#include <arpa/inet.h>
#include <iostream>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <net/ethernet.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>

using namespace std;

struct eth_addr {
    unsigned char addr[6];
};

struct __attribute__((__packed__)) myarp {
    struct ethhdr eth_hdr;
    struct arphdr arp_hdr;
    struct eth_addr sender_ha;
    struct in_addr sender_ip;
    struct eth_addr target_ha;
    struct in_addr target_ip;
};

ostream &operator<<(ostream &out, const struct in_addr &ip)
{
    out << inet_ntoa(ip);
    return out;
}

ostream &operator<<(ostream &out, const struct eth_addr &eth)
{
    char buf[32];
    sprintf(buf, "%02x:%02x:%02x:%02x:%02x:%02x",
            eth.addr[0], eth.addr[1], eth.addr[2], eth.addr[3], eth.addr[4], eth.addr[5]);
    out << buf;
    return out;
}

ostream &operator<<(ostream &out, const struct myarp &arp)
{
    if (ntohs(arp.arp_hdr.ar_op) == ARPOP_REQUEST)
        out << "Request: who-has " << arp.target_ip << " tell " << arp.sender_ip;
    else if (ntohs(arp.arp_hdr.ar_op) == ARPOP_REPLY)
        out << "Reply: " << arp.sender_ip << " is-at " << arp.sender_ha;
    return out;
}

void dump(const unsigned char *ptr, ssize_t len)
{
    struct myarp *arp = (struct myarp *)ptr;
    if (ntohs(arp->eth_hdr.h_proto) != ETH_P_ARP)
        return;
    cout << *arp << endl;
}

int main(int argc, char *argv[])
{
    int sockfd;
    ssize_t nrecv;
    unsigned char buf[1024];

    sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }
    for (;;) {
        nrecv = recvfrom(sockfd, buf, sizeof(buf), 0, NULL, NULL);
        if (nrecv < 0) {
            perror("socket");
            exit(1);
        }
        dump(buf, nrecv);
    }
}