View Source OneDHCPD.IPCalculator (one_dhcpd v2.0.1)

This module handles IP address calculations.

The most involved of the calculations is the determination of a good IP subnet to use. OneDHCPD subnet tries for the following:

  • Subnets should be the same across reboots (convenience and no surprise conflicts)
  • Support running on more than one interface (unique subnets on device)
  • Support hosts than have more than one device (unique subnets between devices)
  • Don't conflict with the IPs used on the host for Internet

The algorithm here is to hash the hostname (uniqueness between devices assuming the hostname is unique) and the network interface (uniqueness on device). Then use those bits to pick a subnet in the 172.31.0.0/16 private address range. That private range was picked arbitrarily since 10.0.0.0/8 and 192.168.0.0/16 ranges are commonly used. 172.18.0.0/16 is used by Docker.

Link to this section Summary

Functions

Calculate the default subnet for the specified Ethernet interface.

Calculate the default subnet for the specified Ethernet interface and specify the hostname manually.

Return the subnet mask.

Return our IP address. This is the one that should be set as a static address on the interface if using the defaults.

Return the prefix length that OneDHCPD uses.

Return the IP address that's given out to the client.

Link to this section Functions

@spec default_subnet(String.t()) :: :inet.ip4_address()

Calculate the default subnet for the specified Ethernet interface.

Link to this function

default_subnet(ifname, hostname)

View Source
@spec default_subnet(String.t(), String.t()) :: :inet.ip4_address()

Calculate the default subnet for the specified Ethernet interface and specify the hostname manually.

@spec mask() :: :inet.ip4_address()

Return the subnet mask.

Currently this is hardcoded to a /30 network.

@spec our_ip_address(:inet.ip4_address()) :: :inet.ip4_address()

Return our IP address. This is the one that should be set as a static address on the interface if using the defaults.

@spec prefix_length() :: 30

Return the prefix length that OneDHCPD uses.

@spec their_ip_address(:inet.ip4_address()) :: :inet.ip4_address()

Return the IP address that's given out to the client.