all: make conn.Bind.Open return a slice of receive functions

Instead of hard-coding exactly two sources from which
to receive packets (an IPv4 source and an IPv6 source),
allow the conn.Bind to specify a set of sources.

Beneficial consequences:

* If there's no IPv6 support on a system,
  conn.Bind.Open can choose not to return a receive function for it,
  which is simpler than tracking that state in the bind.
  This simplification removes existing data races from both
  conn.StdNetBind and bindtest.ChannelBind.
* If there are more than two sources on a system,
  the conn.Bind no longer needs to add a separate muxing layer.

Signed-off-by: Josh Bleecher Snyder <josharian@gmail.com>

2 files changed, 12 insertions, 20 deletions

diff --git a/device/device.go b/device/device.go
index 1e32db6..a635e68 100644
--- a/device/device.go
+++ b/device/device.go
@@ -11,9 +11,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	"golang.org/x/net/ipv4"
-	"golang.org/x/net/ipv6"
-
 	"golang.zx2c4.com/wireguard/conn"
 	"golang.zx2c4.com/wireguard/ratelimiter"
 	"golang.zx2c4.com/wireguard/rwcancel"
@@ -468,8 +465,9 @@ func (device *Device) BindUpdate() error {
 
 	// bind to new port
 	var err error
+	var recvFns []conn.ReceiveFunc
 	netc := &device.net
-	netc.port, err = netc.bind.Open(netc.port)
+	recvFns, netc.port, err = netc.bind.Open(netc.port)
 	if err != nil {
 		netc.port = 0
 		return err
@@ -501,11 +499,12 @@ func (device *Device) BindUpdate() error {
 	device.peers.RUnlock()
 
 	// start receiving routines
-	device.net.stopping.Add(2)
-	device.queue.decryption.wg.Add(2) // each RoutineReceiveIncoming goroutine writes to device.queue.decryption
-	device.queue.handshake.wg.Add(2)  // each RoutineReceiveIncoming goroutine writes to device.queue.handshake
-	go device.RoutineReceiveIncoming(ipv4.Version, netc.bind)
-	go device.RoutineReceiveIncoming(ipv6.Version, netc.bind)
+	device.net.stopping.Add(len(recvFns))
+	device.queue.decryption.wg.Add(len(recvFns)) // each RoutineReceiveIncoming goroutine writes to device.queue.decryption
+	device.queue.handshake.wg.Add(len(recvFns))  // each RoutineReceiveIncoming goroutine writes to device.queue.handshake
+	for _, fn := range recvFns {
+		go device.RoutineReceiveIncoming(fn)
+	}
 
 	device.log.Verbosef("UDP bind has been updated")
 	return nil
diff --git a/device/receive.go b/device/receive.go
index 5ddb66c..fa5c0a6 100644
--- a/device/receive.go
+++ b/device/receive.go
@@ -68,15 +68,15 @@ func (peer *Peer) keepKeyFreshReceiving() {
  * Every time the bind is updated a new routine is started for
  * IPv4 and IPv6 (separately)
  */
-func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
+func (device *Device) RoutineReceiveIncoming(recv conn.ReceiveFunc) {
 	defer func() {
-		device.log.Verbosef("Routine: receive incoming IPv%d - stopped", IP)
+		device.log.Verbosef("Routine: receive incoming %p - stopped", recv)
 		device.queue.decryption.wg.Done()
 		device.queue.handshake.wg.Done()
 		device.net.stopping.Done()
 	}()
 
-	device.log.Verbosef("Routine: receive incoming IPv%d - started", IP)
+	device.log.Verbosef("Routine: receive incoming %p - started", recv)
 
 	// receive datagrams until conn is closed
 
@@ -90,14 +90,7 @@ func (device *Device) RoutineReceiveIncoming(IP int, bind conn.Bind) {
 	)
 
 	for {
-		switch IP {
-		case ipv4.Version:
-			size, endpoint, err = bind.ReceiveIPv4(buffer[:])
-		case ipv6.Version:
-			size, endpoint, err = bind.ReceiveIPv6(buffer[:])
-		default:
-			panic("invalid IP version")
-		}
+		size, endpoint, err = recv(buffer[:])
 
 		if err != nil {
 			device.PutMessageBuffer(buffer)