Re: [PATCH] net/hns3: fix Rx packet truncation when KEEP CRC enabled

[Jie Hai <haijie1@huawei.com>]

Hi, Ferruh,

Thanks for your review.

On 2024/2/7 22:15, Ferruh Yigit wrote:
> On 2/6/2024 1:10 AM, Jie Hai wrote:
>> From: Dengdui Huang <huangdengdui@huawei.com>
>>
>> When KEEP_CRC offload is enabled, some packets will be truncated and
>> the CRC is still be stripped in following cases:
>> 1. For HIP08 hardware, the packet type is TCP and the length
>>     is less than or equal to 60B.
>> 2. For other hardwares, the packet type is IP and the length
>>     is less than or equal to 60B.
>>
> 
> If a device doesn't support the offload by some packets, it can be
> option to disable offload for that device, instead of calculating it in
> software and append it.

The KEEP CRC feature of hns3 is faulty only in the specific packet
type and small packet(<60B) case.
What's more, the small ethernet packet is not common.

> Unless you have a specific usecase, or requirement to support the offload.

Yes, some users of hns3 are already using this feature.
So we cannot drop this offload

> <...>
> 
>> @@ -2492,10 +2544,16 @@ hns3_recv_pkts_simple(void *rx_queue,
>>   			goto pkt_err;
>>   
>>   		rxm->packet_type = hns3_rx_calc_ptype(rxq, l234_info, ol_info);
>> -
>>   		if (rxm->packet_type == RTE_PTYPE_L2_ETHER_TIMESYNC)
>>   			rxm->ol_flags |= RTE_MBUF_F_RX_IEEE1588_PTP;
>>   
>> +		if (unlikely(rxq->crc_len > 0)) {
>> +			if (hns3_need_recalculate_crc(rxq, rxm))
>> +				hns3_recalculate_crc(rxq, rxm);
>> +			rxm->pkt_len -= rxq->crc_len;
>> +			rxm->data_len -= rxq->crc_len;
>>
> 
> Removing 'crc_len' from 'mbuf->pkt_len' & 'mbuf->data_len' is
> practically same as stripping CRC.
> 
> We don't count CRC length in the statistics, but it should be accessible
> in the payload by the user.
Our drivers are behaving exactly as you say.
> 
> .