Make GenerateIfaceName generic

Currently GenerateIfaceName is defined in bridge.go
and it specifically tries to only generate an interface
name only with `veth` prefix. Make it generic so that it
can accept a prefix and length of random bytes. Also
move it to netutils since it is useful to generate various
kinds of interface names using it.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

libnetwork/drivers/bridge/bridge.go

@@ -5,7 +5,6 @@ import (
 	"net"
 	"os/exec"
 	"strconv"
-	"strings"
 	"sync"
 
 	"github.com/Sirupsen/logrus"
@@ -701,13 +700,13 @@ func (d *driver) CreateEndpoint(nid, eid types.UUID, epInfo driverapi.EndpointIn
 	}()
 
 	// Generate a name for what will be the host side pipe interface
-	name1, err := generateIfaceName()
+	name1, err := netutils.GenerateIfaceName(vethPrefix, vethLen)
 	if err != nil {
 		return err
 	}
 
 	// Generate a name for what will be the sandbox side pipe interface
-	name2, err := generateIfaceName()
+	name2, err := netutils.GenerateIfaceName(vethPrefix, vethLen)
 	if err != nil {
 		return err
 	}
@@ -1184,22 +1183,3 @@ func electMacAddress(epConfig *endpointConfiguration) net.HardwareAddr {
 	}
 	return netutils.GenerateRandomMAC()
 }
-
-// Generates a name to be used for a virtual ethernet
-// interface. The name is constructed by 'veth' appended
-// by a randomly generated hex value. (example: veth0f60e2c)
-func generateIfaceName() (string, error) {
-	for i := 0; i < 3; i++ {
-		name, err := netutils.GenerateRandomName(vethPrefix, vethLen)
-		if err != nil {
-			continue
-		}
-		if _, err := net.InterfaceByName(name); err != nil {
-			if strings.Contains(err.Error(), "no such") {
-				return name, nil
-			}
-			return "", err
-		}
-	}
-	return "", &ErrIfaceName{}
-}

libnetwork/netutils/utils.go

@@ -9,7 +9,9 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"strings"
 
+	"github.com/docker/libnetwork/types"
 	"github.com/vishvananda/netlink"
 )
 
@@ -147,3 +149,22 @@ func GenerateRandomName(prefix string, size int) (string, error) {
 	}
 	return prefix + hex.EncodeToString(id)[:size], nil
 }
+
+// GenerateIfaceName returns an interface name using the passed in
+// prefix and the length of random bytes. The api ensures that the
+// there are is no interface which exists with that name.
+func GenerateIfaceName(prefix string, len int) (string, error) {
+	for i := 0; i < 3; i++ {
+		name, err := GenerateRandomName(prefix, len)
+		if err != nil {
+			continue
+		}
+		if _, err := net.InterfaceByName(name); err != nil {
+			if strings.Contains(err.Error(), "no such") {
+				return name, nil
+			}
+			return "", err
+		}
+	}
+	return "", types.InternalErrorf("could not generate interface name")
+}

libnetwork/types/types_test.go

@@ -1,11 +1,12 @@
 package types
 
 import (
+	"flag"
 	"testing"
-
-	_ "github.com/docker/libnetwork/netutils"
 )
 
+var runningInContainer = flag.Bool("incontainer", false, "Indicates if the test is running in a container")
+
 func TestErrorConstructors(t *testing.T) {
 	var err error