header.go

Documentation: golang.org/x/net/ipv6

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package ipv6
     6  
     7  import (
     8  	"encoding/binary"
     9  	"fmt"
    10  	"net"
    11  )
    12  
    13  const (
    14  	Version   = 6  // protocol version
    15  	HeaderLen = 40 // header length
    16  )
    17  
    18  // A Header represents an IPv6 base header.
    19  type Header struct {
    20  	Version      int    // protocol version
    21  	TrafficClass int    // traffic class
    22  	FlowLabel    int    // flow label
    23  	PayloadLen   int    // payload length
    24  	NextHeader   int    // next header
    25  	HopLimit     int    // hop limit
    26  	Src          net.IP // source address
    27  	Dst          net.IP // destination address
    28  }
    29  
    30  func (h *Header) String() string {
    31  	if h == nil {
    32  		return "<nil>"
    33  	}
    34  	return fmt.Sprintf("ver=%d tclass=%#x flowlbl=%#x payloadlen=%d nxthdr=%d hoplim=%d src=%v dst=%v", h.Version, h.TrafficClass, h.FlowLabel, h.PayloadLen, h.NextHeader, h.HopLimit, h.Src, h.Dst)
    35  }
    36  
    37  // ParseHeader parses b as an IPv6 base header.
    38  func ParseHeader(b []byte) (*Header, error) {
    39  	if len(b) < HeaderLen {
    40  		return nil, errHeaderTooShort
    41  	}
    42  	h := &Header{
    43  		Version:      int(b[0]) >> 4,
    44  		TrafficClass: int(b[0]&0x0f)<<4 | int(b[1])>>4,
    45  		FlowLabel:    int(b[1]&0x0f)<<16 | int(b[2])<<8 | int(b[3]),
    46  		PayloadLen:   int(binary.BigEndian.Uint16(b[4:6])),
    47  		NextHeader:   int(b[6]),
    48  		HopLimit:     int(b[7]),
    49  	}
    50  	h.Src = make(net.IP, net.IPv6len)
    51  	copy(h.Src, b[8:24])
    52  	h.Dst = make(net.IP, net.IPv6len)
    53  	copy(h.Dst, b[24:40])
    54  	return h, nil
    55  }
    56
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