PPPoE updates: don't exit if discovery fails, cope with both

[ppp.git] / pppd / ccp.c

/*
 * ccp.c - PPP Compression Control Protocol.
 *
 * Copyright (c) 1994-2002 Paul Mackerras. 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(s) of the authors of this software must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission.
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Paul Mackerras
 *     <paulus@samba.org>".
 *
 * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL THE AUTHORS 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.
 */

#define RCSID   "$Id: ccp.c,v 1.46 2003/05/01 12:30:28 paulus Exp $"

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

#include "pppd.h"
#include "fsm.h"
#include "ccp.h"
#include <net/ppp-comp.h>

#ifdef MPPE
#include "chap_ms.h"    /* mppe_xxxx_key, mppe_keys_set */
#include "lcp.h"        /* lcp_close(), lcp_fsm */
#endif

static const char rcsid[] = RCSID;

/*
 * Unfortunately there is a bug in zlib which means that using a
 * size of 8 (window size = 256) for Deflate compression will cause
 * buffer overruns and kernel crashes in the deflate module.
 * Until this is fixed we only accept sizes in the range 9 .. 15.
 * Thanks to James Carlson for pointing this out.
 */
#define DEFLATE_MIN_WORKS       9

/*
 * Command-line options.
 */
static int setbsdcomp __P((char **));
static int setdeflate __P((char **));
static char bsd_value[8];
static char deflate_value[8];

/*
 * Option variables.
 */
#ifdef MPPE
bool refuse_mppe_stateful = 1;          /* Allow stateful mode? */
#endif

static option_t ccp_option_list[] = {
    { "noccp", o_bool, &ccp_protent.enabled_flag,
      "Disable CCP negotiation" },
    { "-ccp", o_bool, &ccp_protent.enabled_flag,
      "Disable CCP negotiation", OPT_ALIAS },

    { "bsdcomp", o_special, (void *)setbsdcomp,
      "Request BSD-Compress packet compression",
      OPT_PRIO | OPT_A2STRVAL | OPT_STATIC, bsd_value },
    { "nobsdcomp", o_bool, &ccp_wantoptions[0].bsd_compress,
      "don't allow BSD-Compress", OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].bsd_compress },
    { "-bsdcomp", o_bool, &ccp_wantoptions[0].bsd_compress,
      "don't allow BSD-Compress", OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].bsd_compress },

    { "deflate", o_special, (void *)setdeflate,
      "request Deflate compression",
      OPT_PRIO | OPT_A2STRVAL | OPT_STATIC, deflate_value },
    { "nodeflate", o_bool, &ccp_wantoptions[0].deflate,
      "don't allow Deflate compression", OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].deflate },
    { "-deflate", o_bool, &ccp_wantoptions[0].deflate,
      "don't allow Deflate compression", OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].deflate },

    { "nodeflatedraft", o_bool, &ccp_wantoptions[0].deflate_draft,
      "don't use draft deflate #", OPT_A2COPY,
      &ccp_allowoptions[0].deflate_draft },

    { "predictor1", o_bool, &ccp_wantoptions[0].predictor_1,
      "request Predictor-1", OPT_PRIO | 1 },
    { "nopredictor1", o_bool, &ccp_wantoptions[0].predictor_1,
      "don't allow Predictor-1", OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].predictor_1 },
    { "-predictor1", o_bool, &ccp_wantoptions[0].predictor_1,
      "don't allow Predictor-1", OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLR,
      &ccp_allowoptions[0].predictor_1 },

#ifdef MPPE
    /* MPPE options are symmetrical ... we only set wantoptions here */
    { "require-mppe", o_bool, &ccp_wantoptions[0].mppe,
      "require MPPE encryption",
      OPT_PRIO | MPPE_OPT_40 | MPPE_OPT_128 },
    { "+mppe", o_bool, &ccp_wantoptions[0].mppe,
      "require MPPE encryption",
      OPT_ALIAS | OPT_PRIO | MPPE_OPT_40 | MPPE_OPT_128 },
    { "nomppe", o_bool, &ccp_wantoptions[0].mppe,
      "don't allow MPPE encryption", OPT_PRIO },
    { "-mppe", o_bool, &ccp_wantoptions[0].mppe,
      "don't allow MPPE encryption", OPT_ALIAS | OPT_PRIO },

    /* We use ccp_allowoptions[0].mppe as a junk var ... it is reset later */
    { "require-mppe-40", o_bool, &ccp_allowoptions[0].mppe,
      "require MPPE 40-bit encryption", OPT_PRIO | OPT_A2OR | MPPE_OPT_40,
      &ccp_wantoptions[0].mppe },
    { "+mppe-40", o_bool, &ccp_allowoptions[0].mppe,
      "require MPPE 40-bit encryption", OPT_PRIO | OPT_A2OR | MPPE_OPT_40,
      &ccp_wantoptions[0].mppe },
    { "nomppe-40", o_bool, &ccp_allowoptions[0].mppe,
      "don't allow MPPE 40-bit encryption",
      OPT_PRIOSUB | OPT_A2CLRB | MPPE_OPT_40, &ccp_wantoptions[0].mppe },
    { "-mppe-40", o_bool, &ccp_allowoptions[0].mppe,
      "don't allow MPPE 40-bit encryption",
      OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLRB | MPPE_OPT_40,
      &ccp_wantoptions[0].mppe },

    { "require-mppe-128", o_bool, &ccp_allowoptions[0].mppe,
      "require MPPE 128-bit encryption", OPT_PRIO | OPT_A2OR | MPPE_OPT_128,
      &ccp_wantoptions[0].mppe },
    { "+mppe-128", o_bool, &ccp_allowoptions[0].mppe,
      "require MPPE 128-bit encryption",
      OPT_ALIAS | OPT_PRIO | OPT_A2OR | MPPE_OPT_128,
      &ccp_wantoptions[0].mppe },
    { "nomppe-128", o_bool, &ccp_allowoptions[0].mppe,
      "don't allow MPPE 128-bit encryption",
      OPT_PRIOSUB | OPT_A2CLRB | MPPE_OPT_128, &ccp_wantoptions[0].mppe },
    { "-mppe-128", o_bool, &ccp_allowoptions[0].mppe,
      "don't allow MPPE 128-bit encryption",
      OPT_ALIAS | OPT_PRIOSUB | OPT_A2CLRB | MPPE_OPT_128,
      &ccp_wantoptions[0].mppe },

    /* strange one; we always request stateless, but will we allow stateful? */
    { "mppe-stateful", o_bool, &refuse_mppe_stateful,
      "allow MPPE stateful mode", OPT_PRIO },
    { "nomppe-stateful", o_bool, &refuse_mppe_stateful,
      "disallow MPPE stateful mode", OPT_PRIO | 1 },
#endif /* MPPE */

    { NULL }
};

