#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/time.h>
#include <unistd.h>
#include <err.h>
#include <fcntl.h>
#include <sysexits.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_arp.h>

#define BPF_PATH        "/dev/bpf"

static void
send_arp(int fd)
{
        char buf[128];
        struct ether_header *eh;
        struct arphdr *ah;
        struct in_addr sip, tip;
        int len, ret;

        memset(buf, 0, sizeof(buf));

        eh = (struct ether_header *)buf;
        ah = (struct arphdr *)(eh + 1);

        eh->ether_type = htons(ETHERTYPE_ARP);
        memcpy(eh->ether_shost, ether_aton("00:01:00:02:00:03"), sizeof(eh->ether_shost));
        memcpy(eh->ether_dhost, ether_aton("00:02:00:04:00:04"), sizeof(eh->ether_dhost));

        inet_pton(AF_INET, "1.2.3.4", &sip);
        inet_pton(AF_INET, "2.3.4.5", &tip);

        ah->ar_hrd = ARPHRD_ETHER;
        ah->ar_pro = htons(ETHERTYPE_IP);
        ah->ar_hln = 6;
        ah->ar_pln = sizeof(struct in_addr);
        ah->ar_op = htons(ARPOP_REQUEST);
        bcopy(eh->ether_shost, ar_sha(ah), ah->ar_hln);
        bcopy(&sip, ar_spa(ah), ah->ar_pln);
        bcopy(&tip, ar_tpa(ah), ah->ar_pln);

        len = sizeof(*eh) + sizeof(*ah) + 2 * sizeof(struct in_addr) + 2 * 6;

        if ((ret = write(fd, buf, len)) != len)
                warn("write() error");
}

int
main(int ac, char **av)
{
        int fd;
        struct ifreq ifr;
        u_int val;

        if (ac < 2)
                errx(EX_USAGE, "usage: %s iface [hdrcmplt]", av[0]);

        if ((fd = open(BPF_PATH, O_RDWR)) == -1)
                err(EX_OSFILE, "failed to open %s\n", BPF_PATH);

        memset(&ifr, 0, sizeof(ifr));
        strlcpy(ifr.ifr_name, av[1], sizeof(ifr.ifr_name));
        if (ioctl(fd, BIOCSETIF, &ifr) != 0)
                err(EX_DATAERR, "failed to bind to interface %s", av[1]);

        if (ac > 2) {
                val = 1;
                if (ioctl(fd, BIOCSHDRCMPLT, &val) != 0)
                        err(EX_OSERR, "failed to set BIOCSHDRCMPLT");
        }

        send_arp(fd);

        return (0);
}