From dc39e98cfb65489e332fb008e7a53c5e9ae77d5b Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Mon, 20 Jan 2020 11:51:24 +1100
Subject: [PATCH] Fix race in requestStrategyThree request timeout callback

---
 client.go           |  2 +-
 connection.go       |  2 ++
 request_strategy.go | 12 +++++++++---
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/client.go b/client.go
index 620b4b62..0990c6e0 100644
--- a/client.go
+++ b/client.go
@@ -1043,7 +1043,7 @@ func (cl *Client) newTorrent(ih metainfo.Hash, specStorage storage.ClientImpl) (
 			L: cl.locker(),
 		},
 	}
-	t.requestStrategy = cl.config.DefaultRequestStrategy(t.requestStrategyCallbacks())
+	t.requestStrategy = cl.config.DefaultRequestStrategy(t.requestStrategyCallbacks(), &cl._mu)
 	t.logger = cl.logger.WithValues(t).WithText(func(m log.Msg) string {
 		return fmt.Sprintf("%v: %s", t, m.Text())
 	})
diff --git a/connection.go b/connection.go
index 0c25e343..4c106cca 100644
--- a/connection.go
+++ b/connection.go
@@ -545,7 +545,9 @@ func (cn *connection) request(r request, mw messageWriter) bool {
 
 func (rs requestStrategyThree) onSentRequest(r request) {
 	rs.lastRequested[r] = time.AfterFunc(rs.duplicateRequestTimeout, func() {
+		rs.timeoutLocker.Lock()
 		delete(rs.lastRequested, r)
+		rs.timeoutLocker.Unlock()
 		rs.callbacks.requestTimedOut(r)
 	})
 }
diff --git a/request_strategy.go b/request_strategy.go
index e2e2c128..bcf6ac63 100644
--- a/request_strategy.go
+++ b/request_strategy.go
@@ -1,6 +1,7 @@
 package torrent
 
 import (
+	"sync"
 	"time"
 
 	"github.com/anacrolix/missinggo/v2/bitmap"
@@ -79,20 +80,25 @@ func (requestStrategyTwo) ShouldRequestWithoutBias(cn requestStrategyConnection)
 type requestStrategyThree struct {
 	// How long to avoid duplicating a pending request.
 	duplicateRequestTimeout time.Duration
+
+	callbacks requestStrategyCallbacks
+
 	// The last time we requested a chunk. Deleting the request from any connection will clear this
 	// value.
 	lastRequested map[request]*time.Timer
-	callbacks     requestStrategyCallbacks
+	// The lock to take when running a request timeout handler.
+	timeoutLocker sync.Locker
 }
 
-type requestStrategyMaker func(callbacks requestStrategyCallbacks) requestStrategy
+type requestStrategyMaker func(callbacks requestStrategyCallbacks, clientLocker sync.Locker) requestStrategy
 
 func requestStrategyThreeMaker(duplicateRequestTimeout time.Duration) requestStrategyMaker {
-	return func(callbacks requestStrategyCallbacks) requestStrategy {
+	return func(callbacks requestStrategyCallbacks, clientLocker sync.Locker) requestStrategy {
 		return requestStrategyThree{
 			duplicateRequestTimeout: duplicateRequestTimeout,
 			callbacks:               callbacks,
 			lastRequested:           make(map[request]*time.Timer),
+			timeoutLocker:           clientLocker,
 		}
 	}
 }
-- 
2.48.1