netdev - [PATCH v2 net] ixgbe: fix parsing of TC actions for HW offload

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Date:   Thu, 31 May 2018 23:21:04 +0200
From:   Ondřej Hlavatý <ohlavaty@...hat.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Cc:     netdev@...r.kernel.org, Andrew Bowers <andrewx.bowers@...el.com>,
        Ondřej Hlavatý <ohlavaty@...hat.com>
Subject: [PATCH v2 net] ixgbe: fix parsing of TC actions for HW offload

The previous code was optimistic, accepting the offload of whole action
chain when there was a single known action (drop/redirect). This results
in offloading a rule which should not be offloaded, because its behavior
cannot be reproduced in the hardware.

For example:

$ tc filter add dev eno1 parent ffff: protocol ip \
    u32 ht 800: order 1 match tcp src 42 FFFF \
    action mirred egress mirror dev enp1s16 pipe \
    drop

The controller is unable to mirror the packet to a VF, but still
offloads the rule by dropping the packet.

Change the approach of the function to a pessimistic one, rejecting the
chain when an unknown action is found. This is better suited for future
extensions.

Note that both recognized actions always return TC_ACT_SHOT, therefore
it is safe to ignore actions behind them.

Signed-off-by: Ondřej Hlavatý <ohlavaty@...hat.com>

---

Changes from v1: Fix the introduced warning by rejecting hypothetical
empty action chains as well. Removed Cc's from description.

 drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index afadba99f7b8..2ecd55856c50 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -9054,7 +9054,6 @@ static int parse_tc_actions(struct ixgbe_adapter *adapter,
 {
 	const struct tc_action *a;
 	LIST_HEAD(actions);
-	int err;

 	if (!tcf_exts_has_actions(exts))
 		return -EINVAL;
@@ -9075,11 +9074,11 @@ static int parse_tc_actions(struct ixgbe_adapter *adapter,

 			if (!dev)
 				return -EINVAL;
-			err = handle_redirect_action(adapter, dev->ifindex, queue,
-						     action);
-			if (err == 0)
-				return err;
+			return handle_redirect_action(adapter, dev->ifindex,
+						      queue, action);
 		}
+
+		return -EINVAL;
 	}

 	return -EINVAL;
-- 
2.17.1