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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 12559C34056 for ; Wed, 19 Feb 2020 19:12:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFC0C24670 for ; Wed, 19 Feb 2020 19:12:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582139551; bh=kR2N1xdoUxw+RxXMXGS4FbtBBxCzrowtQwH5BdvZY8A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=x6eHcXvEJ4XeodeINTOgaWc9Zve2XeJkCp+CGxccnLkGeM9OUvTplfWXf5zGQ4/Ha Q1G+03RW7+G9pAm3RCt3TiA8vWtdz0SrCL8GmNjuK72gpIEZVek2CrjrdlU5qbMSgQ 970K7nL4eRjmHeKBg9ebxf+qcCU4n1Vk40va2SfA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726811AbgBSTMb (ORCPT ); Wed, 19 Feb 2020 14:12:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:43406 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726647AbgBSTMa (ORCPT ); Wed, 19 Feb 2020 14:12:30 -0500 Received: from kicinski-fedora-PC1C0HJN (unknown [163.114.132.128]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id EB8142465D; Wed, 19 Feb 2020 19:12:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582139550; bh=kR2N1xdoUxw+RxXMXGS4FbtBBxCzrowtQwH5BdvZY8A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=SRcoVwQP2sUVT74AEEGDw4jPrHcnnFY6hCMnZsPXZYHeNhVYd2/Ej56nstdHYqBf0 nAawUfTy45xgvrUb/doSVq8tCxxTERMhtrDcLrRw7xJdlbiXhjWtwmIjmsJWLMU3s+ pXm2brUWoxVANtFqeLzp6SyryIuEllGCn8k5h+m8= Date: Wed, 19 Feb 2020 11:12:28 -0800 From: Jakub Kicinski To: Alexander Aring Cc: David Miller , kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, dav.lebrun@gmail.com, mcr@sandelman.ca, stefan@datenfreihafen.org, kai.beckmann@hs-rm.de, martin.gergeleit@hs-rm.de, robert.kaiser@hs-rm.de, netdev@vger.kernel.org Subject: Re: [PACTH net-next 5/5] net: ipv6: add rpl sr tunnel Message-ID: <20200219111228.024ac5ae@kicinski-fedora-PC1C0HJN> In-Reply-To: <20200219144137.omzmzgfs33fmb6yg@ryzen> References: <20200217223541.18862-1-alex.aring@gmail.com> <20200217223541.18862-6-alex.aring@gmail.com> <20200217.214713.1884483376515699603.davem@davemloft.net> <20200219144137.omzmzgfs33fmb6yg@ryzen> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 19 Feb 2020 09:41:37 -0500 Alexander Aring wrote: > On Mon, Feb 17, 2020 at 09:47:13PM -0800, David Miller wrote: > > From: Alexander Aring > > Date: Mon, 17 Feb 2020 17:35:41 -0500 > > > > > +struct rpl_iptunnel_encap { > > > + struct ipv6_rpl_sr_hdr srh[0]; > > > +}; > > > > We're supposed to use '[]' for zero length arrays these days. > > When I do that I get with gcc 9.2.1: > > linux/net/ipv6/rpl_iptunnel.c:16:25: error: flexible array member in a struct with no named members > 16 | struct ipv6_rpl_sr_hdr srh[]; > > This struct is so defined that a simple memcmp() can decide if it's the > same tunnel or not. We don't have any "named members" _yet_ but possible > new UAPI can introduce them. This seems risky, does C even allow empty structures like this? What's sizeof(struct rpl_iptunnel_encap) going to be? :S > Can we make an exception here? I can remove it but then I need to > introduce the same code again when we introduce new fields in UAPI for > this tunnel.