ipv6

package
v0.13.0-beta.0 Latest Latest
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 Go to latest Published: Jan 10, 2016 License: MPL-2.0 Imports: 10 Imported by: 0

Documentation

Overview

Package ipv6 implements IP-level socket options for the Internet Protocol version 6.

The package provides IP-level socket options that allow manipulation of IPv6 facilities.

The IPv6 protocol is defined in RFC 2460. Basic and advanced socket interface extensions are defined in RFC 3493 and RFC 3542. Socket interface extensions for multicast source filters are defined in RFC 3678. MLDv1 and MLDv2 are defined in RFC 2710 and RFC 3810. Source-specific multicast is defined in RFC 4607.

Unicasting

The options for unicasting are available for net.TCPConn, net.UDPConn and net.IPConn which are created as network connections that use the IPv6 transport. When a single TCP connection carrying a data flow of multiple packets needs to indicate the flow is important, ipv6.Conn is used to set the traffic class field on the IPv6 header for each packet. 

ln, err := net.Listen("tcp6", "[::]:1024")
if err != nil {
	// error handling
}
defer ln.Close()
for {
	c, err := ln.Accept()
	if err != nil {
		// error handling
	}
	go func(c net.Conn) {
		defer c.Close()

The outgoing packets will be labeled DiffServ assured forwarding class 1 low drop precedence, known as AF11 packets. 

		if err := ipv6.NewConn(c).SetTrafficClass(0x28); err != nil {
			// error handling
		}
		if _, err := c.Write(data); err != nil {
			// error handling
		}
	}(c)
}

Multicasting

The options for multicasting are available for net.UDPConn and net.IPconn which are created as network connections that use the IPv6 transport. A few network facilities must be prepared before you begin multicasting, at a minimum joining network interfaces and multicast groups. 

en0, err := net.InterfaceByName("en0")
if err != nil {
	// error handling
}
en1, err := net.InterfaceByIndex(911)
if err != nil {
	// error handling
}
group := net.ParseIP("ff02::114")

First, an application listens to an appropriate address with an appropriate service port. 

c, err := net.ListenPacket("udp6", "[::]:1024")
if err != nil {
	// error handling
}
defer c.Close()

Second, the application joins multicast groups, starts listening to the groups on the specified network interfaces. Note that the service port for transport layer protocol does not matter with this operation as joining groups affects only network and link layer protocols, such as IPv6 and Ethernet. 

p := ipv6.NewPacketConn(c)
if err := p.JoinGroup(en0, &net.UDPAddr{IP: group}); err != nil {
	// error handling
}
if err := p.JoinGroup(en1, &net.UDPAddr{IP: group}); err != nil {
	// error handling
}

The application might set per packet control message transmissions between the protocol stack within the kernel. When the application needs a destination address on an incoming packet, SetControlMessage of ipv6.PacketConn is used to enable control message transmissons. 

if err := p.SetControlMessage(ipv6.FlagDst, true); err != nil {
	// error handling
}

The application could identify whether the received packets are of interest by using the control message that contains the destination address of the received packet. 

b := make([]byte, 1500)
for {
	n, rcm, src, err := p.ReadFrom(b)
	if err != nil {
		// error handling
	}
	if rcm.Dst.IsMulticast() {
		if rcm.Dst.Equal(group) {
			// joined group, do something
		} else {
			// unknown group, discard
			continue
		}
	}

The application can also send both unicast and multicast packets. 

	p.SetTrafficClass(0x0)
	p.SetHopLimit(16)
	if _, err := p.WriteTo(data[:n], nil, src); err != nil {
		// error handling
	}
	dst := &net.UDPAddr{IP: group, Port: 1024}
	wcm := ipv6.ControlMessage{TrafficClass: DiffServCS7, HopLimit: 1}
	for _, ifi := range []*net.Interface{en0, en1} {
		wcm.IfIndex = ifi.Index
		if _, err := p.WriteTo(data[:n], &wcm, dst); err != nil {
			// error handling
		}
	}
}

