fixing VPN server problem with multiple network interface

cmd/apps/vpn-server/vpn-server.go

@@ -30,6 +30,7 @@ var (
 	localPKStr = flag.String("pk", "", "Local PubKey")
 	localSKStr = flag.String("sk", "", "Local SecKey")
 	passcode   = flag.String("passcode", "", "Passcode to authenticate connecting users")
+	networkIfc = flag.String("netifc", "", "Default network interface for multiple available interfaces")
 	secure     = flag.Bool("secure", true, "Forbid connections from clients to server local network")
 )
 
@@ -73,8 +74,9 @@ func main() {
 	log.Infof("Got app listener, bound to %d", vpnPort)
 
 	srvCfg := vpn.ServerConfig{
-		Passcode: *passcode,
-		Secure:   *secure,
+		Passcode:        *passcode,
+		Secure:          *secure,
+		NetworkInteface: *networkIfc,
 	}
 	srv, err := vpn.NewServer(srvCfg, log)
 	if err != nil {

cmd/skywire-cli/commands/config/update/root.go

@@ -30,6 +30,7 @@ var (
 	addVPNServerPasscode   string
 	setVPNServerSecure     string
 	setVPNServerAutostart  string
+	setVPNServerNetIfc     string
 	resetVPNServer         bool
 	addSkysocksClientSrv   string
 	resetSkysocksClient    bool

cmd/skywire-cli/commands/config/update/update.go

@@ -43,6 +43,7 @@ func init() {
 	vpnServerUpdateCmd.Flags().StringVarP(&addVPNServerPasscode, "passwd", "s", "", "add passcode to vpn-server")
 	vpnServerUpdateCmd.Flags().StringVar(&setVPNServerSecure, "secure", "", "change secure mode status of vpn-server")
 	vpnServerUpdateCmd.Flags().StringVar(&setVPNServerAutostart, "autostart", "", "change autostart of vpn-server")
+	vpnServerUpdateCmd.Flags().StringVar(&setVPNServerNetIfc, "netifc", "", "set default network interface")
 	vpnServerUpdateCmd.Flags().BoolVarP(&resetVPNServer, "reset", "r", false, "reset vpn-server configurations")
 }
 
@@ -200,6 +201,9 @@ var vpnServerUpdateCmd = &cobra.Command{
 		if addVPNServerPasscode != "" {
 			changeAppsConfig(conf, "vpn-server", "--passcode", addVPNServerPasscode)
 		}
+		if setVPNServerNetIfc != "" {
+			changeAppsConfig(conf, "vpn-server", "-netifc", setVPNServerNetIfc)
+		}
 		switch setVPNServerSecure {
 		case "true":
 			changeAppsConfig(conf, "vpn-server", "--secure", setVPNServerSecure)

internal/vpn/server.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"strings"
 	"sync"
 
 	"github.com/sirupsen/logrus"
@@ -29,15 +30,25 @@ type Server struct {
 
 // NewServer creates VPN server instance.
 func NewServer(cfg ServerConfig, l logrus.FieldLogger) (*Server, error) {
+	var defaultNetworkIfc string
 	s := &Server{
 		cfg:   cfg,
 		log:   l,
 		ipGen: NewIPGenerator(),
 	}
 
-	defaultNetworkIfc, err := netutil.DefaultNetworkInterface()
-	if err != nil {
-		return nil, fmt.Errorf("error getting default network interface: %w", err)
+	if cfg.NetworkInteface == "" {
+		defaultNetworkIfcs, err := netutil.DefaultNetworkInterface()
+		if err != nil {
+			return nil, fmt.Errorf("error getting default network interface: %w", err)
+		}
+		netIfcs, isMultiple := s.checkingNetworkInterface(defaultNetworkIfcs)
+		if isMultiple {
+			return nil, fmt.Errorf("multiple default network interface detected, please set once in setting or be single: %v", netIfcs)
+		}
+		defaultNetworkIfc = defaultNetworkIfcs
+	} else {
+		defaultNetworkIfc = cfg.NetworkInteface
 	}
 
 	l.Infof("Got default network interface: %s", defaultNetworkIfc)
@@ -316,3 +327,11 @@ func (s *Server) sendServerErrHello(conn net.Conn, status HandshakeStatus) {
 		s.log.WithError(err).Errorln("Error sending server hello")
 	}
 }
+
+func (s *Server) checkingNetworkInterface(defaultNetworkInterface string) ([]string, bool) {
+	networkInterfaces := strings.Split(defaultNetworkInterface, "\n")
+	if len(networkInterfaces) > 1 {
+		return networkInterfaces, true
+	}
+	return []string{}, false
+}

internal/vpn/server_config.go

@@ -2,6 +2,7 @@ package vpn
 
 // ServerConfig is a configuration for VPN server.
 type ServerConfig struct {
-	Passcode string
-	Secure   bool
+	Passcode        string
+	Secure          bool
+	NetworkInteface string
 }

pkg/visor/api.go

@@ -47,6 +47,7 @@ type API interface {
 	SetAppPK(appName string, pk cipher.PubKey) error
 	SetAppSecure(appName string, isSecure bool) error
 	SetAppKillswitch(appName string, killswitch bool) error
+	SetAppNetworkInterface(appName string, netifc string) error
 	LogsSince(timestamp time.Time, appName string) ([]string, error)
 	GetAppStats(appName string) (appserver.AppStats, error)
 	GetAppError(appName string) (string, error)
@@ -411,6 +412,27 @@ func (v *Visor) SetAppPassword(appName, password string) error {
 	return nil
 }
 
