URI defined for connectivity check is relative to search domain

[Kenny]

The connectivity check URI as defined in /usr/lib/NetworkManager/conf.d/20-connectivity-ubuntu.conf is not an absolute FQDN (doesn't end in a dot). As such, resolving connectivity-check.ubuntu.com generates queries for connectivity-check.ubuntu.com.localdomain (assuming a common default search domain of "localdomain") in addition to the expected connectivity-check.ubuntu.com . Or, if your ISP provided search domain is myisp.net, then connectivity-check.ubuntu.com.myisp.net is also queried.

To reduce unintended traffic, may I suggest a trailing dot to ensure the host portion of the URI is a FQDN? Ex:

uri=http://connectivity-check.ubuntu.com./

# lsb_release -rd
Description: Ubuntu 20.04.3 LTS
Release: 20.04

# apt-cache policy network-manager-config-connectivity-ubuntu
network-manager-config-connectivity-ubuntu:
  Installed: 1.22.10-1ubuntu2.2
  Candidate: 1.22.10-1ubuntu2.2
  Version table:
 *** 1.22.10-1ubuntu2.2 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main i386 Packages
        100 /var/lib/dpkg/status
     1.22.10-1ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu focal/main i386 Packages

# What I expected to happen:
Sep 23 18:48:45 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com from 192.168.0.111
Sep 23 18:48:45 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com from 192.168.0.111
Sep 23 18:50:55 dnsmasq[415]: query[A] connectivity-check.ubuntu.com from 192.168.0.111
(requests resulting in NXDOMAIN or NODATA-IPv6 are made twice)

# What happened instead:
Sep 23 17:02:49 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com from 192.168.0.111
Sep 23 17:02:49 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com from 192.168.0.111
Sep 23 17:02:49 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com.localdomain from 192.168.0.111
Sep 23 17:02:49 dnsmasq[415]: query[AAAA] connectivity-check.ubuntu.com.localdomain from 192.168.0.111
Sep 23 17:04:42 dnsmasq[415]: query[A] connectivity-check.ubuntu.com from 192.168.0.111

[Sebastien Bacher (seb128)]

Thank you for your bug report, that was discussed in bug #1880258 and is fixed in the current Ubuntu serie