More multicasting

An application that uses PacketConn may join multiple multicast groups. For example, a UDP listener with port 1024 might join two different groups across over two different network interfaces by using: 

c, err := net.ListenPacket("udp6", "[::]:1024")
if err != nil {
	// error handling
}
defer c.Close()
p := ipv6.NewPacketConn(c)
if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff02::1:114")}); err != nil {
	// error handling
}
if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff02::2:114")}); err != nil {
	// error handling
}
if err := p.JoinGroup(en1, &net.UDPAddr{IP: net.ParseIP("ff02::2:114")}); err != nil {
	// error handling
}

It is possible for multiple UDP listeners that listen on the same UDP port to join the same multicast group. The net package will provide a socket that listens to a wildcard address with reusable UDP port when an appropriate multicast address prefix is passed to the net.ListenPacket or net.ListenUDP. 

c1, err := net.ListenPacket("udp6", "[ff02::]:1024")
if err != nil {
	// error handling
}
defer c1.Close()
c2, err := net.ListenPacket("udp6", "[ff02::]:1024")
if err != nil {
	// error handling
}
defer c2.Close()
p1 := ipv6.NewPacketConn(c1)
if err := p1.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff02::114")}); err != nil {
	// error handling
}
p2 := ipv6.NewPacketConn(c2)
if err := p2.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff02::114")}); err != nil {
	// error handling
}

Also it is possible for the application to leave or rejoin a multicast group on the network interface. 

if err := p.LeaveGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff02::114")}); err != nil {
	// error handling
}
if err := p.JoinGroup(en0, &net.UDPAddr{IP: net.ParseIP("ff01::114")}); err != nil {
	// error handling
}

Source-specific multicasting

An application that uses PacketConn on MLDv2 supported platform is able to join source-specific multicast groups. The application may use JoinSourceSpecificGroup and LeaveSourceSpecificGroup for the operation known as "include" mode, 

ssmgroup := net.UDPAddr{IP: net.ParseIP("ff32::8000:9")}
ssmsource := net.UDPAddr{IP: net.ParseIP("fe80::cafe")}
if err := p.JoinSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
	// error handling
}
if err := p.LeaveSourceSpecificGroup(en0, &ssmgroup, &ssmsource); err != nil {
	// error handling
}

or JoinGroup, ExcludeSourceSpecificGroup, IncludeSourceSpecificGroup and LeaveGroup for the operation known as "exclude" mode. 

exclsource := net.UDPAddr{IP: net.ParseIP("fe80::dead")}
if err := p.JoinGroup(en0, &ssmgroup); err != nil {
	// error handling
}
if err := p.ExcludeSourceSpecificGroup(en0, &ssmgroup, &exclsource); err != nil {
	// error handling
}
if err := p.LeaveGroup(en0, &ssmgroup); err != nil {
	// error handling
}

Note that it depends on each platform implementation what happens when an application which runs on MLDv2 unsupported platform uses JoinSourceSpecificGroup and LeaveSourceSpecificGroup. In general the platform tries to fall back to conversations using MLDv1 and starts to listen to multicast traffic. In the fallback case, ExcludeSourceSpecificGroup and IncludeSourceSpecificGroup may return an error.

Index

Constants

View Source 
const (
	Version   = 6  // protocol version
	HeaderLen = 40 // header length
)

Variables

This section is empty.

Functions

This section is empty.

Types

type Conn 

type Conn struct {
	// contains filtered or unexported fields
}

A Conn represents a network endpoint that uses IPv6 transport. It allows to set basic IP-level socket options such as traffic class and hop limit.

func NewConn 

func NewConn(c net.Conn) *Conn

NewConn returns a new Conn.

func (*Conn) HopLimit 

func (c *Conn) HopLimit() (int, error)

HopLimit returns the hop limit field value for outgoing packets.

func (*Conn) PathMTU 

func (c *Conn) PathMTU() (int, error)

PathMTU returns a path MTU value for the destination associated with the endpoint.

func (*Conn) SetHopLimit 

func (c *Conn) SetHopLimit(hoplim int) error

SetHopLimit sets the hop limit field value for future outgoing packets.

func (*Conn) SetTrafficClass 

func (c *Conn) SetTrafficClass(tclass int) error

SetTrafficClass sets the traffic class field value for future outgoing packets.

func (*Conn) TrafficClass 

func (c *Conn) TrafficClass() (int, error)

TrafficClass returns the traffic class field value for outgoing packets.

type ControlFlags 

type ControlFlags uint

A ControlFlags represents per packet basis IP-level socket option control flags. 

