DNS resolution stops working after some time

[Akash Rawal]

DNS resolution stops working after sometime (usually 10-20 minutes) in Lubuntu 15.10

The problem can be temporarily corrected after restarting network-manager using systemctl, but it starts again after 10-20 minutes. Looks like network-manager is not configuring dnsmasq properly.

Output from 'nslookup google.com':
~~~~~
Server: 127.0.1.1
Address: 127.0.1.1#53

** server can't find google.com: REFUSED
~~~~~

Output from 'tcpdump -i lo port 53' while running above command:
~~~~~
20:16:59.235879 IP localhost.38045 > comp0.arhome.info.domain: 28529+ A? google.com. (28)
20:16:59.286851 IP comp0.arhome.info.domain > localhost.38045: 28529 Refused 0/0/0 (28)
~~~~~

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: network-manager 1.0.4-0ubuntu5.1
ProcVersionSignature: Ubuntu 4.2.0-18.22-generic 4.2.3
Uname: Linux 4.2.0-18-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CRDA:
 country IN: DFS-JP
  (2402 - 2482 @ 40), (N/A, 20), (N/A)
  (5170 - 5250 @ 80), (N/A, 20), (N/A)
  (5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS
  (5735 - 5835 @ 80), (N/A, 20), (N/A)
CurrentDesktop: LXDE
Date: Wed Dec 2 20:14:32 2015
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2015-09-25 (68 days ago)
InstallationMedia: Lubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
IpRoute:
 default via 172.16.84.1 dev wlan0 proto static metric 600
 172.16.84.0/22 dev wlan0 proto kernel scope link src 172.16.84.50 metric 600
 200.1.1.2 via 172.16.84.1 dev wlan0 proto dhcp metric 600
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
SourcePackage: network-manager
UpgradeStatus: Upgraded to wily on 2015-11-06 (25 days ago)
nmcli-dev:
 DEVICE TYPE STATE DBUS-PATH CONNECTION CON-UUID CON-PATH
 wlan0 wifi connected /org/freedesktop/NetworkManager/Devices/1 nn0.arhome.info bab29dc2-8a79-4170-8253-277286712124 /org/freedesktop/NetworkManager/ActiveConnection/0
 eth0 ethernet unavailable /org/freedesktop/NetworkManager/Devices/2 -- -- --
 vboxnet0 ethernet unmanaged /org/freedesktop/NetworkManager/Devices/3 -- -- --
 lo loopback unmanaged /org/freedesktop/NetworkManager/Devices/0 -- -- --
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Akira Tanaka (popo1897)]

I have the same problem when using Ubuntu 16.04.
After I disabled dnsmasq in /etc/NetworkManager/NetworkManager.conf, the name resolution and the Internet connection works fine.

[Thomas Hood (jdthood)]

This possibly arises from bug #1003842.

What is possibly happening: the second or third nameserver on the list of available nameservers supplied to dnsmasq replies quickly to dnsmasq's query with a negative answer and dnsmasq immediately passes that negative answer back to the resolver.

When dnsmasq is not used, the resolver tries the first nameserver on the list first, only trying the second nameserver after a timeout period.

If this is the problem then the "correct" solution is to fix the malfunctioning nameserver or to remove it from the list.