lcp.c

经典的ppp程序

/*
 * 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.
 */

#define RCSID	"$Id: lcp.c,v 1.57 2001/03/08 05:11:14 paulus Exp $"

/*
 * TODO:
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

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

static const char rcsid[] = RCSID;

/*
 * When the link comes up we want to be able to wait for a short while,
 * or until seeing some input from the peer, before starting to send
 * configure-requests.  We do this by delaying the fsm_lowerup call.
 */
/* steal a bit in fsm flags word */
#define DELAYED_UP	0x100

static void lcp_delayed_up __P((void *));

/*
 * LCP-related command-line options.
 */
int	lcp_echo_interval = 0; 	/* Interval between LCP echo-requests */
int	lcp_echo_fails = 0;	/* Tolerance to unanswered echo-requests */
bool	lax_recv = 0;		/* accept control chars in asyncmap */
bool	noendpoint = 0;		/* don't send/accept endpoint discriminator */

static int noopt __P((char **));

#ifdef HAVE_MULTILINK
static int setendpoint __P((char **));
static void printendpoint __P((option_t *, void (*)(void *, char *, ...),
			       void *));
#endif /* HAVE_MULTILINK */

static option_t lcp_option_list[] = {
    /* LCP options */
    { "-all", o_special_noarg, (void *)noopt,
      "Don't request/allow any LCP options" },

    { "noaccomp", o_bool, &lcp_wantoptions[0].neg_accompression,
      "Disable address/control compression",
      OPT_A2CLR, &lcp_allowoptions[0].neg_accompression },
    { "-ac", o_bool, &lcp_wantoptions[0].neg_accompression,
      "Disable address/control compression",
      OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_accompression },

    { "asyncmap", o_uint32, &lcp_wantoptions[0].asyncmap,
      "Set asyncmap (for received packets)",
      OPT_OR, &lcp_wantoptions[0].neg_asyncmap },
    { "-as", o_uint32, &lcp_wantoptions[0].asyncmap,
      "Set asyncmap (for received packets)",
      OPT_ALIAS | OPT_OR, &lcp_wantoptions[0].neg_asyncmap },
    { "default-asyncmap", o_uint32, &lcp_wantoptions[0].asyncmap,
      "Disable asyncmap negotiation",
      OPT_OR | OPT_NOARG | OPT_VAL(~0U) | OPT_A2CLR,
      &lcp_allowoptions[0].neg_asyncmap },
    { "-am", o_uint32, &lcp_wantoptions[0].asyncmap,
      "Disable asyncmap negotiation",
      OPT_ALIAS | OPT_OR | OPT_NOARG | OPT_VAL(~0U) | OPT_A2CLR,
      &lcp_allowoptions[0].neg_asyncmap },

    { "nomagic", o_bool, &lcp_wantoptions[0].neg_magicnumber,
      "Disable magic number negotiation (looped-back line detection)",
      OPT_A2CLR, &lcp_allowoptions[0].neg_magicnumber },
    { "-mn", o_bool, &lcp_wantoptions[0].neg_magicnumber,
      "Disable magic number negotiation (looped-back line detection)",
      OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_magicnumber },

    { "mru", o_int, &lcp_wantoptions[0].mru,
      "Set MRU (maximum received packet size) for negotiation",
      OPT_PRIO, &lcp_wantoptions[0].neg_mru },
    { "default-mru", o_bool, &lcp_wantoptions[0].neg_mru,
      "Disable MRU negotiation (use default 1500)",
      OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_mru },
    { "-mru", o_bool, &lcp_wantoptions[0].neg_mru,
      "Disable MRU negotiation (use default 1500)",
      OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_mru },

    { "mtu", o_int, &lcp_allowoptions[0].mru,
      "Set our MTU", OPT_LIMITS, NULL, MAXMRU, MINMRU },

    { "nopcomp", o_bool, &lcp_wantoptions[0].neg_pcompression,
      "Disable protocol field compression",
      OPT_A2CLR, &lcp_allowoptions[0].neg_pcompression },
    { "-pc", o_bool, &lcp_wantoptions[0].neg_pcompression,
      "Disable protocol field compression",
      OPT_ALIAS | OPT_A2CLR, &lcp_allowoptions[0].neg_pcompression },

    { "passive", o_bool, &lcp_wantoptions[0].passive,
      "Set passive mode", 1 },
    { "-p", o_bool, &lcp_wantoptions[0].passive,
      "Set passive mode", OPT_ALIAS | 1 },

    { "silent", o_bool, &lcp_wantoptions[0].silent,
      "Set silent mode", 1 },

    { "lcp-echo-failure", o_int, &lcp_echo_fails,
      "Set number of consecutive echo failures to indicate link failure",
      OPT_PRIO },
    { "lcp-echo-interval", o_int, &lcp_echo_interval,
      "Set time in seconds between LCP echo requests", OPT_PRIO },
    { "lcp-restart", o_int, &lcp_fsm[0].timeouttime,
      "Set time in seconds between LCP retransmissions", OPT_PRIO },
    { "lcp-max-terminate", o_int, &lcp_fsm[0].maxtermtransmits,
      "Set maximum number of LCP terminate-request transmissions", OPT_PRIO },
    { "lcp-max-configure", o_int, &lcp_fsm[0].maxconfreqtransmits,
      "Set maximum number of LCP configure-request transmissions", OPT_PRIO },
    { "lcp-max-failure", o_int, &lcp_fsm[0].maxnakloops,
      "Set limit on number of LCP configure-naks", OPT_PRIO },

