mirror of
https://github.com/cwinfo/yggdrasil-go.git
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Improve icmpv6.go
- Now doesn't use unsafe - Much cleaner - Doesn't run in a goroutine perpetually - Has a function to create ICMPv6 packets
This commit is contained in:
Neil Alexander
parent
6571a8c300
commit
d78e0f7067
@ -4,219 +4,203 @@ package yggdrasil
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// TAP adapter - as the operating system expects neighbor solicitations
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// for on-link traffic, this goroutine provides them
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import "net"
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import "golang.org/x/net/ipv6"
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import "golang.org/x/net/icmp"
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import "encoding/binary"
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import "unsafe" // TODO investigate if this can be done without resorting to unsafe
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type macAddress [6]byte
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type ipv6Address [16]byte
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const ETHER = 14
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const IPV6 = 40
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type icmpv6 struct {
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tun *tunDevice
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peermac macAddress
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peerlladdr ipv6Address
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peerlladdr net.IP
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mylladdr net.IP
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mymac macAddress
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mylladdr ipv6Address
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}
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type etherHeader struct {
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destination macAddress
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source macAddress
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ethertype [2]byte
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}
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type ipv6Header struct {
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preamble [4]byte
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length [2]byte
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nextheader byte
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hoplimit byte
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source ipv6Address
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destination ipv6Address
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}
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type icmpv6Header struct {
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messagetype byte
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code byte
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checksum uint16
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}
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type icmpv6PseudoHeader struct {
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source ipv6Address
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destination ipv6Address
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length [4]byte
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zero [3]byte
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nextheader byte
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}
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type icmpv6Payload struct {
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ether etherHeader
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ipv6 ipv6Header
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icmpv6 icmpv6Header
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flags [4]byte
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targetaddress ipv6Address
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optiontype byte
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optionlength byte
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linklayeraddress macAddress
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}
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type icmpv6Packet struct {
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ipv6 ipv6Header
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payload icmpv6Payload
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}
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type icmpv6Frame struct {
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ether etherHeader
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packet icmpv6Packet
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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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func (i *icmpv6) init(t *tunDevice) {
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i.tun = t
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copy(i.mymac[:], []byte{0x02, 0x00, 0x00, 0x00, 0x00, 0x02})
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copy(i.mylladdr[:], []byte{
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// Our MAC address and link-local address
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copy(i.mymac[:], []byte{
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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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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0xFE}
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}
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func (i *icmpv6) parse_packet(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.iface.IsTAP() {
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response, err = i.parse_packet_tap(datain)
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} else {
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response, err = i.parse_packet_tun(datain)
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}
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if err != nil {
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i.tun.core.log.Printf("ICMPv6 error: %v", err)
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return
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}
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if response != nil {
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i.tun.iface.Write(response)
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}
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// Write the packet to TUN/TAP
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i.tun.iface.Write(response)
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}
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func (i *icmpv6) parse_packet_tap(datain []byte) ([]byte, error) {
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// Set up
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in := (*icmpv6Frame)(unsafe.Pointer(&datain[0]))
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// Store the peer MAC address
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copy(i.peermac[:6], in.ether.source[:6])
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copy(i.peermac[:6], datain[6:12])
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// Ignore non-IPv6 frames
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if binary.BigEndian.Uint16(in.ether.ethertype[:]) != uint16(0x86DD) {
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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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// Create the response buffer
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dataout := make([]byte, ETHER+IPV6+32)
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out := (*icmpv6Frame)(unsafe.Pointer(&dataout[0]))
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// Populate the response ethernet headers
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copy(out.ether.destination[:], in.ether.destination[:])
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copy(out.ether.source[:], i.mymac[:])
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binary.BigEndian.PutUint16(out.ether.ethertype[:], uint16(0x86DD))
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// Hand over to parse_packet_tun to interpret the IPv6 packet
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ipv6packet, err := i.parse_packet_tun(datain)
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if err != nil {
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return nil, nil
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}
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// Copy the returned packet to our response ethernet frame
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if ipv6packet != nil {
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copy(dataout[ETHER:ETHER+IPV6], ipv6packet)
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return dataout, nil
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}
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// At this point there is no response to send back
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return nil, nil
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}
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func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
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// Set up
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dataout := make([]byte, IPV6+32)
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out := (*icmpv6Packet)(unsafe.Pointer(&dataout[0]))
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in := (*icmpv6Packet)(unsafe.Pointer(&datain[0]))
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// Store the peer link-local address
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copy(i.peerlladdr[:16], in.ipv6.source[:16])
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// Ignore non-ICMPv6 packets
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if in.ipv6.nextheader != uint8(0x3A) {
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return nil, nil
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}
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// What is the ICMPv6 message type?
