dhcp-packet-build.c

this is sample about DHCP-agent

/* $Header: /cvsroot/dhcp-agent/dhcp-agent/src/dhcp-packet-build.c,v 1.9 2003/06/26 23:56:42 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.
 *
 * Packet building routines:
 * Utility routines wrapped around the packet objects.
 * 
 */

#define MODULE_NAME "dhcp-packet-build"

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

/* constants we need. */

static const eth_addr_t eth_null = { {0x00, 0x00, 0x00, 0x00, 0x00, 0x00} };
static const eth_addr_t eth_broadcast = { {0xff, 0xff, 0xff, 0xff, 0xff, 0xff} };
static const uint32_t ip_addr_broadcast = 0xffffffff;

/* * * * * * * * * * * * * * *
 * Packet writing routines.  *
 * * * * * * * * * * * * * * */

static void write_packet_dhcp(rawnet_t *net)
{
    char *packet_ptr;

    /* Dump packet images for DHCP. */

    packet_ptr = net->packet_data;
    memset(packet_ptr, 0, net->mtu); /* fixme: fix the default mtu issue! */

    eth_write_packet_image(net->ether_p, packet_ptr);
    packet_ptr += ETH_HDR_LEN;

    ip_write_packet_image(net->ip_p, packet_ptr);
    packet_ptr += (ip_get_hl(net->ip_p));

    udp_write_packet_image(net->udp_p, packet_ptr);
    packet_ptr += UDP_HDR_LEN;

    dhcp_write_packet_image(net->dhcp_p, packet_ptr);

    /* Run the IP checksum routine. */

    ip_checksum((net->packet_data + ETH_HDR_LEN), (net->packet_len - ETH_HDR_LEN));

    return;
}

static void write_packet_arp(rawnet_t *net)
{
    char *packet_ptr;

    /* Dump packet images for ARP/UNARP. */

    packet_ptr = net->packet_data;
    memset(packet_ptr, 0, net->mtu); /* fixme: fix the default mtu issue! */

    eth_write_packet_image(net->ether_p, packet_ptr);
    packet_ptr += ETH_HDR_LEN;

    arp_write_packet_image(net->arp_p, packet_ptr);

    return;
}

static void write_packet_icmp(rawnet_t *net)
{
    unsigned char *packet_ptr;

    /* Dump packet images for ICMP. */

    packet_ptr = net->packet_data;
    memset(packet_ptr, 0, net->mtu); /* fixme: fix the default mtu issue! */

    eth_write_packet_image(net->ether_p, packet_ptr);
    packet_ptr += ETH_HDR_LEN;

    ip_write_packet_image(net->ip_p, packet_ptr);
    packet_ptr += (ip_get_hl(net->ip_p));

    icmp_write_packet_image(net->icmp_p, packet_ptr);

    ip_checksum((net->packet_data + ETH_HDR_LEN), (net->packet_len - ETH_HDR_LEN));

    return;
}

static void write_packet(rawnet_t *net)
{

    switch (net->type) {

    case RAWNET_DHCP:
        write_packet_dhcp(net);
        break;

    case RAWNET_ARP:
        write_packet_arp(net);
        break;

    case RAWNET_ICMP:
        write_packet_icmp(net);
        break;

    default:
        FATAL_MESSAGE
            ("warning: invalid packet type passed to write_packet() -- this is a bug report it please.");
        break;
    }

    return;
}

/* * * * * * * * * * * *
 * Ethernet Routines.  *
 * * * * * * * * * * * */

static void build_eth_proc(rawnet_t *net,
                           eth_addr_t source_hw_addr, eth_addr_t dest_hw_addr, uint16_t type)
{
    eth_set_dst_addr(net->ether_p, dest_hw_addr);
    eth_set_src_addr(net->ether_p, source_hw_addr);
    eth_set_type(net->ether_p, type);

    return;
}

/* build ethernet header with broadcast destination address. */
static void build_eth_broadcast(rawnet_t *net, eth_addr_t source_hw_addr, uint16_t type)
{
    build_eth_proc(net, source_hw_addr, eth_broadcast, type);
    return;
}

static void build_eth(rawnet_t *net, eth_addr_t source_hw_addr, eth_addr_t dest_hw_addr,
                      uint16_t type)
{
    build_eth_proc(net, source_hw_addr, dest_hw_addr, type);
    return;
}

