svn commit: r239356 - head/sbin/dhclient

[Hajimu UMEMOTO]

Hi,

>>>>> On Thu, 23 Aug 2012 08:41:37 +0400
>>>>> Andrey Chernov <ache at FreeBSD.ORG> said:

ache> On Thu, Aug 23, 2012 at 12:27:46AM +0900, Hajimu UMEMOTO wrote:
> A link-local address has a scope; an interface here.  You cannot omit
> it on FreeBSD by default.  To be able to omit it, specify something
> like ipv6_default_interface="em0" in your /etc/rc.conf.

ache> Please enlighten me a bit. 
ache> RFC 4007 "11.6. Omitting Zone Indices" states:
ache>   "The format defined in this document does not intend to invalidate the
ache>    original format for non-global addresses; that is, the format without
ache>    the zone index portion.  As described in Section 6, in some common
ache>    cases with the notion of the default zone index, there can be no
ache>    ambiguity about scope zones.  In such an environment, the
ache>    implementation can omit the "%<zone_id>" part."

ache> Does absolutely trusted IPv6 local net using link-local addresses only 
ache> falls in that case? If yes, is there a way to make address scope optional 
ache> for all link-local addresses in FreeBSD?

FreeBSD doesn't have a feature to define a zone manually.
If a node has more than one interfaces, a link-local address without
zone identifer has ambiguity.  If you mean `all link-local addresses'
are within one interface, yes, you can omit zone identifer by setting
ipv6_default_interface'

ache> Are link-local addresses ever usable for DNS or not due to their 
ache> %<zone_id> part? F.e. for the case there is no global IPv6 net assigned at 
ache> all but pure isolated IPv6 local network.

> In anyway, I don't recommend to use a link-local address for DNS.

ache> Is it only due to their scope part or other reasons exists too?

As you saw, dig(1) and host(1) doesn't work well with a link-local
address.
Not only a zone identifier, but also some implementation may handle a
link-local address (fe80:: prefix) as special.

Sincerely,

--
Hajimu UMEMOTO
ume at mahoroba.org  ume@{,jp.}FreeBSD.org
http://www.mahoroba.org/~ume/