Initial proxying implementation

NDPRequest.go

@@ -1,6 +1,15 @@
 package main
 
+type NDPType int
+
+const (
+	NDP_ADV NDPType = 0
+	NDP_SOL NDPType = 1
+)
+
 type NDRequest struct {
+	requestType NDPType
+	//TODO use global unicast for router advertisements
 	srcIP          []byte
 	answeringForIP []byte
 	mac            []byte

main.go

@@ -6,14 +6,53 @@ import (
 )
 
 func main() {
+	fmt.Println("Usage: pndpd respond <interface>")
+	fmt.Println("Usage: pndpd proxy <interface1> <interface2>")
+
 	if len(os.Args) <= 1 {
-		fmt.Println("Specify interface")
+		fmt.Println("Specify command")
 		os.Exit(1)
 	}
-	iface := os.Args[1]
-	requests := make(chan *NDRequest, 100)
-	defer close(requests)
-	go respond(iface, requests)
-	listen(iface, requests)
+	if os.Args[1] == "respond" {
+		simpleRespond(os.Args[2])
+	}
+	if os.Args[1] == "proxy" {
+		proxy(os.Args[2], os.Args[3])
+	}
+
+}
+
+func simpleRespond(iface string) {
+	requests := make(chan *NDRequest, 100)
+	defer close(requests)
+	go respond(iface, requests, NDP_ADV)
+	go listen(iface, requests, NDP_SOL)
+	select {}
+	//TODO os.signal
+}
+
+func proxy(iface1, iface2 string) {
+	req_iface1_sol_iface2 := make(chan *NDRequest, 100)
+	defer close(req_iface1_sol_iface2)
+	go listen(iface1, req_iface1_sol_iface2, NDP_SOL)
+	go respond(iface2, req_iface1_sol_iface2, NDP_SOL)
+
+	req_iface2_sol_iface1 := make(chan *NDRequest, 100)
+	defer close(req_iface2_sol_iface1)
+	go listen(iface2, req_iface2_sol_iface1, NDP_SOL)
+	go respond(iface1, req_iface2_sol_iface1, NDP_SOL)
+
+	req_iface1_adv_iface2 := make(chan *NDRequest, 100)
+	defer close(req_iface1_adv_iface2)
+	go listen(iface1, req_iface1_adv_iface2, NDP_ADV)
+	go respond(iface2, req_iface1_adv_iface2, NDP_ADV)
+
+	req_iface2_adv_iface1 := make(chan *NDRequest, 100)
+	defer close(req_iface2_adv_iface1)
+	go listen(iface2, req_iface2_adv_iface1, NDP_ADV)
+	go respond(iface1, req_iface2_adv_iface1, NDP_ADV)
+
+	select {}
+	// TODO os.signal
 
 }

packet.go

@@ -55,25 +55,36 @@ func (h *IPv6Header) constructPacket() []byte {
 	return final
 }
 
-type NDPAdvPayload struct {
+type NdpPayload struct {
+	packetType     NDPType
 	answeringForIP []byte
 	mac            []byte
 }
 
-func newNdpPacket(answeringForIP []byte, mac []byte) *NDPAdvPayload {
-	return &NDPAdvPayload{
+func newNdpPacket(answeringForIP []byte, mac []byte, packetType NDPType) *NdpPayload {
+	return &NdpPayload{
+		packetType:     packetType,
 		answeringForIP: answeringForIP,
 		mac:            mac,
 	}
 }
 
-func (p *NDPAdvPayload) constructPacket() ([]byte, int) {
+func (p *NdpPayload) constructPacket() ([]byte, int) {
+	var protocol byte
+	var flags byte
+	if p.packetType == NDP_SOL {
+		protocol = 0x87
+		flags = 0x0
+	} else {
+		protocol = 0x88
+		flags = 0x60
+	}
 	header := []byte{
-		0x88, // Type: Neighbor Advertisement
+		protocol, // Type: NDPType
 		0x0,      // Code
 		0x0,      // Checksum filled in later
 		0x0,      // Checksum filled in later
-		0x60, // Flags (Solicited,Override)
+		flags,    // Flags (Solicited,Override)
 		0x0,      // Reserved
 		0x0,      // Reserved
 		0x0,      // Reserved

rawsocket.go

@@ -40,7 +40,7 @@ func htons(v uint16) int {
 }
 func htons16(v uint16) uint16 { return v<<8 | v>>8 }
 
