Dear Maintainer,

   * What led up to the situation?

     Installed `apt-cacher-ng` and `avahi-daemon` on Debian 13 which by default
     broadcasts an IPv4 and IPv6 address for an apt-proxy. *NB* IPv6
     routing is disabled in my network router.

     Installed `auto-apt-proxy` and `avahi-utils` on different Debian 13
     LXC. Running `auto-apt-proxy` returns the IPv6 proxy address, but
     `apt update` fails with

     `Cannot initiate the connection to fe80::be24:11ff:fe1f:d527:3142
     (fe80::be24:11ff:fe1f:d527). - connect (22: Invalid argument)`

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

     Turning off IPv6 in the avahi-daemon on the apt-cacher-ng machine
     results in the IPv4 proxy correctly being used -> proxy itself is
     functional.

     Opened `/usr/bin/auto-apt-proxy` to debug, the `hit` check also
     returns the same error, but this is not picked up in the grep
     statement -> auto-apt-proxy incorrectly thinks the IPv6 proxy is
     working

     Also tested on Debian sid, logic is the same -> still a problem in
     unstable

   * What was the outcome of this action?

     see above

   * What outcome did you expect instead?

     If the IPv6 does not connect, use the IPv4 address. This requires 2
     changes: 1) Fix the check to included additional connection errors, and 2) loop over
     the avahi-browse results, currently only the first result is
     checked (which in my case is the IPv6), and return the first one
     that works.

     Happy to help with further debugging/testing.

Hi,

Thanks for your bug report.

Would you be able to grab the binary package from
https://salsa.debian.org/debian/auto-apt-proxy/-/jobs/10124837/artifacts/file/debian/output/auto-apt-proxy_17.1+salsaci+20260812+59_all.deb
and test whether it fixes it for you? If you prefer to look at the
source, you can grab the auto-apt-proxy script from the
'avahi-check-all' branch at
https://salsa.debian.org/debian/auto-apt-proxy/-/tree/avahi-check-all

Sorry this build is actually broken. Try this one instead (or the source
from git branch avahi-check-all):

https://salsa.debian.org/debian/auto-apt-proxy/-/jobs/10125266/artifacts/file/debian/output/auto-apt-proxy_17.1+salsaci+20260812+61_all.deb

We believe that the bug you reported is fixed in the latest version of
auto-apt-proxy, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1124369@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Antonio Terceiro <terceiro@debian.org> (supplier of updated auto-apt-proxy package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Tue, 18 Aug 2026 11:05:20 -0300
Source: auto-apt-proxy
Architecture: source
Version: 18
Distribution: unstable
Urgency: medium
Maintainer: Antonio Terceiro <terceiro@debian.org>
Changed-By: Antonio Terceiro <terceiro@debian.org>
Closes: 1120071 1124369 1128058 1142542
Changes:
 auto-apt-proxy (18) unstable; urgency=medium
 .
   [ Paride Legovini ]
   * Revert "autopkgtest: drop test for squid-deb-proxy"
 .
   [ Antonio Terceiro ]
   * Log a message when default gateway can't be looked up
   * hit(): prevent apt-helper call from recursing into auto-apt-proxy
     (Closes: #1142542)
   * detect_squid_deb_proxy: fix log message
   * Give higher precedence to squid-deb-proxy
   * auto-apt-proxy.conf: drop unused auto-apt-proxy::Debug "setting"
   * wait for network to be online
   * Add ability to lookup default gateway with networkctl
   * Use a unique output directory per run
   * avahi: iterate over all address broadcast as potential proxies
   * avahi: handle unrouteable addresss (Closes: #1124369)
 .
   [ Tj ]
   * use legal SRV name (Closes: #1128058)
   * Rename AUTO_APT_PROXY_AVAHI_NAME to AUTO_APT_PROXY_MDNS_NAME
   * Add systemd-resolved mDNS support
 .
   [ Kirt Runolfson ]
   * Restore DNS hostname resolution for apt-proxy (Closes: #1120071)
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