mirror of
https://github.com/yggdrasil-network/yggdrasil-go.git
synced 2025-04-29 06:35:07 +03:00
Refactoring: move tuntap and icmpv6 into separate package
This commit is contained in:
Neil Alexander
parent
67c670ab4c
commit
0b494a8255
20 changed files with 307 additions and 240 deletions
331
src/tuntap/icmpv6.go
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331
src/tuntap/icmpv6.go
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package tuntap
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// The ICMPv6 module implements functions to easily create ICMPv6
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// packets. These functions, when mixed with the built-in Go IPv6
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// and ICMP libraries, can be used to send control messages back
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// to the host. Examples include:
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// - NDP messages, when running in TAP mode
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// - Packet Too Big messages, when packets exceed the session MTU
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// - Destination Unreachable messages, when a session prohibits
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// incoming traffic
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import (
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"encoding/binary"
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"errors"
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"net"
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"time"
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"golang.org/x/net/icmp"
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"golang.org/x/net/ipv6"
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"github.com/yggdrasil-network/yggdrasil-go/src/address"
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)
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type macAddress [6]byte
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const len_ETHER = 14
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type ICMPv6 struct {
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tun *TunAdapter
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mylladdr net.IP
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mymac macAddress
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peermacs map[address.Address]neighbor
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}
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type neighbor struct {
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mac macAddress
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learned bool
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lastadvertisement time.Time
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lastsolicitation time.Time
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}
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// Marshal returns the binary encoding of h.
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func ipv6Header_Marshal(h *ipv6.Header) ([]byte, error) {
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b := make([]byte, 40)
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b[0] |= byte(h.Version) << 4
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b[0] |= byte(h.TrafficClass) >> 4
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b[1] |= byte(h.TrafficClass) << 4
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b[1] |= byte(h.FlowLabel >> 16)
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b[2] = byte(h.FlowLabel >> 8)
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b[3] = byte(h.FlowLabel)
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binary.BigEndian.PutUint16(b[4:6], uint16(h.PayloadLen))
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b[6] = byte(h.NextHeader)
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b[7] = byte(h.HopLimit)
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copy(b[8:24], h.Src)
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copy(b[24:40], h.Dst)
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return b, nil
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}
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// Initialises the ICMPv6 module by assigning our link-local IPv6 address and
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// our MAC address. ICMPv6 messages will always appear to originate from these
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// addresses.
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func (i *ICMPv6) Init(t *TunAdapter) {
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i.tun = t
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i.peermacs = make(map[address.Address]neighbor)
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// Our MAC address and link-local address
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i.mymac = macAddress{
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0x02, 0x00, 0x00, 0x00, 0x00, 0x02}
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i.mylladdr = net.IP{
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0xFE, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0xFE}
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copy(i.mymac[:], i.tun.addr[:])
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copy(i.mylladdr[9:], i.tun.addr[1:])
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}
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// Parses an incoming ICMPv6 packet. The packet provided may be either an
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// ethernet frame containing an IP packet, or the IP packet alone. This is
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// determined by whether the TUN/TAP adapter is running in TUN (layer 3) or
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// TAP (layer 2) mode.
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func (i *ICMPv6) ParsePacket(datain []byte) {
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var response []byte
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var err error
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// Parse the frame/packet
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if i.tun.IsTAP() {
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response, err = i.UnmarshalPacketL2(datain)
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} else {
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response, err = i.UnmarshalPacket(datain, nil)
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}
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if err != nil {
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return
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}
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// Write the packet to TUN/TAP
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i.tun.Send <- response
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}
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// Unwraps the ethernet headers of an incoming ICMPv6 packet and hands off
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// the IP packet to the ParsePacket function for further processing.
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// A response buffer is also created for the response message, also complete
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// with ethernet headers.
