From 89d754da6f77116b16114f5a843d0894df1a5415 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Tue, 18 Jan 2022 00:04:41 +0300
Subject: [PATCH] network: don't request blocks we already have in the queue

Fixes #2258.
---
 pkg/network/blockqueue.go      | 13 ++++++++++++-
 pkg/network/blockqueue_test.go |  5 +++++
 pkg/network/server.go          | 11 ++++++++++-
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/pkg/network/blockqueue.go b/pkg/network/blockqueue.go
index ef85c878f..f3437d912 100644
--- a/pkg/network/blockqueue.go
+++ b/pkg/network/blockqueue.go
@@ -17,8 +17,9 @@ type Blockqueuer interface {
 
 type blockQueue struct {
 	log         *zap.Logger
-	queueLock   sync.Mutex
+	queueLock   sync.RWMutex
 	queue       []*block.Block
+	lastQ       uint32
 	checkBlocks chan struct{}
 	chain       Blockqueuer
 	relayF      func(*block.Block)
@@ -115,6 +116,10 @@ func (bq *blockQueue) putBlock(block *block.Block) error {
 	if bq.queue[pos] == nil || bq.queue[pos].Index < block.Index {
 		bq.len++
 		bq.queue[pos] = block
+		for pos < blockCacheSize && bq.queue[pos] != nil && bq.lastQ+1 == bq.queue[pos].Index {
+			bq.lastQ = bq.queue[pos].Index
+			pos++
+		}
 	}
 	l := bq.len
 	bq.queueLock.Unlock()
@@ -129,6 +134,12 @@ func (bq *blockQueue) putBlock(block *block.Block) error {
 	return nil
 }
 
+func (bq *blockQueue) lastQueued() uint32 {
+	bq.queueLock.RLock()
+	defer bq.queueLock.RUnlock()
+	return bq.lastQ
+}
+
 func (bq *blockQueue) discard() {
 	if bq.discarded.CAS(false, true) {
 		close(bq.checkBlocks)
diff --git a/pkg/network/blockqueue_test.go b/pkg/network/blockqueue_test.go
index 7237b8c99..137928c72 100644
--- a/pkg/network/blockqueue_test.go
+++ b/pkg/network/blockqueue_test.go
@@ -22,6 +22,7 @@ func TestBlockQueue(t *testing.T) {
 	for i := 3; i < 5; i++ {
 		assert.NoError(t, bq.putBlock(blocks[i]))
 	}
+	assert.Equal(t, uint32(0), bq.lastQueued())
 	// nothing should be put into the blockchain
 	assert.Equal(t, uint32(0), chain.BlockHeight())
 	assert.Equal(t, 2, bq.length())
@@ -30,6 +31,7 @@ func TestBlockQueue(t *testing.T) {
 		assert.NoError(t, bq.putBlock(blocks[i]))
 	}
 	// but they're still not put into the blockchain, because bq isn't running
+	assert.Equal(t, uint32(4), bq.lastQueued())
 	assert.Equal(t, uint32(0), chain.BlockHeight())
 	assert.Equal(t, 4, bq.length())
 	// block with too big index is dropped
@@ -38,12 +40,14 @@ func TestBlockQueue(t *testing.T) {
 	go bq.run()
 	// run() is asynchronous, so we need some kind of timeout anyway and this is the simplest one
 	assert.Eventually(t, func() bool { return chain.BlockHeight() == 4 }, 4*time.Second, 100*time.Millisecond)
+	assert.Equal(t, uint32(4), bq.lastQueued())
 	assert.Equal(t, 0, bq.length())
 	assert.Equal(t, uint32(4), chain.BlockHeight())
 	// put some old blocks
 	for i := 1; i < 5; i++ {
 		assert.NoError(t, bq.putBlock(blocks[i]))
 	}
+	assert.Equal(t, uint32(4), bq.lastQueued())
 	assert.Equal(t, 0, bq.length())
 	assert.Equal(t, uint32(4), chain.BlockHeight())
 	// unexpected blocks with run() active
@@ -61,6 +65,7 @@ func TestBlockQueue(t *testing.T) {
 	assert.NoError(t, bq.putBlock(blocks[5]))
 	// run() is asynchronous, so we need some kind of timeout anyway and this is the simplest one
 	assert.Eventually(t, func() bool { return chain.BlockHeight() == 8 }, 4*time.Second, 100*time.Millisecond)
+	assert.Equal(t, uint32(8), bq.lastQueued())
 	assert.Equal(t, 1, bq.length())
 	assert.Equal(t, uint32(8), chain.BlockHeight())
 	bq.discard()
diff --git a/pkg/network/server.go b/pkg/network/server.go
index 98815b8af..371842f80 100644
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@@ -1070,7 +1070,16 @@ func (s *Server) handleGetAddrCmd(p Peer) error {
 // 2. Send requests for chunk in increasing order.
 // 3. After all requests were sent, request random height.
 func (s *Server) requestBlocks(bq Blockqueuer, p Peer) error {
-	pl := getRequestBlocksPayload(p, bq.BlockHeight(), &s.lastRequestedBlock)
+	h := bq.BlockHeight()
+	pl := getRequestBlocksPayload(p, h, &s.lastRequestedBlock)
+	lq := s.bQueue.lastQueued()
+	if lq > pl.IndexStart {
+		c := int16(h + blockCacheSize - lq)
+		if c < payload.MaxHashesCount {
+			pl.Count = c
+		}
+		pl.IndexStart = lq + 1
+	}
 	return p.EnqueueP2PMessage(NewMessage(CMDGetBlockByIndex, pl))
 }