Node Feature Discovery

# Customization guide

## Table of contents

## Overview

NFD provides multiple extension points for vendor and application specific labeling:

- `NodeFeature` objects can be used to communicate "raw" node features and node labeling requests to nfd-master.
- `NodeFeatureRule` objects provide a way to deploy custom labeling rules via the Kubernetes API.
- `local` feature source of nfd-worker creates labels by reading text files and executing hooks.
- `custom` feature source of nfd-worker creates labels based on user-specified rules.

## NodeFeature custom resource

NodeFeature objects provide a way for 3rd party extensions to advertise custom features, both as "raw" features that serve as input to NodeFeatureRule objects and as feature labels directly.

Note that RBAC rules must be created for each extension for them to be able to create and manipulate NodeFeature objects in their namespace.

The NodeFeature CRD API can be disabled with the NodeFeatureAPI feature gate (`-feature-gates NodeFeatureAPI=false` on command line). The `-feature-gates` command line flag must be specified for both nfd-master and nfd-worker as it will enable the gRPC communication between them. Note that the gRPC API is DEPRECATED and will be removed in a future release, at which point the NodeFeature API cannot be disabled.

### A NodeFeature example

Consider the following referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeature
    metadata:
      labels:
        nfd.node.kubernetes.io/node-name: node-1
      name: vendor-features-for-node-1
    spec:
      # Features for NodeFeatureRule matching
      features:
        flags:
          vendor.flags:
            elements:
              feature-x: {}
              feature-y: {}
        attributes:
          vendor.config:
            elements:
              setting-a: "auto"
              knob-b: "123"
        instances:
          vendor.devices:
            elements:
            - attributes:
                model: "dev-1000"
                vendor: "acme"
            - attributes:
                model: "dev-2000"
                vendor: "acme"
      # Labels to be created
      labels:
        vendor.io/feature.enabled: "true"

The object targets node named `node-1`. It lists two "flag type" features under the `vendor.flags` domain, two "attribute type" features and under the `vendor.config` domain and two "instance type" features under the `vendor.devices` domain. These features will not be directly affecting the node labels but they will be used as input when the `NodeFeatureRule` objects are evaluated.

In addition, the example requests directly the `vendor.io/feature.enabled=true` node label to be created.

The `nfd.node.kubernetes.io/node-name=<node-name>` must be in place for each NodeFeature object as NFD uses it to determine the node which it is targeting.

### Feature types

Features have three different types:

- flag features: a set of names without any associated values, e.g. CPUID flags or loaded kernel modules
- attribute features: a set of names each of which has a single value associated with it (essentially a map of key-value pairs), e.g. kernel config flags or os release information
- instance features: a list of instances, each of which has multiple attributes (key-value pairs of their own) associated with it, e.g. PCI or USB devices

## NodeFeatureRule custom resource

`NodeFeatureRule` objects provide an easy way to create vendor or application specific labels and taints. It uses a flexible rule-based mechanism for creating labels and optionally taints based on node features.

### A NodeFeatureRule example

Consider the following referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-sample-rule-object
    spec:
      rules:
        - name: "my sample rule"
          labels:
            "feature.node.kubernetes.io/my-sample-feature": "true"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

It specifies one rule which creates node label `feature.node.kubernetes.io/my-sample-feature=true` if both of the following conditions are true (`matchFeatures` implements a logical AND over the matchers):

- The `dummy` network driver module has been loaded
- X86 option in kernel config is set to `=y`

Create a `NodeFeatureRule` with a yaml file:

    kubectl apply -f https://raw.githubusercontent.com/kubernetes-sigs/node-feature-discovery/master/examples/nodefeaturerule.yaml

Now, on X86 platforms the feature label appears after doing `modprobe dummy` on a system and correspondingly the label is removed after `rmmod dummy`. Note a re-labeling delay up to the sleep-interval of nfd-worker (1 minute by default).

See Feature rule format for detailed description of available fields and how to write labeling rules.

### Node tainting

This feature is experimental.

In some circumstances, it is desirable to keep nodes with specialized hardware away from running general workload and instead leave them for workloads that need the specialized hardware. One way to achieve it is to taint the nodes with the specialized hardware and add corresponding toleration to pods that require the special hardware. NFD offers node tainting functionality which is disabled by default. User can define one or more custom taints via the `taints` field of the NodeFeatureRule CR. The same rule-based mechanism is applied here and the NFD taints only rule matching nodes.

To enable the tainting feature, `--enable-taints` flag needs to be set to `true`. If the flag `--enable-taints` is set to `false` (i.e. disabled), taints defined in the NodeFeatureRule CR have no effect and will be ignored by the NFD master.

See documentation of the taints field for detailed description how to specify taints in the NodeFeatureRule object.

> NOTE: Before enabling any taints, make sure to edit nfd-worker daemonset to tolerate the taints to be created. Otherwise, already running pods that do not tolerate the taint are evicted immediately from the node including the nfd-worker pod.

