ddclient: unable to determine IPv6 address with strategy usev6=ifv6

[flipside2]

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Describe the bug

I'm trying to update my existing DDNS configuration to also update my IPv6 address. The configuration in the GUI is as follows:

and the file /usr/local/etc/ddclient.conf contains the following:

syslog=yes                  # log update msgs to syslog
pid=/var/run/ddclient.pid   # record PID in file.
verbose=yes
ssl=yes

usev6=ifv6, ifv6=pppoe0, \
usev4=ifv4, ifv4=pppoe0, \
protocol=dyndns2, \
server=dyndns.inwx.com, \
login=<hidden>, \
password=<hidden> \
<hidden>

Now the issue I am facing is that my ddclient log file contains the following entry:

hg.lan: unable to determine IPv6 address with strategy usev6=ifv6

and the IPv6 address is not updated. IPv4 works fine.

A clear and concise description of what the bug is, including last known working version (if any).

To Reproduce
Steps to reproduce the behavior:

1. Configure DDNS as shown above
2. Restart ddclient service
3. See error, IPv6 address not updated

Expected behavior

The IPv6 address should be detected and the update should be processed

Screenshots

See above

Relevant log files

See above

Additional context

PPPoE via

WAN interface:

PPPoE device:

Network topology:

Environment

OPNsense 25.7.8-amd64
FreeBSD 14.3-RELEASE-p5
OpenSSL 3.0.18