From owner-cvs-src@FreeBSD.ORG Tue Dec 12 14:34:36 2006 Return-Path: X-Original-To: cvs-src@FreeBSD.org Delivered-To: cvs-src@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id DAEDA16A505; Tue, 12 Dec 2006 14:34:35 +0000 (UTC) (envelope-from ticso@cicely12.cicely.de) Received: from raven.bwct.de (raven.bwct.de [85.159.14.73]) by mx1.FreeBSD.org (Postfix) with ESMTP id 385F9443D0; Tue, 12 Dec 2006 14:16:46 +0000 (GMT) (envelope-from ticso@cicely12.cicely.de) Received: from cicely5.cicely.de ([10.1.1.7]) by raven.bwct.de (8.13.4/8.13.4) with ESMTP id kBCEI8nL044486; Tue, 12 Dec 2006 15:18:08 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (cicely12.cicely.de [10.1.1.14]) by cicely5.cicely.de (8.13.4/8.13.4) with ESMTP id kBCEI0Jj043194 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 12 Dec 2006 15:18:00 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (localhost [127.0.0.1]) by cicely12.cicely.de (8.13.4/8.13.3) with ESMTP id kBCEI03v074924; Tue, 12 Dec 2006 15:18:00 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: (from ticso@localhost) by cicely12.cicely.de (8.13.4/8.13.3/Submit) id kBCEHxjn074923; Tue, 12 Dec 2006 15:17:59 +0100 (CET) (envelope-from ticso) Date: Tue, 12 Dec 2006 15:17:59 +0100 From: Bernd Walter To: Luigi Rizzo Message-ID: <20061212141759.GZ54209@cicely12.cicely.de> References: <200612081036.kB8AakMD029277@repoman.freebsd.org> <20061212131333.GU54209@cicely12.cicely.de> <20061212055756.A61182@xorpc.icir.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061212055756.A61182@xorpc.icir.org> X-Operating-System: FreeBSD cicely12.cicely.de 5.4-STABLE alpha User-Agent: Mutt/1.5.9i X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED=-1.8, BAYES_00=-2.599 autolearn=ham version=3.1.7 X-Spam-Checker-Version: SpamAssassin 3.1.7 (2006-10-05) on cicely12.cicely.de Cc: Luigi Rizzo , src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org, imp@FreeBSD.org, ticso@cicely.de Subject: Re: cvs commit: src/sys/net if_ethersubr.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: ticso@cicely.de List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Dec 2006 14:34:36 -0000 On Tue, Dec 12, 2006 at 05:57:56AM -0800, Luigi Rizzo wrote: > On Tue, Dec 12, 2006 at 02:13:34PM +0100, Bernd Walter wrote: > > On Fri, Dec 08, 2006 at 10:36:46AM +0000, Luigi Rizzo wrote: > > > luigi 2006-12-08 10:36:45 UTC > > > > > > FreeBSD src repository > > > > > > Modified files: > > > sys/net if_ethersubr.c > > > Log: > > > Fix an oscure bug triggered by a recent change in kern_socket.c. > > > The symptoms were that outgoing DHCP requests for diskless kernels > > > had the IP header corrupt. After long investigations, the source of > > > the problem was found in ether_output() - for SIMPLEX interfaces > > > and broadcast traffic, a copy of the packet is passed back to the kernel > > > through if_simloop(). However if_simloop() modifies the mbuf, while > > > the copy obtained through m_copym() is a readonly one. > > > > > > The bug has been there forever, but it has been triggered only recently > > > by a change in sosend_dgram() which passed down mbufs with sufficient > > > space to prepend the header. > > > > > > This fix is trivial - use m_dup() instead of m_copy() to create > > > the copy. As an alternative, we could try and modify if_simloop() > > > to play safely with readonly mbufs, but i don't think it is worthwhile > > > because 1) this is a relatively infrequent code path so we do not need > > > to worry too much about performance, and 2) the cost of doing an > > > extra m_pullup in if_simloop() is probably the same as doing the > > > copy of the cluster, anyways. > > > > This change produces an alignment panic on arm. > > Reverting it gets my system back to live. > > then i suppose the proper fix is to revert to m_copy() and > work on if_simloop() so that 1. it handles a readonly chain, and > 2. when doing so, it passes up a properly aligned packet... Can't comment on this, as I don't have enough knowledge about network code. According to the xscale report it was likely never properly aligned, the alignment obviously just moved with your change. > however note that there is already some code in net/if_loop.c::if_simloop(), > just that it uses this: > > #if defined(__ia64__) || defined(__sparc64__) > /* > * Some archs do not like unaligned data, so > * we move data down in the first mbuf. > */ > if (mtod(m, vm_offset_t) & 3) { > KASSERT(hlen >= 3, ("if_simloop: hlen too small")); > bcopy(m->m_data, > (char *)(mtod(m, vm_offset_t) > - (mtod(m, vm_offset_t) & 3)), > m->m_len); > m->m_data -= (mtod(m,vm_offset_t) & 3); > } > #endif > to detect whether the architecture is alignment-sensitive. > Is there any other identifier that we can use to check ? I wonder how many of these are missing __arm__? -- B.Walter http://www.bwct.de http://www.fizon.de bernd@bwct.de info@bwct.de support@fizon.de