From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ashwanth Goli Subject: Re: ip6-in-ip{4,6} ipsec tunnel issues with 1280 MTU Date: Fri, 27 Apr 2018 16:32:06 +0530 Message-ID: References: <1524743477.2658.38.camel@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, maloney@google.com, edumazet@google.com, David Ahern , netdev-owner@vger.kernel.org To: Paolo Abeni Return-path: Received: from smtp.codeaurora.org ([198.145.29.96]:57596 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932754AbeD0LCH (ORCPT ); Fri, 27 Apr 2018 07:02:07 -0400 In-Reply-To: <1524743477.2658.38.camel@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 2018-04-26 17:21, Paolo Abeni wrote: > 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 Should I send out the following change as a patch? diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 2e891d2..c4c3313 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1235,7 +1235,7 @@ static int ip6_setup_cork(struct sock *sk, struct inet_cork_full *cork, if (np->frag_size) mtu = np->frag_size; } - if (mtu < IPV6_MIN_MTU) + if (!(rt->dst.flags & DST_XFRM_TUNNEL) && mtu < IPV6_MIN_MTU) return -EINVAL; cork->base.fragsize = mtu; if (dst_allfrag(xfrm_dst_path(&rt->dst)))