cxgb4: check rule prio conflicts before offload

Only offload rule if it satisfies both of the following conditions:
1. The immediate previous rule has priority <= current rule's priority.
2. The immediate next rule has priority >= current rule's priority.

Also rework free entry fetch logic to search from end of TCAM, instead
of beginning, because higher indices have lower priority than lower
indices. This is similar to how TC auto generates priority values.

v5:
- Fixed commit message and comment to include comparison for equal
  priority.

v4:
- Patch added in this version.

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 5 deletions

diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c
index e447976bdd3e..5179ad23be3c 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_flower.c
@@ -636,12 +636,12 @@ static int cxgb4_validate_flow_actions(struct net_device *dev,
 int cxgb4_tc_flower_replace(struct net_device *dev,
 			    struct flow_cls_offload *cls)
 {
+	struct netlink_ext_ack *extack = cls->common.extack;
 	struct adapter *adap = netdev2adap(dev);
 	struct ch_tc_flower_entry *ch_flower;
 	struct ch_filter_specification *fs;
 	struct filter_ctx ctx;
-	int fidx;
-	int ret;
+	int fidx, ret;
 
 	if (cxgb4_validate_flow_actions(dev, cls))
 		return -EOPNOTSUPP;
@@ -664,14 +664,35 @@ int cxgb4_tc_flower_replace(struct net_device *dev,
 	if (fs->hash) {
 		fidx = 0;
 	} else {
-		fidx = cxgb4_get_free_ftid(dev, fs->type ? PF_INET6 : PF_INET);
-		if (fidx < 0) {
-			netdev_err(dev, "%s: No fidx for offload.\n", __func__);
+		u8 inet_family;
+
+		inet_family = fs->type ? PF_INET6 : PF_INET;
+
+		/* Note that TC uses prio 0 to indicate stack to
+		 * generate automatic prio and hence doesn't pass prio
+		 * 0 to driver. However, the hardware TCAM index
+		 * starts from 0. Hence, the -1 here.
+		 */
+		if (cls->common.prio <= adap->tids.nftids)
+			fidx = cls->common.prio - 1;
+		else
+			fidx = cxgb4_get_free_ftid(dev, inet_family);
+
+		/* Only insert FLOWER rule if its priority doesn't
+		 * conflict with existing rules in the LETCAM.
+		 */
+		if (fidx < 0 ||
+		    !cxgb4_filter_prio_in_range(dev, fidx, cls->common.prio)) {
+			NL_SET_ERR_MSG_MOD(extack,
+					   "No free LETCAM index available");
 			ret = -ENOMEM;
 			goto free_entry;
 		}
 	}
 
+	fs->tc_prio = cls->common.prio;
+	fs->tc_cookie = cls->cookie;
+
 	init_completion(&ctx.completion);
 	ret = __cxgb4_set_filter(dev, fidx, fs, &ctx);
 	if (ret) {