Truncate IP addresses

nginx.conf

@@ -14,9 +14,15 @@ http {
     include       /etc/nginx/mime.types;
     default_type  application/octet-stream;
 
+    map $http_x_forwarded_for $forwarded_anon {
+        ~(?P<ip>\d+\.\d+\.\d+)\.    $ip.0;
+        ~(?P<ip>[^:]+:[^:]+):       $ip::;
+        default                     0.0.0.0;
+    }
+
     log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                       '$status $body_bytes_sent "$http_referer" '
-                      '"$http_user_agent" "$http_x_forwarded_for"';
+                      '"$http_user_agent" "$forwarded_anon"';
 
     access_log  /logs/access.log  main;