[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

** No longer affects: maas

** No longer affects: nplan (Ubuntu)

** No longer affects: systemd (Ubuntu)

** Changed in: cloud-init
   Status: New => Confirmed

** Changed in: cloud-init
   Importance: Undecided => Medium

** Changed in: cloud-init
 Assignee: (unassigned) => Ryan Harper (raharper)

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Dan Watkins]

On Thu, Mar 08, 2018 at 04:30:30PM -, Scott Moser wrote:
> I'm pretty sure that if you you rm /etc/resolv.conf
> and then just write what ever you want in there, it wont get overritten.
> 
> mv /etc/resolv.conf /etc/resolv.conf.dist
> echo "nameserver 8.8.8.8" > /etc/resolv.conf

Apologies, I thought I was replying to another "DNS resolution in bionic
doesn't work" bug. >.<

(That said, systemd-resolved does own /etc/resolv.conf, so it _could_
rewrite it.  An example would be when the search domain changes, but
that's unlikely in a MAAS environment.)

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

I'm pretty sure that if you you rm /etc/resolv.conf
and then just write what ever you want in there, it wont get overritten.

mv /etc/resolv.conf /etc/resolv.conf.dist
echo "nameserver 8.8.8.8" > /etc/resolv.conf


On Thu, Mar 8, 2018 at 4:36 PM, Mike Pontillo 
wrote:

> We discussed this today and decided that the proper place to fix this is
> not in MAAS; the v1 YAML containing global DNS servers should be
> converted to equivalent valid Netplan (using a heuristic).
>
> Alternatively, global DNS could be added to the Netplan schema (possibly
> as a shortcut to apply configuration to a group of interfaces).
>
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>
> Title:
>   [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
>   leads to no DNS resolution
>
> To manage notifications about this bug go to:
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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Mike Pontillo]

We discussed this today and decided that the proper place to fix this is
not in MAAS; the v1 YAML containing global DNS servers should be
converted to equivalent valid Netplan (using a heuristic).

Alternatively, global DNS could be added to the Netplan schema (possibly
as a shortcut to apply configuration to a group of interfaces).

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

** Changed in: maas
   Importance: High => Medium

** Changed in: maas
   Status: Won't Fix => Triaged

** Changed in: maas
   Importance: Medium => Low

** Changed in: maas
Milestone: None => 2.4.x

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Mike Pontillo]

** Changed in: maas
   Status: Triaged => Won't Fix

** Changed in: maas
 Assignee: Mike Pontillo (mpontillo) => (unassigned)

** Changed in: maas
Milestone: 2.4.0alpha2 => None

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Jason Hobbs]

Ok, that's not much of a workaround then :).

