Fix race conditions

Author: kylecarbs

wsnet/rtc.go

@@ -9,6 +9,7 @@ import (
 	"io"
 	"net"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/pion/dtls/v2"
@@ -168,27 +169,34 @@ func newPeerConnection(servers []webrtc.ICEServer) (*webrtc.PeerConnection, erro
 
 // Proxies ICE candidates using the protocol to a writer.
 func proxyICECandidates(conn *webrtc.PeerConnection, w io.Writer) func() {
-	queue := make([]*webrtc.ICECandidate, 0)
-	flushed := false
-	write := func(i *webrtc.ICECandidate) {
-		b, _ := json.Marshal(&protoMessage{
-			Candidate: i.ToJSON().Candidate,
-		})
-		_, _ = w.Write(b)
-	}
+	var (
+		mut     sync.Mutex
+		queue   = []*webrtc.ICECandidate{}
+		flushed = false
+		write   = func(i *webrtc.ICECandidate) {
+			b, _ := json.Marshal(&protoMessage{
+				Candidate: i.ToJSON().Candidate,
+			})
+			_, _ = w.Write(b)
+		}
+	)
 
 	conn.OnICECandidate(func(i *webrtc.ICECandidate) {
 		if i == nil {
 			return
 		}
 		if !flushed {
+			mut.Lock()
+			defer mut.Unlock()
 			queue = append(queue, i)
 			return
 		}
 
 		write(i)
 	})
 	return func() {
+		mut.Lock()
+		defer mut.Unlock()
 		for _, i := range queue {
 			write(i)
 		}

wsnet/wsnet_test.go

@@ -1,5 +1,3 @@
-// +build !race
-
 package wsnet
 
 import (
@@ -15,6 +13,7 @@ import (
 	"math/big"
 	"net"
 	"net/http"
+	"sync"
 	"testing"
 	"time"
 
@@ -35,14 +34,19 @@ func createDumbBroker(t *testing.T) (connectAddr string, listenAddr string) {
 	t.Cleanup(func() {
 		listener.Close()
 	})
-	mux := http.NewServeMux()
-	var sess *yamux.Session
+	var (
+		mux  = http.NewServeMux()
+		sess *yamux.Session
+		mut  sync.Mutex
+	)
 	mux.HandleFunc("/listen", func(w http.ResponseWriter, r *http.Request) {
 		c, err := websocket.Accept(w, r, nil)
 		if err != nil {
 			t.Error(err)
 		}
 		nc := websocket.NetConn(context.Background(), c, websocket.MessageBinary)
+		mut.Lock()
+		defer mut.Unlock()
 		sess, err = yamux.Client(nc, nil)
 		if err != nil {
 			t.Error(err)
@@ -54,6 +58,8 @@ func createDumbBroker(t *testing.T) (connectAddr string, listenAddr string) {
 			t.Error(err)
 		}
 		nc := websocket.NetConn(context.Background(), c, websocket.MessageBinary)
+		mut.Lock()
+		defer mut.Unlock()
 		oc, err := sess.Open()
 		if err != nil {
 			t.Error(err)