Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761614AbXEZPF4 (ORCPT ); Sat, 26 May 2007 11:05:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761320AbXEZPFs (ORCPT ); Sat, 26 May 2007 11:05:48 -0400 Received: from stinky.trash.net ([213.144.137.162]:60430 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754915AbXEZPFr (ORCPT ); Sat, 26 May 2007 11:05:47 -0400 Message-ID: <46584CC6.3020705@trash.net> Date: Sat, 26 May 2007 17:05:42 +0200 From: Patrick McHardy User-Agent: Debian Thunderbird 1.0.7 (X11/20051019) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ingo Oeser CC: Adam Osuchowski , Stephen Hemminger , bridge@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Bart De Schuymer Subject: Re: [Bridge] [BUG] Dropping fragmented IP packets within VLAN frames on bridge References: <20070525081750.5ba4a411@zonk.pl> <20070525174925.41bd6b2e@zonk.pl> <4657EC24.1030407@trash.net> <200705261621.00385.ioe-lkml@rameria.de> In-Reply-To: <200705261621.00385.ioe-lkml@rameria.de> X-Enigmail-Version: 0.93.0.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2684 Lines: 72 Ingo Oeser wrote: > On Saturday 26 May 2007, Patrick McHardy wrote: > >>net/8021q ignores the VLAN header overhead, so we should probably do the >>same here for consistency. Using IS_VLAN_IP (and IS_PPPOE_IP for current >>-rc) looks fine, additionally we should probably also check for >>skb->nfct != NULL to make sure that at least without connection tracking >>the bridge doesn't perform fragmentation. > > > And could we separe the conditions for that into a static helper function > explaining each of these conditions? e.g. sth. like that: The MTU checks are self-explanatory. Just a comment above the function stating that it tries to find out whether a packet needs to be refragmented because it was defragmented by IPv4 connection tracking and exceeds the MTU should be enough. > static bool br_nf_need_fragment(struct sk_buff *skb) > { > /* Plain IP packet does not fit in MTU */ > if (!(skb->protocol == htons(ETH_P_IP) && skb->len > skb->dev->mtu)) > return true; > > /* VLAN encapsulated IP packet does not fit in MTU */ > if (IS_VLAN_IP(skb) && skb->len > skb->dev->mtu - VLAN_HLEN) > return true; > > /* PPPoE encapsulated IP packet does not fit in MTU */ > if (IS_PPPOE_IP(skb) && skb->len > skb->dev->mtu - PPPOE_SES_HLEN) > return true; > > return false; > } As I said, I don't think we should account for the VLAN header overhead, the VLAN code itself doesn't even do it. And we should exclude packets that don't have a connection tracking reference attached since we are only undoing the damage connection tracking did by defragmenting it and should avoid fragmenting other packets as good as possible. > and then br_nf_dev_queue_xmit() becomes: > > static int br_nf_dev_queue_xmit(struct sk_buff *skb) > { > if (br_nf_need_fragment(skb) && !skb_is_gso(skb)) > return ip_fragment(skb, br_dev_queue_push_xmit); > else > return br_dev_queue_push_xmit(skb); > } > > which is much more readable, more documented and doesn't contain a condition monster :-) > > @Patrick: Could you check, wether the PPPoE case is correct? It looks OK. But there is another problem, ip_fragment doesn't care about the PPPoE overhead and produces a packet that will be too large after restoring the PPPoE header. A second __fake_rtable that accounts for the PPPoE overhead could probably fix that .. > What do you think? Should I submit a patch for that? Sure :) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/