Change topology net30 to topology subnet

By default, the OpenVPN server sends to the client the option topology net30

Nov 6 15:58:45 omnia1 openvpn(turris)[8508]: PUSH: Received control message: 'PUSH_REPLY,route 198.18.2.0 255.255.255.0,route 48.0.0.0 255.255.0.0,route 10.111.111.1,topology net30,ping 10,ping-restart 120,ifconfig 10.111.111.6 10.111.111.5,peer-id 0,cipher AES-256-GCM'

This option is deprecated and for legacy clients only (year 2014). By configuring the topology subnet directive, it makes the routing table easier to read and simplifies the routing.

uci set openvpn.server_turris.topology='subnet'

Nov 6 16:10:42 omnia1 openvpn(turris)[11847]: PUSH: Received control message: 'PUSH_REPLY,route 198.18.2.0 255.255.255.0,route 48.0.0.0 255.255.0.0,route-gateway 10.111.111.1,topology subnet,ping 10,ping-restart 120,ifconfig 10.111.111.4 255.255.255.0,peer-id 0,cipher AES-256-GCM'

OpenVPN Topology