## NodeFeatureGroup custom resource

`NodeFeatureGroup` objects provide a way to create node groups that share the same set of features. The `NodeFeatureGroup` object spec consists of a list of `NodeFeatureRule` that follow the same format as the `NodeFeatureRule`, but the difference in this case is that nodes that match any of the rules in the `NodeFeatureGroup` will be listed in the `NodeFeatureGroup` status.

### A NodeFeatureGroup example

Consider the following referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureGroup
    metadata:
      name: node-feature-group-example
    spec:
      featureGroupRules:
        - name: "kernel version"
          matchFeatures:
            - feature: kernel.version
              matchExpressions:
                major: {op: In, value: ["6"]}
    status:
      nodes:
        - name: node-1
        - name: node-2
        - name: node-3

The object specifies a group of nodes that share the same `kernel.version.major` (Linux kernel v6.x).

Create a `NodeFeatureGroup` with a yaml file:

    kubectl apply -f https://raw.githubusercontent.com/kubernetes-sigs/node-feature-discovery/master/examples/nodefeaturegroup.yaml

See Feature rule format for detailed description of available fields and how to write group filtering rules.

## Local feature source

NFD-Worker has a special feature source named `local` which is an integration point for external feature detectors. It provides a mechanism for pluggable extensions, allowing the creation of new user-specific features and even overriding built-in labels.

The `local` feature source has two methods for detecting features, feature files and hooks (hooks are deprecated and slated for removal in NFD v0.17). The features discovered by the `local` source can further be used in label rules specified in `NodeFeatureRule` objects and the `custom` feature source.

> NOTE: Be careful when creating and/or updating hook or feature files while NFD is running. To avoid race conditions you should write into a temporary file, and atomically create/update the original file by doing a file rename operation. NFD ignores dot files, so temporary file can be written to the same directory and renamed (`.my.feature` -> `my.feature`) once file is complete. Both file names should (obviously) be unique for the given application.

### An example

Consider a plaintext file `/etc/kubernetes/node-feature-discovery/features.d/my-features` having the following contents (or alternatively a shell script `/etc/kubernetes/node-feature-discovery/source.d/my-hook.sh` having the following stdout output):

    feature.node.kubernetes.io/my-feature.1
    feature.node.kubernetes.io/my-feature.2=myvalue
    vendor.io/my-feature.3=456

This will translate into the following node labels:

    feature.node.kubernetes.io/my-feature.1: "true"
    feature.node.kubernetes.io/my-feature.2: "myvalue"
    vendor.io/my-feature.3: "456"

### Feature files

The `local` source reads files found in `/etc/kubernetes/node-feature-discovery/features.d/`. File content is parsed and translated into node labels, see the input format below.

### Hooks

DEPRECATED Hooks are deprecated and will be completely removed in NFD v0.17.

The `local` source executes hooks found in `/etc/kubernetes/node-feature-discovery/source.d/`. The hook files must be executable and they are supposed to print all discovered features in `stdout`. Since NFD v0.13 the default container image only supports statically linked ELF binaries.

`stderr` output of hooks is propagated to NFD log so it can be used for debugging and logging.

NFD tries to execute any regular files found from the hooks directory. Any additional data files the hook might need (e.g. a configuration file) should be placed in a separate directory to avoid NFD unnecessarily trying to execute them. A subdirectory under the hooks directory can be used, for example `/etc/kubernetes/node-feature-discovery/source.d/conf/`.

> NOTE: Starting from release v0.14 hooks are disabled by default and can be enabled via `sources.local.hooksEnabled` field in the worker configuration.

    sources:
      local:
        hooksEnabled: true  # true by default at this point

> NOTE: NFD will blindly run any executables placed/mounted in the hooks directory. It is the user's responsibility to review the hooks for e.g. possible security implications.

> NOTE: The full image variant provides backwards-compatibility with older NFD versions by including a more expanded environment, supporting bash and perl runtimes.

### Input format

The hook stdout and feature files are expected to contain features in simple key-value pairs, separated by newlines:

    # This is a comment
    <key>[=<value>]

The label value defaults to `true`, if not specified.

Label namespace must be specified with `<namespace>/<name>[=<value>]`.

> NOTE: The feature file size limit it 64kB. The feature file will be ignored if the size limit is exceeded.

Comment lines (starting with `#`) are ignored.

Adding following line anywhere to feature file defines date when its content expires / is ignored:

    # +expiry-time=2023-07-29T11:22:33Z

Also, the expiry-time value would stay the same during the processing of the feature file until another expiry-time directive is encountered. Considering the following file:

    # +expiry-time=2012-07-28T11:22:33Z
    vendor.io/feature1=featureValue

    # +expiry-time=2080-07-28T11:22:33Z
    vendor.io/feature2=featureValue2

    # +expiry-time=2070-07-28T11:22:33Z
    vendor.io/feature3=featureValue3

    # +expiry-time=2002-07-28T11:22:33Z
    vendor.io/feature4=featureValue4

After processing the above file, only `vendor.io/feature2` and `vendor.io/feature3` would be included in the list of accepted features.

