commit ed2d5df87d0be7c86f21d19d42ec90b8d2616ae2
Author: Simone Basso <bassosim...@gmail.com>
Date: Mon Jun 14 10:46:46 2021 +0200
Fix datarace for WebRTCPeer.lastReceive
The race condition occurs because concurrent goroutines are
intermixing reads and writes of `WebRTCPeer.lastReceive`.
Spotted when integrating Snowflake inside OONI in
https://github.com/ooni/probe-cli/pull/373.
---
client/lib/webrtc.go | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/client/lib/webrtc.go b/client/lib/webrtc.go
index af7ba6d..6a42ebd 100644
--- a/client/lib/webrtc.go
+++ b/client/lib/webrtc.go
@@ -21,8 +21,10 @@ type WebRTCPeer struct {
pc *webrtc.PeerConnection
transport *webrtc.DataChannel
- recvPipe *io.PipeReader
- writePipe *io.PipeWriter
+ recvPipe *io.PipeReader
+ writePipe *io.PipeWriter
+
+ mu sync.Mutex // protects the following:
lastReceive time.Time
open chan struct{} // Channel to notify when datachannel opens
@@ -89,12 +91,17 @@ func (c *WebRTCPeer) Close() error {
// Should also update the DataChannel in underlying go-webrtc's to make Closes
// more immediate / responsive.
func (c *WebRTCPeer) checkForStaleness() {
+ c.mu.Lock()
c.lastReceive = time.Now()
+ c.mu.Unlock()
for {
if c.closed {
return
}
- if time.Since(c.lastReceive) > SnowflakeTimeout {
+ c.mu.Lock()
+ lastReceive := c.lastReceive
+ c.mu.Unlock()
+ if time.Since(lastReceive) > SnowflakeTimeout {
log.Printf("WebRTC: No messages received for %v --
closing stale connection.",
SnowflakeTimeout)
c.Close()
@@ -173,7 +180,9 @@ func (c *WebRTCPeer) preparePeerConnection(config
*webrtc.Configuration) error {
log.Printf("c.writePipe.CloseWithError returned
error: %v", inerr)
}
}
+ c.mu.Lock()
c.lastReceive = time.Now()
+ c.mu.Unlock()
})
c.transport = dc
c.open = make(chan struct{})
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