On Thu, Mar 8, 2018 at 3:52 AM, Dan Watkins
 wrote:
> On Wed, Mar 07, 2018 at 11:42:29PM -, Jason Hobbs wrote:
>> Is there a workaround for this? I can just rm /etc/resolv.conf and
>> create it with the contents I want, right?
>
> Yep, though you'll need to recreate it every so often as it will be
> replaced.
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1750884
>
> Title:
>   [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
>   leads to no DNS resolution
>
> Status in cloud-init:
>   New
> Status in MAAS:
>   Triaged
> Status in nplan package in Ubuntu:
>   New
> Status in systemd package in Ubuntu:
>   New
>
> Bug description:
>   When deploying Bionic, /etc/resolv.conf is not configured correctly,
>   which leads to no DNS resolution. In the output below, you will see
>   that netplan config is correctly to the 10.90.90.1 nameserver, but in
>   resolv.conf that's a local address.
>
>   Resolv.conf should really be configured to use the provided DNS
>   server(s). That said, despite that fact, DNS resolution doesn't work
>   with the local address.
>
>   Bionic
>   --
>
>   ubuntu@node01:~$ cat /etc/netplan/50-cloud-init.yaml
>   # This file is generated from information provided by
>   # the datasource.  Changes to it will not persist across an instance.
>   # To disable cloud-init's network configuration capabilities, write a file
>   # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
>   # network: {config: disabled}
>   network:
>   version: 2
>   ethernets:
>   enp0s25:
>   match:
>   macaddress: b8:ae:ed:7d:17:d2
>   mtu: 1500
>   nameservers:
>   addresses:
>   - 10.90.90.1
>   search:
>   - maaslab
>   - maas
>   set-name: enp0s25
>   bridges:
>   br0:
>   addresses:
>   - 10.90.90.3/24
>   gateway4: 10.90.90.1
>   interfaces:
>   - enp0s25
>   parameters:
>   forward-delay: 15
>   stp: false
>   ubuntu@node01:~$ cat /etc/resolv.conf
>   # This file is managed by man:systemd-resolved(8). Do not edit.
>   #
>   # 127.0.0.53 is the systemd-resolved stub resolver.
>   # run "systemd-resolve --status" to see details about the actual 
> nameservers.
>   nameserver 127.0.0.53
>
>   search maaslab maas
>   ubuntu@node01:~$ ping google.com
>   ping: google.com: Temporary failure in name resolution
>
>   [...]
>
>   ubuntu@node01:~$ sudo vim /etc/resolv.conf
>   ubuntu@node01:~$ cat /etc/resolv.conf
>   # This file is managed by man:systemd-resolved(8). Do not edit.
>   #
>   # 127.0.0.53 is the systemd-resolved stub resolver.
>   # run "systemd-resolve --status" to see details about the actual 
> nameservers.
>   nameserver 10.90.90.1
>
>   search maaslab maas
>   ubuntu@node01:~$ ping google.com
>   PING google.com (172.217.0.174) 56(84) bytes of data.
>   64 bytes from mia09s16-in-f14.1e100.net (172.217.0.174): icmp_seq=1 ttl=52 
> time=4.46 ms
>   64 bytes from mia09s16-in-f14.1e100.net (172.217.0.174): icmp_seq=2 ttl=52 
> time=4.38 ms
>
>   =
>   Xenial
>   ==
>
>   ubuntu@node05:~$ cat /etc/network/interfaces.d/50-cloud-init.cfg
>   # This file is generated from information provided by
>   # the datasource.  Changes to it will not persist across an instance.
>   # To disable cloud-init's network configuration capabilities, write a file
>   # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
>   # network: {config: disabled}
>   auto lo
>   iface lo inet loopback
>   dns-nameservers 10.90.90.1
>   dns-search maaslab maas
>
>   auto enp0s25
>   iface enp0s25 inet static
>   address 10.90.90.162/24
>   gateway 10.90.90.1
>   mtu 1500
>   ubuntu@node05:~$ cat /etc/resolv.conf
>   # Dynamic resolv.conf(5) file for glibc resolver(3) generated by 
> resolvconf(8)
>   # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
>   nameserver 10.90.90.1
>   search maaslab maas
>
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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Dan Watkins]

On Wed, Mar 07, 2018 at 11:42:29PM -, Jason Hobbs wrote:
> Is there a workaround for this? I can just rm /etc/resolv.conf and
> create it with the contents I want, right?

Yep, though you'll need to recreate it every so often as it will be
replaced.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Jason Hobbs]

Is there a workaround for this? I can just rm /etc/resolv.conf and
create it with the contents I want, right?

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

Currently maas sends v1 config to cloud-init. cloud-init converts
that to netplan.  MAAS could certainly change change to either
a.) improve the v1 config that it sends to put dns as per-interface
b.) send v2 config with dns per-interface.

I don't think there is reason to justify either of those at this time.

I do think that at some point MAAS network configuration will be
hindered and they'll end up wanting to describe dns more eloquently.
That time is not yet upon us.

Mathieu, you tell us how to indicate global dns in netplan configuration
and cloud-init will make sure it gets through to netplan correctly.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Mathieu Trudel-Lapierre]

Whether or not /e/n/i supports something correctly or just happens to
work by sheer luck has no bearing on what is technically correct and
sensical -- let's abstract this, what we need to concern ourselves with
here is netplan, cloud-init and maas.

In the network world, it is absolutely true that DNS nameservers only
make sense on a per-interface basis: nothing guarantees that a
"globally-set" nameserver of 8.8.8.8 is reachable through all
interfaces. It just happens to be that way on 99% of systems because
they only connect to one network, through one interface.

