fingerprint: add fingerprinting for CNI plugins presense and version

This PR adds a fingerprinter to set the attributes
 "cni.plugins" -> "true" or "false" if <cni_path> contains CNI plugins
 "cni.plugins.version" -> version of the CNI plugins if present

client/fingerprint/cni.go

@@ -6,16 +6,18 @@ import (
 	"strings"
 
 	"github.com/containernetworking/cni/libcni"
-	log "github.com/hashicorp/go-hclog"
+	"github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/nomad/nomad/structs"
 )
 
+// CNIFingerprint creates a fingerprint of the CNI configuration(s) on the
+// Nomad client.
 type CNIFingerprint struct {
 	StaticFingerprinter
-	logger log.Logger
+	logger hclog.Logger
 }
 
-func NewCNIFingerprint(logger log.Logger) Fingerprint {
+func NewCNIFingerprint(logger hclog.Logger) Fingerprint {
 	return &CNIFingerprint{logger: logger}
 }
 

client/fingerprint/cni_plugins.go

@@ -0,0 +1,70 @@
+package fingerprint
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/hashicorp/go-hclog"
+)
+
+const (
+	defaultCNIPath = "/opt/cni/bin"
+)
+
+// CNIPluginsFingerprint creates a fingerprint of the CNI plugins present on the
+// CNI plugin path specified for the Nomad client.
+type CNIPluginsFingerprint struct {
+	StaticFingerprinter
+	logger hclog.Logger
+	lister func(string) ([]os.DirEntry, error)
+}
+
+func NewCNIPluginsFingerprint(logger hclog.Logger) Fingerprint {
+	return &CNIPluginsFingerprint{
+		logger: logger.Named("cni_plugins"),
+		lister: os.ReadDir,
+	}
+}
+
+func (f *CNIPluginsFingerprint) Fingerprint(req *FingerprintRequest, resp *FingerprintResponse) error {
+	cniPath := req.Config.CNIPath
+	if cniPath == "" {
+		cniPath = defaultCNIPath
+	}
+
+	entries, err := f.lister(cniPath)
+	switch {
+	case err != nil:
+		f.logger.Debug("failed to read CNI plugins directory", "cni_path", cniPath, "error", err)
+		resp.Detected = true
+		resp.AddAttribute("cni.plugins", "false")
+		return nil
+	case len(entries) == 0:
+		f.logger.Debug("no CNI plugins found", "cni_path", cniPath)
+		resp.Detected = true
+		resp.AddAttribute("cni.plugins", "false")
+		return nil
+	}
+
+	bridgePath := filepath.Join(cniPath, "bridge")
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	cmd := exec.CommandContext(ctx, bridgePath, "--version")
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		f.logger.Debug("failed to detect CNI plugins version", "error", err)
+		resp.AddAttribute("cni.plugins", "false")
+		return nil
+	}
+	tokens := strings.Fields(string(output))
+	version := tokens[len(tokens)-1]
+	f.logger.Debug("detected CNI plugins", "version", version)
+	resp.AddAttribute("cni.plugins", "true")
+	resp.AddAttribute("cni.plugins.version", version)
+	resp.Detected = true
+	return nil
+}

client/fingerprint/cni_plugins_test.go

@@ -0,0 +1,64 @@
+package fingerprint
+
+import (
+	"os"
+	"testing"
+
+	"github.com/hashicorp/nomad/ci"
+	"github.com/hashicorp/nomad/client/config"
+	"github.com/hashicorp/nomad/helper/testlog"
+	"github.com/shoenig/test/must"
+)
+
+func TestCNIPluginsFingerprint_Fingerprint_default(t *testing.T) {
+	ci.Parallel(t)
+
+	f := NewCNIPluginsFingerprint(testlog.HCLogger(t))
+	request := &FingerprintRequest{
+		Config: new(config.Config),
+	}
+	response := new(FingerprintResponse)
+
+	err := f.Fingerprint(request, response)
+	must.NoError(t, err)
+	must.True(t, response.Detected)
+	must.Eq(t, "true", response.Attributes["cni.plugins"])
+	must.StrHasPrefix(t, "v1", response.Attributes["cni.plugins.version"])
+}
+
+func TestCNIPluginsFingerprint_Fingerprint_absent(t *testing.T) {
+	ci.Parallel(t)
+
+	f := NewCNIPluginsFingerprint(testlog.HCLogger(t))
+	request := &FingerprintRequest{
+		Config: &config.Config{
+			CNIPath: "/does/not/exist",
+		},
+	}
+	response := new(FingerprintResponse)
+
+	err := f.Fingerprint(request, response)
+	must.False(t, response.Detected)
+	must.NoError(t, err)
+	must.Eq(t, "false", response.Attributes["cni.plugins"])
+}
+
+func TestCNIPluginsFingerprint_Fingerprint_empty(t *testing.T) {
+	ci.Parallel(t)
+
+	lister := func(string) ([]os.DirEntry, error) {
+		return nil, nil
+	}
+
+	f := NewCNIPluginsFingerprint(testlog.HCLogger(t))
+	f.(*CNIPluginsFingerprint).lister = lister
+	request := &FingerprintRequest{
+		Config: new(config.Config),
+	}
+	response := new(FingerprintResponse)
+
+	err := f.Fingerprint(request, response)
+	must.NoError(t, err)
+	must.True(t, response.Detected)
+	must.Eq(t, "false", response.Attributes["cni.plugins"])
+}

client/fingerprint/fingerprint.go

@@ -29,17 +29,18 @@ var (
 	// hostFingerprinters contains the host fingerprints which are available for a
 	// given platform.
 	hostFingerprinters = map[string]Factory{
-		"arch":    NewArchFingerprint,
-		"consul":  NewConsulFingerprint,
-		"cni":     NewCNIFingerprint,
-		"cpu":     NewCPUFingerprint,
-		"host":    NewHostFingerprint,
-		"memory":  NewMemoryFingerprint,
-		"network": NewNetworkFingerprint,
-		"nomad":   NewNomadFingerprint,
-		"signal":  NewSignalFingerprint,
-		"storage": NewStorageFingerprint,
-		"vault":   NewVaultFingerprint,
+		"arch":        NewArchFingerprint,
+		"consul":      NewConsulFingerprint,
+		"cni":         NewCNIFingerprint,
+		"cni_plugins": NewCNIPluginsFingerprint,
+		"cpu":         NewCPUFingerprint,
+		"host":        NewHostFingerprint,
+		"memory":      NewMemoryFingerprint,
+		"network":     NewNetworkFingerprint,
+		"nomad":       NewNomadFingerprint,
+		"signal":      NewSignalFingerprint,
+		"storage":     NewStorageFingerprint,
+		"vault":       NewVaultFingerprint,
 	}
 
 	// envFingerprinters contains the fingerprints that are environment specific.