cni: fix plugin fingerprinting versions (#16776)

CNI plugins v1.2.0 and above output a second line, containing supported protocol versions.

.changelog/16776.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+client: Fix CNI plugin version fingerprint when output includes protocol version
+```

client/fingerprint/plugins_cni.go

@@ -101,9 +101,9 @@ func (f *PluginsCNIFingerprint) detectOne(cniPath string, entry os.DirEntry) (st
 	// e.g.
 	//  /opt/cni/bin/bridge <no args>
 	//  CNI bridge plugin v1.0.0
+	//  (and optionally another line that contains the supported CNI protocol versions)
 	tokens := strings.Fields(string(output))
-	for i := len(tokens) - 1; i >= 0; i-- {
-		token := tokens[i]
+	for _, token := range tokens {
 		if _, parseErr := version.NewSemver(token); parseErr == nil {
 			return token, true
 		}

client/fingerprint/plugins_cni_test.go

@@ -26,8 +26,10 @@ func TestPluginsCNIFingerprint_Fingerprint_present(t *testing.T) {
 	must.True(t, response.Detected)
 	attrCustom := f.(*PluginsCNIFingerprint).attribute("custom")
 	attrBridge := f.(*PluginsCNIFingerprint).attribute("bridge")
+	attrVlan := f.(*PluginsCNIFingerprint).attribute("vlan")
 	must.Eq(t, "v1.2.3", response.Attributes[attrCustom])
 	must.Eq(t, "v1.0.2", response.Attributes[attrBridge])
+	must.Eq(t, "v1.2.0", response.Attributes[attrVlan])
 }
 
 func TestPluginsCNIFingerprint_Fingerprint_absent(t *testing.T) {

client/fingerprint/test_fixtures/cni/bridge

@@ -1,3 +1,4 @@
 #!/bin/sh
 
+# This fixture uses the old version output, without the supported CNI protocol versions.
 echo "CNI bridge plugin v1.0.2"

client/fingerprint/test_fixtures/cni/vlan

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+# This fixture uses the new version output, including the supported CNI protocol versions.
+echo "CNI vlan plugin v1.2.0"
+echo "CNI protocol versions supported: 0.1.0, 0.2.0, 0.3.0, 0.3.1, 0.4.0, 1.0.0"