搭建tailscale自建derp

package main

import (
	"encoding/json"
	"log"
	"net/http"
	"os"
)

type DERPAdmitClientRequest struct {
	NodePublic string
	Source     string
}

type DERPAdmitClientResponse struct {
	Allow bool
}

var allowedNodes []string

func loadNodes(filename string) error {
	data, err := os.ReadFile(filename)
	if err != nil {
		return err
	}

	var nodeKeys []string
	if err := json.Unmarshal(data, &nodeKeys); err != nil {
		return err
	}

	for _, nodeStr := range nodeKeys {
		allowedNodes = append(allowedNodes, nodeStr)
	}

	return nil
}

func handleAdmitRequest(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		w.WriteHeader(http.StatusMethodNotAllowed)
		return
	}

	var req DERPAdmitClientRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	allowed := false
	for _, node := range allowedNodes {
		if node == req.NodePublic {
			allowed = true
			break
		}
	}

	resp := DERPAdmitClientResponse{Allow: allowed}
	if err := json.NewEncoder(w).Encode(resp); err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		return
	}

	if allowed {
		log.Printf("Node admitted: %x", req.NodePublic)
	}
}

func main() {
	if err := loadNodes("nodes.json"); err != nil {
		log.Fatal("Failed to load nodes:", err)
	}

	http.HandleFunc("/", handleAdmitRequest)

	log.Println("Server listening on :3000")
	if err := http.ListenAndServe(":3000", nil); err != nil {
		log.Fatal(err)
	}
}