Update dependencies

vendor/tailscale.com/wgengine/netstack/link_endpoint.go

@@ -16,19 +16,27 @@ import (
 )
 
 type queue struct {
-	// TODO(jwhited): evaluate performance with mu as Mutex and/or alternative
-	//  non-channel buffer.
-	c      chan *stack.PacketBuffer
-	mu     sync.RWMutex // mu guards closed
+	// TODO(jwhited): evaluate performance with a non-channel buffer.
+	c chan *stack.PacketBuffer
+
+	closeOnce sync.Once
+	closedCh  chan struct{}
+
+	mu     sync.RWMutex
 	closed bool
 }
 
 func (q *queue) Close() {
+	q.closeOnce.Do(func() {
+		close(q.closedCh)
+	})
+
 	q.mu.Lock()
 	defer q.mu.Unlock()
-	if !q.closed {
-		close(q.c)
+	if q.closed {
+		return
 	}
+	close(q.c)
 	q.closed = true
 }
 
@@ -51,26 +59,27 @@ func (q *queue) ReadContext(ctx context.Context) *stack.PacketBuffer {
 }
 
 func (q *queue) Write(pkt *stack.PacketBuffer) tcpip.Error {
-	// q holds the PacketBuffer.
 	q.mu.RLock()
 	defer q.mu.RUnlock()
 	if q.closed {
 		return &tcpip.ErrClosedForSend{}
 	}
-
-	wrote := false
 	select {
 	case q.c <- pkt.IncRef():
-		wrote = true
-	default:
-		// TODO(jwhited): reconsider/count
-		pkt.DecRef()
-	}
-
-	if wrote {
 		return nil
+	case <-q.closedCh:
+		pkt.DecRef()
+		return &tcpip.ErrClosedForSend{}
 	}
-	return &tcpip.ErrNoBufferSpace{}
+}
+
+func (q *queue) Drain() int {
+	c := 0
+	for pkt := range q.c {
+		pkt.DecRef()
+		c++
+	}
+	return c
 }
 
 func (q *queue) Num() int {
@@ -107,7 +116,8 @@ func newLinkEndpoint(size int, mtu uint32, linkAddr tcpip.LinkAddress, supported
 	le := &linkEndpoint{
 		supportedGRO: supportedGRO,
 		q: &queue{
-			c: make(chan *stack.PacketBuffer, size),
+			c:        make(chan *stack.PacketBuffer, size),
+			closedCh: make(chan struct{}),
 		},
 		mtu:      mtu,
 		linkAddr: linkAddr,
@@ -164,12 +174,7 @@ func (l *linkEndpoint) ReadContext(ctx context.Context) *stack.PacketBuffer {
 
 // Drain removes all outbound packets from the channel and counts them.
 func (l *linkEndpoint) Drain() int {
-	c := 0
-	for pkt := l.Read(); pkt != nil; pkt = l.Read() {
-		pkt.DecRef()
-		c++
-	}
-	return c
+	return l.q.Drain()
 }
 
 // NumQueued returns the number of packets queued for outbound.