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fix: Close peer negotiate mutex if we haven't negotiated #1774

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Merged
merged 2 commits into from
May 27, 2022
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fix: Close peer negotiate mutex if we haven't negotiated #1774

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a7a1ec5
fix: Close peer negotiate mutex if we haven't negotiated
kylecarbs May 26, 2022
98a81ba
Merge branch 'main' into negotiatemutex
kylecarbs May 27, 2022
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fix: Close peer negotiate mutex if we haven't negotiated 
Closes #1706 and #1644.
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@kylecarbs
kylecarbs committed May 27, 2022
commit a7a1ec5fb6879240771aa9b0557dae45317deef3
9 changes: 9 additions & 0 deletions peer/channel.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ import (
"io"
"net"
"sync"
"time"

"github.com/pion/datachannel"
"github.com/pion/webrtc/v3"
Expand Down Expand Up @@ -244,6 +245,14 @@ func (c *Channel) Write(bytes []byte) (n int, err error) {
if c.dc.BufferedAmount()+uint64(len(bytes)) >= maxBufferedAmount {
<-c.sendMore
}

// There's an obvious race-condition here. This is an edge-case, as
// most-frequently data won't be pooled so synchronously, but is
// definitely possible.
//
// See: https://github.com/pion/sctp/issues/181
time.Sleep(time.Microsecond)

return c.rwc.Write(bytes)
}

Expand Down
34 changes: 22 additions & 12 deletions peer/conn.go
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Expand Up @@ -73,6 +73,7 @@ func newWithClientOrServer(servers []webrtc.ICEServer, client bool, opts *ConnOp
dcFailedChannel: make(chan struct{}),
localCandidateChannel: make(chan webrtc.ICECandidateInit),
localSessionDescriptionChannel: make(chan webrtc.SessionDescription, 1),
negotiated: make(chan struct{}),
remoteSessionDescriptionChannel: make(chan webrtc.SessionDescription, 1),
settingEngine: opts.SettingEngine,
}
Expand Down Expand Up @@ -124,8 +125,7 @@ type Conn struct {
localSessionDescriptionChannel chan webrtc.SessionDescription
remoteSessionDescriptionChannel chan webrtc.SessionDescription

negotiateMutex sync.Mutex
hasNegotiated bool
negotiated chan struct{}

loggerValue atomic.Value
settingEngine webrtc.SettingEngine
Expand All @@ -152,9 +152,6 @@ func (c *Conn) logger() slog.Logger {
}

func (c *Conn) init() error {
// The negotiation needed callback can take a little bit to execute!
c.negotiateMutex.Lock()

c.rtc.OnNegotiationNeeded(c.negotiate)
c.rtc.OnICEConnectionStateChange(func(iceConnectionState webrtc.ICEConnectionState) {
c.closedICEMutex.Lock()
Expand Down Expand Up @@ -290,11 +287,13 @@ func (c *Conn) negotiate() {
c.logger().Debug(context.Background(), "negotiating")
// ICE candidates cannot be added until SessionDescriptions have been
// exchanged between peers.
if c.hasNegotiated {
c.negotiateMutex.Lock()
}
c.hasNegotiated = true
defer c.negotiateMutex.Unlock()
defer func() {
select {
case <-c.negotiated:
default:
close(c.negotiated)
}
}()

if c.offerer {
offer, err := c.rtc.CreateOffer(&webrtc.OfferOptions{})
Expand Down Expand Up @@ -368,8 +367,10 @@ func (c *Conn) AddRemoteCandidate(i webrtc.ICECandidateInit) {
// This must occur in a goroutine to allow the SessionDescriptions
// to be exchanged first.
go func() {
c.negotiateMutex.Lock()
defer c.negotiateMutex.Unlock()
select {
case <-c.closed:
case <-c.negotiated:
}
if c.isClosed() {
return
}
Expand Down Expand Up @@ -605,6 +606,15 @@ func (c *Conn) CloseWithError(err error) error {
// All logging, goroutines, and async functionality is cleaned up after this.
c.dcClosedWaitGroup.Wait()

// It's possible the connection can be closed before negotiation has
// began. In this case, we want to unlock the mutex to unblock any
// pending candidates being flushed.
select {
case <-c.negotiated:
default:
close(c.negotiated)
}
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Shouldn't you close(c.closed) sooner?

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Nah, but you did bring up a good point about the second close not being needed. Fixed!


// Disable logging!
c.loggerValue.Store(slog.Logger{})
logger.Sync()
Expand Down
2 changes: 0 additions & 2 deletions peer/conn_test.go
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Expand Up @@ -59,9 +59,7 @@ func TestMain(m *testing.M) {
}

func TestConn(t *testing.T) {
t.Skip("known flake -- https://github.com/coder/coder/issues/1644")
t.Parallel()

t.Run("Ping", func(t *testing.T) {
t.Parallel()
client, server, _ := createPair(t)
Expand Down