Check this out:

#!/usr/usc/perl/5.6.1/bin/perl
use strict;
use warnings;
$|++;

my $dev = shift @ARGV;
$dev ||= 'qe0';

my $filter_string = 'udp src port 68 and dst port 67';
#my $filter_string = 'udp';

my $snaplen = 1508;
my $promisc = 1;
my $timeout = 100;
my $count = -1;

use Net::Pcap;

my $err = '';
my $cap_dev;
my $filter = '';
my $net = -256;

$cap_dev = Net::Pcap::open_live($dev, $snaplen, $promisc, $timeout, \$
+err);
die "$err\n" if $err;

Net::Pcap::compile($cap_dev, \$filter, $filter_string, 0, -256)
    and die "compile: $err\n";

Net::Pcap::setfilter($cap_dev, $filter);
Net::Pcap::loop($cap_dev, $count, \&callback, 'woot');
Net::Pcap::close($cap_dev);
exit 0;

sub callback {
    my ($user_data, $hdr, $pkt) = @_;
    warn "packet!\n";
    my %header = %$hdr;
    #process_packet(\%header, $pkt);
    my $len = length $pkt;
#    warn "$header{len} $header{caplen} $len\n"; 
}
    
sub process_packet {
    my ($hdr, $pkt) = @_;
    my $len = length $pkt;
    warn "$hdr->{len} $hdr->{caplen} $len\n";
}
[download]

This happily prints:

packet!
packet!
packet!
packet!

Unless I uncomment the warn line. Then I get:

packet!
342 342 342
Segmentation Fault (core dumped)

Which seems quite odd. Any ideas what could cause this behavior?

This is perl, v5.6.1 built for sun4-solaris
Net::Pcap 0.04
libpcap 0.7.1

Otherwise I use the perl and pcap (tcpdump...) all the time without seeing anything this bizare.