Re: Of Net::Arp and Hashes

The error IS in the XS code. I added a printf() line to ARP.xs:

char *
arp_lookup(dev, ip, mac)
        unsigned char *dev;   
        unsigned char *ip;
        unsigned char *mac;
        CODE:
          char tmp[20];
          printf("TMP(%d) IS %s\n", strlen(tmp), tmp);
          if(SOCK_TYPE == SOCK_RAW)
          {
            arp_lookup_bsd(dev,ip,tmp);
          }
          else
          {
            arp_lookup_linux(dev,ip,tmp);
          }

          mac = tmp;

        OUTPUT:  
        mac
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Then I ran this:

#!/usr/bin/perl

use Net::ARP;

my $mac = "";
Net::ARP::arp_lookup(eth1 => '172.18.0.1', $mac);
print "mac=$mac\n";
Net::ARP::arp_lookup(eth1 => '172.18.0.1', $mac);
print "mac=$mac\n";
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I get this as output:

TMP(0) IS 
mac=
TMP(8) IS p锟锟斤拷
mac=00:0E:D7:80:37:20
[download]

The simple fix is change char tmp[20]; to char tmp[20] = "unknown";. I will be sending a bug report to the author.

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

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Re^2: Of Net::Arp and Hashes by cmilfo (Hermit) on Jan 13, 2006 at 19:18 UTC
++japhy!	[reply]
Re^3: Of Net::Arp and Hashes by japhy (Canon) on Jan 13, 2006 at 20:12 UTC
The author has already responded, fixed the bug (and an identical one in get_mac()), and uploaded a new version to CPAN. 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	[reply]
Re^4: Of Net::Arp and Hashes by idsfa (Vicar) on Jan 14, 2006 at 03:46 UTC
IMHO, still wrong. The C code returns a value to indicate error conditions, but the XS has no way to convey this to the perl module. I just think that this whole function of the module is ill-conceived. The intelligent reader will judge for himself. Without examining the facts fully and fairly, there is no way of knowing whether vox populi is really vox dei, or merely vox asinorum. — Cyrus H. Gordon	[reply]