> NOTE: The time format supported is RFC3339. Also, the `expiry-time` tag is only evaluated in each re-discovery period, and the expiration of node labels is not tracked.

To exclude specific features from the `local.feature` Feature, you can use the `# +no-feature` directive. The `# +no-label` directive causes the feature to be excluded from the `local.label` Feature and a node label not to be generated.

Considering the following file:

    # +no-feature
    vendor.io/label-only=value

    vendor.io/my-feature=value

    vendor.io/foo=bar

    # +no-label
    foo=baz

Processing the above file would result in the following Features:

    local.features:
      foo: baz
      vendor.io/my-feature: value
    local.labels:
      vendor.io/label-only: value
      vendor.io/my-feature: value

and the following labels added to the Node:

    vendor.io/label-only=value
    vendor.io/my-feature=value

> NOTE: use of unprefixed label names (like `foo=bar`) should not be used. In NFD master unprefixed names will be automatically prefixed with `feature.node.kubernetes.io/` but this will change in a future version (see autoDefaultNs config option. Unprefixed names for plain Features (tagged with `# +no-label`) can be used without restrictions, however.

### Mounts

The standard NFD deployments contain `hostPath` mounts for `/etc/kubernetes/node-feature-discovery/source.d/` and `/etc/kubernetes/node-feature-discovery/features.d/`, making these directories from the host available inside the nfd-worker container.

#### Injecting labels from other pods

One use case for the feature files and hooks is detecting features in other Pods outside NFD, e.g. in Kubernetes device plugins. By using the same `hostPath` mounts for `/etc/kubernetes/node-feature-discovery/source.d/` and `/etc/kubernetes/node-feature-discovery/features.d/` in the side-car (e.g. device plugin) creates a shared area for deploying feature files and hooks to NFD. NFD periodically scans the directories and reads any feature files and runs any hooks it finds.

## Custom feature source

The `custom` feature source in nfd-worker provides a rule-based mechanism for label creation, similar to the `NodeFeatureRule` objects. The difference is that the rules are specified in the worker configuration instead of a Kubernetes API object.

See worker configuration for instructions how to set-up and manage the worker configuration.

### An example custom feature source configuration

Consider the following referential configuration for nfd-worker:

    core:
      labelSources: ["custom"]
    sources:
      custom:
        - name: "my sample rule"
          labels:
            "feature.node.kubenernetes.io/my-sample-feature": "true"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

It specifies one rule which creates node label `feature.node.kubenernetes.io/my-sample-feature=true` if both of the following conditions are true (`matchFeatures` implements a logical AND over the matchers):

- The `dummy` network driver module has been loaded
- X86 option in kernel config is set to `=y`

In addition, the configuration only enables the `custom` source, disabling all built-in labels.

Now, on X86 platforms the feature label appears after doing `modprobe dummy` on a system and correspondingly the label is removed after `rmmod dummy`. Note a re-labeling delay up to the sleep-interval of nfd-worker (1 minute by default).

### Additional configuration directory

In addition to the rules defined in the nfd-worker configuration file, the `custom` feature source can read more configuration files located in the `/etc/kubernetes/node-feature-discovery/custom.d/` directory. This makes more dynamic and flexible configuration easier.

As an example, consider having file `/etc/kubernetes/node-feature-discovery/custom.d/my-rule.yaml` with the following content:

    - name: "my e1000 rule"
      labels:
        "feature.node.kubenernetes.io/e1000.present": "true"
      matchFeatures:
        - feature: kernel.loadedmodule
          matchExpressions:
            e1000: {op: Exists}

This simple rule will create `feature.node.kubenernetes.io/e1000.present=true` label if the `e1000` kernel module has been loaded.

The `samples/custom-rules` kustomize overlay sample contains an example for deploying a custom rule from a ConfigMap.

## Node labels

Feature labels have the following format:

    <namespace>/<name> = <value>

The namespace part (i.e. prefix) of the labels is controlled by nfd:

- All built-in labels use `feature.node.kubernetes.io`.
- Namespaces may be excluded with the `-deny-label-ns` command line flag of nfd-master
  - To allow specific namespaces that were denied, you can use `-extra-label-ns` command line flag of nfd-master. e.g: `nfd-master -deny-label-ns="*" -extra-label-ns=example.com`

## Feature rule format

This section describes the rule format used in `NodeFeatureRule` objects and in the configuration of the `custom` feature source.

It is based on a generic feature matcher that covers all features discovered by nfd-worker. The rules rely on a unified data model of the available features and a generic expression-based format. Features that can be used in the rules are described in detail in available features below.

