Hello, I tried to get DNS packets using :
$ sudo tcpdump -i lxcbr0 -l -vvv dst host 10.0.3.1 and dst port 53 |tee /tmp/tcpdump-dns I then wait until systemd-resolved ate 100% of CPU. But at this time (unfortunately when I noticed it, it may have been eaten CPU for quite a while). However I can't see any strange exchange between systemd- resolved and dnsmasq. I attach all the packets captured by tcpdump. I'm not an expert in networks topics but I'm at ease with linux and cli commands, so feel free to tell me which experiment you would like me to run. ** Attachment added: "tcpdump session between dnsmasq and systemd-resolved" https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1721092/+attachment/5044944/+files/tcpdump-dns -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to systemd in Ubuntu. https://bugs.launchpad.net/bugs/1721092 Title: systemd-resolved and dns-masq make CPU 100% when using lxc name resolution Status in systemd package in Ubuntu: Triaged Bug description: This bug may be a duplicate of https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/1688364 but I'm not sure, hence this new entry. It hits while I wanted systemd to resolve the lxc domain to my internal lxc hosts. Step to (maybe) reproduce: - having lxc installed - make some user space lxc container - uncomment the line LXC_DOMAIN="lxc" in /etc/default/lxc-net - restart lxc-net service Now the dnsmasq on 10.0.3.1 should be a dns resolving lxc names. - add a file /etc/systemd/resolved.conf.d/lxc.conf [Resolve] DNS=10.0.3.1 Domains=~.lxc DNSSEC=false - restart systemd-resolved service Now systemd knows it should ask .lxc names to dnsmasq - start an lxc container, let assume it's called my-container - ping it using my-container.lxc it should work After some times, systemd-resolved should use 100% CPU. Commenting the /etc/systemd/resolved.conf.d/lxc.conf file and restarting it makes systemd-resolved never eating resources again. ProblemType: Bug DistroRelease: Ubuntu 17.04 Package: systemd 232-21ubuntu5 Uname: Linux 4.10.16-041016-generic x86_64 ApportVersion: 2.20.4-0ubuntu4.5 Architecture: amd64 CurrentDesktop: GNOME Date: Tue Oct 3 18:18:56 2017 InstallationDate: Installed on 2015-11-10 (692 days ago) InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021) MachineType: Intel Corporation Skylake Platform ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.10.16-041016-generic root=UUID=6814e3c1-8cea-4ecc-964d-535fd18782e9 ro quiet splash crashkernel=384M-:128M vt.handoff=7 SourcePackage: systemd UpgradeStatus: Upgraded to zesty on 2017-02-25 (219 days ago) dmi.bios.date: 11/06/2015 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 5.11 dmi.board.asset.tag: Base Board Asset Tag dmi.board.name: WhiteTip Mountain1 Fab2 dmi.board.vendor: Topstar dmi.board.version: RVP7 dmi.chassis.asset.tag: Default string dmi.chassis.type: 9 dmi.chassis.vendor: Default string dmi.chassis.version: Default string dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr5.11:bd11/06/2015:svnIntelCorporation:pnSkylakePlatform:pvr0.1:rvnTopstar:rnWhiteTipMountain1Fab2:rvrRVP7:cvnDefaultstring:ct9:cvrDefaultstring: dmi.product.name: Skylake Platform dmi.product.version: 0.1 dmi.sys.vendor: Intel Corporation To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1721092/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
