commit 6baa3c4d5f70fd50223dc41febf67576267d039b
Author: Cecylia Bocovich <[email protected]>
Date: Thu Oct 15 14:47:51 2020 -0400
Add synchronization to prevent post-melt collects
This fixes a race condition in which snowflakes.End() is called while
snowflakes.Collect() is in progress resulting in a write to a closed
channel. We now wait for all in-progress collections to finish and add
an extra check before proceeding with a collection.
---
client/lib/peers.go | 15 +++++++++++++--
client/lib/snowflake.go | 1 -
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/client/lib/peers.go b/client/lib/peers.go
index d864fc8..d02eed3 100644
--- a/client/lib/peers.go
+++ b/client/lib/peers.go
@@ -5,6 +5,7 @@ import (
"errors"
"fmt"
"log"
+ "sync"
)
// Container which keeps track of multiple WebRTC remote peers.
@@ -25,7 +26,10 @@ type Peers struct {
snowflakeChan chan *WebRTCPeer
activePeers *list.List
- melt chan struct{}
+ melt chan struct{}
+ melted bool
+
+ collection sync.WaitGroup
}
// Construct a fresh container of remote peers.
@@ -45,6 +49,11 @@ func NewPeers(tongue Tongue) (*Peers, error) {
// As part of |SnowflakeCollector| interface.
func (p *Peers) Collect() (*WebRTCPeer, error) {
// Engage the Snowflake Catching interface, which must be available.
+ p.collection.Add(1)
+ defer p.collection.Done()
+ if p.melted {
+ return nil, fmt.Errorf("Snowflakes have melted")
+ }
if nil == p.Tongue {
return nil, errors.New("missing Tongue to catch Snowflakes
with")
}
@@ -110,8 +119,10 @@ func (p *Peers) purgeClosedPeers() {
// Close all Peers contained here.
func (p *Peers) End() {
- close(p.snowflakeChan)
close(p.melt)
+ p.melted = true
+ p.collection.Wait()
+ close(p.snowflakeChan)
cnt := p.Count()
for e := p.activePeers.Front(); e != nil; {
next := e.Next()
diff --git a/client/lib/snowflake.go b/client/lib/snowflake.go
index 0ba5667..e888160 100644
--- a/client/lib/snowflake.go
+++ b/client/lib/snowflake.go
@@ -181,7 +181,6 @@ func Handler(socks net.Conn, tongue Tongue) error {
// transfer to the Tor SOCKS handler when needed.
func connectLoop(snowflakes SnowflakeCollector) {
for {
- // Check if ending is necessary.
_, err := snowflakes.Collect()
if err != nil {
log.Printf("WebRTC: %v Retrying in %v...",
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