Re: reuse the packets after tx burst

[Stephen Hemminger <stephen@networkplumber.org>]

On Mon, 12 Aug 2024 15:55:50 +0530
Lokesh Chakka <lvenkatakumarchakka@gmail.com> wrote:

> hello,
> 
> Here is a small piece of code :
> 
> while( condition )
> {
> 
> 	if( rte_eth_tx_burst( port_id, 0, mbuf, num_of_pkts_per_queue ) !=
> num_of_pkts_per_queue )
> 	{
> 		fprintf( stderr, "%d %s\n", rte_errno, rte_strerror(rte_errno) );
> 		rte_exit( EXIT_FAILURE, "%s %d rte_eth_tx_burst port id: %u\n",
> __func__, __LINE__, port_id );//second iteration failing.
> 	}
> 	fprintf( stderr, "%s %d port: %u packet: %c sent %u packets\n",
> __func__, __LINE__, port_id, argv[3][0], num_of_pkts_per_queue
> );//printing once
> 	for( pkt_count=0; pkt_count<num_of_pkts_per_queue; pkt_count++ )
> 	{//want to send same data again...!!!
> 		mbuf[pkt_count]->pkt_len = mbuf[pkt_count]->data_len = dev_info.max_mtu;
> 
> 	}
> 
> }
> 
> Can someone help me understand how to reuse the packets again to send the
> same data ?
> 

When packet is passed to tx_burst, the ownership of that mbuf is passed
to the driver. The driver will free it after it is sent.

One option would be to increase the reference count on the packet before sending.
Using rte_mbuf_refcnt_update() function to add one to refcount.
Then the driver will decrement refcount and the refcount will still be one (not freed).

Assume this is some kind of packet generator.