Apply sockopt from inbound config to dokodemo tproxy's response connection

proxy/dokodemo/dokodemo.go

@@ -27,7 +27,7 @@ func init() {
 	common.Must(common.RegisterConfig((*Config)(nil), func(ctx context.Context, config interface{}) (interface{}, error) {
 		d := new(DokodemoDoor)
 		err := core.RequireFeatures(ctx, func(pm policy.Manager) error {
-			return d.Init(config.(*Config), pm)
+			return d.Init(config.(*Config), pm, session.SockoptFromContext(ctx))
 		})
 		return d, err
 	}))
@@ -38,10 +38,11 @@ type DokodemoDoor struct {
 	config        *Config
 	address       net.Address
 	port          net.Port
+	sockopt       *session.Sockopt
 }
 
 // Init initializes the DokodemoDoor instance with necessary parameters.
-func (d *DokodemoDoor) Init(config *Config, pm policy.Manager) error {
+func (d *DokodemoDoor) Init(config *Config, pm policy.Manager, sockopt *session.Sockopt) error {
 	if (config.NetworkList == nil || len(config.NetworkList.Network) == 0) && len(config.Networks) == 0 {
 		return newError("no network specified")
 	}
@@ -49,6 +50,7 @@ func (d *DokodemoDoor) Init(config *Config, pm policy.Manager) error {
 	d.address = config.GetPredefinedAddress()
 	d.port = net.Port(config.Port)
 	d.policyManager = pm
+	d.sockopt = sockopt
 
 	return nil
 }
@@ -165,6 +167,9 @@ func (d *DokodemoDoor) Process(ctx context.Context, network net.Network, conn in
 				sockopt.BindAddress = dest.Address.IP()
 				sockopt.BindPort = uint32(dest.Port)
 			}
+			if d.sockopt != nil {
+				sockopt.Mark = d.sockopt.Mark
+			}
 			tConn, err := internet.DialSystem(ctx, net.DestinationFromAddr(conn.RemoteAddr()), sockopt)
 			if err != nil {
 				return err