/*
 * Protocol entry points from main code.
 */
static void ccp_init __P((int unit));
static void ccp_open __P((int unit));
static void ccp_close __P((int unit, char *));
static void ccp_lowerup __P((int unit));
static void ccp_lowerdown __P((int));
static void ccp_input __P((int unit, u_char *pkt, int len));
static void ccp_protrej __P((int unit));
static int  ccp_printpkt __P((u_char *pkt, int len,
                              void (*printer) __P((void *, char *, ...)),
                              void *arg));
static void ccp_datainput __P((int unit, u_char *pkt, int len));

struct protent ccp_protent = {
    PPP_CCP,
    ccp_init,
    ccp_input,
    ccp_protrej,
    ccp_lowerup,
    ccp_lowerdown,
    ccp_open,
    ccp_close,
    ccp_printpkt,
    ccp_datainput,
    1,
    "CCP",
    "Compressed",
    ccp_option_list,
    NULL,
    NULL,
    NULL
};

fsm ccp_fsm[NUM_PPP];
ccp_options ccp_wantoptions[NUM_PPP];   /* what to request the peer to use */
ccp_options ccp_gotoptions[NUM_PPP];    /* what the peer agreed to do */
ccp_options ccp_allowoptions[NUM_PPP];  /* what we'll agree to do */
ccp_options ccp_hisoptions[NUM_PPP];    /* what we agreed to do */

/*
 * Callbacks for fsm code.
 */
static void ccp_resetci __P((fsm *));
static int  ccp_cilen __P((fsm *));
static void ccp_addci __P((fsm *, u_char *, int *));
static int  ccp_ackci __P((fsm *, u_char *, int));
static int  ccp_nakci __P((fsm *, u_char *, int));
static int  ccp_rejci __P((fsm *, u_char *, int));
static int  ccp_reqci __P((fsm *, u_char *, int *, int));
static void ccp_up __P((fsm *));
static void ccp_down __P((fsm *));
static int  ccp_extcode __P((fsm *, int, int, u_char *, int));
static void ccp_rack_timeout __P((void *));
static char *method_name __P((ccp_options *, ccp_options *));

static fsm_callbacks ccp_callbacks = {
    ccp_resetci,
    ccp_cilen,
    ccp_addci,
    ccp_ackci,
    ccp_nakci,
    ccp_rejci,
    ccp_reqci,
    ccp_up,
    ccp_down,
    NULL,
    NULL,
    NULL,
    NULL,
    ccp_extcode,
    "CCP"
};

/*
 * Do we want / did we get any compression?
 */
#define ANY_COMPRESS(opt)       ((opt).deflate || (opt).bsd_compress \
                                 || (opt).predictor_1 || (opt).predictor_2 \
                                 || (opt).mppe)

/*
 * Local state (mainly for handling reset-reqs and reset-acks).
 */
static int ccp_localstate[NUM_PPP];
#define RACK_PENDING    1       /* waiting for reset-ack */
#define RREQ_REPEAT     2       /* send another reset-req if no reset-ack */

#define RACKTIMEOUT     1       /* second */

static int all_rejected[NUM_PPP];       /* we rejected all peer's options */

/*
 * Option parsing.
 */
static int
setbsdcomp(argv)
    char **argv;
{
    int rbits, abits;
    char *str, *endp;

    str = *argv;
    abits = rbits = strtol(str, &endp, 0);
    if (endp != str && *endp == ',') {
        str = endp + 1;
        abits = strtol(str, &endp, 0);
    }
    if (*endp != 0 || endp == str) {
        option_error("invalid parameter '%s' for bsdcomp option", *argv);
        return 0;
    }
    if ((rbits != 0 && (rbits < BSD_MIN_BITS || rbits > BSD_MAX_BITS))
        || (abits != 0 && (abits < BSD_MIN_BITS || abits > BSD_MAX_BITS))) {
        option_error("bsdcomp option values must be 0 or %d .. %d",
                     BSD_MIN_BITS, BSD_MAX_BITS);
        return 0;
    }
    if (rbits > 0) {
        ccp_wantoptions[0].bsd_compress = 1;
        ccp_wantoptions[0].bsd_bits = rbits;
    } else
        ccp_wantoptions[0].bsd_compress = 0;
    if (abits > 0) {
        ccp_allowoptions[0].bsd_compress = 1;
        ccp_allowoptions[0].bsd_bits = abits;
    } else
        ccp_allowoptions[0].bsd_compress = 0;
    slprintf(bsd_value, sizeof(bsd_value),
             rbits == abits? "%d": "%d,%d", rbits, abits);

    return 1;
}

static int
setdeflate(argv)
    char **argv;
{
    int rbits, abits;
    char *str, *endp;

    str = *argv;
    abits = rbits = strtol(str, &endp, 0);
    if (endp != str && *endp == ',') {
        str = endp + 1;
        abits = strtol(str, &endp, 0);
    }
    if (*endp != 0 || endp == str) {
        option_error("invalid parameter '%s' for deflate option", *argv);
        return 0;
    }
    if ((rbits != 0 && (rbits < DEFLATE_MIN_SIZE || rbits > DEFLATE_MAX_SIZE))
        || (abits != 0 && (abits < DEFLATE_MIN_SIZE
                          || abits > DEFLATE_MAX_SIZE))) {
        option_error("deflate option values must be 0 or %d .. %d",
                     DEFLATE_MIN_SIZE, DEFLATE_MAX_SIZE);
        return 0;
    }
    if (rbits == DEFLATE_MIN_SIZE || abits == DEFLATE_MIN_SIZE) {
        if (rbits == DEFLATE_MIN_SIZE)
            rbits = DEFLATE_MIN_WORKS;
        if (abits == DEFLATE_MIN_SIZE)
            abits = DEFLATE_MIN_WORKS;
        warn("deflate option value of %d changed to %d to avoid zlib bug",
             DEFLATE_MIN_SIZE, DEFLATE_MIN_WORKS);
    }
    if (rbits > 0) {
        ccp_wantoptions[0].deflate = 1;
        ccp_wantoptions[0].deflate_size = rbits;
    } else
        ccp_wantoptions[0].deflate = 0;
    if (abits > 0) {
        ccp_allowoptions[0].deflate = 1;
        ccp_allowoptions[0].deflate_size = abits;
    } else
        ccp_allowoptions[0].deflate = 0;
    slprintf(deflate_value, sizeof(deflate_value),
             rbits == abits? "%d": "%d,%d", rbits, abits);

    return 1;
}

/*
 * ccp_init - initialize CCP.
 */
static void
ccp_init(unit)
    int unit;
{
    fsm *f = &ccp_fsm[unit];

    f->unit = unit;
    f->protocol = PPP_CCP;
    f->callbacks = &ccp_callbacks;
    fsm_init(f);

    memset(&ccp_wantoptions[unit],  0, sizeof(ccp_options));
    memset(&ccp_gotoptions[unit],   0, sizeof(ccp_options));
    memset(&ccp_allowoptions[unit], 0, sizeof(ccp_options));
    memset(&ccp_hisoptions[unit],   0, sizeof(ccp_options));

    ccp_wantoptions[0].deflate = 1;
    ccp_wantoptions[0].deflate_size = DEFLATE_MAX_SIZE;
    ccp_wantoptions[0].deflate_correct = 1;
    ccp_wantoptions[0].deflate_draft = 1;
    ccp_allowoptions[0].deflate = 1;
    ccp_allowoptions[0].deflate_size = DEFLATE_MAX_SIZE;
    ccp_allowoptions[0].deflate_correct = 1;
    ccp_allowoptions[0].deflate_draft = 1;

    ccp_wantoptions[0].bsd_compress = 1;
    ccp_wantoptions[0].bsd_bits = BSD_MAX_BITS;
    ccp_allowoptions[0].bsd_compress = 1;
    ccp_allowoptions[0].bsd_bits = BSD_MAX_BITS;

    ccp_allowoptions[0].predictor_1 = 1;
}

/*
 * ccp_open - CCP is allowed to come up.
 */
static void
ccp_open(unit)
    int unit;
{
    fsm *f = &ccp_fsm[unit];

    if (f->state != OPENED)
        ccp_flags_set(unit, 1, 0);

