conn, device, tun: implement vectorized I/O plumbing

Accept packet vectors for reading and writing in the tun.Device and
conn.Bind interfaces, so that the internal plumbing between these
interfaces now passes a vector of packets. Vectors move untouched
between these interfaces, i.e. if 128 packets are received from
conn.Bind.Read(), 128 packets are passed to tun.Device.Write(). There is
no internal buffering.

Currently, existing implementations are only adjusted to have vectors
of length one. Subsequent patches will improve that.

Also, as a related fixup, use the unix and windows packages rather than
the syscall package when possible.

Co-authored-by: James Tucker <james@tailscale.com>
Signed-off-by: James Tucker <james@tailscale.com>
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 17 insertions, 9 deletions

diff --git a/device/peer.go b/device/peer.go
index 0e7b669..0ac4896 100644
--- a/device/peer.go
+++ b/device/peer.go
@@ -45,9 +45,9 @@ type Peer struct {
 	}
 
 	queue struct {
-		staged   chan *QueueOutboundElement // staged packets before a handshake is available
-		outbound *autodrainingOutboundQueue // sequential ordering of udp transmission
-		inbound  *autodrainingInboundQueue  // sequential ordering of tun writing
+		staged   chan *[]*QueueOutboundElement // staged packets before a handshake is available
+		outbound *autodrainingOutboundQueue    // sequential ordering of udp transmission
+		inbound  *autodrainingInboundQueue     // sequential ordering of tun writing
 	}
 
 	cookieGenerator             CookieGenerator
@@ -81,7 +81,7 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
 	peer.device = device
 	peer.queue.outbound = newAutodrainingOutboundQueue(device)
 	peer.queue.inbound = newAutodrainingInboundQueue(device)
-	peer.queue.staged = make(chan *QueueOutboundElement, QueueStagedSize)
+	peer.queue.staged = make(chan *[]*QueueOutboundElement, QueueStagedSize)
 
 	// map public key
 	_, ok := device.peers.keyMap[pk]
@@ -108,7 +108,7 @@ func (device *Device) NewPeer(pk NoisePublicKey) (*Peer, error) {
 	return peer, nil
 }
 
-func (peer *Peer) SendBuffer(buffer []byte) error {
+func (peer *Peer) SendBuffers(buffers [][]byte) error {
 	peer.device.net.RLock()
 	defer peer.device.net.RUnlock()
 
@@ -123,9 +123,13 @@ func (peer *Peer) SendBuffer(buffer []byte) error {
 		return errors.New("no known endpoint for peer")
 	}
 
-	err := peer.device.net.bind.Send(buffer, peer.endpoint)
+	err := peer.device.net.bind.Send(buffers, peer.endpoint)
 	if err == nil {
-		peer.txBytes.Add(uint64(len(buffer)))
+		var totalLen uint64
+		for _, b := range buffers {
+			totalLen += uint64(len(b))
+		}
+		peer.txBytes.Add(totalLen)
 	}
 	return err
 }
@@ -187,8 +191,12 @@ func (peer *Peer) Start() {
 
 	device.flushInboundQueue(peer.queue.inbound)
 	device.flushOutboundQueue(peer.queue.outbound)
-	go peer.RoutineSequentialSender()
-	go peer.RoutineSequentialReceiver()
+
+	// Use the device batch size, not the bind batch size, as the device size is
+	// the size of the batch pools.
+	batchSize := peer.device.BatchSize()
+	go peer.RoutineSequentialSender(batchSize)
+	go peer.RoutineSequentialReceiver(batchSize)
 
 	peer.isRunning.Store(true)
 }