net/mlx5: DR, Ignore modify TTL if device doesn't support it

When modifying TTL, packet's csum has to be recalculated.
Due to HW issue in ConnectX-5, csum recalculation for modify TTL
is supported through a work-around that is specifically enabled
by configuration.
If the work-around isn't enabled, ignore the modify TTL action
rather than adding an unsupported action.
Signed-off-by: Yevgeny Kliteynik <kliteyn@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/steering/dr_action.c

@@ -1560,6 +1560,12 @@ dr_action_modify_check_is_ttl_modify(const void *sw_action)
 	return sw_field == MLX5_ACTION_IN_FIELD_OUT_IP_TTL;
 }
 
+static bool dr_action_modify_ttl_ignore(struct mlx5dr_domain *dmn)
+{
+	return !mlx5dr_ste_supp_ttl_cs_recalc(&dmn->info.caps) &&
+	       !MLX5_CAP_ESW_FLOWTABLE(dmn->mdev, fdb_ipv4_ttl_modify);
+}
+
 static int dr_actions_convert_modify_header(struct mlx5dr_action *action,
 					    u32 max_hw_actions,
 					    u32 num_sw_actions,
@@ -1591,8 +1597,13 @@ static int dr_actions_convert_modify_header(struct mlx5dr_action *action,
 		if (ret)
 			return ret;
 
-		if (!(*modify_ttl))
-			*modify_ttl = dr_action_modify_check_is_ttl_modify(sw_action);
+		if (!(*modify_ttl) &&
+		    dr_action_modify_check_is_ttl_modify(sw_action)) {
+			if (dr_action_modify_ttl_ignore(dmn))
+				continue;
+
+			*modify_ttl = true;
+		}
 
 		/* Convert SW action to HW action */
 		ret = dr_action_modify_sw_to_hw(dmn,
@@ -1631,7 +1642,7 @@ static int dr_actions_convert_modify_header(struct mlx5dr_action *action,
 			 * modify actions doesn't exceeds the limit
 			 */
 			hw_idx++;
-			if ((num_sw_actions + hw_idx - i) >= max_hw_actions) {
+			if (hw_idx >= max_hw_actions) {
 				mlx5dr_dbg(dmn, "Modify header action number exceeds HW limit\n");
 				return -EINVAL;
 			}
@@ -1642,6 +1653,10 @@ static int dr_actions_convert_modify_header(struct mlx5dr_action *action,
 		hw_idx++;
 	}
 
+	/* if the resulting HW actions list is empty, add NOP action */
+	if (!hw_idx)
+		hw_idx++;
+
 	*num_hw_actions = hw_idx;
 
 	return 0;

include/linux/mlx5/mlx5_ifc.h

@@ -833,7 +833,7 @@ struct mlx5_ifc_flow_table_eswitch_cap_bits {
 	u8      fdb_to_vport_reg_c_id[0x8];
 	u8      reserved_at_8[0xd];
 	u8      fdb_modify_header_fwd_to_table[0x1];
-	u8      reserved_at_16[0x1];
+	u8      fdb_ipv4_ttl_modify[0x1];
 	u8      flow_source[0x1];
 	u8      reserved_at_18[0x2];
 	u8      multi_fdb_encap[0x1];