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rcsid[] and sccsid[] and copyright[] are essentially unmaintained (and
unmaintainable).  these days, people use source.  these id's do not provide
any benefit, and do hurt the small install media
(the 33,000 line diff is essentially mechanical)
ok with the idea millert, ok dms

/*	$OpenBSD: fsm.c,v 1.8 2009/10/27 23:59:53 deraadt Exp $	*/

/*
 * fsm.c - {Link, IP} Control Protocol Finite State Machine.
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * TODO:
 * 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(void *);
static void fsm_rconfreq(fsm *, int, 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)

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;
	/* fall through */
    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)(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 an 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 */
	/* fall through */
    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 */
	/* fall through */
    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));
}