nd6 change and rc.d/network_ipv6 -> rc.d/netif integration

Kevin Oberman oberman at es.net
Mon Oct 5 18:54:13 UTC 2009

> From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des at des.no>
> Date: Mon, 05 Oct 2009 20:08:40 +0200
> Sender: owner-freebsd-current at freebsd.org
> Hiroki Sato <hrs at FreeBSD.org> writes:
> > John Hay <jhay at meraka.org.za> writes:
> > > Is there a good reason why we still ship with ipv6 off by default?
> > What do you mean by "off by default"?  I think IPv6 is not disabled by
> > default with the patch.
> % ident /usr/src/etc/defaults/rc.conf 
> /usr/src/etc/defaults/rc.conf:
>      $FreeBSD: head/etc/defaults/rc.conf 197619 2009-09-29 16:49:10Z dougb $
> % grep ipv6_network_interfaces /usr/src/etc/defaults/rc.conf
> ipv6_network_interfaces="none"	# List of IPv6 network interfaces
> #ipv6_network_interfaces="ed0 ep0"	# Examples for router
> % grep ipv6_prefer /usr/src/etc/defaults/rc.conf 
> ipv6_prefer="NO"	# Use IPv6 when both IPv4 and IPv6 can be used
> Does mean that IPv6 is disabled by default?  Who knows?  There is no
> coherent explanation *anywhere* of what these variables mean, and
> rc.conf(5) does not mention them at all.  In fact, the first hit for
> "ipv6" in rc.conf(5) is this:
>      ipv6_enable
>                  (bool) Enable support for IPv6 networking.  Note that this
>                  requires that the kernel has been compiled with options
>                  INET6.

Am I missing something here? From the same /etc/defaults/rc.conf:
### IPv6 options: ###
ipv6_enable="NO"		# Set to YES to set up for IPv6.

That looks about a "disabled out of the box" as it gets.

As far as I can see (which may not be far), ipv6_network_interfaces is
only relevant to IPv6 routing.

I believe that ipv6_prefer controls the default behavior when DNS returns
both IPv4 and IPv6 addresses for a host. If it is set to "NO", IPv4 will
be tried first (preferred). If set to "YES", the IPv6 address will be
preferred. I strongly recommend keeping ipv6_prefer set to "NO".
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman at es.net			Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4  EADA 927D EBB3 987B 3751

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