arp.c

用libpcap和libnet写arp包

#include <stdio.h>
#include <pcap.h>
#include <libnet.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
int get_hw_addr(char *, unsigned char *, struct in_addr *);
int main()
{
    char *dev;
    char errbuf[PCAP_ERRBUF_SIZE];
    unsigned char bcast_mac[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
    unsigned char my_mac[6] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06 };
    unsigned char zero_mac[6] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
    char *ipptr = "10.1.0.155";
    libnet_t *handle;
    struct in_addr ipaddr, myaddr;
    int i;

    inet_aton(ipptr, &ipaddr);
    dev = pcap_lookupdev(errbuf);
    if (dev == NULL) {
        fprintf(stderr, "Couldn't find device %s: %s\n", dev, errbuf);
        return 2;
    }
    if (get_hw_addr(dev, my_mac, &myaddr) == -1) {
        return 2;
    }
    ipaddr.s_addr = myaddr.s_addr & 0x00ffffff;
    handle = libnet_init(LIBNET_LINK, dev, errbuf);
    if (handle == NULL) {
        fprintf(stderr, "Couldn't initiate handle: %s\n", errbuf);
        return 2;
    }

    for (i = 0; i < 256; i++) {
        if (libnet_build_arp(ARPHRD_ETHER,
                             ETHERTYPE_IP,
                             6,
                             4,
                             ARPOP_REQUEST,
                             my_mac,
                             (unsigned char *) &myaddr,
                             zero_mac,
                             (unsigned char *) &ipaddr, NULL, 0, handle,
                             0) == -1) {
            fprintf(stderr, "Couldn't build arp: %s\n", errbuf);
            libnet_destroy(handle);
            return 2;
        }
        if (libnet_build_ethernet
            (bcast_mac, my_mac, ETHERTYPE_ARP, NULL, 0, handle, 0) == -1) {
            fprintf(stderr, "Couldn't build ethernet: %s\n", errbuf);
            libnet_destroy(handle);
            return 2;
        }
        if (libnet_write(handle) == -1) {
            fprintf(stderr, "Couldn't send package: %s\n", errbuf);
            libnet_destroy(handle);
            return 2;
        }
        libnet_clear_packet(handle);
        ipaddr.s_addr += 0x01000000;
    }

    libnet_destroy(handle);

    return 0;
}

int get_hw_addr(char *dev, unsigned char macbuf[6], struct in_addr *myaddr)
{
    libnet_t *handle;
    char errbuf[LIBNET_ERRBUF_SIZE] = "";
    struct libnet_ether_addr *mac;

    handle = libnet_init(LIBNET_LINK, dev, errbuf);
    if (!handle) {
        fprintf(stderr, "get_hw_addr(): libnet_init: %s\n", errbuf);
        return -1;
    }
    mac = libnet_get_hwaddr(handle);
    if (!mac) {
        fprintf(stderr, "get_hw_addr(): libnet_get_hwaddr: %s\n",
                libnet_geterror(handle));
        libnet_destroy(handle);
        return -1;
    }
    myaddr->s_addr = (unsigned long) libnet_get_ipaddr4(handle);
    memcpy(macbuf, mac->ether_addr_octet, 6);

    libnet_destroy(handle);
    return 0;
}