istio.io/istio@v0.0.0-20240520182934-d79c90f27776/tools/istio-iptables/pkg/validation/vld.go (about)

     1  // Copyright Istio Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package validation
    16  
    17  import (
    18  	"encoding/binary"
    19  	"unsafe"
    20  )
    21  
    22  var nativeByteOrder binary.ByteOrder
    23  
    24  func init() {
    25  	var x uint16 = 0x0102
    26  	lowerByte := *(*byte)(unsafe.Pointer(&x))
    27  	switch lowerByte {
    28  	case 0x01:
    29  		nativeByteOrder = binary.BigEndian
    30  	case 0x02:
    31  		nativeByteOrder = binary.LittleEndian
    32  	default:
    33  		panic("Could not determine native byte order.")
    34  	}
    35  }
    36  
    37  // <arpa/inet.h>
    38  func ntohs(n16 uint16) uint16 {
    39  	if nativeByteOrder == binary.BigEndian {
    40  		return n16
    41  	}
    42  	return (n16&0xff00)>>8 | (n16&0xff)<<8
    43  }