Subject: Re: quick autoconf question

From: Thomas Narten <[email-masked]>
Date: Fri, 30 Jun 2000 15:28:46 -0400

Rich,

Maybe I misunderstand the issue, but it seems obvious that a node MUST
accept the NA. If it doesn't accept the NA, DAD won't work. I.e., you
rely on someone else returning an NA to indicate that the tentative
address is in use. If you discard it without processing it, the DAD
code won't see it either. What am I missing?

I think you do point out that the wording isn't perfect though. I.e.,
it should say, something like "accept packets whose IP destination
address is a tentative address".

I.e., the idea is that you accept/process NA/ND packets addressed to
tentative addresses, but silently discard all other packets addressed
to the tentative address.

Thomas
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From: Richard Draves <[email-masked]>
Date: Fri, 30 Jun 2000 11:35:30 -0700

I'm reviewing the latest TAHI test results. They've added some new tests for
autoconfiguration, and one of them raises a question.

If I receive a Neighbor Advertisement and the Destination Address in the
IPv6 header is a tentative address and the Target Address in the NA is the
same tentative address, should I process the NA (therefore concluding that
the address is a duplicate) or should I silently discard the NA?

In RFC 2462 it says:

   An address on which the duplicate Address Detection Procedure is
   applied is said to be tentative until the procedure has completed
   successfully.  A tentative address is not considered "assigned to an
   interface" in the traditional sense. That is, the interface must
   accept Neighbor Solicitation and Advertisement messages containing
   the tentative address in the Target Address field, but processes such
   packets differently from those whose Target Address matches an
   address assigned to the interface. Other packets addressed to the
   tentative address should be silently discarded.

The TAHI test says the NA should be silently discarded, and reading the
quoted paragraph closely it's not quite clear. It hinges on the word "Other"
in the last sentence.

Note that normally when when the Target Address is a tentative address, the
destination address is multicast (ff02::1 for NAs and solicited-node
multicast for NSs) so the answer only affects clever tests, not normal
operation.

Thanks,
Rich