pkg/hostagent: Support static port forwarding to direct guest IP

Since port forwarding to the guest IP directly does not require guest agent,
we can support static port forwarding if `DialContextToGuestIP()` returns non-nil.

pkg/portfwd:
- Add `Forwarder.Forward()`

pkg/hostagent:
- Use `a.grpcPortForwarder.Forward()` if `DialContextToGuestIP()` returns non-nil.

Signed-off-by: Norio Nomura <norio.nomura@gmail.com>

Author: norio-nomura

pkg/hostagent/hostagent.go

@@ -772,6 +772,9 @@ func (a *HostAgent) watchGuestAgentEvents(ctx context.Context) {
 }
 
 func (a *HostAgent) addStaticPortForwardsFromList(ctx context.Context, staticPortForwards []limatype.PortForward) {
+	// Since port forwarding to the guest IP directly does not require guest agent,
+	// we can support static port forwarding if DialContextToGuestIP() returns non-nil.
+	dialContext := a.DialContextToGuestIP()
 	sshAddress, sshPort := a.sshAddressPort()
 	for _, rule := range staticPortForwards {
 		if rule.GuestSocket == "" {
@@ -783,8 +786,21 @@ func (a *HostAgent) addStaticPortForwardsFromList(ctx context.Context, staticPor
 			local, remote := a.portForwarder.forwardingAddresses(guest)
 			if local != "" {
 				logrus.Infof("Setting up static TCP forwarding from %s to %s", remote, local)
-				if err := forwardTCP(ctx, a.sshConfig, sshAddress, sshPort, local, remote, verbForward); err != nil {
-					logrus.WithError(err).Warnf("failed to set up static TCP forwarding %s -> %s", remote, local)
+				if dialContext != nil {
+					switch rule.Proto {
+					case "tcp":
+						a.grpcPortForwarder.Forward(ctx, dialContext, rule.Proto, local, remote)
+					case "udp":
+						a.grpcPortForwarder.Forward(ctx, dialContext, rule.Proto, local, remote)
+					case "any":
+						a.grpcPortForwarder.Forward(ctx, dialContext, "tcp", local, remote)
+						a.grpcPortForwarder.Forward(ctx, dialContext, "udp", local, remote)
+					}
+				} else {
+					// fallback to SSH-based port forwarding
+					if err := forwardTCP(ctx, a.sshConfig, sshAddress, sshPort, local, remote, verbForward); err != nil {
+						logrus.WithError(err).Warnf("failed to set up static TCP forwarding %s -> %s", remote, local)
+					}
 				}
 			}
 		}

pkg/portfwd/forward.go

@@ -53,8 +53,7 @@ func (fw *Forwarder) OnEvent(ctx context.Context, dialContext func(ctx context.C
 			}
 			continue
 		}
-		logrus.Infof("Forwarding %s from %s to %s", strings.ToUpper(f.Protocol), remote, local)
-		fw.closableListeners.Forward(ctx, dialContext, f.Protocol, local, remote)
+		fw.Forward(ctx, dialContext, f.Protocol, local, remote)
 	}
 	for _, f := range ev.RemovedLocalPorts {
 		local, remote := fw.forwardingAddresses(f)
@@ -66,6 +65,11 @@ func (fw *Forwarder) OnEvent(ctx context.Context, dialContext func(ctx context.C
 	}
 }
 
+func (fw *Forwarder) Forward(ctx context.Context, dialContext func(ctx context.Context, network string, addr string) (net.Conn, error), protocol, local, remote string) {
+	logrus.Infof("Forwarding %s from %s to %s", strings.ToUpper(protocol), remote, local)
+	fw.closableListeners.Forward(ctx, dialContext, protocol, local, remote)
+}
+
 func (fw *Forwarder) forwardingAddresses(guest *api.IPPort) (hostAddr, guestAddr string) {
 	guestIP := net.ParseIP(guest.Ip)
 	for _, rule := range fw.rules {