Comment 4 for bug 2055148

So, I believe the best solution here would be to add options to DNS addresses, similar to what we do with IP addresses. Something like this

nameservers:
  addresses:
    - 1.2.3.4:
        sni: domain
        port: 1234
        interface: eth123
    - 1.1.1.1

with this we'd fully support both Network Manager and networkd backends.

Right now NM seems to support only the SNI parameter (1.2.3.4#domain) but networkd supports more:

"111.222.333.444:9953%ifname#example.com" for IPv4 and "[1111:2222::3333]:9953%ifname#example.com" for IPv6.

Alternatively, to keep things simpler, we could just accept the string 1.2.3.4#domain (and possibly the full notation used by networkd too).

What do you think, Lukas?