Dear Maintainer,

When creating an IPv6 network with Docker 26.1.5+dfsg1-9+b13, the gateway's
address reported by Docker includes the prefix, for example,
fd05:d0ca:2::1/112. The prefix is retained until Docker is restarted. That
breaks various tools, including Docker's newest Go client libraries
(github.com/moby/moby/client v0.4), which makes upgrading them impossible if
compatibility with the Docker version included in Debian 13 should be retained.

Please see the following upstream reports for details:

https://github.com/moby/moby/issues/52991
https://github.com/moby/moby/pull/49520

Thanks!

Hi Andreas,

Thank you for reporting this issue and for providing the upstream references.

As you noted, this was fixed upstream in moby/moby PR #49520 ("Fix network
inspect IPv6 gateway address format"), which was included starting in
Docker Engine v28.0.1.

In Debian unstable (sid), docker.io was upgraded to the 28.x series in
version 28.5.2+dfsg1-1, where the fix is present (engine/daemon/network.go
now reports the IP address without the CIDR prefix).

I am therefore closing this bug with version 28.5.2+dfsg1-1.

(Regarding Debian 13 / Trixie where docker.io 26.1.5 is packaged, we are
evaluating the backport of PR #49520 for a future point release update.)

Thanks,
Reinhard