Bug#1064133: systemd-resolved: Using systemd-resolved as drop-in replacements breaks in conjunction with ifupdown

[Michael Biebl]

On Sat, 17 Feb 2024 16:00:08 +0100 Felix Jacobi <felix at jacobi-bs.de> wrote:

> In background, this executes `resolvconf -a IFACE.PROTOCOL` and supplies
> the nameservers to resolvconf, e.g.
> 
> echo 'nameserver 192.0.0.1' | resolvconf -a ens3.inet
> 
> However, the systemd-resolved resolvconf implementation removes the
> protocol indentifier:
> 
> echo "nameserver 192.0.0.1" | resolvconf -a ens3.inet
> Dropped protocol specifier '.inet' from 'ens3.inet'. Using 'ens3' (ifindex=2).
> 
> This leads to the fact, that only ens3 is used internally. For the
> configuration above, this means the previous configured IPv4 nameserver
> is completely overriddden with the latter one in the IPv6 stanza.
> 
> This also causes several other problems for tools relying on resolvconf
> not dropping the protocol identifier and I would consider this a
> breaking change compared to the original resolvconf implementation.

The Debian package does not ship any patches in that regard.
It would thus be best if you raise this upstream at
https://github.com/systemd/systemd/issues

I did not immediately find, why resolvectl/resolved does strip away the 
protocol identifier.
At the very least, this incompatibility could be documented in the 
resolvctl man page.

Regards,
Michael
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