So, in light of the nameserver setting in MaaS under Settings being
unspecified, there's /no other way/ but to either set the nameserver
globally or try to guess the right interface (either by which is
connected to MaaS, or which gets the default gateway, or which matches
subnets). None of the detection options I could come up with strike me
as particularly solid and foolproof.

Next steps for netplan strike me as being to add support for global
nameservers even if it's silly; we shouldn't expect users to have to
have the level of knowledge of networking to know to set it up on a
particular interface when it will work correctly as "global" for 99% of
cases.

In MaaS, my opinion is that every effort should be taken to allow
network administrators to set things up correctly -- nothing guarantees
that the systems deployed will remain accessible to MaaS, or that it
will be their main interface to the network. Only allowing global DNS is
brittle at best, and breaks at least what *I* have been taught were best
practices, to have a separate "public" network from the authenticated
"private" side where monitoring and/or deployment happens. Maybe I'm
just the one who's particular in doing this.

I'm not sure what next steps are for cloud-init -- given a valid
configuration, I assumed it should just pass it through to netplan if
it's v2.

I'll take care of the "global DNS" implementation in netplan.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Mike Pontillo]

I don't want to change the v1 YAML in MAAS to output per-interface DNS,
because this risks causing a change of behavior in pre-netplan
deployments. It seems this is necessary in Netplan, but it isn't clear
to me that this is correct. I think it's valuable to take a step back
and look at the requirements here. With DNS resolution being a system-
wide function, is it really correct for it to be associated with a
particular interface? If I think about the user stories, it's:

 - I want to use a specific DNS server to resolve DNS names for a particular 
forward or reverse domain.
 - I want the set of configured DNS servers to be symmetrical with enabled 
interfaces. (In other words, if I have a DMZ interface and an internal 
interface, I might want queries for *.example.com to hit 10.0.0.2, but I want 
queries for anything else to hit 8.8.8.8.)

Somewhat of a tangent here, but don't like search lists. That just makes
DNS names ambiguous. If my search list is 'example.com', now when I type
"foo.com", the resolver has to decide whether I meant
"foo.com.example.com" or just plain "foo.com". I don't want a /search/
list. I want a /match/ list. (But that sounds like a separate bug.)

Back to the current problem: if we blindly configure global default DNS
servers on interfaces that can't reach them, we risk that resolvconf
will calculate an incorrect global configuration. That is, the MAAS
administrator might have expected that the per-interface configuration
take precedence over the default configuration. Would having default
configuration inside an interface cause it to take priority?

Then again, I'm not entirely clear on what the expected behavior is
here, even for the v1 YAML. If I specify global DNS servers *and* per-
interface DNS servers (for a subset of interfaces), is there an
unambiguous way to render that in /e/n/i?

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Steve Langasek]

On Fri, Feb 23, 2018 at 04:09:07AM -, Andres Rodriguez wrote:
> On Thu, Feb 22, 2018 at 10:30 PM Scott Moser 
> wrote:

> > Getting this fixed in cloud-init is tricky.
> > In ifupdown (/etc/network/interfaces) world, we just took the "global dns"
> > entries and put them on the loopback device (lo).  Since that device would
> > always be brought up, and never really brought down, it served its purpose.

> > That is what Ryan tried above, but it doesnt seem to work.  Even if it
> > *did* work, the solution would be systemd-networkd specific, and cloud-
> > init doesn't speak to systemd-networkd or systemd-resolved.  It speaks
> > to netplan.  So we would still need a way for cloud-init to tell netplan
> > to do this.

> > That leaves us with 2 not-so-great solutions in cloud-init only:
> > a.) blindly put global dns entries on *all* interfaces
> > b.) cloud-init search through the config and find the "right" interface to
> > put the global dns entry on.

> This is the same issue we are facing in MAAS. Unless a user specifies a
> specific set of dns servers on a subnet, which is not always the case, then
> MAAS doesn’t know which interface the dns servers belong to.

