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/*

 * demand.c - Support routines for demand-dialling.

 *

 * Copyright (c) 1993 The Australian National 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 the Australian National 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   "demand.c,v 1.3 2002/01/31 21:40:47 joel Exp";

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include <fcntl.h>

#include <netdb.h>

#include <sys/param.h>

#include <sys/types.h>

#include <sys/wait.h>

#include <sys/time.h>

#include <sys/resource.h>

#include <sys/stat.h>

#include <sys/socket.h>

#ifdef PPP_FILTER

#include <net/if.h>

#include <net/bpf.h>

#include <pcap.h>

#endif

#include "pppd.h"

#include "fsm.h"

#include "ipcp.h"

#include "lcp.h"

static const char rcsid[] = RCSID;

char *frame;

int framelen;

int framemax;

int escape_flag;

int flush_flag;

int fcs;

struct packet {

    int length;

    struct packet *next;

    unsigned char data[1];

};

struct packet *pend_q;

struct packet *pend_qtail;

static int active_packet __P((unsigned char *, int));

/*

 * demand_conf - configure the interface for doing dial-on-demand.

 */

void

demand_conf()

{

    int i;

    struct protent *protp;

/*    framemax = lcp_allowoptions[0].mru;

    if (framemax < PPP_MRU) */

        framemax = PPP_MRU;

    framemax += PPP_HDRLEN + PPP_FCSLEN;

    frame = malloc(framemax);

    if (frame == NULL)

        novm("demand frame");

    framelen = 0;

    pend_q = NULL;

    escape_flag = 0;

    flush_flag = 0;

    fcs = PPP_INITFCS;

    ppp_send_config(0, PPP_MRU, (u_int32_t) 0, 0, 0);

    ppp_recv_config(0, PPP_MRU, (u_int32_t) 0, 0, 0);

#ifdef PPP_FILTER

    set_filters(&pass_filter, &active_filter);

#endif

    /*

     * Call the demand_conf procedure for each protocol that's got one.

     */

    for (i = 0; (protp = protocols[i]) != NULL; ++i)

        if (protp->enabled_flag && protp->demand_conf != NULL)

            if (!((*protp->demand_conf)(0)))

                die(1);

}

/*

 * demand_block - set each network protocol to block further packets.

 */

void

demand_block()

{

    int i;

    struct protent *protp;

    for (i = 0; (protp = protocols[i]) != NULL; ++i)

        if (protp->enabled_flag && protp->demand_conf != NULL)

            sifnpmode(0, protp->protocol & ~0x8000, NPMODE_QUEUE);

    get_loop_output();

}

/*

 * demand_discard - set each network protocol to discard packets

 * with an error.

 */

void

demand_discard()

{

    struct packet *pkt, *nextpkt;

    int i;

    struct protent *protp;

    for (i = 0; (protp = protocols[i]) != NULL; ++i)

        if (protp->enabled_flag && protp->demand_conf != NULL)

            sifnpmode(0, protp->protocol & ~0x8000, NPMODE_ERROR);

    get_loop_output();

    /* discard all saved packets */

    for (pkt = pend_q; pkt != NULL; pkt = nextpkt) {

        nextpkt = pkt->next;

        free(pkt);

    }

    pend_q = NULL;

    framelen = 0;

    flush_flag = 0;

    escape_flag = 0;

    fcs = PPP_INITFCS;

}

/*

 * demand_unblock - set each enabled network protocol to pass packets.

 */

void

demand_unblock()

{

    int i;

    struct protent *protp;

    for (i = 0; (protp = protocols[i]) != NULL; ++i)

        if (protp->enabled_flag && protp->demand_conf != NULL)

            sifnpmode(0, protp->protocol & ~0x8000, NPMODE_PASS);

}

/*

 * FCS lookup table as calculated by genfcstab.

 */

static u_short fcstab[256] = {

        0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,

        0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,

        0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,

        0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,

        0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,

        0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,

        0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,

        0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,

        0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,

        0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,

        0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,

        0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,

        0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,

        0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,

        0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,

        0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,

        0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,

        0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,

        0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,

        0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,

        0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,

        0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,

        0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,

        0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,

        0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,

        0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,

        0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,

        0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,

        0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,

        0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,

        0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,

        0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78

};

/*

 * loop_chars - process characters received from the loopback.

