Date: Wed, 28 Jul 2004 22:54:31 +0200 From: Brad Knowles <brad@stop.mail-abuse.org> To: FreeBSD-CURRENT Mailing List <freebsd-current@freebsd.org> Subject: Re: Problems with ntp4.2 when names resolve to IPv6 addresses Message-ID: <p06002000bd2d9429e65e@[192.168.50.233]> In-Reply-To: <20040728145738.GA47187@walton.maths.tcd.ie> References: <20040726012016.D232E5D0A@ptavv.es.net> <p0600201bbd2c7d596650@[192.168.50.233]> <20040728145738.GA47187@walton.maths.tcd.ie>
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[Retransmitting from correct e-mail address. -Brad]
At 3:57 PM +0100 2004-07-28, David Malone wrote:
> Ntpd has some issues in this area. It will always try the first
> address returned by getaddrinfo and doesn't fall back to other
> addresses if things don't work out. This means if you don't have
> IPv6 connectivity, but your server does have an AAAA record, then
> you probably won't be able to talk NTP to the server. The fix is
> to change ntp.conf to say "server -4 server.name" rather than just
> "server server.name".
If this were true, then pool.ntp.org would be totally and
completely useless. If the initial connection attempt fails or times
out, the next IP address in sequence should be used. However, I
don't know how the switch-over from IPv6 to IPv4 works.
Once ntpd has latched onto a particular number, it won't use any
others. Nor will it re-resolve the name into IP addresses, which
makes a DNS rotor like pool.ntp.org somewhat less useful.
What I'd like to see happen is to have ntpd latch onto all the
advertised IP addresses for a given server, and at least contact all
of them. If they really are different, then they should be used
separately -- kind of like the OpenNTPd "servers" directive.
> (The same problem exists with servers with multiple IPv4 addresses,
> some of which are unreachable, it's just less obvious...)
So far as I know, we're not doing anything unusual with regards
to resolving IP addresses or switching from one advertised address to
the next. If you've got IP stack problems, that's an issue we may
not be able to help with.
--
======================================================================
Brad Knowles, <brad@stop.mail-abuse.org>
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
-Benjamin Franklin, Historical Review of Pennsylvania.
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