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

[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.