 * Calls loop_frame when a complete frame has been accumulated.

 * Return value is 1 if we need to bring up the link, 0 otherwise.

 */

int

loop_chars(p, n)

    unsigned char *p;

    int n;

{

    int c, rv;

    rv = 0;

    for (; n > 0; --n) {

        c = *p++;

        if (c == PPP_FLAG) {

            if (!escape_flag && !flush_flag

                && framelen > 2 && fcs == PPP_GOODFCS) {

                framelen -= 2;

                if (loop_frame(frame, framelen))

                    rv = 1;

            }

            framelen = 0;

            flush_flag = 0;

            escape_flag = 0;

            fcs = PPP_INITFCS;

            continue;

        }

        if (flush_flag)

            continue;

        if (escape_flag) {

            c ^= PPP_TRANS;

            escape_flag = 0;

        } else if (c == PPP_ESCAPE) {

            escape_flag = 1;

            continue;

        }

        if (framelen >= framemax) {

            flush_flag = 1;

            continue;

        }

        frame[framelen++] = c;

        fcs = PPP_FCS(fcs, c);

    }

    return rv;

}

/*

 * loop_frame - given a frame obtained from the loopback,

 * decide whether to bring up the link or not, and, if we want

 * to transmit this frame later, put it on the pending queue.

 * Return value is 1 if we need to bring up the link, 0 otherwise.

 * We assume that the kernel driver has already applied the

 * pass_filter, so we won't get packets it rejected.

 * We apply the active_filter to see if we want this packet to

 * bring up the link.

 */

int

loop_frame(frame, len)

    unsigned char *frame;

    int len;

{

    struct packet *pkt;

    /* dbglog("from loop: %P", frame, len); */

    if (len < PPP_HDRLEN)

        return 0;

    if ((PPP_PROTOCOL(frame) & 0x8000) != 0)

        return 0;                /* shouldn't get any of these anyway */

    if (!active_packet(frame, len))

        return 0;

    pkt = (struct packet *) malloc(sizeof(struct packet) + len);

    if (pkt != NULL) {

        pkt->length = len;

        pkt->next = NULL;

        memcpy(pkt->data, frame, len);

        if (pend_q == NULL)

            pend_q = pkt;

        else

            pend_qtail->next = pkt;

        pend_qtail = pkt;

    }

    return 1;

}

/*

 * demand_rexmit - Resend all those frames which we got via the

 * loopback, now that the real serial link is up.

 */

void

demand_rexmit(proto)

    int proto;

{

    struct packet *pkt, *prev, *nextpkt;

    prev = NULL;

    pkt = pend_q;

    pend_q = NULL;

    for (; pkt != NULL; pkt = nextpkt) {

        nextpkt = pkt->next;

        if (PPP_PROTOCOL(pkt->data) == proto) {

            output(0, pkt->data, pkt->length);

            free(pkt);

        } else {

            if (prev == NULL)

                pend_q = pkt;

            else

                prev->next = pkt;

            prev = pkt;

        }

    }

    pend_qtail = prev;

    if (prev != NULL)

        prev->next = NULL;

}

/*

 * Scan a packet to decide whether it is an "active" packet,

 * that is, whether it is worth bringing up the link for.

 */

static int

active_packet(p, len)

    unsigned char *p;

    int len;

{

    int proto, i;

    struct protent *protp;

    if (len < PPP_HDRLEN)

        return 0;

    proto = PPP_PROTOCOL(p);

#ifdef PPP_FILTER

    if (active_filter.bf_len != 0

        && bpf_filter(active_filter.bf_insns, frame, len, len) == 0)

        return 0;

#endif

    for (i = 0; (protp = protocols[i]) != NULL; ++i) {

        if (protp->protocol < 0xC000 && (protp->protocol & ~0x8000) == proto) {

            if (!protp->enabled_flag)

                return 0;

            if (protp->active_pkt == NULL)

                return 1;

            return (*protp->active_pkt)(p, len);

        }

    }

    return 0;                    /* not a supported protocol !!?? */

}