1 files changed, 12 insertions, 7 deletions
diff --git a/lib/VNDBUtil.pm b/lib/VNDBUtil.pm
index 5e7135cf..c864fda9 100644
--- a/lib/VNDBUtil.pm
+++ b/lib/VNDBUtil.pm
@@ -7,7 +7,7 @@ use warnings;
 use Exporter 'import';
 use Encode 'encode_utf8';
 use Unicode::Normalize 'NFKD';
-use Socket 'inet_pton', 'inet_ntop', 'AF_INET6';
+use Socket 'inet_pton', 'inet_ntop', 'AF_INET', 'AF_INET6';
 
 our @EXPORT = qw|shorten bb2html gtintype normalize normalize_titles normalize_query imgsize norm_ip|;
 
@@ -246,17 +246,22 @@ sub imgsize {
 
 
 # Normalized IP address to use for duplicate detection/throttling. For IPv4
-# this is just the normal address, but for IPv6 this is the /48 subnet, with
-# the rest of the address zero'd.
+# this is the /23 subnet (is this enough?), for IPv6 the /48 subnet, with the
+# least significant bits of the address zero'd.
 sub norm_ip {
     my $ip = shift;
-    return $ip if $ip !~ /:/;
 
-    # There's a whole bunch of IPv6 manipulation modules on CPAN, but many seem
+    # There's a whole bunch of IP manipulation modules on CPAN, but many seem
     # quite bloated and still don't offer the functionality to return an IP
     # with its mask applied (admittedly not a common operation). The libc
-    # socket functions will do fine in parsing and formatting IPv6 addresses,
-    # and the actual masking is quite trivial in binary form.
+    # socket functions will do fine in parsing and formatting addresses, and
+    # the actual masking is quite trivial in binary form.
+    my $v4 = inet_pton AF_INET, $ip;
+    if($v4) {
+      $v4 =~ s/(..)(.)./$1 . chr(ord($2) & 254) . "\0"/se;
+      return inet_ntop AF_INET, $v4;
+    }
+
     $ip = inet_pton AF_INET6, $ip;
     return '::' if !$ip;
     $ip =~ s/^(.{6}).+$/$1 . "\0"x10/se;