[ntp:hackers] IPv6 ntp-dev replying with wrong source address?

Danny Mayer mayer at gis.net
Wed Jul 9 18:43:42 PDT 2003


At 07:59 PM 7/9/03, Frederick Bruckman wrote:
>On Wed, 9 Jul 2003, David Malone wrote:
>
> > I've a few FreeBSD machine running ntp-dev from about the 7th of
> > June. I noticed that one of the machines was ignoring replies from
> > another. The machine that is sending the reply has two global
> > unicast IPv6 addresses and seems to be replying with with the
> > wrong one:
> >
> > transmit: at 69 
> 2001:bb0:dd0:cc01::2->2001:770:68:1ff:202:b3ff:fe65:604b mode 3
> > receive: at 69 2001:bb0:dd0:cc01::2<-2001:770:68:ff::1 mode 4 code 3
> >
> > I guess it is possible this has been fixed since then?
>
>RFC 3484 makes it clear that source address selection is the job of
>the OS. Moreover, FreeBSD seems to be doing the right thing here by
>choosing the manually configured address over the auto-configured
>address (assuming they're on the same interface). RFC 3484 also says
>the OS is supposed to let you configure the rules for choosing, yet
>no OS actually lets you do that yet, as far as I know.
>
>The "bug" in ntpd is that it's not recognizing the two addresses as
>coming from the same host. Of course, there's no conceivable way that
>ntpd *could* glean that information from the addresses alone, which is
>what I believe it tries to do now. It'd need some other source for the
>information, like DNS (somewhat analogously to MX records).

>Can't you just configure the other machine to use 2001:770:68:ff::1?

If you mean in ntpd there's no support yet for that. If you mean the O/S then
maybe.

Danny

>Frederick
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