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Date: Fri, 3 May 2024 18:08:04 +0000
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Subject: Re: [Intel-wired-lan] [PATCH iwl-next] ice: flower: validate control
 flags
To: "Buvaneswaran, Sujai" <sujai.buvaneswaran@intel.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
 Eric Dumazet <edumazet@google.com>,
 "Nguyen, Anthony L" <anthony.l.nguyen@intel.com>,
 Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
 "David S. Miller" <davem@davemloft.net>,
 "intel-wired-lan@lists.osuosl.org" <intel-wired-lan@lists.osuosl.org>
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Hi Sujai,

On 5/3/24 5:57 AM, Buvaneswaran, Sujai wrote:
>> -----Original Message-----
>> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
>> Asbjørn Sloth Tønnesen
>> Sent: Tuesday, April 16, 2024 8:14 PM
>> To: intel-wired-lan@lists.osuosl.org
>> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Eric Dumazet
>> <edumazet@google.com>; Nguyen, Anthony L
>> <anthony.l.nguyen@intel.com>; Asbjørn Sloth Tønnesen <ast@fiberby.net>;
>> Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>;
>> David S. Miller <davem@davemloft.net>
>> Subject: [Intel-wired-lan] [PATCH iwl-next] ice: flower: validate control flags
>>
>> This driver currently doesn't support any control flags.
>>
>> Use flow_rule_has_control_flags() to check for control flags, such as can be
>> set through `tc flower ... ip_flags frag`.
>>
>> In case any control flags are masked, flow_rule_has_control_flags() sets a NL
>> extended error message, and we return -EOPNOTSUPP.
>>
>> Only compile-tested.
>>
>> Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
>> ---
>>   drivers/net/ethernet/intel/ice/ice_tc_lib.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
> 
> Hi,
> 
> I have tested this patch in upstream kernel - 6.9.0-rc5+ and observing no effect while adding tc flow rule with control flags.
> 'Not supported' error is not shown while adding the below tc rule.
> 
> [root@cbl-mariner ~]# tc qdisc add dev ens5f0np0 ingress
> [root@cbl-mariner ~]#
> [root@cbl-mariner ~]# tc filter add dev ens5f0np0 ingress protocol ip flower ip_flags frag/firstfrag action drop

Thank you for testing!

I think the issue you are observing, is because you are missing "skip_sw":
tc filter add dev ens5f0np0 ingress protocol ip flower skip_sw \
	ip_flags frag/firstfrag action drop

Without skip_sw, then the hardware offload is opportunistic,
and therefore the error in hardware offloading doesn't bubble
through to user space.

Without skip_sw, you should still be able to observe a change in
`tc filter show dev ens5f0np0 ingress`. Without the patch you
should see "in_hw", and with it you should see "not_in_hw".

With skip_sw, then the error in hardware offloading causes
the tc command to fail, with the -EOPNOTSUPP error and
associated extended Netlink error message.

Also see Ido's testing for mlxsw in this other thread:
https://lore.kernel.org/netdev/ZiABPNMbOOYGiHCq@shredder/#t

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541