    { "receive-all", o_bool, &lax_recv,
      "Accept all received control characters", 1 },

#ifdef HAVE_MULTILINK
    { "mrru", o_int, &lcp_wantoptions[0].mrru,
      "Maximum received packet size for multilink bundle",
      OPT_PRIO, &lcp_wantoptions[0].neg_mrru },

    { "mpshortseq", o_bool, &lcp_wantoptions[0].neg_ssnhf,
      "Use short sequence numbers in multilink headers",
      OPT_PRIO | 1, &lcp_allowoptions[0].neg_ssnhf },
    { "nompshortseq", o_bool, &lcp_wantoptions[0].neg_ssnhf,
      "Don't use short sequence numbers in multilink headers",
      OPT_PRIOSUB | OPT_A2CLR, &lcp_allowoptions[0].neg_ssnhf },

    { "endpoint", o_special, (void *) setendpoint,
      "Endpoint discriminator for multilink",
      OPT_PRIO | OPT_A2PRINTER, (void *) printendpoint },
#endif /* HAVE_MULTILINK */

    { "noendpoint", o_bool, &noendpoint,
      "Don't send or accept multilink endpoint discriminator", 1 },

    {NULL}
};

/* 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 */

static int lcp_echos_pending = 0;	/* Number of outstanding echo msgs */
static int lcp_echo_number   = 0;	/* ID number of next echo frame */
static int lcp_echo_timer_running = 0;  /* set 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,
    lcp_option_list,
    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 + 2 */
#define CILEN_CHAP	5	/* CILEN_VOID + 2 + 1 */
#define CILEN_LONG	6	/* CILEN_VOID + 4 */
#define CILEN_LQR	8	/* CILEN_VOID + 2 + 4 */
#define CILEN_CBCP	3

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

/*
 * noopt - Disable all options (why?).
 */
static int
noopt(argv)
    char **argv;
{
    BZERO((char *) &lcp_wantoptions[0], sizeof (struct lcp_options));
    BZERO((char *) &lcp_allowoptions[0], sizeof (struct lcp_options));

    return (1);
}

#ifdef HAVE_MULTILINK
static int
setendpoint(argv)
    char **argv;
{
    if (str_to_epdisc(&lcp_wantoptions[0].endpoint, *argv)) {
	lcp_wantoptions[0].neg_endpoint = 1;
	return 1;
    }
    option_error("Can't parse '%s' as an endpoint discriminator", *argv);
    return 0;
}

static void
printendpoint(opt, printer, arg)
    option_t *opt;
    void (*printer) __P((void *, char *, ...));
    void *arg;
{
	printer(arg, "%s", epdisc_to_str(&lcp_wantoptions[0].endpoint));
}
#endif /* HAVE_MULTILINK */

/*
 * 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);

    BZERO(wo, sizeof(*wo));
    wo->neg_mru = 1;
    wo->mru = DEFMRU;
    wo->neg_asyncmap = 1;
    wo->chap_mdtype = CHAP_DIGEST_MD5;
    wo->neg_magicnumber = 1;
    wo->neg_pcompression = 1;
    wo->neg_accompression = 1;

    BZERO(ao, sizeof(*ao));
    ao->neg_mru = 1;
    ao->mru = MAXMRU;
    ao->neg_asyncmap = 1;
    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;
#ifdef CBCP_SUPPORT
    ao->neg_cbcp = 1;
#endif
    ao->neg_endpoint = 1;
}


/*
 * 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 &= ~(OPT_PASSIVE | OPT_SILENT);
    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)
	new_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];
    fsm *f = &lcp_fsm[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_send_config(unit, PPP_MRU, 0xffffffff, 0, 0);
    ppp_recv_config(unit, PPP_MRU, (lax_recv? 0: 0xffffffff),
		    wo->neg_pcompression, wo->neg_accompression);
    peer_mru[unit] = PPP_MRU;

    if (listen_time != 0) {
	f->flags |= DELAYED_UP;
	timeout(lcp_delayed_up, f, 0, listen_time * 1000);
    } else
	fsm_lowerup(f);
}


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

    if (f->flags & DELAYED_UP)
	f->flags &= ~DELAYED_UP;
    else
	fsm_lowerdown(&lcp_fsm[unit]);
}


/*
 * lcp_delayed_up - Bring the lower layer up now.
 */
static void
lcp_delayed_up(arg)
    void *arg;
{
    fsm *f = arg;

    if (f->flags & DELAYED_UP) {
	f->flags &= ~DELAYED_UP;
	fsm_lowerup(f);
    }
}


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

    if (f->flags & DELAYED_UP) {
	f->flags &= ~DELAYED_UP;
	fsm_lowerup(f);
    }
    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;
	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 an 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;

    if (len < 2) {
	LCPDEBUG(("lcp_rprotrej: Rcvd short Protocol-Reject packet!"));
	return;
    }

    GETSHORT(prot, inp);

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

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