    /*
     * Find out which compressors the kernel supports before
     * deciding whether to open in silent mode.
     */
    ccp_resetci(f);
    if (!ANY_COMPRESS(ccp_gotoptions[unit]))
        f->flags |= OPT_SILENT;

    fsm_open(f);
}

/*
 * ccp_close - Terminate CCP.
 */
static void
ccp_close(unit, reason)
    int unit;
    char *reason;
{
    ccp_flags_set(unit, 0, 0);
    fsm_close(&ccp_fsm[unit], reason);
}

/*
 * ccp_lowerup - we may now transmit CCP packets.
 */
static void
ccp_lowerup(unit)
    int unit;
{
    fsm_lowerup(&ccp_fsm[unit]);
}

/*
 * ccp_lowerdown - we may not transmit CCP packets.
 */
static void
ccp_lowerdown(unit)
    int unit;
{
    fsm_lowerdown(&ccp_fsm[unit]);
}

/*
 * ccp_input - process a received CCP packet.
 */
static void
ccp_input(unit, p, len)
    int unit;
    u_char *p;
    int len;
{
    fsm *f = &ccp_fsm[unit];
    int oldstate;

    /*
     * Check for a terminate-request so we can print a message.
     */
    oldstate = f->state;
    fsm_input(f, p, len);
    if (oldstate == OPENED && p[0] == TERMREQ && f->state != OPENED) {
        notice("Compression disabled by peer.");
#ifdef MPPE
        if (ccp_gotoptions[unit].mppe) {
            error("MPPE disabled, closing LCP");
            lcp_close(unit, "MPPE disabled by peer");
        }
#endif
    }

    /*
     * If we get a terminate-ack and we're not asking for compression,
     * close CCP.
     */
    if (oldstate == REQSENT && p[0] == TERMACK
        && !ANY_COMPRESS(ccp_gotoptions[unit]))
        ccp_close(unit, "No compression negotiated");
}

/*
 * Handle a CCP-specific code.
 */
static int
ccp_extcode(f, code, id, p, len)
    fsm *f;
    int code, id;
    u_char *p;
    int len;
{
    switch (code) {
    case CCP_RESETREQ:
        if (f->state != OPENED)
            break;
        /* send a reset-ack, which the transmitter will see and
           reset its compression state. */
        fsm_sdata(f, CCP_RESETACK, id, NULL, 0);
        break;

    case CCP_RESETACK:
        if (ccp_localstate[f->unit] & RACK_PENDING && id == f->reqid) {
            ccp_localstate[f->unit] &= ~(RACK_PENDING | RREQ_REPEAT);
            UNTIMEOUT(ccp_rack_timeout, f);
        }
        break;

    default:
        return 0;
    }

    return 1;
}

/*
 * ccp_protrej - peer doesn't talk CCP.
 */
static void
ccp_protrej(unit)
    int unit;
{
    ccp_flags_set(unit, 0, 0);
    fsm_lowerdown(&ccp_fsm[unit]);

#ifdef MPPE
    if (ccp_gotoptions[unit].mppe) {
        error("MPPE required but peer negotiation failed");
        lcp_close(unit, "MPPE required but peer negotiation failed");
    }
#endif

}

/*
 * ccp_resetci - initialize at start of negotiation.
 */
static void
ccp_resetci(f)
    fsm *f;
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    u_char opt_buf[CCP_MAX_OPTION_LENGTH];

    *go = ccp_wantoptions[f->unit];
    all_rejected[f->unit] = 0;

#ifdef MPPE
    if (go->mppe) {
        ccp_options *ao = &ccp_allowoptions[f->unit];
        int auth_mschap_bits = auth_done[f->unit];
        int numbits;

        /*
         * Start with a basic sanity check: mschap[v2] auth must be in
         * exactly one direction.  RFC 3079 says that the keys are
         * 'derived from the credentials of the peer that initiated the call',
         * however the PPP protocol doesn't have such a concept, and pppd
         * cannot get this info externally.  Instead we do the best we can.
         * NB: If MPPE is required, all other compression opts are invalid.
         *     So, we return right away if we can't do it.
         */

        /* Leave only the mschap auth bits set */
        auth_mschap_bits &= (CHAP_MS_WITHPEER  | CHAP_MS_PEER |
                             CHAP_MS2_WITHPEER | CHAP_MS2_PEER);
        /* Count the mschap auths */
        auth_mschap_bits >>= CHAP_MS_SHIFT;
        numbits = 0;
        do {
            numbits += auth_mschap_bits & 1;
            auth_mschap_bits >>= 1;
        } while (auth_mschap_bits);
        if (numbits > 1) {
            error("MPPE required, but auth done in both directions.");
            lcp_close(f->unit, "MPPE required but not available");
            return;
        }
        if (!numbits) {
            error("MPPE required, but MS-CHAP[v2] auth not performed.");
            lcp_close(f->unit, "MPPE required but not available");
            return;
        }

        /* A plugin (eg radius) may not have obtained key material. */
        if (!mppe_keys_set) {
            error("MPPE required, but keys are not available.  "
                  "Possible plugin problem?");
            lcp_close(f->unit, "MPPE required but not available");
            return;
        }

        /* LM auth not supported for MPPE */
        if (auth_done[f->unit] & (CHAP_MS_WITHPEER | CHAP_MS_PEER)) {
            /* This might be noise */
            if (go->mppe & MPPE_OPT_40) {
                notice("Disabling 40-bit MPPE; MS-CHAP LM not supported");
                go->mppe &= ~MPPE_OPT_40;
                ccp_wantoptions[f->unit].mppe &= ~MPPE_OPT_40;
            }
        }

        /* Last check: can we actually negotiate something? */
        if (!(go->mppe & (MPPE_OPT_40 | MPPE_OPT_128))) {
            /* Could be misconfig, could be 40-bit disabled above. */
            error("MPPE required, but both 40-bit and 128-bit disabled.");
            lcp_close(f->unit, "MPPE required but not available");
            return;
        }

        /* sync options */
        ao->mppe = go->mppe;
        /* MPPE is not compatible with other compression types */
        ao->bsd_compress = go->bsd_compress = 0;
        ao->predictor_1  = go->predictor_1  = 0;
        ao->predictor_2  = go->predictor_2  = 0;
        ao->deflate      = go->deflate      = 0;
    }
#endif /* MPPE */

