Re: Updating to RFC6434 to deal with 8200-style header insertion by IPIP

"C. M. Heard" <heard@pobox.com> Thu, 02 November 2017 15:26 UTC

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From: "C. M. Heard" <heard@pobox.com>
Date: Thu, 2 Nov 2017 08:26:29 -0700
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Subject: Re: Updating to RFC6434 to deal with 8200-style header insertion by IPIP
To: 6man WG <ipv6@ietf.org>
Cc: Michael Richardson <mcr+ietf@sandelman.ca>, Mikael Abrahamsson <swmike@swm.pp.se>
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On Thu, Nov 2, 2017, Michael Richardson <mcr+ietf@sandelman.ca>; wrote:

>
> C. M. Heard <heard@pobox.com>; wrote:
>     > On Wed, 01 Nov 2017, Michael Richardson wrote:
>     >> Yet we skip other extension headers in order to find the ULP.
>
>     > Not so. An end node that encounters an unrecognized extension header
> is
>
> Both AH and IPIP are well known and recognized extension headers.
>

Not to a node that does not have any IPsec code at all (or that has IPsec
turned off).

 On Wed, 1 Nov 2017, Mikael Abrahamsson wrote:

>
>    > If the device isn't configured to do IPsec (even by default), then I don't
>    > think it should do what you describe.
>
> Yet we skip other extension headers in order to find the ULP.
> In fact, a host that has *NO* IPsec code *at all* will skip it as an unknown
> header....  Because we got this wrong, we couldn't use AH to secure ND or any
> other multicast (like OSPF) without causing of a flag day.  AH became totally
> USELESS.  It was sad.
>
>
> Right. I forgot that IPSEC is an extension header in IPv6, I tought of it as
> something that was encapsulated. So I take back what I said.


No, you were right the first time. Unknown extension headers are not
skipped; they cause the packet to be discarded (see RFC 8200, Sec 4).

Mike Heard