From fb9f19334935fde694ed567c30af4baa2aa0786b Mon Sep 17 00:00:00 2001
From: Giulio rebuffo <giulio.rebuffo@gmail.com>
Date: Mon, 18 Jul 2022 03:04:02 +0200
Subject: [PATCH] fixed Two Block PoW Re-org to Higher-Height Chain (#4730)

Co-authored-by: giuliorebuffo <giuliorebuffo@system76-pc.localdomain>
---
 eth/stagedsync/stage_headers.go   | 11 ++++++++++
 turbo/engineapi/fork_validator.go |  7 +++++++
 turbo/stages/stageloop.go         | 35 ++++++++++++++++---------------
 3 files changed, 36 insertions(+), 17 deletions(-)

diff --git a/eth/stagedsync/stage_headers.go b/eth/stagedsync/stage_headers.go
index bf6ad576a4c..3f2996bf937 100644
--- a/eth/stagedsync/stage_headers.go
+++ b/eth/stagedsync/stage_headers.go
@@ -667,6 +667,8 @@ func schedulePoSDownload(
 func verifyAndSaveDownloadedPoSHeaders(tx kv.RwTx, cfg HeadersCfg, headerInserter *headerdownload.HeaderInserter) {
 	var lastValidHash common.Hash
 	var badChainError error
+	var foundPow bool
+
 	headerLoadFunc := func(key, value []byte, _ etl.CurrentTableReader, _ etl.LoadNextFunc) error {
 		var h types.Header
 		if err := rlp.DecodeBytes(value, &h); err != nil {
@@ -683,6 +685,15 @@ func verifyAndSaveDownloadedPoSHeaders(tx kv.RwTx, cfg HeadersCfg, headerInserte
 			cfg.hd.ReportBadHeaderPoS(h.Hash(), lastValidHash)
 			return nil
 		}
+		// If we are in PoW range then block validation is not required anymore.
+		if foundPow {
+			return headerInserter.FeedHeaderPoS(tx, &h, h.Hash())
+		}
+
+		foundPow = h.Difficulty.Cmp(common.Big0) != 0
+		if foundPow {
+			return headerInserter.FeedHeaderPoS(tx, &h, h.Hash())
+		}
 		// Validate state if possible (bodies will be retrieved through body download)
 		_, _, validationError, criticalError := cfg.forkValidator.ValidatePayload(tx, &h, nil, false)
 		if criticalError != nil {
diff --git a/turbo/engineapi/fork_validator.go b/turbo/engineapi/fork_validator.go
index 91b87b31087..ae83190cd4b 100644
--- a/turbo/engineapi/fork_validator.go
+++ b/turbo/engineapi/fork_validator.go
@@ -15,6 +15,7 @@ package engineapi
 
 import (
 	"bytes"
+	"fmt"
 
 	"github.com/ledgerwatch/erigon-lib/gointerfaces/remote"
 	"github.com/ledgerwatch/erigon-lib/kv"
@@ -130,6 +131,7 @@ func (fv *ForkValidator) ValidatePayload(tx kv.RwTx, header *types.Header, body
 	// if the block is not in range of maxForkDepth from head then we do not validate it.
 	if abs64(int64(fv.currentHeight)-header.Number.Int64()) > maxForkDepth {
 		status = remote.EngineStatus_ACCEPTED
+		fmt.Println("not in range")
 		return
 	}
 	// Let's assemble the side fork backwards
@@ -137,6 +139,7 @@ func (fv *ForkValidator) ValidatePayload(tx kv.RwTx, header *types.Header, body
 	currentHash := header.ParentHash
 	foundCanonical, criticalError = rawdb.IsCanonicalHash(tx, currentHash)
 	if criticalError != nil {
+		fmt.Println("critical")
 		return
 	}
 
@@ -160,6 +163,10 @@ func (fv *ForkValidator) ValidatePayload(tx kv.RwTx, header *types.Header, body
 		}
 		unwindPoint = sb.header.Number.Uint64() - 1
 	}
+	// Do not set an unwind point if we are already there.
+	if unwindPoint == fv.currentHeight {
+		unwindPoint = 0
+	}
 	// if it is not canonical we validate it in memory and discard it aferwards.
 	batch := memdb.NewMemoryBatch(tx)
 	defer batch.Close()
diff --git a/turbo/stages/stageloop.go b/turbo/stages/stageloop.go
index 8a0caa5451f..5280dc8b7e3 100644
--- a/turbo/stages/stageloop.go
+++ b/turbo/stages/stageloop.go
@@ -262,25 +262,26 @@ func StateStep(ctx context.Context, batch kv.RwTx, stateSync *stagedsync.Sync, h
 		if err = stateSync.RunUnwind(nil, batch); err != nil {
 			return err
 		}
-		// Once we unwond we can start constructing the chain (assumption: len(headersChain) == len(bodiesChain))
-		for i := range headersChain {
-			currentHeader := headersChain[i]
-			currentBody := bodiesChain[i]
-			currentHeight := headersChain[i].Number.Uint64()
-			currentHash := headersChain[i].Hash()
-			// Prepare memory state for block execution
-			if err = rawdb.WriteRawBodyIfNotExists(batch, currentHash, currentHeight, currentBody); err != nil {
-				return err
-			}
-			rawdb.WriteHeader(batch, currentHeader)
-			if err = rawdb.WriteHeaderNumber(batch, currentHash, currentHeight); err != nil {
-				return err
-			}
-			if err = rawdb.WriteCanonicalHash(batch, currentHash, currentHeight); err != nil {
-				return err
-			}
+	}
+	// Once we unwond we can start constructing the chain (assumption: len(headersChain) == len(bodiesChain))
+	for i := range headersChain {
+		currentHeader := headersChain[i]
+		currentBody := bodiesChain[i]
+		currentHeight := headersChain[i].Number.Uint64()
+		currentHash := headersChain[i].Hash()
+		// Prepare memory state for block execution
+		if err = rawdb.WriteRawBodyIfNotExists(batch, currentHash, currentHeight, currentBody); err != nil {
+			return err
+		}
+		rawdb.WriteHeader(batch, currentHeader)
+		if err = rawdb.WriteHeaderNumber(batch, currentHash, currentHeight); err != nil {
+			return err
+		}
+		if err = rawdb.WriteCanonicalHash(batch, currentHash, currentHeight); err != nil {
+			return err
 		}
 	}
+
 	// If we did not specify header or body we stop here
 	if header == nil {
 		return nil