vlan: More consistent static IP consistency checks

[jbemmel]

---
defaults.device: frr
module: [vlan]

vlans:
 access:

nodes:
 n1:
  vlans:
   access:
    ipv4: 1
 n2:

links:
- n1:
    vlan.access: access
    ipv4: 2  # This is the one we end up with
  n2:
- n1:
    vlan.access: access
    ipv4: 3  # This gets ignored
  n2:

Arguably, the above topology should throw an error at ipv4: 2 because the user put ipv4: 1 at the node level.
We could allow ipv4: True (and keep .1)

If ipv4: 1 were removed, ipv4: 3 should throw an error (instead of getting ignored)

[ipspace]

See the warning in https://netlab.tools/module/vlan/#vlan-interface-parameters

What you're doing is not supported. If you feel like adding checks that will tell the user they should not set any parameters on the VLAN links I might look at the PR, but that's the maximum I'm willing to merge.

[jbemmel]

That’s my point: I’m not supposed to be able to set the IP to 2 like this, but it works

It’s not supported by design, but allowed in practice. That’s the inconsistency

[ipspace]

I think we fixed this (I should close discussions sooner ;)