Merge pull request #14 from neilalexander/icmpv6

Replace ndp.go with icmpv6.go

src/yggdrasil/icmpv6.go

@@ -0,0 +1,226 @@
+package yggdrasil
+
+// The NDP functions are needed when you are running with a
+// TAP adapter - as the operating system expects neighbor solicitations
+// for on-link traffic, this goroutine provides them
+
+import "net"
+import "golang.org/x/net/ipv6"
+import "golang.org/x/net/icmp"
+import "encoding/binary"
+
+type macAddress [6]byte
+
+const ETHER = 14
+
+type icmpv6 struct {
+	tun        *tunDevice
+	peermac    macAddress
+	peerlladdr net.IP
+	mylladdr   net.IP
+	mymac      macAddress
+}
+
+// Marshal returns the binary encoding of h.
+func ipv6Header_Marshal(h *ipv6.Header) ([]byte, error) {
+	b := make([]byte, 40)
+	b[0] |= byte(h.Version) << 4
+	b[0] |= byte(h.TrafficClass) >> 4
+	b[1] |= byte(h.TrafficClass) << 4
+	b[1] |= byte(h.FlowLabel >> 16)
+	b[2] = byte(h.FlowLabel >> 8)
+	b[3] = byte(h.FlowLabel)
+	binary.BigEndian.PutUint16(b[4:6], uint16(h.PayloadLen))
+	b[6] = byte(h.NextHeader)
+	b[7] = byte(h.HopLimit)
+	copy(b[8:24], h.Src)
+	copy(b[24:40], h.Dst)
+	return b, nil
+}
+
+func (i *icmpv6) init(t *tunDevice) {
+	i.tun = t
+
+	// Our MAC address and link-local address
+	copy(i.mymac[:], []byte{
+		0x02, 0x00, 0x00, 0x00, 0x00, 0x02})
+	i.mylladdr = net.IP{
+		0xFE, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0xFE}
+}
+
+func (i *icmpv6) parse_packet(datain []byte) {
+	var response []byte
+	var err error
+
+	// Parse the frame/packet
+	if i.tun.iface.IsTAP() {
+		response, err = i.parse_packet_tap(datain)
+	} else {
+		response, err = i.parse_packet_tun(datain)
+	}
+
+	if err != nil {
+		return
+	}
+
+	// Write the packet to TUN/TAP
+	i.tun.iface.Write(response)
+}
+
+func (i *icmpv6) parse_packet_tap(datain []byte) ([]byte, error) {
+	// Store the peer MAC address
+	copy(i.peermac[:6], datain[6:12])
+
+	// Ignore non-IPv6 frames
+	if binary.BigEndian.Uint16(datain[12:14]) != uint16(0x86DD) {
+		return nil, nil
+	}
+
+	// Hand over to parse_packet_tun to interpret the IPv6 packet
+	ipv6packet, err := i.parse_packet_tun(datain[ETHER:])
+	if err != nil {
+		return nil, err
+	}
+
+	// Create the response buffer
+	dataout := make([]byte, ETHER+ipv6.HeaderLen+32)
+
+	// Populate the response ethernet headers
+	copy(dataout[:6], datain[6:12])
+	copy(dataout[6:12], i.mymac[:])
+	binary.BigEndian.PutUint16(dataout[12:14], uint16(0x86DD))
+
+	// Copy the returned packet to our response ethernet frame
+	copy(dataout[ETHER:], ipv6packet)
+	return dataout, nil
+}
+
+func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
+	// Parse the IPv6 packet headers
+	ipv6Header, err := ipv6.ParseHeader(datain[:ipv6.HeaderLen])
+	if err != nil {
+		return nil, err
+	}
+
+	// Check if the packet is IPv6
+	if ipv6Header.Version != ipv6.Version {
+		return nil, err
+	}
+
+	// Check if the packet is ICMPv6
+	if ipv6Header.NextHeader != 58 {
+		return nil, err
+	}
+
+	// Store the peer link local address, it will come in useful later
