Another systemd-resolved problem in 17.04

[Robert Heller]

At Thu, 22 Jun 2017 15:00:46 +0100 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> On Thu, Jun 22, 2017 at 08:40:45AM -0400, Tom H wrote:
> > On Thu, Jun 22, 2017 at 3:53 AM, Chris Green <cl at isbd.net> wrote:
> > > On Wed, Jun 21, 2017 at 06:07:54PM -0400, Tom H wrote:
> > >>
> > >> resolved is querying the wrong server because "fe80::..." is an ipv6
> > >> link-local address.
> > >>
> > >> Is there a log of when and/or why it became the dns server?
> > >
> > > The systemd-resolved set up on 17.04 has a local to the machine
> > > caching DNS so it could be right. It listens on 127.0.0.53 port 53.
> > >
> > > I don't quite understand why it's using IPV6 though, I thought I'd
> > > told everything not to use IPV6.
> > 
> > What I was asking was:
> > 
> > Is there a "Switching to DNS server ... fe80..." or "Switching to
> > fallback DNS server ... fe80..." in the log?
> > 
>     Jun 21 09:21:27 t470 systemd-resolved[961]: Transaction 13674 for <sync-445-us-west-2.sync.services.mozilla.com IN A> scope dns on wlp4s0/*.
>     Jun 21 09:21:27 t470 systemd-resolved[961]: Using feature level UDP+EDNS0+DO+LARGE for transaction 13674.
>     Jun 21 09:21:27 t470 systemd-resolved[961]: Using DNS server 192.168.1.2 for transaction 13674.
>     Jun 21 09:21:27 t470 systemd-resolved[961]: Sending query packet with id 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Timeout reached on transaction 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Retrying transaction 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Switching to DNS server fe80::1e74:dff:fe9d:5b1c%3 for interface wl p4s0.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Cache miss for sync-445-us-west-2.sync.services.mozilla.com IN A   
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Transaction 13674 for <sync-445-us-west-2.sync.services.mozilla.com IN A> scope dns on wlp4s0/*.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Using feature level UDP for transaction 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Using DNS server fe80::1e74:dff:fe9d:5b1c%3 for transaction 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Sending query packet with id 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Processing incoming packet on transaction 13674.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Transaction 13674 for <sync-445-us-west-2.sync.services.mozilla.com IN A> on scope dns on wlp4s0/* now complete with <rcode-failure> from network (unsigned).
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Freeing transaction 41827.
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Sent message type=error sender=n/a destination=:1.26631 object=n/a interface=n/a member=n/a cookie=106057 reply_cookie=2 error=Could not resolve 'sync-445-us-west-2.sync.services .mozilla.com', server or network returned error REFUSED
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Sent message type=method_call sender=n/a destination=org.freedeskto p.DBus object=/org/freedesktop/DBus interface=org.freedesktop.DBus member=RemoveMatch cookie=106058 reply_cooki e=0 error=n/a
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Got message type=method_return sender=org.freedesktop.DBus destinat ion=:1.22 object=n/a interface=n/a member=n/a cookie=79941 reply_cookie=106058 error=n/a
>     Jun 21 09:21:28 t470 systemd-resolved[961]: Freeing transaction 13674.
> 
> ... but why is it switching to a backup DNS server that I haven't specified anywhere?  Not to mention why is
> is it timing out, 192.168.1.2 is a system on the LAN with nothing else to do except DNS

Does 192.168.1.2 have a firewall set up?  Is it set up *correctly*?  Eg does 
it happen to block UDP port 53?

What is in the log file for 192.168.1.2?

The IP6 "backup" DNS might be "hard coded" into the DNS query logic somewhere 
as a "fall back" (or there might be an obscure conf file with that in it as a 
[default] "fall back".

> 

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