Re: [dpdk-dev] Wrong TCP Checkum computed by hardware

[Padam Jeet Singh <padam.singh@inventum.net>]

> On 28-Oct-2015, at 1:46 pm, Liu, Jijiang <jijiang.liu@intel.com> wrote:
> 
> 
> 
>> -----Original Message-----
>> From: Padam Jeet Singh [mailto:padam.singh@inventum.net]
>> Sent: Wednesday, October 28, 2015 4:12 PM
>> To: Liu, Jijiang
>> Cc: dev@dpdk.org; Matthew Hall
>> Subject: Re: [dpdk-dev] Wrong TCP Checkum computed by hardware
>> 
>> 
>>> On 28-Oct-2015, at 1:31 pm, Liu, Jijiang <jijiang.liu@intel.com> wrote:
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Padam Jeet Singh
>>>> Sent: Wednesday, October 28, 2015 3:20 PM
>>>> To: Matthew Hall
>>>> Cc: dev@dpdk.org
>>>> Subject: Re: [dpdk-dev] Wrong TCP Checkum computed by hardware
>>>> 
>>> 
>>> Did you set the txq_flags?
>>> If the flag is not set, the default value is IXGBE_SIMPLE_FLAGS, and the any
>> TX offloads do not work.
>>> 
>>> See the following codes in ixgbe_rxtx.c file
>>> 
>>> /* Use a simple Tx queue (no offloads, no multi segs) if possible */
>>> 	if (((txq->txq_flags & IXGBE_SIMPLE_FLAGS) == IXGBE_SIMPLE_FLAGS)
>>> 			&& (txq->tx_rs_thresh >=
>> RTE_PMD_IXGBE_TX_MAX_BURST)) {
>>> 		PMD_INIT_LOG(INFO, "Using simple tx code path");
>>>                     ...
>>> 		dev->tx_pkt_burst = ixgbe_xmit_pkts_simple;
>>> 	} else {
>>> 	             ...
>>> 		dev->tx_pkt_burst = ixgbe_xmit_pkts;
>>> 	}
>>> 
>>> 
>>> --Jijiang Liu
>> 
>> I initialise the queue with the following structure:
>> 
>> static const struct rte_eth_txconf tx_conf = {
>> 	.tx_thresh = {
>> 		.pthresh = 32,  /* Ring prefetch threshold */
>> 		.hthresh = 0,   /* Ring host threshold */
>> 		.wthresh = 0,   /* Ring writeback threshold */
>> 	},
>> 	.tx_free_thresh = 0,    /* Use PMD default values */
>> 	.tx_rs_thresh = 0,      /* Use PMD default values */
>> };
>> 
>> This would set the txq_flags to zero - so the tx_pkt_burst function would
>> always point to ixgbe_xmit_pkts. Also, as observed only TCP checksum is
>> computed wrong when there is VLAN TX Offload + IP Offload + TCP offload
>> bits set.  VLAN TX Offload + IP Offload + TCP CKSUM in software generates
>> correct packet on the wire.
> 
> I don't think the txq_flags is 0 if you just initialized the struct rte_eth_txconf like that.

It’s declared as a global static, so it indeed is 0. I also added some debug around the init of the queue:

for (i = 0; i < tx; ++i) {
	    ret = rte_eth_tx_queue_setup(port, i, NB_TXD,
		rte_eth_dev_socket_id(port), &tx_conf);
	    RTE_LOG(INFO, APP, "Port %u TXQ[%d] txflags = %d\n", (unsigned)port,
	    	i, tx_conf.txq_flags);
	    if (ret < 0)
		rte_exit(EXIT_FAILURE, "Could not setup up TX queue %d for "
				"port%u (%d)", i, (unsigned)port, ret);
	}

And got the following result:

Oct 28 13:55:34 localhost fpnas[1322]: APP: Port 0 TXQ[0] txflags = 0
Oct 28 13:55:34 localhost fpnas[1322]: APP: Port 0 TXQ[1] txflags = 0
Oct 28 13:55:34 localhost fpnas[1322]: APP: Port 1 TXQ[0] txflags = 0
Oct 28 13:55:34 localhost fpnas[1322]: APP: Port 1 TXQ[1] txflags = 0
Oct 28 13:55:35 localhost fpnas[1322]: APP: Port 2 TXQ[0] txflags = 0
Oct 28 13:55:35 localhost fpnas[1322]: APP: Port 3 TXQ[0] txflags = 0


> 
>> Thanks,
>> Padam