+	copy(i.peerlladdr[:], ipv6Header.Src[:])
+
+	// Parse the ICMPv6 message contents
+	icmpv6Header, err := icmp.ParseMessage(58, datain[ipv6.HeaderLen:])
+	if err != nil {
+		return nil, err
+	}
+
+	// Check for a supported message type
+	switch icmpv6Header.Type {
+	case ipv6.ICMPTypeNeighborSolicitation:
+		{
+			response, err := i.handle_ndp(datain[ipv6.HeaderLen:])
+			if err == nil {
+				// Create our ICMPv6 response
+				responsePacket, err := i.create_icmpv6_tun(ipv6Header.Src, ipv6.ICMPTypeNeighborAdvertisement, 0, response)
+				if err != nil {
+					return nil, err
+				}
+
+				// Fix the checksum because I don't even know why, net/icmp is stupid
+				responsePacket[17] ^= 0x4
+
+				// Send it back
+				return responsePacket, nil
+			} else {
+				return nil, err
+			}
+		}
+	}
+
+	return nil, nil
+}
+
+func (i *icmpv6) create_icmpv6_tap(dstmac macAddress, dst net.IP, mtype ipv6.ICMPType, mcode int, mbody []byte) ([]byte, error) {
+	// Pass through to create_icmpv6_tun
+	ipv6packet, err := i.create_icmpv6_tun(dst, mtype, mcode, mbody)
+	if err != nil {
+		return nil, err
+	}
+
+	// Create the response buffer
+	dataout := make([]byte, ETHER+ipv6.HeaderLen+len(mbody))
+
+	// Populate the response ethernet headers
+	copy(dataout[:6], dstmac[:6])
+	copy(dataout[6:12], i.mymac[:])
+	binary.BigEndian.PutUint16(dataout[12:14], uint16(0x86DD))
+
+	// Copy the returned packet to our response ethernet frame
+	copy(dataout[ETHER:], ipv6packet)
+	return dataout, nil
+}
+
+func (i *icmpv6) create_icmpv6_tun(dst net.IP, mtype ipv6.ICMPType, mcode int, mbody []byte) ([]byte, error) {
+	// Create the IPv6 header
+	ipv6Header := ipv6.Header{
+		Version:    ipv6.Version,
+		NextHeader: 58,
+		PayloadLen: len(mbody),
+		HopLimit:   255,
+		Src:        i.mylladdr,
+		Dst:        dst,
+	}
+
+	// Create the ICMPv6 message
+	icmpMessage := icmp.Message{
+		Type: mtype,
+		Code: mcode,
+		Body: &icmp.DefaultMessageBody{Data: mbody},
+	}
+
+	// Convert the IPv6 header into []byte
+	ipv6HeaderBuf, err := ipv6Header_Marshal(&ipv6Header)
+	if err != nil {
+		return nil, err
+	}
+
+	// Convert the ICMPv6 message into []byte
+	icmpMessageBuf, err := icmpMessage.Marshal(icmp.IPv6PseudoHeader(ipv6Header.Dst, ipv6Header.Src))
+	if err != nil {
+		return nil, err
+	}
+
+	// Construct the packet
+	responsePacket := make([]byte, ipv6.HeaderLen+ipv6Header.PayloadLen)
+	copy(responsePacket[:ipv6.HeaderLen], ipv6HeaderBuf)
+	copy(responsePacket[ipv6.HeaderLen:], icmpMessageBuf)
+
+	// Send it back
+	return responsePacket, nil
+}
+
+func (i *icmpv6) handle_ndp(in []byte) ([]byte, error) {
+	// Ignore NDP requests for anything outside of fd00::/8
+	if in[8] != 0xFD {
+		return nil, nil
+	}
+
+	// Create our NDP message body response
+	body := make([]byte, 32)
+	binary.BigEndian.PutUint32(body[:4], uint32(0x20000000))
+	copy(body[4:20], in[8:24]) // Target address
+	body[20] = uint8(2)
+	body[21] = uint8(1)
+	copy(body[22:28], i.mymac[:6])
+
+	// Send it back
+	return body, nil
+}

