Merge pull request #204 from neilalexander/tapmac

Neighbor discovery changes for TAP mode

src/yggdrasil/icmpv6.go

@@ -13,6 +13,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"net"
+	"time"
 
 	"golang.org/x/net/icmp"
 	"golang.org/x/net/ipv6"
@@ -24,10 +25,16 @@ const len_ETHER = 14
 
 type icmpv6 struct {
 	tun      *tunDevice
-	peermac    macAddress
-	peerlladdr net.IP
 	mylladdr net.IP
 	mymac    macAddress
+	peermacs map[address]neighbor
+}
+
+type neighbor struct {
+	mac               macAddress
+	learned           bool
+	lastadvertisement time.Time
+	lastsolicitation  time.Time
 }
 
 // Marshal returns the binary encoding of h.
@@ -52,13 +59,16 @@ func ipv6Header_Marshal(h *ipv6.Header) ([]byte, error) {
 // addresses.
 func (i *icmpv6) init(t *tunDevice) {
 	i.tun = t
+	i.peermacs = make(map[address]neighbor)
 
 	// Our MAC address and link-local address
-	copy(i.mymac[:], []byte{
+	i.mymac = macAddress{
-		0x02, 0x00, 0x00, 0x00, 0x00, 0x02})
+		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}
+	copy(i.mymac[:], i.tun.core.router.addr[:])
+	copy(i.mylladdr[9:], i.tun.core.router.addr[1:])
 }
 
 // Parses an incoming ICMPv6 packet. The packet provided may be either an
@@ -73,7 +83,7 @@ func (i *icmpv6) parse_packet(datain []byte) {
 	if i.tun.iface.IsTAP() {
 		response, err = i.parse_packet_tap(datain)
 	} else {
-		response, err = i.parse_packet_tun(datain)
+		response, err = i.parse_packet_tun(datain, nil)
 	}
 
 	if err != nil {
@@ -89,16 +99,14 @@ func (i *icmpv6) parse_packet(datain []byte) {
 // A response buffer is also created for the response message, also complete
 // with ethernet headers.
 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[len_ETHER:])
+	mac := datain[6:12]
+	ipv6packet, err := i.parse_packet_tun(datain[len_ETHER:], &mac)
 	if err != nil {
 		return nil, err
 	}
@@ -120,7 +128,7 @@ func (i *icmpv6) parse_packet_tap(datain []byte) ([]byte, error) {
 // sanity checks on the packet - i.e. is the packet an ICMPv6 packet, does the
 // ICMPv6 message match a known expected type. The relevant handler function
 // is then called and a response packet may be returned.
-func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
+func (i *icmpv6) parse_packet_tun(datain []byte, datamac *[]byte) ([]byte, error) {
 	// Parse the IPv6 packet headers
 	ipv6Header, err := ipv6.ParseHeader(datain[:ipv6.HeaderLen])
 	if err != nil {
@@ -137,9 +145,6 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 		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 {
@@ -149,7 +154,6 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 	// 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
@@ -166,7 +170,19 @@ func (i *icmpv6) parse_packet_tun(datain []byte) ([]byte, error) {
 		} else {
 			return nil, err
 		}
+	case ipv6.ICMPTypeNeighborAdvertisement:
+		if datamac != nil {
+			var addr address
+			var mac macAddress
+			copy(addr[:], ipv6Header.Src[:])
+			copy(mac[:], (*datamac)[:])
+			neighbor := i.peermacs[addr]
+			neighbor.mac = mac
+			neighbor.learned = true
+			neighbor.lastadvertisement = time.Now()
+			i.peermacs[addr] = neighbor
 		}
+		return nil, errors.New("No response needed")
 	}
 
 	return nil, errors.New("ICMPv6 type not matched")
@@ -238,6 +254,42 @@ func (i *icmpv6) create_icmpv6_tun(dst net.IP, src net.IP, mtype ipv6.ICMPType,
 	return responsePacket, nil
 }
 
+func (i *icmpv6) create_ndp_tap(dst address) ([]byte, error) {
+	// Create the ND payload
+	var payload [28]byte
+	copy(payload[:4], []byte{0x00, 0x00, 0x00, 0x00})
+	copy(payload[4:20], dst[:])
+	copy(payload[20:22], []byte{0x01, 0x01})
+	copy(payload[22:28], i.mymac[:6])
+
+	// Create the ICMPv6 solicited-node address
+	var dstaddr address
+	copy(dstaddr[:13], []byte{
+		0xFF, 0x02, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x01, 0xFF})
+	copy(dstaddr[13:], dst[13:16])
+
+	// Create the multicast MAC
+	var dstmac macAddress
+	copy(dstmac[:2], []byte{0x33, 0x33})
+	copy(dstmac[2:6], dstaddr[12:16])
+
+	// Create the ND request
+	requestPacket, err := i.create_icmpv6_tap(
+		dstmac, dstaddr[:], i.mylladdr,
+		ipv6.ICMPTypeNeighborSolicitation, 0,
+		&icmp.DefaultMessageBody{Data: payload[:]})
+	if err != nil {
+		return nil, err
+	}
+	neighbor := i.peermacs[dstaddr]
+	neighbor.lastsolicitation = time.Now()
+	i.peermacs[dstaddr] = neighbor
+
+	return requestPacket, nil
+}
+
 // Generates a response to an NDP discovery packet. This is effectively called
 // when the host operating system generates an NDP request for any address in
 // the fd00::/8 range, so that the operating system knows to route that traffic

