Make veth settings closer to those produced by the weave script

[awh]

The weave script does a few things like ethtool tx off that the plugin doesn't currently do.

Most of these are not relevant to FDP, only the "slow" path.

Replaces weaveworks-experiments/docker-plugin#53; see there for additional commentary.

[bboreham]

Also the weave script adds a multicast route for each container

[bboreham]

Multicast route covered by #1776; ethtool tx off less important now we're mostly not using pcap.

[rade]

ethtool tx off less important now we're mostly not using pcap.

See #1788 for why that is the case.

[rade]

So what is left to do here?

[bboreham]

The predecessor issue noted "The arp stuff is relevant".

The ethtool point also relates to #1255

[bboreham]

The Docker plugin is not given direct access to the container's namespace (indeed, it is called before the container has started), so adjusting its arp settings requires an indirect approach. We could do it in the same place we add DNS names, i.e. after the container has started.

Note #2030 adds a utility function to do the arp settings.

[bboreham]

tx off now implemented by #2307; only arp settings and gratuitous arp remain.

These would have to be done asynchronously by the plugin, after the container starts, because they need to be done in the container's namespace. Docker does not provide a hook to do this.

Also Docker doesn't tell the network driver the IP address in JoinEndpoint.

Probably we can do it at the same time as we do the DNS update; we need to find the container's namespace, enter it, do the arp stuff.