internal/ethapi: add eth_baseFee RPC method (#34904)

This method is similar to `eth_blobBaseFee` but returns the next base
fee.

eth/api_backend.go

@@ -26,6 +26,7 @@ import (
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus"
+	"github.com/ethereum/go-ethereum/consensus/misc/eip1559"
 	"github.com/ethereum/go-ethereum/consensus/misc/eip4844"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/filtermaps"
@@ -430,6 +431,13 @@ func (b *EthAPIBackend) FeeHistory(ctx context.Context, blockCount uint64, lastB
 	return b.gpo.FeeHistory(ctx, blockCount, lastBlock, rewardPercentiles)
 }
 
+func (b *EthAPIBackend) BaseFee(ctx context.Context) *big.Int {
+	if b.ChainConfig().IsLondon(b.CurrentHeader().Number) {
+		return eip1559.CalcBaseFee(b.ChainConfig(), b.CurrentHeader())
+	}
+	return nil
+}
+
 func (b *EthAPIBackend) BlobBaseFee(ctx context.Context) *big.Int {
 	if excess := b.CurrentHeader().ExcessBlobGas; excess != nil {
 		return eip4844.CalcBlobFee(b.ChainConfig(), b.CurrentHeader())

internal/ethapi/api.go

@@ -146,6 +146,11 @@ func (api *EthereumAPI) BlobBaseFee(ctx context.Context) *hexutil.Big {
 	return (*hexutil.Big)(api.b.BlobBaseFee(ctx))
 }
 
+// BaseFee returns the base fee for the next block.
+func (api *EthereumAPI) BaseFee(ctx context.Context) *hexutil.Big {
+	return (*hexutil.Big)(api.b.BaseFee(ctx))
+}
+
 // Syncing returns false in case the node is currently not syncing with the network. It can be up-to-date or has not
 // yet received the latest block headers from its peers. In case it is synchronizing:
 // - startingBlock: block number this node started to synchronize from

internal/ethapi/api_test.go

@@ -500,6 +500,7 @@ func (b testBackend) FeeHistory(ctx context.Context, blockCount uint64, lastBloc
 	return nil, nil, nil, nil, nil, nil, nil
 }
 func (b testBackend) BlobBaseFee(ctx context.Context) *big.Int { return new(big.Int) }
+func (b testBackend) BaseFee(ctx context.Context) *big.Int     { return new(big.Int) }
 func (b testBackend) ChainDb() ethdb.Database                  { return b.db }
 func (b testBackend) AccountManager() *accounts.Manager        { return b.accman }
 func (b testBackend) ExtRPCEnabled() bool                      { return false }

internal/ethapi/backend.go

@@ -46,6 +46,7 @@ type Backend interface {
 	SuggestGasTipCap(ctx context.Context) (*big.Int, error)
 	FeeHistory(ctx context.Context, blockCount uint64, lastBlock rpc.BlockNumber, rewardPercentiles []float64) (*big.Int, [][]*big.Int, []*big.Int, []float64, []*big.Int, []float64, error)
 	BlobBaseFee(ctx context.Context) *big.Int
+	BaseFee(ctx context.Context) *big.Int
 	ChainDb() ethdb.Database
 	AccountManager() *accounts.Manager
 	ExtRPCEnabled() bool

internal/ethapi/transaction_args_test.go

@@ -318,6 +318,7 @@ func (b *backendMock) SuggestGasTipCap(ctx context.Context) (*big.Int, error) {
 	return big.NewInt(42), nil
 }
 func (b *backendMock) BlobBaseFee(ctx context.Context) *big.Int { return big.NewInt(42) }
+func (b *backendMock) BaseFee(ctx context.Context) *big.Int     { return big.NewInt(42) }
 
 func (b *backendMock) CurrentHeader() *types.Header     { return b.current }
 func (b *backendMock) ChainConfig() *params.ChainConfig { return b.config }