device: test packets between two fake devices

Signed-off-by: David Crawshaw <crawshaw@tailscale.io>

1 files changed, 199 insertions, 29 deletions

diff --git a/device/device_test.go b/device/device_test.go
index cdbd458..14cc605 100644
--- a/device/device_test.go
+++ b/device/device_test.go
@@ -5,54 +5,212 @@
 
 package device
 
-/* Create two device instances and simulate full WireGuard interaction
- * without network dependencies
- */
-
 import (
+	"bufio"
 	"bytes"
+	"encoding/binary"
+	"io"
+	"net"
+	"os"
+	"strings"
 	"testing"
+	"time"
+
+	"golang.zx2c4.com/wireguard/tun"
 )
 
-func TestDevice(t *testing.T) {
+func TestTwoDevicePing(t *testing.T) {
+	// TODO(crawshaw): pick unused ports on localhost
+	cfg1 := `private_key=481eb0d8113a4a5da532d2c3e9c14b53c8454b34ab109676f6b58c2245e37b58
+listen_port=53511
+replace_peers=true
+public_key=f70dbb6b1b92a1dde1c783b297016af3f572fef13b0abb16a2623d89a58e9725
+protocol_version=1
+replace_allowed_ips=true
+allowed_ip=1.0.0.2/32
+endpoint=127.0.0.1:53512`
+	tun1 := NewChannelTUN()
+	dev1 := NewDevice(tun1.TUN(), NewLogger(LogLevelDebug, "dev1: "))
+	dev1.Up()
+	defer dev1.Close()
+	if err := dev1.IpcSetOperation(bufio.NewReader(strings.NewReader(cfg1))); err != nil {
+		t.Fatal(err)
+	}
 
-	// prepare tun devices for generating traffic
+	cfg2 := `private_key=98c7989b1661a0d64fd6af3502000f87716b7c4bbcf00d04fc6073aa7b539768
+listen_port=53512
+replace_peers=true
+public_key=49e80929259cebdda4f322d6d2b1a6fad819d603acd26fd5d845e7a123036427
+protocol_version=1
+replace_allowed_ips=true
+allowed_ip=1.0.0.1/32
+endpoint=127.0.0.1:53511`
+	tun2 := NewChannelTUN()
+	dev2 := NewDevice(tun2.TUN(), NewLogger(LogLevelDebug, "dev2: "))
+	dev2.Up()
+	defer dev2.Close()
+	if err := dev2.IpcSetOperation(bufio.NewReader(strings.NewReader(cfg2))); err != nil {
+		t.Fatal(err)
+	}
 
-	tun1 := newDummyTUN("tun1")
-	tun2 := newDummyTUN("tun2")
+	t.Run("ping 1.0.0.1", func(t *testing.T) {
+		msg2to1 := ping(net.ParseIP("1.0.0.1"), net.ParseIP("1.0.0.2"))
+		tun2.Outbound <- msg2to1
+		select {
+		case msgRecv := <-tun1.Inbound:
+			if !bytes.Equal(msg2to1, msgRecv) {
+				t.Error("ping did not transit correctly")
+			}
+		case <-time.After(300 * time.Millisecond):
+			t.Error("ping did not transit")
+		}
+	})
+
+	t.Run("ping 1.0.0.2", func(t *testing.T) {
+		msg1to2 := ping(net.ParseIP("1.0.0.2"), net.ParseIP("1.0.0.1"))
+		tun1.Outbound <- msg1to2
+		select {
+		case msgRecv := <-tun2.Inbound:
+			if !bytes.Equal(msg1to2, msgRecv) {
+				t.Error("return ping did not transit correctly")
+			}
+		case <-time.After(300 * time.Millisecond):
+			t.Error("return ping did not transit")
+		}
+	})
+}
 
-	_ = tun1
-	_ = tun2
+func ping(dst, src net.IP) []byte {
+	localPort := uint16(1337)
+	seq := uint16(0)
 
-	// prepare endpoints
+	payload := make([]byte, 4)
+	binary.BigEndian.PutUint16(payload[0:], localPort)
+	binary.BigEndian.PutUint16(payload[2:], seq)
 
-	end1, err := CreateDummyEndpoint()
-	if err != nil {
-		t.Error("failed to create endpoint:", err.Error())
+	return genICMPv4(payload, dst, src)
+}
+
+// checksum is the "internet checksum" from https://tools.ietf.org/html/rfc1071.
+func checksum(buf []byte, initial uint16) uint16 {
+	v := uint32(initial)
+	for i := 0; i < len(buf)-1; i += 2 {
+		v += uint32(binary.BigEndian.Uint16(buf[i:]))
+	}
+	if len(buf)%2 == 1 {
+		v += uint32(buf[len(buf)-1]) << 8
+	}
+	for v > 0xffff {
+		v = (v >> 16) + (v & 0xffff)
 	}
+	return ^uint16(v)
+}
 
