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

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

[Ondřej Hlavatý]

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@redhat.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

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

[Jeff Kirsher]

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On Thu, 2018-05-31 at 23:21 +0200, Ondřej Hlavatý wrote:
> 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@redhat.com>

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

Note- I am having our validation move to testing with GCC 8.1.1 or
later so that we can catch warnings like Dave found in the future.

Dave- Please go ahead and pick this up.

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

[David Miller]

From: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Date: Thu, 31 May 2018 14:46:08 -0700

> On Thu, 2018-05-31 at 23:21 +0200, Ondřej Hlavatý wrote:
>> 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@redhat.com>
> 
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> 
> Note- I am having our validation move to testing with GCC 8.1.1 or
> later so that we can catch warnings like Dave found in the future.
> 
> Dave- Please go ahead and pick this up.

Ok, applied, thanks.