/usr/share/gocode/src/code.google.com/p/go.net/ipv4/header.go is in golang-go.net-dev 0.0~hg20131201-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 | // Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ipv4
import (
"errors"
"fmt"
"net"
"runtime"
"syscall"
"unsafe"
)
var (
errMissingAddress = errors.New("missing address")
errMissingHeader = errors.New("missing header")
errHeaderTooShort = errors.New("header too short")
errBufferTooShort = errors.New("buffer too short")
errInvalidConnType = errors.New("invalid conn type")
)
// References:
//
// RFC 791 Internet Protocol
// http://tools.ietf.org/html/rfc791
// RFC 1112 Host Extensions for IP Multicasting
// http://tools.ietf.org/html/rfc1112
// RFC 1122 Requirements for Internet Hosts
// http://tools.ietf.org/html/rfc1122
const (
Version = 4 // protocol version
HeaderLen = 20 // header length without extension headers
maxHeaderLen = 60 // sensible default, revisit if later RFCs define new usage of version and header length fields
)
const (
posTOS = 1 // type-of-service
posTotalLen = 2 // packet total length
posID = 4 // identification
posFragOff = 6 // fragment offset
posTTL = 8 // time-to-live
posProtocol = 9 // next protocol
posChecksum = 10 // checksum
posSrc = 12 // source address
posDst = 16 // destination address
)
type HeaderFlags int
const (
MoreFragments HeaderFlags = 1 << iota // more fragments flag
DontFragment // don't fragment flag
)
// A Header represents an IPv4 header.
type Header struct {
Version int // protocol version
Len int // header length
TOS int // type-of-service
TotalLen int // packet total length
ID int // identification
Flags HeaderFlags // flags
FragOff int // fragment offset
TTL int // time-to-live
Protocol int // next protocol
Checksum int // checksum
Src net.IP // source address
Dst net.IP // destination address
Options []byte // options, extension headers
}
func (h *Header) String() string {
if h == nil {
return "<nil>"
}
return fmt.Sprintf("ver: %v, hdrlen: %v, tos: %#x, totallen: %v, id: %#x, flags: %#x, fragoff: %#x, ttl: %v, proto: %v, cksum: %#x, src: %v, dst: %v", h.Version, h.Len, h.TOS, h.TotalLen, h.ID, h.Flags, h.FragOff, h.TTL, h.Protocol, h.Checksum, h.Src, h.Dst)
}
// Please refer to the online manual; IP(4) on Darwin, FreeBSD and
// OpenBSD. IP(7) on Linux.
const supportsNewIPInput = runtime.GOOS == "linux" || runtime.GOOS == "openbsd"
// Marshal returns the binary encoding of the IPv4 header h.
func (h *Header) Marshal() ([]byte, error) {
if h == nil {
return nil, syscall.EINVAL
}
if h.Len < HeaderLen {
return nil, errHeaderTooShort
}
hdrlen := HeaderLen + len(h.Options)
b := make([]byte, hdrlen)
b[0] = byte(Version<<4 | (hdrlen >> 2 & 0x0f))
b[posTOS] = byte(h.TOS)
flagsAndFragOff := (h.FragOff & 0x1fff) | int(h.Flags<<13)
if supportsNewIPInput {
b[posTotalLen], b[posTotalLen+1] = byte(h.TotalLen>>8), byte(h.TotalLen)
b[posFragOff], b[posFragOff+1] = byte(flagsAndFragOff>>8), byte(flagsAndFragOff)
} else {
*(*uint16)(unsafe.Pointer(&b[posTotalLen : posTotalLen+1][0])) = uint16(h.TotalLen)
*(*uint16)(unsafe.Pointer(&b[posFragOff : posFragOff+1][0])) = uint16(flagsAndFragOff)
}
b[posID], b[posID+1] = byte(h.ID>>8), byte(h.ID)
b[posTTL] = byte(h.TTL)
b[posProtocol] = byte(h.Protocol)
b[posChecksum], b[posChecksum+1] = byte(h.Checksum>>8), byte(h.Checksum)
if ip := h.Src.To4(); ip != nil {
copy(b[posSrc:posSrc+net.IPv4len], ip[:net.IPv4len])
}
if ip := h.Dst.To4(); ip != nil {
copy(b[posDst:posDst+net.IPv4len], ip[:net.IPv4len])
} else {
return nil, errMissingAddress
}
if len(h.Options) > 0 {
copy(b[HeaderLen:], h.Options)
}
return b, nil
}
// ParseHeader parses b as an IPv4 header.
func ParseHeader(b []byte) (*Header, error) {
if len(b) < HeaderLen {
return nil, errHeaderTooShort
}
hdrlen := int(b[0]&0x0f) << 2
if hdrlen > len(b) {
return nil, errBufferTooShort
}
h := &Header{}
h.Version = int(b[0] >> 4)
h.Len = hdrlen
h.TOS = int(b[posTOS])
if supportsNewIPInput {
h.TotalLen = int(b[posTotalLen])<<8 | int(b[posTotalLen+1])
h.FragOff = int(b[posFragOff])<<8 | int(b[posFragOff+1])
} else {
h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[posTotalLen : posTotalLen+1][0])))
h.TotalLen += hdrlen
h.FragOff = int(*(*uint16)(unsafe.Pointer(&b[posFragOff : posFragOff+1][0])))
}
h.Flags = HeaderFlags(h.FragOff&0xe000) >> 13
h.FragOff = h.FragOff & 0x1fff
h.ID = int(b[posID])<<8 | int(b[posID+1])
h.TTL = int(b[posTTL])
h.Protocol = int(b[posProtocol])
h.Checksum = int(b[posChecksum])<<8 | int(b[posChecksum+1])
h.Src = net.IPv4(b[posSrc], b[posSrc+1], b[posSrc+2], b[posSrc+3])
h.Dst = net.IPv4(b[posDst], b[posDst+1], b[posDst+2], b[posDst+3])
if hdrlen-HeaderLen > 0 {
h.Options = make([]byte, hdrlen-HeaderLen)
copy(h.Options, b[HeaderLen:])
}
return h, nil
}
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