[dpdk-users] rte_eth_from_rings: how to free descriptors

[avatli at itu.edu.tr]

Hi

I'm trying to use rte_eth_from_rings() to allow data exchange between  
cores using rings to be done in the same way as sending or receiving  
packets from an Ethernet device.  However, I don't understand exactly  
how rte_mbuf descriptors are cleaned.

For example, for a forwarding application, I don't need to free an  
rte_mbuf when I use rte_eth_rx_burst() and rte_eth_tx_burst() on the  
real Ethernet device. Because the rte_eth_tx_burst() function picks up  
the next available descriptor in the transmit ring and frees the  
network buffer previously sent with that descriptor. As a result, I do  
not need to free rte_mbuf descriptor since it will be freed in  
rte_eth_tx_burst().  Please correct me if I'm wrong.

Does the same behavior apply to rte_eth_from_rings() model? If so, I  
have to copy the rte_mbuf from pseudo-Ethernet port (created by  
rte_eth_from_rings) to send to a real Ethernet port, otherwise it will  
be freed twice (in the 2th and 4rd below). Is there any other way than  
copy? Please correct me if it is wrong.

app_1
1) allocate rte_mbuf
2) sent the rte_mbuf to pseudo-Ethernet using rte_eth_tx_burst()

app_2
3) pseudo-Ethernet rte_eth_rx_burst()
4) real-Ethernet rte_eth_tx_burst()

Best regards...

Volkan