    /*
     * Check whether the kernel knows about the various
     * compression methods we might request.
     */
#ifdef MPPE
    if (go->mppe) {
        opt_buf[0] = CI_MPPE;
        opt_buf[1] = CILEN_MPPE;
        MPPE_OPTS_TO_CI(go->mppe, &opt_buf[2]);
        /* Key material unimportant here. */
        if (ccp_test(f->unit, opt_buf, CILEN_MPPE + MPPE_MAX_KEY_LEN, 0) <= 0) {
            error("MPPE required, but kernel has no support.");
            lcp_close(f->unit, "MPPE required but not available");
        }
    }
#endif
    if (go->bsd_compress) {
        opt_buf[0] = CI_BSD_COMPRESS;
        opt_buf[1] = CILEN_BSD_COMPRESS;
        opt_buf[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION, BSD_MIN_BITS);
        if (ccp_test(f->unit, opt_buf, CILEN_BSD_COMPRESS, 0) <= 0)
            go->bsd_compress = 0;
    }
    if (go->deflate) {
        if (go->deflate_correct) {
            opt_buf[0] = CI_DEFLATE;
            opt_buf[1] = CILEN_DEFLATE;
            opt_buf[2] = DEFLATE_MAKE_OPT(DEFLATE_MIN_WORKS);
            opt_buf[3] = DEFLATE_CHK_SEQUENCE;
            if (ccp_test(f->unit, opt_buf, CILEN_DEFLATE, 0) <= 0)
                go->deflate_correct = 0;
        }
        if (go->deflate_draft) {
            opt_buf[0] = CI_DEFLATE_DRAFT;
            opt_buf[1] = CILEN_DEFLATE;
            opt_buf[2] = DEFLATE_MAKE_OPT(DEFLATE_MIN_WORKS);
            opt_buf[3] = DEFLATE_CHK_SEQUENCE;
            if (ccp_test(f->unit, opt_buf, CILEN_DEFLATE, 0) <= 0)
                go->deflate_draft = 0;
        }
        if (!go->deflate_correct && !go->deflate_draft)
            go->deflate = 0;
    }
    if (go->predictor_1) {
        opt_buf[0] = CI_PREDICTOR_1;
        opt_buf[1] = CILEN_PREDICTOR_1;
        if (ccp_test(f->unit, opt_buf, CILEN_PREDICTOR_1, 0) <= 0)
            go->predictor_1 = 0;
    }
    if (go->predictor_2) {
        opt_buf[0] = CI_PREDICTOR_2;
        opt_buf[1] = CILEN_PREDICTOR_2;
        if (ccp_test(f->unit, opt_buf, CILEN_PREDICTOR_2, 0) <= 0)
            go->predictor_2 = 0;
    }
}

/*
 * ccp_cilen - Return total length of our configuration info.
 */
static int
ccp_cilen(f)
    fsm *f;
{
    ccp_options *go = &ccp_gotoptions[f->unit];

    return (go->bsd_compress? CILEN_BSD_COMPRESS: 0)
        + (go->deflate? CILEN_DEFLATE: 0)
        + (go->predictor_1? CILEN_PREDICTOR_1: 0)
        + (go->predictor_2? CILEN_PREDICTOR_2: 0)
        + (go->mppe? CILEN_MPPE: 0);
}

/*
 * ccp_addci - put our requests in a packet.
 */
static void
ccp_addci(f, p, lenp)
    fsm *f;
    u_char *p;
    int *lenp;
{
    int res;
    ccp_options *go = &ccp_gotoptions[f->unit];
    u_char *p0 = p;

    /*
     * Add the compression types that we can receive, in decreasing
     * preference order.  Get the kernel to allocate the first one
     * in case it gets Acked.
     */
#ifdef MPPE
    if (go->mppe) {
        u_char opt_buf[CILEN_MPPE + MPPE_MAX_KEY_LEN];

        p[0] = opt_buf[0] = CI_MPPE;
        p[1] = opt_buf[1] = CILEN_MPPE;
        MPPE_OPTS_TO_CI(go->mppe, &p[2]);
        MPPE_OPTS_TO_CI(go->mppe, &opt_buf[2]);
        BCOPY(mppe_recv_key, &opt_buf[CILEN_MPPE], MPPE_MAX_KEY_LEN);
        res = ccp_test(f->unit, opt_buf, CILEN_MPPE + MPPE_MAX_KEY_LEN, 0);
        if (res > 0)
            p += CILEN_MPPE;
        else
            /* This shouldn't happen, we've already tested it! */
            lcp_close(f->unit, "MPPE required but not available in kernel");
    }
#endif
    if (go->deflate) {
        p[0] = go->deflate_correct? CI_DEFLATE: CI_DEFLATE_DRAFT;
        p[1] = CILEN_DEFLATE;
        p[2] = DEFLATE_MAKE_OPT(go->deflate_size);
        p[3] = DEFLATE_CHK_SEQUENCE;
        if (p != p0) {
            p += CILEN_DEFLATE;
        } else {
            for (;;) {
                if (go->deflate_size < DEFLATE_MIN_WORKS) {
                    go->deflate = 0;
                    break;
                }
                res = ccp_test(f->unit, p, CILEN_DEFLATE, 0);
                if (res > 0) {
                    p += CILEN_DEFLATE;
                    break;
                } else if (res < 0) {
                    go->deflate = 0;
                    break;
                }
                --go->deflate_size;
                p[2] = DEFLATE_MAKE_OPT(go->deflate_size);
            }
        }
        if (p != p0 && go->deflate_correct && go->deflate_draft) {
            p[0] = CI_DEFLATE_DRAFT;
            p[1] = CILEN_DEFLATE;
            p[2] = p[2 - CILEN_DEFLATE];
            p[3] = DEFLATE_CHK_SEQUENCE;
            p += CILEN_DEFLATE;
        }
    }
    if (go->bsd_compress) {
        p[0] = CI_BSD_COMPRESS;
        p[1] = CILEN_BSD_COMPRESS;
        p[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION, go->bsd_bits);
        if (p != p0) {
            p += CILEN_BSD_COMPRESS;    /* not the first option */
        } else {
            for (;;) {
                if (go->bsd_bits < BSD_MIN_BITS) {
                    go->bsd_compress = 0;
                    break;
                }
                res = ccp_test(f->unit, p, CILEN_BSD_COMPRESS, 0);
                if (res > 0) {
                    p += CILEN_BSD_COMPRESS;
                    break;
                } else if (res < 0) {
                    go->bsd_compress = 0;
                    break;
                }
                --go->bsd_bits;
                p[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION, go->bsd_bits);
            }
        }
    }
    /* XXX Should Predictor 2 be preferable to Predictor 1? */
    if (go->predictor_1) {
        p[0] = CI_PREDICTOR_1;
        p[1] = CILEN_PREDICTOR_1;
        if (p == p0 && ccp_test(f->unit, p, CILEN_PREDICTOR_1, 0) <= 0) {
            go->predictor_1 = 0;
        } else {
            p += CILEN_PREDICTOR_1;
        }
    }
    if (go->predictor_2) {
        p[0] = CI_PREDICTOR_2;
        p[1] = CILEN_PREDICTOR_2;
        if (p == p0 && ccp_test(f->unit, p, CILEN_PREDICTOR_2, 0) <= 0) {
            go->predictor_2 = 0;
        } else {
            p += CILEN_PREDICTOR_2;
        }
    }

    go->method = (p > p0)? p0[0]: -1;

    *lenp = p - p0;
}

/*
 * ccp_ackci - process a received configure-ack, and return
 * 1 iff the packet was OK.
 */
static int
ccp_ackci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    u_char *p0 = p;

