From a16bfd77759b36aa61065c609ba61b31517b6e06 Mon Sep 17 00:00:00 2001
From: Alex <alex@akselrod.org>
Date: Thu, 11 Jan 2018 03:21:49 -0700
Subject: [PATCH] chain/neutrino: fix data races due to not using pointer for
 rescan

---
 chain/neutrino.go | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/chain/neutrino.go b/chain/neutrino.go
index 280ec1e..c9c7bf6 100644
--- a/chain/neutrino.go
+++ b/chain/neutrino.go
@@ -20,7 +20,7 @@ type NeutrinoClient struct {
 	CS *neutrino.ChainService
 
 	// We currently support one rescan/notifiction goroutine per client
-	rescan neutrino.Rescan
+	rescan *neutrino.Rescan
 
 	enqueueNotification chan interface{}
 	dequeueNotification chan interface{}
@@ -181,6 +181,8 @@ func (s *NeutrinoClient) Rescan(startHash *chainhash.Hash, addrs []btcutil.Addre
 		s.clientMtx.Unlock()
 		s.rescan.WaitForShutdown()
 		s.clientMtx.Lock()
+		s.rescan = nil
+		s.rescanErr = nil
 	}
 	s.rescanQuit = make(chan struct{})
 	s.scanning = true
@@ -214,7 +216,7 @@ func (s *NeutrinoClient) Rescan(startHash *chainhash.Hash, addrs []btcutil.Addre
 		}
 	}
 
-	s.rescan = s.CS.NewRescan(
+	newRescan := s.CS.NewRescan(
 		neutrino.NotificationHandlers(rpcclient.NotificationHandlers{
 			OnBlockConnected:         s.onBlockConnected,
 			OnFilteredBlockConnected: s.onFilteredBlockConnected,
@@ -226,6 +228,7 @@ func (s *NeutrinoClient) Rescan(startHash *chainhash.Hash, addrs []btcutil.Addre
 		neutrino.WatchAddrs(addrs...),
 		neutrino.WatchOutPoints(watchOutPoints...),
 	)
+	s.rescan = &newRescan
 	s.rescanErr = s.rescan.Start()
 
 	return nil
@@ -263,7 +266,7 @@ func (s *NeutrinoClient) NotifyReceived(addrs []btcutil.Address) error {
 	s.lastProgressSent = true
 
 	// Rescan with just the specified addresses.
-	s.rescan = s.CS.NewRescan(
+	newRescan := s.CS.NewRescan(
 		neutrino.NotificationHandlers(rpcclient.NotificationHandlers{
 			OnBlockConnected:         s.onBlockConnected,
 			OnFilteredBlockConnected: s.onFilteredBlockConnected,
@@ -273,6 +276,7 @@ func (s *NeutrinoClient) NotifyReceived(addrs []btcutil.Address) error {
 		neutrino.QuitChan(s.rescanQuit),
 		neutrino.WatchAddrs(addrs...),
 	)
+	s.rescan = &newRescan
 	s.rescanErr = s.rescan.Start()
 	s.clientMtx.Unlock()
 	return nil
@@ -467,6 +471,9 @@ func (s *NeutrinoClient) notificationHandler() {
 	var next interface{}
 out:
 	for {
+		s.clientMtx.Lock()
+		rescanErr := s.rescanErr
+		s.clientMtx.Unlock()
 		select {
 		case n, ok := <-enqueue:
 			if !ok {
@@ -506,7 +513,7 @@ out:
 				dequeue = nil
 			}
 
-		case err := <-s.rescanErr:
+		case err := <-rescanErr:
 			if err != nil {
 				log.Errorf("Neutrino rescan ended with error: %s", err)
 			}