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func (i *ICMPv6) UnmarshalPacketL2(datain []byte) ([]byte, error) {
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// Ignore non-IPv6 frames
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if binary.BigEndian.Uint16(datain[12:14]) != uint16(0x86DD) {
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return nil, nil
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}
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// Hand over to ParsePacket to interpret the IPv6 packet
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mac := datain[6:12]
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ipv6packet, err := i.UnmarshalPacket(datain[len_ETHER:], &mac)
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if err != nil {
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return nil, err
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}
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// Create the response buffer
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dataout := make([]byte, len_ETHER+ipv6.HeaderLen+32)
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// Populate the response ethernet headers
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copy(dataout[:6], datain[6:12])
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copy(dataout[6:12], i.mymac[:])
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binary.BigEndian.PutUint16(dataout[12:14], uint16(0x86DD))
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// Copy the returned packet to our response ethernet frame
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copy(dataout[len_ETHER:], ipv6packet)
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return dataout, nil
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}
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// Unwraps the IP headers of an incoming IPv6 packet and performs various
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// sanity checks on the packet - i.e. is the packet an ICMPv6 packet, does the
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// ICMPv6 message match a known expected type. The relevant handler function
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// is then called and a response packet may be returned.
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func (i *ICMPv6) UnmarshalPacket(datain []byte, datamac *[]byte) ([]byte, error) {
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// Parse the IPv6 packet headers
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ipv6Header, err := ipv6.ParseHeader(datain[:ipv6.HeaderLen])
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if err != nil {
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return nil, err
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}
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// Check if the packet is IPv6
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if ipv6Header.Version != ipv6.Version {
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return nil, err
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}
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// Check if the packet is ICMPv6
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if ipv6Header.NextHeader != 58 {
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return nil, err
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}
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// Parse the ICMPv6 message contents
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icmpv6Header, err := icmp.ParseMessage(58, datain[ipv6.HeaderLen:])
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if err != nil {
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return nil, err
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}
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// Check for a supported message type
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switch icmpv6Header.Type {
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case ipv6.ICMPTypeNeighborSolicitation:
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if !i.tun.IsTAP() {
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return nil, errors.New("Ignoring Neighbor Solicitation in TUN mode")
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}
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response, err := i.HandleNDP(datain[ipv6.HeaderLen:])
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if err == nil {
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// Create our ICMPv6 response
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responsePacket, err := CreateICMPv6(
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ipv6Header.Src, i.mylladdr,
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ipv6.ICMPTypeNeighborAdvertisement, 0,
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&icmp.DefaultMessageBody{Data: response})
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if err != nil {
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return nil, err
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}
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// Send it back
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return responsePacket, nil
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} else {
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return nil, err
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}
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case ipv6.ICMPTypeNeighborAdvertisement:
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if !i.tun.IsTAP() {
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return nil, errors.New("Ignoring Neighbor Advertisement in TUN mode")
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}
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if datamac != nil {
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var addr address.Address
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var target address.Address
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var mac macAddress
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copy(addr[:], ipv6Header.Src[:])
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copy(target[:], datain[48:64])
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copy(mac[:], (*datamac)[:])
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// i.tun.core.log.Printf("Learning peer MAC %x for %x\n", mac, target)
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neighbor := i.peermacs[target]
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neighbor.mac = mac
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neighbor.learned = true
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neighbor.lastadvertisement = time.Now()
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i.peermacs[target] = neighbor
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}
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return nil, errors.New("No response needed")
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}
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return nil, errors.New("ICMPv6 type not matched")
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}
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// Creates an ICMPv6 packet based on the given icmp.MessageBody and other
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// parameters, complete with ethernet and IP headers, which can be written
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// directly to a TAP adapter.
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func (i *ICMPv6) CreateICMPv6L2(dstmac macAddress, dst net.IP, src net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
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// Pass through to CreateICMPv6
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ipv6packet, err := CreateICMPv6(dst, src, mtype, mcode, mbody)
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if err != nil {
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return nil, err
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}
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// Create the response buffer
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dataout := make([]byte, len_ETHER+len(ipv6packet))
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// Populate the response ethernet headers
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copy(dataout[:6], dstmac[:6])
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copy(dataout[6:12], i.mymac[:])
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binary.BigEndian.PutUint16(dataout[12:14], uint16(0x86DD))
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// Copy the returned packet to our response ethernet frame
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copy(dataout[len_ETHER:], ipv6packet)
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return dataout, nil
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}
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// Creates an ICMPv6 packet based on the given icmp.MessageBody and other
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// parameters, complete with IP headers only, which can be written directly to
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// a TUN adapter, or called directly by the CreateICMPv6L2 function when
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// generating a message for TAP adapters.