-	end2, err := CreateDummyEndpoint()
-	if err != nil {
-		t.Error("failed to create endpoint:", err.Error())
+func genICMPv4(payload []byte, dst, src net.IP) []byte {
+	const (
+		icmpv4ProtocolNumber = 1
+		icmpv4Echo           = 8
+		icmpv4ChecksumOffset = 2
+		icmpv4Size           = 8
+		ipv4Size             = 20
+		ipv4TotalLenOffset   = 2
+		ipv4ChecksumOffset   = 10
+		ttl                  = 65
+	)
+
+	hdr := make([]byte, ipv4Size+icmpv4Size)
+
+	ip := hdr[0:ipv4Size]
+	icmpv4 := hdr[ipv4Size : ipv4Size+icmpv4Size]
+
+	// https://tools.ietf.org/html/rfc792
+	icmpv4[0] = icmpv4Echo // type
+	icmpv4[1] = 0          // code
+	chksum := ^checksum(icmpv4, checksum(payload, 0))
+	binary.BigEndian.PutUint16(icmpv4[icmpv4ChecksumOffset:], chksum)
+
+	// https://tools.ietf.org/html/rfc760 section 3.1
+	length := uint16(len(hdr) + len(payload))
+	ip[0] = (4 << 4) | (ipv4Size / 4)
+	binary.BigEndian.PutUint16(ip[ipv4TotalLenOffset:], length)
+	ip[8] = ttl
+	ip[9] = icmpv4ProtocolNumber
+	copy(ip[12:], src.To4())
+	copy(ip[16:], dst.To4())
+	chksum = ^checksum(ip[:], 0)
+	binary.BigEndian.PutUint16(ip[ipv4ChecksumOffset:], chksum)
+
+	var v []byte
+	v = append(v, hdr...)
+	v = append(v, payload...)
+	return []byte(v)
+}
+
+// TODO(crawshaw): find a reusable home for this. package devicetest?
+type ChannelTUN struct {
+	Inbound  chan []byte // incoming packets, closed on TUN close
+	Outbound chan []byte // outbound packets, blocks forever on TUN close
+
+	closed chan struct{}
+	events chan tun.Event
+	tun    chTun
+}
+
+func NewChannelTUN() *ChannelTUN {
+	c := &ChannelTUN{
+		Inbound:  make(chan []byte),
+		Outbound: make(chan []byte),
+		closed:   make(chan struct{}),
+		events:   make(chan tun.Event, 1),
 	}
+	c.tun.c = c
+	c.events <- tun.EventUp
+	return c
+}
+
+func (c *ChannelTUN) TUN() tun.Device {
+	return &c.tun
+}
 
-	_ = end1
-	_ = end2
+type chTun struct {
+	c *ChannelTUN
+}
 
-	// create binds
+func (t *chTun) File() *os.File { return nil }
 
+func (t *chTun) Read(data []byte, offset int) (int, error) {
+	select {
+	case <-t.c.closed:
+		return 0, io.EOF // TODO(crawshaw): what is the correct error value?
+	case msg := <-t.c.Outbound:
+		return copy(data[offset:], msg), nil
+	}
 }
 
-func randDevice(t *testing.T) *Device {
-	sk, err := newPrivateKey()
-	if err != nil {
-		t.Fatal(err)
+// Write is called by the wireguard device to deliver a packet for routing.
+func (t *chTun) Write(data []byte, offset int) (int, error) {
+	if offset == -1 {
+		close(t.c.closed)
+		close(t.c.events)
+		return 0, io.EOF
 	}
-	tun := newDummyTUN("dummy")
-	logger := NewLogger(LogLevelError, "")
-	device := NewDevice(tun, logger)
-	device.SetPrivateKey(sk)
-	return device
+	msg := make([]byte, len(data)-offset)
+	copy(msg, data[offset:])
+	select {
+	case <-t.c.closed:
+		return 0, io.EOF // TODO(crawshaw): what is the correct error value?
+	case t.c.Inbound <- msg:
+		return len(data) - offset, nil
+	}
+}
+
+func (t *chTun) Flush() error           { return nil }
+func (t *chTun) MTU() (int, error)      { return DefaultMTU, nil }
+func (t *chTun) Name() (string, error)  { return "loopbackTun1", nil }
+func (t *chTun) Events() chan tun.Event { return t.c.events }
+func (t *chTun) Close() error {
+	t.Write(nil, -1)
+	return nil
 }
 
 func assertNil(t *testing.T, err error) {
@@ -66,3 +224,15 @@ func assertEqual(t *testing.T, a, b []byte) {
 		t.Fatal(a, "!=", b)
 	}
 }
+
+func randDevice(t *testing.T) *Device {
+	sk, err := newPrivateKey()
+	if err != nil {
+		t.Fatal(err)
+	}
+	tun := newDummyTUN("dummy")
+	logger := NewLogger(LogLevelError, "")
+	device := NewDevice(tun, logger)
+	device.SetPrivateKey(sk)
+	return device
+}