freebsd-dev/contrib/ipfilter/mkfilters

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#!/usr/local/bin/perl
# for best results, bring up all your interfaces before running this
open(I, "ifconfig -a|") || die $!;
while (<I>) {
chop;
if (/^[a-zA-Z]+\d+:/) {
($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";
$grpi = 0;
foreach $i (keys %ifaces) {
if (!defined($inet{$i})) {
next;
}
$grpi += 100;
$grpo = $grpi + 50;
if ($i !~ /lo/) {
print "pass out on $i all head $grpo\n";
print "block out from 127.0.0.0/8 to any group $grpo\n";
print "block out from any to 127.0.0.0/8 group $grpo\n";
print "block out from any to $inet{$i}/32 group $grpo\n";
print "pass in on $i all head $grpi\n";
print "block in from 127.0.0.0/8 to any group $grpi\n";
print "block in from $inet{$i}/32 to any group $grpi\n";
foreach $j (keys %ifaces) {
if ($i ne $j && $j !~ /^lo/ && defined($net{$j})) {
print "block in from $net{$j} to any group $grpi\n";
}
}
}
}