/*
 *  $Id: arp.c,v 1.5 2004/01/28 19:45:00 mike Exp $
 *
 *  libnet 1.1
 *  Build an ARP packet
 *
 *  Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
 *  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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
 *
 */

// some modified by hoppang

#include<libnet.h>

int main(int argc, char *argv[])
{
    int c;					// 반환값 체크용 변수.
    u_int32_t src, dst;		// 발신자/수신자 IP 주소를 저장.
    libnet_t *l;			// libnet 객체
    libnet_ptag_t t;		// protocol tag..라는데.
    char *device = NULL;	// 네트워크 카드 이름..을 저장
    u_int8_t *packet;		// 패킷 데이터
    u_int32_t packet_s;		// 패킷 길이.
    char errbuf[LIBNET_ERRBUF_SIZE];	// 에러메시지 저장용
	libnet_ether_addr* src_mac_addr;	// 내 컴퓨터의 mac 주소를 담을 변수.
	// 브로드캐스팅은 전부 0xFF다. 숫자가 다 똑같으니 바이트오더 걱정할 필요도 없구나.
	u_char broadcast_mac[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

    printf("libnet 1.1 packet shaping: ARP[link -- autobuilding ethernet]\n");

    if (argc > 1)
    {
         device = argv[1];
    }

	// libpcap이 그렇듯이, 관리자 권한을 얻지 못하면 실패한다.
    l = libnet_init(
            LIBNET_LINK_ADV,                        /* injection type */
            device,                                 /* network interface */
            errbuf);                                /* errbuf */

    if (l == NULL)
    {
        fprintf(stderr, "%s", errbuf);
        exit(EXIT_FAILURE);
    }
	else

    /*
     *  Build the packet, remmebering that order IS important.  We must
     *  build the packet from lowest protocol type on up as it would
     *  appear on the wire.  So for our ARP packet:
     *
     *  -------------------------------------------
     *  |  Ethernet   |           ARP             |
     *  -------------------------------------------
     *         ^                     ^
     *         |------------------   |
     *  libnet_build_ethernet()--|   |
     *                               |
     *  libnet_build_arp()-----------|
     */

	// 내 컴퓨터의 IP주소 구하기.
	src = libnet_get_ipaddr4(l);
	// 이 부분은 문제가 좀 있는데.. 인텔 CPU와 같은 바이트오더(LE)에서만 값이 제대로 들어간다.
	// PPC나 뭐.. 여튼 문제가  가능성이 많지만 귀찮으니까 그냥 써야지.
	// 192.168.1.101(내 놋북 IP)
	dst = (192) + (168<<8) + (1<<16) + (101<<24);
	// 내 컴퓨터의 mac 주소 구하기.
	src_mac_addr = libnet_get_hwaddr(l);
    t = libnet_autobuild_arp(
            ARPOP_REQUEST,						/* operation type */
            src_mac_addr->ether_addr_octet,		/* sender hardware addr */
            (u_int8_t *)&src,					/* sender protocol addr */
            broadcast_mac,						/* target hardware addr */
            (u_int8_t *)&dst,					/* target protocol addr */
            l);									/* libnet context */

	// 이 밑으로는 전부 arp_new.c와 같음.
    if (t == -1)
    {
        fprintf(stderr, "Can't build ARP header: %s\n", libnet_geterror(l));
        goto bad;
    }

    t = libnet_autobuild_ethernet(
            broadcast_mac,                               /* ethernet destination */
            ETHERTYPE_ARP,                          /* protocol type */
            l);                                     /* libnet handle */
    if (t == -1)
    {
        fprintf(stderr, "Can't build ethernet header: %s\n",
                libnet_geterror(l));
        goto bad;
    }


    if (libnet_adv_cull_packet(l, &packet, &packet_s) == -1)
    {
        fprintf(stderr, "%s", libnet_geterror(l));
    }
    else
    {
        fprintf(stderr, "packet size: %d\n", packet_s);
        libnet_adv_free_packet(l, packet);
    }

    c = libnet_write(l);

    if (c == -1)
    {
        fprintf(stderr, "Write error: %s\n", libnet_geterror(l));
        goto bad;
    }
    else
    {
        fprintf(stderr, "Wrote %d byte ARP packet from context \"%s\"; "
                "check the wire.\n", c, libnet_cq_getlabel(l));
    }
    libnet_destroy(l);
    return (EXIT_SUCCESS);
bad:
    libnet_destroy(l);
    return (EXIT_FAILURE);
}

/* EOF */