cmd/evm: add difficulty calculation to t8n tool

cmd/evm/internal/t8ntool/execution.go

@@ -18,6 +18,7 @@ package t8ntool
 
 import (
 	"fmt"
+	"github.com/ethereum/go-ethereum/consensus/ethash"
 	"math/big"
 	"os"
 
@@ -53,6 +54,7 @@ type ExecutionResult struct {
 	Bloom       types.Bloom    `json:"logsBloom"        gencodec:"required"`
 	Receipts    types.Receipts `json:"receipts"`
 	Rejected    []*rejectedTx  `json:"rejected,omitempty"`
+	Difficulty  *big.Int       `json:"currentDifficulty" gencodec:"required"`
 }
 
 type ommer struct {
@@ -62,23 +64,27 @@ type ommer struct {
 
 //go:generate gencodec -type stEnv -field-override stEnvMarshaling -out gen_stenv.go
 type stEnv struct {
-	Coinbase    common.Address                      `json:"currentCoinbase"   gencodec:"required"`
-	Difficulty  *big.Int                            `json:"currentDifficulty" gencodec:"required"`
-	GasLimit    uint64                              `json:"currentGasLimit"   gencodec:"required"`
-	Number      uint64                              `json:"currentNumber"     gencodec:"required"`
-	Timestamp   uint64                              `json:"currentTimestamp"  gencodec:"required"`
-	BlockHashes map[math.HexOrDecimal64]common.Hash `json:"blockHashes,omitempty"`
-	Ommers      []ommer                             `json:"ommers,omitempty"`
-	BaseFee     *big.Int                            `json:"currentBaseFee,omitempty"`
+	Coinbase         common.Address                      `json:"currentCoinbase"   gencodec:"required"`
+	Difficulty       *big.Int                            `json:"currentDifficulty"`
+	ParentDifficulty *big.Int                            `json:"parentDifficulty"`
+	GasLimit         uint64                              `json:"currentGasLimit"   gencodec:"required"`
+	Number           uint64                              `json:"currentNumber"     gencodec:"required"`
+	Timestamp        uint64                              `json:"currentTimestamp"  gencodec:"required"`
+	ParentTimestamp  uint64                              `json:"parentTimestamp,omitempty"`
+	BlockHashes      map[math.HexOrDecimal64]common.Hash `json:"blockHashes,omitempty"`
+	Ommers           []ommer                             `json:"ommers,omitempty"`
+	BaseFee          *big.Int                            `json:"currentBaseFee,omitempty"`
 }
 
 type stEnvMarshaling struct {
-	Coinbase   common.UnprefixedAddress
-	Difficulty *math.HexOrDecimal256
-	GasLimit   math.HexOrDecimal64
-	Number     math.HexOrDecimal64
-	Timestamp  math.HexOrDecimal64
-	BaseFee    *math.HexOrDecimal256
+	Coinbase         common.UnprefixedAddress
+	Difficulty       *math.HexOrDecimal256
+	ParentDifficulty *math.HexOrDecimal256
+	GasLimit         math.HexOrDecimal64
+	Number           math.HexOrDecimal64
+	Timestamp        math.HexOrDecimal64
+	ParentTimestamp  math.HexOrDecimal64
+	BaseFee          *math.HexOrDecimal256
 }
 
 type rejectedTx struct {
@@ -247,6 +253,7 @@ func (pre *Prestate) Apply(vmConfig vm.Config, chainConfig *params.ChainConfig,
 		LogsHash:    rlpHash(statedb.Logs()),
 		Receipts:    receipts,
 		Rejected:    rejectedTxs,
+		Difficulty:  vmContext.Difficulty,
 	}
 	return statedb, execRs, nil
 }
@@ -274,3 +281,18 @@ func rlpHash(x interface{}) (h common.Hash) {
 	hw.Sum(h[:0])
 	return h
 }
+
+// calcDifficulty is based on ethash.CalcDifficulty. This method is used in case
+// the caller does not provide an explicit difficulty, but instead provides only
+// parent timestamp + difficulty.
+// Note: this method only works for ethash engine.
+func calcDifficulty(config *params.ChainConfig, number, currentTime, parentTime uint64, parentDifficulty *big.Int) *big.Int {
+	parent := &types.Header{
+		ParentHash: common.Hash{},
+		UncleHash:  types.EmptyUncleHash,
+		Difficulty: parentDifficulty,
+		Number:     new(big.Int).SetUint64(number - 1),
+		Time:       parentTime,
+	}
+	return ethash.CalcDifficulty(config, currentTime, parent)
+}

