/*
 * Written by Pejman Moghadam / 1401-02-30
 * Public domain.
 *
 */

/* gcc src.c -lpcap */

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <pcap/pcap.h>
#include <netinet/ether.h>

void show_packet(char *buf, int len)
{
    unsigned char ch;
    int i, j, k, space;

    for (i = 0; i < len; i+=16) {
        printf("\t0x%04x  ", i);
        for (j = i; j < i+16 && j < len; j++) {
            ch = (unsigned char)buf[j];
            printf("%02X ", ch);
        }
 
        if (j == i+16)
            space = 1;
        else
            space = 1 + (16*3) - (j-i)*3;
 
        for (k = 0; k < space; k++)
            printf(" ");
 
        for (j = i; j < i+16 && j < len; j++) {
            ch = (unsigned char)buf[j];
            if (ch <= 32 || ch >= 127)
                ch = '.';
            printf("%c", ch);
        }
        printf("\n");
    }
    printf("\n");
}

char *ether_ntoa_padded(const struct ether_addr *addr, char *buf)
{
    sprintf (buf, "%02x:%02x:%02x:%02x:%02x:%02x",
        addr->ether_addr_octet[0], addr->ether_addr_octet[1],
        addr->ether_addr_octet[2], addr->ether_addr_octet[3],
        addr->ether_addr_octet[4], addr->ether_addr_octet[5]);
    return buf;
}

void show_ethernet_header(char *packet, int len)
{
    /* man 3 ether_aton */
    /* /usr/include/linux/if_ether.h */

    struct ethhdr *h;
    h = (struct ethhdr *)packet;

    struct ether_addr *dst;
    dst = (struct ether_addr *)(h->h_dest);

    struct ether_addr *src;
    src = (struct ether_addr *)(h->h_source);
    
    char addr_str[INET6_ADDRSTRLEN];
    printf("Ethernet header info:\n");
    printf("\tdst: %s (%s)\n", ether_ntoa(dst), ether_ntoa_padded(dst, addr_str));
    printf("\tsrc: %s (%s)\n", ether_ntoa(src), ether_ntoa_padded(src, addr_str));
    printf("\ttype: 0x%04X\n", ntohs(h->h_proto));
    printf("\n");
}

void packet_handler(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes)
{
    static int packet_count = 0;
    for (int i = 0;i < 80; i++) putchar('#');
    printf("\n# Packet: %d , Size: %d\n", ++packet_count, h->len);
    show_packet((char *)bytes, h->len);
    show_ethernet_header((char *)bytes, h->len);
}

int main()
{
    pcap_t *p;
    char errbuf[PCAP_ERRBUF_SIZE];
    p = pcap_open_offline("capture.pcap", errbuf);
    if (p == NULL) {
        fprintf(stderr, "\npcap_open_offline() failed: %s\n", errbuf);
        exit(EXIT_FAILURE);
    }

    if (pcap_loop(p, 0, packet_handler, NULL) < 0) {
        fprintf(stderr, "\npcap_loop() failed: %s\n", pcap_geterr(p));
        exit(EXIT_FAILURE);
    }

    return 0;
}