Add route support

route.go

@@ -0,0 +1,89 @@
+package tun
+
+import (
+	"net/netip"
+
+	E "github.com/sagernet/sing/common/exceptions"
+)
+
+type ActionType = uint8
+
+const (
+	ActionTypeReturn ActionType = iota
+	ActionTypeReject
+	ActionTypeDirect
+)
+
+func ParseActionType(action string) (ActionType, error) {
+	switch action {
+	case "return":
+		return ActionTypeReturn, nil
+	case "reject":
+		return ActionTypeReject, nil
+	case "direct":
+		return ActionTypeDirect, nil
+	default:
+		return 0, E.New("unknown action: ", action)
+	}
+}
+
+func ActionTypeName(actionType ActionType) string {
+	switch actionType {
+	case ActionTypeReturn:
+		return "return"
+	case ActionTypeReject:
+		return "reject"
+	case ActionTypeDirect:
+		return "direct"
+	default:
+		return "unknown"
+	}
+}
+
+type RouteSession struct {
+	IPVersion   uint8
+	Network     uint8
+	Source      netip.AddrPort
+	Destination netip.AddrPort
+}
+
+type RouteContext interface {
+	WritePacket(packet []byte) error
+}
+
+type Router interface {
+	RouteConnection(session RouteSession, context RouteContext) RouteAction
+}
+
+type RouteAction interface {
+	ActionType() ActionType
+	Timeout() bool
+}
+
+type ActionReturn struct{}
+
+func (r *ActionReturn) ActionType() ActionType {
+	return ActionTypeReturn
+}
+
+func (r *ActionReturn) Timeout() bool {
+	return false
+}
+
+type ActionReject struct{}
+
+func (r *ActionReject) ActionType() ActionType {
+	return ActionTypeReject
+}
+
+func (r *ActionReject) Timeout() bool {
+	return false
+}
+
+type ActionDirect struct {
+	DirectDestination
+}
+
+func (r *ActionDirect) ActionType() ActionType {
+	return ActionTypeDirect
+}