From 53423b7c3723e04e4c15f313f4327e7950a73e4b Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 22 Apr 2022 14:45:37 +0300
Subject: [PATCH] network: fix panic in blockqueue during shutdown

panic: send on closed channel

goroutine 116 [running]:
github.com/nspcc-dev/neo-go/pkg/network.(*blockQueue).putBlock(0xc00011b650, 0xc01e371200)
        github.com/nspcc-dev/neo-go/pkg/network/blockqueue.go:129 +0x185
github.com/nspcc-dev/neo-go/pkg/network.(*Server).handleBlockCmd(0xc0002d3c00, {0xf69b7f?, 0xc001520010?}, 0xc02eb44000?)
        github.com/nspcc-dev/neo-go/pkg/network/server.go:607 +0x6f
github.com/nspcc-dev/neo-go/pkg/network.(*Server).handleMessage(0xc0002d3c00, {0x121f4c8?, 0xc001528000?}, 0xc01e35cf80)
        github.com/nspcc-dev/neo-go/pkg/network/server.go:1160 +0x6c5
github.com/nspcc-dev/neo-go/pkg/network.(*TCPPeer).handleIncoming(0xc001528000)
        github.com/nspcc-dev/neo-go/pkg/network/tcp_peer.go:189 +0x98
created by github.com/nspcc-dev/neo-go/pkg/network.(*TCPPeer).handleConn
        github.com/nspcc-dev/neo-go/pkg/network/tcp_peer.go:164 +0xcf
---
 pkg/network/blockqueue.go | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/pkg/network/blockqueue.go b/pkg/network/blockqueue.go
index f3437d912..992ea54c8 100644
--- a/pkg/network/blockqueue.go
+++ b/pkg/network/blockqueue.go
@@ -105,10 +105,13 @@ func (bq *blockQueue) run() {
 func (bq *blockQueue) putBlock(block *block.Block) error {
 	h := bq.chain.BlockHeight()
 	bq.queueLock.Lock()
+	defer bq.queueLock.Unlock()
+	if bq.discarded.Load() {
+		return nil
+	}
 	if block.Index <= h || h+blockCacheSize < block.Index {
 		// can easily happen when fetching the same blocks from
 		// different peers, thus not considered as error
-		bq.queueLock.Unlock()
 		return nil
 	}
 	pos := indexToPosition(block.Index)
@@ -122,7 +125,6 @@ func (bq *blockQueue) putBlock(block *block.Block) error {
 		}
 	}
 	l := bq.len
-	bq.queueLock.Unlock()
 	// update metrics
 	updateBlockQueueLenMetric(l)
 	select {
@@ -142,8 +144,8 @@ func (bq *blockQueue) lastQueued() uint32 {
 
 func (bq *blockQueue) discard() {
 	if bq.discarded.CAS(false, true) {
-		close(bq.checkBlocks)
 		bq.queueLock.Lock()
+		close(bq.checkBlocks)
 		// Technically we could bq.queue = nil, but this would cost
 		// another if in run().
 		for i := 0; i < len(bq.queue); i++ {