> I believe this is one of the reasons why the “global” config was used,
> because effectively, the DNS server doesn’t really “belong” to a specific
> interface.

> So we either sent it to all, interfaces or pick a “best” interface, which
> is not the best approach either.

> As per mpontillo’s config, this has the likelihood to break dns
> resolution.

> That said, maybe option 3 would be to put th dns on the interface which the
> default routes will be going through...

Yes, and option 3 was what I previously recommended when mpontillo raised
this issue in .

Given that cloud-init itself has some notion of a "global" DNS server in v1
yaml, I think its v2 yaml renderer should apply the same logic.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Dimitri John Ledkov]

If we don't know, then maybe things should be passed to netplan, in a way for 
it to generate global resolved config? as in, create
/run/systemd/resolved.conf.d/global.conf

[Resolve]
DNS=999.999.999.999
(Maybe FallbackDNS=, if we want it to leave DNS= setting for users to tweak)

Or whatnot, which should then appear in systemd-resolve --status, Global
section which is applied as a fallback if an interface does not have a
per-interface DNS settings.

Could somebody try dropping dns configs out of netplan file that is
generated, rerun apply, check that systemd-resolve --status  has
nothing, then add above drop-in with the right dns server, restart
resolved, and check if that picks up a global DNS server, and if network
resolution works correctly? *globally*

I also wonder, if .network / .link files should have an ability to
specify Global DNS settings for resolved...

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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Re: [Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

On Thu, Feb 22, 2018 at 10:30 PM Scott Moser 
wrote:

> Getting this fixed in cloud-init is tricky.
> In ifupdown (/etc/network/interfaces) world, we just took the "global dns"
> entries and put them on the loopback device (lo).  Since that device would
> always be brought up, and never really brought down, it served its purpose.
>
> That is what Ryan tried above, but it doesnt seem to work.  Even if it
> *did* work, the solution would be systemd-networkd specific, and cloud-
> init doesn't speak to systemd-networkd or systemd-resolved.  It speaks
> to netplan.  So we would still need a way for cloud-init to tell netplan
> to do this.
>
> That leaves us with 2 not-so-great solutions in cloud-init only:
> a.) blindly put global dns entries on *all* interfaces
> b.) cloud-init search through the config and find the "right" interface to
> put the global dns entry on.
>

This is the same issue we are facing in MAAS. Unless a user specifies a
specific set of dns servers on a subnet, which is not always the case, then
MAAS doesn’t know which interface the dns servers belong to.

I believe this is one of the reasons why the “global” config was used,
because effectively, the DNS server doesn’t really “belong” to a specific
interface.

So we either sent it to all, interfaces or pick a “best” interface, which
is not the best approach either.

As per mpontillo’s config, this has the likelihood to break dns
resolution.

That said, maybe option 3 would be to put th dns on the interface which the
default routes will be going through...


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>
> Title:
>   [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
>   leads to no DNS resolution
>
> To manage notifications about this bug go to:
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>
> Launchpad-Notification-Type: bug
> Launchpad-Bug: product=cloud-init; status=New; importance=Undecided;
> assignee=None;
> Launchpad-Bug: product=maas; milestone=2.4.0alpha2; status=Triaged;
> importance=High; assignee=mike.ponti...@canonical.com;
> Launchpad-Bug: distribution=ubuntu; sourcepackage=nplan; component=main;
> status=New; importance=Critical; assignee=None;
> Launchpad-Bug: distribution=ubuntu; sourcepackage=systemd; component=main;
> status=New; importance=Critical; assignee=None;
> Launchpad-Bug-Information-Type: Public
> Launchpad-Bug-Private: no
> Launchpad-Bug-Security-Vulnerability: no
> Launchpad-Bug-Commenters: andreserl cyphermox dean raharper smoser xnox
> Launchpad-Bug-Reporter: Andres Rodriguez (andreserl)
> Launchpad-Bug-Modifier: Scott Moser (smoser)
> Launchpad-Message-Rationale: Subscriber
> Launchpad-Message-For: andreserl
>
-- 
Andres Rodriguez (RoAkSoAx)
Ubuntu Server Developer
MSc. Telecom & Networking
Systems Engineer

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

Getting this fixed in cloud-init is tricky.
In ifupdown (/etc/network/interfaces) world, we just took the "global dns" 
entries and put them on the loopback device (lo).  Since that device would 
always be brought up, and never really brought down, it served its purpose.

