[Bug 1727237] Re: systemd-resolved is not finding a domain

[Steve Langasek]

My understanding is that systemd-resolved as shipped in Ubuntu is meant
to not have DNS caching enabled at all.

  https://lists.ubuntu.com/archives/ubuntu-devel/2016-June/039375.html

Looking at the default resolved.conf and the resolved.conf(5) manpage,
it appears we do have DNS caching enabled.

Dimitri, is this an oversight, or was there some further discussion with
the Security Team that resulted in caching being enabled?

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Title:
  systemd-resolved is not finding a domain

Status in systemd package in Ubuntu:
  Triaged

Bug description:
  I have an odd network situation that I have so far managed to narrow
  down to the inability to resolve a domain via systemd-resolved which
  is resolvable with nslookup. If I use nslookup against the two
  nameservers on this network I get answers for the domain, but ping
  says it is unable to resolve the same domain (as do browsers and
  crucially the captive portal mechanism).

  Here are details:

  NSLOOKUP:

  ~$ nslookup securelogin.arubanetworks.com 208.67.220.220
  Server:		208.67.220.220
  Address:	208.67.220.220#53

  Non-authoritative answer:
  Name:	securelogin.arubanetworks.com
  Address: 172.22.240.242

  ~$ nslookup securelogin.arubanetworks.com 208.67.222.222
  Server:		208.67.222.222
  Address:	208.67.222.222#53

  Non-authoritative answer:
  Name:	securelogin.arubanetworks.com
  Address: 172.22.240.242

  
  PING:

  ~$ ping securelogin.arubanetworks.com
  ping: securelogin.arubanetworks.com: Name or service not known
  mark at mark-X1Y2:~$ 

  
  DIG:

  ~$ dig @208.67.222.222 securelogin.arubanetworks.com

  ; <<>> DiG 9.10.3-P4-Ubuntu <<>> @208.67.222.222 securelogin.arubanetworks.com
  ; (1 server found)
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 9416
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 4096
  ;; QUESTION SECTION:
  ;securelogin.arubanetworks.com.	IN	A

  ;; AUTHORITY SECTION:
  arubanetworks.com.	1991	IN	SOA	dns5.arubanetworks.com. hostmaster.arubanetworks.com. 1323935888 3600 200 1209600 86400

  ;; Query time: 34 msec
  ;; SERVER: 208.67.222.222#53(208.67.222.222)
  ;; WHEN: Wed Oct 25 10:31:10 CEST 2017
  ;; MSG SIZE  rcvd: 144

  
  MORE DIG:

  ~$ dig securelogin.arubanetworks.com

  ; <<>> DiG 9.10.3-P4-Ubuntu <<>> securelogin.arubanetworks.com
  ;; global options: +cmd
  ;; Got answer:
  ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 3924
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

  ;; OPT PSEUDOSECTION:
  ; EDNS: version: 0, flags:; udp: 65494
  ;; QUESTION SECTION:
  ;securelogin.arubanetworks.com.	IN	A

  ;; Query time: 0 msec
  ;; SERVER: 127.0.0.53#53(127.0.0.53)
  ;; WHEN: Wed Oct 25 10:34:01 CEST 2017
  ;; MSG SIZE  rcvd: 58

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