From: Ashwanth Goli <ashwanth@codeaurora•org>
To: David Ahern <dsahern@gmail•com>
Cc: Paolo Abeni <pabeni@redhat•com>,
netdev@vger•kernel.org, maloney@google•com, edumazet@google•com,
netdev-owner@vger•kernel.org
Subject: Re: ip6-in-ip{4,6} ipsec tunnel issues with 1280 MTU
Date: Fri, 27 Apr 2018 21:14:17 +0530 [thread overview]
Message-ID: <36807b4bda59b9145a69cc949facbb2b@codeaurora.org> (raw)
In-Reply-To: <b5b26603-199b-66e3-0576-ec4dfab9230f@gmail.com>
On 2018-04-27 20:18, David Ahern wrote:
> On 4/27/18 5:02 AM, Ashwanth Goli wrote:
>> 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.
>
> If you know you are running ipsec over the link why are you setting the
> outer MTU to 1280? RFC 2460 suggests the fragmentation of packets for
> links with MTU < 1280 should be done below the IPv6 layer:
>
> 5. Packet Size Issues
>
> IPv6 requires that every link in the internet have an MTU of 1280
> octets or greater. On any link that cannot convey a 1280-octet
> packet in one piece, link-specific fragmentation and reassembly must
> be provided at a layer below IPv6.
>
> Links that have a configurable MTU (for example, PPP links [RFC-
> 1661]) must be configured to have an MTU of at least 1280 octets; it
> is recommended that they be configured with an MTU of 1500 octets or
> greater, to accommodate possible encapsulations (i.e., tunneling)
> without incurring IPv6-layer fragmentation.
But is this not breaking point (b) from section 7.1 of RFC2473 since the
inner packet can be smaller than 1280.
https://tools.ietf.org/html/rfc2473#section-7.1
next prev parent reply other threads:[~2018-04-27 15:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <c3a1f2fc545b622bbb362e98313d7eba@codeaurora.org>
2018-04-26 11:51 ` ip6-in-ip{4,6} ipsec tunnel issues with 1280 MTU Paolo Abeni
2018-04-27 11:02 ` Ashwanth Goli
2018-04-27 14:48 ` David Ahern
2018-04-27 15:44 ` Ashwanth Goli [this message]
2018-04-29 1:05 ` David Ahern
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