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Merge pull request #369 from containernetworking/port-mapping

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CONVENTIONS.md: Update details on port-mappings
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Tom Denham 2017-02-14 11:47:59 -08:00 committed by GitHub
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CONVENTIONS.md
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@ -10,9 +10,11 @@ Establishing these conventions allows plugins to work across multiple runtimes.
## Plugins
* Plugin authors should aim to support these conventions where it makes sense for their plugin. This means they are more likely to "just work" with a wider range of runtimes.
* Plugins should accept arguments according to these conventions if they implement the same basic functionality as other plugins. If plugins have shared functionality that isn't coverered by these conventions then a PR should be opened against this document.
## Runtimes
* Runtime authors should follow these conventions if they want to pass additional information to plugins. This will allow the extra information to be consumed by the widest range of plugins.
* These conventions serve as an abstraction for the runtime. For example, port forwarding is highly implementation specific, but users should be able to select the plugin of their choice without changing the runtime.
# Current conventions
Additional conventions can be created by creating PRs which modify this document.
@ -21,13 +23,39 @@ Additional conventions can be created by creating PRs which modify this document
[Plugin specific fields](https://github.com/containernetworking/cni/blob/master/SPEC.md#network-configuration) formed part of the original CNI spec and have been present since the initial release.
> Plugins may define additional fields that they accept and may generate an error if called with unknown fields. The exception to this is the args field may be used to pass arbitrary data which may be ignored by plugins.
A plugin can define any additional fields it needs to work properly. It is expected that it will return an error if if can't act on fields that were expected or where the field values were malformed.
A plugin can define any additional fields it needs to work properly. It is expected that it will return an error if it can't act on fields that were expected or where the field values were malformed.
This method of passing information to a plugin is recommended when the information should be acted on and has specific meaning to that plugin.
This method of passing information to a plugin is recommended when the following conditions hold
* The configuration has specific meaning to the plugin (i.e. it's not just general meta data)
* the plugin is expected to act on the configuration or return an error if it can't
Dynamic information (i.e. data that a runtime fills out) should be placed in a `runtime_config` section.
| Area | Purpose| Spec and Example | Runtime implementations | Plugin Implementations |
| ------ | ------ | ------ | ------ | ------ | ------ |
| port mappings | Pass mapping from ports on the host to ports in the container network namespace. | <pre>"port_mappings" : [<br /> { "host_port": 8080, "container_port": 80, "protocol": "tcp" },<br /> { "host_port": 8000, "container_port": 8001, "protocol": "udp" }<br />] </pre> | none | none |
| port mappings | Pass mapping from ports on the host to ports in the container network namespace. | Operators can ask runtimes to pass port mapping information to plugins, by setting the following in the CNI config <pre>"capabilities": {port_mappings": true} </pre> Runtimes should fill in the actual port mappings when the config is passed to plugins. It should be placed in a new section of the config "runtime_config" e.g. <pre>"runtime_config": {<br /> "port_mappings" : [<br /> { "host_port": 8080, "container_port": 80, "protocol": "tcp" },<br /> { "host_port": 8000, "container_port": 8001, "protocol": "udp" }<br /> ]<br />}</pre> | none | none |
For example, the configuration for a port mapping plugin might look like this to an operator (it should be included as part of a [network configuration list](https://github.com/containernetworking/cni/blob/master/SPEC.md#network-configuration-lists).
```json
{
"name" : "ExamplePlugin",
"type" : "port-mapper",
"capabilities": {"port_mappings": true}
}
```
But the runtime would fill in the mappings so the plugin itself would receive something like this.
```json
{
"name" : "ExamplePlugin",
"type" : "port-mapper",
"runtime_config": {
"port_mappings": [
{"host_port": 8080, "container_port": 80, "protocol": "tcp"}
]
}
}
```
## "args" in network config
`args` in [network config](https://github.com/containernetworking/cni/blob/master/SPEC.md#network-configuration) were introduced as an optional field into the `0.1.0` CNI spec. The first CNI code release that it appeared in was `v0.4.0`.