From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6B0BC4332F for ; Thu, 16 Sep 2021 11:26:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF211610D1 for ; Thu, 16 Sep 2021 11:26:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238033AbhIPL2M (ORCPT ); Thu, 16 Sep 2021 07:28:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33620 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234769AbhIPL2K (ORCPT ); Thu, 16 Sep 2021 07:28:10 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:12e:520::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2909DC061574; Thu, 16 Sep 2021 04:26:50 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1mQpXN-0002K7-IT; Thu, 16 Sep 2021 13:26:41 +0200 Date: Thu, 16 Sep 2021 13:26:41 +0200 From: Florian Westphal To: Cole Dishington Cc: pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de, davem@davemloft.net, kuba@kernel.org, shuah@kernel.org, linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, coreteam@netfilter.org, netdev@vger.kernel.org, Anthony Lineham , Scott Parlane , Blair Steven Subject: Re: [PATCH net v4] net: netfilter: Fix port selection of FTP for NF_NAT_RANGE_PROTO_SPECIFIED Message-ID: <20210916112641.GC20414@breakpoint.cc> References: <20210916041057.459-1-Cole.Dishington@alliedtelesis.co.nz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210916041057.459-1-Cole.Dishington@alliedtelesis.co.nz> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Cole Dishington wrote: > + /* Avoid applying nat->range to the reply direction */ > + if (!exp->dir || !nat->range_info.min_proto.all || !nat->range_info.max_proto.all) { > + min = ntohs(exp->saved_proto.tcp.port); > + range_size = 65535 - min + 1; > + } else { > + min = ntohs(nat->range_info.min_proto.all); > + range_size = ntohs(nat->range_info.max_proto.all) - min + 1; > + } > + > /* Try to get same port: if not, try to change it. */ > - for (port = ntohs(exp->saved_proto.tcp.port); port != 0; port++) { > - int ret; > + first_port = ntohs(exp->saved_proto.tcp.port); > + if (min > first_port || first_port > (min + range_size - 1)) > + first_port = min; > > + for (i = 0, port = first_port; i < range_size; i++, port = (port - first_port + i) % range_size) { This looks complicated. As far as I understand, this could instead be written like this (not even compile tested): /* Avoid applying nat->range to the reply direction */ if (!exp->dir || !nat->range_info.min_proto.all || !nat->range_info.max_proto.all) { min = 1; max = 65535; range_size = 65535; } else { min = ntohs(nat->range_info.min_proto.all); max = ntohs(nat->range_info.max_proto.all); range_size = max - min + 1; } /* Try to get same port: if not, try to change it. */ port = ntohs(exp->saved_proto.tcp.port); if (port < min || port > max) port = min; for (i = 0; i < range_size; i++) { exp->tuple.dst.u.tcp.port = htons(port); ret = nf_ct_expect_related(exp, 0); if (ret != -EBUSY) break; port++; if (port > max) port = min; } if (ret != 0) { ... AFAICS this is the same, we loop at most range_size times, in case range_size is 64k, we will loop through all (hmmm, not good actually, but better make that a different change) else through given min - max range. If orig port was in-range, we try it first, then increment. If port exceeds upper bound, cycle back to min. What do you think?