Re: [DNA] [Issue 15] [Issue 16] DAD and MLD Interaction

[Erik Nordmark <erik.nordmark@sun.com>]

Greg Daley wrote:

> Should this be tied to the Link-Up indications, or to the DNA reception
> and processing of hints?
> 
> For example, if no link-layer indication is received does the
> reception of an 'unexpected' RA and subsequent initiation of
> DNA operations cause Optimistic to be set?
> 
> I'd guess it's tied to DNA initiation, rather than the Link-Up
> explicitly.

Things wouldn't work safely from a DAD perspective if there is no 
link-up notification.

Take an example:
1. Host moves and attaches to link B (no link-up notification)
2. Host receives a NS for it's link-local address. It responds since it
    isn't aware that it might have moved to a different link.
3. Host receives an unsolicited RA, which has some 'unexpected' things
    in it (e.g., only unknown prefixes). This triggers DNA; move
    addresses to optimistic state and send RS.

The issue is that if the link-local address is a duplicate on the new 
link, then at #2 the host would mess up things for the existing user of 
that link-local address on the new link.

So things can't be very robust without a link-up notification.

    Erik