commit c28c8ca489633aae2d9b9dbea0e781ca5e44cc66 Author: Cecylia Bocovich cohosh@torproject.org Date: Sat Mar 30 12:19:29 2019 -0400
Fix for proxy deadlock bug
This is a fix for the proxy-go deadlock bug (ticket #25688). The assumption that OnIceComplete is always followed by a successful connection where OnDataChannel has been called turns out not to occur in practice. OnICEComplete looks like it is being deprecated in other libraries anyway, so it's safer to just remove it. --- proxy-go/snowflake.go | 42 ++++++++++++++++-------------------------- 1 file changed, 16 insertions(+), 26 deletions(-)
diff --git a/proxy-go/snowflake.go b/proxy-go/snowflake.go index 2e8fe20..aeb9f51 100644 --- a/proxy-go/snowflake.go +++ b/proxy-go/snowflake.go @@ -259,8 +259,6 @@ func datachannelHandler(conn *webRTCConn, remoteAddr net.Addr) { // Installs an OnDataChannel callback that creates a webRTCConn and passes it to // datachannelHandler. func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config *webrtc.Configuration) (*webrtc.PeerConnection, error) { - errChan := make(chan error) - answerChan := make(chan struct{})
pc, err := webrtc.NewPeerConnection(config) if err != nil { @@ -269,9 +267,6 @@ func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config *webrtc. pc.OnNegotiationNeeded = func() { panic("OnNegotiationNeeded") } - pc.OnIceComplete = func() { - answerChan <- struct{}{} - } pc.OnDataChannel = func(dc *webrtc.DataChannel) { log.Println("OnDataChannel")
@@ -310,30 +305,25 @@ func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config *webrtc. } log.Println("sdp offer successfully received.")
- go func() { - log.Println("Generating answer...") - answer, err := pc.CreateAnswer() // blocking - if err != nil { - errChan <- err - return - } - err = pc.SetLocalDescription(answer) - if err != nil { - errChan <- err - return - } - }() + log.Println("Generating answer...") + answer, err := pc.CreateAnswer() + // blocks on ICE gathering. we need to add a timeout if needed + // not putting this in a separate go routine, because we need + // SetLocalDescription(answer) to be called before sendAnswer + if err != nil { + pc.Destroy() + return nil, err + }
- // Wait until answer is ready. - select { - case err = <-errChan: + if answer == nil { + pc.Destroy() + return nil, fmt.Errorf("Failed gathering ICE candidates.") + } + + err = pc.SetLocalDescription(answer) + if err != nil { pc.Destroy() return nil, err - case _, ok := <-answerChan: - if !ok { - pc.Destroy() - return nil, fmt.Errorf("Failed gathering ICE candidates.") - } } return pc, nil }