pkg/hostagent: Set LocalAddr to net.Dialer in DialContextToGuestIP()

Signed-off-by: Norio Nomura <[email protected]>

Author: norio-nomura

pkg/hostagent/hostagent.go

@@ -89,6 +89,9 @@ type HostAgent struct {
 	guestIPv4 net.IP
 	guestIPv6 net.IP
 	guestIPMu sync.RWMutex
+	// Host IP address on the same subnet as the guest.
+	hostIPv4 net.IP
+	hostIPv6 net.IP
 }
 
 type options struct {
@@ -542,6 +545,14 @@ func (a *HostAgent) GuestIPv6() net.IP {
 	return a.guestIPv6
 }
 
+// HostIPs returns the host's IP addresses on the same subnet as the guest.
+// It returns nil if the guest is not reachable by a direct IP.
+func (a *HostAgent) HostIPs() (ipv4, ipv6 net.IP) {
+	a.guestIPMu.RLock()
+	defer a.guestIPMu.RUnlock()
+	return a.hostIPv4, a.hostIPv6
+}
+
 func (a *HostAgent) Info(_ context.Context) (*hostagentapi.Info, error) {
 	guestIP := a.GuestIP()
 	info := &hostagentapi.Info{
@@ -800,7 +811,7 @@ 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 := DialContextToGuestIP(a.GuestIP())
+	dialContext := a.DialContextToGuestIP(a.GuestIP())
 	sshAddress, sshPort := a.sshAddressPort()
 	for _, rule := range staticPortForwards {
 		if rule.GuestSocket == "" {
@@ -932,15 +943,15 @@ func (a *HostAgent) processGuestAgentEvents(ctx context.Context, client *guestag
 				} else if ip := net.ParseIP(host); ip.IsUnspecified() || ip.Equal(guestIPv4) || ip.Equal(guestIPv6) {
 					if ip.To4() != nil {
 						if guestIPv4 != nil {
-							return DialContextToGuestIP(guestIPv4)(ctx, network, guestAddress)
+							return a.DialContextToGuestIP(guestIPv4)(ctx, network, guestAddress)
 						} else if guestIPv4 = a.GuestIPv6().To4(); guestIPv4 != nil {
-							return DialContextToGuestIP(guestIPv4)(ctx, network, guestAddress)
+							return a.DialContextToGuestIP(guestIPv4)(ctx, network, guestAddress)
 						}
 					} else if ip.To16() != nil {
 						if guestIPv6 != nil {
-							return DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
+							return a.DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
 						} else if guestIPv6 = a.GuestIPv4().To16(); guestIPv6 != nil {
-							return DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
+							return a.DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
 						}
 					}
 					// If we reach here, it means we couldn't find a suitable guest IP
@@ -962,12 +973,21 @@ func (a *HostAgent) processGuestAgentEvents(ctx context.Context, client *guestag
 
 // DialContextToGuestIP returns a DialContext function that connects to the guest IP directly.
 // If the guest IP is not known, it returns nil.
-func DialContextToGuestIP(guestIP net.IP) func(ctx context.Context, network, address string) (net.Conn, error) {
+func (a *HostAgent) DialContextToGuestIP(guestIP net.IP) func(ctx context.Context, network, address string) (net.Conn, error) {
 	if guestIP == nil {
 		return nil
 	}
+	var sourceIP net.IP
+	hostIPv4, hostIPv6 := a.HostIPs()
+	if hostIPv4 != nil && guestIP.To4() != nil {
+		sourceIP = hostIPv4
+	} else if hostIPv6 != nil && guestIP.To16() != nil {
+		sourceIP = hostIPv6
+	} else {
+		return nil
+	}
 	return func(ctx context.Context, network, address string) (net.Conn, error) {
-		var d net.Dialer
+		d := net.Dialer{LocalAddr: &net.TCPAddr{IP: sourceIP}}
 		_, port, err := net.SplitHostPort(address)
 		if err != nil {
 			return nil, err

pkg/hostagent/requirements.go

@@ -321,19 +321,36 @@ func (a *HostAgent) detectGuestIfnameOnSameSubnetAtHost(stdout string) error {
 	if err != nil {
 		return fmt.Errorf("failed to get network interfaces: %w", err)
 	}
+	var (
+		guestIfnameOnSameSubnetAsHost string
+		hostIPv4                      net.IP
+		hostIPv6                      net.IP
+	)
 	for _, neighbor := range neighbors {
 		for _, ifi := range interfaces {
 			if ifi.HardwareAddr.String() != neighbor.LLADDR {
 				continue
 			}
-			a.guestIPMu.Lock()
-			a.guestIfnameOnSameSubnetAsHost = neighbor.DEV
-			a.guestIPMu.Unlock()
-			logrus.Infof("Detected the guest has interface %q in same subnet on the host", neighbor.DEV)
-			return nil
+			guestIfnameOnSameSubnetAsHost = neighbor.DEV
+			if hostIP := net.ParseIP(neighbor.DST); hostIP.To4() != nil {
+				hostIPv4 = hostIP
+			} else if hostIP.To16() != nil {
+				hostIPv6 = hostIP
+			}
 		}
 	}
-	logrus.Info("The guest does not have interface in same subnet on the host")
+	a.guestIPMu.Lock()
+	a.guestIfnameOnSameSubnetAsHost = guestIfnameOnSameSubnetAsHost
+	a.hostIPv4 = hostIPv4
+	a.hostIPv6 = hostIPv6
+	a.guestIPMu.Unlock()
+	logrus.Infof("Detected the guest has interface %q in same subnet on the host", guestIfnameOnSameSubnetAsHost)
+	if hostIPv4 != nil {
+		logrus.Infof("The host IPv4 address on the same subnet as the guest is %q", hostIPv4)
+	}
+	if hostIPv6 != nil {
+		logrus.Infof("The host IPv6 address on the same subnet as the guest is %q", hostIPv6)
+	}
 	return nil
 }