netdev - Re: [PATCH iwl-next 1/2] ice: Add direction metadata

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Date: Fri, 23 Jun 2023 09:25:04 +0200
From: Simon Horman <simon.horman@...igine.com>
To: Marcin Szycik <marcin.szycik@...ux.intel.com>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: Re: [PATCH iwl-next 1/2] ice: Add direction metadata

On Thu, Jun 22, 2023 at 03:35:12PM +0200, Marcin Szycik wrote:
> Currently it is possible to create a filter which breaks TX traffic, e.g.:
> 
> tc filter add dev $PF1 ingress protocol ip prio 1 flower ip_proto udp
> dst_port $PORT action mirred egress redirect dev $VF1_PR
> 
> This adds a rule which might match both TX and RX traffic, and in TX path
> the PF will actually receive the traffic, which breaks communication.
> 
> To fix this, add a match on direction metadata flag when adding a tc rule.
> 
> Because of the way metadata is currently handled, a duplicate lookup word
> would appear if VLAN metadata is also added. The lookup would still work
> correctly, but one word would be wasted. To prevent it, lookup 0 now always
> contains all metadata. When any metadata needs to be added, it is added to
> lookup 0 and lookup count is not incremented. This way, two flags residing
> in the same word will take up one word, instead of two.
> 
> Note: the drop action is also affected, i.e. it will now only work in one
> direction.
> 
> Signed-off-by: Marcin Szycik <marcin.szycik@...ux.intel.com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>