> On Sep 2, 2024, at 18:30, Mike Fischer <fischer+o...@lavielle.com> wrote:
>
> To my knowledge there is no mechanism or hook to trigger when the public IPv6
> prefix changes. (It would be nice to have such a mechanism though.)
Yeah. I see rtsold has a couple scripts it knows how to run, so that is a
place. But having a hook in slaacd(8) (or somewhere else?) would be nice.
Heck, I’d love to be able to configure “these are my IIDs for this interface”
in a conf file. That would be a little mixed between “autoconfiguration”
and manual though I guess.
Please speak up if you also think it would be valuable to have slaacd
configuration for either multiple IIDs for an interface, or a hook script
to be called when receiving and applying a RA.
> The following (adjust for your interface) is one way to extract the current
> public IPv6 prefix:
> $interface='em0'
> slaacctl show interface "$interface" \
> | grep 'prefix:' \
> | grep -v 'prefix: fd' \
> | cut -d' ' -f2 \
> | awk -F'::/' '{print substr($1,1,19)}'
I think this will not work when the network changes. Right now I see
two matches for that, one from the router I’m building which is getting
its IPv6 from a different location than the prior/current gateway.
I have the “new” network from that advertisement last night, with a
lifetime of 0. With some effort, I could write something to parse
slaacctl output with more thought. But, I’m not wholly sure I’d be
able to know enough about what the possible outputs mean.
> If you have static Interface IDs (IIDs, the lower 64 bits of the IPv6
> address) then once you have determined that your prefix has changed you can
> trigger actions such updating DDNS, reconfiguring services listening on a
> specific public IPv6 address, etc.
>
> I use this in my /etc/hostname.if files to get a static IID with the current
> public IPv6 prefix:
> inet6 autoconf -temporary -soii
> This generates an EUI64 IID based on the MAC address.
I only have “inet6 autoconf” for the same purpose. Then, after sleeping
a few seconds, a couple of “inet6 alias” lines for the static secondary
addresses. But, of course, that only works for the historic static
IPv6 network I am moving away from.
Thanks for your thoughts!
