[conspire] missing rDNS for (intentionally missing) IPv6

[Nick Moffitt]

On 24Feb2021 09:09pm (-0800), Rick Moen wrote:
> I was thus truly surprised (and still am) to find that my server
> suddenly had an IPv6 address after the unplanned restart of yesterday --
> because nothing in /etc/ even mentions that address.

One of the storied advantages of IPv6, back when it still seemed fresh, was that autoconfiguration did not require special DHCP daemons polling the network: the kernel could autoconfigure IPv6 itself!

These days that seems less a feature and more a vulnerability, but I ran across it on my own virtual server.

The trouble is that the IPv6 autoconfig address I was given was part of a /64 with all other customers of my provider, which meant that I got royally tarred-by-association with a number of rather high-volume mail delivery systems that had a blasé attitude toward the GDPR.  Fortunately my provider was happy to give me my own /64 to play with, and I allocated ...::1 from it and thought I'd go on my merry way.

But no!  The autoconfiguration kept finding the old IP and routing through it.  Eventually I needed to set it back up in my netplan configs (I'm trying to be Modern these days, you see) and set it "lifetime: 0" so that it wouldn't keep popping up in the routing table.

And having my own /64 means that now my IPv4 address is in some bogus "blackhole the whole /24" lists, but my IPv6 address is truly mine and reflects only the mail my system sends.  So if that turns out to appear on some RBLs I'll at least know it wasn't just a noisy neighbour, I guess.