src/yggdrasil/tun.go

@@ -3,6 +3,9 @@ package yggdrasil
 // This manages the tun driver to send/recv packets to/from applications
 
 import (
+	"bytes"
+	"errors"
+	"time"
 	"yggdrasil/defaults"
 
 	"github.com/songgao/packets/ethernet"
@@ -48,6 +51,21 @@ func (tun *tunDevice) start(ifname string, iftapmode bool, addr string, mtu int)
 	}
 	go func() { panic(tun.read()) }()
 	go func() { panic(tun.write()) }()
+	go func() {
+		for {
+			if _, ok := tun.icmpv6.peermacs[tun.core.router.addr]; ok {
+				break
+			}
+			request, err := tun.icmpv6.create_ndp_tap(tun.core.router.addr)
+			if err != nil {
+				panic(err)
+			}
+			if _, err := tun.iface.Write(request); err != nil {
+				panic(err)
+			}
+			time.Sleep(time.Second)
+		}
+	}()
 	return nil
 }
 
@@ -61,17 +79,75 @@ func (tun *tunDevice) write() error {
 			continue
 		}
 		if tun.iface.IsTAP() {
+			var destAddr address
+			if data[0]&0xf0 == 0x60 {
+				if len(data) < 40 {
+					panic("Tried to send a packet shorter than an IPv6 header...")
+				}
+				copy(destAddr[:16], data[24:])
+			} else if data[0]&0xf0 == 0x40 {
+				if len(data) < 20 {
+					panic("Tried to send a packet shorter than an IPv4 header...")
+				}
+				copy(destAddr[:4], data[16:])
+			} else {
+				return errors.New("Invalid address family")
+			}
+			sendndp := func(destAddr address) {
+				neigh, known := tun.icmpv6.peermacs[destAddr]
+				known = known && (time.Since(neigh.lastsolicitation).Seconds() < 30)
+				if !known {
+					request, err := tun.icmpv6.create_ndp_tap(destAddr)
+					if err != nil {
+						panic(err)
+					}
+					if _, err := tun.iface.Write(request); err != nil {
+						panic(err)
+					}
+					tun.icmpv6.peermacs[destAddr] = neighbor{
+						lastsolicitation: time.Now(),
+					}
+				}
+			}
+			var peermac macAddress
+			var peerknown bool
+			if data[0]&0xf0 == 0x40 {
+				destAddr = tun.core.router.addr
+			} else if data[0]&0xf0 == 0x60 {
+				if !bytes.Equal(tun.core.router.addr[:16], destAddr[:16]) && !bytes.Equal(tun.core.router.subnet[:8], destAddr[:8]) {
+					destAddr = tun.core.router.addr
+				}
+			}
+			if neighbor, ok := tun.icmpv6.peermacs[destAddr]; ok && neighbor.learned {
+				peermac = neighbor.mac
+				peerknown = true
+			} else if neighbor, ok := tun.icmpv6.peermacs[tun.core.router.addr]; ok && neighbor.learned {
+				peermac = neighbor.mac
+				peerknown = true
+				sendndp(destAddr)
+			} else {
+				sendndp(tun.core.router.addr)
+			}
+			if peerknown {
+				var proto ethernet.Ethertype
+				switch {
+				case data[0]&0xf0 == 0x60:
+					proto = ethernet.IPv6
+				case data[0]&0xf0 == 0x40:
+					proto = ethernet.IPv4
+				}
 				var frame ethernet.Frame
 				frame.Prepare(
-				tun.icmpv6.peermac[:6], // Destination MAC address
+					peermac[:6],          // Destination MAC address
 					tun.icmpv6.mymac[:6], // Source MAC address
 					ethernet.NotTagged,   // VLAN tagging
-				ethernet.IPv6,          // Ethertype
+					proto,                // Ethertype
 					len(data))            // Payload length
 				copy(frame[tun_ETHER_HEADER_LENGTH:], data[:])
 				if _, err := tun.iface.Write(frame); err != nil {
 					panic(err)
 				}
+			}
 		} else {
 			if _, err := tun.iface.Write(data); err != nil {
 				panic(err)