#ifdef MPPE
    if (go->mppe) {
        u_char opt_buf[CILEN_MPPE];

        opt_buf[0] = CI_MPPE;
        opt_buf[1] = CILEN_MPPE;
        MPPE_OPTS_TO_CI(go->mppe, &opt_buf[2]);
        if (len < CILEN_MPPE || memcmp(opt_buf, p, CILEN_MPPE))
            return 0;
        p += CILEN_MPPE;
        len -= CILEN_MPPE;
        /* XXX Cope with first/fast ack */
        if (len == 0)
            return 1;
    }
#endif
    if (go->deflate) {
        if (len < CILEN_DEFLATE
            || p[0] != (go->deflate_correct? CI_DEFLATE: CI_DEFLATE_DRAFT)
            || p[1] != CILEN_DEFLATE
            || p[2] != DEFLATE_MAKE_OPT(go->deflate_size)
            || p[3] != DEFLATE_CHK_SEQUENCE)
            return 0;
        p += CILEN_DEFLATE;
        len -= CILEN_DEFLATE;
        /* XXX Cope with first/fast ack */
        if (len == 0)
            return 1;
        if (go->deflate_correct && go->deflate_draft) {
            if (len < CILEN_DEFLATE
                || p[0] != CI_DEFLATE_DRAFT
                || p[1] != CILEN_DEFLATE
                || p[2] != DEFLATE_MAKE_OPT(go->deflate_size)
                || p[3] != DEFLATE_CHK_SEQUENCE)
                return 0;
            p += CILEN_DEFLATE;
            len -= CILEN_DEFLATE;
        }
    }
    if (go->bsd_compress) {
        if (len < CILEN_BSD_COMPRESS
            || p[0] != CI_BSD_COMPRESS || p[1] != CILEN_BSD_COMPRESS
            || p[2] != BSD_MAKE_OPT(BSD_CURRENT_VERSION, go->bsd_bits))
            return 0;
        p += CILEN_BSD_COMPRESS;
        len -= CILEN_BSD_COMPRESS;
        /* XXX Cope with first/fast ack */
        if (p == p0 && len == 0)
            return 1;
    }
    if (go->predictor_1) {
        if (len < CILEN_PREDICTOR_1
            || p[0] != CI_PREDICTOR_1 || p[1] != CILEN_PREDICTOR_1)
            return 0;
        p += CILEN_PREDICTOR_1;
        len -= CILEN_PREDICTOR_1;
        /* XXX Cope with first/fast ack */
        if (p == p0 && len == 0)
            return 1;
    }
    if (go->predictor_2) {
        if (len < CILEN_PREDICTOR_2
            || p[0] != CI_PREDICTOR_2 || p[1] != CILEN_PREDICTOR_2)
            return 0;
        p += CILEN_PREDICTOR_2;
        len -= CILEN_PREDICTOR_2;
        /* XXX Cope with first/fast ack */
        if (p == p0 && len == 0)
            return 1;
    }

    if (len != 0)
        return 0;
    return 1;
}

/*
 * ccp_nakci - process received configure-nak.
 * Returns 1 iff the nak was OK.
 */
static int
ccp_nakci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    ccp_options no;             /* options we've seen already */
    ccp_options try;            /* options to ask for next time */

    memset(&no, 0, sizeof(no));
    try = *go;

#ifdef MPPE
    if (go->mppe && len >= CILEN_MPPE
        && p[0] == CI_MPPE && p[1] == CILEN_MPPE) {
        no.mppe = 1;
        /*
         * Peer wants us to use a different strength or other setting.
         * Fail if we aren't willing to use his suggestion.
         */
        MPPE_CI_TO_OPTS(&p[2], try.mppe);
        if ((try.mppe & MPPE_OPT_STATEFUL) && refuse_mppe_stateful) {
            error("Refusing MPPE stateful mode offered by peer");
            try.mppe = 0;
        } else if (((go->mppe | MPPE_OPT_STATEFUL) & try.mppe) != try.mppe) {
            /* Peer must have set options we didn't request (suggest) */
            try.mppe = 0;
        }

        if (!try.mppe) {
            error("MPPE required but peer negotiation failed");
            lcp_close(f->unit, "MPPE required but peer negotiation failed");
        }
    }
#endif /* MPPE */
    if (go->deflate && len >= CILEN_DEFLATE
        && p[0] == (go->deflate_correct? CI_DEFLATE: CI_DEFLATE_DRAFT)
        && p[1] == CILEN_DEFLATE) {
        no.deflate = 1;
        /*
         * Peer wants us to use a different code size or something.
         * Stop asking for Deflate if we don't understand his suggestion.
         */
        if (DEFLATE_METHOD(p[2]) != DEFLATE_METHOD_VAL
            || DEFLATE_SIZE(p[2]) < DEFLATE_MIN_WORKS
            || p[3] != DEFLATE_CHK_SEQUENCE)
            try.deflate = 0;
        else if (DEFLATE_SIZE(p[2]) < go->deflate_size)
            try.deflate_size = DEFLATE_SIZE(p[2]);
        p += CILEN_DEFLATE;
        len -= CILEN_DEFLATE;
        if (go->deflate_correct && go->deflate_draft
            && len >= CILEN_DEFLATE && p[0] == CI_DEFLATE_DRAFT
            && p[1] == CILEN_DEFLATE) {
            p += CILEN_DEFLATE;
            len -= CILEN_DEFLATE;
        }
    }

    if (go->bsd_compress && len >= CILEN_BSD_COMPRESS
        && p[0] == CI_BSD_COMPRESS && p[1] == CILEN_BSD_COMPRESS) {
        no.bsd_compress = 1;
        /*
         * Peer wants us to use a different number of bits
         * or a different version.
         */
        if (BSD_VERSION(p[2]) != BSD_CURRENT_VERSION)
            try.bsd_compress = 0;
        else if (BSD_NBITS(p[2]) < go->bsd_bits)
            try.bsd_bits = BSD_NBITS(p[2]);
        p += CILEN_BSD_COMPRESS;
        len -= CILEN_BSD_COMPRESS;
    }

    /*
     * Predictor-1 and 2 have no options, so they can't be Naked.
     *
     * There may be remaining options but we ignore them.
     */

    if (f->state != OPENED)
        *go = try;
    return 1;
}

/*
 * ccp_rejci - reject some of our suggested compression methods.
 */
static int
ccp_rejci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    ccp_options try;            /* options to request next time */

    try = *go;

    /*
     * Cope with empty configure-rejects by ceasing to send
     * configure-requests.
     */
    if (len == 0 && all_rejected[f->unit])
        return -1;

