/usr/share/gocode/src/code.google.com/p/go.net/ipv4/control_linux.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 | // 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 (
"os"
"syscall"
"unsafe"
)
// Linux provides a convenient path control option IP_PKTINFO that
// contains IP_SENDSRCADDR, IP_RECVDSTADDR, IP_RECVIF and IP_SENDIF.
const pktinfo = FlagSrc | FlagDst | FlagInterface
func setControlMessage(fd int, opt *rawOpt, cf ControlFlags, on bool) error {
opt.Lock()
defer opt.Unlock()
if cf&FlagTTL != 0 {
if err := setIPv4ReceiveTTL(fd, on); err != nil {
return err
}
if on {
opt.set(FlagTTL)
} else {
opt.clear(FlagTTL)
}
}
if cf&pktinfo != 0 {
if err := setIPv4PacketInfo(fd, on); err != nil {
return err
}
if on {
opt.set(cf & pktinfo)
} else {
opt.clear(cf & pktinfo)
}
}
return nil
}
func newControlMessage(opt *rawOpt) (oob []byte) {
opt.Lock()
defer opt.Unlock()
l, off := 0, 0
if opt.isset(FlagTTL) {
l += syscall.CmsgSpace(1)
}
if opt.isset(pktinfo) {
l += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
}
if l > 0 {
oob = make([]byte, l)
if opt.isset(FlagTTL) {
m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
m.Level = ianaProtocolIP
m.Type = syscall.IP_RECVTTL
m.SetLen(syscall.CmsgLen(1))
off += syscall.CmsgSpace(1)
}
if opt.isset(pktinfo) {
m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
m.Level = ianaProtocolIP
m.Type = syscall.IP_PKTINFO
m.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
off += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
}
}
return
}
func parseControlMessage(b []byte) (*ControlMessage, error) {
if len(b) == 0 {
return nil, nil
}
cmsgs, err := syscall.ParseSocketControlMessage(b)
if err != nil {
return nil, os.NewSyscallError("parse socket control message", err)
}
cm := &ControlMessage{}
for _, m := range cmsgs {
if m.Header.Level != ianaProtocolIP {
continue
}
switch m.Header.Type {
case syscall.IP_TTL:
cm.TTL = int(*(*byte)(unsafe.Pointer(&m.Data[:1][0])))
case syscall.IP_PKTINFO:
pi := (*syscall.Inet4Pktinfo)(unsafe.Pointer(&m.Data[0]))
cm.IfIndex = int(pi.Ifindex)
cm.Dst = pi.Addr[:]
}
}
return cm, nil
}
func marshalControlMessage(cm *ControlMessage) (oob []byte) {
if cm == nil {
return
}
l, off := 0, 0
pion := false
if cm.Src.To4() != nil || cm.IfIndex != 0 {
pion = true
l += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
}
if l > 0 {
oob = make([]byte, l)
if pion {
m := (*syscall.Cmsghdr)(unsafe.Pointer(&oob[off]))
m.Level = ianaProtocolIP
m.Type = syscall.IP_PKTINFO
m.SetLen(syscall.CmsgLen(syscall.SizeofInet4Pktinfo))
pi := (*syscall.Inet4Pktinfo)(unsafe.Pointer(&oob[off+syscall.CmsgLen(0)]))
if ip := cm.Src.To4(); ip != nil {
copy(pi.Addr[:], ip)
}
if cm.IfIndex != 0 {
pi.Ifindex = int32(cm.IfIndex)
}
off += syscall.CmsgSpace(syscall.SizeofInet4Pktinfo)
}
}
return
}
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