Re: rte_pktmbuf_alloc() is returning same address on two consecutive calls

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 23 Feb 2023 14:54:13 +0000
NAGENDRA BALAGANI <nagendra.balagani@oracle.com> wrote:

> Hi Team,
> 
> In my dpdk application, I am facing an issue where rte_pktmbuf_alloc() is returning same address for two consecutive calls in a single thread context.
> 
> Following is the code snippet,
> 
> int Func(struct rte_mbuf *mblk)
> {
>               struct rte_mbuf *tmpbuf = nullptr;;
>               struct rte_mbuf *copybuf  = nullptr;
>               char  *nextPtr = NULL;
> 
>               tmpbuf = rte_pktmbuf_alloc(mbuf_pool);
> 
>               nextPtr = rte_pktmbuf_append(tmpbuf, IPV4_HDR_LEN);
>               //update some info on nextptr
> 
>               copybuf = rte_pktmbuf_copy(mblk, mbuf_pool, 0, pkt_len);
> 
>               ....
>               return 0;
> }
> 
> With the above snippet, 'tmpbuf' and 'copybuf' which are getting allocated from same pool (mbuf_pool), pointing to same address, Due to this tmpbuf which gets allocated first, and further populated, is getting over written inside rte_pktmbuf_copy() call which is not expected .
> When I further debug , rte_pktmbuf_copy() is internally using rte_pktmbuf_alloc() to get the free buffer from mbuf_pool and copy the data from mblk.
> 
> Please let us know if there is any known issue with rte_pktmbuf_alloc(), and why it may be giving same address on two consecutive calls.
> 
> Regards,
> Nagendra
> 

Most likely your mbuf pool has gotten corrupted before you get to that code.
Try building with the config options for POOL and MBUF debug.