[Bug 1875044] [NEW] Host name not resolved

[Rimas Kudelis]

Public bug reported:

Systemd-resolved fails to resolve a host which has a private IP address, even though its DNS entry is public. This happens even when I am connected to a VPN where the host resides.
Interestingly, if I manually issue a `host -a` request, the host gets resolved, and further resolution works until its cached entry times out.

Here's some hopefully helpful output of me running `nslookup` and
`host`:

# nslookup
> presto.lmta.lt
Server:		127.0.0.53
Address:	127.0.0.53#53

Non-authoritative answer:
*** Can't find presto.lmta.lt: No answer
> server 8.8.8.8
Default server: 8.8.8.8
Address: 8.8.8.8#53
> presto.lmta.lt
Server:		8.8.8.8
Address:	8.8.8.8#53

Non-authoritative answer:
Name:	presto.lmta.lt
Address: 10.41.0.118
> server 127.0.0.53
Default server: 127.0.0.53
Address: 127.0.0.53#53
> presto.lmta.lt
Server:		127.0.0.53
Address:	127.0.0.53#53

Non-authoritative answer:
*** Can't find presto.lmta.lt: No answer
[^D pressed]

# host presto.lmta.lt
[no output at all. I immediately run the next command]

# host -a presto.lmta.lt
Trying "presto.lmta.lt"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20532
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;presto.lmta.lt.			IN	ANY

;; ANSWER SECTION:
presto.lmta.lt.		3599	IN	A	10.41.0.118

Received 48 bytes from 127.0.0.53#53 in 57 ms

[then immediately afterwards:]
# host presto.lmta.lt
presto.lmta.lt has address 10.41.0.118

# nslookup
> presto.lmta.lt
Server:		127.0.0.53
Address:	127.0.0.53#53

Non-authoritative answer:
Name:	presto.lmta.lt
Address: 10.41.0.118

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1875044

Title:
  Host name not resolved

Status in systemd package in Ubuntu:
  New

Bug description:
  Systemd-resolved fails to resolve a host which has a private IP address, even though its DNS entry is public. This happens even when I am connected to a VPN where the host resides.
  Interestingly, if I manually issue a `host -a` request, the host gets resolved, and further resolution works until its cached entry times out.

  Here's some hopefully helpful output of me running `nslookup` and
  `host`:

  # nslookup
  > presto.lmta.lt
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  Non-authoritative answer:
  *** Can't find presto.lmta.lt: No answer
  > server 8.8.8.8
  Default server: 8.8.8.8
  Address: 8.8.8.8#53
  > presto.lmta.lt
  Server:		8.8.8.8
  Address:	8.8.8.8#53

  Non-authoritative answer:
  Name:	presto.lmta.lt
  Address: 10.41.0.118
  > server 127.0.0.53
  Default server: 127.0.0.53
  Address: 127.0.0.53#53
  > presto.lmta.lt
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  Non-authoritative answer:
  *** Can't find presto.lmta.lt: No answer
  [^D pressed]

  # host presto.lmta.lt
  [no output at all. I immediately run the next command]

  # host -a presto.lmta.lt
  Trying "presto.lmta.lt"
  ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20532
  ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

  ;; QUESTION SECTION:
  ;presto.lmta.lt.			IN	ANY

  ;; ANSWER SECTION:
  presto.lmta.lt.		3599	IN	A	10.41.0.118

  Received 48 bytes from 127.0.0.53#53 in 57 ms

  [then immediately afterwards:]
  # host presto.lmta.lt
  presto.lmta.lt has address 10.41.0.118

  # nslookup
  > presto.lmta.lt
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  Non-authoritative answer:
  Name:	presto.lmta.lt
  Address: 10.41.0.118

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