/*      $OpenBSD: ccp.c,v 1.14 2024/08/09 05:16:13 deraadt Exp $        */

/*
 * ccp.c - PPP Compression Control Protocol.
 *
 * Copyright (c) 1989-2002 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.
 */

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

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

/*
 * Protocol entry points from main code.
 */
static void ccp_init(int unit);
static void ccp_open(int unit);
static void ccp_close(int unit, char *);
static void ccp_lowerup(int unit);
static void ccp_lowerdown(int);
static void ccp_input(int unit, u_char *pkt, int len);
static void ccp_protrej(int unit);
static int  ccp_printpkt(u_char *pkt, int len,
    void (*printer)(void *, char *, ...), void *arg);
static void ccp_datainput(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",
    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(fsm *);
static int  ccp_cilen(fsm *);
static void ccp_addci(fsm *, u_char *, int *);
static int  ccp_ackci(fsm *, u_char *, int);
static int  ccp_nakci(fsm *, u_char *, int);
static int  ccp_rejci(fsm *, u_char *, int);
static int  ccp_reqci(fsm *, u_char *, int *, int);
static void ccp_up(fsm *);
static void ccp_down(fsm *);
static int  ccp_extcode(fsm *, int, int, u_char *, int);
static void ccp_rack_timeout(void *);
static char *method_name(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)

/*
 * 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 */

/*
 * ccp_init - initialize CCP.
 */
static void
ccp_init(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(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(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(int unit)
{
    fsm_lowerup(&ccp_fsm[unit]);
}

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

/*
 * ccp_input - process a received CCP packet.
 */
static void
ccp_input(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)
        syslog(LOG_NOTICE, "Compression disabled by peer.");

    /*
     * 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(fsm *f, int code, int 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(int unit)
{
    ccp_flags_set(unit, 0, 0);
    fsm_lowerdown(&ccp_fsm[unit]);
}

/*
 * ccp_resetci - initialize at start of negotiation.
 */
static void
ccp_resetci(fsm *f)
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    u_char opt_buf[16];

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

    /*
     * Check whether the kernel knows about the various
     * compression methods we might request.
     */
    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_SIZE);
            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_SIZE);
            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(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);
}

/*
 * ccp_addci - put our requests in a packet.
 */
static void
ccp_addci(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.
     */
    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;
        for (;;) {
            res = ccp_test(f->unit, p, CILEN_DEFLATE, 0);
            if (res > 0) {
                p += CILEN_DEFLATE;
                break;
            }
            if (res < 0 || go->deflate_size <= DEFLATE_MIN_SIZE) {
                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 (;;) {
                res = ccp_test(f->unit, p, CILEN_BSD_COMPRESS, 0);
                if (res > 0) {
                    p += CILEN_BSD_COMPRESS;
                    break;
                }
                if (res < 0 || go->bsd_bits <= BSD_MIN_BITS) {
                    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(fsm *f, u_char *p, int len)
{
    ccp_options *go = &ccp_gotoptions[f->unit];
    u_char *p0 = p;

    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(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;

    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_SIZE
            || 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.
     *
     * XXX What should we do with any remaining options?
     */

    if (len != 0)
        return 0;

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

/*
 * ccp_rejci - reject some of our suggested compression methods.
 */
static int
ccp_rejci(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;

    if (go->deflate && len >= CILEN_DEFLATE
        && p[0] == (go->deflate_correct? CI_DEFLATE: 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 */
        if (go->deflate_correct)
            try.deflate_correct = 0;
        else
            try.deflate_draft = 0;
        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) {
            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(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];

    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) {
            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_SIZE) {
                    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_SIZE || 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;
    }
    return ret;
}

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

    if (!ANY_COMPRESS(*opt))
        return "(none)";
    switch (opt->method) {
    case CI_DEFLATE:
    case CI_DEFLATE_DRAFT:
        if (opt2 != NULL && opt2->deflate_size != opt->deflate_size)
            snprintf(result, sizeof result, "Deflate%s (%d/%d)",
                    (opt->method == CI_DEFLATE_DRAFT? "(old#)": ""),
                    opt->deflate_size, opt2->deflate_size);
        else
            snprintf(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)
            snprintf(result, sizeof result,
                    "BSD-Compress (%d/%d)", opt->bsd_bits,
                    opt2->bsd_bits);
        else
            snprintf(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:
        snprintf(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(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) {
                syslog(LOG_NOTICE, "%s compression enabled",
                       method_name(go, ho));
            } else {
                strncpy(method1, method_name(go, NULL), sizeof method1);
                syslog(LOG_NOTICE, "%s / %s compression enabled",
                       method1, method_name(ho, NULL));
            }
        } else
            syslog(LOG_NOTICE, "%s receive compression enabled",
                   method_name(go, NULL));
    } else if (ANY_COMPRESS(*ho))
        syslog(LOG_NOTICE, "%s transmit compression enabled",
               method_name(ho, NULL));
}

/*
 * CCP has gone down - inform the kernel driver.
 */
static void
ccp_down(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);
}

/*
 * 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(u_char *p, int plen, void (*printer)(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) {
            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(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(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.
             */
            syslog(LOG_ERR, "Lost compression sync: disabling compression");
            ccp_close(unit, "Lost compression sync");
        } 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(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;
}