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Replace <sys/param.h> with <limits.h> and other less dirty headers where
possible.  Annotate <sys/param.h> lines with their current reasons.  Switch
to PATH_MAX, NGROUPS_MAX, HOST_NAME_MAX+1, LOGIN_NAME_MAX, etc.  Change
MIN() and MAX() to local definitions of MINIMUM() and MAXIMUM() where
sensible to avoid pulling in the pollution.  These are the files confirmed
through binary verification.
ok guenther, millert, doug (helped with the verification protocol)

/*	$OpenBSD: demand.c,v 1.11 2015/01/16 06:40:19 deraadt Exp $	*/

/*
 * demand.c - Support routines for demand-dialling.
 *
 * 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 <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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <syslog.h>

#include "pppd.h"
#include "fsm.h"
#include "ipcp.h"
#include "lcp.h"

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(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_drop - set each network protocol to discard packets
 * without an error.
 */
void
demand_drop()
{
    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_DROP);
    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;

    /* log_packet(frame, len, "from loop: ", LOG_DEBUG); */
    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 !!?? */
}