core, eth/downloader: fix ancestor lookup for fast sync

1 files changed, 29 insertions, 4 deletions

diff --git a/eth/downloader/downloader.go b/eth/downloader/downloader.go
index 1f52fc6db..f81a5cbac 100644
--- a/eth/downloader/downloader.go
+++ b/eth/downloader/downloader.go
@@ -181,6 +181,9 @@ type BlockChain interface {
 	// HasBlock verifies a block's presence in the local chain.
 	HasBlock(common.Hash, uint64) bool
 
+	// HasFastBlock verifies a fast block's presence in the local chain.
+	HasFastBlock(common.Hash, uint64) bool
+
 	// GetBlockByHash retrieves a block from the local chain.
 	GetBlockByHash(common.Hash) *types.Block
 
@@ -663,8 +666,9 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 	if localHeight >= MaxForkAncestry {
 		floor = int64(localHeight - MaxForkAncestry)
 	}
-
 	from, count, skip, max := calculateRequestSpan(remoteHeight, localHeight)
+
+	p.log.Trace("Span searching for common ancestor", "count", count, "from", from, "skip", skip)
 	go p.peer.RequestHeadersByNumber(uint64(from), count, skip, false)
 
 	// Wait for the remote response to the head fetch
@@ -708,8 +712,17 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 				// Otherwise check if we already know the header or not
 				h := headers[i].Hash()
 				n := headers[i].Number.Uint64()
-				if (d.mode == FullSync && d.blockchain.HasBlock(h, n)) ||
-					(d.mode != FullSync && d.lightchain.HasHeader(h, n)) {
+
+				var known bool
+				switch d.mode {
+				case FullSync:
+					known = d.blockchain.HasBlock(h, n)
+				case FastSync:
+					known = d.blockchain.HasFastBlock(h, n)
+				default:
+					known = d.lightchain.HasHeader(h, n)
+				}
+				if known {
 					number, hash = n, h
 					break
 				}
@@ -738,6 +751,8 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 	if floor > 0 {
 		start = uint64(floor)
 	}
+	p.log.Trace("Binary searching for common ancestor", "start", start, "end", end)
+
 	for start+1 < end {
 		// Split our chain interval in two, and request the hash to cross check
 		check := (start + end) / 2
@@ -770,7 +785,17 @@ func (d *Downloader) findAncestor(p *peerConnection, remoteHeader *types.Header)
 				// Modify the search interval based on the response
 				h := headers[0].Hash()
 				n := headers[0].Number.Uint64()
-				if (d.mode == FullSync && !d.blockchain.HasBlock(h, n)) || (d.mode != FullSync && !d.lightchain.HasHeader(h, n)) {
+
+				var known bool
+				switch d.mode {
+				case FullSync:
+					known = d.blockchain.HasBlock(h, n)
+				case FastSync:
+					known = d.blockchain.HasFastBlock(h, n)
+				default:
+					known = d.lightchain.HasHeader(h, n)
+				}
+				if !known {
 					end = check
 					break
 				}