (len < HEADERLEN) {
      FSMDEBUG((LOG_INFO, "fsm_rcoderej: Rcvd short Code-Reject packet!"));
      return;
    }
    GETCHAR(code, inp);
    GETCHAR(id, inp);
    syslog(LOG_WARNING, "%s: Rcvd Code-Reject for code %d, id %d",
         PROTO_NAME(f), code, id);

    if( f->state == ACKRCVD )
      f->state = REQSENT;
}


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

    case STOPPING:
    case REQSENT:
    case ACKRCVD:
    case ACKSENT:
      UNTIMEOUT(fsm_timeout, f);    /* Cancel timeout */
      /* FALLTHROUGH */
    case STOPPED:
      f->state = STOPPED;
      if( f->callbacks->finished )
          (*f->callbacks->finished)(f);
      break;

    case 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 = STOPPING;
      break;

    default:
      FSMDEBUG((LOG_INFO, "%s: Protocol-reject event in state %d!",
              PROTO_NAME(f), f->state));
    }
}


/*
 * fsm_sconfreq - Send a Configure-Request.
 */
static void
fsm_sconfreq(f, retransmit)
    fsm *f;
    int retransmit;
{
    u_char *outp;
    int cilen;

    if( f->state != REQSENT && f->state != ACKRCVD && f->state != 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 + PPP_HDRLEN + HEADERLEN;
    if( f->callbacks->cilen && f->callbacks->addci ){
      cilen = (*f->callbacks->cilen)(f);
      if( cilen > peer_mru[f->unit] - 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",
            PROTO_NAME(f), f->reqid));
}


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

    /* Adjust length to be smaller than MTU */
    outp = outpacket_buf;
    if (datalen > peer_mru[f->unit] - 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);
    output(f->unit, outpacket_buf, outlen + PPP_HDRLEN);

    FSMDEBUG((LOG_INFO, "fsm_sdata(%s): Sent code %d, id %d.",
            PROTO_NAME(f), code, id));
}

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