#ifdef MPPE
    if (go->mppe && len >= CILEN_MPPE
        && p[0] == CI_MPPE && p[1] == CILEN_MPPE) {
        error("MPPE required but peer refused");
        lcp_close(f->unit, "MPPE required but peer refused");
        p += CILEN_MPPE;
        len -= CILEN_MPPE;
    }
#endif
    if (go->deflate_correct && len >= CILEN_DEFLATE
        && p[0] == CI_DEFLATE && p[1] == CILEN_DEFLATE) {
        if (p[2] != DEFLATE_MAKE_OPT(go->deflate_size)
            || p[3] != DEFLATE_CHK_SEQUENCE)
            return 0;           /* Rej is bad */
        try.deflate_correct = 0;
        p += CILEN_DEFLATE;
        len -= CILEN_DEFLATE;
    }
    if (go->deflate_draft && len >= CILEN_DEFLATE
        && p[0] == CI_DEFLATE_DRAFT && p[1] == CILEN_DEFLATE) {
        if (p[2] != DEFLATE_MAKE_OPT(go->deflate_size)
            || p[3] != DEFLATE_CHK_SEQUENCE)
            return 0;           /* Rej is bad */
        try.deflate_draft = 0;
        p += CILEN_DEFLATE;
        len -= CILEN_DEFLATE;
    }
    if (!try.deflate_correct && !try.deflate_draft)
        try.deflate = 0;
    if (go->bsd_compress && len >= CILEN_BSD_COMPRESS
        && p[0] == CI_BSD_COMPRESS && p[1] == CILEN_BSD_COMPRESS) {
        if (p[2] != BSD_MAKE_OPT(BSD_CURRENT_VERSION, go->bsd_bits))
            return 0;
        try.bsd_compress = 0;
        p += CILEN_BSD_COMPRESS;
        len -= CILEN_BSD_COMPRESS;
    }
    if (go->predictor_1 && len >= CILEN_PREDICTOR_1
        && p[0] == CI_PREDICTOR_1 && p[1] == CILEN_PREDICTOR_1) {
        try.predictor_1 = 0;
        p += CILEN_PREDICTOR_1;
        len -= CILEN_PREDICTOR_1;
    }
    if (go->predictor_2 && len >= CILEN_PREDICTOR_2
        && p[0] == CI_PREDICTOR_2 && p[1] == CILEN_PREDICTOR_2) {
        try.predictor_2 = 0;
        p += CILEN_PREDICTOR_2;
        len -= CILEN_PREDICTOR_2;
    }

    if (len != 0)
        return 0;

    if (f->state != OPENED)
        *go = try;

    return 1;
}

/*
 * ccp_reqci - processed a received configure-request.
 * Returns CONFACK, CONFNAK or CONFREJ and the packet modified
 * appropriately.
 */
static int
ccp_reqci(f, p, lenp, dont_nak)
    fsm *f;
    u_char *p;
    int *lenp;
    int dont_nak;
{
    int ret, newret, res;
    u_char *p0, *retp;
    int len, clen, type, nb;
    ccp_options *ho = &ccp_hisoptions[f->unit];
    ccp_options *ao = &ccp_allowoptions[f->unit];
#ifdef MPPE
    bool rej_for_ci_mppe = 1;   /* Are we rejecting based on a bad/missing */
                                /* CI_MPPE, or due to other options?       */
#endif

    ret = CONFACK;
    retp = p0 = p;
    len = *lenp;

    memset(ho, 0, sizeof(ccp_options));
    ho->method = (len > 0)? p[0]: -1;

    while (len > 0) {
        newret = CONFACK;
        if (len < 2 || p[1] < 2 || p[1] > len) {
            /* length is bad */
            clen = len;
            newret = CONFREJ;

        } else {
            type = p[0];
            clen = p[1];

            switch (type) {
#ifdef MPPE
            case CI_MPPE:
                if (!ao->mppe || clen != CILEN_MPPE) {
                    newret = CONFREJ;
                    break;
                }
                MPPE_CI_TO_OPTS(&p[2], ho->mppe);

                /* Nak if anything unsupported or unknown are set. */
                if (ho->mppe & MPPE_OPT_UNSUPPORTED) {
                    newret = CONFNAK;
                    ho->mppe &= ~MPPE_OPT_UNSUPPORTED;
                }
                if (ho->mppe & MPPE_OPT_UNKNOWN) {
                    newret = CONFNAK;
                    ho->mppe &= ~MPPE_OPT_UNKNOWN;
                }

                /* Check state opt */
                if (ho->mppe & MPPE_OPT_STATEFUL) {
                    /*
                     * We can Nak and request stateless, but it's a
                     * lot easier to just assume the peer will request
                     * it if he can do it; stateful mode is bad over
                     * the Internet -- which is where we expect MPPE.
                     */
                   if (refuse_mppe_stateful) {
                        error("Refusing MPPE stateful mode offered by peer");
                        newret = CONFREJ;
                        break;
                    }
                }

                /* Find out which of {S,L} are set. */
                if ((ho->mppe & MPPE_OPT_128)
                     && (ho->mppe & MPPE_OPT_40)) {
                    /* Both are set, negotiate the strongest. */
                    newret = CONFNAK;
                    if (ao->mppe & MPPE_OPT_128)
                        ho->mppe &= ~MPPE_OPT_40;
                    else if (ao->mppe & MPPE_OPT_40)
                        ho->mppe &= ~MPPE_OPT_128;
                    else {
                        newret = CONFREJ;
                        break;
                    }
                } else if (ho->mppe & MPPE_OPT_128) {
                    if (!(ao->mppe & MPPE_OPT_128)) {
                        newret = CONFREJ;
                        break;
                    }
                } else if (ho->mppe & MPPE_OPT_40) {
                    if (!(ao->mppe & MPPE_OPT_40)) {
                        newret = CONFREJ;
                        break;
                    }
                } else {
                    /* Neither are set. */
                    newret = CONFREJ;
                    break;
                }

                /* rebuild the opts */
                MPPE_OPTS_TO_CI(ho->mppe, &p[2]);
                if (newret == CONFACK) {
                    u_char opt_buf[CILEN_MPPE + MPPE_MAX_KEY_LEN];
                    int mtu;

                    BCOPY(p, opt_buf, CILEN_MPPE);
                    BCOPY(mppe_send_key, &opt_buf[CILEN_MPPE],
                          MPPE_MAX_KEY_LEN);
                    if (ccp_test(f->unit, opt_buf,
                                 CILEN_MPPE + MPPE_MAX_KEY_LEN, 1) <= 0) {
                        /* This shouldn't happen, we've already tested it! */
                        error("MPPE required, but kernel has no support.");
                        lcp_close(f->unit, "MPPE required but not available");
                        newret = CONFREJ;
                        break;
                    }
                    /*
                     * We need to decrease the interface MTU by MPPE_PAD
                     * because MPPE frames **grow**.  The kernel [must]
                     * allocate MPPE_PAD extra bytes in xmit buffers.
                     */
                    mtu = netif_get_mtu(f->unit);
                    if (mtu)
                        netif_set_mtu(f->unit, mtu - MPPE_PAD);
                    else
                        newret = CONFREJ;
                }

                /*
                 * We have accepted MPPE or are willing to negotiate
                 * MPPE parameters.  A CONFREJ is due to subsequent
                 * (non-MPPE) processing.
                 */
                rej_for_ci_mppe = 0;
                break;
#endif /* MPPE */
            case CI_DEFLATE:
            case CI_DEFLATE_DRAFT:
                if (!ao->deflate || clen != CILEN_DEFLATE
                    || (!ao->deflate_correct && type == CI_DEFLATE)
                    || (!ao->deflate_draft && type == CI_DEFLATE_DRAFT)) {
                    newret = CONFREJ;
                    break;
                }

                ho->deflate = 1;
                ho->deflate_size = nb = DEFLATE_SIZE(p[2]);
                if (DEFLATE_METHOD(p[2]) != DEFLATE_METHOD_VAL
                    || p[3] != DEFLATE_CHK_SEQUENCE
                    || nb > ao->deflate_size || nb < DEFLATE_MIN_WORKS) {
                    newret = CONFNAK;
                    if (!dont_nak) {
                        p[2] = DEFLATE_MAKE_OPT(ao->deflate_size);
                        p[3] = DEFLATE_CHK_SEQUENCE;
                        /* fall through to test this #bits below */
                    } else
                        break;
                }

