netdev - Re: Regression for ip6-in-ip4 IPsec tunnel in 4.14.16

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Date:   Wed, 07 Feb 2018 18:05:39 +0100
From:   Yves-Alexis Perez <corsac@...ian.org>
To:     Mike Maloney <maloney@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, debian-kernel@...ts.debian.org,
        Tobias Brunner <tobias@...ongswan.org>
Subject: Re: Regression for ip6-in-ip4 IPsec tunnel in 4.14.16

On Wed, 2018-02-07 at 17:38 +0100, Yves-Alexis Perez wrote:
> Starting with 4.14.16, IPv6 traffic is broken. When trying a simple ping
> to an IPv6 address I get:
> 
> ping: sendmsg: Invalid argument

I forgot an important bit of information: due to the way routers usually broke
path MTU discovery by filtering ICMP, I'm lowering the MTU to 1280 (so exactly
  IPV6_MIN_MTU) when using IPsec.

The MTU is configured by the IKE daemon (strongSwan, thus adding Tobias to
CC:) in routing table 220:

default via 192.168.28.254 dev eth0 proto static src 192.168.0.129 mtu 1280 advmss 1320

I'll try to printk the mtu before returning EINVAL to see why it's lower than
1280, but maybe the IP encapsulation is not correctly handled?

Regards,
-- 
Yves-Alexis
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