internal/ethapi: don't set sender-balance to maxuint, fixes #16999 (#20783)

Prior to this change, eth_call changed the balance of the sender account in the
EVM environment to 2^256 wei to cover the gas cost of the call execution.
We've had this behavior for a long time even though it's super confusing.

This commit sets the default call gasprice to zero instead of updating the balance,
which is better because it makes eth_call semantics less surprising. Removing
the built-in balance assignment also makes balance overrides work as expected.

eth/api_backend.go

@@ -23,7 +23,6 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/bloombits"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -191,7 +190,6 @@ func (b *EthAPIBackend) GetTd(blockHash common.Hash) *big.Int {
 }
 
 func (b *EthAPIBackend) GetEVM(ctx context.Context, msg core.Message, state *state.StateDB, header *types.Header) (*vm.EVM, func() error, error) {
-	state.SetBalance(msg.From(), math.MaxBig256)
 	vmError := func() error { return nil }
 
 	context := core.NewEVMContext(msg, header, b.eth.BlockChain(), nil)

internal/ethapi/api.go

@@ -47,10 +47,6 @@ import (
 	"github.com/tyler-smith/go-bip39"
 )
 
-const (
-	defaultGasPrice = params.GWei
-)
-
 // PublicEthereumAPI provides an API to access Ethereum related information.
 // It offers only methods that operate on public data that is freely available to anyone.
 type PublicEthereumAPI struct {
@@ -808,7 +804,7 @@ func DoCall(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.Blo
 		log.Warn("Caller gas above allowance, capping", "requested", gas, "cap", globalGasCap)
 		gas = globalGasCap.Uint64()
 	}
-	gasPrice := new(big.Int).SetUint64(defaultGasPrice)
+	gasPrice := new(big.Int)
 	if args.GasPrice != nil {
 		gasPrice = args.GasPrice.ToInt()
 	}

les/api_backend.go

@@ -23,7 +23,6 @@ import (
 
 	"github.com/ethereum/go-ethereum/accounts"
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/bloombits"
 	"github.com/ethereum/go-ethereum/core/rawdb"
@@ -168,7 +167,6 @@ func (b *LesApiBackend) GetTd(hash common.Hash) *big.Int {
 }
 
 func (b *LesApiBackend) GetEVM(ctx context.Context, msg core.Message, state *state.StateDB, header *types.Header) (*vm.EVM, func() error, error) {
-	state.SetBalance(msg.From(), math.MaxBig256)
 	context := core.NewEVMContext(msg, header, b.eth.blockchain, nil)
 	return vm.NewEVM(context, state, b.eth.chainConfig, vm.Config{}), state.Error, nil
 }