Add direct io option for clash api

experimental/trackerconn/packet_conn.go

@@ -0,0 +1,37 @@
+package trackerconn
+
+import (
+	"github.com/sagernet/sing/common/buf"
+	M "github.com/sagernet/sing/common/metadata"
+	N "github.com/sagernet/sing/common/network"
+
+	"go.uber.org/atomic"
+)
+
+type PacketConn struct {
+	N.PacketConn
+	readCounter  *atomic.Int64
+	writeCounter *atomic.Int64
+}
+
+func NewPacket(conn N.PacketConn, readCounter *atomic.Int64, writeCounter *atomic.Int64) *PacketConn {
+	return &PacketConn{conn, readCounter, writeCounter}
+}
+
+func (c *PacketConn) ReadPacket(buffer *buf.Buffer) (destination M.Socksaddr, err error) {
+	destination, err = c.PacketConn.ReadPacket(buffer)
+	if err == nil {
+		c.readCounter.Add(int64(buffer.Len()))
+	}
+	return
+}
+
+func (c *PacketConn) WritePacket(buffer *buf.Buffer, destination M.Socksaddr) error {
+	dataLen := int64(buffer.Len())
+	err := c.PacketConn.WritePacket(buffer, destination)
+	if err != nil {
+		return err
+	}
+	c.writeCounter.Add(dataLen)
+	return nil
+}