// Title:   display_ip_address.c
// Purpose: Display IP, Netmask, Broadcast, and MAC
//--------------------------------------------------------
// REFERENCES:
// http://www.beej.us/guide/bgnet/output/html/multipage/structs.html
// http://www.basepath.com/aup/ex/structsockaddr__in.html
// http://www.gsp.com/cgi-bin/man.cgi?section=3&topic=getifaddrs
// http://www.hmug.org/man/3/getifaddrs.php
//--------------------------------------------------------
#include <stdio.h>             /* standard io headers */
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>        /* defines sturct addr_sockaddr_in */
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ifaddrs.h>           /* getifaddrs() */
#include <netinet/ether.h>     /* ether_ntoa() */
#include <netpacket/packet.h>  /* struct sockaddr_ll */
#define  MY_INTERFACE "ath0"
#define  DEBUG 1
//--------------------------------------------------------//
int main()
{
  struct ifaddrs *id;                      // linked list of structs (id->ifa_next points to next element)
  struct sockaddr_in *addr_sockaddr_in;    // sockaddr_in has an in_addr member
  struct sockaddr_in *netmask_sockaddr_in; // sockaddr_in has an ifa_netmask member
  struct ether_addr *mac_ether_addr;       // ether_addr, cast to 
  struct sockaddr_ll *mac_sockaddr_ll;     // 
  struct sockaddr_ll *ip_sockaddr_ll = (struct sockaddr_ll *)(id->ifa_addr);

  char *ascii_ip_address;                  // holds 'dots-and-number' ip address
  char *ascii_netmask_address;             // holds 'dots-and-number' netmask address
  char *ascii_broadcast_address;           // holds 'dots-and-number' broadcast address
  char *ascii_mac_address;                 // hods the 'colon-and-numbers' mac address
  char *ascii_interface;                   // holds name of the network interface
  
  int val;                                 // socket descriptor is junst an int 

  val = getifaddrs(&id);                   // getifaddrs function stores a reference to a linked list of the network interfaces
                                           // 

  for ( ; id != NULL ; id = id->ifa_next)  // Loop through all interfaces known to getifaddrs
					   // enter section below,
					   // then point to next struct in linked list
  {
    
   if ( id->ifa_addr != NULL )   // ifa_addr contains either interface address OR link level address OR NULL
   {
    if ( id->ifa_addr->sa_family == AF_INET )                                   // "AF_INET" means internetwork: UDP, TCP, etc. */ 
    {
      if ( strcmp(id->ifa_name, MY_INTERFACE) == 0 )                            // if 'id->ifa_name' is MY_INTERFACE,enter section
      {
        ascii_interface=id->ifa_name;                                           // Output interface name string
        if( DEBUG )
	{ 
	  printf("Interface:   %s\n", ascii_interface);                      // Output the 'dots-and-number' ip
	}
        //--------------------------------------------------------//
        // IP 
        // 
        //--------------------------------------------------------//
        addr_sockaddr_in = (struct sockaddr_in *)(id->ifa_addr);                // cast struct sockaddr to struct sockaddr_in,
                                                                                // sockaddr_in has an ifa_addr member, but sockaddr doesn't
        ascii_ip_address = inet_ntoa( addr_sockaddr_in->sin_addr );             // convert socket ip to 'dots-and-number' ip
        if( DEBUG )
	{ 
          printf("IP Address:  %s\n", ascii_ip_address);                    // Output the 'dots-and-number' ip
        }
        //--------------------------------------------------------//
        // Netmask
        //--------------------------------------------------------//
        if ( id->ifa_netmask != NULL )                                          // checking for null before processing.
        {
          netmask_sockaddr_in = (struct sockaddr_in *)(id->ifa_netmask);        // cast struct sockaddr to be struct sockaddr_in,
                                                                                // sockaddr_in has an ifa_netmask member, but sockaddr doesn't 
          ascii_netmask_address = inet_ntoa( netmask_sockaddr_in->sin_addr );   // convert socket ip to 'dots-and-number' ip
          if( DEBUG )
	  { 
             printf("Netmask:     %s\n", ascii_netmask_address);             // Output the 'dots-and-number' netmask
          }
	}
        //--------------------------------------------------------//
        // Broadcast 
        //--------------------------------------------------------//
        if ( id->ifa_broadaddr != NULL )                                        // checking for null before processing.
        {
          netmask_sockaddr_in = (struct sockaddr_in *)(id->ifa_broadaddr);      // cat struct sockaddr to be sturct sockaddr_in,
          ascii_broadcast_address = inet_ntoa( netmask_sockaddr_in->sin_addr ); // struct sockaddr_in has an ifa_broadaddr member,
                                                                                // but sockaddr doesn't 
          if( DEBUG )
	  { 
            printf("Broadcast:   %s\n", ascii_broadcast_address);           // Output the 'dots-and-number' broadcast
	  }
        }
	
      }
    
    }
   } 
    //--------------------------------------------------------//
    // MAC
    //--------------------------------------------------------//
    if ( id->ifa_addr->sa_family == AF_PACKET )                                 // "AF_PACKET" contains the mac 
    {
     //if ( strcmp(id->ifa_name, "lo") != 0 )                                   // if 'id->ifa_name' is not loopback (lo),enter section
     if ( strcmp(id->ifa_name, MY_INTERFACE ) == 0 )                            // if 'id->ifa_name' is MY_INTERFACE,enter section
     {
       mac_sockaddr_ll = (struct sockaddr_ll *)(id->ifa_addr);                  // cast struct sockaddr to be struct sockaddr_ll 
                                                                                // sockaddr_ll has member sll_addr (the mac)
        if ( mac_sockaddr_ll->sll_hatype == ARPHRD_ETHER)                       // check for correct hatype to have a mac 
        {
          ascii_mac_address = ether_ntoa((struct ether_addr *)(mac_sockaddr_ll->sll_addr)); // cast sturct sockaddr_ll to struct ether_addr
	                                                                                        // ether_ntoa only works on struct ether_addr
          if( DEBUG )
	  { 
            printf("MAC:         %s\n", ascii_mac_address);     // Output  the 'dots-and-number' mac
          }
	}
      }     
      //break;        // Just grab first interface
      //printf("\n"); // Print all interfaces
    } 
  }  
  // should run  freeifaddrs();
  freeifaddrs (id);

  printf("%s %s  %s %s %s\n", ascii_interface, ascii_ip_address, ascii_netmask_address, ascii_broadcast_address, ascii_mac_address);
  return 0;
}