/* * * * * * * * * * * *
 * ARP/UNARP Routines. *
 * * * * * * * * * * * */

/* Build ARP packet: write out all the members. */
static void build_arp(rawnet_t *net,
                      uint16_t opcode,
                      eth_addr_t sender_hw_addr,
                      uint32_t sender_ip_addr,
                      eth_addr_t target_hw_addr, uint32_t target_ip_addr, uint8_t hardware_len)
{ /* for unarp it's 0 */

    arp_set_hardware_type(net->arp_p, ARP_HRD_ETH);
    arp_set_protocol_type(net->arp_p, ARP_PRO_IP);
    arp_set_hardware_len(net->arp_p, hardware_len);
    arp_set_protocol_len(net->arp_p, IP_ADDR_LEN);
    arp_set_op(net->arp_p, opcode);
    arp_set_sender_hardware_address(net->arp_p, sender_hw_addr);
    arp_set_sender_protocol_address(net->arp_p, sender_ip_addr);
    arp_set_target_hardware_address(net->arp_p, target_hw_addr);
    arp_set_target_protocol_address(net->arp_p, target_ip_addr);

    return;
}

/* Build ARP Proc: Do all the work for an arp packet. */
static void build_arp_proc(rawnet_t *net,
                           uint16_t opcode,
                           eth_addr_t sender_hw_addr,
                           uint32_t sender_ip_addr,
                           eth_addr_t target_hw_addr, uint32_t target_ip_addr)
{
    build_eth_broadcast(net, sender_hw_addr, ETH_TYPE_ARP);
    build_arp(net, opcode, sender_hw_addr, sender_ip_addr, target_hw_addr,
              target_ip_addr, ETH_ADDR_LEN);

    net->type = RAWNET_ARP;
    net->packet_len = ETH_HDR_LEN + ARP_ETHIP_LEN + ARP_HDR_LEN;

    write_packet(net);
    return;
}

/* Interface routines to ARP/UNARP building. */

/* Build ARP reply. */
void build_arp_reply(rawnet_t *net,
                     uint32_t source_addr,
                     uint32_t dest_addr, eth_addr_t source_hw_addr, eth_addr_t dest_hw_addr)
{
    build_arp_proc(net, ARP_OP_REPLY, source_hw_addr, source_addr, dest_hw_addr, dest_addr);
    return;
}

/* Build ARP request. */
void build_arp_request(rawnet_t *net,
                       uint32_t source_addr, uint32_t dest_addr, eth_addr_t source_hw_addr)
{
    build_arp_proc(net, ARP_OP_REQUEST, source_hw_addr, source_addr, eth_broadcast, dest_addr);
    return;
}

/* Build ARP reply with broadcast destination hardware address. */
void build_arp_reply_broadcast(rawnet_t *net, uint32_t source_addr, eth_addr_t source_hw_addr)
{

    build_arp_reply(net, source_addr, ip_addr_broadcast, source_hw_addr, eth_broadcast);
    return;
}

/* only one way to build unarp, so don't procify it. */
void build_unarp(rawnet_t *net, uint32_t source_addr, eth_addr_t source_hw_addr)
{
    build_eth_broadcast(net, source_hw_addr, ETH_TYPE_ARP);
    build_arp(net, ARP_OP_REPLY, source_hw_addr, 0, eth_broadcast, ip_addr_broadcast, ETH_ADDR_LEN);

    net->type = RAWNET_ARP;
    net->packet_len = ETH_HDR_LEN + ARP_ETHIP_LEN + ARP_HDR_LEN;

    write_packet(net);

    return;
}

/* * * * * * * * * * * * * * * *
 * Internet Protocol routines. *
 * * * * * * * * * * * * * * * */

static void build_ip(rawnet_t *net, uint16_t ip_len, uint8_t protocol,
                     ip_addr_t source_addr, ip_addr_t dest_addr)
{
    ip_set_hl(net->ip_p, IP_HDR_LEN);
    ip_set_tos(net->ip_p, IP_TOS_DEFAULT);
    ip_set_len(net->ip_p, ip_len);
    ip_set_id(net->ip_p, IP_DF);
    ip_set_off(net->ip_p, 0);