make the FlowController thread-safe

flow_controller.go

@@ -1,6 +1,8 @@
 package quic
 
 import (
+	"sync"
+
 	"github.com/lucas-clemente/quic-go/handshake"
 	"github.com/lucas-clemente/quic-go/protocol"
 )
@@ -16,6 +18,8 @@ type flowController struct {
 	receiveWindowUpdateThreshold      protocol.ByteCount
 	receiveFlowControlWindow          protocol.ByteCount
 	receiveFlowControlWindowIncrement protocol.ByteCount
+
+	mutex sync.RWMutex
 }
 
 func newFlowController(connectionParametersManager *handshake.ConnectionParametersManager) *flowController {
@@ -28,12 +32,18 @@ func newFlowController(connectionParametersManager *handshake.ConnectionParamete
 }
 
 func (c *flowController) AddBytesSent(n protocol.ByteCount) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	c.bytesSent += n
 }
 
 // UpdateSendWindow should be called after receiving a WindowUpdateFrame
 // it returns true if the window was actually updated
 func (c *flowController) UpdateSendWindow(newOffset protocol.ByteCount) bool {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	if newOffset > c.sendFlowControlWindow {
 		c.sendFlowControlWindow = newOffset
 		return true
@@ -42,6 +52,9 @@ func (c *flowController) UpdateSendWindow(newOffset protocol.ByteCount) bool {
 }
 
 func (c *flowController) SendWindowSize() protocol.ByteCount {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
+
 	if c.bytesSent > c.sendFlowControlWindow { // should never happen, but make sure we don't do an underflow here
 		return 0
 	}
@@ -49,6 +62,9 @@ func (c *flowController) SendWindowSize() protocol.ByteCount {
 }
 
 func (c *flowController) AddBytesRead(n protocol.ByteCount) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	c.bytesRead += n
 }
 
@@ -59,6 +75,9 @@ func (c *flowController) MaybeTriggerBlocked() bool {
 		return false
 	}
 
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	if c.lastBlockedSentForOffset == c.sendFlowControlWindow {
 		return false
 	}
@@ -70,6 +89,9 @@ func (c *flowController) MaybeTriggerBlocked() bool {
 // MaybeTriggerWindowUpdate determines if it is necessary to send a WindowUpdate
 // if so, it returns true and the offset of the window
 func (c *flowController) MaybeTriggerWindowUpdate() (bool, protocol.ByteCount) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	diff := c.receiveFlowControlWindow - c.bytesRead
 	if diff < c.receiveWindowUpdateThreshold {
 		c.receiveFlowControlWindow += c.receiveFlowControlWindowIncrement
@@ -79,6 +101,9 @@ func (c *flowController) MaybeTriggerWindowUpdate() (bool, protocol.ByteCount) {
 }
 
 func (c *flowController) CheckFlowControlViolation(highestByte protocol.ByteCount) bool {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
 	if highestByte > c.receiveFlowControlWindow {
 		return true
 	}