Take this rule as a referential example:

        - name: "my feature rule"
          labels:
            "feature.node.kubernetes.io/my-special-feature": "my-value"
          matchFeatures:
            - feature: cpu.cpuid
              matchExpressions:
                AVX512F: {op: Exists}
            - feature: kernel.version
              matchExpressions:
                major: {op: In, value: ["5"]}
                minor: {op: Gt, value: ["1"]}
            - feature: pci.device
              matchExpressions:
                vendor: {op: In, value: ["8086"]}
                class: {op: In, value: ["0200"]}

This will yield `feature.node.kubernetes.io/my-special-feature=my-value` node label if all of these are true (`matchFeatures` implements a logical AND over the matchers):

- the CPU has AVX512F capability
- kernel version is 5.2 or later (must be v5.x)
- an Intel network controller is present

### Fields

#### name

The `.name` field is required and used as an identifier of the rule.

#### labels

The `.labels` is a map of the node labels to create if the rule matches.

Take this rule as a referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-sample-rule-object
    spec:
      rules:
        - name: "my dynamic label value rule"
          labels:
            feature.node.kubernetes.io/linux-lsm-enabled: "@kernel.config.LSM"
            feature.node.kubernetes.io/custom-label: "customlabel"

Label `linux-lsm-enabled` uses the `@` notation for dynamic values. The value of the label will be the value of the attribute `LSM` of the feature `kernel.config`.

The `@<feature-name>.<element-name>` format can be used to inject values of detected features to the label. See available features for possible values to use.

This will yield into the following node label:

      labels:
        ...
        feature.node.kubernetes.io/linux-lsm-enabled: apparmor
        feature.node.kubernetes.io/custom-label: "customlabel"

#### labelsTemplate

The `.labelsTemplate` field specifies a text template for dynamically creating labels based on the matched features. See templating for details.

> NOTE: The `labels` field has priority over `labelsTemplate`, i.e. labels specified in the `labels` field will override anything originating from `labelsTemplate`.

#### annotations

The `.annotations` field is a list of features to be advertised as node annotations.

Take this rule as a referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: feature-annotations-example
    spec:
      rules:
        - name: "annotation-example"
          annotations:
            feature.node.kubernetes.io/defaul-ns-annotation: "foo"
            custom.vendor.io/feature: "baz"
          matchFeatures:
            - feature: kernel.version
              matchExpressions:
                major: {op: Exists}

This will yield into the following node annotations:

      annotations:
        ...
        feature.node.kubernetes.io/defaul-ns-annotation: "foo"
        custom.vendor.io/feature: "baz"
        ...

NFD enforces some limitations to the namespace (or prefix)/ of the annotations:

- `kubernetes.io/` and its sub-namespaces (like `sub.ns.kubernetes.io/`) cannot generally be used
- the only exception is `feature.node.kubernetes.io/` and its sub-namespaces (like `sub.ns.feature.node.kubernetes.io`)
- unprefixed names (like `my-annotation`) should not be used. In NFD master unprefixed names will be automatically prefixed with `feature.node.kubernetes.io/` but this will change in a future version (see autoDefaultNs config option.

> NOTE: The `annotations` field has will only advertise features via node annotations the features won't be advertised as node labels unless they are specified in the `labels` field.

#### taints

taints is a list of taint entries and each entry can have `key`, `value` and `effect`, where the `value` is optional. Effect could be `NoSchedule`, `PreferNoSchedule` or `NoExecute`. To learn more about the meaning of these effects, check out k8s documentation.

Example NodeFeatureRule with taints:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-sample-rule-object
    spec:
      rules:
        - name: "my sample taint rule"
          taints:
            - effect: PreferNoSchedule
              key: "feature.node.kubernetes.io/special-node"
              value: "true"
            - effect: NoExecute
              key: "feature.node.kubernetes.io/dedicated-node"
          matchFeatures:
            - feature: kernel.loadedmodule
              matchExpressions:
                dummy: {op: Exists}
            - feature: kernel.config
              matchExpressions:
                X86: {op: In, value: ["y"]}

In this example, if the `my sample taint rule` rule is matched, `feature.node.kubernetes.io/pci-0300_1d0f.present=true:NoExecute` and `feature.node.kubernetes.io/cpu-cpuid.ADX:NoExecute` taints are set on the node.

There are some limitations to the namespace part (i.e. prefix/) of the taint key:

- `kubernetes.io/` and its sub-namespaces (like `sub.ns.kubernetes.io/`) cannot generally be used
- the only exception is `feature.node.kubernetes.io/` and its sub-namespaces (like `sub.ns.feature.node.kubernetes.io`)
- unprefixed keys (like `foo`) keys are disallowed

> NOTE: taints field is not available for the custom rules of nfd-worker and only for NodeFeatureRule objects.

#### vars

The `.vars` field is a map of values (key-value pairs) to store for subsequent rules to use. In other words, these are variables that are not advertised as node labels. See backreferences for more details on the usage of vars.

#### extendedResources

The `.extendedResources` field is a list of extended resources to advertise. See extended resources for more details.

