Validate minimum gasPrice and reject if not met

ethchain/transaction_pool.go

@@ -22,6 +22,7 @@ type TxMsgTy byte
 const (
 	TxPre = iota
 	TxPost
+	minGasPrice = 1000000
 )
 
 type TxMsg struct {
@@ -172,6 +173,12 @@ func (pool *TxPool) ValidateTransaction(tx *Transaction) error {
 		return fmt.Errorf("[TXPL] Insufficient amount in sender's (%x) account", tx.Sender())
 	}
 
+	if tx.IsContract() {
+		if tx.GasPrice.Cmp(big.NewInt(minGasPrice)) < 0 {
+			return fmt.Errorf("[TXPL] Gasprice to low, %s given should be at least %d.", tx.GasPrice, minGasPrice)
+		}
+	}
+
 	// Increment the nonce making each tx valid only once to prevent replay
 	// attacks