Re: [PATCH v12 3/9] arp/ndp: send ARP announcement / unsolicited NA when neigbour entry added

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Oct 09, 2025 at 09:29:12PM +0200, Stefano Brivio wrote:
> On Thu, 9 Oct 2025 14:51:02 +1100
> David Gibson <david@gibson.dropbear.id.au> wrote:
> > On Wed, Oct 08, 2025 at 12:01:18PM +0200, Stefano Brivio wrote:
> > > On Wed, 8 Oct 2025 11:27:32 +1100
> > > David Gibson <david@gibson.dropbear.id.au> wrote:
[snip]
> > > but that wasn't the case, hence (I think) the
> > > current struggle. If we go in that direction, I hope it's possible.  
> > 
> > Thinking a bit more closely, I don't think it is, for much the same
> > reason it wasn't in this draft.
> > 
> > According to the rules Jon and I thrashed out elsewhere in the thread,
> > there are certain guest side addresses that must be locked to use
> > our_tap_mac.  We're essentially shadowing something that might exist
> > on the host side, so we should use our MAC not the MAC of whatever is
> > shadowed.
> > 
> > Just pre-populating an entry won't do the trick, because it could be
> > overwritten if the right events occur for the shadowed host.
> 
> Right, sorry, I omitted another bit of context: I've been suggesting to
> Jon that he'd introduce some kind of "permanent" or "administrative"
> bit, and keep those entries at the beginning of the chain, exactly for
> the reason you mention.

Ah, right.  Yes, that's a good idea.

> I can imagine we'll need those at some point if we ever want to offer
> explicit link-layer address mapping in the future, and they're probably
> convenient the day one can change map_guest_addr and map_host_loopback
> at runtime.
> 
> We can also happily skip that for the moment, though, it's another
> problem we can keep for later.

Right.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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