Take this rule as a referential example:

    apiVersion: nfd.k8s-sigs.io/v1alpha1
    kind: NodeFeatureRule
    metadata:
      name: my-extended-resource-rule
    spec:
      rules:
        - name: "my extended resource rule"
          extendedResources:
            vendor.io/dynamic: "@kernel.version.major"
            vendor.io/static: "123"
          matchFeatures:
            - feature: kernel.version
              matchExpressions:
                major: {op: Exists}

The extended resource `vendor.io/dynamic` is defined in the form `@feature.attribute`. The value of the extended resource will be the value of the attribute `major` of the feature `kernel.version`.

The `@<feature-name>.<element-name>` format can be used to inject values of detected features to the extended resource. See available features for possible values to use. Note that the value must be eligible as a Kubernetes resource quantity.

This will yield into the following node status:

      allocatable:
        ...
        vendor.io/dynamic: "5"
        vendor.io/static: "123"
        ...
      capacity:
        ...
        vendor.io/dynamic: "5"
        vendor.io/static: "123"
        ...

There are some limitations to the namespace part (i.e. prefix)/ of the Extended Resources names:

- `kubernetes.io/` and its sub-namespaces (like `sub.ns.kubernetes.io/`) cannot generally be used
- the only exception is `feature.node.kubernetes.io/` and its sub-namespaces (like `sub.ns.feature.node.kubernetes.io`)
- unprefixed names (like `my-er`) site.version }} unprefixed names will be automatically prefixed with `feature.node.kubernetes.io/` but this will change in a future version (see autoDefaultNs config option.

> NOTE: `.extendedResources` is not supported by the custom feature source – it can only be used in NodeFeatureRule objects.

#### varsTemplate

The `.varsTemplate` field specifies a text template for dynamically creating vars based on the matched features. See templating for details on using templates and backreferences for more details on the usage of vars.

> NOTE: The `vars` field has priority over `varsTemplate`, i.e. vars specified in the `vars` field will override anything originating from `varsTemplate`.

#### matchFeatures

The `.matchFeatures` field specifies a feature matcher, consisting of a list of feature matcher terms. It implements a logical AND over the terms i.e. all of them must match for the rule to trigger.

          matchFeatures:
            - feature: <feature-name>
              matchExpressions:
                <key>:
                  op: <op>
                  value:
                    - <value-1>
                    - ...
              matchName:
                op: <op>
                value:
                    - <value-1>
                    - ...

The `.matchFeatures[].feature` field specifies the feature which to evaluate.

> NOTE:If both `matchExpressions` and `matchName` are specified, they both must match.

##### matchExpressions

The `.matchFeatures[].matchExpressions` field is used to match against the value(s) of a feature. The `matchExpressions` field consists of a set of expressions, each of which is evaluated against all elements of the specified feature.

          matchExpressions:
            <key>:
              op: <op>
              value:
                - <value-1>
                - ...

In each MatchExpression the `key` specifies the name of of the feature element (flag and attribute features) or name of the attribute (instance features) which to look for. The behavior of MatchExpression depends on the feature type:

- for flag and attribute features the MatchExpression operates on the feature element whose name matches the `<key>`
- for instance features all MatchExpressions are evaluated against the attributes of each instance separately

The `op` field specifies the operator to apply. Valid values are described below.

Operator | Number of values | Matches when
--- | --- | ---
`In` | 1 or greater | Input is equal to one of the values
`NotIn` | 1 or greater | Input is not equal to any of the values
`InRegexp` | 1 or greater | Values of the MatchExpression are treated as regexps and input matches one or more of them
`Exists` | 0 | The key exists
`DoesNotExist` | 0 | The key does not exists
`Gt` | 1 | Input is greater than the value. Both the input and value must be integer numbers.
`Lt` | 1 | Input is less than the value. Both the input and value must be integer numbers.
`GtLt` | 2 | Input is between two values. Both the input and value must be integer numbers.
`IsTrue` | 0 | Input is equal to "true"
`IsFalse` | 0 | Input is equal "false"

The `value` field of MatchExpression is a list of string arguments to the operator.

##### matchName

The `.matchFeatures[].matchName` field is used to match against the name(s) of a feature (whereas the `matchExpressions` field matches against the value(s). The `matchName` field consists of a single expression which is evaulated against the name of each element of the specified feature.

          matchName:
            op: <op>
            value:
              - <value-1>
              - ...

The behavior of `matchName` depends on the feature type:

- for flag and attribute features the expression is evaluated against the name of each element
- for instance features the expression is evaluated against the name of each attribute, for each element (instance) separately (matches if the attributes of any of the elements satisfy the expression)

The `op` field specifies the operator to apply. Same operators as for `matchExpressions` above are available.

Operator | Number of values | Matches
--- | --- | ---
`In` | 1 or greater | All name is equal to one of the values
`NotIn` | 1 or greater | All name that is not equal to any of the values
`InRegexp` | 1 or greater | All name that matches any of the values (treated as regexps)
`Exists` | 0 | All elements

Other operators are not practical with `matchName` (`DoesNotExist` never matches; `Gt`,`Lt` and `GtLt` are only usable if feature names are integers; `IsTrue` and `IsFalse` are only usable if the feature name is `true` or `false`).

