openvswitch: Fix push/pop ethernet validation

When there are both pop and push ethernet header actions among the
actions to be applied to a packet, an unexpected EINVAL (Invalid
argument) error is obtained. This is due to mac_proto not being reset
correctly when those actions are validated.

Reported-at:
https://mail.openvswitch.org/pipermail/ovs-discuss/2018-October/047554.html
Fixes: 91820da6 ("openvswitch: add Ethernet push and pop actions")
Signed-off-by: NJaime Caamaño Ruiz <jcaamano@suse.com>
Tested-by: NGreg Rose <gvrose8192@gmail.com>
Reviewed-by: NGreg Rose <gvrose8192@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/openvswitch/flow_netlink.c

@@ -3030,7 +3030,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
 			 * is already present */
 			if (mac_proto != MAC_PROTO_NONE)
 				return -EINVAL;
-			mac_proto = MAC_PROTO_NONE;
+			mac_proto = MAC_PROTO_ETHERNET;
 			break;
 
 		case OVS_ACTION_ATTR_POP_ETH:
@@ -3038,7 +3038,7 @@ static int __ovs_nla_copy_actions(struct net *net, const struct nlattr *attr,
 				return -EINVAL;
 			if (vlan_tci & htons(VLAN_TAG_PRESENT))
 				return -EINVAL;
-			mac_proto = MAC_PROTO_ETHERNET;
+			mac_proto = MAC_PROTO_NONE;
 			break;
 
 		case OVS_ACTION_ATTR_PUSH_NSH: