The switch to using subnetpools caused quite a bit of confusion
because it didn't respect the value of FIXED_RANGE. This caused
conflicts in the gate with it's default IPv4 value of 10.0.0.0/8.
This patch does a few things to address the issue:
* It introduces the IPV4_ADDRS_SAFE_TO_USE and IPV6_ADDRS_SAFE_TO_USE
values and adjusts all of the FIXED_RANGE and SUBNETPOOL_PREFIX values
to dervive from them by default.
* This addresses the concern that was raised about implying that
SUBNETPOOL_PREFIX and FIXED_RANGE are equivalent when setting
SUBNETPOOL_PREFIX=FIXED_RANGE by default. Now we have a new value
for the operator specify a chunk of addresses that are safe to
use for private networks without implementation implications.
* Backwards compatibility is maintained by alloing users to override
override all of these values.
* The default for IPV4_ADDRS_SAFE_TO_USE uses /22 instead of /24
* Because we want to be able to use subnetpools for auto allocated
topologies and we want to be able to have a large chunk of
instances on each network, we needed a little more breathing room
in the default v4 network size.
* SUBNET_POOL_SIZE_V4 default is changed from 24 to 26
* In conjuction with this change and the one above, the default
subnetpool will support up to 16 64-address allocations.
* This should be enough to cover any regular gate scenarios.
* If someone wants a bigger/smaller subnet, they can ask for that
in the API request, change this value themselves, or use a different
network entirely.
* FIXED_RANGE_V6 defaults to a max prefix of /64 from IPV6_ADDRS_SAFE_TO_USE
* This avoids the private subnet in the non-subnetpool case from being
larger than /64 to avoid issues identified in rfc 7421.
* Users can still explicitly set this value to whatever they want.
This 'max' behavior is only for the default.
* This allows IPV6_ADDRS_SAFE_TO_USE to default to a /56, which leaves
tons of room for v6 subnetpools.
Closes-Bug: #1629133
Change-Id: I7b32804d47bec743c0b13e434e6a7958728896ea
4bfbc291ee