Add Match Rules package to be used in Custom Source

- Add a Rule interface to help describe the contract
  between a match rule and the Custom source that uses it.

- Add PciIdRule - a rule that matches on the PCI attributes:
  class, vendor, device. Each is provided as a list of elements(strings).
  Match operation: OR will be performed per element and AND will be
  performed per attribute.
  An empty attribute will not be included in the matching process.
  Example:
  {
    "class": ["0200"]
    "vendor": ["15b3"]
    "device": ["1014", "1016"]
  }

- Add LoadedKmodRule - a rule that matches a list of kernel
  modules with the kernel modules currently loaded in the node.
  Example:
  {
    ["rdma_cm", "ib_core"]
  }

source/custom/custom.go

@@ -17,11 +17,10 @@ limitations under the License.
 package custom
 
 import (
-	"encoding/json"
-
 	"sigs.k8s.io/node-feature-discovery/source"
 )
 
+// Custom Features Configurations
 type MatchRule struct {
 }
 

source/custom/rules/loaded_kmod_rule.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rules
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+)
+
+// Rule that matches on loaded kernel modules in the system
+type LoadedKModRule []string
+
+const kmodProcfsPath = "/proc/modules"
+
+func (kmods *LoadedKModRule) Match() (bool, error) {
+	loadedModules, err := kmods.getLoadedModules()
+	if err != nil {
+		return false, fmt.Errorf("failed to get loaded kernel modules. %s", err.Error())
+	}
+	for _, kmod := range *kmods {
+		if _, ok := loadedModules[kmod]; !ok {
+			// kernel module not loaded
+			return false, nil
+		}
+	}
+	return true, nil
+}
+
+func (kmods *LoadedKModRule) getLoadedModules() (map[string]struct{}, error) {
+	out, err := ioutil.ReadFile(kmodProcfsPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %s", kmodProcfsPath, err.Error())
+	}
+
+	loadedMods := make(map[string]struct{})
+	for _, line := range strings.Split(string(out), "\n") {
+		// skip empty lines
+		if len(line) == 0 {
+			continue
+		}
+		// append loaded module
+		loadedMods[strings.Fields(line)[0]] = struct{}{}
+	}
+	return loadedMods, nil
+}

source/custom/rules/pci_id_rule.go

@@ -0,0 +1,87 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rules
+
+import (
+	"fmt"
+	pciutils "sigs.k8s.io/node-feature-discovery/source/internal"
+)
+
+// Rule that matches on the following PCI device attributes: <class, vendor, device>
+// each device attribute will be a list elements(strings).
+// Match operation: OR will be performed per element and AND will be performed per attribute.
+// An empty attribute will not be included in the matching process.
+type PciIdRuleInput struct {
+	Class  []string `json:"class,omitempty"`
+	Vendor []string `json:"vendor,omitempty"`
+	Device []string `json:"device,omitempty"`
+}
+
+type PciIdRule struct {
+	PciIdRuleInput
+}
+
+// Match PCI devices on the provided list of PCI regular expressions
+func (r *PciIdRule) Match() (bool, error) {
+	devAttr := map[string]bool{}
+	for _, attr := range []string{"class", "vendor", "device"} {
+		devAttr[attr] = true
+	}
+	allDevs, err := pciutils.DetectPci(devAttr)
+	if err != nil {
+		return false, fmt.Errorf("failed to detect PCI devices: %s", err.Error())
+	}
+
+	for _, classDevs := range allDevs {
+		for _, dev := range classDevs {
+			// match rule on a single device
+			if r.matchDevOnRule(dev) {
+				return true, nil
+			}
+		}
+	}
+	return false, nil
+}
+
+func (r *PciIdRule) matchDevOnRule(dev pciutils.PciDeviceInfo) bool {
+	if len(r.Class) == 0 && len(r.Vendor) == 0 && len(r.Device) == 0 {
+		return false
+	}
+
+	if len(r.Class) > 0 && !in(dev["class"], r.Class) {
+		return false
+	}
+
+	if len(r.Vendor) > 0 && !in(dev["vendor"], r.Vendor) {
+		return false
+	}
+
+	if len(r.Device) > 0 && !in(dev["device"], r.Device) {
+		return false
+	}
+
+	return true
+}
+
+func in(item string, arr []string) bool {
+	for _, val := range arr {
+		if val == item {
+			return true
+		}
+	}
+	return false
+}

source/custom/rules/rule.go

@@ -0,0 +1,22 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package rules
+
+type Rule interface {
+	// Match on rule
+	Match() (bool, error)
+}