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Re: Enabling SLAAC for IPv6 by default

On 25/09/2018 16:40, Greg Troxel wrote:
Roy Marples <> writes:

He's specifically talking about temporary addresses.
dhcpcd enables stable private addresses by default instead.

I am not quite following, and will assume I'm not the only one - so a
few questions trying to be precise.

I am unable to find any documentation of use_tempaddr and
prefer_tempaddr under /usr/share/man.

Is the "temp_addr" sysctl about "SLAAC privacy extensions", changing
behavior of the in-kernel stateless autoconfiguration client, such that
if not set, the MAC address is used to form the host part, and if set,
forming the host part randomly?

The MAC address forming the host part is still created.
A temporary address where the host part is random is *also* created.

What is the lifetime of the addresses formed by the kernel when enabled?
Are we following the recommendation of 1 day as preferred and 7 days as

sysctls net.inet6.ip6.temppltime and net.inet6.ip6.tempvltime are used to calculate the lifetimes based on the lifetime of the actual address.

Is there a mechanism to keep such addresses (marked deprecrated) until
they are no longer in use (well, bound)?  I checked a few Mac machines,
and they seem to keep "deprecated" addresses around for varying
intervals.  Or simply the expiration at the end of the valid lifetime?

They will vanish when the lifetime expires.
This is my real issue, they are useless for persistent connections.

I checked one each netbsd-7 and netbsd-8, configured for dhcpcd, and
they have both link-local (fe80::) and global v6 addresses that do not
appear to have been formed from the MAC address.

dhcpcd generates stable private addresses - not temporary addresses.
These are a different beast and a better solution than temporary addresses.
See RFC 7217.

Do we know if there are mechanisms to keep temporary addresses in
deprecated state while ?in use"?

Even if in use, they vanish when expired.
See my above issue.


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