virtual-net: initial (#4751)

pkg/config/v1/visitor_plugin.go

@@ -0,0 +1,86 @@
+// Copyright 2025 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package v1
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"reflect"
+)
+
+const (
+	VisitorPluginVirtualNet = "virtual_net"
+)
+
+var visitorPluginOptionsTypeMap = map[string]reflect.Type{
+	VisitorPluginVirtualNet: reflect.TypeOf(VirtualNetVisitorPluginOptions{}),
+}
+
+type VisitorPluginOptions interface {
+	Complete()
+}
+
+type TypedVisitorPluginOptions struct {
+	Type string `json:"type"`
+	VisitorPluginOptions
+}
+
+func (c *TypedVisitorPluginOptions) UnmarshalJSON(b []byte) error {
+	if len(b) == 4 && string(b) == "null" {
+		return nil
+	}
+
+	typeStruct := struct {
+		Type string `json:"type"`
+	}{}
+	if err := json.Unmarshal(b, &typeStruct); err != nil {
+		return err
+	}
+
+	c.Type = typeStruct.Type
+	if c.Type == "" {
+		return errors.New("visitor plugin type is empty")
+	}
+
+	v, ok := visitorPluginOptionsTypeMap[typeStruct.Type]
+	if !ok {
+		return fmt.Errorf("unknown visitor plugin type: %s", typeStruct.Type)
+	}
+	options := reflect.New(v).Interface().(VisitorPluginOptions)
+
+	decoder := json.NewDecoder(bytes.NewBuffer(b))
+	if DisallowUnknownFields {
+		decoder.DisallowUnknownFields()
+	}
+
+	if err := decoder.Decode(options); err != nil {
+		return fmt.Errorf("unmarshal VisitorPluginOptions error: %v", err)
+	}
+	c.VisitorPluginOptions = options
+	return nil
+}
+
+func (c *TypedVisitorPluginOptions) MarshalJSON() ([]byte, error) {
+	return json.Marshal(c.VisitorPluginOptions)
+}
+
+type VirtualNetVisitorPluginOptions struct {
+	Type          string `json:"type"`
+	DestinationIP string `json:"destinationIP"`
+}
+
+func (o *VirtualNetVisitorPluginOptions) Complete() {}