host-local IPAM allocates IPv4 and IPv6 addresses out of a specified address range. Optionally, it can include a DNS configuration from a resolv.conf file on the host.

Overview

host-local IPAM plugin allocates IPv4 addresses out of a specified address range. It stores the state locally on the host filesystem, therefore ensuring uniqueness of IP addresses on a single host.

Example configurations

IPv4:

{
	"ipam": {
		"type": "host-local",
		"subnet": "10.10.0.0/16",
		"rangeStart": "10.10.1.20",
		"rangeEnd": "10.10.3.50",
		"gateway": "10.10.0.254",
		"routes": [
			{ "dst": "0.0.0.0/0" },
			{ "dst": "192.168.0.0/16", "gw": "10.10.5.1" }
		],
		"dataDir": "/var/my-orchestrator/container-ipam-state"
	}
}

IPv6:

{
  "ipam": {
		"type": "host-local",
		"subnet": "3ffe:ffff:0:01ff::/64",
		"rangeStart": "3ffe:ffff:0:01ff::0010",
		"rangeEnd": "3ffe:ffff:0:01ff::0020",
		"routes": [
			{ "dst": "3ffe:ffff:0:01ff::1/64" }
		],
		"resolvConf": "/etc/resolv.conf"
	}
}

We can test it out on the command-line:

$ export CNI_COMMAND=ADD
$ export CNI_CONTAINERID=f81d4fae-7dec-11d0-a765-00a0c91e6bf6
$ echo '{ "name": "default", "ipam": { "type": "host-local", "subnet": "203.0.113.0/24" } }' | ./host-local

{
    "ip4": {
        "ip": "203.0.113.1/24"
    }
}

Network configuration reference

type (string, required): "host-local".
subnet (string, required): CIDR block to allocate out of.
rangeStart (string, optional): IP inside of "subnet" from which to start allocating addresses. Defaults to ".2" IP inside of the "subnet" block.
rangeEnd (string, optional): IP inside of "subnet" with which to end allocating addresses. Defaults to ".254" IP inside of the "subnet" block.
gateway (string, optional): IP inside of "subnet" to designate as the gateway. Defaults to ".1" IP inside of the "subnet" block.
routes (string, optional): list of routes to add to the container namespace. Each route is a dictionary with "dst" and optional "gw" fields. If "gw" is omitted, value of "gateway" will be used.
resolvConf (string, optional): Path to a resolv.conf on the host to parse and return as the DNS configuration
dataDir (string, optional): Path to a directory to use for maintaining state, e.g. which IPs have been allocated to which containers

Supported arguments

The following CNI_ARGS are supported:

ip: request a specific IP address from the subnet. If it's not available, the plugin will exit with an error

Files

Allocated IP addresses are stored as files in /var/lib/cni/networks/$NETWORK_NAME. The prefix can be customized with the dataDir option listed above.