blockchain: don't assign header as the best tip on

maybeAcceptBlockHeader

maybeAcceptBlockHeader verified the passed in block header and set it as
the best tip on it passing verification. However, since the best tip is
used for marking a block that's passed all verification and headers
verification isn't complete verification, we remove the code for adding
the blockNode as the best tip.

This allows us to use the ProcessBlockHeader code for verification of a
header without accepting it as well.

blockchain/accept.go

@@ -172,7 +172,5 @@ func (b *BlockChain) maybeAcceptBlockHeader(header *wire.BlockHeader, checkHeade
 	newNode := newBlockNode(header, prevNode)
 	b.index.AddNode(newNode)
 
-	// This node is now the end of the best chain.
-	b.bestChain.SetTip(newNode)
 	return newNode, nil
 }

netsync/manager.go

@@ -1092,6 +1092,7 @@ func (sm *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
 
 	if sm.headersBuildMode {
 		var finalHeader *wire.BlockHeader
+		var finalHeight int32
 		for _, blockHeader := range msg.Headers {
 			finalHeader = blockHeader
 
@@ -1103,31 +1104,29 @@ func (sm *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
 				peer.Disconnect()
 				return
 			}
+
+			prevNodeEl := sm.headerList.Back()
+			prevNode := prevNodeEl.Value.(*headerNode)
+
+			if prevNode.hash.IsEqual(&blockHeader.PrevBlock) {
+				hash := blockHeader.BlockHash()
+				node := headerNode{height: prevNode.height + 1, hash: &hash}
+				finalHeight = node.height
+				sm.headerList.PushBack(&node)
+			}
 		}
 
 		finalHash := finalHeader.BlockHash()
-		finalHeight, err := sm.chain.BlockHeightByHash(&finalHash)
-		if err != nil {
-			log.Warnf("Failed to grab block height for last block hash "+
-				"%v. %v.", finalHash.String(), err)
-			return
-		}
 
 		// We're now done downloading headers at this point.
 		if finalHeight >= sm.chain.AssumeUtreexoHeight() {
-			assumeUtreexoHeight := sm.chain.AssumeUtreexoHeight()
-			indexHash, err := sm.chain.BlockHashByHeight(assumeUtreexoHeight)
-			if err != nil {
-				log.Warnf("Failed to grab block height for last block hash "+
-					"%v. %v.", finalHash.String(), err)
-				return
-			}
-			if sm.chain.AssumeUtreexoHash() != *indexHash {
-				log.Warnf("The nodea had hash %v hardcoded in but the valid proof-of-work "+
+			assumeUtreexoHash := sm.chain.AssumeUtreexoHash()
+			if !finalHash.IsEqual(&assumeUtreexoHash) {
+				log.Warnf("The node had hash %v hardcoded in but the valid proof-of-work "+
 					"chain has the hash %v at height %v. The user should not trust this "+
 					"software as genuine and there may be attempts to steal funds. The user "+
-					"should delete the datadir at %v ", sm.chain.AssumeUtreexoHash().String(),
-					indexHash.String(), assumeUtreexoHeight)
+					"should delete the datadir", sm.chain.AssumeUtreexoHash().String(),
+					finalHash.String(), finalHeight)
 				os.Exit(1)
 			}
 
@@ -1147,7 +1146,7 @@ func (sm *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
 				"at block %v(%d)", bestState.Hash.String(), bestState.Height)
 
 			locator := blockchain.BlockLocator([]*chainhash.Hash{&bestState.Hash})
-			err = peer.PushGetBlocksMsg(locator, &zeroHash)
+			err := peer.PushGetBlocksMsg(locator, &zeroHash)
 			if err != nil {
 				log.Warnf("Failed to send getblocks message to "+
 					"peer %s: %v", peer.Addr(), err)
@@ -1162,7 +1161,7 @@ func (sm *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
 		// next checkpoint.
 		locator := blockchain.BlockLocator([]*chainhash.Hash{&finalHash})
 		stopHash := sm.chain.AssumeUtreexoHash()
-		err = peer.PushGetHeadersMsg(locator, &stopHash)
+		err := peer.PushGetHeadersMsg(locator, &stopHash)
 		if err != nil {
 			log.Warnf("Failed to send getheaders message to "+
 				"peer %s: %v", peer.Addr(), err)