-func listen(iface string, responder chan *NDRequest) {
+func listen(iface string, responder chan *NDRequest, requestType NDPType) {
 
 	niface, err := net.InterfaceByName(iface)
 	if err != nil {
@@ -68,7 +68,9 @@ func listen(iface string, responder chan *NDRequest) {
 		fmt.Println(err.Error())
 	}
 
-	var f Filter = []bpf.Instruction{
+	var f Filter
+	if requestType == NDP_SOL {
+		f = []bpf.Instruction{
 			// Load "EtherType" field from the ethernet header.
 			bpf.LoadAbsolute{Off: 12, Size: 2},
 			// Jump to the drop packet instruction if EtherType is not IPv6.
@@ -86,6 +88,26 @@ func listen(iface string, responder chan *NDRequest) {
 			// Verdict is "ignore packet."
 			bpf.RetConstant{Val: 0},
 		}
+	} else {
+		f = []bpf.Instruction{
+			// Load "EtherType" field from the ethernet header.
+			bpf.LoadAbsolute{Off: 12, Size: 2},
+			// Jump to the drop packet instruction if EtherType is not IPv6.
+			bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x86dd, SkipTrue: 4},
+			// Load "Next Header" field from IPV6 header.
+			bpf.LoadAbsolute{Off: 20, Size: 1},
+			// Jump to the drop packet instruction if Next Header is not ICMPv6.
+			bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x3a, SkipTrue: 2},
+			// Load "Type" field from ICMPv6 header.
+			bpf.LoadAbsolute{Off: 54, Size: 1},
+			// Jump to the drop packet instruction if Type is not Neighbor Advertisement.
+			bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x88, SkipTrue: 1},
+			// Verdict is "send up to 4k of the packet to userspace."
+			bpf.RetConstant{Val: 4096},
+			// Verdict is "ignore packet."
+			bpf.RetConstant{Val: 0},
+		}
+	}
 
 	err = f.ApplyTo(fd)
 	if err != nil {
@@ -106,9 +128,10 @@ func listen(iface string, responder chan *NDRequest) {
 		fmt.Printf("% X\n", buf[:numRead][80:86])
 		fmt.Println()
 		responder <- &NDRequest{
+			requestType:    requestType,
 			srcIP:          buf[:numRead][22:38],
 			answeringForIP: buf[:numRead][62:78],
-			mac:            niface.HardwareAddr,
+			mac:            buf[:numRead][80:86],
 		}
 	}
 }

responder.go

@@ -1,29 +1,40 @@
 package main
 
 import (
+	"net"
 	"syscall"
 )
 
 var fd int
 
-func respond(iface string, requests chan *NDRequest) {
+func respond(iface string, requests chan *NDRequest, respondType NDPType) {
 	fd, _ = syscall.Socket(syscall.AF_INET6, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
 	syscall.BindToDevice(fd, iface)
 
+	niface, err := net.InterfaceByName(iface)
+	if err != nil {
+		panic(err.Error())
+	}
+
 	for {
 		n := <-requests
-		pkt(n.srcIP, n.answeringForIP, n.mac)
+		pkt(n.srcIP, n.answeringForIP, niface.HardwareAddr, respondType)
 	}
 }
 
-func pkt(srcip []byte, tgtip []byte, mac []byte) {
+func pkt(srcip []byte, tgtip []byte, mac []byte, respondType NDPType) {
 	v6 := newIpv6Header(emptyIpv6, srcip)
-	NDPa := newNdpPacket(tgtip, mac)
+	NDPa := newNdpPacket(tgtip, mac, respondType)
 	v6.addPayload(NDPa)
 	response := v6.constructPacket()
 
 	var t [16]byte
+	if respondType == NDP_SOL {
+		copy(t[:], []byte{0xff, 0x02, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x02})
+	} else {
 		copy(t[:], srcip)
+	}
+
 	d := syscall.SockaddrInet6{
 		Port: 0,
 		Addr: t,