dhcp-sniff.c

this is sample about DHCP-agent

/* $Header: /cvsroot/dhcp-agent/dhcp-agent/src/dhcp-sniff.c,v 1.8 2003/06/28 16:30:01 actmodern Exp $
 *
 * Copyright 2002 Thamer Alharbash
 *
 * 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 names of the authors 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 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * dhcp-agent sniffer
 *
 */

#define MODULE_NAME "main"

#include "dhcp-local.h"
#include "dhcp-libutil.h"
#include "dhcp-librawnet.h"

#include "dhcp-print.h"
#include "dhcp-sniff-defaults.h"

int interactive = 1;
#if !defined(HAVE_PROGNAME)
const char *__progname;
#endif                          /* HAVE_PROGNAME */

char *workdirectory = ".";

static void usage(char *n)
{
    fprintf(stderr, "usage: %s [-bv] [-i interface_name ]\n", n);
    exit(1);
}

int main(int argc, char *argv[])
{
    int c;
    char *interface_name = NULL;
    rawnet_t *net;
    int retval;
    int sport, dport;
    stringbuffer_t *filter;
    print_packet p_packet = print_dhcp_packet_verbose;
    list_t *available_interfaces;

#if !defined(HAVE_PROGNAME)
    __progname = argv[0];
#endif                          /* HAVE_PROGNAME */

    while((c = getopt(argc, argv, "bvi:")) != -1) {

        switch (c) {

        case 'i':
            interface_name = xstrdup(optarg);
            break;

        case 'v':
            printf("%s version: %s\n", argv[0], VERSION);
            exit(0);

        case 'b':
            /* brief mode. */
            p_packet = print_dhcp_packet_brief;
            break;

        default:
            usage(argv[0]);
        }
    }

    if(interface_name == NULL) {

        /* get the first available on. */
        available_interfaces = rawnet_list_active_interfaces();

        if(available_interfaces != NULL) {

            interface_name = xstrdup(list_first(available_interfaces));
            list_destroy(available_interfaces, xfree);

        } else {
            FATAL_MESSAGE("unable to find suitable interface");
        }
    }

    /* Get port numbers from services db. */

    dport = rawnet_port_for_service("bootps", "udp");
    sport = rawnet_port_for_service("bootpc", "udp");

    if(dport == -1 || sport == -1) {

        dport = BOOTP_CLIENT;
        sport = BOOTP_SERVER;

    } else {

        dport = ntohs(dport);
        sport = ntohs(sport);
    }

    filter = stringbuffer_create();
    stringbuffer_aprintf(filter, "arp or icmp or (udp and (port %d or port %d))", dport, sport);

    /* It's ok not to set ports since we're not writing any packets. */
    net = rawnet_create(interface_name, stringbuffer_getstring(filter), DEFAULT_SNIFF_SNAPLEN, 0, 0, 1, 0);
    if(net == NULL) {
        FATAL_MESSAGE("unable to access raw network");
    }
    stringbuffer_destroy(filter);

    INFO_MESSAGE("opened %s for packet capturing", interface_name);
    printf("\n");

    /* Sniffing loop. */

    while(1) {

        retval = rawnet_get_packet(net, NULL);

        switch (retval) {

        case RAWNET_PCAP_ERROR:

            FATAL_MESSAGE("encountered fatal error while sniffing");

        case RAWNET_OK:

            /* Print it out */

            if(net->type == RAWNET_DHCP) {

                p_packet(net);
                printf("\n");
                fflush(stdout);

                dhcp_purge(net->dhcp_p);

            }
            break;

        case RAWNET_MALFORMED_PACKET:
        case RAWNET_UNHANDLED:
        default:
            break; /* don't handle. */
        }
    }

    exit(0);
}