sfc: validate MAE action order

Currently the only actions supported are COUNT and DELIVER, which can only
 happen in the right order; but when more actions are added, it will be
 necessary to check that they are only used in the same order in which the
 hardware performs them (since the hardware API takes an action *set* in
 which the order is implicit).  For instance, a VLAN pop must not follow a
 VLAN push.  Most practical use-cases should be unaffected by these
 restrictions.
Add a function efx_tc_flower_action_order_ok() that checks whether it is
 appropriate to add a specified action to the existing action-set.
Signed-off-by: Edward Cree <ecree.xilinx@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/tc.c

@@ -284,6 +284,29 @@ static int efx_tc_flower_parse_match(struct efx_nic *efx,
 	return 0;
 }
 
+/* For details of action order constraints refer to SF-123102-TC-1§12.6.1 */
+enum efx_tc_action_order {
+	EFX_TC_AO_COUNT,
+	EFX_TC_AO_DELIVER
+};
+/* Determine whether we can add @new action without violating order */
+static bool efx_tc_flower_action_order_ok(const struct efx_tc_action_set *act,
+					  enum efx_tc_action_order new)
+{
+	switch (new) {
+	case EFX_TC_AO_COUNT:
+		if (act->count)
+			return false;
+		fallthrough;
+	case EFX_TC_AO_DELIVER:
+		return !act->deliver;
+	default:
+		/* Bad caller.  Whatever they wanted to do, say they can't. */
+		WARN_ON_ONCE(1);
+		return false;
+	}
+}
+
 static int efx_tc_flower_replace(struct efx_nic *efx,
 				 struct net_device *net_dev,
 				 struct flow_cls_offload *tc,
@@ -383,6 +406,25 @@ static int efx_tc_flower_replace(struct efx_nic *efx,
 		     fa->id == FLOW_ACTION_DROP) && fa->hw_stats) {
 			struct efx_tc_counter_index *ctr;
 
+			/* Currently the only actions that want stats are
+			 * mirred and gact (ok, shot, trap, goto-chain), which
+			 * means we want stats just before delivery.  Also,
+			 * note that tunnel_key set shouldn't change the length
+			 * — it's only the subsequent mirred that does that,
+			 * and the stats are taken _before_ the mirred action
+			 * happens.
+			 */
+			if (!efx_tc_flower_action_order_ok(act, EFX_TC_AO_COUNT)) {
+				/* All supported actions that count either steal
+				 * (gact shot, mirred redirect) or clone act
+				 * (mirred mirror), so we should never get two
+				 * count actions on one action_set.
+				 */
+				NL_SET_ERR_MSG_MOD(extack, "Count-action conflict (can't happen)");
+				rc = -EOPNOTSUPP;
+				goto release;
+			}
+
 			if (!(fa->hw_stats & FLOW_ACTION_HW_STATS_DELAYED)) {
 				NL_SET_ERR_MSG_FMT_MOD(extack, "hw_stats_type %u not supported (only 'delayed')",
 						       fa->hw_stats);
@@ -413,6 +455,14 @@ static int efx_tc_flower_replace(struct efx_nic *efx,
 		case FLOW_ACTION_REDIRECT:
 		case FLOW_ACTION_MIRRED:
 			save = *act;
+
+			if (!efx_tc_flower_action_order_ok(act, EFX_TC_AO_DELIVER)) {
+				/* can't happen */
+				rc = -EOPNOTSUPP;
+				NL_SET_ERR_MSG_MOD(extack, "Deliver action violates action order (can't happen)");
+				goto release;
+			}
+
 			to_efv = efx_tc_flower_lookup_efv(efx, fa->dev);
 			if (IS_ERR(to_efv)) {
 				NL_SET_ERR_MSG_MOD(extack, "Mirred egress device not on switch");