tuntest: split out testing package

This code is useful to other packages writing tests.

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

2 files changed, 155 insertions, 141 deletions

diff --git a/device/device_test.go b/device/device_test.go
index 14cc605..87ecfc8 100644
--- a/device/device_test.go
+++ b/device/device_test.go
@@ -8,15 +8,12 @@ package device
 import (
 	"bufio"
 	"bytes"
-	"encoding/binary"
-	"io"
 	"net"
-	"os"
 	"strings"
 	"testing"
 	"time"
 
-	"golang.zx2c4.com/wireguard/tun"
+	"golang.zx2c4.com/wireguard/tun/tuntest"
 )
 
 func TestTwoDevicePing(t *testing.T) {
@@ -29,7 +26,7 @@ protocol_version=1
 replace_allowed_ips=true
 allowed_ip=1.0.0.2/32
 endpoint=127.0.0.1:53512`
-	tun1 := NewChannelTUN()
+	tun1 := tuntest.NewChannelTUN()
 	dev1 := NewDevice(tun1.TUN(), NewLogger(LogLevelDebug, "dev1: "))
 	dev1.Up()
 	defer dev1.Close()
@@ -45,7 +42,7 @@ protocol_version=1
 replace_allowed_ips=true
 allowed_ip=1.0.0.1/32
 endpoint=127.0.0.1:53511`
-	tun2 := NewChannelTUN()
+	tun2 := tuntest.NewChannelTUN()
 	dev2 := NewDevice(tun2.TUN(), NewLogger(LogLevelDebug, "dev2: "))
 	dev2.Up()
 	defer dev2.Close()
@@ -54,7 +51,7 @@ endpoint=127.0.0.1:53511`
 	}
 
 	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"))
+		msg2to1 := tuntest.Ping(net.ParseIP("1.0.0.1"), net.ParseIP("1.0.0.2"))
 		tun2.Outbound <- msg2to1
 		select {
 		case msgRecv := <-tun1.Inbound:
@@ -67,7 +64,7 @@ endpoint=127.0.0.1:53511`
 	})
 
 	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"))
+		msg1to2 := tuntest.Ping(net.ParseIP("1.0.0.2"), net.ParseIP("1.0.0.1"))
 		tun1.Outbound <- msg1to2
 		select {
 		case msgRecv := <-tun2.Inbound:
@@ -80,139 +77,6 @@ endpoint=127.0.0.1:53511`
 	})
 }
 
-func ping(dst, src net.IP) []byte {
-	localPort := uint16(1337)
-	seq := uint16(0)
-
-	payload := make([]byte, 4)
-	binary.BigEndian.PutUint16(payload[0:], localPort)
-	binary.BigEndian.PutUint16(payload[2:], seq)
-
-	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)
-}
-
-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
-}
-
-type chTun struct {
-	c *ChannelTUN
-}
-
-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
-	}
-}
-
-// 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
-	}
-	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) {
 	if err != nil {
 		t.Fatal(err)
diff --git a/tun/tuntest/tuntest.go b/tun/tuntest/tuntest.go
new file mode 100644
index 0000000..bdd96ac
--- /dev/null
+++ b/tun/tuntest/tuntest.go
@@ -0,0 +1,150 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2017-2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package tuntest
+
+import (
+	"encoding/binary"
+	"io"
+	"net"
+	"os"
+
+	"golang.zx2c4.com/wireguard/tun"
+)
+
+func Ping(dst, src net.IP) []byte {
+	localPort := uint16(1337)
+	seq := uint16(0)
+
+	payload := make([]byte, 4)
+	binary.BigEndian.PutUint16(payload[0:], localPort)
+	binary.BigEndian.PutUint16(payload[2:], seq)
+
+	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)
+}
+
+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
+}
+
+type chTun struct {
+	c *ChannelTUN
+}
+
+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
+	}
+}
+
+// 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
+	}
+	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
+	}
+}
+
+const DefaultMTU = 1420
+
+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
+}