Add bor.isValidatorAction and call it while validating underpriced tx

consensus/bor/bor.go

@@ -1218,6 +1218,24 @@ func (c *Bor) CommitStates(
 	return nil
 }
 
+func (c *Bor) isValidatorAction(chain consensus.ChainReader, from common.Address, tx *types.Transaction) bool {
+	header := chain.CurrentHeader()
+	snap, err := c.snapshot(chain, header.Number.Uint64(), header.Hash(), nil)
+	if err != nil {
+		log.Error("Failed fetching snapshot", err)
+	}
+
+	_isValidatorAction := false
+	for _, validator := range snap.ValidatorSet.Validators {
+		if bytes.Compare(validator.Address.Bytes(), from.Bytes()) == 0 {
+			_isValidatorAction = true
+			break
+		}
+	}
+	// @todo only either of proposeState and proposeSpan should pass this check
+	return _isValidatorAction
+}
+
 //
 // Private methods
 //

core/tx_pool.go

@@ -27,6 +27,7 @@ import (
 
 	"github.com/maticnetwork/bor/common"
 	"github.com/maticnetwork/bor/common/prque"
+	"github.com/maticnetwork/bor/consensus"
 	"github.com/maticnetwork/bor/core/state"
 	"github.com/maticnetwork/bor/core/types"
 	"github.com/maticnetwork/bor/event"
@@ -116,14 +117,22 @@ const (
 	TxStatusIncluded
 )
 
+// bor acts as a way to be able to type cast consensus.Engine;
+// since importing "github.com/maticnetwork/bor/consensus/bor" results in a cyclic dependency
+type bor interface {
+	isValidatorAction(chain consensus.ChainReader, from common.Address, tx *types.Transaction) bool
+}
+
 // blockChain provides the state of blockchain and current gas limit to do
 // some pre checks in tx pool and event subscribers.
 type blockChain interface {
 	CurrentBlock() *types.Block
 	GetBlock(hash common.Hash, number uint64) *types.Block
 	StateAt(root common.Hash) (*state.StateDB, error)
-
 	SubscribeChainHeadEvent(ch chan<- ChainHeadEvent) event.Subscription
+
+	Engine() consensus.Engine
+	CurrentHeader() *types.Header
 }
 
 // TxPoolConfig are the configuration parameters of the transaction pool.
@@ -527,7 +536,9 @@ func (pool *TxPool) validateTx(tx *types.Transaction, local bool) error {
 	}
 	// Drop non-local transactions under our own minimal accepted gas price
 	local = local || pool.locals.contains(from) // account may be local even if the transaction arrived from the network
-	if !local && pool.gasPrice.Cmp(tx.GasPrice()) > 0 {
+	if !local &&
+		!pool.chain.Engine().(bor).isValidatorAction(pool.chain.(consensus.ChainReader), from, tx) &&
+		pool.gasPrice.Cmp(tx.GasPrice()) > 0 {
 		return ErrUnderpriced
 	}
 	// Ensure the transaction adheres to nonce ordering