[dpdk-dev] [PATCH v8 1/2] app/testpmd: fix max rx packet length for VLAN packets

Ferruh Yigit ferruh.yigit at intel.com
Thu Nov 5 11:50:45 CET 2020


On 11/5/2020 10:48 AM, Thomas Monjalon wrote:
> + more maintainers Cc'ed
> 
> We have a critical issue with testpmd in -rc2.
> It is blocking a lot of testing.
> Would be good to do a -rc3 today.
> Please see below.
> 
> 05/11/2020 11:44, Thomas Monjalon:
>> 05/11/2020 11:37, Ferruh Yigit:
>>> On 11/5/2020 9:33 AM, Yang, SteveX wrote:
>>>> From: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
>>>>> Sent: Thursday, November 5, 2020 4:54 PM
>>>>> To: Thomas Monjalon <thomas at monjalon.net>; Yang, SteveX
>>>>> <stevex.yang at intel.com>; Yigit, Ferruh <ferruh.yigit at intel.com>
>>>>> Cc: dev at dpdk.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>;
>>>>> Xing, Beilei <beilei.xing at intel.com>; Lu, Wenzhuo <wenzhuo.lu at intel.com>;
>>>>> Iremonger, Bernard <bernard.iremonger at intel.com>; Yang, Qiming
>>>>> <qiming.yang at intel.com>; mdr at ashroe.eu; nhorman at tuxdriver.com;
>>>>> david.marchand at redhat.com
>>>>> Subject: Re: [dpdk-dev] [PATCH v8 1/2] app/testpmd: fix max rx packet
>>>>> length for VLAN packets
>>>>>
>>>>> On 11/4/20 11:39 PM, Thomas Monjalon wrote:
>>>>>> 04/11/2020 21:19, Ferruh Yigit:
>>>>>>> On 11/4/2020 5:55 PM, Thomas Monjalon wrote:
>>>>>>>> 04/11/2020 18:07, Ferruh Yigit:
>>>>>>>>> On 11/4/2020 4:51 PM, Thomas Monjalon wrote:
>>>>>>>>>> 03/11/2020 14:29, Ferruh Yigit:
>>>>>>>>>>> On 11/2/2020 11:48 AM, Ferruh Yigit wrote:
>>>>>>>>>>>> On 11/2/2020 8:52 AM, SteveX Yang wrote:
>>>>>>>>>>>>> When the max rx packet length is smaller than the sum of mtu
>>>>>>>>>>>>> size and ether overhead size, it should be enlarged, otherwise
>>>>>>>>>>>>> the VLAN packets will be dropped.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Fixes: 35b2d13fd6fd ("net: add rte prefix to ether defines")
>>>>>>>>>>>>>
>>>>>>>>>>>>> Signed-off-by: SteveX Yang <stevex.yang at intel.com>
>>>>>>>>>>>>
>>>>>>>>>>>> Reviewed-by: Ferruh Yigit <ferruh.yigit at intel.com>
>>>>>>>>>>>
>>>>>>>>>>> Applied to dpdk-next-net/main, thanks.
>>>>>>>>>>>
>>>>>>>>>>> only 1/2 applied since discussion is going on for 2/2.
>>>>>>>>>>
>>>>>>>>>> I'm not sure this testpmd change is good.
>>>>>>>>>>
>>>>>>>>>> Reminder: testpmd is for testing the PMDs.
>>>>>>>>>> Don't we want to see VLAN packets dropped in the case described
>>>>> above?
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The patch set 'max_rx_pkt_len' in a way to make MTU 1500 for all
>>>>>>>>> PMDs, otherwise testpmd set hard-coded 'RTE_ETHER_MAX_LEN'
>>>>> value,
>>>>>>>>> which makes MTU between 1492-1500 depending on PMD.
>>>>>>>>>
>>>>>>>>> It is application responsibility to provide correct 'max_rx_pkt_len'.
>>>>>>>>> I guess the original intention was to set MTU as 1500 but was not
>>>>>>>>> correct for all PMDs and this patch is fixing it.
>>>>>>>>>
>>>>>>>>> The same problem in the ethdev, (assuming 'RTE_ETHER_MAX_LEN'
>>>>> will
>>>>>>>>> give MTU 1500), the other patch in the set is to fix it later.
>>>>>>>>
>>>>>>>> OK but the testpmd patch is just hiding the issue, isn't it?
>>>>>>>>
>>>>>>>
>>>>>>> I don't think so, issue was application (testpmd) setting the
>>>>> 'max_rx_pkt_len'
>>>>>>> wrong.
>>>>>>>
>>>>>>> What is hidden?
>>>>>>
>>>>>> I was looking for adding a helper in ethdev API.
>>>>>> But I think I can agree with your way of thinking.
>>>>>>
>>>>>
>>>>> The patch breaks running testpmd on Virtio-Net because the driver
>>>>> populates dev_info.max_rx_pktlen but keeps dev_info.max_mtu equal to
>>>>> UINT16_MAX as it was filled in by ethdev. As the result:
>>>>>
>>>>> Ethdev port_id=0 max_rx_pkt_len 11229 > max valid value 9728 Fail to
>>>>> configure port 0
>>>>
>>>> Similar issue occurred for other net PMD drivers which use default max_mtu (UINT16_MAX).
>>>> More strict checking condition will be added within new patch sooner.
>>>>
>>>
>>> :(
>>>
>>> For drivers not providing 'max_mtu' information explicitly, the default
>>> 'UINT16_MAX' is set in ethdev layer.
>>> This prevents calculating PMD specific 'overhead' and the logic in the patch is
>>> broken.
>>>
>>> Indeed this makes inconsistency in the driver too, for example for virtio, it
>>> claims 'max_rx_pktlen' as "VIRTIO_MAX_RX_PKTLEN (9728)" and 'max_mtu' as
>>> UINT16_MAX. From 'virtio_mtu_set()' we can see the real limit is
>>> 'VIRTIO_MAX_RX_PKTLEN'.
>>>
>>> When PMDs fixed, the logic in this patch can work but not sure if post -rc2 is
>>> good time to start fixing the PMDs.
>>
>> Do you suggest revert is the best choice here?
> 
> 

(copy/pasting previous reply to this eamil)

One option is revert, but than the issue this patch is trying to fix still remain.

Other option is the extend the patch as Steve sent [1], the check there is more 
like workaround in application, so not nice to have them, but with extending the 
deprecation notice (other patch in this patchset) to fix PMDs too in next 
release, I would be OK to have these checks. What do you think?

[1]
https://patches.dpdk.org/patch/83717/



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