[dpdk-dev] [PATCH v2] examples/multi_process - fix crash in mp_client with sparse ports

[Stephen Hemminger <stephen@networkplumber.org>]

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.

Also:
   - the flush code is common enough that it should not be marked
     unlikely
   - combine conditions to reduce indentation
   - 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       | 19 ++++++++++---------
 1 file changed, 10 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..db9ebbe2402a 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 +246,20 @@ 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]);
+				if (unlikely(sent))
+					tx_stats->tx[port] += sent;
+			}
 			need_flush = 0;
 			continue;
 		}
-- 
2.20.1