src/yggdrasil/ndp.go

@@ -1,165 +0,0 @@
-package yggdrasil
-
-// The NDP functions are needed when you are running with a
-// TAP adapter - as the operating system expects neighbor solicitations
-// for on-link traffic, this goroutine provides them
-
-import "golang.org/x/net/icmp"
-import "encoding/binary"
-import "unsafe" // TODO investigate if this can be done without resorting to unsafe
-
-type macAddress [6]byte
-type ipv6Address [16]byte
-
-const ETHER = 14
-const IPV6 = 40
-
-type ndp struct {
-	tun        *tunDevice
-	peermac    macAddress
-	peerlladdr ipv6Address
-	mymac      macAddress
-	mylladdr   ipv6Address
-	recv       chan []byte
-}
-
-type etherHeader struct {
-	destination macAddress
-	source      macAddress
-	ethertype   [2]byte
-}
-
-type ipv6Header struct {
-	preamble    [4]byte
-	length      [2]byte
-	nextheader  byte
-	hoplimit    byte
-	source      ipv6Address
-	destination ipv6Address
-}
-
-type icmpv6Header struct {
-	messagetype byte
-	code        byte
-	checksum    uint16
-}
-
-type icmpv6PseudoHeader struct {
-	source      ipv6Address
-	destination ipv6Address
-	length      [4]byte
-	zero        [3]byte
-	nextheader  byte
-}
-
-type icmpv6Packet struct {
-	ether            etherHeader
-	ipv6             ipv6Header
-	icmpv6           icmpv6Header
-	flags            [4]byte
-	targetaddress    ipv6Address
-	optiontype       byte
-	optionlength     byte
-	linklayeraddress macAddress
-}
-
-func (n *ndp) init(t *tunDevice) {
-	n.tun = t
-	n.recv = make(chan []byte)
-	copy(n.mymac[:], []byte{0x02, 0x00, 0x00, 0x00, 0x00, 0x02})
-	copy(n.mylladdr[:], []byte{
-		0xFE, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80, 0xFE})
-	go n.listen()
-}
-
-func (n *ndp) listen() {
-	for {
-		// Receive from the channel and check if we're using TAP instead
-		// of TUN mode - NDP is only relevant for TAP
-		datain := <-n.recv
-		if !n.tun.iface.IsTAP() {
-			continue
-		}
-
-		// Create our return frame buffer and also the unsafe pointers to
-		// map them to the structs
-		dataout := make([]byte, ETHER+IPV6+32)
-		in := (*icmpv6Packet)(unsafe.Pointer(&datain[0]))
-		out := (*icmpv6Packet)(unsafe.Pointer(&dataout[0]))
-
-		// Store peer MAC address and link-local IP address -
-		// these will be used later by tun.go
-		copy(n.peermac[:6], in.ether.source[:6])
-		copy(n.peerlladdr[:16], in.ipv6.source[:16])
-
-		// Ignore non-IPv6 packets
-		if binary.BigEndian.Uint16(in.ether.ethertype[:]) != uint16(0x86DD) {
-			continue
-		}
-
-		// Ignore non-ICMPv6 packets
-		if in.ipv6.nextheader != uint8(0x3A) {
-			continue
-		}
-
-		// Ignore non-NDP Solicitation packets
-		if in.icmpv6.messagetype != uint8(135) {
-			continue
-		}
-
-		// Ignore NDP requests for anything outside of fd00::/8
-		if in.targetaddress[0] != 0xFD {
-			continue
-		}
-
-		// Populate the out ethernet headers
-		copy(out.ether.destination[:], in.ether.destination[:])
-		copy(out.ether.source[:], n.mymac[:])
-		binary.BigEndian.PutUint16(out.ether.ethertype[:], uint16(0x86DD))
-
-		// And for now just copy the rest of the packet we were sent
-		copy(dataout[ETHER:ETHER+IPV6], datain[ETHER:ETHER+IPV6])
-
-		// Update the source and destination addresses in the IPv6 header
-		copy(out.ipv6.destination[:], in.ipv6.source[:])
-		copy(out.ipv6.source[:], n.mylladdr[:])
-		binary.BigEndian.PutUint16(out.ipv6.length[:], uint16(32))
-
-		// Copy the payload
-		copy(dataout[ETHER+IPV6:], datain[ETHER+IPV6:])
-
-		// Update the ICMPv6 headers
-		out.icmpv6.messagetype = uint8(136)
-		out.icmpv6.code = uint8(0)
-
-		// Update the ICMPv6 payload
-		copy(out.targetaddress[:], in.targetaddress[:])
-		out.optiontype = uint8(2)
-		out.optionlength = uint8(1)
-		copy(out.linklayeraddress[:], n.mymac[:])
-		binary.BigEndian.PutUint32(out.flags[:], uint32(0x20000000))
-
-		// Generate the pseudo-header for the checksum
-		ps := make([]byte, 44)
-		pseudo := (*icmpv6PseudoHeader)(unsafe.Pointer(&ps[0]))
-		copy(pseudo.destination[:], out.ipv6.destination[:])
-		copy(pseudo.source[:], out.ipv6.source[:])
-		binary.BigEndian.PutUint32(pseudo.length[:], uint32(binary.BigEndian.Uint16(out.ipv6.length[:])))
-		pseudo.nextheader = out.ipv6.nextheader
-
-		// Lazy-man's checksum using the icmp library
-		icmpv6, err := icmp.ParseMessage(0x3A, dataout[ETHER+IPV6:])
-		if err != nil {
-			continue
-		}
-		payload, err := icmpv6.Marshal(ps)
-		if err != nil {
-			continue
-		}
-		copy(dataout[ETHER+IPV6:], payload)
-
-		// Send the frame back to the TAP adapter
-		n.tun.iface.Write(dataout)
-	}
-}

