Re: IPv6 static host address inside dynamic network

> Am 14.10.2024 um 04:58 schrieb Chris Ross <cross+openbsd@distal.com>:
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>> On Sep 3, 2024, at 16:48, Chris Ross <cross+openbsd@distal.com> wrote:
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>>> On Sep 3, 2024, at 10:28, Mike Fischer <fischer+obsd@lavielle.com> wrote:
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>>> There are two parts to this:
>>> - The IPv6 prefix.
>>> - The IID.
>>>
>>> The changes of the IPv6 prefix are generally triggered from the outside (Internet provider). So here some mechanism to notify about changes would be nice.
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> Okay. Many weeks later and I have a related question. I'm away from the "switching between routers" phase, and just have the one ever. But, the IPv6 network it advertises can change when my upstream delegates me a new one (via DHCPv6 IA_PD).
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> Looking, I think devd will let me monitor for this in FreeBSD 14, but not 13, and not other OSes. It looks like dhcpleasectl may be able to do this for me in OpenBSD. But, I haven't found anything portable.
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> So, I'm looking into writing a daemon that can be notified when the IPv6 network/address changes on an interface. But, I can't yet find a portable way. It looks like a PF_NETLINK socket can do this on FreeBSD and Linux, but that is not available in OpenBSD (7.5). How can I register interest in the address changes on a network interface in OpenBSD? Can this be done with PF_LINK or PF_ROUTE? (Just thinking randomly)
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> Obviously, polling is an option, but I'd rather be notified by the kernel when I need to.

I think the suggestion made by Florian Obser earlier in this thread makes a lot of sense.

And if you want to get away from scripting and directly interface with the notifications, the source code of the route(8) command would probably be a good place to look for how this is done.
https://cvsweb.openbsd.org/src/sbin/route/


I'd be interested in what you come up with.

Mike