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switch in.payload.icmpv6.messagetype {
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case uint8(135):
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i.handle_ndp(&in.payload, &out.payload)
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break
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}
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// Update the source and destination addresses in the IPv6 header
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copy(out.ipv6.destination[:], in.ipv6.source[:])
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copy(out.ipv6.source[:], i.mylladdr[:])
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binary.BigEndian.PutUint16(out.ipv6.length[:], uint16(32))
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// Copy the payload
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copy(dataout[IPV6:], datain[IPV6:])
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// Calculate the checksum
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err := i.calculate_checksum(dataout)
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ipv6packet, err := i.parse_packet_tun(datain[ETHER:])
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if err != nil {
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return nil, err
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}
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// Return the response packet
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// Create the response buffer
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dataout := make([]byte, 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[ETHER:], ipv6packet)
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return dataout, nil
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}
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func (i *icmpv6) calculate_checksum(dataout []byte) (error) {
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// Set up
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out := (*icmpv6Packet)(unsafe.Pointer(&dataout[0]))
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// Generate the pseudo-header for the checksum
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ps := make([]byte, 44)
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pseudo := (*icmpv6PseudoHeader)(unsafe.Pointer(&ps[0]))
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copy(pseudo.destination[:], out.ipv6.destination[:])
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copy(pseudo.source[:], out.ipv6.source[:])
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binary.BigEndian.PutUint32(pseudo.length[:], uint32(binary.BigEndian.Uint16(out.ipv6.length[:])))
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pseudo.nextheader = out.ipv6.nextheader
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// Lazy-man's checksum using the icmp library
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icmpv6, err := icmp.ParseMessage(0x3A, dataout[IPV6:])
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func (i *icmpv6) parse_packet_tun(datain []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 err
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return nil, err
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}
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// And copy the payload
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payload, err := icmpv6.Marshal(ps)
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if err != nil {
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return err
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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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copy(dataout[IPV6:], payload)
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// Return nil if successful
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return nil
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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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// Store the peer link local address, it will come in useful later
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copy(i.peerlladdr[:], ipv6Header.Src[:])
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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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{
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response, err := i.handle_ndp(datain[ipv6.HeaderLen:])
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if err == nil {
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// Create our ICMPv6 response
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responsePacket, err := i.create_icmpv6(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0, response)
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if err != nil {
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return nil, err
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}
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// Fix the checksum because I don't even know why, net/icmp is stupid
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responsePacket[17] ^= 0x4
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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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}
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}
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return nil, nil
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}
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func (i *icmpv6) handle_ndp(in *icmpv6Payload, out *icmpv6Payload) {
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func (i *icmpv6) create_icmpv6(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody []byte) ([]byte, error) {
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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(mbody),
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HopLimit: 255,
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Src: i.mylladdr,
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Dst: dst,
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}
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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: &icmp.DefaultMessageBody{Data: mbody},
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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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// Convert the ICMPv6 message into []byte
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icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(ipv6Header.Dst, ipv6Header.Src))
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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) handle_ndp(in []byte) ([]byte, error) {
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// Ignore NDP requests for anything outside of fd00::/8
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if in.targetaddress[0] != 0xFD {
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return
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if in[8] != 0xFD {
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return nil, nil
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}
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// Update the ICMPv6 headers
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out.icmpv6.messagetype = uint8(136)
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out.icmpv6.code = uint8(0)
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// Create our NDP message body response
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body := make([]byte, 32)
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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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// Update the ICMPv6 payload
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copy(out.targetaddress[:], in.targetaddress[:])
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out.optiontype = uint8(2)
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out.optionlength = uint8(1)
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copy(out.linklayeraddress[:], i.mymac[:])
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binary.BigEndian.PutUint32(out.flags[:], uint32(0x20000000))
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// Send it back
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return body, nil
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}
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@ -80,11 +80,7 @@ func (tun *tunDevice) read() error {
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b := make([]byte, n)
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copy(b, buf)
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// tun.icmpv6.recv <- b
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if tun.iface.IsTAP() {
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go tun.icmpv6.parse_packet_tap(b)
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} else {
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go tun.icmpv6.parse_packet_tun(b)
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}
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go tun.icmpv6.parse_packet(b)
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}
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packet := append(util_getBytes(), buf[o:n]...)
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tun.send <- packet
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