The `value` field is a list of string arguments to the operator.

An example:

          matchFeatures:
            - feature: cpu.cpuid
              matchName: {op: InRegexp, value: ["^AVX"]}

The snippet above would match if any CPUID feature starting with AVX is present (e.g. AVX1 or AVX2 or AVX512F etc).

#### matchAny

The `.matchAny` field is a list of of `matchFeatures` matchers. A logical OR is applied over the matchers, i.e. at least one of them must match for the rule to trigger.

Consider the following example:

          matchAny:
            - matchFeatures:
                - feature: kernel.loadedmodule
                  matchExpressions:
                    kmod-1: {op: Exists}
                - feature: pci.device
                  matchExpressions:
                    vendor: {op: In, value: ["0eee"]}
                    class: {op: In, value: ["0200"]}
            - matchFeatures:
                - feature: kernel.loadedmodule
                  matchExpressions:
                    kmod-2: {op: Exists}
                - feature: pci.device
                  matchExpressions:
                    vendor: {op: In, value: ["0fff"]}
                    class: {op: In, value: ["0200"]}

This matches if kernel module kmod-1 is loaded and a network controller from vendor 0eee is present, OR, if kernel module kmod-2 has been loaded and a network controller from vendor 0fff is present (OR both of these conditions are true).

### Available features

The following features are available for matching:

