device: test up/down using virtual conn

This prevents port clashing bugs.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

conn/bindtest/bindtest.go

@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019-2021 WireGuard LLC. All Rights Reserved.
+ */
+
+package bindtest
+
+import (
+	"fmt"
+	"math/rand"
+	"net"
+	"os"
+	"strconv"
+
+	"golang.zx2c4.com/wireguard/conn"
+)
+
+type ChannelBind struct {
+	rx4, tx4         *chan []byte
+	rx6, tx6         *chan []byte
+	closeSignal      chan bool
+	source4, source6 ChannelEndpoint
+	target4, target6 ChannelEndpoint
+}
+
+type ChannelEndpoint uint16
+
+var _ conn.Bind = (*ChannelBind)(nil)
+var _ conn.Endpoint = (*ChannelEndpoint)(nil)
+
+func NewChannelBinds() [2]conn.Bind {
+	arx4 := make(chan []byte, 8192)
+	brx4 := make(chan []byte, 8192)
+	arx6 := make(chan []byte, 8192)
+	brx6 := make(chan []byte, 8192)
+	var binds [2]ChannelBind
+	binds[0].rx4 = &arx4
+	binds[0].tx4 = &brx4
+	binds[1].rx4 = &brx4
+	binds[1].tx4 = &arx4
+	binds[0].rx6 = &arx6
+	binds[0].tx6 = &brx6
+	binds[1].rx6 = &brx6
+	binds[1].tx6 = &arx6
+	binds[0].target4 = ChannelEndpoint(1)
+	binds[1].target4 = ChannelEndpoint(2)
+	binds[0].target6 = ChannelEndpoint(3)
+	binds[1].target6 = ChannelEndpoint(4)
+	binds[0].source4 = binds[1].target4
+	binds[0].source6 = binds[1].target6
+	binds[1].source4 = binds[0].target4
+	binds[1].source6 = binds[0].target6
+	return [2]conn.Bind{&binds[0], &binds[1]}
+}
+
+func (c ChannelEndpoint) ClearSrc() {}
+
+func (c ChannelEndpoint) SrcToString() string { return "" }
+
+func (c ChannelEndpoint) DstToString() string { return fmt.Sprintf("127.0.0.1:%d", c) }
+
+func (c ChannelEndpoint) DstToBytes() []byte { return []byte{byte(c)} }
+
+func (c ChannelEndpoint) DstIP() net.IP { return net.IPv4(127, 0, 0, 1) }
+
+func (c ChannelEndpoint) SrcIP() net.IP { return nil }
+
+func (c *ChannelBind) Open(port uint16) (actualPort uint16, err error) {
+	c.closeSignal = make(chan bool)
+	if rand.Uint32()&1 == 0 {
+		return uint16(c.source4), nil
+	} else {
+		return uint16(c.source6), nil
+	}
+}
+
+func (c *ChannelBind) Close() error {
+	if c.closeSignal != nil {
+		select {
+		case <-c.closeSignal:
+		default:
+			close(c.closeSignal)
+		}
+	}
+	return nil
+}
+
+func (c *ChannelBind) SetMark(mark uint32) error { return nil }
+
+func (c *ChannelBind) ReceiveIPv6(b []byte) (n int, ep conn.Endpoint, err error) {
+	select {
+	case <-c.closeSignal:
+		return 0, nil, net.ErrClosed
+	case rx := <-*c.rx6:
+		return copy(b, rx), c.target6, nil
+	}
+}
+
+func (c *ChannelBind) ReceiveIPv4(b []byte) (n int, ep conn.Endpoint, err error) {
+	select {
+	case <-c.closeSignal:
+		return 0, nil, net.ErrClosed
+	case rx := <-*c.rx4:
+		return copy(b, rx), c.target4, nil
+	}
+}
+
+func (c *ChannelBind) Send(b []byte, ep conn.Endpoint) error {
+	select {
+	case <-c.closeSignal:
+		return net.ErrClosed
+	default:
+		bc := make([]byte, len(b))
+		copy(bc, b)
+		if ep.(ChannelEndpoint) == c.target4 {
+			*c.tx4 <- bc
+		} else if ep.(ChannelEndpoint) == c.target6 {
+			*c.tx6 <- bc
+		} else {
+			return os.ErrInvalid
+		}
+	}
+	return nil
+}
+
+func (c *ChannelBind) ParseEndpoint(s string) (conn.Endpoint, error) {
+	_, port, err := net.SplitHostPort(s)
+	if err != nil {
+		return nil, err
+	}
+	i, err := strconv.ParseUint(port, 10, 16)
+	if err != nil {
+		return nil, err
+	}
+	return ChannelEndpoint(i), nil
+}