That is what Ryan tried above, but it doesnt seem to work.  Even if it
*did* work, the solution would be systemd-networkd specific, and cloud-
init doesn't speak to systemd-networkd or systemd-resolved.  It speaks
to netplan.  So we would still need a way for cloud-init to tell netplan
to do this.

That leaves us with 2 not-so-great solutions in cloud-init only:
a.) blindly put global dns entries on *all* interfaces
b.) cloud-init search through the config and find the "right" interface to put 
the global dns entry on.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

** Changed in: maas
   Importance: Low => High

** Changed in: maas
 Assignee: (unassigned) => Mike Pontillo (mpontillo)

** Changed in: maas
Milestone: None => 2.4.0alpha2

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Ryan Harper]

I gave the "loopback" trick a go like so:

root@b1:~# cat /etc/systemd/network/10-netplan-lo.network 
[Match]
Name=lo

[Network]
Address=127.0.0.1
DNS=10.90.90.1
Domains=maaslab maas
root@b1:~# networkctl status --all
● 1: lo
   Link File: n/a
Network File: /etc/systemd/network/10-netplan-lo.network
Type: loopback
   State: carrier (configured)
 Address: 127.0.0.1
  ::1
 DNS: 10.90.90.1
  Search Domains: maaslab
  maas

● 38: eth0
   Link File: n/a
Network File: /run/systemd/network/10-netplan-eth0.network
Type: ether
   State: routable (configured)
  HW Address: 00:16:3e:4c:5b:4b (Xensource, Inc.)
 Address: 10.8.107.71
  fe80::216:3eff:fe4c:5b4b
 Gateway: 10.8.107.1
 DNS: 10.8.107.1
  Search Domains: lxd
root@b1:~# systemd-resolve --status --no-pager 
Global
  DNSSEC NTA: 10.in-addr.arpa
  16.172.in-addr.arpa
  168.192.in-addr.arpa
  17.172.in-addr.arpa
  18.172.in-addr.arpa
  19.172.in-addr.arpa
  20.172.in-addr.arpa
  21.172.in-addr.arpa
  22.172.in-addr.arpa
  23.172.in-addr.arpa
  24.172.in-addr.arpa
  25.172.in-addr.arpa
  26.172.in-addr.arpa
  27.172.in-addr.arpa
  28.172.in-addr.arpa
  29.172.in-addr.arpa
  30.172.in-addr.arpa
  31.172.in-addr.arpa
  corp
  d.f.ip6.arpa
  home
  internal
  intranet
  lan
  local
  private
  test

Link 38 (eth0)
  Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
   LLMNR setting: yes
MulticastDNS setting: no
  DNSSEC setting: no
DNSSEC supported: no
 DNS Servers: 10.8.107.1
  DNS Domain: lxd


networkctl processed the .network file but systemd-resolved didn't seem to 
notice it.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Dean Henrichsmeyer]

Let's make sure this is fixed for bionic. The scope of nameservers has
changed and maas should do the right thing.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

** Changed in: maas
   Importance: Undecided => Low

** Changed in: maas
   Status: Invalid => Triaged

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

@Scott,

Sure, we can all improve but I just want to note one thing. The "Silly"
config that MAAS sends to curtin is valid config. That yields valid
configuration in Xenial. Since Curtin is now passing the /same/
configuration to cloud-init, cloud-init is not generating valid
configuration in Bionic. Despite the fact that theres a "global" DNS,
there's also DNS defined for the bridge, but cloud-init is not writing
the bridge config correctly.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Dimitri John Ledkov]

In terms of expectations on bionic:

1) /etc/resolv.conf should be a symlink to ../run/systemd/resolve/stub-
resolv.conf

2) The contents should point at `nameserver 127.0.0.53` and list search
domains, if any are available. I.e. the contents shown in the bug
description is correct.