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
)

type ControlMessage 

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
}

A ControlMessage represents per packet basis IP-level socket options.

func (*ControlMessage) String 

func (cm *ControlMessage) String() string
type Header struct {
	Version      int    // protocol version
	TrafficClass int    // traffic class
	FlowLabel    int    // flow label
	PayloadLen   int    // payload length
	NextHeader   int    // next header
	HopLimit     int    // hop limit
	Src          net.IP // source address
	Dst          net.IP // destination address
}

A Header represents an IPv6 base header.

func ParseHeader 

func ParseHeader(b []byte) (*Header, error)

ParseHeader parses b as an IPv6 base header.

func (*Header) String 

func (h *Header) String() string

type ICMPFilter 

type ICMPFilter struct {
	// contains filtered or unexported fields
}

An ICMPFilter represents an ICMP message filter for incoming packets. The filter belongs to a packet delivery path on a host and it cannot interact with forwarding packets or tunnel-outer packets.

Note: RFC 2460 defines a reasonable role model. A node means a device that implements IP. A router means a node that forwards IP packets not explicitly addressed to itself, and a host means a node that is not a router.

func (*ICMPFilter) Accept 

func (f *ICMPFilter) Accept(typ ICMPType)

Accept accepts incoming ICMP packets including the type field value typ.

func (*ICMPFilter) Block 

func (f *ICMPFilter) Block(typ ICMPType)

Block blocks incoming ICMP packets including the type field value typ.

func (*ICMPFilter) SetAll 

func (f *ICMPFilter) SetAll(block bool)

SetAll sets the filter action to the filter.

func (*ICMPFilter) WillBlock 

func (f *ICMPFilter) WillBlock(typ ICMPType) bool

WillBlock reports whether the ICMP type will be blocked.

type ICMPType 

type ICMPType int

An ICMPType represents a type of ICMP message. 

const (
	ICMPTypeDestinationUnreachable                ICMPType = 1   // Destination Unreachable
	ICMPTypePacketTooBig                          ICMPType = 2   // Packet Too Big
	ICMPTypeTimeExceeded                          ICMPType = 3   // Time Exceeded
	ICMPTypeParameterProblem                      ICMPType = 4   // Parameter Problem
	ICMPTypeEchoRequest                           ICMPType = 128 // Echo Request
	ICMPTypeEchoReply                             ICMPType = 129 // Echo Reply
	ICMPTypeMulticastListenerQuery                ICMPType = 130 // Multicast Listener Query
	ICMPTypeMulticastListenerReport               ICMPType = 131 // Multicast Listener Report
	ICMPTypeMulticastListenerDone                 ICMPType = 132 // Multicast Listener Done
	ICMPTypeRouterSolicitation                    ICMPType = 133 // Router Solicitation
	ICMPTypeRouterAdvertisement                   ICMPType = 134 // Router Advertisement
	ICMPTypeNeighborSolicitation                  ICMPType = 135 // Neighbor Solicitation
	ICMPTypeNeighborAdvertisement                 ICMPType = 136 // Neighbor Advertisement
	ICMPTypeRedirect                              ICMPType = 137 // Redirect Message
	ICMPTypeRouterRenumbering                     ICMPType = 138 // Router Renumbering
	ICMPTypeNodeInformationQuery                  ICMPType = 139 // ICMP Node Information Query
	ICMPTypeNodeInformationResponse               ICMPType = 140 // ICMP Node Information Response
	ICMPTypeInverseNeighborDiscoverySolicitation  ICMPType = 141 // Inverse Neighbor Discovery Solicitation Message
	ICMPTypeInverseNeighborDiscoveryAdvertisement ICMPType = 142 // Inverse Neighbor Discovery Advertisement Message
	ICMPTypeVersion2MulticastListenerReport       ICMPType = 143 // Version 2 Multicast Listener Report
	ICMPTypeHomeAgentAddressDiscoveryRequest      ICMPType = 144 // Home Agent Address Discovery Request Message
	ICMPTypeHomeAgentAddressDiscoveryReply        ICMPType = 145 // Home Agent Address Discovery Reply Message
	ICMPTypeMobilePrefixSolicitation              ICMPType = 146 // Mobile Prefix Solicitation
	ICMPTypeMobilePrefixAdvertisement             ICMPType = 147 // Mobile Prefix Advertisement
	ICMPTypeCertificationPathSolicitation         ICMPType = 148 // Certification Path Solicitation Message
	ICMPTypeCertificationPathAdvertisement        ICMPType = 149 // Certification Path Advertisement Message
	ICMPTypeMulticastRouterAdvertisement          ICMPType = 151 // Multicast Router Advertisement
	ICMPTypeMulticastRouterSolicitation           ICMPType = 152 // Multicast Router Solicitation
	ICMPTypeMulticastRouterTermination            ICMPType = 153 // Multicast Router Termination
	ICMPTypeFMIPv6                                ICMPType = 154 // FMIPv6 Messages
	ICMPTypeRPLControl                            ICMPType = 155 // RPL Control Message
	ICMPTypeILNPv6LocatorUpdate                   ICMPType = 156 // ILNPv6 Locator Update Message
	ICMPTypeDuplicateAddressRequest               ICMPType = 157 // Duplicate Address Request
	ICMPTypeDuplicateAddressConfirmation          ICMPType = 158 // Duplicate Address Confirmation
	ICMPTypeMPLControl                            ICMPType = 159 // MPL Control Message
)

