[PATCH net-next 3/4] rocker: do not make neighbour entry changes when preparing transactions

[Simon Horman <simon.horman@netronome.com>]

rocker_port_ipv4_nh() and in turn rocker_port_ipv4_neigh() may be
be called with trans == SWITCHDEV_TRANS_PREPARE and then
trans == SWITCHDEV_TRANS_COMMIT from switchdev_port_obj_set() via
fib_table_insert().

Although I have been unable to find a scenario where a bug manifests
I do see some incorrect behaviour when adding a fib entry with a gateway.

The first time that rocker_port_ipv4_nh() is called, with
trans == SWITCHDEV_TRANS_PREPARE, _rocker_neigh_add()
adds a new entry to the neigh table.

And the second time  rocker_port_ipv4_nh() is called, with
trans == SWITCHDEV_TRANS_COMMIT, that entry is found and
_rocker_neigh_update() is called.

Assuming the transaction runs to completion this appears to be harmless.
I suspect it would be not correct if the transaction was aborted.

This problem does not appear to affect deletion as my analysis is
that deletion is always performed with trans == SWITCHDEV_TRANS_NONE.

For completeness _rocker_neigh_{add,del,prepare} are updated not
to manipulate fib table entries if trans == SWITCHDEV_TRANS_PREPARE.

Fixes: c4f20321d968 ("rocker: support prepare-commit transaction model")
Signed-off-by: Simon Horman <simon.horman@netronome.com>
---
 drivers/net/ethernet/rocker/rocker.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/rocker/rocker.c b/drivers/net/ethernet/rocker/rocker.c
index 89d22bdcbdc4..3f728bcd0f90 100644
--- a/drivers/net/ethernet/rocker/rocker.c
+++ b/drivers/net/ethernet/rocker/rocker.c
@@ -2909,8 +2909,11 @@ static struct rocker_neigh_tbl_entry *
 }
 
 static void _rocker_neigh_add(struct rocker *rocker,
+			      enum switchdev_trans trans,
 			      struct rocker_neigh_tbl_entry *entry)
 {
+	if (trans == SWITCHDEV_TRANS_PREPARE)
+		return;
 	entry->index = rocker->neigh_tbl_next_index++;
 	entry->ref_count++;
 	hash_add(rocker->neigh_tbl, &entry->entry,
@@ -2921,6 +2924,8 @@ static void _rocker_neigh_del(struct rocker_port *rocker_port,
 			      enum switchdev_trans trans,
 			      struct rocker_neigh_tbl_entry *entry)
 {
+	if (trans == SWITCHDEV_TRANS_PREPARE)
+		return;
 	if (--entry->ref_count == 0) {
 		hash_del(&entry->entry);
 		rocker_port_kfree(rocker_port, trans, entry);
@@ -2928,8 +2933,11 @@ static void _rocker_neigh_del(struct rocker_port *rocker_port,
 }
 
 static void _rocker_neigh_update(struct rocker_neigh_tbl_entry *entry,
+				 enum switchdev_trans trans,
 				 u8 *eth_dst, bool ttl_check)
 {
+	if (trans == SWITCHDEV_TRANS_PREPARE)
+		return;
 	if (eth_dst) {
 		ether_addr_copy(entry->eth_dst, eth_dst);
 		entry->ttl_check = ttl_check;
@@ -2973,12 +2981,12 @@ static int rocker_port_ipv4_neigh(struct rocker_port *rocker_port,
 		entry->dev = rocker_port->dev;
 		ether_addr_copy(entry->eth_dst, eth_dst);
 		entry->ttl_check = true;
-		_rocker_neigh_add(rocker, entry);
+		_rocker_neigh_add(rocker, trans, entry);
 	} else if (removing) {
 		memcpy(entry, found, sizeof(*entry));
 		_rocker_neigh_del(rocker_port, trans, found);
 	} else if (updating) {
-		_rocker_neigh_update(found, eth_dst, true);
+		_rocker_neigh_update(found, trans, eth_dst, true);
 		memcpy(entry, found, sizeof(*entry));
 	} else {
 		err = -ENOENT;
@@ -3089,13 +3097,13 @@ static int rocker_port_ipv4_nh(struct rocker_port *rocker_port,
 	if (adding) {
 		entry->ip_addr = ip_addr;
 		entry->dev = rocker_port->dev;
-		_rocker_neigh_add(rocker, entry);
+		_rocker_neigh_add(rocker, trans, entry);
 		*index = entry->index;
 		resolved = false;
 	} else if (removing) {
 		_rocker_neigh_del(rocker_port, trans, found);
 	} else if (updating) {
-		_rocker_neigh_update(found, NULL, false);
+		_rocker_neigh_update(found, trans, NULL, false);
 		resolved = !is_zero_ether_addr(found->eth_dst);
 	} else {
 		err = -ENOENT;
-- 
2.1.4