src/yggdrasil/tun.go

@@ -18,7 +18,7 @@ type tunInterface interface {
 
 type tunDevice struct {
 	core   *Core
-	ndp   ndp
+	icmpv6 icmpv6
 	send   chan<- []byte
 	recv   <-chan []byte
 	mtu    int
@@ -27,7 +27,7 @@ type tunDevice struct {
 
 func (tun *tunDevice) init(core *Core) {
 	tun.core = core
-	tun.ndp.init(tun)
+	tun.icmpv6.init(tun)
 }
 
 func (tun *tunDevice) write() error {
@@ -36,8 +36,8 @@ func (tun *tunDevice) write() error {
 		if tun.iface.IsTAP() {
 			var frame ethernet.Frame
 			frame.Prepare(
-				tun.ndp.peermac[:6], // Destination MAC address
+				tun.icmpv6.peermac[:6], // Destination MAC address
-				tun.ndp.mymac[:6],   // Source MAC address
+				tun.icmpv6.mymac[:6],   // Source MAC address
 				ethernet.NotTagged,     // VLAN tagging
 				ethernet.IPv6,          // Ethertype
 				len(data))              // Payload length
@@ -68,9 +68,6 @@ func (tun *tunDevice) read() error {
 		o := 0
 		if tun.iface.IsTAP() {
 			o = ETHER_HEADER_LENGTH
-			b := make([]byte, n)
-			copy(b, buf)
-			tun.ndp.recv <- b
 		}
 		if buf[o]&0xf0 != 0x60 ||
 			n != 256*int(buf[o+4])+int(buf[o+5])+IPv6_HEADER_LENGTH+o {
@@ -78,6 +75,13 @@ func (tun *tunDevice) read() error {
 			//panic("Should not happen in testing")
 			continue
 		}
+		if buf[o+6] == 58 {
+			// Found an ICMPv6 packet
+			b := make([]byte, n)
+			copy(b, buf)
+			// tun.icmpv6.recv <- b
+			go tun.icmpv6.parse_packet(b)
+		}
 		packet := append(util_getBytes(), buf[o:n]...)
 		tun.send <- packet
 	}