Implementing basic unwind process for Proof-of-stake (#3083)

* initial commmit

* gofmt

* flipped if statement

* flipped if statement (forgot to save)

* passing unwinding to status ch

* added unwinding constant

* took out unwinding

* added statusCh

* added a return statement and a second part to the if statement

* checking for parent hash

* checking for parent hash

* changed check to check for parentHash

* staged wrong file

* changed header check to parentHash check

* channged blockhash name to a better name

* changed it to check for header.Hash()

* changed name of blocknumber to blockHash

* changed bad block to common.Hash{}

eth/stagedsync/stage_headers.go

@@ -18,6 +18,7 @@ import (
 	"github.com/ledgerwatch/erigon/core/rawdb"
 	"github.com/ledgerwatch/erigon/core/types"
 	"github.com/ledgerwatch/erigon/eth/stagedsync/stages"
+	"github.com/ledgerwatch/erigon/ethdb/privateapi"
 	"github.com/ledgerwatch/erigon/p2p/enode"
 	"github.com/ledgerwatch/erigon/params"
 	"github.com/ledgerwatch/erigon/rlp"
@@ -30,6 +31,7 @@ import (
 type HeadersCfg struct {
 	db                kv.RwDB
 	hd                *headerdownload.HeaderDownload
+	statusCh          chan privateapi.ExecutionStatus
 	chainConfig       params.ChainConfig
 	headerReqSend     func(context.Context, *headerdownload.HeaderRequest) (enode.ID, bool)
 	announceNewHashes func(context.Context, []headerdownload.Announce)
@@ -45,6 +47,7 @@ type HeadersCfg struct {
 func StageHeadersCfg(
 	db kv.RwDB,
 	headerDownload *headerdownload.HeaderDownload,
+	statusCh chan privateapi.ExecutionStatus,
 	chainConfig params.ChainConfig,
 	headerReqSend func(context.Context, *headerdownload.HeaderRequest) (enode.ID, bool),
 	announceNewHashes func(context.Context, []headerdownload.Announce),
@@ -59,6 +62,7 @@ func StageHeadersCfg(
 	return HeadersCfg{
 		db:                db,
 		hd:                headerDownload,
+		statusCh:          statusCh,
 		chainConfig:       chainConfig,
 		headerReqSend:     headerReqSend,
 		announceNewHashes: announceNewHashes,
@@ -127,7 +131,25 @@ func HeadersDownward(
 	log.Info("Waiting for payloads...")
 	header := <-cfg.reverseDownloadCh
 	*cfg.waitingPosHeaders = false
+
+	defer tx.Commit()
+
+	headerNumber := header.Number.Uint64()
+
+	blockHash, err := rawdb.ReadCanonicalHash(tx, headerNumber)
+	if err != nil {
+		return err
+	}
+
 	// Do we need to unwind? (TODO)
+	if s.BlockNumber >= headerNumber && header.Hash() != blockHash {
+		u.UnwindTo(headerNumber-1, common.Hash{})
+		cfg.statusCh <- privateapi.ExecutionStatus{
+			HeadHash: header.ParentHash,
+			Status:   privateapi.Syncing,
+		}
+		return nil
+	}
 
 	// Write current payload
 	rawdb.WriteHeader(tx, &header)

turbo/stages/mock_sentry.go

@@ -275,6 +275,7 @@ func MockWithEverything(t *testing.T, gspec *core.Genesis, key *ecdsa.PrivateKey
 		stagedsync.DefaultStages(mock.Ctx, prune, stagedsync.StageHeadersCfg(
 			mock.DB,
 			mock.downloader.Hd,
+			make(chan privateapi.ExecutionStatus),
 			*mock.ChainConfig,
 			sendHeaderRequest,
 			propagateNewBlockHashes,

turbo/stages/stageloop.go

@@ -244,6 +244,7 @@ func NewStagedSync(
 		stagedsync.DefaultStages(ctx, cfg.Prune, stagedsync.StageHeadersCfg(
 			db,
 			controlServer.Hd,
+			statusCh,
 			*controlServer.ChainConfig,
 			controlServer.SendHeaderRequest,
 			controlServer.PropagateNewBlockHashes,