Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753628Ab3JFPg7 (ORCPT ); Sun, 6 Oct 2013 11:36:59 -0400 Received: from mail-ie0-f177.google.com ([209.85.223.177]:62713 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752719Ab3JFPg5 (ORCPT ); Sun, 6 Oct 2013 11:36:57 -0400 MIME-Version: 1.0 In-Reply-To: <20131006151351.GB9295@order.stressinduktion.org> References: <1380880333-3546-1-git-send-email-ou.ghorbel@gmail.com> <20131005140636.GA25076@order.stressinduktion.org> <20131006151351.GB9295@order.stressinduktion.org> Date: Sun, 6 Oct 2013 16:36:56 +0100 Message-ID: Subject: Re: [PATCH] Fix the upper MTU limit in ipv6 GRE tunnel From: Oussama Ghorbel To: Oussama Ghorbel , "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1733 Lines: 54 On Sun, Oct 6, 2013 at 4:13 PM, Hannes Frederic Sowa wrote: > On Sun, Oct 06, 2013 at 03:42:15PM +0100, Oussama Ghorbel wrote: >> The initialization in ip6gre_tnl_link_config is done as the following: >> static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu) >> { >> ... >> int addend = sizeof(struct ipv6hdr) + 4; >> ... >> /* Precalculate GRE options length */ >> if (t->parms.o_flags&(GRE_CSUM|GRE_KEY|GRE_SEQ)) { >> if (t->parms.o_flags&GRE_CSUM) >> addend += 4; >> if (t->parms.o_flags&GRE_KEY) >> addend += 4; >> if (t->parms.o_flags&GRE_SEQ) >> addend += 4; >> } >> ... >> dev->hard_header_len = rt->dst.dev->hard_header_len + addend; >> ... >> t->hlen = addend; >> .. >> } >> >> Unless they are other reasons, the hard_header_len is taken into >> account the GRE_KEY, GRE_SEQ .. > > But only if a new route is found. The hard_header_len reinitialization is > guarded by a (rt == NULL). We may have not found one on boot up. > In that case the function will make a return and hlen will be zero. Subtracting hlen in ip6gre_tunnel_change_mtu has no effect ... >> > To make this correct we would have to refactor the usage of the variables a >> > bit as is done in ipv4/ip_tunnel.c. The safest thing would be to leave this >> > check as-is currently although we exclude some allowed mtus. >> > >> > Perhaps you want to take a look how to achieve that? ;) >> > >> Why not, consistency is good ... > > Thanks, > > Hannes > Thanks, Oussama -- 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/