+// SetAppNetworkInterface implements API.
+func (v *Visor) SetAppNetworkInterface(appName, netifc string) error {
+	if skyenv.VPNServerName != appName {
+		return fmt.Errorf("app %s is not allowed to set network interface", appName)
+	}
+
+	v.log.Infof("Changing %s network interface to %q", appName, netifc)
+
+	const (
+		netifcArgName = "-netifc"
+	)
+
+	if err := v.conf.UpdateAppArg(v.appL, appName, netifcArgName, netifc); err != nil {
+		return err
+	}
+
+	v.log.Infof("Updated %v network interface", appName)
+
+	return nil
+}
+
 // SetAppKillswitch implements API.
 func (v *Visor) SetAppKillswitch(appName string, killswitch bool) error {
 	if appName != skyenv.VPNClientName {

pkg/visor/hypervisor.go

@@ -604,13 +604,14 @@ func (hv *Hypervisor) putApp() http.HandlerFunc {
 			Secure     *bool          `json:"secure,omitempty"`
 			Status     *int           `json:"status,omitempty"`
 			Passcode   *string        `json:"passcode,omitempty"`
+			NetIfc     *string        `json:"netifc,omitempty"`
 			PK         *cipher.PubKey `json:"pk,omitempty"`
 		}
 
 		shouldRestartApp := func(r req) bool {
 			// we restart the app if one of these fields was changed
 			return r.Killswitch != nil || r.Secure != nil || r.Passcode != nil ||
-				r.PK != nil
+				r.PK != nil || r.NetIfc != nil
 		}
 
 		var reqBody req
@@ -661,6 +662,13 @@ func (hv *Hypervisor) putApp() http.HandlerFunc {
 			}
 		}
 
+		if reqBody.NetIfc != nil {
+			if err := ctx.API.SetAppNetworkInterface(ctx.App.Name, *reqBody.NetIfc); err != nil {
+				httputil.WriteJSON(w, r, http.StatusInternalServerError, err)
+				return
+			}
+		}
+
 		if shouldRestartApp(reqBody) {
 			if err := ctx.API.RestartApp(ctx.App.Name); err != nil {
 				httputil.WriteJSON(w, r, http.StatusInternalServerError, err)

pkg/visor/rpc.go

@@ -253,6 +253,19 @@ func (r *RPC) SetAppPassword(in *SetAppPasswordIn, _ *struct{}) (err error) {
 	return r.visor.SetAppPassword(in.AppName, in.Password)
 }
 
+// SetAppNetworkInterfaceIn is input for SetAppNetworkInterface.
+type SetAppNetworkInterfaceIn struct {
+	AppName string
+	NetIfc  string
+}
+
+// SetAppNetworkInterface sets network interface for the app.
+func (r *RPC) SetAppNetworkInterface(in *SetAppNetworkInterfaceIn, _ *struct{}) (err error) {
+	defer rpcutil.LogCall(r.log, "SetAppNetworkInterface", in)(nil, &err)
+
+	return r.visor.SetAppNetworkInterface(in.AppName, in.NetIfc)
+}
+
 // SetAppPKIn is input for SetAppPK.
 type SetAppPKIn struct {
 	AppName string

pkg/visor/rpc_client.go

@@ -190,6 +190,14 @@ func (rc *rpcClient) SetAppKillswitch(appName string, killswitch bool) error {
 	}, &struct{}{})
 }
 
+// SetAppKillswitch implements API.
+func (rc *rpcClient) SetAppNetworkInterface(appName, netifc string) error {
+	return rc.Call("SetAppNetworkInterface", &SetAppNetworkInterfaceIn{
+		AppName: appName,
+		NetIfc:  netifc,
+	}, &struct{}{})
+}
+
 // SetAppSecure implements API.
 func (rc *rpcClient) SetAppSecure(appName string, isSecure bool) error {
 	return rc.Call("SetAppSecure", &SetAppBoolIn{
@@ -743,6 +751,21 @@ func (mc *mockRPCClient) SetAppPassword(string, string) error {
 	})
 }
 
+// SetAppPassword implements API.
+func (mc *mockRPCClient) SetAppNetworkInterface(string, string) error {
+	return mc.do(true, func() error {
+		const vpnServerName = "vpn-server"
+
+		for i := range mc.o.Apps {
+			if mc.o.Apps[i].Name == vpnServerName {
+				return nil
+			}
+		}
+
+		return fmt.Errorf("app of name '%s' does not exist", vpnServerName)
+	})
+}
+
 // SetAppPK implements API.
 func (mc *mockRPCClient) SetAppPK(string, cipher.PubKey) error {
 	return mc.do(true, func() error {