[dpdk-dev] [PATCH v2 3/4] app/testpmd: fix packet header in txonly mode

Chengchang Tang tangchengchang at huawei.com
Thu Sep 17 13:48:04 CEST 2020



On 2020/9/17 19:16, Ferruh Yigit wrote:
> On 9/17/2020 8:10 AM, Chengchang Tang wrote:
>>
>>
>> On 2020/9/15 0:23, Ferruh Yigit wrote:
>>> On 8/20/2020 2:42 AM, Wei Hu (Xavier) wrote:
>>>> From: Chengchang Tang <tangchengchang at huawei.com>
>>>>
>>>> In txonly forward mode, the packet header is fixed by the initial
>>>> setting, including the packet length and checksum. So when the packets
>>>> varies, this may cause a packet header error. Currently, there are two
>>>> methods in txonly mode to randomly change the packets.
>>>> 1. Set txsplit random and txpkts (x[,y]*), the number of segments
>>>>     each packets will be a random value between 1 and total number of
>>>>     segments determined by txpkts settings.
>>>>     The step as follows:
>>>>       a) ./testpmd -w xxx -l xx -n 4 -- -i --rxd xxxx --txd xxxx
>>>>       b) set fwd txonly
>>>>       c) set txsplit rand
>>>>       d) set txpkts 2048,2048,2048,2048
>>>>       e) start
>>>> The nb_segs of the packets sent by testpmd will be 1~4. The real packet
>>>> length will be 2048, 4096, 6144 and 8192. But in fact the packet length
>>>> in ip header and udp header will be fixed by 8178 and 8158.
>>>
>>> Although I confirm the patch fixes the ip & udp header packet size for
>>> "txsplit=rand" config,
>>> I am always getting actual packet size wrong, independent from
>>> 'txsplit', and it is always first segment size. Am I doing something wrong?
>>
>> Yes, I miss it. If the txsplit is not set and the txpkts is set, the txonly
>> fwd engine will only send single segment packets, and there will be a payload
>> error for the data_len will be refreshed by the sum of the segment size.
>>
> 
> I am getting the size error when 'txsplit' is 'on' or 'rand'. In that case packet header are correct (after your patch) but wireshark complains the size of the packet on wire is different than the values in headers. And the size of the actual packet is reported by wireshark as the size of the first segment.

Maybe it should be configured with multi_segs offload. If the 'txsplit' is 'on' or 'rand',
the txonly engine will send a multi segments packets. I tested it on hns3 PMD, which
support a multi_segs by default configuration. So, I miss to add these information to
the commit log. For some PMDs, the multi_segs is not support as default.

>> May be the data_len should be the first segment size if the txsplit is not set?
>> I will fix it in the next version.
>>>
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> 
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