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// Copyright 2013 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 ipv6
import (
"fmt"
"net"
"sync"
"golang.org/x/net/internal/iana"
"golang.org/x/net/internal/socket"
)
// Note that RFC 3542 obsoletes RFC 2292 but OS X Snow Leopard and the
// former still support RFC 2292 only. Please be aware that almost
// all protocol implementations prohibit using a combination of RFC
// 2292 and RFC 3542 for some practical reasons.
type rawOpt struct {
sync.RWMutex
cflags ControlFlags
}
func (c *rawOpt) set(f ControlFlags) { c.cflags |= f }
func (c *rawOpt) clear(f ControlFlags) { c.cflags &^= f }
func (c *rawOpt) isset(f ControlFlags) bool { return c.cflags&f != 0 }
// A ControlFlags represents per packet basis IP-level socket option
// control flags.
type ControlFlags uint
const (
FlagTrafficClass ControlFlags = 1 << iota // pass the traffic class on the received packet
FlagHopLimit // pass the hop limit on the received packet
FlagSrc // pass the source address on the received packet
FlagDst // pass the destination address on the received packet
FlagInterface // pass the interface index on the received packet
FlagPathMTU // pass the path MTU on the received packet path
)
const flagPacketInfo = FlagDst | FlagInterface
// A ControlMessage represents per packet basis IP-level socket
// options.
type ControlMessage struct {
// Receiving socket options: SetControlMessage allows to
// receive the options from the protocol stack using ReadFrom
// method of PacketConn.
//
// Specifying socket options: ControlMessage for WriteTo
// method of PacketConn allows to send the options to the
// protocol stack.
//
TrafficClass int // traffic class, must be 1 <= value <= 255 when specifying
HopLimit int // hop limit, must be 1 <= value <= 255 when specifying
Src net.IP // source address, specifying only
Dst net.IP // destination address, receiving only
IfIndex int // interface index, must be 1 <= value when specifying
NextHop net.IP // next hop address, specifying only
MTU int // path MTU, receiving only
}
func (cm *ControlMessage) String() string {
if cm == nil {
return "<nil>"
}
return fmt.Sprintf("tclass=%#x hoplim=%d src=%v dst=%v ifindex=%d nexthop=%v mtu=%d", cm.TrafficClass, cm.HopLimit, cm.Src, cm.Dst, cm.IfIndex, cm.NextHop, cm.MTU)
}
// Marshal returns the binary encoding of cm.
func (cm *ControlMessage) Marshal() []byte {
if cm == nil {
return nil
}
var l int
tclass := false
if ctlOpts[ctlTrafficClass].name > 0 && cm.TrafficClass > 0 {
tclass = true
l += socket.ControlMessageSpace(ctlOpts[ctlTrafficClass].length)
}
hoplimit := false
if ctlOpts[ctlHopLimit].name > 0 && cm.HopLimit > 0 {
hoplimit = true
l += socket.ControlMessageSpace(ctlOpts[ctlHopLimit].length)
}
pktinfo := false
if ctlOpts[ctlPacketInfo].name > 0 && (cm.Src.To16() != nil && cm.Src.To4() == nil || cm.IfIndex > 0) {
pktinfo = true
l += socket.ControlMessageSpace(ctlOpts[ctlPacketInfo].length)
}
nexthop := false
if ctlOpts[ctlNextHop].name > 0 && cm.NextHop.To16() != nil && cm.NextHop.To4() == nil {
nexthop = true
l += socket.ControlMessageSpace(ctlOpts[ctlNextHop].length)
}
var b []byte
if l > 0 {
b = make([]byte, l)
bb := b
if tclass {
bb = ctlOpts[ctlTrafficClass].marshal(bb, cm)
}
if hoplimit {
bb = ctlOpts[ctlHopLimit].marshal(bb, cm)
}
if pktinfo {
bb = ctlOpts[ctlPacketInfo].marshal(bb, cm)
}
if nexthop {
bb = ctlOpts[ctlNextHop].marshal(bb, cm)
}
}
return b
}
// Parse parses b as a control message and stores the result in cm.
func (cm *ControlMessage) Parse(b []byte) error {
ms, err := socket.ControlMessage(b).Parse()
if err != nil {
return err
}
for _, m := range ms {
lvl, typ, l, err := m.ParseHeader()
if err != nil {
return err
}
if lvl != iana.ProtocolIPv6 {
continue
}
switch {
case typ == ctlOpts[ctlTrafficClass].name && l >= ctlOpts[ctlTrafficClass].length:
ctlOpts[ctlTrafficClass].parse(cm, m.Data(l))
case typ == ctlOpts[ctlHopLimit].name && l >= ctlOpts[ctlHopLimit].length:
ctlOpts[ctlHopLimit].parse(cm, m.Data(l))
case typ == ctlOpts[ctlPacketInfo].name && l >= ctlOpts[ctlPacketInfo].length:
ctlOpts[ctlPacketInfo].parse(cm, m.Data(l))
case typ == ctlOpts[ctlPathMTU].name && l >= ctlOpts[ctlPathMTU].length:
ctlOpts[ctlPathMTU].parse(cm, m.Data(l))
}
}
return nil
}
// NewControlMessage returns a new control message.
//
// The returned message is large enough for options specified by cf.
func NewControlMessage(cf ControlFlags) []byte {
opt := rawOpt{cflags: cf}
var l int
if opt.isset(FlagTrafficClass) && ctlOpts[ctlTrafficClass].name > 0 {
l += socket.ControlMessageSpace(ctlOpts[ctlTrafficClass].length)
}
if opt.isset(FlagHopLimit) && ctlOpts[ctlHopLimit].name > 0 {
l += socket.ControlMessageSpace(ctlOpts[ctlHopLimit].length)
}
if opt.isset(flagPacketInfo) && ctlOpts[ctlPacketInfo].name > 0 {
l += socket.ControlMessageSpace(ctlOpts[ctlPacketInfo].length)
}
if opt.isset(FlagPathMTU) && ctlOpts[ctlPathMTU].name > 0 {
l += socket.ControlMessageSpace(ctlOpts[ctlPathMTU].length)
}
var b []byte
if l > 0 {
b = make([]byte, l)
}
return b
}
// Ancillary data socket options
const (
ctlTrafficClass = iota // header field
ctlHopLimit // header field
ctlPacketInfo // inbound or outbound packet path
ctlNextHop // nexthop
ctlPathMTU // path mtu
ctlMax
)
// A ctlOpt represents a binding for ancillary data socket option.
type ctlOpt struct {
name int // option name, must be equal or greater than 1
length int // option length
marshal func([]byte, *ControlMessage) []byte
parse func(*ControlMessage, []byte)
}
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