#!/usr/local/bin/perl # for best results, bring up all your interfaces before running this open(I, "ifconfig -a|") || die $!; while () { chop; if (/^[a-zA-Z]+\d+:/) { ($iface = $_) =~ s/^([a-zA-Z]+\d+).*/$1/; $ifaces{$iface} = $iface; next; } if (/inet/) { if (/\-\-\>/) { # PPP, (SLIP?) ($inet{$iface} = $_) =~ s/.*inet ([^ ]+) \-\-\> ([^ ]+).*/$1/; ($ppp{$iface} = $_) =~ s/.*inet ([^ ]+) \-\-\> ([^ ]+).*/$2/; } else { ($inet{$iface} = $_) =~ s/.*inet ([^ ]+).*/$1/; } } if (/netmask/) { ($mask = $_) =~ s/.*netmask ([^ ]+).*/$1/; $mask =~ s/^/0x/ if ($mask =~ /^[0-9a-f]*$/); $netmask{$iface} = $mask; } if (/broadcast/) { ($bcast{$iface} = $_) =~ s/.*broadcast ([^ ]+).*/$1/; } } foreach $i (keys %ifaces) { $net{$i} = $inet{$i}."/".$netmask{$i} if (defined($inet{$i})); } # # print out route suggestions # print "#\n"; print "# The following routes should be configured, if not already:\n"; print "#\n"; foreach $i (keys %ifaces) { next if (($i =~ /lo/) || !defined($net{$i}) || defined($ppp{$i})); print "# route add $inet{$i} localhost 0\n"; } print "#\n"; # # print out some generic filters which people should use somewhere near the top # print "block in log quick from any to any with ipopts\n"; print "block in log quick proto tcp from any to any with short\n"; foreach $i (keys %ifaces) { if (!defined($inet{$i})) { next; } if ($i !~ /lo/) { print "block in on $i from 127.0.0.0/8 to any\n"; print "block out on $i from 127.0.0.0/8 to any\n"; print "block out on $i from any to 127.0.0.0/8\n"; print "block in on $i from $inet{$i}/32 to any\n"; print "block out on $i from any to $inet{$i}/32\n"; foreach $j (keys %ifaces) { if ($i ne $j && $j !~ /^lo/ && defined($net{$j})) { print "block in on $i from $net{$j} to any\n"; } } } }