Re: [PATCH] tap: Don't update ip6.addr_seen to ::

[Stefano Brivio <sbrivio@redhat.com>]

On Tue, 16 May 2023 10:36:11 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> When we receive packets from the tap side, we update the addr_seen fields
> to reflect the last known address of the guest or ns.  For ip4.addr_seen
> we, sensibly, only update if the address we've just seen isn't 0 (0.0.0.0).
> This case can occur during early DHCP transactions.
> 
> We have no equivalent case for IPv6.  We're less likely to hit this,
> because DHCPv6 uses link-local addresses, however we can see an source
> address of :: with certain multicast operations.  This can bite us if we
> try to make an incoming connection very early after starting pasta with
> --config-net: we may have only seen some of those multicast packets,
> updated addr_seen to :: and not had any "real" packets to update it to a
> global address.  I've seen this with some of the avocado test conversions.

It looks like I haven't stared at enough packet captures yet...

> In any case, it can never make sense to update addr_seen to ::, so
> explicitly exclude that case.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Applied.

-- 
Stefano