chore: add loopback detect for direct outbound

adapter/outbound/direct_loopback_detect.go

@@ -0,0 +1,68 @@
+package outbound
+
+import (
+	"net/netip"
+
+	"github.com/metacubex/mihomo/common/callback"
+	C "github.com/metacubex/mihomo/constant"
+
+	"github.com/puzpuzpuz/xsync/v3"
+)
+
+type loopBackDetector struct {
+	connMap       *xsync.MapOf[netip.AddrPort, struct{}]
+	packetConnMap *xsync.MapOf[netip.AddrPort, struct{}]
+}
+
+func newLoopBackDetector() *loopBackDetector {
+	return &loopBackDetector{
+		connMap:       xsync.NewMapOf[netip.AddrPort, struct{}](),
+		packetConnMap: xsync.NewMapOf[netip.AddrPort, struct{}](),
+	}
+}
+
+func (l *loopBackDetector) NewConn(conn C.Conn) C.Conn {
+	metadata := C.Metadata{}
+	if metadata.SetRemoteAddr(conn.LocalAddr()) != nil {
+		return conn
+	}
+	connAddr := metadata.AddrPort()
+	if !connAddr.IsValid() {
+		return conn
+	}
+	l.connMap.Store(connAddr, struct{}{})
+	return callback.NewCloseCallbackConn(conn, func() {
+		l.connMap.Delete(connAddr)
+	})
+}
+
+func (l *loopBackDetector) NewPacketConn(conn C.PacketConn) C.PacketConn {
+	metadata := C.Metadata{}
+	if metadata.SetRemoteAddr(conn.LocalAddr()) != nil {
+		return conn
+	}
+	connAddr := metadata.AddrPort()
+	if !connAddr.IsValid() {
+		return conn
+	}
+	l.packetConnMap.Store(connAddr, struct{}{})
+	return callback.NewCloseCallbackPacketConn(conn, func() {
+		l.packetConnMap.Delete(connAddr)
+	})
+}
+
+func (l *loopBackDetector) CheckConn(connAddr netip.AddrPort) bool {
+	if !connAddr.IsValid() {
+		return false
+	}
+	_, ok := l.connMap.Load(connAddr)
+	return ok
+}
+
+func (l *loopBackDetector) CheckPacketConn(connAddr netip.AddrPort) bool {
+	if !connAddr.IsValid() {
+		return false
+	}
+	_, ok := l.packetConnMap.Load(connAddr)
+	return ok
+}