Prevent proxied ips of the wrong flavour to poison our clients

ot_http.c

@@ -420,9 +420,17 @@ static ssize_t http_handle_announce( const int64 sock, struct ot_workstruct *ws,
   if( accesslist_is_blessed( cookie->ip, OT_PERMISSION_MAY_PROXY ) ) {
     ot_ip6 proxied_ip;
     char *fwd = http_header( ws->request, ws->header_size, "x-forwarded-for" );
-    if( fwd && scan_ip6( fwd, proxied_ip ) )
+    if( fwd && scan_ip6( fwd, proxied_ip ) ) {
+      /* If proxy reports an ipv6 address but we can only handle v4 (or vice versa), bail out */
+#ifndef WANT_V6
+      if( !ip6_isv4mapped(proxied_ip) )
+#else
+      if( ip6_isv4mapped(proxied_ip) )
+#endif
+        HTTPERROR_400_PARAM;
+
       OT_SETIP( &ws->peer, proxied_ip );
-    else
+    } else
       OT_SETIP( &ws->peer, cookie->ip );
   } else
 #endif