I'm not sure I understand what you mean. In a typical configuration you never send "foo" to the nameservice, there's always a search domain and those lookups are always tried first (because the default value for the ndots is 1). This is handled by the libc resolver linked into every program, it's not handled by a central service.
I don't have any idea how systemd-resolve works. But, my understanding of how it used to work with dnsmasq using split tunneling was that the nameservice mapped domains to DNS servers, and the resolver would only forward requests to the DNS server that matched the domain for the host being requested. If you have a VPN interface that adds "mycorp.com" to the search domain that appears in /etc/resolv.conf search, so it contains "mycorp.com localdomain" for example. Then when someone tries to resolve "myhost", the libc resolver sees that there are no dots here and so it starts appending search paths to the hostname, in order, and sending them to the DNS service to look up. So first it will send "myhost.mycorp.com" to the resolver. The resolver sees that the hostname ends in "mycorp.com" and it knows that the VPN DNS servers "own" that domain, so it forwards that request to those servers for lookup. If that doesn't match, then the libc resolver will try to look up "myhost.localdomain". That does NOT match the VPN domain, so it will not try to forward that to the DNS servers for the VPN connection and instead use a different resolver. I don't think there's any information leakage here. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1726124 Title: DNS domain search paths not updated when VPN started Status in network-manager package in Ubuntu: New Status in network-manager-openvpn package in Ubuntu: New Status in systemd package in Ubuntu: New Bug description: I connect to work with openvpn through network-manager-openvpn. I'm selecting automatic (DHCP) to get an IP address, and "Use this connection only for resources on its network" to support split tunneling. In the last few versions of Ubuntu I used, this all worked fine. In Ubuntu 17.10 (fresh install, not upgrade) I can access hosts on both my VPN network and the internet, BUT I have to use FQDN for my VPN network hosts: the updates to the DNS search path provided by my VPN DHCP server are never being applied. Investigating the system I see that /etc/resolv.conf is pointing to /run/systemd/resolve/stub-resolv.conf and that resolv.conf does not have any of the VPN's search path settings in it: # This file is managed by man:systemd-resolved(8). Do not edit. # # 127.0.0.53 is the systemd-resolved stub resolver. # run "systemd-resolve --status" to see details about the actual nameservers. nameserver 127.0.0.53 search home In previous versions of Ubuntu, where NetworkManager controlled the resolver not systemd, /etc/resolv.conf pointed to /run/NetworkManager/resolv.conf and there was a local dnsmasq instance that managed all the complexity. In Ubuntu 17.10 when I look in /run/NetworkManager/resolv.conf file, I see that the search paths ARE properly updated there: $ cat /run/NetworkManager/resolv.conf # Generated by NetworkManager search internal.mycorp.com other.mycorp.com home nameserver 127.0.1.1 However this file isn't being used, and also there's no dnsmasq running on the system so if I switch my /etc/resolv.conf to point to this file instead, then all lookups fail. Strangely, if I look at the systemd-resolv status I see that in theory systemd-resolve does seem to know about the proper search paths: $ systemd-resolve --status ... Link 3 (tun0) Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6 LLMNR setting: yes MulticastDNS setting: no DNSSEC setting: no DNSSEC supported: no DNS Servers: 10.3.0.10 10.8.42.2 DNS Domain: ~internal.mycorp.com ~other.mycorp.com but for whatever reason the search domains are not getting put into the resolv.conf file: $ host mydesk ;; connection timed out; no servers could be reached $ host mydesk.internal.mycorp.com mydesk.internal.mycorp.com has address 10.8.37.74 (BTW, the timeout in the failed attempt above takes 10s: it is SUPER frustrating when all your host lookups are taking that long just to fail). ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: systemd 234-2ubuntu12 ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4 Uname: Linux 4.13.0-16-generic x86_64 ApportVersion: 2.20.7-0ubuntu3 Architecture: amd64 CurrentDesktop: GNOME Date: Sun Oct 22 15:08:57 2017 InstallationDate: Installed on 2017-10-21 (1 days ago) InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20171018) MachineType: System manufacturer System Product Name ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-16-generic root=UUID=4384306c-5fed-4b48-97a6-a6d594c4f72b ro quiet splash vt.handoff=7 SourcePackage: systemd SystemdDelta: [EXTENDED] /lib/systemd/system/rc-local.service → /lib/systemd/system/rc-local.service.d/debian.conf [EXTENDED] /lib/systemd/system/user@.service → /lib/systemd/system/user@.service.d/timeout.conf 2 overridden configuration files found. UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 12/02/2014 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: 2101 dmi.board.asset.tag: To Be Filled By O.E.M. dmi.board.name: M5A78L-M/USB3 dmi.board.vendor: ASUSTeK Computer INC. dmi.board.version: Rev X.0x dmi.chassis.asset.tag: Asset-1234567890 dmi.chassis.type: 3 dmi.chassis.vendor: Chassis Manufacture dmi.chassis.version: Chassis Version dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr2101:bd12/02/2014:svnSystemmanufacturer:pnSystemProductName:pvrSystemVersion:rvnASUSTeKComputerINC.:rnM5A78L-M/USB3:rvrRevX.0x:cvnChassisManufacture:ct3:cvrChassisVersion: dmi.product.family: To Be Filled By O.E.M. dmi.product.name: System Product Name dmi.product.version: System Version dmi.sys.vendor: System manufacturer To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1726124/+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