cmd/evm/internal/t8ntool/transition.go

@@ -252,6 +252,18 @@ func Main(ctx *cli.Context) error {
 			return NewError(ErrorVMConfig, errors.New("EIP-1559 config but missing 'currentBaseFee' in env section"))
 		}
 	}
+	if env := prestate.Env; env.Difficulty == nil {
+		// If difficulty was not provided by caller, we need to calculate it.
+		switch {
+		case env.ParentDifficulty == nil:
+			return NewError(ErrorVMConfig, errors.New("currentDifficulty was not provided, and cannot be calculated due to missing parentDifficulty"))
+		case env.Number == 0:
+			return NewError(ErrorVMConfig, errors.New("currentDifficulty needs to be provided for block number 0"))
+		case env.Timestamp == 0:
+			return NewError(ErrorVMConfig, errors.New("currentDifficulty cannot be calculated if time is set to 0"))
+		}
+		prestate.Env.Difficulty = calcDifficulty(chainConfig, env.Number, env.Timestamp, env.ParentTimestamp, env.ParentDifficulty)
+	}
 	// Run the test and aggregate the result
 	s, result, err := prestate.Apply(vmConfig, chainConfig, txs, ctx.Int64(RewardFlag.Name), getTracer)
 	if err != nil {

cmd/evm/testdata/14/alloc.json

@@ -0,0 +1,12 @@
+{
+  "a94f5374fce5edbc8e2a8697c15331677e6ebf0b": {
+    "balance": "0x5ffd4878be161d74",
+    "code": "0x",
+    "nonce": "0xac",
+    "storage": {}
+  },
+  "0x8a8eafb1cf62bfbeb1741769dae1a9dd47996192":{
+    "balance": "0xfeedbead",
+    "nonce" : "0x00"
+  }
+}

cmd/evm/testdata/14/env.json

@@ -0,0 +1,8 @@
+{
+  "currentCoinbase": "0xc94f5374fce5edbc8e2a8697c15331677e6ebf0b",
+  "currentGasLimit": "0x750a163df65e8a",
+  "currentNumber": "12301230",
+  "currentTimestamp": "10000",
+  "parentTimestamp" : "999",
+  "parentDifficulty" : "0x2000"
+}

cmd/evm/testdata/14/readme.md

@@ -0,0 +1,22 @@
+## Difficulty calculation
+
+This test shows how the `evm t8n` can be used to calculate the (ethash) difficulty, if none is provided by the caller. 
+
+```
+./evm t8n --input.alloc=./testdata/14/alloc.json --input.txs=./testdata/14/txs.json --input.env=./testdata/14/env.json --output.result=stdout
+INFO [08-08|16:53:45.535] Trie dumping started                     root=6f0588..7f4bdc
+INFO [08-08|16:53:45.535] Trie dumping complete                    accounts=2 elapsed="75.275µs"
+INFO [08-08|16:53:45.535] Wrote file                               file=alloc.json
+{
+ "result": {
+  "stateRoot": "0x6f058887ca01549716789c380ede95aecc510e6d1fdc4dbf67d053c7c07f4bdc",
+  "txRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+  "receiptRoot": "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
+  "logsHash": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
+  "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+  "receipts": [],
+  "currentDifficulty": 2361183241434822737920
+ }
+}
+```
+

cmd/evm/testdata/14/txs.json

@@ -0,0 +1 @@
+[]