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, 22 insertions, 14 deletions

diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_u32.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_u32.c
index 02fc63fa7f25..133f8623ba86 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_u32.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_tc_u32.c
@@ -36,6 +36,7 @@
 #include <net/tc_act/tc_mirred.h>
 
 #include "cxgb4.h"
+#include "cxgb4_filter.h"
 #include "cxgb4_tc_u32_parse.h"
 #include "cxgb4_tc_u32.h"
 
@@ -148,6 +149,7 @@ static int fill_action_fields(struct adapter *adap,
 int cxgb4_config_knode(struct net_device *dev, struct tc_cls_u32_offload *cls)
 {
 	const struct cxgb4_match_field *start, *link_start = NULL;
+	struct netlink_ext_ack *extack = cls->common.extack;
 	struct adapter *adapter = netdev2adap(dev);
 	__be16 protocol = cls->common.protocol;
 	struct ch_filter_specification fs;
@@ -164,14 +166,21 @@ int cxgb4_config_knode(struct net_device *dev, struct tc_cls_u32_offload *cls)
 	if (protocol != htons(ETH_P_IP) && protocol != htons(ETH_P_IPV6))
 		return -EOPNOTSUPP;
 
-	/* Fetch the location to insert the filter. */
-	filter_id = cls->knode.handle & 0xFFFFF;
+	/* 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.
+	 */
+	filter_id = TC_U32_NODE(cls->knode.handle) - 1;
 
-	if (filter_id > adapter->tids.nftids) {
-		dev_err(adapter->pdev_dev,
-			"Location %d out of range for insertion. Max: %d\n",
-			filter_id, adapter->tids.nftids);
-		return -ERANGE;
+	/* Only insert U32 rule if its priority doesn't conflict with
+	 * existing rules in the LETCAM.
+	 */
+	if (filter_id >= adapter->tids.nftids ||
+	    !cxgb4_filter_prio_in_range(dev, filter_id, cls->common.prio)) {
+		NL_SET_ERR_MSG_MOD(extack,
+				   "No free LETCAM index available");
+		return -ENOMEM;
 	}
 
 	t = adapter->tc_u32;
@@ -190,6 +199,9 @@ int cxgb4_config_knode(struct net_device *dev, struct tc_cls_u32_offload *cls)
 
 	memset(&fs, 0, sizeof(fs));
 
+	fs.tc_prio = cls->common.prio;
+	fs.tc_cookie = cls->knode.handle;
+
 	if (protocol == htons(ETH_P_IPV6)) {
 		start = cxgb4_ipv6_fields;
 		is_ipv6 = true;
@@ -350,14 +362,10 @@ int cxgb4_delete_knode(struct net_device *dev, struct tc_cls_u32_offload *cls)
 		return -EOPNOTSUPP;
 
 	/* Fetch the location to delete the filter. */
-	filter_id = cls->knode.handle & 0xFFFFF;
-
-	if (filter_id > adapter->tids.nftids) {
-		dev_err(adapter->pdev_dev,
-			"Location %d out of range for deletion. Max: %d\n",
-			filter_id, adapter->tids.nftids);
+	filter_id = TC_U32_NODE(cls->knode.handle) - 1;
+	if (filter_id >= adapter->tids.nftids ||
+	    cls->knode.handle != adapter->tids.ftid_tab[filter_id].fs.tc_cookie)
 		return -ERANGE;
-	}
 
 	t = adapter->tc_u32;
 	handle = cls->knode.handle;