TUN-8052: Update go to 1.21.5

Also update golang.org/x/net and google.golang.org/grpc to fix vulnerabilities,
although cloudflared is using them in a way that is not exposed to those risks

vendor/google.golang.org/grpc/internal/buffer/unbounded.go

@@ -18,7 +18,10 @@
 // Package buffer provides an implementation of an unbounded buffer.
 package buffer
 
-import "sync"
+import (
+	"errors"
+	"sync"
+)
 
 // Unbounded is an implementation of an unbounded buffer which does not use
 // extra goroutines. This is typically used for passing updates from one entity
@@ -28,42 +31,50 @@ import "sync"
 // the underlying mutex used for synchronization.
 //
 // Unbounded supports values of any type to be stored in it by using a channel
-// of `interface{}`. This means that a call to Put() incurs an extra memory
-// allocation, and also that users need a type assertion while reading. For
-// performance critical code paths, using Unbounded is strongly discouraged and
-// defining a new type specific implementation of this buffer is preferred. See
+// of `any`. This means that a call to Put() incurs an extra memory allocation,
+// and also that users need a type assertion while reading. For performance
+// critical code paths, using Unbounded is strongly discouraged and defining a
+// new type specific implementation of this buffer is preferred. See
 // internal/transport/transport.go for an example of this.
 type Unbounded struct {
-	c       chan interface{}
+	c       chan any
+	closed  bool
+	closing bool
 	mu      sync.Mutex
-	backlog []interface{}
+	backlog []any
 }
 
 // NewUnbounded returns a new instance of Unbounded.
 func NewUnbounded() *Unbounded {
-	return &Unbounded{c: make(chan interface{}, 1)}
+	return &Unbounded{c: make(chan any, 1)}
 }
 
+var errBufferClosed = errors.New("Put called on closed buffer.Unbounded")
+
 // Put adds t to the unbounded buffer.
-func (b *Unbounded) Put(t interface{}) {
+func (b *Unbounded) Put(t any) error {
 	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.closing {
+		return errBufferClosed
+	}
 	if len(b.backlog) == 0 {
 		select {
 		case b.c <- t:
-			b.mu.Unlock()
-			return
+			return nil
 		default:
 		}
 	}
 	b.backlog = append(b.backlog, t)
-	b.mu.Unlock()
+	return nil
 }
 
-// Load sends the earliest buffered data, if any, onto the read channel
-// returned by Get(). Users are expected to call this every time they read a
+// Load sends the earliest buffered data, if any, onto the read channel returned
+// by Get(). Users are expected to call this every time they successfully read a
 // value from the read channel.
 func (b *Unbounded) Load() {
 	b.mu.Lock()
+	defer b.mu.Unlock()
 	if len(b.backlog) > 0 {
 		select {
 		case b.c <- b.backlog[0]:
@@ -71,8 +82,9 @@ func (b *Unbounded) Load() {
 			b.backlog = b.backlog[1:]
 		default:
 		}
+	} else if b.closing && !b.closed {
+		close(b.c)
 	}
-	b.mu.Unlock()
 }
 
 // Get returns a read channel on which values added to the buffer, via Put(),
@@ -80,6 +92,25 @@ func (b *Unbounded) Load() {
 //
 // Upon reading a value from this channel, users are expected to call Load() to
 // send the next buffered value onto the channel if there is any.
-func (b *Unbounded) Get() <-chan interface{} {
+//
+// If the unbounded buffer is closed, the read channel returned by this method
+// is closed after all data is drained.
+func (b *Unbounded) Get() <-chan any {
 	return b.c
 }
+
+// Close closes the unbounded buffer. No subsequent data may be Put(), and the
+// channel returned from Get() will be closed after all the data is read and
+// Load() is called for the final time.
+func (b *Unbounded) Close() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.closing {
+		return
+	}
+	b.closing = true
+	if len(b.backlog) == 0 {
+		b.closed = true
+		close(b.c)
+	}
+}