89 lines
2.7 KiB
Markdown
89 lines
2.7 KiB
Markdown
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# flannel plugin
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## Overview
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This plugin is designed to work in conjunction with [flannel](https://github.com/coreos/flannel), a network fabric for containers.
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When flannel daemon is started, it outputs a `/run/flannel/subnet.env` file that looks like this:
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```
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FLANNEL_NETWORK=10.1.0.0/16
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FLANNEL_SUBNET=10.1.17.1/24
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FLANNEL_MTU=1472
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FLANNEL_IPMASQ=true
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```
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This information reflects the attributes of flannel network on the host.
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The flannel CNI plugin uses this information to configure another CNI plugin, such as bridge plugin.
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## Operation
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Given the following network configuration file and the contents of `/run/flannel/subnet.env` above,
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```
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{
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"name": "mynet",
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"type": "flannel"
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}
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```
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the flannel plugin will generate another network configuration file:
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```
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{
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"name": "mynet",
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"type": "bridge",
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"mtu": 1472,
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"ipMasq": false,
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"isGateway": true,
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"ipam": {
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"type": "host-local",
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"subnet": "10.1.17.0/24"
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}
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}
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```
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It will then invoke the bridge plugin, passing it the generated configuration.
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As can be seen from above, the flannel plugin, by default, will delegate to the bridge plugin.
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If additional configuration values need to be passed to the bridge plugin, it can be done so via the `delegate` field:
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```
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{
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"name": "mynet",
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"type": "flannel",
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"delegate": {
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"bridge": "mynet0",
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"mtu": 1400
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}
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}
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```
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This supplies a configuration parameter to the bridge plugin -- the created bridge will now be named `mynet0`.
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Notice that `mtu` has also been specified and this value will not be overwritten by flannel plugin.
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Additionally, the `delegate` field can be used to select a different kind of plugin altogether.
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To use `ipvlan` instead of `bridge`, the following configuration can be specified:
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```
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{
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"name": "mynet",
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"type": "flannel",
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"delegate": {
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"type": "ipvlan",
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"master": "eth0"
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}
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}
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```
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## Network configuration reference
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* `name` (string, required): the name of the network
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* `type` (string, required): "flannel"
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* `subnetFile` (string, optional): full path to the subnet file written out by flanneld. Defaults to /run/flannel/subnet.env
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* `dataDir` (string, optional): path to directory where plugin will store generated network configuration files. Defaults to `/var/lib/cni/flannel`
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* `delegate` (dictionary, optional): specifies configuration options for the delegated plugin.
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flannel plugin will always set the following fields in the delegated plugin configuration:
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* `name`: value of its "name" field.
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* `ipam`: "host-local" type will be used with "subnet" set to `$FLANNEL_SUBNET`.
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flannel plugin will set the following fields in the delegated plugin configuration if they are not present:
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* `ipMasq`: the inverse of `$FLANNEL_IPMASQ`
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* `mtu`: `$FLANNEL_MTU`
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Additionally, for the bridge plugin, `isGateway` will be set to `true`, if not present.
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