This is still happening with 17.10 final. I have been digging a bit and found something that makes me think that this is a caching / IPv6 issue. Attached is the screenshot of a Wireshark capture of the DNS packets on all interfaces on the affected machine (the IP address of the machine is 192.168.0.154).
When querying a hostname that should be resolved to a local network address (in this case odoo.caligrafix.cl), the resolver makes two requests to our local DNS server 192.168.0.2 (and not to any external DNS server, as I first thought): 1. The request for odoo.caligrafix.cl 2. A request for o3.caligrafix.cl. The second request is made before receiving the response to the first request. This second request can be explained by the fact that outside of our network, the name odoo.caligrafix.cl resolves to a CNAME o3.caligrafix.cl, and for some reason the resolver uses this cached information instead of waiting for the result of the first request. The response to the first request, which correctly indicates the expected local network address, seems to be discarded, and the result of subsequent requests that resolves to our public address trough a chain of CNAMES, is used instead. The funny thing is that after flushing the resolver's cache, the resolver also makes two requests to our local DNS server, but both with the name odoo.caligrafix.cl, and gets the correct answer. But then it makes a request for the AAAA (IPv6) record, and gets the chain the CNAME records that lead to our public IP. So it seems that somehow the IPv6 and IPv4 caches get mixed up afterwards. Although I guess I could (and will attempt to) mitigate the issue by configuring the AAAA record differently on our DNS server, I think the current behavior of the resolver is incorrect, as it uses cached info for an IPv6 record when querying an IPv4 record. ** Attachment added: "Wireshark capture of failed resolution" https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1716976/+attachment/4997137/+files/Screenshot%20from%202017-10-26%2018-22-20.png -- 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/1716976 Title: DNS resolver mixes IPv6 and IPv4 caches Status in systemd package in Ubuntu: New Bug description: In our network we have a DNS server that resolves some names to local addresses, while the same names are resolved to our public IP when public DNSs are used. For instance (using fictitious names and IPs), xyz.mydomain.com resolves to the public IP 65.254.242.180 when using an external DNS server, but resolves to 192.168.0.14 when using our internal DNS server (which all our computers are told to use via DHCP). This used to work fine until a somewhat recent update in Ubuntu 17.10. Now, xyz.domain.com almost always resolves to the public IP instead of the internal IP. Interestingly, restarting the systemd-resolved service fixes the problem for a while (from a few seconds to a few minutes). Right after restarting the service, the dig command reports the expected internal IP, but after a while it gets back to reporting the public IP. Forcing the dig command to query our DNS server instead of the local resolver returns the correct IP. ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: systemd 234-2ubuntu9 ProcVersionSignature: Ubuntu 4.12.0-13.14-generic 4.12.10 Uname: Linux 4.12.0-13-generic x86_64 ApportVersion: 2.20.7-0ubuntu1 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Wed Sep 13 13:34:50 2017 InstallationDate: Installed on 2015-01-23 (963 days ago) InstallationMedia: Ubuntu-GNOME 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2) MachineType: LENOVO 20266 ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.12.0-13-generic.efi.signed root=UUID=eecad38d-4fff-462c-92bc-357fa12e5515 ro quiet splash vt.handoff=7 SourcePackage: systemd UpgradeStatus: Upgraded to artful on 2017-06-15 (90 days ago) dmi.bios.date: 03/30/2015 dmi.bios.vendor: LENOVO dmi.bios.version: 76CN43WW dmi.board.asset.tag: No Asset Tag dmi.board.name: Yoga2 dmi.board.vendor: LENOVO dmi.board.version: 31900058STD dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: LENOVO dmi.chassis.version: Lenovo Yoga 2 Pro dmi.modalias: dmi:bvnLENOVO:bvr76CN43WW:bd03/30/2015:svnLENOVO:pn20266:pvrLenovoYoga2Pro:rvnLENOVO:rnYoga2:rvr31900058STD:cvnLENOVO:ct10:cvrLenovoYoga2Pro: dmi.product.family: IDEAPAD dmi.product.name: 20266 dmi.product.version: Lenovo Yoga 2 Pro dmi.sys.vendor: LENOVO To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1716976/+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
