From ef6dbe6863d92710fd2da7781e5b2aac87578751 Mon Sep 17 00:00:00 2001 From: Suhas Daftuar Date: Wed, 26 Jan 2022 18:29:56 -0500 Subject: [PATCH] Respond to getheaders if we have sufficient chainwork Previously, we would check to see if we were in IBD and ignore getheaders requests accordingly. However, the IBD criteria -- an optimization mostly targeted at behavior when we have peers serving us many blocks we need to download -- is difficult to reason about in edge-case scenarios, such as if the network were to go a long time without any blocks found and nodes getting restarted during that time. To make things simpler to reason about, just use nMinimumChainWork as our anti-DoS threshold; as long as our chain has that much work, it should be fine to respond to a peer asking for our headers (and this should allow such a peer to request blocks from us if needed). --- src/net_processing.cpp | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/src/net_processing.cpp b/src/net_processing.cpp index 273cb4fccb5..ac6b4654f17 100644 --- a/src/net_processing.cpp +++ b/src/net_processing.cpp @@ -3189,9 +3189,23 @@ void PeerManagerImpl::ProcessMessage(CNode& pfrom, const std::string& msg_type, return; } + if (fImporting || fReindex) { + LogPrint(BCLog::NET, "Ignoring getheaders from peer=%d while importing/reindexing\n", pfrom.GetId()); + return; + } + LOCK(cs_main); - if (m_chainman.ActiveChainstate().IsInitialBlockDownload() && !pfrom.HasPermission(NetPermissionFlags::Download)) { - LogPrint(BCLog::NET, "Ignoring getheaders from peer=%d because node is in initial block download\n", pfrom.GetId()); + + // Note that if we were to be on a chain that forks from the checkpointed + // chain, then serving those headers to a peer that has seen the + // checkpointed chain would cause that peer to disconnect us. Requiring + // that our chainwork exceed nMinimumChainWork is a protection against + // being fed a bogus chain when we started up for the first time and + // getting partitioned off the honest network for serving that chain to + // others. + if (m_chainman.ActiveTip() == nullptr || + (m_chainman.ActiveTip()->nChainWork < nMinimumChainWork && !pfrom.HasPermission(NetPermissionFlags::Download))) { + LogPrint(BCLog::NET, "Ignoring getheaders from peer=%d because active chain has too little work\n", pfrom.GetId()); return; }