OVPN-505 — Address pushing in OPENVPN must respect the INTERFACE type
Addresses that are being pushed to the clients must respect the interface type. Namely, for the TUN interface, only the 'inner' addresses from the particular /30 network can be used.
For example, for TUN address range 10.8.0.1/24, the first address suitable for client 10.8.0.5 (or 10.8.0.6 ), being the first usable address from subnet 10.8.0.4/30. Next one would be 10.8.0.9 (or 10.8.0.10). In another words, the address suitable address for client if it is congruent with 1 or 2 modulo 4. Moreover, from each /30 network, only one address can be used at the moment.