Feature | Feature types | Elements | Value type | Description
--- | --- | --- | --- | ---
`cpu.cpuid` | flag |  |  | Supported CPU capabilities
|  | `<cpuid-flag>` |  | CPUID flag is present
| attribute |  |  | CPU capability attributes
|  | AVX10_VERSION | int | AVX10 vector ISA version (if supported)
`cpu.cstate` | attribute |  |  | Status of cstates in the intel_idle cpuidle driver
|  | `enabled` | bool | ‘true' if cstates are set, otherwise ‘false'. Does not exist of intel_idle driver is not active.
`cpu.model` | attribute |  |  | CPU model related attributes
|  | `family` | int | CPU family
|  | `vendor_id` | string | CPU vendor ID
|  | `id` | int | CPU model ID
`cpu.pstate` | attribute |  |  | State of the Intel pstate driver. Does not exist if the driver is not enabled.
|  | `status` | string | Status of the driver, possible values are ‘active' and ‘passive'
|  | `turbo` | bool | ‘true' if turbo frequencies are enabled, otherwise ‘false'
|  | `scaling` | string | Active scaling_governor, possible values are ‘powersave' or ‘performance'.
`cpu.rdt` | attribute |  |  | Intel RDT capabilities supported by the system
|  | `<rdt-flag>` |  | RDT capability is supported, see RDT flags for details
|  | `RDTL3CA_NUM_CLOSID` | int | The number or available CLOSID (Class of service ID) for Intel L3 Cache Allocation Technology
`cpu.security` | attribute |  |  | Features related to security and trusted execution environments
|  | `sgx.enabled` | bool | `true` if Intel SGX (Software Guard Extensions) has been enabled, otherwise does not exist
|  | `sgx.epc` | int | The total amount Intel SGX Encrypted Page Cache memory in bytes. It's only present if `sgx.enabled` is `true`.
|  | `se.enabled` | bool | `true` if IBM Secure Execution for Linux is available and has been enabled, otherwise does not exist
|  | `tdx.enabled` | bool | `true` if Intel TDX (Trusted Domain Extensions) is available on the host and has been enabled, otherwise does not exist
|  | `tdx.total_keys` | int | The total amount of keys an Intel TDX (Trusted Domain Extensions) host can provide. It's only present if `tdx.enabled` is `true`.
|  | `tdx.protected` | bool | `true` if a guest VM was started using Intel TDX (Trusted Domain Extensions), otherwise does not exist.
|  | `sev.enabled` | bool | `true` if AMD SEV (Secure Encrypted Virtualization) is available on the host and has been enabled, otherwise does not exist
|  | `sev.es.enabled` | bool | `true` if AMD SEV-ES (Encrypted State supported) is available on the host and has been enabled, otherwise does not exist
|  | `sev.snp.enabled` | bool | `true` if AMD SEV-SNP (Secure Nested Paging supported) is available on the host and has been enabled, otherwise does not exist
|  | `sev.asids` | int | The total amount of AMD SEV address-space identifiers (ASIDs), based on the `/sys/fs/cgroup/misc.capacity` information.
|  | `sev.encrypted_state_ids` | int | The total amount of AMD SEV-ES and SEV-SNP supported, based on the `/sys/fs/cgroup/misc.capacity` information.
`cpu.sst` | attribute |  |  | Intel SST (Speed Select Technology) capabilities
|  | `bf.enabled` | bool | `true` if Intel SST-BF (Intel Speed Select Technology - Base frequency) has been enabled, otherwise does not exist
`cpu.topology` | attribute |  |  | CPU topology related features
|  | `hardware_multithreading` | bool | Hardware multithreading, such as Intel HTT, is enabled
|  | `socket_count` | int | Number of CPU Sockets
`cpu.coprocessor` | attribute |  |  | CPU Coprocessor related features
|  | `nx_gzip` | bool | Nest Accelerator GZIP support is enabled
`kernel.config` | attribute |  |  | Kernel configuration options
|  | `<config-flag>` | string | Value of the kconfig option
`kernel.loadedmodule` | flag |  |  | Kernel modules loaded on the node as reported by `/proc/modules`
`kernel.enabledmodule` | flag |  |  | Kernel modules loaded on the node and available as built-ins as reported by `modules.builtin`
|  | `mod-name` |  | Kernel module `<mod-name>` is loaded
`kernel.selinux` | attribute |  |  | Kernel SELinux related features
|  | `enabled` | bool | `true` if SELinux has been enabled and is in enforcing mode, otherwise `false`
`kernel.version` | attribute |  |  | Kernel version information
|  | `full` | string | Full kernel version (e.g. ‘4.5.6-7-g123abcde')
|  | `major` | int | First component of the kernel version (e.g. ‘4')
|  | `minor` | int | Second component of the kernel version (e.g. ‘5')
|  | `revision` | int | Third component of the kernel version (e.g. ‘6')
`local.label` | attribute |  |  | Labels from feature files and hooks, i.e. labels from the local feature source
`local.feature` | attribute |  |  | Features from feature files and hooks, i.e. features from the local feature source
|  | `<label-name>` | string | Label `<label-name>` created by the local feature source, value equals the value of the label
`memory.nv` | instance |  |  | NVDIMM devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `devtype`, `mode`
`memory.numa` | attribute |  |  | NUMA nodes
|  | `is_numa` | bool | `true` if NUMA architecture, `false` otherwise
|  | `node_count` | int | Number of NUMA nodes
`memory.swap` | attribute |  |  | Swap enabled on node
|  | `enabled` | bool | `true` if swap partition detected, `false` otherwise
`network.device` | instance |  |  | Physical (non-virtual) network interfaces present in the system
|  | `name` | string | Name of the network interface
|  | `<sysfs-attribute>` | string | Sysfs network interface attribute, available attributes: `operstate`, `speed`, `sriov_numvfs`, `sriov_totalvfs`
`network.virtual` | instance |  |  | Virtual network interfaces present in the system
|  | `name` | string | Name of the network interface
|  | `<sysfs-attribute>` | string | Sysfs network interface attribute, available attributes: `operstate`, `speed`
`pci.device` | instance |  |  | PCI devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `class`, `vendor`, `device`, `subsystem_vendor`, `subsystem_device`, `sriov_totalvfs`, `iommu_group/type`, `iommu/intel-iommu/version`
`storage.block` | instance |  |  | Block storage devices present in the system
|  | `name` | string | Name of the block device
|  | `<sysfs-attribute>` | string | Sysfs network interface attribute, available attributes: `dax`, `rotational`, `nr_zones`, `zoned`
`system.osrelease` | attribute |  |  | System identification data from `/etc/os-release`
|  | `<parameter>` | string | One parameter from `/etc/os-release`
`system.dmiid` | attribute |  |  | DMI identification data from `/sys/devices/virtual/dmi/id/`
|  | `sys_vendor` | string | Vendor name from `/sys/devices/virtual/dmi/id/sys_vendor`
`system.name` | attribute |  |  | System name information
|  | `nodename` | string | Name of the kubernetes node object
`usb.device` | instance |  |  | USB devices present in the system
|  | `<sysfs-attribute>` | string | Value of the sysfs device attribute, available attributes: `class`, `vendor`, `device`, `serial`
`rule.matched` | attribute |  |  | Previously matched rules
|  | `<label-or-var>` | string | Label or var from a preceding rule that matched

#### Intel RDT flags

Flag | Description
--- | ---
RDTMON | Intel RDT Monitoring Technology
RDTCMT | Intel Cache Monitoring (CMT)
RDTMBM | Intel Memory Bandwidth Monitoring (MBM)
RDTL3CA | Intel L3 Cache Allocation Technology
RDTl2CA | Intel L2 Cache Allocation Technology
RDTMBA | Intel Memory Bandwidth Allocation (MBA) Technology

### Templating

Rules support template-based creation of labels and vars with the `.labelsTemplate` and `.varsTemplate` fields. These makes it possible to dynamically generate labels and vars based on the features that matched.

The template must expand into a simple format with `<key>=<value>` pairs separated by newline.

Consider the following example:

        labelsTemplate: |
          {{ range .pci.device }}vendor-{{ .class }}-{{ .device }}.present=true
          {{ end }}
        matchFeatures:
          - feature: pci.device
            matchExpressions:
              class: {op: InRegexp, value: ["^02"]}
              vendor: ["0fff"]

The rule above will create individual labels `feature.node.kubernetes.io/vendor-<class-id>-<device-id>.present=true` for each network controller device (device class starting with 02) from vendor 0fff.

