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libpcap.c

/* $Id: libpcap.c 767 2004-10-06 12:48:49Z aturner $ */

/*
 * Copyright (c) 2001-2004 Aaron Turner, Matt Bing.
 * 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. Neither the names of the copyright owners nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
 * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>

#include "capinfo.h"
#include "libpcap.h"
#include "err.h"
#include "fakepcap.h"

/* state of the current pcap file */
struct pcap_file_header phdr;
int modified;
int swapped;

/* return flag if this is a pcap file */
int
is_pcap(int fd)
{

    if (lseek(fd, SEEK_SET, 0) != 0) {
        err(1, "Unable to seek to start of file");
    }

    if (read(fd, (void *)&phdr, sizeof(phdr)) != sizeof(phdr))
        return 0;

    switch (phdr.magic) {
    case PCAP_MAGIC:
        swapped = 0;
        modified = 0;
        break;

    case PCAP_SWAPPED_MAGIC:
        swapped = 1;
        modified = 0;
        break;

    case PCAP_MODIFIED_MAGIC:
        swapped = 0;
        modified = 1;
        break;

    case PCAP_SWAPPED_MODIFIED_MAGIC:
        swapped = 1;
        modified = 1;
        break;

    default:
        return 0;
    }

    /* ensure everything is in host-byte order */
    if (swapped) {
        phdr.version_major = SWAPSHORT(phdr.version_major);
        phdr.version_minor = SWAPSHORT(phdr.version_minor);
        phdr.snaplen = SWAPLONG(phdr.snaplen);
        phdr.linktype = SWAPLONG(phdr.linktype);
    }

    /* version, snaplen, & linktype magic */
    if (phdr.version_major != 2)
        return 0;

    return 1;
}

int
get_next_pcap(int fd, struct packet *pkt)
{
    struct pcap_pkthdr p1, *p;
    struct pcap_mod_pkthdr p2;

    if (modified) {
        if (read(fd, &p2, sizeof(p2)) != sizeof(p2))
            return 0;
        p = &p2.hdr;
    }
    else {
        if (read(fd, &p1, sizeof(p1)) != sizeof(p1))
            return 0;
        p = &p1;
    }

    if (swapped) {
        pkt->len = SWAPLONG(p->caplen);
        pkt->ts.tv_sec = SWAPLONG(p->ts.tv_sec);
        pkt->ts.tv_usec = SWAPLONG(p->ts.tv_usec);
        pkt->actual_len = SWAPLONG(p->len);
    }
    else {
        pkt->len = p->caplen;
        pkt->ts = p->ts;
        pkt->actual_len = p->len;
    }

    if (read(fd, &pkt->data, pkt->len) != pkt->len)
        return 0;

    return pkt->len;
}

/* 
 * Print statistics about a pcap file. is_pcap() must be called first 
 * to read the pcap header.
 */
void
stat_pcap(int fd, struct pcap_info *p)
{
    struct packet pkt;
    char *endian[2];

#ifdef LIBNET_LIL_ENDIAN
    endian[0] = "little endian";
    endian[1] = "big endian";
#else
    endian[0] = "big endian";
    endian[1] = "little endian";
#endif

    p->modified = modified;
    p->swapped = swapped ? endian[1] : endian[0];
    p->phdr = phdr;
    p->linktype = pcap_datalink_val_to_description(phdr.linktype);

    p->bytes = p->trunc = 0;
    for (p->cnt = 0; get_next_pcap(fd, &pkt); p->cnt++) {
        /* grab time of the first packet */
        if (p->cnt == 0)
            TIMEVAL_TO_TIMESPEC(&pkt.ts, &p->start_tm);

        /* count p->truncated packets */
        p->bytes += pkt.len;
        if (pkt.actual_len > phdr.snaplen)
            p->trunc++;
    }
    /* grab time of the last packet */
    TIMEVAL_TO_TIMESPEC(&pkt.ts, &p->finish_tm);
}

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