NetworkManager with dnsmasq caching NXDOMAIN response of router

From	David Ayers <ayers@fsfe.org>
Newsgroups	linux.debian.user
Subject	NetworkManager with dnsmasq caching NXDOMAIN response of router
Date	2024-07-08 01:20 +0200
Message-ID	<IXJkJ-yNn-1@gated-at.bofh.it> (permalink)
Organization	linux.* mail to news gateway

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Hello everyone!

My Debian 12/bookworm laptop uses DHCP with NetworkManager which
produce an /etc/resolv.conf containing:
# Generated by NetworkManager
```
search home
nameserver 192.168.1.254
```

I've setup NetworkManager to use its local dnsmasq instance to add
additional name resolution for libvirt and a VPN, according to [1].
My /etc/NetworkManager/conf.d/localdns.conf contains:
```
[main]
dns=dnsmasq
```
and my /etc/NetworkManager/dnsmasq.d/local_dnsmasq.conf contains
```
server=/virt/192.168.122.1
server=/122.168.192.in-addr.arpa/192.168.122.1
server=/vpn/10.70.71.1
server=/71.70.10.in-addr.arpa/10.70.71.1
log-queries
```

The name resolutions (and reverse resolutions) for the the *.vpn and
*.virt work just fine.  But I'm having issues with the *.home domain as
soon as set the dns=dnsmasq in /etc/NetworkManager/conf.d/localdns.conf
independent of any entries in
/etc/NetworkManager/dnsmasq.d/local_dnsmasq.conf

After starting (or restarting) NetworkManager either with 
```
sudo systemctl reload NetworkManager.service
```
or with
```
sudo nmcli general reload dns-full
```
the name resolution works twice for anyhost.home in the local domain
but subsequently fails with NXDOMAIN.

Here ist the output of the log-queries output for a successful 
```
ping -c 1 nas-server.home
PING nas-server.home (192.168.1.103) 56(84) bytes of data.
64 bytes from nas-server.home (192.168.1.103): icmp_seq=1 ttl=64 time=7.47 ms
```
with the corresponding
```
sudo tail -f /var/log/syslog
TS HOST systemd[1]: Reloaded NetworkManager.service - Network Manager.
TS HOST dnsmasq[169260]: query[A] nas-server.home from 127.0.0.1
TS HOST dnsmasq[169260]: forwarded nas-server.home to 192.168.1.254
TS HOST dnsmasq[169260]: query[AAAA] nas-server.home from 127.0.0.1
TS HOST dnsmasq[169260]: forwarded nas-server.home to 192.168.1.254
TS HOST dnsmasq[169260]: reply nas-server.home is 192.168.1.103
TS HOST dnsmasq[169260]: reply nas-server.home is NXDOMAIN
TS HOST dnsmasq[169260]: query[PTR] 103.1.168.192.in-addr.arpa from 127.0.0.1
TS HOST dnsmasq[169260]: forwarded 103.1.168.192.in-addr.arpa to 192.168.1.254
TS HOST dnsmasq[169260]: reply 192.168.1.103 is nas-server.home
```
Notice the IPv6 AAAA query and the two replies with the FQDN.

The first subsequent query succeeds again with:
```
ping -c 1 nas-server.home
ping: nas-server.home: Name or service not known
```
with the corresponding
```
sudo tail -f /var/log/syslog
TS HOST dnsmasq[171213]: query[A] nas-server.home from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server.home is NXDOMAIN
TS HOST dnsmasq[171213]: query[AAAA] nas-server.home from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server.home is NXDOMAIN
TS HOST dnsmasq[171213]: query[A] nas-server from 127.0.0.1
TS HOST dnsmasq[171213]: forwarded nas-server to 192.168.1.254
TS HOST dnsmasq[171213]: query[AAAA] nas-server from 127.0.0.1
TS HOST dnsmasq[171213]: forwarded nas-server to 192.168.1.254
TS HOST dnsmasq[171213]: reply nas-server is 192.168.1.103
TS HOST dnsmasq[171213]: reply nas-server is NXDOMAIN
TS HOST dnsmasq[171213]: query[PTR] 103.1.168.192.in-addr.arpa from 127.0.0.1
TS HOST dnsmasq[171213]: forwarded 103.1.168.192.in-addr.arpa to 192.168.1.254
TS HOST dnsmasq[171213]: reply 192.168.1.103 is nas-server.home
```
Notice that the FQDN caches with NXDOMAIN are followed up with just the
host name and the same two replies, one with the IP and the other with
NXDOMAIN.

But all subsequent queries will fail with:
```
ping -c 1 nas-server.home
ping: nas-server.home: Name or service not known
```
with the corresponding
```
TS HOST dnsmasq[171213]: query[A] nas-server.home from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server.home is NXDOMAIN
TS HOST dnsmasq[171213]: query[AAAA] nas-server.home from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server.home is NXDOMAIN
TS HOST dnsmasq[171213]: query[A] nas-server from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server is NXDOMAIN
TS HOST dnsmasq[171213]: query[AAAA] nas-server from 127.0.0.1
TS HOST dnsmasq[171213]: cached nas-server is NXDOMAIN
```

Once I restart/reload NetworkManager (i.e. clear the cache) I get two
successful name resolutions with subsequent requests failing again.

I do notice that when querying external domains, they seem to return
NODATA-IPv6 instead of NXDOMAIN for what I assume are the AAAA queries.
But I have no control of that my ZTE based ISP suppired router will
reply for the AAAA queries.  I suppose, that the router is returning
the wrong reply for its own local domain for AAAA queries.

So I guess my question is, can I tell dnsmasq somehow not to cache
NXDOMAIN or interpret it as NODATA-IPv6 for queries to the *.home
domain?

Any other suggestions are also welcome!

And in case this isn't it, where is the correct mailing list, to pose
suche a question?

Thanks, anyone!
David

[1] https://networkmanager.dev/docs/api/latest/NetworkManager.conf.html
-- 
David Ayers

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Thread

NetworkManager with dnsmasq caching NXDOMAIN response of router David Ayers <ayers@fsfe.org> - 2024-07-08 01:20 +0200
  Re: NetworkManager with dnsmasq caching NXDOMAIN response of router jeremy ardley <jeremy.ardley@gmail.com> - 2024-07-08 06:10 +0200
    Re: NetworkManager with dnsmasq caching NXDOMAIN response of router David Ayers <ayers@fsfe.org> - 2024-07-08 12:00 +0200
      Re: NetworkManager with dnsmasq caching NXDOMAIN response of router Detlef Vollmann <dv@vollmann.ch> - 2024-07-10 15:20 +0200
        Re: NetworkManager with dnsmasq caching NXDOMAIN response of router Greg Wooledge <greg@wooledge.org> - 2024-07-10 15:20 +0200
          Re: NetworkManager with dnsmasq caching NXDOMAIN response of router songbird <songbird@anthive.com> - 2024-07-11 01:00 +0200
  Re: NetworkManager with dnsmasq caching NXDOMAIN response of router jeremy ardley <jeremy.ardley@gmail.com> - 2024-07-08 05:50 +0200
  Re: NetworkManager with dnsmasq caching NXDOMAIN response of router Michael Kjörling <c9bc136c6063@ewoof.net> - 2024-07-08 09:50 +0200

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