QtCreator is flooding the system with DNS queries

[Pat McGowan]

I started QtCreator and my system hung completely during startup, so I hard rebooted.
When I started QtCreator again I was unable to access the network, and the syslog was full of
dnsmasq[6046]: Maximum number of concurrent DNS queries reached (max: 150)

I deleted the device-i386 LXD container which also seemed to cause this if it was running without starting QtCreator. Running QtCreator after deleting this still causes the flood of queries.

ubuntu-sdk-ide: 3.5.4~144+201607250738~ubuntu16.04.1

[Pat McGowan (pat-mcgowan)]

Syslog when starting ubuntu-sdk-ide

Aug 11 17:16:22 samsung930X3G systemd[1]: Starting LXD - network bridge...
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.7956] manager: (lxdbr0): new Bridge device (/org/freedesktop/NetworkManager/Devices/3)
Aug 11 17:16:22 samsung930X3G systemd-udevd[8668]: Could not generate persistent MAC address for lxdbr0: No such file or directory
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: Joining mDNS multicast group on interface lxdbr0.IPv4 with address 10.0.1.1.
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: New relevant interface lxdbr0.IPv4 for mDNS.
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: Registering new address record for 10.0.1.1 on lxdbr0.IPv4.
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: Joining mDNS multicast group on interface lxdbr0.IPv6 with address fe80::f4dd:30ff:fe16:9c5f.
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: New relevant interface lxdbr0.IPv6 for mDNS.
Aug 11 17:16:22 samsung930X3G avahi-daemon[3871]: Registering new address record for fe80::f4dd:30ff:fe16:9c5f on lxdbr0.*.
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8264] devices added (path: /sys/devices/virtual/net/lxdbr0, iface: lxdbr0)
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8264] device added (path: /sys/devices/virtual/net/lxdbr0, iface: lxdbr0): no ifupdown configuration found.
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8265] device (lxdbr0): state change: unmanaged -> unavailable (reason 'connection-assumed') [10 20 41]
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: started, version 2.75 cachesize 150
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: compile time options: IPv6 GNU-getopt DBus i18n IDN DHCP DHCPv6 no-Lua TFTP conntrack ipset auth DNSSEC loop-detect inotify
Aug 11 17:16:22 samsung930X3G dnsmasq-dhcp[8703]: DHCP, IP range 10.0.1.2 -- 10.0.1.254, lease time 1h
Aug 11 17:16:22 samsung930X3G dnsmasq-dhcp[8703]: DHCP, sockets bound exclusively to interface lxdbr0
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: using local addresses only for domain lxd
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: reading /etc/resolv.conf
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: using local addresses only for domain lxd
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: using nameserver 127.0.1.1#53
Aug 11 17:16:22 samsung930X3G dnsmasq[8703]: read /etc/hosts - 7 addresses
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8344] keyfile: add connection in-memory (3a22ac02-0cf4-464b-a779-26bbc556e0bb,"lxdbr0")
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8355] device (lxdbr0): state change: unavailable -> disconnected (reason 'connection-assumed') [20 30 41]
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [1470950182.8360] policy: Device 'lxdbr0' has no connection; scheduling activate_check in 0 seconds.
Aug 11 17:16:22 samsung930X3G systemd[1]: Started LXD - network bridge.
Aug 11 17:16:22 samsung930X3G NetworkManager[4003]: <info> [14...

[Stéphane Graber (stgraber)]

Sounds like something in your container was causing some kind of DNS query loop, completely overwhelming the DNS server, causing it to drop requests and log that message.

We've never had any such report by other LXD users so it seems very likely to be something to do with your setup/container rather than a general problem in LXD's dnsmasq configuration.

[Pat McGowan (pat-mcgowan)]

I thought I had seen it running just QtCreator (and no container started) but cannot reproduce that.