Controller shouldn't allocate IP addresses that are "reserved" for the subnet

[christianang]

Context

Broken out of the conversation started in #123 (comment).

There are ip addresses that shouldn't be given out that are reserved for special cases in the subnet. This is typically the network address, the broadcast address, and the gateway address.

Proposed Solution

If I defined the following pool:

Gateway: 192.168.0.1
Prefix: 16
Addresses:
- 192.168.0.0/16

The controller should not allocate: 192.168.0.0 (network address), 192.168.0.1 (gateway address), 192.168.255.255 (broadcast address). It would therefore give out 192.168.0.2-192.168.255.254.

If a user wants to allocate reserved addresses i.e ignore the above functionality except for gateway, a user can set a new flag called allocatedReservedAddresses, which would allocate 192.168.0.0-192.168.255.255 (except for 192.168.0.1). If the user doesn't want to reserve the gateway they should not set the gateway.

[schrej]

I think we should never allocate the gateway address when it's set. If you don't want it to be reserved, don't set it.

[christianang]

Yeah that makes sense. Updated the body of the issue.

[tylerschultz]

FYI - we're taking a hack at this issue

[schrej]

/assign @tylerschultz