Add support for legacy fee mode (#153)

Author: hazim-j

pkg/entrypoint/transaction/handleops.go

@@ -91,17 +91,12 @@ func HandleOps(
 	if err != nil {
 		return nil, nil, err
 	}
-	tip, err := eth.SuggestGasTipCap(context.Background())
-	if err != nil {
-		return nil, nil, err
-	}
 
 	auth, err := bind.NewKeyedTransactorWithChainID(eoa.PrivateKey, chainID)
 	if err != nil {
 		return nil, nil, err
 	}
 	auth.GasLimit = gas
-	auth.GasTipCap = tip
 
 	txn, err = ep.HandleOps(auth, toAbiType(batch), beneficiary)
 	if err != nil {
@@ -131,19 +126,14 @@ func CreateRawHandleOps(
 	if err != nil {
 		return "", err
 	}
-	tip, err := eth.SuggestGasTipCap(context.Background())
-	if err != nil {
-		return "", err
-	}
 
 	auth, err := bind.NewKeyedTransactorWithChainID(eoa.PrivateKey, chainID)
 	if err != nil {
 		return "", err
 	}
 	auth.GasLimit = gas
-	auth.GasTipCap = tip
-	auth.GasFeeCap = big.NewInt(0).Add(baseFee, tip)
 	auth.NoSend = true
+
 	tx, err := ep.HandleOps(auth, toAbiType(batch), beneficiary)
 	if err != nil {
 		return "", err

pkg/modules/checks/gasfee.go

@@ -7,13 +7,22 @@ import (
 )
 
 // ValidateFeePerGas checks the maxFeePerGas is sufficiently high to be included with the current
-// block.basefee.
+// block.basefee. Alternatively, if basefee is not supported, then check that maxPriorityFeePerGas is equal to
+// maxFeePerGas as a fallback.
 func ValidateFeePerGas(op *userop.UserOperation, gbf GetBaseFeeFunc) error {
 	bf, err := gbf()
 	if err != nil {
 		return err
 	}
 
+	if bf == nil {
+		if op.MaxPriorityFeePerGas.Cmp(op.MaxFeePerGas) != 0 {
+			return fmt.Errorf("legacy fee mode: maxPriorityFeePerGas must equal maxFeePerGas")
+		}
+
+		return nil
+	}
+
 	if op.MaxFeePerGas.Cmp(bf) < 0 {
 		return fmt.Errorf("maxFeePerGas: must be equal to or greater than current block.basefee")
 	}