I think there's a bug in the XS code: 
char *
arp_lookup(dev, ip, mac)
    unsigned char *dev;
    unsigned char *ip;
    unsigned char *mac;
    CODE:
      char tmp[20];

      if(SOCK_TYPE == SOCK_RAW)
      {
        arp_lookup_bsd(dev,ip,tmp);
      }
      else
      {
        arp_lookup_linux(dev,ip,tmp);
      }

      mac = tmp;

    OUTPUT:
    mac

[download]
That's the XS that handles arp_lookup(). Notice that it creates char tmp[20] without ever assigning anything to it (such as ""). I'm not a C guru, but that's a definite NO-NO. Because in the arp_lookup_linux() code, we have: 
int arp_lookup_linux(char *dev, char *ip, char *mac)
{
  FILE *fp;
  char ipaddr[100];
  char line[200];
  char hwa[100];
  char mask[100];
  char device[100];
  int num, type, flags;
  
  if(strlen(mac) > 0)
    strcpy(mac,"unkown");
  else
    return -1;

[download]
which leads me to believe -1 is being returned. I just think it's suspect.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re^3: Of Net::Arp and Hashes by japhy
in thread Of Net::Arp and Hashes by cmilfo

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