pkg/wireguard: allow specifying iface named

This commit makes it possible to specify the Kilo interface name. If the
specified interface exists, it will be used; if it does not exist, Kilo
will create it. If the interface already existed, then it will not be
deleted on shutdown; otherwise Kilo will destroy the interface.

Fixes: https://github.com/squat/kilo/issues/8
Addresses: 1/2 of https://github.com/squat/kilo/issues/17

pkg/mesh/mesh.go

@@ -44,6 +44,8 @@ const (
 	PrivateKeyPath = KiloPath + "/key"
 	// ConfPath is the filepath where the WireGuard configuration is stored.
 	ConfPath = KiloPath + "/conf"
+	// DefaultKiloInterface is the default iterface created and used by Kilo.
+	DefaultKiloInterface = "kilo0"
 	// DefaultKiloPort is the default UDP port Kilo uses.
 	DefaultKiloPort = 51820
 	// DefaultCNIPath is the default path to the CNI config file.
@@ -169,6 +171,7 @@ type Mesh struct {
 	Backend
 	cni         bool
 	cniPath     string
+	deleteIface bool
 	enc         encapsulation.Encapsulator
 	externalIP  *net.IPNet
 	granularity Granularity
@@ -202,7 +205,7 @@ type Mesh struct {
 }
 
 // New returns a new Mesh instance.
-func New(backend Backend, enc encapsulation.Encapsulator, granularity Granularity, hostname string, port uint32, subnet *net.IPNet, local, cni bool, cniPath string, logger log.Logger) (*Mesh, error) {
+func New(backend Backend, enc encapsulation.Encapsulator, granularity Granularity, hostname string, port uint32, subnet *net.IPNet, local, cni bool, cniPath, iface string, logger log.Logger) (*Mesh, error) {
 	if err := os.MkdirAll(KiloPath, 0700); err != nil {
 		return nil, fmt.Errorf("failed to create directory to store configuration: %v", err)
 	}
@@ -239,7 +242,7 @@ func New(backend Backend, enc encapsulation.Encapsulator, granularity Granularit
 		return nil, fmt.Errorf("failed to find interface for public IP: %v", err)
 	}
 	pubIface := ifaces[0].Index
-	kiloIface, err := wireguard.New("kilo")
+	kiloIface, created, err := wireguard.New(iface)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create WireGuard interface: %v", err)
 	}
@@ -258,6 +261,7 @@ func New(backend Backend, enc encapsulation.Encapsulator, granularity Granularit
 		Backend:     backend,
 		cni:         cni,
 		cniPath:     cniPath,
+		deleteIface: created,
 		enc:         enc,
 		externalIP:  publicIP,
 		granularity: granularity,
@@ -713,9 +717,11 @@ func (m *Mesh) cleanUp() {
 		level.Error(m.logger).Log("error", fmt.Sprintf("failed to delete configuration file: %v", err))
 		m.errorCounter.WithLabelValues("cleanUp").Inc()
 	}
-	if err := iproute.RemoveInterface(m.kiloIface); err != nil {
-		level.Error(m.logger).Log("error", fmt.Sprintf("failed to remove WireGuard interface: %v", err))
-		m.errorCounter.WithLabelValues("cleanUp").Inc()
+	if m.deleteIface {
+		if err := iproute.RemoveInterface(m.kiloIface); err != nil {
+			level.Error(m.logger).Log("error", fmt.Sprintf("failed to remove WireGuard interface: %v", err))
+			m.errorCounter.WithLabelValues("cleanUp").Inc()
+		}
 	}
 	if err := m.Nodes().CleanUp(m.hostname); err != nil {
 		level.Error(m.logger).Log("error", fmt.Sprintf("failed to clean up node backend: %v", err))

pkg/wireguard/wireguard.go

@@ -18,8 +18,6 @@ import (
 	"bytes"
 	"fmt"
 	"os/exec"
-	"regexp"
-	"strconv"
 
 	"github.com/vishvananda/netlink"
 )
@@ -37,37 +35,28 @@ func (w wgLink) Type() string {
 	return w.t
 }
 
-// New creates a new WireGuard interface.
-func New(prefix string) (int, error) {
-	links, err := netlink.LinkList()
-	if err != nil {
-		return 0, fmt.Errorf("failed to list links: %v", err)
+// New returns a WireGuard interface with the given name.
+// If the interface exists, its index is returned.
+// Otherwise, a new interface is created.
+// The function also returns a boolean to indicate if the interface was created.
+func New(name string) (int, bool, error) {
+	link, err := netlink.LinkByName(name)
+	if err == nil {
+		return link.Attrs().Index, false, nil
 	}
-	max := 0
-	re := regexp.MustCompile(fmt.Sprintf("^%s([0-9]+)$", prefix))
-	for _, link := range links {
-		if matches := re.FindStringSubmatch(link.Attrs().Name); len(matches) == 2 {
-			i, err := strconv.Atoi(matches[1])
-			if err != nil {
-				// This should never happen.
-				return 0, fmt.Errorf("failed to parse digits as an integer: %v", err)
-			}
-			if i >= max {
-				max = i + 1
-			}
-		}
+	if _, ok := err.(netlink.LinkNotFoundError); !ok {
+		return 0, false, fmt.Errorf("failed to get links: %v", err)
 	}
-	name := fmt.Sprintf("%s%d", prefix, max)
 	wl := wgLink{a: netlink.NewLinkAttrs(), t: "wireguard"}
 	wl.a.Name = name
 	if err := netlink.LinkAdd(wl); err != nil {
-		return 0, fmt.Errorf("failed to create interface %s: %v", name, err)
+		return 0, false, fmt.Errorf("failed to create interface %s: %v", name, err)
 	}
-	link, err := netlink.LinkByName(name)
+	link, err = netlink.LinkByName(name)
 	if err != nil {
-		return 0, fmt.Errorf("failed to get interface index: %v", err)
+		return 0, false, fmt.Errorf("failed to get interface index: %v", err)
 	}
-	return link.Attrs().Index, nil
+	return link.Attrs().Index, true, nil
 }
 
 // Keys generates a WireGuard private and public key-pair.