From 98ca17aab896813eb164f625779bbb6155d51893 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Wed, 2 Sep 2020 15:00:53 +0300
Subject: [PATCH] network: restrict block queue size

Close #1374.
---
 pkg/network/blockqueue.go      | 9 ++++++++-
 pkg/network/blockqueue_test.go | 3 +++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/pkg/network/blockqueue.go b/pkg/network/blockqueue.go
index 179c468a1..a5bb92c42 100644
--- a/pkg/network/blockqueue.go
+++ b/pkg/network/blockqueue.go
@@ -15,6 +15,12 @@ type blockQueue struct {
 	relayF      func(*block.Block)
 }
 
+const (
+	// blockCacheSize is the amount of blocks above current height
+	// which are stored in queue.
+	blockCacheSize = 2000
+)
+
 func newBlockQueue(capacity int, bc blockchainer.Blockchainer, log *zap.Logger, relayer func(*block.Block)) *blockQueue {
 	if log == nil {
 		return nil
@@ -66,7 +72,8 @@ func (bq *blockQueue) run() {
 }
 
 func (bq *blockQueue) putBlock(block *block.Block) error {
-	if bq.chain.BlockHeight() >= block.Index {
+	h := bq.chain.BlockHeight()
+	if block.Index <= h || h+blockCacheSize < block.Index {
 		// can easily happen when fetching the same blocks from
 		// different peers, thus not considered as error
 		return nil
diff --git a/pkg/network/blockqueue_test.go b/pkg/network/blockqueue_test.go
index 7141976cf..85382c526 100644
--- a/pkg/network/blockqueue_test.go
+++ b/pkg/network/blockqueue_test.go
@@ -31,6 +31,9 @@ func TestBlockQueue(t *testing.T) {
 	// but they're still not put into the blockchain, because bq isn't running
 	assert.Equal(t, uint32(0), chain.BlockHeight())
 	assert.Equal(t, 4, bq.length())
+	// block with too big index is dropped
+	assert.NoError(t, bq.putBlock(&block.Block{Base: block.Base{Index: bq.chain.BlockHeight() + blockCacheSize + 1}}))
+	assert.Equal(t, 4, bq.length())
 	go bq.run()
 	// run() is asynchronous, so we need some kind of timeout anyway and this is the simplest one
 	for i := 0; i < 5; i++ {