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func CreateICMPv6(dst net.IP, src net.IP, mtype ipv6.ICMPType, mcode int, mbody icmp.MessageBody) ([]byte, error) {
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// Create the ICMPv6 message
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icmpMessage := icmp.Message{
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Type: mtype,
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Code: mcode,
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Body: mbody,
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}
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// Convert the ICMPv6 message into []byte
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icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(src, dst))
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if err != nil {
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return nil, err
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}
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// Create the IPv6 header
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ipv6Header := ipv6.Header{
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Version: ipv6.Version,
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NextHeader: 58,
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PayloadLen: len(icmpMessageBuf),
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HopLimit: 255,
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Src: src,
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Dst: dst,
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}
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// Convert the IPv6 header into []byte
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ipv6HeaderBuf, err := ipv6Header_Marshal(&ipv6Header)
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if err != nil {
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return nil, err
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}
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// Construct the packet
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responsePacket := make([]byte, ipv6.HeaderLen+ipv6Header.PayloadLen)
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copy(responsePacket[:ipv6.HeaderLen], ipv6HeaderBuf)
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copy(responsePacket[ipv6.HeaderLen:], icmpMessageBuf)
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// Send it back
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return responsePacket, nil
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}
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func (i *ICMPv6) CreateNDPL2(dst address.Address) ([]byte, error) {
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// Create the ND payload
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var payload [28]byte
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copy(payload[:4], []byte{0x00, 0x00, 0x00, 0x00})
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copy(payload[4:20], dst[:])
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copy(payload[20:22], []byte{0x01, 0x01})
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copy(payload[22:28], i.mymac[:6])
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// Create the ICMPv6 solicited-node address
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var dstaddr address.Address
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copy(dstaddr[:13], []byte{
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0xFF, 0x02, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x01, 0xFF})
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copy(dstaddr[13:], dst[13:16])
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// Create the multicast MAC
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var dstmac macAddress
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copy(dstmac[:2], []byte{0x33, 0x33})
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copy(dstmac[2:6], dstaddr[12:16])
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// Create the ND request
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requestPacket, err := i.CreateICMPv6L2(
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dstmac, dstaddr[:], i.mylladdr,
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ipv6.ICMPTypeNeighborSolicitation, 0,
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&icmp.DefaultMessageBody{Data: payload[:]})
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if err != nil {
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return nil, err
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}
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neighbor := i.peermacs[dstaddr]
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neighbor.lastsolicitation = time.Now()
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i.peermacs[dstaddr] = neighbor
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return requestPacket, nil
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}
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// Generates a response to an NDP discovery packet. This is effectively called
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// when the host operating system generates an NDP request for any address in
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// the fd00::/8 range, so that the operating system knows to route that traffic
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// to the Yggdrasil TAP adapter.
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func (i *ICMPv6) HandleNDP(in []byte) ([]byte, error) {
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// Ignore NDP requests for anything outside of fd00::/8
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var source address.Address
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copy(source[:], in[8:])
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var snet address.Subnet
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copy(snet[:], in[8:])
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switch {
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case source.IsValid():
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case snet.IsValid():
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default:
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return nil, errors.New("Not an NDP for 0200::/7")
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}
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// Create our NDP message body response
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body := make([]byte, 28)
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binary.BigEndian.PutUint32(body[:4], uint32(0x20000000))
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copy(body[4:20], in[8:24]) // Target address
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body[20] = uint8(2)
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body[21] = uint8(1)
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copy(body[22:28], i.mymac[:6])
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// Send it back
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return body, nil
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}
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