From owner-freebsd-net@freebsd.org  Fri Mar 13 19:28:43 2020
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Date: Fri, 13 Mar 2020 20:28:33 +0100
From: Jan Behrens <jbe-mlist@magnetkern.de>
To: freebsd-net@freebsd.org
Subject: ifconfig prefer_source and IPv6 privacy extensions
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Dear all,

I'm using FreeBSD 12.1 with an ISP that supports IPv6. I have IPv6
privacy extensions enabled (ipv6_privacy="YES" in /etc/rc.conf which
sets net.inet6.ip6.prefer_tempaddr=1).

Given my router and ISP (who supports IPv6), my machine's FreeBSD
system assigns me 5 addresses through IPv6 autoconfiguration:

link-local:     fe80::<modified EUI-64>%<interface>
ULA:            fd<prefix>:<modified EUI-64>
ULA privacy:    fd<prefix>:<randomized>
Public:         2003:<prefix>:<modified EUI-64>
Public privacy: 2003:<prefix>:<randomized>

When I setup a static IPv6 address in the ULA range, such as
(fd<prefix>::2) and enable the "prefer_source" option (see man
ifconfig), the "prefer_source" option is ignored. It seems that
net.inet6.ip6.prefer_tempaddr=1 takes precedence.

Calling sysctl net.inet6.ip6.prefer_tempaddr=0 fixes my problem but
disables privacy extensions altogether (which I would like to keep
enabled).

Is it intended that "net.inet6.ip6.prefer_tempaddr" takes precedence
over "prefer_source"? If yes, why?


Kind regards,
Jan Behrens