[Bug 1957086] Re: Autopkgtest systemd fail against dnsmasq 2.86 (22.04)

[Christian Ehrhardt ]

Result of the repro:


#2 ipv6 fails and gets into a loop
dig @10.241.3.1 -t AAAA math.lab

#2a - Good case (dnsmasq 2.85)
root at j-dnsmasq-release:~# dig @10.241.3.1 -t AAAA math.lab
dnsmasq: query[AAAA] math.lab from 10.241.3.1
dnsmasq: config math.lab is NODATA-IPv6

; <<>> DiG 9.16.15-Ubuntu <<>> @10.241.3.1 -t AAAA math.lab
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48650
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;math.lab.			IN	AAAA

;; Query time: 0 msec
;; SERVER: 10.241.3.1#53(10.241.3.1)
;; WHEN: Tue Jan 11 13:09:21 UTC 2022
;; MSG SIZE  rcvd: 37


#2b - Bad case (dnsmasq 2.86)

root at j-dnsmasq-proposed:~# dig @10.241.3.1 -t AAAA math.lab
dnsmasq: query[AAAA] math.lab from 10.241.3.1
dnsmasq: forwarded math.lab to 127.0.0.53
dnsmasq: query[AAAA] math.lab from 10.241.3.1
dnsmasq: forwarded math.lab to 127.0.0.53
dnsmasq: query[AAAA] math.lab from 10.241.3.1
...
dnsmasq: Maximum number of concurrent DNS queries reached (max: 150)
dnsmasq: config error is REFUSED
... repeats infinitely


There is no ipv6 answer configured, so it is ok to return an empty/bad answer.

But dnsmasq should not fall into a forwarding loop right?
Or does this test make a hard configuration mistake (always did) that now
in 2.86 exposes an issue, but was always wrong?


The original test command of `resolvectl query math.lab` gets into a "wait
until timeout" with the new behavior.

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https://bugs.launchpad.net/bugs/1957086

Title:
  Autopkgtest systemd fail against dnsmasq 2.86 (22.04)

Status in dnsmasq package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  New

Bug description:
  Full log (same on all architectures):
  https://autopkgtest.ubuntu.com/results/autopkgtest-jammy/jammy/arm64/s/systemd/20220106_214401_24d29@/log.gz

  The test is from systemd:
  https://github.com/systemd/systemd/blob/main/test/networkd-test.py#L619

  Tail of the log:
  ```
  ERROR: test_resolved_domain_restricted_dns (__main__.DnsmasqClientTest)
  resolved: domain-restricted DNS servers
  ----------------------------------------------------------------------
  Traceback (most recent call last):
    File "/tmp/autopkgtest.NdIvJq/build.fBQ/src/test/networkd-test.py", line 678, in test_resolved_domain_restricted_dns
      out = subprocess.check_output(['resolvectl', 'query', 'math.lab'])
    File "/usr/lib/python3.9/subprocess.py", line 424, in check_output
      return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
    File "/usr/lib/python3.9/subprocess.py", line 528, in run
      raise CalledProcessError(retcode, process.args,
  subprocess.CalledProcessError: Command '['resolvectl', 'query', 'math.lab']' returned non-zero exit status 1.
  ```

  
  Tagging update-excuse to be shown in excuses

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