All the matched features of each feature matcher term under `matchFeatures` fields are available for the template engine. Matched features can be referenced with `{{ .<feature-name> }}` in the template, and the available data could be described in yaml as follows:

    .
      <key-feature>:
        - Name: <matched-key>
        - ...

      <value-feature>:
        - Name: <matched-key>
          Value: <matched-value>
        - ...

      <instance-feature>:
        - <attribute-1-name>: <attribute-1-value>
          <attribute-2-name>: <attribute-2-value>
          ...
        - ...

That is, the per-feature data is a list of objects whose data fields depend on the type of the feature:

- for flag features only ‘Name' is available
- for value features ‘Name' and ‘Value' are available
- for instance features all attributes of the matched instance are available

A simple example of a template utilizing name and value from an attribute feature:

        labelsTemplate: |
          {{ range .system.osrelease }}system-{{ .Name }}={{ .Value }}
          {{ end }}
        matchFeatures:
          - feature: system.osRelease
            matchExpressions:
              ID: {op: Exists}
              VERSION_ID.major: {op: Exists}

> NOTE:If both `matchExpressions` and `matchName` for a feature matcher term (see `matchFeatures`) is specified, the list of matched features (for the template engine) is the union from both of these. NOTE: In case of matchAny is specified, the template is executed separately against each individual `matchFeatures` field and the final set of labels will be superset of all these separate template expansions. E.g. consider the following:

      - name: <name>
        labelsTemplate: <template>
        matchFeatures: <matcher#1>
        matchAny:
          - matchFeatures: <matcher#2>
          - matchFeatures: <matcher#3>

In the example above (assuming the overall result is a match) the template would be executed on matcher#1 as well as on matcher#2 and/or matcher#3 (depending on whether both or only one of them match). All the labels from these separate expansions would be created, i.e. the end result would be a union of all the individual expansions.

Rule templates use the Golang text/template package and all its built-in functionality (e.g. pipelines and functions) can be used. An example template taking use of the built-in `len` function, advertising the number of PCI network controllers from a specific vendor:

        labelsTemplate: |
          num-intel-network-controllers={{ .pci.device | len }}
        matchFeatures:
          - feature: pci.device
            matchExpressions:
              vendor: {op: In, value: ["8086"]}
              class: {op: In, value: ["0200"]}

Imaginative template pipelines are possible, but care must be taken to produce understandable and maintainable rule sets.

### Backreferences

Rules support referencing the output of preceding rules. This enables sophisticated scenarios where multiple rules are combined together to for more complex heuristics than a single rule can provide. The labels and vars created by the execution of preceding rules are available as a special `rule.matched` feature.

Consider the following configuration:

      - name: "my kernel label rule"
        labels:
          kernel-feature: "true"
        matchFeatures:
          - feature: kernel.version
            matchExpressions:
              major: {op: Gt, value: ["4"]}

      - name: "my var rule"
        vars:
          nolabel-feature: "true"
        matchFeatures:
          - feature: cpu.cpuid
            matchExpressions:
              AVX512F: {op: Exists}
          - feature: pci.device
            matchExpressions:
              vendor: {op: In, value: ["0fff"]}
              device: {op: In, value: ["1234", "1235"]}

      - name: "my high level feature rule"
        labels:
          high-level-feature: "true"
        matchFeatures:
          - feature: rule.matched
            matchExpressions:
              kernel-feature: {op: IsTrue}
              nolabel-feature: {op: IsTrue}

The `feature.node.kubernetes.io/high-level-feature = true` label depends on the two previous rules.

Note that when referencing rules across multiple `NodeFeatureRule` objects attention must be paid to the ordering. `NodeFeatureRule` objects are processed in alphabetical order (based on their `.metadata.name`).

### Examples

Some more configuration examples below.

Match certain CPUID features:

      - name: "example cpuid rule"
        labels:
          my-special-cpu-feature: "true"
        matchFeatures:
          - feature: cpu.cpuid
            matchExpressions:
              AESNI: {op: Exists}
              AVX: {op: Exists}

Require a certain loaded kernel module and OS version:

      - name: "my multi-feature rule"
        labels:
          my-special-multi-feature: "true"
        matchFeatures:
          - feature: kernel.loadedmodule
            matchExpressions:
              e1000: {op: Exists}
          - feature: system.osrelease
            matchExpressions:
              NAME: {op: InRegexp, values: ["^openSUSE"]}
              VERSION_ID.major: {op: Gt, values: ["14"]}

Require a loaded kernel module and two specific PCI devices (both of which must be present):

      - name: "my multi-device rule"
        labels:
          my-multi-device-feature: "true"
        matchFeatures:
          - feature: kernel.loadedmodule
            matchExpressions:
              my-driver-module: {op: Exists}
          - pci.device:
              vendor: "0fff"
              device: "1234"
          - pci.device:
              vendor: "0fff"
              device: "abcd"

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This Software is under the terms of Apache License 2.0.