core/stateless: API methods to get execution witness of block

This PR adds a new RPC call, which re-executes a block with stateless
mode activated, so that the witness data are collected and returned.

They are `debug_executionWitnessByHash` which takes in a block hash
and `debug_executionWitness` which takes in a block number.

---------

Signed-off-by: Guillaume Ballet <[email protected]>

Author: gballet

core/blockchain.go

@@ -1907,7 +1907,7 @@ func (bc *BlockChain) insertChain(chain types.Blocks, setHead bool, makeWitness
 		}
 		// The traced section of block import.
 		start := time.Now()
-		res, err := bc.processBlock(parent.Root, block, setHead, makeWitness && len(chain) == 1)
+		res, err := bc.ProcessBlock(parent.Root, block, setHead, makeWitness && len(chain) == 1)
 		if err != nil {
 			return nil, it.index, err
 		}
@@ -1973,9 +1973,13 @@ type blockProcessingResult struct {
 	witness  *stateless.Witness
 }
 
-// processBlock executes and validates the given block. If there was no error
+func (bpr *blockProcessingResult) Witness() *stateless.Witness {
+	return bpr.witness
+}
+
+// ProcessBlock executes and validates the given block. If there was no error
 // it writes the block and associated state to database.
-func (bc *BlockChain) processBlock(parentRoot common.Hash, block *types.Block, setHead bool, makeWitness bool) (_ *blockProcessingResult, blockEndErr error) {
+func (bc *BlockChain) ProcessBlock(parentRoot common.Hash, block *types.Block, setHead bool, makeWitness bool) (_ *blockProcessingResult, blockEndErr error) {
 	var (
 		err       error
 		startTime = time.Now()

core/stateless/encoding.go

@@ -19,28 +19,29 @@ package stateless
 import (
 	"io"
 
+	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
-// toExtWitness converts our internal witness representation to the consensus one.
-func (w *Witness) toExtWitness() *extWitness {
-	ext := &extWitness{
+// ToExtWitness converts our internal witness representation to the consensus one.
+func (w *Witness) ToExtWitness() *ExtWitness {
+	ext := &ExtWitness{
 		Headers: w.Headers,
 	}
-	ext.Codes = make([][]byte, 0, len(w.Codes))
+	ext.Codes = make([]hexutil.Bytes, 0, len(w.Codes))
 	for code := range w.Codes {
 		ext.Codes = append(ext.Codes, []byte(code))
 	}
-	ext.State = make([][]byte, 0, len(w.State))
+	ext.State = make([]hexutil.Bytes, 0, len(w.State))
 	for node := range w.State {
 		ext.State = append(ext.State, []byte(node))
 	}
 	return ext
 }
 
 // fromExtWitness converts the consensus witness format into our internal one.
-func (w *Witness) fromExtWitness(ext *extWitness) error {
+func (w *Witness) fromExtWitness(ext *ExtWitness) error {
 	w.Headers = ext.Headers
 
 	w.Codes = make(map[string]struct{}, len(ext.Codes))
@@ -56,21 +57,22 @@ func (w *Witness) fromExtWitness(ext *extWitness) error {
 
 // EncodeRLP serializes a witness as RLP.
 func (w *Witness) EncodeRLP(wr io.Writer) error {
-	return rlp.Encode(wr, w.toExtWitness())
+	return rlp.Encode(wr, w.ToExtWitness())
 }
 
 // DecodeRLP decodes a witness from RLP.
 func (w *Witness) DecodeRLP(s *rlp.Stream) error {
-	var ext extWitness
+	var ext ExtWitness
 	if err := s.Decode(&ext); err != nil {
 		return err
 	}
 	return w.fromExtWitness(&ext)
 }
 
-// extWitness is a witness RLP encoding for transferring across clients.
-type extWitness struct {
-	Headers []*types.Header
-	Codes   [][]byte
-	State   [][]byte
+// ExtWitness is a witness RLP encoding for transferring across clients.
+type ExtWitness struct {
+	Headers []*types.Header `json:"headers"`
+	Codes   []hexutil.Bytes `json:"codes"`
+	State   []hexutil.Bytes `json:"state"`
+	Keys    []hexutil.Bytes `json:"keys"`
 }

core/stateless/witness.go

@@ -100,6 +100,10 @@ func (w *Witness) AddState(nodes map[string][]byte) {
 	}
 }
 
+func (w *Witness) AddKey() {
+	panic("not yet implemented")
+}
+
 // Copy deep-copies the witness object.  Witness.Block isn't deep-copied as it
 // is never mutated by Witness
 func (w *Witness) Copy() *Witness {

eth/api_debug.go

@@ -26,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/rawdb"
 	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/stateless"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/internal/ethapi"
@@ -491,3 +492,43 @@ func (api *DebugAPI) StateSize(blockHashOrNumber *rpc.BlockNumberOrHash) (interf
 		"contractCodeBytes":    hexutil.Uint64(stats.ContractCodeBytes),
 	}, nil
 }
+
+func (api *DebugAPI) ExecutionWitness(bn rpc.BlockNumber) (*stateless.ExtWitness, error) {
+	bc := api.eth.blockchain
+	block, err := api.eth.APIBackend.BlockByNumber(context.Background(), bn)
+	if err != nil {
+		return &stateless.ExtWitness{}, fmt.Errorf("block number %v not found", bn)
+	}
+
+	parent := bc.GetHeader(block.ParentHash(), block.NumberU64()-1)
+	if parent == nil {
+		return &stateless.ExtWitness{}, fmt.Errorf("block number %v found, but parent missing", bn)
+	}
+
+	result, err := bc.ProcessBlock(parent.Root, block, false, true)
+	if err != nil {
+		return nil, err
+	}
+
+	return result.Witness().ToExtWitness(), nil
+}
+
+func (api *DebugAPI) ExecutionWitnessByHash(hash common.Hash) (*stateless.ExtWitness, error) {
+	bc := api.eth.blockchain
+	block := bc.GetBlockByHash(hash)
+	if block == nil {
+		return &stateless.ExtWitness{}, fmt.Errorf("block hash %x not found", hash)
+	}
+
+	parent := bc.GetHeader(block.ParentHash(), block.NumberU64()-1)
+	if parent == nil {
+		return &stateless.ExtWitness{}, fmt.Errorf("block number %x found, but parent missing", hash)
+	}
+
+	result, err := bc.ProcessBlock(parent.Root, block, false, true)
+	if err != nil {
+		return nil, err
+	}
+
+	return result.Witness().ToExtWitness(), nil
+}