dhcp-arp-discovery.c

this is sample about DHCP-agent

/* $Header: /cvsroot/dhcp-agent/dhcp-agent/src/dhcp-arp-discovery.c,v 1.5 2003/06/08 22:14:16 actmodern Exp $
 * 
 * Copyright 2002 Thamer Alharbash <[e-mail]>
 * 
 * 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.
 *
 */

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

#define MODULE_NAME "dhcp-arp-discovery"

/* Accept a list of arguments. Will contain rawnet first, and
 * then the ip address we're interested in. 
 *
 * Returns: 1 on error, 0 on success. 
 */

static int check_for_arp_reply(void *data)
{
    rawnet_t *net;
    unsigned char *addr, *received_addr;
    list_t *argument_list = data;

    net = list_first(argument_list);
    addr = list_second(argument_list);

    if(addr == NULL) {
        WARN_MESSAGE("no address passed to function -- skipping");
        return 0;
    }

    received_addr = arp_get_sender_protocol_address(net->arp_p);

    if((net->type == RAWNET_ARP) &&
       (arp_get_hardware_type(net->arp_p) == ARP_HRD_ETH) &&
       (arp_get_protocol_type(net->arp_p) == ARP_PRO_IP) &&
       (arp_get_hardware_len(net->arp_p) == ETH_ADDR_LEN) &&
       (arp_get_protocol_len(net->arp_p) == IP_ADDR_LEN) &&
       (arp_get_op(net->arp_p) == ARP_OP_REPLY)) {

        /* now check if its the address we're looking for */
        if(!memcmp(addr, received_addr, IP_ADDR_LEN))
            return 1; /* yes! address match */
        else
            return 0; /* nope we got another response. */
    }

    return 0; /* not the right kind of packet. */
}

int arp_discover_hardware_address(rawnet_t *net, int retries, int timeout, uint32_t address,
                                  eth_addr_t *mac_addr)
{
    list_t *arg_list;
    unsigned char *sender_addr;
    int retval;

    arg_list = list_create();
    list_add(arg_list, &address);
    list_add(arg_list, net);

    /* 0 for source ip, address to discover for dest, our
     * hardware address so we get a reply back. */

    build_arp_request(net, net->cip_addr, address, net->chw_addr);

    while(retries--) {

        retval =
            rawnet_packet_transact(net, arg_list, NULL, check_for_arp_reply,
                                   timeout);

        switch (retval) {

        case RAWNET_TIMEOUT:
            /* we timed out. retry. */
            break;

        case RAWNET_OK:

            /* Yummy! We got a valid reply! */

            sender_addr = arp_get_sender_hardware_address(net->arp_p);
            memcpy(mac_addr->data, sender_addr, ETH_ADDR_LEN);

            list_destroy(arg_list, NULL);

            return 0;

        case RAWNET_ERROR:
            /* wops error. this is bad. */
            ERROR_MESSAGE("received error from raw network handler.");
            list_destroy(arg_list, NULL);
            return 1;

        case RAWNET_USER_INTERRUPT:
            FATAL_MESSAGE("user interrupt. bailing out!");

        default:
            /* not good. */
            FATAL_MESSAGE("invalid return from rawnet_transact. this a bug report it.");
        }

    }

    list_destroy(arg_list, NULL);

    WARN_MESSAGE("timeout on discovery.");

    /* no response, return error. */
    return 1;

}