cmd/utils: validate pre-existing genesis in --dev mode (#28468)

geth --dev can be used with an existing data directory and genesis block. Since
dev mode only works with PoS, we need to verify that the merge has happened.

Co-authored-by: Felix Lange <fjl@twurst.com>

cmd/utils/flags.go

@@ -1870,6 +1870,21 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
 			chaindb := tryMakeReadOnlyDatabase(ctx, stack)
 			if rawdb.ReadCanonicalHash(chaindb, 0) != (common.Hash{}) {
 				cfg.Genesis = nil // fallback to db content
+
+				//validate genesis has PoS enabled in block 0
+				genesis, err := core.ReadGenesis(chaindb)
+				if err != nil {
+					Fatalf("Could not read genesis from database: %v", err)
+				}
+				if !genesis.Config.TerminalTotalDifficultyPassed {
+					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficultyPassed must be true in developer mode")
+				}
+				if genesis.Config.TerminalTotalDifficulty == nil {
+					Fatalf("Bad developer-mode genesis configuration: terminalTotalDifficulty must be specified.")
+				}
+				if genesis.Difficulty.Cmp(genesis.Config.TerminalTotalDifficulty) != 1 {
+					Fatalf("Bad developer-mode genesis configuration: genesis block difficulty must be > terminalTotalDifficulty")
+				}
 			}
 			chaindb.Close()
 		}

core/genesis.go

@@ -589,7 +589,7 @@ func DeveloperGenesisBlock(gasLimit uint64, faucet common.Address) *Genesis {
 		Config:     &config,
 		GasLimit:   gasLimit,
 		BaseFee:    big.NewInt(params.InitialBaseFee),
-		Difficulty: big.NewInt(0),
+		Difficulty: big.NewInt(1),
 		Alloc: map[common.Address]GenesisAccount{
 			common.BytesToAddress([]byte{1}): {Balance: big.NewInt(1)}, // ECRecover
 			common.BytesToAddress([]byte{2}): {Balance: big.NewInt(1)}, // SHA256

eth/catalyst/simulated_beacon.go

@@ -82,10 +82,6 @@ type SimulatedBeacon struct {
 }
 
 func NewSimulatedBeacon(period uint64, eth *eth.Ethereum) (*SimulatedBeacon, error) {
-	chainConfig := eth.APIBackend.ChainConfig()
-	if !chainConfig.IsDevMode {
-		return nil, errors.New("incompatible pre-existing chain configuration")
-	}
 	block := eth.BlockChain().CurrentBlock()
 	current := engine.ForkchoiceStateV1{
 		HeadBlockHash:      block.Hash(),

params/config.go

@@ -180,7 +180,6 @@ var (
 		ShanghaiTime:                  newUint64(0),
 		TerminalTotalDifficulty:       big.NewInt(0),
 		TerminalTotalDifficultyPassed: true,
-		IsDevMode:                     true,
 	}
 
 	// AllCliqueProtocolChanges contains every protocol change (EIPs) introduced
@@ -331,7 +330,6 @@ type ChainConfig struct {
 	// Various consensus engines
 	Ethash *EthashConfig `json:"ethash,omitempty"`
 	Clique *CliqueConfig `json:"clique,omitempty"`
-	IsDevMode bool          `json:"isDev,omitempty"`
 }
 
 // EthashConfig is the consensus engine configs for proof-of-work based sealing.