net/i40e: issue with ADD VLAN from Guest

Reset the configuration of vlan strip that would be change by the pf kernel driver when adding vlan from vf. Application cannot use rte_eth_dev_set_vlan_offload() to set the VLAN_STRIP, as this will only work for the first time when original and current config mismatch, but for all subsequent call it will be ignored.

---
v2:
* Simplied the commit log.
* goto err; is not required as it has only one more return path and there is no cleanup required apart from just return err.
* Updated the comment start from /* -> /**
* Changed the error log in case vlan strip command fails.

---
 drivers/net/i40e/i40e_ethdev_vf.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

index c26b036..a00e290 100644
@@ -1078,8 +1078,19 @@ i40evf_add_vlan(struct rte_eth_dev *dev, uint16_t vlanid)
 	args.out_buffer = vf->aq_resp;
 	args.out_size = I40E_AQ_BUF_SZ;
 	err = i40evf_execute_vf_cmd(dev, &args);
-	if (err)
+	if (err) {
 		PMD_DRV_LOG(ERR, "fail to execute command OP_ADD_VLAN");
+		return err;
+	}
+	/**
+	 * In linux kernel driver on receiving ADD_VLAN it enables
+	 * VLAN_STRIP by default. So reconfigure the vlan_offload
+	 * as it was done by the app earlier.
+	 */
+	err = i40evf_vlan_offload_set(dev, ETH_VLAN_STRIP_MASK)
+	if (err)
+		PMD_DRV_LOG(ERR, "fail to set vlan_strip "
+			"as a part of OP_ADD_VLAN");
 
 	return err;
 }

2.9.3.windows.1