Default .weave.local domain is reserved for Multicast DNS

[bboreham]

Weave Net by default registers hosts in .weave.local domain. Unfortunately that name is reserved by RFC6762:

This document specifies that the DNS top-level domain ".local." is a
special domain with special semantics, namely that any fully
qualified name ending in ".local." is link-local, and names within
this domain are meaningful only on the link where they originate.

We became aware of this via golang/go#16739, because Go 1.7 changed to not send DNS queries for .local domains.

Users may work round this by specifying a different domain to Weave, e.g.:

weave launch --dns-domain=mydomain.net

and using the same domain in any related places, e.g. if you specify --hostname on a container.

[rade]

The bit of the spec that hurts us is

Any DNS query for a name ending with ".local." MUST be sent to the mDNS IPv4 link-local multicast address 224.0.0.251

[bboreham]

The Go change was unwound; Kubernetes is still using .local; I am downgrading from a bug to a chore.