When resending an eth tx, always increase gas price

Incrementing the gas price unconditionally avoids sending the exact same
transaction, which geth will reject because that transaction already exists in
the pool

coordinator/batch.go

@@ -8,6 +8,7 @@ import (
 	"path"
 	"time"
 
+	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/hermeznetwork/hermez-node/common"
 	"github.com/hermeznetwork/hermez-node/eth"
@@ -90,9 +91,9 @@ type BatchInfo struct {
 	L2Txs                 []common.L2Tx
 	CoordIdxs             []common.Idx
 	ForgeBatchArgs        *eth.RollupForgeBatchArgs
-	// FeesInfo
-	EthTx    *types.Transaction
-	EthTxErr error
+	Auth                  *bind.TransactOpts `json:"-"`
+	EthTx                 *types.Transaction
+	EthTxErr              error
 	// SendTimestamp  the time of batch sent to ethereum
 	SendTimestamp time.Time
 	Receipt       *types.Receipt

coordinator/txmanager.go

@@ -182,19 +182,29 @@ func addPerc(v *big.Int, p int64) *big.Int {
 	r.Mul(r, big.NewInt(p))
 	// nolint reason: to calculate percentages we divide by 100
 	r.Div(r, big.NewInt(100)) //nolit:gomnd
+	// If the increase is 0, force it to be 1 so that a gas increase
+	// doesn't result in the same value, making the transaction to be equal
+	// than before.
+	if r.Cmp(big.NewInt(0)) == 0 {
+		r = big.NewInt(1)
+	}
 	return r.Add(v, r)
 }
 
 func (t *TxManager) sendRollupForgeBatch(ctx context.Context, batchInfo *BatchInfo, resend bool) error {
 	var ethTx *types.Transaction
 	var err error
-	auth, err := t.NewAuth(ctx, batchInfo)
-	if err != nil {
-		return tracerr.Wrap(err)
-	}
-	auth.Nonce = big.NewInt(int64(t.accNextNonce))
+	var auth *bind.TransactOpts
 	if resend {
-		auth.Nonce = big.NewInt(int64(batchInfo.EthTx.Nonce()))
+		auth = batchInfo.Auth
+		auth.GasPrice = addPerc(auth.GasPrice, 10)
+	} else {
+		auth, err = t.NewAuth(ctx, batchInfo)
+		if err != nil {
+			return tracerr.Wrap(err)
+		}
+		batchInfo.Auth = auth
+		auth.Nonce = big.NewInt(int64(t.accNextNonce))
 	}
 	for attempt := 0; attempt < t.cfg.EthClientAttempts; attempt++ {
 		if auth.GasPrice.Cmp(t.cfg.MaxGasPrice) > 0 {