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

Michael Richardson <mcr+ietf@sandelman.ca> Sun, 05 November 2017 01:32 UTC

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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: Mikael Abrahamsson <swmike@swm.pp.se>
cc: "C. M. Heard" <heard@pobox.com>, 6man WG <ipv6@ietf.org>
Subject: Re: Updating to RFC6434 to deal with 8200-style header insertion by IPIP
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Date: Sat, 04 Nov 2017 21:32:29 -0400
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Mikael Abrahamsson <swmike@swm.pp.se>; wrote:
    >>> 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).

    > Sure, but if the device understands IPSEC but has it turned off, what
    > should it do?

    > I don't know.

Exactly.
Depends entirely on what "turned off" means.
Probably it means that the SPI# is not configured.
For ESP, dropping the packet makes sense, because you can't decrypt and you
can't know what's "beyond" the ESP without knowing the parameters (so even
ESP_NULL encryption can't be skipped).

But, AH has the property that we *know* it's not encrypted, and we know the
size of everything, and so we can just skip things if the integrity check is
not for us.

If we can gotten that right, we could have used AH for multicasted traffic,
and even for some interesting uses where we want to authenticate that things
went through certain routers.


-- 
Michael Richardson <mcr+IETF@sandelman.ca>;, Sandelman Software Works
 -= IPv6 IoT consulting =-