pkg/hostagent: Aware forwarding guest address is IPv4 or IPv6

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

Author: norio-nomura

pkg/hostagent/hostagent.go

@@ -922,10 +922,28 @@ func (a *HostAgent) processGuestAgentEvents(ctx context.Context, client *guestag
 				if guestIP == nil {
 					return portfwd.DialContextToGRPCTunnel(client)(ctx, network, guestAddress)
 				}
+				guestIPv4 := a.GuestIPv4()
+				guestIPv6 := a.GuestIPv6()
+				// Check if the host part of guestAddress is either unspecified address or matches the known guest IP.
+				// If so, replace it with the known guest IP to avoid issues with dual-stack setups and DNS resolution.
+				// Otherwise, fall back to the gRPC tunnel.
 				if host, _, err := net.SplitHostPort(guestAddress); err != nil {
 					return nil, err
-				} else if ip := net.ParseIP(host); ip.IsUnspecified() || ip.Equal(guestIP) {
-					return DialContextToGuestIP(guestIP)(ctx, network, guestAddress)
+				} 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)
+						} else if guestIPv4 = a.GuestIPv6().To4(); guestIPv4 != nil {
+							return DialContextToGuestIP(guestIPv4)(ctx, network, guestAddress)
+						}
+					} else if ip.To16() != nil {
+						if guestIPv6 != nil {
+							return DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
+						} else if guestIPv6 = a.GuestIPv4().To16(); guestIPv6 != nil {
+							return DialContextToGuestIP(guestIPv6)(ctx, network, guestAddress)
+						}
+					}
+					// If we reach here, it means we couldn't find a suitable guest IP
 				}
 				return portfwd.DialContextToGRPCTunnel(client)(ctx, network, guestAddress)
 			}