From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Abeni Subject: Re: ip6-in-ip{4,6} ipsec tunnel issues with 1280 MTU Date: Thu, 26 Apr 2018 13:51:17 +0200 Message-ID: <1524743477.2658.38.camel@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, maloney@google.com, edumazet@google.com, David Ahern To: Ashwanth Goli Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:50254 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755346AbeDZLvT (ORCPT ); Thu, 26 Apr 2018 07:51:19 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Hi, [fixed CC list] On Wed, 2018-04-25 at 21:43 +0530, Ashwanth Goli wrote: > Hi Pablo, Actually I'm Paolo, but yours is a recurring mistake ;) > I am noticing an issue similar to the one reported by Alexis Perez > [Regression for ip6-in-ip4 IPsec tunnel in 4.14.16] > > In my IPsec setup outer MTU is set to 1280, ip6_setup_cork sees an MTU > less than IPV6_MIN_MTU because of the tunnel headers. -EINVAL is being > returned as a result of the MTU check that got added with below patch. > > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/net/ipv6/ip6_output.c?h=v4.14.34&id=8278804e05f6bcfe3fdfea4a404020752ead15a6 > > Can we remove this MTU check since your recent patch [ipv6: the entire > IPv6 header chain must fit the first fragment] fixes a similar issue? AFAICS, RFC 2473 implies we can have MTU below 1280 for tunnel devices so we can probably relax the MTU check for such devices, but I think we would still need it in the general case. Cheers, Paolo