Internet Control Message Protocol version 6 (ICMPv6) Parameters, Updated: 2015-07-07

func (ICMPType) Protocol 

func (typ ICMPType) Protocol() int

Protocol returns the ICMPv6 protocol number.

func (ICMPType) String 

func (typ ICMPType) String() string

type PacketConn 

type PacketConn struct {
	// contains filtered or unexported fields
}

A PacketConn represents a packet network endpoint that uses IPv6 transport. It is used to control several IP-level socket options including IPv6 header manipulation. It also provides datagram based network I/O methods specific to the IPv6 and higher layer protocols such as OSPF, GRE, and UDP.

func NewPacketConn 

func NewPacketConn(c net.PacketConn) *PacketConn

NewPacketConn returns a new PacketConn using c as its underlying transport.

func (*PacketConn) Checksum 

func (c *PacketConn) Checksum() (on bool, offset int, err error)

Checksum reports whether the kernel will compute, store or verify a checksum for both incoming and outgoing packets. If on is true, it returns an offset in bytes into the data of where the checksum field is located.

func (*PacketConn) Close 

func (c *PacketConn) Close() error

Close closes the endpoint.

func (*PacketConn) ExcludeSourceSpecificGroup 

func (c *PacketConn) ExcludeSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error

ExcludeSourceSpecificGroup excludes the source-specific group from the already joined any-source groups by JoinGroup on the interface ifi.

func (*PacketConn) HopLimit 

func (c *PacketConn) HopLimit() (int, error)

HopLimit returns the hop limit field value for outgoing packets.

func (*PacketConn) ICMPFilter 

func (c *PacketConn) ICMPFilter() (*ICMPFilter, error)

ICMPFilter returns an ICMP filter.

func (*PacketConn) IncludeSourceSpecificGroup 

func (c *PacketConn) IncludeSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error

IncludeSourceSpecificGroup includes the excluded source-specific group by ExcludeSourceSpecificGroup again on the interface ifi.

func (*PacketConn) JoinGroup 

func (c *PacketConn) JoinGroup(ifi *net.Interface, group net.Addr) error

JoinGroup joins the group address group on the interface ifi. By default all sources that can cast data to group are accepted. It's possible to mute and unmute data transmission from a specific source by using ExcludeSourceSpecificGroup and IncludeSourceSpecificGroup. JoinGroup uses the system assigned multicast interface when ifi is nil, although this is not recommended because the assignment depends on platforms and sometimes it might require routing configuration.

func (*PacketConn) JoinSourceSpecificGroup 

func (c *PacketConn) JoinSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error

JoinSourceSpecificGroup joins the source-specific group comprising group and source on the interface ifi. JoinSourceSpecificGroup uses the system assigned multicast interface when ifi is nil, although this is not recommended because the assignment depends on platforms and sometimes it might require routing configuration.