3) The nameservers are now preferred to be on the per-interface basis,
thus e.g. nameserver should be declared on the interface that has the
default route. Indeed sending "global" configs is loss of information
about networking.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

It seems to me that each of maas, cloud-init and netplan could do better
here.

a.) maas declares 'global' nameserver/dns info.
this is kind of silly in that such a thing doesn't really exist.
maas has the information necessary to declare the nameserver on the
device with the address that has a route to it.

b.) cloud-init is currently sticking that global definition on an
interface that doesnt have an address.  so cloud-init could do better.

c.) netplan or systemd-networkd could realize enp0s25 interface is "up"
and that it should have its nameservers used.

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

@Matthieu,

ubuntu@node01:~$ systemd-resolve google.com
google.com: resolve call failed: No appropriate name servers or networks for 
name found

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

MAAS is sending a "global" nameserver, and a ethernet device on a bridge.
cloud-init is rendering that nameserver onto the ethernet device rather
than on the bridge or as a "global" entry.


$ cat my.yaml
network:
  config: [
   {"id": "enp0s25", "type": "physical", "name": "enp0s25",
"mac_address": "b8:ae:ed:7d:16:d0", "mtu": 1500,
"subnets": [{"type": "manual"}]},
   {"id": "br0", "type": "bridge", "name": "br0",
"mac_address": "b8:ae:ed:7d:16:d0", "bridge_interfaces": ["enp0s25"],
"mtu": 1500, "params": {'bridge_fd': 15, 'bridge_stp': 0},
"subnets": [
   {"type": "static", "address": "10.90.90.4/24", "dns_nameservers": [],
"gateway": "10.90.90.1"}
 ]},
   {"type": "nameserver", "address": ["10.90.90.1"],
"search": ["maaslab", "maas"]},
  ]
  version: 1

$ PYTHONPATH=$PWD python3 ./tools/net-convert.py \
   --network-data=my.yaml  --kind=yaml --output-kind=netplan --directory=out.d

$ cat out.d/etc/netplan/50-cloud-init.yaml

network:
version: 2
ethernets:
enp0s25:
match:
macaddress: b8:ae:ed:7d:16:d0
mtu: 1500
nameservers:
addresses:
- 10.90.90.1
search:
- maaslab
- maas
set-name: enp0s25
bridges:
br0:
addresses:
- 10.90.90.4/24
gateway4: 10.90.90.1
interfaces:
- enp0s25
parameters:
forward-delay: 15
stp: false

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Mathieu Trudel-Lapierre]

Why aren't the nameservers set under the br0 interface, if the interface
is supposed to be in a bridge?

The /e/n/i config and netplan configs here are not equivalent. I expect
that systemd-resolved should be happy with the config as it is anyway,
but this may be a special case where systemd thinks the interface is not
really up?

If you run 'systemd-resolve google.com', what happens?

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

@Mathieu,

Good catch.

@Scott:

Network config MAAS sent is correect, it is the same config sent to
xenial: https://pastebin.canonical.com/p/rjBgzKjdxR/

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Andres Rodriguez]

ubuntu@node03:~$ systemd-resolve --status --no-pager
Global
  DNSSEC NTA: 10.in-addr.arpa
  16.172.in-addr.arpa
  168.192.in-addr.arpa
  17.172.in-addr.arpa
  18.172.in-addr.arpa
  19.172.in-addr.arpa
  20.172.in-addr.arpa
  21.172.in-addr.arpa
  22.172.in-addr.arpa
  23.172.in-addr.arpa
  24.172.in-addr.arpa
  25.172.in-addr.arpa
  26.172.in-addr.arpa
  27.172.in-addr.arpa
  28.172.in-addr.arpa
  29.172.in-addr.arpa
  30.172.in-addr.arpa
  31.172.in-addr.arpa
  corp
  d.f.ip6.arpa
  home
  internal
  intranet
  lan
  local
  private
  test

Link 3 (br0)
  Current Scopes: LLMNR/IPv4 LLMNR/IPv6
   LLMNR setting: yes
MulticastDNS setting: no
  DNSSEC setting: no
DNSSEC supported: no

Link 2 (enp0s25)
  Current Scopes: none
   LLMNR setting: yes
MulticastDNS setting: no
  DNSSEC setting: no
DNSSEC supported: no
 DNS Servers: 10.90.90.1
  DNS Domain: maaslab
  maas

** Description changed:

  When deploying Bionic, /etc/resolv.conf is not configured correctly,
  which leads to no DNS resolution. In the output below, you will see that
  netplan config is correctly to the 10.90.90.1 nameserver, but in
  resolv.conf that's a local address.
  
