set the offset in BLOCKED and STREAM_BLOCKED frames

internal/flowcontrol/base_flow_controller.go

@@ -79,11 +79,16 @@ func (c *baseFlowController) getWindowUpdate() protocol.ByteCount {
 	return c.receiveWindow
 }
 
-func (c *baseFlowController) IsBlocked() bool {
+// IsBlocked says if it is blocked by flow control.
+// If it is blocked, the offset is returned.
+func (c *baseFlowController) IsBlocked() (bool, protocol.ByteCount) {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
 
-	return c.sendWindowSize() == 0
+	if c.sendWindowSize() != 0 {
+		return false, 0
+	}
+	return true, c.sendWindow
 }
 
 // maybeAdjustWindowIncrement increases the receiveWindowIncrement if we're sending updates too often.

internal/flowcontrol/base_flow_controller_test.go

@@ -54,7 +54,9 @@ var _ = Describe("Base Flow controller", func() {
 			controller.UpdateSendWindow(100)
 			Expect(controller.IsBlocked()).To(BeFalse())
 			controller.AddBytesSent(100)
-			Expect(controller.IsBlocked()).To(BeTrue())
+			blocked, offset := controller.IsBlocked()
+			Expect(blocked).To(BeTrue())
+			Expect(offset).To(Equal(protocol.ByteCount(100)))
 		})
 	})
 

internal/flowcontrol/interface.go

@@ -5,7 +5,7 @@ import "github.com/lucas-clemente/quic-go/internal/protocol"
 type flowController interface {
 	// for sending
 	SendWindowSize() protocol.ByteCount
-	IsBlocked() bool
+	IsBlocked() (bool, protocol.ByteCount)
 	UpdateSendWindow(protocol.ByteCount)
 	AddBytesSent(protocol.ByteCount)
 	// for receiving

internal/flowcontrol/stream_flow_controller_test.go

@@ -233,7 +233,8 @@ var _ = Describe("Stream Flow controller", func() {
 			controller.connection.UpdateSendWindow(50)
 			controller.UpdateSendWindow(100)
 			controller.AddBytesSent(50)
-			Expect(controller.connection.IsBlocked()).To(BeTrue())
+			blocked, _ := controller.connection.IsBlocked()
+			Expect(blocked).To(BeTrue())
 			Expect(controller.IsBlocked()).To(BeFalse())
 		})
 	})