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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 DA989C3A5A7 for ; Wed, 4 Sep 2019 09:31:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B853121670 for ; Wed, 4 Sep 2019 09:31:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729122AbfIDJbS (ORCPT ); Wed, 4 Sep 2019 05:31:18 -0400 Received: from orbyte.nwl.cc ([151.80.46.58]:50192 "EHLO orbyte.nwl.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727348AbfIDJbS (ORCPT ); Wed, 4 Sep 2019 05:31:18 -0400 Received: from n0-1 by orbyte.nwl.cc with local (Exim 4.91) (envelope-from ) id 1i5RdC-0006Yn-Rm; Wed, 04 Sep 2019 11:31:14 +0200 Date: Wed, 4 Sep 2019 11:31:14 +0200 From: Phil Sutter To: Florian Westphal Cc: Pablo Neira Ayuso , netfilter-devel@vger.kernel.org Subject: Re: [conntrack-tools PATCH] conntrack: Fix CIDR to mask conversion on Big Endian Message-ID: <20190904093114.GI25650@orbyte.nwl.cc> Mail-Followup-To: Phil Sutter , Florian Westphal , Pablo Neira Ayuso , netfilter-devel@vger.kernel.org References: <20190902164431.18398-1-phil@nwl.cc> <20190903203447.saqplkgbbxlajkqr@salvia> <20190904065356.GF25650@orbyte.nwl.cc> <20190904082128.GG13660@breakpoint.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190904082128.GG13660@breakpoint.cc> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Hi, On Wed, Sep 04, 2019 at 10:21:28AM +0200, Florian Westphal wrote: > Phil Sutter wrote: > > What we need in b is 'ff ff ff 00' for a prefix length of 24. Your > > suggested alternative does not compile, so I tried both options for the > > closing brace: > > > > | htonl((1 << 24) - 1) > > > > This turns into '00 ff ff ff' for both LE and BE, the opposite of what > > we need. > > > > | htonl((1 << 24)) - 1 > > > > This turns into '00 00 00 00' on LE and '00 ff ff ff' on BE. > > > > My code leads to correct result on either architecture and I don't see a > > simpler way of doing it. > > htonl(~0u << (32 - i)) would work, assuming i > 0 and <= 32. Ah, indeed! Left-shifting all-ones didn't come to mind. I'll send a v2. Thanks, Phil