Comment 5 for bug 1786799

Thanks Niels; I think we have all the information we need to further discuss this issue.

I'll copy and paste part of my comment on the merge proposal for bug #1776604; I think this is relevant:

"""
It's risky for us to change this code because effectively this function is a heuristic. It tries to guess the best interface to assign the node's primary hostname to. In cases where it guesses wrong, it's possible that customers have come to rely on the previous behavior. For example, it looks like we may be missing cases where there the PXE interface is configured with a triple-parent, such as:

physical (eth0) -> bond ({eth0, eth1} via bond0) -> vlan (bond0.11) -> bridge (br-vlan11)

In this case it's possible that a customer might be relying on MAAS to return an IP address assigned to bond0, when in fact we /could/ have a good argument that we should change the logic to return an IP address assigned to br-vlan11.
"""

Hence the dilemma: we would love to accept your patch into MAAS, but it's possible that someone else is already be relying on MAAS DNS to point to a management network with no gateway address.

I think the proper solution is what you imply: allow greater configuration of this algorithm, either implicitly (such as "prefer VLANs with a gateway over anything else") or explicitly ("I want this node to use interface X for its default DNS").