  Resolv.conf should really be configured to use the provided DNS
- server(s)
+ server(s). That said, despite that fact, DNS resolution doesn't work
+ with the local address.
  
  Bionic
  --
  
  ubuntu@node01:~$ cat /etc/netplan/50-cloud-init.yaml
  # This file is generated from information provided by
  # the datasource.  Changes to it will not persist across an instance.
  # To disable cloud-init's network configuration capabilities, write a file
  # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
  # network: {config: disabled}
  network:
  version: 2
  ethernets:
  enp0s25:
  match:
  macaddress: b8:ae:ed:7d:17:d2
  mtu: 1500
  nameservers:
  addresses:
  - 10.90.90.1
  search:
  - maaslab
  - maas
  set-name: enp0s25
  bridges:
  br0:
  addresses:
  - 10.90.90.3/24
  gateway4: 10.90.90.1
  interfaces:
  - enp0s25
  parameters:
  forward-delay: 15
  stp: false
  ubuntu@node01:~$ cat /etc/resolv.conf
  # This file is managed by man:systemd-resolved(8). Do not edit.
  #
  # 127.0.0.53 is the systemd-resolved stub resolver.
  # run "systemd-resolve --status" to see details about the actual nameservers.
  nameserver 127.0.0.53
  
  search maaslab maas
  ubuntu@node01:~$ ping google.com
  ping: google.com: Temporary failure in name resolution
  
- 
  [...]
- 
  
  ubuntu@node01:~$ sudo vim /etc/resolv.conf
  ubuntu@node01:~$ cat /etc/resolv.conf
  # This file is managed by man:systemd-resolved(8). Do not edit.
  #
  # 127.0.0.53 is the systemd-resolved stub resolver.
  # run "systemd-resolve --status" to see details about the actual nameservers.
  nameserver 10.90.90.1
  
  search maaslab maas
  ubuntu@node01:~$ ping google.com
  PING google.com (172.217.0.174) 56(84) bytes of data.
  64 bytes from mia09s16-in-f14.1e100.net (172.217.0.174): icmp_seq=1 ttl=52 
time=4.46 ms
  64 bytes from mia09s16-in-f14.1e100.net (172.217.0.174): icmp_seq=2 ttl=52 
time=4.38 ms
  
  =
  Xenial
  ==
  
  ubuntu@node05:~$ cat /etc/network/interfaces.d/50-cloud-init.cfg
  # This file is generated from information provided by
  # the datasource.  Changes to it will not persist across an instance.
  # To disable cloud-init's network configuration capabilities, write a file
  # /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with the following:
  # network: {config: disabled}
  auto lo
  iface lo inet loopback
  dns-nameservers 10.90.90.1
  dns-search maaslab maas
  
  auto enp0s25
  iface enp0s25 inet static
  address 10.90.90.162/24
  gateway 10.90.90.1
  mtu 1500
  ubuntu@node05:~$ cat /etc/resolv.conf
  # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
  # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
  nameserver 10.90.90.1
  search maaslab maas

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[Bug 1750884] Re: [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic, leads to no DNS resolution

[Scott Moser]

Hi,

cloud-init has never updated resolv.conf directly.
/etc/resolv.conf in 16.04 is managed via resolvconf through 
/etc/network/interfaces.
/etc/resolv.conf in 18.04 is managed via systemd-resolve (netplan -> 
systemd-networkd -> systemd-resolve).

Can you provide the content of:
   systemd-resolve --status --no-pager

And does this happen in the ephemeral environment, the installed
environment, or both?

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Title:
  [2.4, bionic] /etc/resolv.conf not configured correctly in Bionic,
  leads to no DNS resolution

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