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