                /*
                 * Check whether we can do Deflate with the window
                 * size they want.  If the window is too big, reduce
                 * it until the kernel can cope and nak with that.
                 * We only check this for the first option.
                 */
                if (p == p0) {
                    for (;;) {
                        res = ccp_test(f->unit, p, CILEN_DEFLATE, 1);
                        if (res > 0)
                            break;              /* it's OK now */
                        if (res < 0 || nb == DEFLATE_MIN_WORKS || dont_nak) {
                            newret = CONFREJ;
                            p[2] = DEFLATE_MAKE_OPT(ho->deflate_size);
                            break;
                        }
                        newret = CONFNAK;
                        --nb;
                        p[2] = DEFLATE_MAKE_OPT(nb);
                    }
                }
                break;

            case CI_BSD_COMPRESS:
                if (!ao->bsd_compress || clen != CILEN_BSD_COMPRESS) {
                    newret = CONFREJ;
                    break;
                }

                ho->bsd_compress = 1;
                ho->bsd_bits = nb = BSD_NBITS(p[2]);
                if (BSD_VERSION(p[2]) != BSD_CURRENT_VERSION
                    || nb > ao->bsd_bits || nb < BSD_MIN_BITS) {
                    newret = CONFNAK;
                    if (!dont_nak) {
                        p[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION, ao->bsd_bits);
                        /* fall through to test this #bits below */
                    } else
                        break;
                }

                /*
                 * Check whether we can do BSD-Compress with the code
                 * size they want.  If the code size is too big, reduce
                 * it until the kernel can cope and nak with that.
                 * We only check this for the first option.
                 */
                if (p == p0) {
                    for (;;) {
                        res = ccp_test(f->unit, p, CILEN_BSD_COMPRESS, 1);
                        if (res > 0)
                            break;
                        if (res < 0 || nb == BSD_MIN_BITS || dont_nak) {
                            newret = CONFREJ;
                            p[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION,
                                                ho->bsd_bits);
                            break;
                        }
                        newret = CONFNAK;
                        --nb;
                        p[2] = BSD_MAKE_OPT(BSD_CURRENT_VERSION, nb);
                    }
                }
                break;

            case CI_PREDICTOR_1:
                if (!ao->predictor_1 || clen != CILEN_PREDICTOR_1) {
                    newret = CONFREJ;
                    break;
                }

                ho->predictor_1 = 1;
                if (p == p0
                    && ccp_test(f->unit, p, CILEN_PREDICTOR_1, 1) <= 0) {
                    newret = CONFREJ;
                }
                break;

            case CI_PREDICTOR_2:
                if (!ao->predictor_2 || clen != CILEN_PREDICTOR_2) {
                    newret = CONFREJ;
                    break;
                }

                ho->predictor_2 = 1;
                if (p == p0
                    && ccp_test(f->unit, p, CILEN_PREDICTOR_2, 1) <= 0) {
                    newret = CONFREJ;
                }
                break;

            default:
                newret = CONFREJ;
            }
        }

        if (newret == CONFNAK && dont_nak)
            newret = CONFREJ;
        if (!(newret == CONFACK || (newret == CONFNAK && ret == CONFREJ))) {
            /* we're returning this option */
            if (newret == CONFREJ && ret == CONFNAK)
                retp = p0;
            ret = newret;
            if (p != retp)
                BCOPY(p, retp, clen);
            retp += clen;
        }

        p += clen;
        len -= clen;
    }

    if (ret != CONFACK) {
        if (ret == CONFREJ && *lenp == retp - p0)
            all_rejected[f->unit] = 1;
        else
            *lenp = retp - p0;
    }
#ifdef MPPE
    if (ret == CONFREJ && ao->mppe && rej_for_ci_mppe) {
        error("MPPE required but peer negotiation failed");
        lcp_close(f->unit, "MPPE required but peer negotiation failed");
    }
#endif
    return ret;
}

/*
 * Make a string name for a compression method (or 2).
 */
static char *
method_name(opt, opt2)
    ccp_options *opt, *opt2;
{
    static char result[64];

    if (!ANY_COMPRESS(*opt))
        return "(none)";
    switch (opt->method) {
#ifdef MPPE
    case CI_MPPE:
    {
        char *p = result;
        char *q = result + sizeof(result); /* 1 past result */

        slprintf(p, q - p, "MPPE ");
        p += 5;
        if (opt->mppe & MPPE_OPT_128) {
            slprintf(p, q - p, "128-bit ");
            p += 8;
        }
        if (opt->mppe & MPPE_OPT_40) {
            slprintf(p, q - p, "40-bit ");
            p += 7;
        }
        if (opt->mppe & MPPE_OPT_STATEFUL)
            slprintf(p, q - p, "stateful");
        else
            slprintf(p, q - p, "stateless");

        break;
    }
#endif
    case CI_DEFLATE:
    case CI_DEFLATE_DRAFT:
        if (opt2 != NULL && opt2->deflate_size != opt->deflate_size)
            slprintf(result, sizeof(result), "Deflate%s (%d/%d)",
                     (opt->method == CI_DEFLATE_DRAFT? "(old#)": ""),
                     opt->deflate_size, opt2->deflate_size);
        else
            slprintf(result, sizeof(result), "Deflate%s (%d)",
                     (opt->method == CI_DEFLATE_DRAFT? "(old#)": ""),
                     opt->deflate_size);
        break;
    case CI_BSD_COMPRESS:
        if (opt2 != NULL && opt2->bsd_bits != opt->bsd_bits)
            slprintf(result, sizeof(result), "BSD-Compress (%d/%d)",
                     opt->bsd_bits, opt2->bsd_bits);
        else
            slprintf(result, sizeof(result), "BSD-Compress (%d)",
                     opt->bsd_bits);
        break;
    case CI_PREDICTOR_1:
        return "Predictor 1";
    case CI_PREDICTOR_2:
        return "Predictor 2";
    default:
        slprintf(result, sizeof(result), "Method %d", opt->method);
    }
    return result;
}

/*
 * CCP has come up - inform the kernel driver and log a message.
 */
static void
ccp_up(f)
    fsm *f;
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    ccp_options *ho = &ccp_hisoptions[f->unit];
    char method1[64];

    ccp_flags_set(f->unit, 1, 1);
    if (ANY_COMPRESS(*go)) {
        if (ANY_COMPRESS(*ho)) {
            if (go->method == ho->method) {
                notice("%s compression enabled", method_name(go, ho));
            } else {
                strlcpy(method1, method_name(go, NULL), sizeof(method1));
                notice("%s / %s compression enabled",
                       method1, method_name(ho, NULL));
            }
        } else
            notice("%s receive compression enabled", method_name(go, NULL));
    } else if (ANY_COMPRESS(*ho))
        notice("%s transmit compression enabled", method_name(ho, NULL));
#ifdef MPPE
    if (go->mppe) {
        BZERO(mppe_recv_key, MPPE_MAX_KEY_LEN);
        BZERO(mppe_send_key, MPPE_MAX_KEY_LEN);
        continue_networks(f->unit);             /* Bring up IP et al */
    }
#endif
}

