examples/ptpclient: fix delay request message

From: Vanshika Shukla <vanshika.shukla@nxp.com>

The size of delay request message sent out by the DPDK
ptpclient application was observed to have extra length
than expected. Due to this, bad messages were observed
on the master side and delay response was not received.

This patch fixes this bug.

Signed-off-by: Vanshika Shukla <vanshika.shukla@nxp.com>
---
 examples/ptpclient/ptpclient.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
  

Hello,

On Wed, Nov 17, 2021 at 7:19 AM <vanshika.shukla@nxp.com> wrote:
>
> From: Vanshika Shukla <vanshika.shukla@nxp.com>
>
> The size of delay request message sent out by the DPDK
> ptpclient application was observed to have extra length
> than expected. Due to this, bad messages were observed
> on the master side and delay response was not received.
>
> This patch fixes this bug.

We need a Fixes: line and it is likely a candidate for backport.

>
> Signed-off-by: Vanshika Shukla <vanshika.shukla@nxp.com>
> ---
>  examples/ptpclient/ptpclient.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/examples/ptpclient/ptpclient.c b/examples/ptpclient/ptpclient.c
> index 4f32ade7fb..1eb813ab01 100644
> --- a/examples/ptpclient/ptpclient.c
> +++ b/examples/ptpclient/ptpclient.c
> @@ -422,7 +422,7 @@ parse_fup(struct ptpv2_data_slave_ordinary *ptp_data)
>
>                 created_pkt = rte_pktmbuf_alloc(mbuf_pool);
>                 pkt_size = sizeof(struct rte_ether_hdr) +
> -                       sizeof(struct ptp_message);
> +                       sizeof(struct delay_req_msg);
>                 created_pkt->data_len = pkt_size;
>                 created_pkt->pkt_len = pkt_size;

This example code is in a bad shape.

Directly updating mbuf fields without caring for available data size
is a bad practice, plus there is no check on available size in
allocated buffer.
It should be like (untested):

                created_pkt = rte_pktmbuf_alloc(mbuf_pool);
                pkt_size = sizeof(struct rte_ether_hdr) +
-                       sizeof(struct ptp_message);
-               created_pkt->data_len = pkt_size;
-               created_pkt->pkt_len = pkt_size;
+                       sizeof(struct delay_req_msg);
+               if (rte_pktmbuf_append(created_pkt, pkt_size) == NULL) {
+                       rte_pktmbuf_free(created_pkt);
+                       return;
+               }
+

After this, the rest of the code uses a struct ptp_msg pointer.
It should use a pointer with the right type.

Something like:

+               struct delay_req_msg *req_msg;
...
-               ptp_msg = (struct ptp_message *)
-                       (rte_pktmbuf_mtod(created_pkt, char *) +
-                       sizeof(struct rte_ether_hdr));
+               req_msg = rte_pktmbuf_mtod_offset(created_pkt,
+                       struct delay_req_msg *, sizeof(struct rte_ether_hdr));

etc...