Public bug reported:

Systemd sometimes just doesn't resolve DNS queries and for the life of
me I don't know why.

So often when I'm switching between wifi networks I find that systemd-
resolved in 17.10 complete fails to do it's job. Here's the example. I'm
connected to the internet :

```
chalbersma@nebraska [~] {Tue Oct 31 20:58:18}        
> ping 8.8.8.8            
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.         
64 bytes from 8.8.8.8: icmp_seq=1 ttl=53 time=196 ms 
64 bytes from 8.8.8.8: icmp_seq=2 ttl=53 time=67.5 ms                           
                          
64 bytes from 8.8.8.8: icmp_seq=3 ttl=53 time=78.9 ms                           
                          
^C                        
--- 8.8.8.8 ping statistics ---                      
3 packets transmitted, 3 received, 0% packet loss, time 1999ms                  
                          
rtt min/avg/max/mdev = 67.534/114.169/196.025/58.068 ms
```

But I can't seem to resolve domains:

```
chalbersma@nebraska [~] {Tue Oct 31 20:59:17}        
> nslookup google.com
;; connection timed out; no servers could be reached

```

So I did a `systemd-resolver --status` to see if it's getting the right
dns server. It is :

```
Link 3 (wlp2s0)                                      
      Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6      
       LLMNR setting: yes                            
MulticastDNS setting: no                             
      DNSSEC setting: no                             
    DNSSEC supported: no                             
         DNS Servers: 192.168.43.1                   
                      2001:4888:51:ff00:506:d::      
                      2001:4888:50:ff00:500:d::

```

And it's actually up and working properly :

```
chalbersma@nebraska [~] {Tue Oct 31 21:02:06}
> nslookup google.com 192.168.43.1
Server:         192.168.43.1
Address:        192.168.43.1#53

Non-authoritative answer:
Name:   google.com
Address: 172.217.11.78
chalbersma@nebraska [~] {Tue Oct 31 21:03:16}
> nslookup google.com 2001:4888:51:ff00:506:d::
Server:         2001:4888:51:ff00:506:d::
Address:        2001:4888:51:ff00:506:d::#53

Non-authoritative answer:
Name:   google.com
Address: 172.217.11.78
```

Systemd just can't figure out to make the request. I did try the common
step of flushing the cache (with `--flush-cache`) restarting network-
manager and systemd-resolverd service but nothing seems to be able to
make systemd-resolverd function. Even a reboot doesn't always fix the
issue; sometimes it persists.

For debugging this is what's in my /etc/resolv.conf :

```  
chalbersma@nebraska [~] {Tue Oct 31 21:09:15} 
> cat /etc/resolv.conf                        
# Generated by NetworkManager                 
nameserver 127.0.1.1      
```

As soon as I manually set the nameserver from my loopback to the actual
dns server (bypassing systemd-resolvd) things start working again. Let
me know what kind of tshooting data I'd need to grab to help display
this issue.

In order to restore networking I had to manually edit that file and
change my dns to the external source.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: systemd-resolved

-- 
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https://bugs.launchpad.net/bugs/1729194

Title:
  Systemd-Resolvd Forgets to Resolv Request

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