[PATCH iwl-next 3/8] ixgbe: prevent adding duplicate FDIR perfect filter rules

[Aleksandr Loktionov <aleksandr.loktionov@intel.com>]

From: Piotr Skajewski <piotrx.skajewski@intel.com>

When the same flow specification is added twice (same 5-tuple with
different sw_idx values), ixgbe_add_ethtool_fdir_entry() silently
programs the duplicate into hardware using a second FDIR table slot.
This wastes a scarce FDIR entry and can cause confusing behaviour
when deleting rules.

Add a helper ixgbe_match_ethtool_fdir_entry() that walks the in-kernel
filter list before programming hardware.  If an entry with an
identical filter (excluding the sw_idx) already exists, the new add
request is rejected with -EEXIST.

Signed-off-by: Piotr Skajewski <piotrx.skajewski@intel.com>
Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
---
 .../net/ethernet/intel/ixgbe/ixgbe_ethtool.c  | 27 +++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
index ba049b3..a2009df 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
@@ -2938,6 +2938,23 @@ static int ixgbe_flowspec_to_flow_type(struct ethtool_rx_flow_spec *fsp,
 	return 1;
 }
 
+static bool ixgbe_match_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
+					   struct ixgbe_fdir_filter *input)
+{
+	struct ixgbe_fdir_filter *rule = NULL;
+
+	hlist_for_each_entry(rule, &adapter->fdir_filter_list, fdir_node) {
+		if (rule->sw_idx == input->sw_idx)
+			continue;
+		if (!memcmp(&rule->filter, &input->filter,
+			    sizeof(rule->filter))) {
+			e_warn(drv, "FDIR filter already exists\n");
+			return true;
+		}
+	}
+	return false;
+}
+
 static int ixgbe_add_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
 					struct ethtool_rxnfc *cmd)
 {
@@ -2947,7 +2964,7 @@ static int ixgbe_add_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
 	struct ixgbe_fdir_filter *input;
 	union ixgbe_atr_input mask;
 	u8 queue;
-	int err;
+	int err = -EINVAL;
 
 	if (!(adapter->flags & IXGBE_FLAG_FDIR_PERFECT_CAPABLE))
 		return -EOPNOTSUPP;
@@ -3050,6 +3067,12 @@ static int ixgbe_add_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
 	/* apply mask and compute/store hash */
 	ixgbe_atr_compute_perfect_hash_82599(&input->filter, &mask);
 
+	/* check for a duplicate filter */
+	if (ixgbe_match_ethtool_fdir_entry(adapter, input)) {
+		err = -EEXIST;
+		goto err_out_w_lock;
+	}
+
 	/* program filters to filter memory */
 	err = ixgbe_fdir_write_perfect_filter_82599(hw,
 				&input->filter, input->sw_idx, queue);
@@ -3065,7 +3088,7 @@ static int ixgbe_add_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
 	spin_unlock(&adapter->fdir_perfect_lock);
 err_out:
 	kfree(input);
-	return -EINVAL;
+	return err;
 }
 
 static int ixgbe_del_ethtool_fdir_entry(struct ixgbe_adapter *adapter,
-- 
2.52.0