Public bug reported:
I'm running Ubuntu 18.04 (upgraded from 17.10) on a machine with both
ethernet and wifi interfaces. When I boot, my ethernet connection
enp0s31f6 is brought up by Network Manager and given three nameserver
addresses via DHCP, 10.1.13.10, 10.1.141.10, 10.1.13.36. Running nmcli
shows the three nameservers under "DNS configuration". Running "systemd-
resolve --status" shows them under a "Link 2 (enp0s31f6)" section. I can
do a "ip route get to X" and ping each one successfully. No other
connection is active.
testuser ☼ systemd-resolve --status
Global
DNS Domain: orgsdomain.net
DNSSEC NTA: 10.in-addr.arpa
16.172.in-addr.arpa
168.192.in-addr.arpa
17.172.in-addr.arpa
18.172.in-addr.arpa
19.172.in-addr.arpa
20.172.in-addr.arpa
21.172.in-addr.arpa
22.172.in-addr.arpa
23.172.in-addr.arpa
24.172.in-addr.arpa
25.172.in-addr.arpa
26.172.in-addr.arpa
27.172.in-addr.arpa
28.172.in-addr.arpa
29.172.in-addr.arpa
30.172.in-addr.arpa
31.172.in-addr.arpa
corp
d.f.ip6.arpa
home
internal
intranet
lan
local
private
test
Link 3 (wlp4s0)
Current Scopes: none
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
Link 2 (enp0s31f6)
Current Scopes: DNS
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 10.1.13.10
10.1.141.10
10.1.13.36
DNS Domain: orgsdomain.net
However, when I actually try to resolve a name, even the name of one of
the nameservers, dig claims that "connection timed out: no servers could
be reached".
testuser ☼ dig dcpdc001.orgsdomain.net +nocookie
; <<>> DiG 9.11.3-1ubuntu1.1-Ubuntu <<>> dcpdc001.orgsdomain.net +nocookie
;; global options: +cmd
;; connection timed out; no servers could be reached
Note that this name should resolve to 10.1.13.10, the first nameserver.
The "+nocookie" option is there to work around an issue with Windows DNS
servers. But other than that, the servers themselves work fine if I tell
dig where to look:
testuser ☼ dig dcpdc001.orgsdomain.net +nocookie @10.1.13.10
; <<>> DiG 9.11.3-1ubuntu1.1-Ubuntu <<>> dcpdc001.orgsdomain.net +nocookie
@10.1.13.10
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61294
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4000
;; QUESTION SECTION:
;dcpdc001.orgsdomain.net. IN A
;; ANSWER SECTION:
dcpdc001.orgsdomain.net. 3600 IN A 10.1.13.10
;; Query time: 2 msec
;; SERVER: 10.1.13.10#53(10.1.13.10)
;; WHEN: Fri Jul 20 10:56:27 AEST 2018
;; MSG SIZE rcvd: 65
I have configured resolvconf to use dynamic updates. /etc/resolv.conf
points to /run/resolvconf/resolv.conf. This file contains only (non-
comments):
nameserver 127.0.0.53
search orgsdomain
If I add "nameserver 10.1.13.10" to this file manually, suddenly dig can
resolve again (without the @...), and anything else that needs to
resolve names can do so. Removing the nameserver breaks that again.
I don't know much about the servers. They're part of a Windows-based
network, but since I can use them if I edit resolv.conf or give dig the
address, I don't think they're the issue (except in the sense that maybe
they require a feature that systemd-resolved doesn't support?).
I increased the logging level of systemd-resolved to "debug" and
"journalctl -f -u systemd-resolved" shows this during a failed query:
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Got DNS stub UDP query
packet for id 19836
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Looking up RR for
dcpdc001.orgsdomain.net IN A.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Switching to DNS server
10.1.13.10 for interface enp0s31f6.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Cache miss for
dcpdc001.orgsdomain.net IN A
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Transaction 12728 for
<dcpdc001.orgsdomain.net IN A> scope dns on enp0s31f6/*.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Using feature level
UDP+EDNS0+DO+LARGE for transaction 12728.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Using DNS server
10.1.13.10 for transaction 12728.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Sending query packet with
id 12728.
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Processing query...
Jul 20 10:33:23 heerij-ubuntu systemd-resolved[2352]: Timeout reached on
transaction 12728.
This repeats dozens of times, trying the other nameservers too. Note
that there is substantially less than a second between the "Processing
query..." message and the "Timeout reached..." message. (There are also
problems with the other servers not having port 53 open, so I also get
"Using degraded feature set..." messaged for them. But again, the first
server seems to work fine with everything except systemd-resolved.)
Things I have tried:
* Enabling DNSSEC. It's supported, but doesn't fix the issue.
* Explicitly setting nameservers in Netplan's config. Is accepted, but
doesn't change anything.
Sorry for the lack of the usual bug report attachments, but getting
anything out of this machine and on to the internet is now a massive
pain. Let me know what other debugging info might help and I'll try to
add it.
** Affects: systemd (Ubuntu)
Importance: Undecided
Status: New
** Bug watch added: github.com/systemd/systemd/issues #4621
https://github.com/systemd/systemd/issues/4621
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https://bugs.launchpad.net/bugs/1782679
Title:
systemd-resolved can't resolve at all, need to add nameservers to
resolve.conf
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