Do not invoke OnBufferedAmountLow after close

datachannel.go

@@ -707,13 +707,23 @@ func (d *DataChannel) OnBufferedAmountLow(f func()) {
 	d.mu.Lock()
 	defer d.mu.Unlock()
 
-	d.onBufferedAmountLow = func() {
+	onBufferedAmountLow := d.makeBufferedAmountLowHandler(f)
-		go f()
+	d.onBufferedAmountLow = onBufferedAmountLow
-	}
+
 	if d.dataChannel != nil {
-		d.dataChannel.OnBufferedAmountLow(func() {
+		d.dataChannel.OnBufferedAmountLow(onBufferedAmountLow)
-			go f()
+	}
-		})
+}
+
+func (d *DataChannel) makeBufferedAmountLowHandler(f func()) func() {
+	return func() {
+		go func() {
+			if d.ReadyState() != DataChannelStateOpen {
+				return
+			}
+
+			f()
+		}()
 	}
 }
 

datachannel_go_test.go

@@ -855,3 +855,49 @@ func TestOnBufferedAmountLowDeadlock(t *testing.T) {
 	<-gotAllMessages.Done()
 	closePairNow(t, offerPC, answerPC)
 }
+
+func TestOnBufferedAmountLowRespectsReadyState(t *testing.T) {
+	t.Run("fires when open", func(t *testing.T) {
+		dc := &DataChannel{}
+		dc.setReadyState(DataChannelStateOpen)
+
+		called := make(chan struct{}, 1)
+		dc.OnBufferedAmountLow(func() {
+			called <- struct{}{}
+		})
+
+		dc.mu.RLock()
+		handler := dc.onBufferedAmountLow
+		dc.mu.RUnlock()
+
+		handler()
+
+		select {
+		case <-called:
+		case <-time.After(time.Second):
+			assert.Fail(t, "expected OnBufferedAmountLow to fire when open")
+		}
+	})
+
+	t.Run("skips when not open", func(t *testing.T) {
+		dc := &DataChannel{}
+		dc.setReadyState(DataChannelStateClosing)
+
+		called := make(chan struct{}, 1)
+		dc.OnBufferedAmountLow(func() {
+			called <- struct{}{}
+		})
+
+		dc.mu.RLock()
+		handler := dc.onBufferedAmountLow
+		dc.mu.RUnlock()
+
+		handler()
+
+		select {
+		case <-called:
+			assert.Fail(t, "expected OnBufferedAmountLow to be ignored when not open")
+		case <-time.After(50 * time.Millisecond):
+		}
+	})
+}

datachannel_js.go

@@ -301,6 +301,10 @@ func (d *DataChannel) OnBufferedAmountLow(f func()) {
 		defer oldHandler.Release()
 	}
 	onBufferedAmountLow := js.FuncOf(func(this js.Value, args []js.Value) any {
+		if d.ReadyState() != DataChannelStateOpen {
+			return js.Undefined()
+		}
+
 		go f()
 		return js.Undefined()
 	})