netmgr: Feature: Implement API flag to handle /32 IP configuration with non-local gateway using Peer entry

[suezzelur]

You are given the following:

IP Address: A.B.C.D/32
Gateway: E.F.G.1

Now the default gateway is not on the same subnet as the host.

Here is the /etc/systemd/network/10-eth0.network generated by netmgr:

[Match]
Name=eth0

[Network]
Gateway=62.210.249.1
Address=195.154.58.18/32
DHCP=no

[DHCP]
UseDNS=false

This doesn't work as the OS doesn't know how to join the GW.

Here it what should be generated when a /32 subnet is used for the host in /etc/systemd/network/10-eth0.network

[Match]
Name=eth0

[Address]
Address=195.154.58.18/32
Peer=62.210.249.1/32

[Network]
Gateway=62.210.249.1

[DHCP]
UseDNS=false

[ssahani]

May be use the onlink option

[Match]
Name= eth0

[Address]
Address=195.154.58.18/32

[Route]
Gateway=62.210.249.1
GatewayOnlink=true

[DHCP]
UseDNS=false

[ssahani]

@suezzelur systemd/systemd#10938