func (*PacketConn) LeaveGroup 

func (c *PacketConn) LeaveGroup(ifi *net.Interface, group net.Addr) error

LeaveGroup leaves the group address group on the interface ifi regardless of whether the group is any-source group or source-specific group.

func (*PacketConn) LeaveSourceSpecificGroup 

func (c *PacketConn) LeaveSourceSpecificGroup(ifi *net.Interface, group, source net.Addr) error

LeaveSourceSpecificGroup leaves the source-specific group on the interface ifi.

func (*PacketConn) MulticastHopLimit 

func (c *PacketConn) MulticastHopLimit() (int, error)

MulticastHopLimit returns the hop limit field value for outgoing multicast packets.

func (*PacketConn) MulticastInterface 

func (c *PacketConn) MulticastInterface() (*net.Interface, error)

MulticastInterface returns the default interface for multicast packet transmissions.

func (*PacketConn) MulticastLoopback 

func (c *PacketConn) MulticastLoopback() (bool, error)

MulticastLoopback reports whether transmitted multicast packets should be copied and send back to the originator.

func (*PacketConn) ReadFrom 

func (c *PacketConn) ReadFrom(b []byte) (n int, cm *ControlMessage, src net.Addr, err error)

ReadFrom reads a payload of the received IPv6 datagram, from the endpoint c, copying the payload into b. It returns the number of bytes copied into b, the control message cm and the source address src of the received datagram.

func (*PacketConn) SetChecksum 

func (c *PacketConn) SetChecksum(on bool, offset int) error

SetChecksum enables the kernel checksum processing. If on is ture, the offset should be an offset in bytes into the data of where the checksum field is located.

func (*PacketConn) SetControlMessage 

func (c *PacketConn) SetControlMessage(cf ControlFlags, on bool) error

SetControlMessage allows to receive the per packet basis IP-level socket options.

func (*PacketConn) SetDeadline 

func (c *PacketConn) SetDeadline(t time.Time) error

SetDeadline sets the read and write deadlines associated with the endpoint.

func (*PacketConn) SetHopLimit 

func (c *PacketConn) SetHopLimit(hoplim int) error

SetHopLimit sets the hop limit field value for future outgoing packets.

func (*PacketConn) SetICMPFilter 

func (c *PacketConn) SetICMPFilter(f *ICMPFilter) error

SetICMPFilter deploys the ICMP filter.

func (*PacketConn) SetMulticastHopLimit 

func (c *PacketConn) SetMulticastHopLimit(hoplim int) error

SetMulticastHopLimit sets the hop limit field value for future outgoing multicast packets.

func (*PacketConn) SetMulticastInterface 

func (c *PacketConn) SetMulticastInterface(ifi *net.Interface) error

SetMulticastInterface sets the default interface for future multicast packet transmissions.

func (*PacketConn) SetMulticastLoopback 

func (c *PacketConn) SetMulticastLoopback(on bool) error

SetMulticastLoopback sets whether transmitted multicast packets should be copied and send back to the originator.

func (*PacketConn) SetReadDeadline 

func (c *PacketConn) SetReadDeadline(t time.Time) error

SetReadDeadline sets the read deadline associated with the endpoint.

func (*PacketConn) SetTrafficClass 

func (c *PacketConn) SetTrafficClass(tclass int) error

SetTrafficClass sets the traffic class field value for future outgoing packets.

func (*PacketConn) SetWriteDeadline 

func (c *PacketConn) SetWriteDeadline(t time.Time) error

SetWriteDeadline sets the write deadline associated with the endpoint.

func (*PacketConn) TrafficClass 

func (c *PacketConn) TrafficClass() (int, error)

TrafficClass returns the traffic class field value for outgoing packets.

func (*PacketConn) WriteTo 

func (c *PacketConn) WriteTo(b []byte, cm *ControlMessage, dst net.Addr) (n int, err error)

WriteTo writes a payload of the IPv6 datagram, to the destination address dst through the endpoint c, copying the payload from b. It returns the number of bytes written. The control message cm allows the IPv6 header fields and the datagram path to be specified. The cm may be nil if control of the outgoing datagram is not required.

Source Files

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