Add Darwin FFI for macOS in-process embedding

- ffi_darwin.go: C-exported functions (minising_start/stop/is_running/
  get_peers/get_build_info/free) for c-archive buildmode
- main.go: exclude darwin+cgo from CLI build
- go.mod: fix sing-tun replace path after directory reorganization

ffi_darwin.go

@@ -0,0 +1,160 @@
+//go:build darwin && cgo
+
+package main
+
+/*
+#include <stdlib.h>
+*/
+import "C"
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+	"sync"
+	"unsafe"
+
+	"github.com/netkits-dev/mini-sing/option"
+)
+
+var (
+	ffiMu     sync.Mutex
+	ffiBox    *Box
+	ffiCtx    context.Context
+	ffiCancel context.CancelFunc
+
+	// Set via -ldflags at build time
+	buildTime = "unknown"
+	buildHash = "unknown"
+)
+
+//export minising_start
+func minising_start(cconfig *C.char) *C.char {
+	config := C.GoString(cconfig)
+
+	// Setup logging from config
+	if logPath := extractLogPath(config); logPath != "" {
+		setupLog(logPath)
+	}
+	log.Printf("[ffi] mini-sing build=%s hash=%s", buildTime, buildHash)
+	log.Println("[ffi] start called, config bytes:", len(config))
+
+	var opts option.Options
+	if err := json.Unmarshal([]byte(config), &opts); err != nil {
+		return C.CString("parse: " + err.Error())
+	}
+
+	ffiMu.Lock()
+	defer ffiMu.Unlock()
+
+	if ffiBox != nil {
+		log.Println("[ffi] already running, rejecting start")
+		return C.CString("already running")
+	}
+
+	log.Println("[ffi] creating box")
+	ffiCtx, ffiCancel = context.WithCancel(context.Background())
+	box, err := NewBox(ffiCtx, opts)
+	if err != nil {
+		log.Println("[ffi] create box failed:", err)
+		ffiCancel()
+		return C.CString("create: " + err.Error())
+	}
+
+	log.Println("[ffi] box created, starting")
+	if err := box.Start(); err != nil {
+		log.Println("[ffi] start failed:", err)
+		box.Close()
+		ffiCancel()
+		return C.CString("start: " + err.Error())
+	}
+	ffiBox = box
+	log.Println("[ffi] started successfully")
+	return nil // nil = success
+}
+
+//export minising_stop
+func minising_stop() {
+	log.Println("[ffi] stop called")
+	ffiMu.Lock()
+	defer ffiMu.Unlock()
+	if ffiBox != nil {
+		ffiCancel()
+		ffiBox.Close()
+		ffiBox = nil
+		log.Println("[ffi] stopped")
+	}
+}
+
+//export minising_is_running
+func minising_is_running() C.int {
+	ffiMu.Lock()
+	defer ffiMu.Unlock()
+	if ffiBox != nil {
+		return 1
+	}
+	return 0
+}
+
+//export minising_get_peers
+func minising_get_peers() *C.char {
+	ffiMu.Lock()
+	box := ffiBox
+	ffiMu.Unlock()
+
+	if box == nil {
+		return C.CString(`{"error":"not running"}`)
+	}
+	ts := box.findTailscale()
+	if ts == nil {
+		return C.CString(`{"error":"tailscale not enabled"}`)
+	}
+	self, peers, err := ts.Peers()
+	if err != nil {
+		return C.CString(fmt.Sprintf(`{"error":"%s"}`, err.Error()))
+	}
+	data, _ := json.Marshal(map[string]any{"self": self, "peers": peers})
+	return C.CString(string(data))
+}
+
+//export minising_get_build_info
+func minising_get_build_info() *C.char {
+	info := fmt.Sprintf(`{"build_time":"%s","build_hash":"%s"}`, buildTime, buildHash)
+	return C.CString(info)
+}
+
+//export minising_free
+func minising_free(p *C.char) {
+	C.free(unsafe.Pointer(p))
+}
+
+func extractLogPath(config string) string {
+	var raw map[string]json.RawMessage
+	if err := json.Unmarshal([]byte(config), &raw); err != nil {
+		return ""
+	}
+	logRaw, ok := raw["log"]
+	if !ok {
+		return ""
+	}
+	var logObj struct {
+		Output string `json:"output"`
+	}
+	if err := json.Unmarshal(logRaw, &logObj); err != nil {
+		return ""
+	}
+	return logObj.Output
+}
+
+func setupLog(logPath string) {
+	f, err := os.OpenFile(logPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
+	if err != nil {
+		return
+	}
+	log.SetOutput(f)
+	log.SetFlags(log.Ldate | log.Ltime | log.Lmicroseconds)
+}
+
+func main() {} // required for c-archive buildmode

go.mod

@@ -23,7 +23,7 @@ require (
 
 replace github.com/netkits-dev/mini-dns => ../mini-dns
 
-replace github.com/sagernet/sing-tun => ../sing-tun
+replace github.com/sagernet/sing-tun => ../reference/sing-tun
 
 replace github.com/netkits-dev/tailnet => ../tailnet
 

main.go

@@ -1,4 +1,4 @@
-//go:build !android || !cgo
+//go:build !cgo || (!android && !darwin)
 
 package main