title: What exactly means iOS networking interface name? what's pdp_ip ? what's ap?
body: <p>I use following code to print all interface and it's mac address</p>
  
  <pre><code>- ( void )interfaceInfo{
  
  int                 mib[6];
  size_t              len;
  char                *buf;
  unsigned char       *ptr;
  struct if_msghdr    *ifm;
  struct sockaddr_dl  *sdl;
  
  mib[0] = CTL_NET;
  mib[1] = AF_ROUTE;
  mib[2] = 0;
  mib[3] = AF_LINK;
  mib[4] = NET_RT_IFLIST;
  
  char name[128];
  memset(name, 0, sizeof(name));
  for (int i=1; i&lt;20; i ++) {
      if (if_indextoname(i, name)) {
          printf("%s ",name);            
      }else{
          continue;
      }
  
      if ((mib[5] = if_nametoindex(name)) == 0) {
          printf("Error: if_nametoindex error\n");
          return NULL;
      }
  
      if (sysctl(mib, 6, NULL, &amp;len, NULL, 0) &lt; 0) {
          printf("Error: sysctl, take 1\n");
          return NULL;
      }
  
      if ((buf = malloc(len)) == NULL) {
          printf("Could not allocate memory. error!\n");
          return NULL;
      }
  
      if (sysctl(mib, 6, buf, &amp;len, NULL, 0) &lt; 0) {
          printf("Error: sysctl, take 2");
          free(buf);
          return NULL;
      }
  
          ifm = (struct if_msghdr *)buf;
          sdl = (struct sockaddr_dl *)(ifm + 1);
          ptr = (unsigned char *)LLADDR(sdl);
          NSString *macString = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X",
                         *ptr, *(ptr+1), *(ptr+2), *(ptr+3), *(ptr+4), *(ptr+5)];
          printf(" %s\n",[macString cStringUsingEncoding:NSUTF8StringEncoding]);
          free(buf);
      }
      return nil;
  }
  </code></pre>
  
  <p>I run the code on iPhone 5 and the output is </p>
  
  <pre><code>lo0  00:00:00:00:00:00
  pdp_ip0  00:00:00:00:00:00
  pdp_ip1  00:00:00:00:00:00
  pdp_ip2  00:00:00:00:00:00
  pdp_ip3  00:00:00:00:00:00
  ap1  EA:8D:28:44:32:2F
  en0  E8:8D:28:44:32:2F
  en1  EA:8D:28:44:32:31
  awdl0  4A:79:85:44:5B:4D
  //I faked parts data
  </code></pre>
  
  <p>I wanna know what's the pdp_ip? and what's the ap1,en1? </p>
  
  <p>I find out en0 is wifi hardware mac address</p>
  
  <p>Does ap1 and en1 is virtual interface? </p>
  
  <p>Thank you!</p>