Re: [babel] Dummy source address [was: I-D Action: draft-ietf-babel-v4viav6-01.txt]

Juliusz Chroboczek <jch@irif.fr> Wed, 14 April 2021 12:31 UTC

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Date: Wed, 14 Apr 2021 14:31:45 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
To: Donald Eastlake <d3e3e3@gmail.com>
Cc: Babel at IETF <babel@ietf.org>
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Subject: Re: [babel] Dummy source address [was: I-D Action: draft-ietf-babel-v4viav6-01.txt]
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>> 1. reuse the 4rd dummy address, as David suggested, repurposing it
>>    to be a generic dummy address?

>> 3. define a cross-protocol dummy address in this draft?

> I don't think (3) exceeds our scope. We need a facility. So we specify
> it in our draft. And, just in passing, we are liberal and say others
> can use it. There is no need to make a big point of it being
> "cross-protocol" and no need to name any other routing protocol(s).

Donald, could you please check RFC 7600, because I'm wondering if that's
not what they have done already.  Here are the relevant quotations:

Section 4.8:

   R-22: If a CE or BR receives an ICMPv6 error message [RFC4443], it
         MUST synthesize an ICMPv4 error packet [RFC792].  This packet
         MUST contain the first 8 octets of the discarded packet's IP
         payload.  The reserved IPv4 dummy address (192.0.0.8/32; see
         Section 6) MUST be used as its source address.

IANA Considerations:

   o  Reserved IPv4 address 192.0.0.8/32 to be used as the "IPv4 dummy
      address" (Section 4.8).

So I'm pretty tempted to say "MAY use 192.0.0.8 if no more suitable IPv4
address is available", as David originally suggested, and see what the
IESG says.

-- Juliusz