/*
 * CCP has gone down - inform the kernel driver.
 */
static void
ccp_down(f)
    fsm *f;
{
    if (ccp_localstate[f->unit] & RACK_PENDING)
        UNTIMEOUT(ccp_rack_timeout, f);
    ccp_localstate[f->unit] = 0;
    ccp_flags_set(f->unit, 1, 0);
#ifdef MPPE
    if (ccp_gotoptions[f->unit].mppe) {
        ccp_gotoptions[f->unit].mppe = 0;
        if (lcp_fsm[f->unit].state == OPENED) {
            /* If LCP is not already going down, make sure it does. */
            error("MPPE disabled");
            lcp_close(f->unit, "MPPE disabled");
        }
    }
#endif
}

/*
 * Print the contents of a CCP packet.
 */
static char *ccp_codenames[] = {
    "ConfReq", "ConfAck", "ConfNak", "ConfRej",
    "TermReq", "TermAck", "CodeRej",
    NULL, NULL, NULL, NULL, NULL, NULL,
    "ResetReq", "ResetAck",
};

static int
ccp_printpkt(p, plen, printer, arg)
    u_char *p;
    int plen;
    void (*printer) __P((void *, char *, ...));
    void *arg;
{
    u_char *p0, *optend;
    int code, id, len;
    int optlen;

    p0 = p;
    if (plen < HEADERLEN)
        return 0;
    code = p[0];
    id = p[1];
    len = (p[2] << 8) + p[3];
    if (len < HEADERLEN || len > plen)
        return 0;

    if (code >= 1 && code <= sizeof(ccp_codenames) / sizeof(char *)
        && ccp_codenames[code-1] != NULL)
        printer(arg, " %s", ccp_codenames[code-1]);
    else
        printer(arg, " code=0x%x", code);
    printer(arg, " id=0x%x", id);
    len -= HEADERLEN;
    p += HEADERLEN;

    switch (code) {
    case CONFREQ:
    case CONFACK:
    case CONFNAK:
    case CONFREJ:
        /* print list of possible compression methods */
        while (len >= 2) {
            code = p[0];
            optlen = p[1];
            if (optlen < 2 || optlen > len)
                break;
            printer(arg, " <");
            len -= optlen;
            optend = p + optlen;
            switch (code) {
#ifdef MPPE
            case CI_MPPE:
                if (optlen >= CILEN_MPPE) {
                    u_char mppe_opts;

                    MPPE_CI_TO_OPTS(&p[2], mppe_opts);
                    printer(arg, "mppe %s %s %s %s %s %s%s",
                            (p[2] & MPPE_H_BIT)? "+H": "-H",
                            (p[5] & MPPE_M_BIT)? "+M": "-M",
                            (p[5] & MPPE_S_BIT)? "+S": "-S",
                            (p[5] & MPPE_L_BIT)? "+L": "-L",
                            (p[5] & MPPE_D_BIT)? "+D": "-D",
                            (p[5] & MPPE_C_BIT)? "+C": "-C",
                            (mppe_opts & MPPE_OPT_UNKNOWN)? " +U": "");
                    if (mppe_opts & MPPE_OPT_UNKNOWN)
                        printer(arg, " (%.2x %.2x %.2x %.2x)",
                                p[2], p[3], p[4], p[5]);
                    p += CILEN_MPPE;
                }
                break;
#endif
            case CI_DEFLATE:
            case CI_DEFLATE_DRAFT:
                if (optlen >= CILEN_DEFLATE) {
                    printer(arg, "deflate%s %d",
                            (code == CI_DEFLATE_DRAFT? "(old#)": ""),
                            DEFLATE_SIZE(p[2]));
                    if (DEFLATE_METHOD(p[2]) != DEFLATE_METHOD_VAL)
                        printer(arg, " method %d", DEFLATE_METHOD(p[2]));
                    if (p[3] != DEFLATE_CHK_SEQUENCE)
                        printer(arg, " check %d", p[3]);
                    p += CILEN_DEFLATE;
                }
                break;
            case CI_BSD_COMPRESS:
                if (optlen >= CILEN_BSD_COMPRESS) {
                    printer(arg, "bsd v%d %d", BSD_VERSION(p[2]),
                            BSD_NBITS(p[2]));
                    p += CILEN_BSD_COMPRESS;
                }
                break;
            case CI_PREDICTOR_1:
                if (optlen >= CILEN_PREDICTOR_1) {
                    printer(arg, "predictor 1");
                    p += CILEN_PREDICTOR_1;
                }
                break;
            case CI_PREDICTOR_2:
                if (optlen >= CILEN_PREDICTOR_2) {
                    printer(arg, "predictor 2");
                    p += CILEN_PREDICTOR_2;
                }
                break;
            }
            while (p < optend)
                printer(arg, " %.2x", *p++);
            printer(arg, ">");
        }
        break;

    case TERMACK:
    case TERMREQ:
        if (len > 0 && *p >= ' ' && *p < 0x7f) {
            print_string((char *)p, len, printer, arg);
            p += len;
            len = 0;
        }
        break;
    }

    /* dump out the rest of the packet in hex */
    while (--len >= 0)
        printer(arg, " %.2x", *p++);

    return p - p0;
}

/*
 * We have received a packet that the decompressor failed to
 * decompress.  Here we would expect to issue a reset-request, but
 * Motorola has a patent on resetting the compressor as a result of
 * detecting an error in the decompressed data after decompression.
 * (See US patent 5,130,993; international patent publication number
 * WO 91/10289; Australian patent 73296/91.)
 *
 * So we ask the kernel whether the error was detected after
 * decompression; if it was, we take CCP down, thus disabling
 * compression :-(, otherwise we issue the reset-request.
 */
static void
ccp_datainput(unit, pkt, len)
    int unit;
    u_char *pkt;
    int len;
{
    fsm *f;

    f = &ccp_fsm[unit];
    if (f->state == OPENED) {
        if (ccp_fatal_error(unit)) {
            /*
             * Disable compression by taking CCP down.
             */
            error("Lost compression sync: disabling compression");
            ccp_close(unit, "Lost compression sync");
#ifdef MPPE
            /*
             * If we were doing MPPE, we must also take the link down.
             */
            if (ccp_gotoptions[unit].mppe) {
                error("Too many MPPE errors, closing LCP");
                lcp_close(unit, "Too many MPPE errors");
            }
#endif
        } else {
            /*
             * Send a reset-request to reset the peer's compressor.
             * We don't do that if we are still waiting for an
             * acknowledgement to a previous reset-request.
             */
            if (!(ccp_localstate[f->unit] & RACK_PENDING)) {
                fsm_sdata(f, CCP_RESETREQ, f->reqid = ++f->id, NULL, 0);
                TIMEOUT(ccp_rack_timeout, f, RACKTIMEOUT);
                ccp_localstate[f->unit] |= RACK_PENDING;
            } else
                ccp_localstate[f->unit] |= RREQ_REPEAT;
        }
    }
}

/*
 * Timeout waiting for reset-ack.
 */
static void
ccp_rack_timeout(arg)
    void *arg;
{
    fsm *f = arg;

    if (f->state == OPENED && ccp_localstate[f->unit] & RREQ_REPEAT) {
        fsm_sdata(f, CCP_RESETREQ, f->reqid, NULL, 0);
        TIMEOUT(ccp_rack_timeout, f, RACKTIMEOUT);
        ccp_localstate[f->unit] &= ~RREQ_REPEAT;
    } else
        ccp_localstate[f->unit] &= ~RACK_PENDING;
}