No possibility to create an IPv6 only network

[narqo]

Hey, docker maintainers!

Currently NetworkController do subnet params normalisation, through the network.ipamAllocate() that always add predefined default IPv4 addresses with ipam.Allocator. This leads to inability to have an IPv6-only network even with drivers that (theoretically) might work without IPv4 address (e.g. macvlan from docker experimental).

Are there any reasons to do it in controller and not in the particular driver (taking into account that currently allocation is skipped for host and null drivers, using if n.Type() == "host" || n.Type() == "null").

[tgraf]

Related: #826

[GordonTheTurtle]

@narqo It has been detected that this issue has not received any activity in over 6 months. Can you please let us know if it is still relevant:

• For a bug: do you still experience the issue with the latest version?
• For a feature request: was your request appropriately answered in a later version?

Thank you!
This issue will be automatically closed in 1 week unless it is commented on.
For more information please refer to #1926