I have two VPNs – one via wireguard for my general internet traffic, one via openvpn (for work). DNS resolution over openvpn is only partly working.
With both tunnels up:
A) systemd-resolve needs to be "taught" to use tun0. (This was working previously when both VPNs were using openvpn.)
> systemd-resolve jenkins.staging.mycompany.com
jenkins.staging.mycompany.com: resolve call failed: All attempts to contact name servers or networks failed
> systemd-resolve -i tun0 jenkins.staging.mycompany.com
jenkins.staging.mycompany.com: 10.1.2.36 -- link: tun0
-- Information acquired via protocol DNS in 48.5ms.
-- Data is authenticated: no
> systemd-resolve jenkins.staging.mycompany.com
jenkins.staging.mycompany.com: 10.1.2.36 -- link: tun0
-- Information acquired via protocol DNS in 852us.
-- Data is authenticated: no
B) dig works out of the box. nslookup only works if I tell it which DNS server to use. curl doesn't work.
> curl jenkins.staging.mycompany.com:8080
curl: (6) Could not resolve host: jenkins.staging.mycompany.com
> dig jenkins.staging.mycompany.com
; <<>> DiG 9.11.5-P4-5.1ubuntu2.1-Ubuntu <<>> jenkins.staging.mycompany.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 2834
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1280
;; QUESTION SECTION:
;jenkins.staging.mycompany.com. IN A
;; AUTHORITY SECTION:
mycompany.com. 56 IN SOA [aws dns info]
;; Query time: 47 msec
;; SERVER: 172.16.0.1#53(172.16.0.1)
;; WHEN: Sat Apr 18 09:08:44 EDT 2020
;; MSG SIZE rcvd: 143
> nslookup jenkins.staging.mycompany.com
Server: 172.16.0.1 <- uses wrong dns server by default
Address: 172.16.0.1#53
** server can't find jenkins.staging.mycompany.com: NXDOMAIN
> nslookup jenkins.staging.mycompany.com 10.0.0.2
Server: 10.0.0.2
Address: 10.0.0.2#53
Non-authoritative answer:
Name: jenkins.staging.mycompany.com
Address: 10.1.2.36
My theory was that wireguard was somehow stealing DNS responsibilities from systemd, so I attempted to add the openvpn provided DNS to the client conf file:
[Interface]
PrivateKey = xxx
Address = 172.aa.bb.cc/32
DNS = 172.16.0.1 10.0.0.2
But this doesn't help.
systemd-resolve's config looks fine, I think(?):
> resolveconf status
Global
LLMNR setting: no
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
Current DNS Server: 172.16.0.1
DNS Servers: 172.16.0.1
10.0.0.2
DNS Domain: staging.mycompany.com
production.mycompany.com
infrastructure.mycompany.com
DNSSEC NTA: 10.in-addr.arpa
...
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 5 (tun0)
Current Scopes: DNS
DefaultRoute setting: yes
LLMNR setting: yes
MulticastDNS setting: no
DNSOverTLS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 10.0.0.2
DNS Domain: staging.mycompany.com
production.mycompany.com
infrastructure.mycompany.com
Best Answer
I have a suggestion but I don't have enough reputation to comment so I'm putting my comment in an answer. Have you looked at the interface metric for your Wireguard virtual adapter and your OpenVPN virtual adapter? I know in Windows, when I run into the problem you are describing, I have to manually set the interface metric on both, for the OpenVPN virtual adapter it just has to be lower than the metric for the other adapter.