mega refactor internet.TCPConn->tcp.Conn

internal/ip.go

@@ -0,0 +1,44 @@
+package internal
+
+import (
+	"encoding/binary"
+	"errors"
+)
+
+var (
+	errUnsupportedIP             = errors.New("unsupported IP version")
+	errInvalidIPVersionToSetAddr = errors.New("invalid ip version to setDstAddr")
+)
+
+func GetIPSourceAddr(buf []byte) (addr []byte, id uint16, err error) {
+	version := buf[0] >> 4
+	switch version { //
+	case 4:
+		addr = buf[12:16]
+		id = binary.BigEndian.Uint16(buf[4:6])
+	case 6:
+		addr = buf[8:24]
+	default:
+		err = errUnsupportedIP
+	}
+	return addr, id, err
+}
+
+func SetIPDestinationAddr(buf []byte, id uint16, addr []byte) (err error) {
+	var dstaddr []byte
+	version := buf[0] >> 4
+	switch version {
+	case 4:
+		dstaddr = buf[16:20]
+		binary.BigEndian.PutUint16(buf[4:6], id)
+	case 6:
+		dstaddr = buf[24:40]
+	default:
+		err = errUnsupportedIP
+	}
+	if err == nil && len(dstaddr) != len(addr) {
+		return errInvalidIPVersionToSetAddr
+	}
+	copy(dstaddr, addr)
+	return nil
+}