Re: IPFilter 5 and IPv4-mapped IPv6 adresses

[is%netbsd.org@localhost]

On Thu, Jul 25, 2019 at 05:04:11PM +0200, Gert Doering wrote:
> 
> On Thu, Jul 25, 2019 at 01:39:47PM +0200, Joerg Sonnenberger wrote:
> > > That sounds like a bug to me; if nothing else, it makes it impossible
> > > to treat IPv4 packets differently from v4-mapped IPv6 packets.
> > There is nothing like a v4-mapped IPv6 packet.
> 
> Strictly speaking, if you happen to encounter an IPv6 packet on the
> wire with a v4-mapped address, you might want to discard that (because
> it should never show up). 
> But technically one could construct one...

I've seen them in the wild:

Some MPLS exit(?) node between work->us and outside, that tried to
send a hop count exceeded but but did not have any IPv6 address of
it's own, so it used the mapped address as the source address.  5-
letter-vendor, in case you wonder.

	-is