From 4d286dcfeb9742b5483e382f6cc7fdb6d5777563 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Fri, 29 Nov 2019 11:46:01 +0300
Subject: [PATCH] network: check height before requesting headers

Only request headers from the other peer if his height is bigger than
ours. Otherwise we routinely ask 0-height newcomers for some random headers
that they know nothing about.
---
 pkg/network/server.go | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/pkg/network/server.go b/pkg/network/server.go
index 3220b8934..3e6e333b5 100644
--- a/pkg/network/server.go
+++ b/pkg/network/server.go
@@ -284,6 +284,8 @@ func (s *Server) PeerCount() int {
 // startProtocol starts a long running background loop that interacts
 // every ProtoTickInterval with the peer.
 func (s *Server) startProtocol(p Peer) {
+	var err error
+
 	log.WithFields(log.Fields{
 		"addr":        p.RemoteAddr(),
 		"userAgent":   string(p.Version().UserAgent),
@@ -292,10 +294,12 @@ func (s *Server) startProtocol(p Peer) {
 	}).Info("started protocol")
 
 	s.discovery.RegisterGoodAddr(p.PeerAddr().String())
-	err := s.requestHeaders(p)
-	if err != nil {
-		p.Disconnect(err)
-		return
+	if s.chain.HeaderHeight() < p.Version().StartHeight {
+		err = s.requestHeaders(p)
+		if err != nil {
+			p.Disconnect(err)
+			return
+		}
 	}
 
 	timer := time.NewTimer(s.ProtoTickInterval)