[v3] examples/multi_process - fix crash in mp_client with sparse ports

  From: Stephen Hemminger <sthemmin@microsoft.com>

The mp_client crashes if run on Azure or any system where ethdev
ports are owned. This is because the flush loop is confusing the
index into the array of ports[] with the port id.

For example if the server has Ports 3 and 5. Then calling
rte_eth_tx_buffer_flush on any other buffer will dereference null
because the tx buffer for that port was not allocated.

v2
   - fix typo
   - the flush code is common enough that it should not be marked unlikely
   - combine conditions to reduce indentation

v3
   - avoid unnecessary if() if sent is zero.

Fixes: e2366e74e029 ("examples: use buffered Tx")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
---
 .../client_server_mp/mp_client/client.c        | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)
  

On Tue, Jun 18, 2019 at 6:41 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> From: Stephen Hemminger <sthemmin@microsoft.com>
>
> The mp_client crashes if run on Azure or any system where ethdev
> ports are owned. This is because the flush loop is confusing the
> index into the array of ports[] with the port id.
>
> For example if the server has Ports 3 and 5. Then calling
> rte_eth_tx_buffer_flush on any other buffer will dereference null
> because the tx buffer for that port was not allocated.
>
> v2
>    - fix typo
>    - the flush code is common enough that it should not be marked unlikely
>    - combine conditions to reduce indentation
>
> v3
>    - avoid unnecessary if() if sent is zero.
>

Annotations should be after the ---.



> Fixes: e2366e74e029 ("examples: use buffered Tx")
>

Cc: stable@dpdk.org


Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
> ---
>  .../client_server_mp/mp_client/client.c        | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/examples/multi_process/client_server_mp/mp_client/client.c
> b/examples/multi_process/client_server_mp/mp_client/client.c
> index c23dd3f378f7..361d90b54b2d 100644
> --- a/examples/multi_process/client_server_mp/mp_client/client.c
> +++ b/examples/multi_process/client_server_mp/mp_client/client.c
> @@ -246,19 +246,19 @@ main(int argc, char *argv[])
>
>         for (;;) {
>                 uint16_t i, rx_pkts;
> -               uint16_t port;
>
>                 rx_pkts = rte_ring_dequeue_burst(rx_ring, pkts,
>                                 PKT_READ_SIZE, NULL);
>
> -               if (unlikely(rx_pkts == 0)){
> -                       if (need_flush)
> -                               for (port = 0; port < ports->num_ports;
> port++) {
> -                                       sent =
> rte_eth_tx_buffer_flush(ports->id[port], client_id,
> -                                                       tx_buffer[port]);
> -                                       if (unlikely(sent))
> -                                               tx_stats->tx[port] += sent;
> -                               }
> +               if (rx_pkts == 0 && need_flush) {
> +                       for (i = 0; i < ports->num_ports; i++) {
> +                               uint16_t port = ports->id[i];
> +
> +                               sent = rte_eth_tx_buffer_flush(port,
> +                                                              client_id,
> +
> tx_buffer[port]);
> +                               tx_stats->tx[port] += sent;
> +                       }
>                         need_flush = 0;
>                         continue;
>                 }
>
>
Woh, had to concentrate to see that the pb was when accessing tx_buffer[]
and tx_stats->tx[] arrays, good catch :-)

Reviewed-by: David Marchand <david.marchand@redhat.com>