source/network: run discovery under host sysfs

Instead of relying on golang "net" package, use the configured host
sysfs for all discovery. No need to use hostNetwork after that so drop
it from the worker deployment templates.

nfd-daemonset-combined.yaml.template

@@ -56,7 +56,6 @@ spec:
         app: nfd
     spec:
       serviceAccount: nfd-master
-      hostNetwork: true
       containers:
         - env:
           - name: NODE_NAME

nfd-worker-daemonset.yaml.template

@@ -14,7 +14,6 @@ spec:
       labels:
         app: nfd-worker
     spec:
-      hostNetwork: true
       dnsPolicy: ClusterFirstWithHostNet
       containers:
         - env:

nfd-worker-job.yaml.template

@@ -13,7 +13,6 @@ spec:
       labels:
         app: node-feature-discovery
     spec:
-      hostNetwork: true
       dnsPolicy: ClusterFirstWithHostNet
       affinity:
         podAntiAffinity:

source/network/network.go

@@ -21,13 +21,22 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
-	"net"
 	"strconv"
 	"strings"
 
 	"sigs.k8s.io/node-feature-discovery/source"
 )
 
+// Linux net iface flags (we only specify the first few)
+const (
+	flagUp = 1 << iota
+	_      // flagBroadcast
+	_      // flagDebug
+	flagLoopback
+)
+
+const sysfsBaseDir = "class/net"
+
 // Source implements FeatureSource.
 type Source struct{}
 
@@ -46,48 +55,70 @@ func (s *Source) SetConfig(source.Config) {}
 // Discover returns feature names sriov-configured and sriov if SR-IOV capable NICs are present and/or SR-IOV virtual functions are configured on the node
 func (s Source) Discover() (source.Features, error) {
 	features := source.Features{}
-	netInterfaces, err := net.Interfaces()
+
+	netInterfaces, err := ioutil.ReadDir(source.SysfsDir.Path(sysfsBaseDir))
 	if err != nil {
-		return nil, fmt.Errorf("can't obtain the network interfaces details: %s", err.Error())
+		return nil, fmt.Errorf("failed to list network interfaces: %s", err.Error())
 	}
+
 	// iterating through network interfaces to obtain their respective number of virtual functions
 	for _, netInterface := range netInterfaces {
-		if strings.Contains(netInterface.Flags.String(), "up") && !strings.Contains(netInterface.Flags.String(), "loopback") {
-			totalBytes, err := ioutil.ReadFile(source.SysfsDir.Path("class/net", netInterface.Name, "device/sriov_totalvfs"))
+		name := netInterface.Name()
+		flags, err := readIfFlags(name)
+		if err != nil {
+			log.Printf("%v", err)
+			continue
+		}
+
+		if flags&flagUp != 0 && flags&flagLoopback == 0 {
+			totalBytes, err := ioutil.ReadFile(source.SysfsDir.Path(sysfsBaseDir, name, "device/sriov_totalvfs"))
 			if err != nil {
-				log.Printf("SR-IOV not supported for network interface: %s: %v", netInterface.Name, err)
+				log.Printf("SR-IOV not supported for network interface: %s: %v", name, err)
 				continue
 			}
 			total := bytes.TrimSpace(totalBytes)
 			t, err := strconv.Atoi(string(total))
 			if err != nil {
-				log.Printf("Error in obtaining maximum supported number of virtual functions for network interface: %s: %v", netInterface.Name, err)
+				log.Printf("Error in obtaining maximum supported number of virtual functions for network interface: %s: %v", name, err)
 				continue
 			}
 			if t > 0 {
-				log.Printf("SR-IOV capability is detected on the network interface: %s", netInterface.Name)
-				log.Printf("%d maximum supported number of virtual functions on network interface: %s", t, netInterface.Name)
+				log.Printf("SR-IOV capability is detected on the network interface: %s", name)
+				log.Printf("%d maximum supported number of virtual functions on network interface: %s", t, name)
 				features["sriov.capable"] = true
-				numBytes, err := ioutil.ReadFile(source.SysfsDir.Path("class/net", netInterface.Name, "device/sriov_numvfs"))
+				numBytes, err := ioutil.ReadFile(source.SysfsDir.Path(sysfsBaseDir, name, "device/sriov_numvfs"))
 				if err != nil {
-					log.Printf("SR-IOV not configured for network interface: %s: %s", netInterface.Name, err)
+					log.Printf("SR-IOV not configured for network interface: %s: %s", name, err)
 					continue
 				}
 				num := bytes.TrimSpace(numBytes)
 				n, err := strconv.Atoi(string(num))
 				if err != nil {
-					log.Printf("Error in obtaining the configured number of virtual functions for network interface: %s: %v", netInterface.Name, err)
+					log.Printf("Error in obtaining the configured number of virtual functions for network interface: %s: %v", name, err)
 					continue
 				}
 				if n > 0 {
-					log.Printf("%d virtual functions configured on network interface: %s", n, netInterface.Name)
+					log.Printf("%d virtual functions configured on network interface: %s", n, name)
 					features["sriov.configured"] = true
 					break
 				} else if n == 0 {
-					log.Printf("SR-IOV not configured on network interface: %s", netInterface.Name)
+					log.Printf("SR-IOV not configured on network interface: %s", name)
 				}
 			}
 		}
 	}
 	return features, nil
 }
+
+func readIfFlags(name string) (uint64, error) {
+	raw, err := ioutil.ReadFile(source.SysfsDir.Path(sysfsBaseDir, name, "flags"))
+	if err != nil {
+		return 0, fmt.Errorf("failed to read flags for interface %q: %v", name, err)
+	}
+	flags, err := strconv.ParseUint(strings.TrimSpace(string(raw)), 0, 64)
+	if err != nil {
+		return 0, fmt.Errorf("failed to parse flags for interface %q: %v", name, err)
+	}
+
+	return flags, nil
+}