Strange behavior with rte_pktmbuf_clone cal

[NAGENDRA BALAGANI]

Hi,

I am seeing strange behavior where rte_pktmbuf_clone is not giving desired result.
Here is the detailed info, in my dpdk application  , once I received the packet info in mbuf, I need to send the same packet to two destinations, the sequence  I should follow is,

(i)                  First, Tunnel the packet to one of desired destination, so I created the shallow copy using rte_pktmbuf_clone, had another mbuf for Outer IP Header for IPinIP tunnel and sent to NIC.

(ii)                Second, I need to modify the source and destination ip addresses of the packet and send out.

The issue, I am seeing is the tunneled packet (clone) have modified IP addresses from (ii).

Code flow:

Main()
{
Struct rte_mbuf *org_mbuf; //lets assume this org_mbuf is holding the packet info.

(i)                  Towards First destination.
Build_tunnel_packet(org_mbuf) {

-          Struct rte_mbuf *clone_buffer;
-          Allocate a clone buffer Clone_buffer = rte_pktmbuf_clone(org_mbuf, clone_pool);

-          Constructed IPinIP info in another mbuf and prepended in clone_buffer
-          Call rte_pktmbuf_tx_burst();
}

(ii)                Towards another destination.
Modify_l3_and_route(org_mbuf)
{

-          Modify L3 information of 'org_mbuf'
-          and Call rte_pkt_mbuf_tx_burst();
}

}

[cid:image001.jpg at 01D916CA.5B7CCA10]

In the above screenshot, the packet 37 should tunneled as it is by adding the outer ip layer(i.e 182.16.146.*), but the inner L3 information also getting changed (which I am modifying in the second step) for some packets.
Using, rte_pktmbuf_copy(), solving the issue, but in expense of extra mbuf.


Please, help me in understanding what is wrong in the case of rte_pktmbuf_clone()?


Regards,
Nagendra


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