[PATCH] examples/packet_ordering: fix segfault in disable_reorder mode

[Qian Hao <qi_an_hao@126.com>]

packet_ordering example works in two modes (--disable-reorder):
  - When reorder is enabled: rx_thread - N*worker_thread - send_thread
  - When reorder is disabled: rx_thread - N*worker_thread - tx_thread
N parallel worker_thread(s) generate out-of-order packets.

When reorder is enabled, send_thread uses sequence number generated in rx_thread (Line 459) to enforce packet ordering. Otherwise rx_thread just sends any packet it receives.

rx_thread writes sequence number into a dynamic field, which is only registered by calling rte_reorder_create() (Line 741) when reorder is enabled. However, rx_thread marks sequence number onto each packet no matter whether reorder is enabled, overwriting the leading bytes in packet mbufs when reorder is disabled, resulting in segfaults when PMD tries to DMA packets.

if (!disable_reorder) {...} is added to fix the bug.
---
 examples/packet_ordering/main.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/examples/packet_ordering/main.c b/examples/packet_ordering/main.c
index d2fd6f77e4..7688f541ba 100644
--- a/examples/packet_ordering/main.c
+++ b/examples/packet_ordering/main.c
@@ -455,8 +455,11 @@ rx_thread(struct rte_ring *ring_out)
 				app_stats.rx.rx_pkts += nb_rx_pkts;
 
 				/* mark sequence number */
-				for (i = 0; i < nb_rx_pkts; )
-					*rte_reorder_seqn(pkts[i++]) = seqn++;
+				if (!disable_reorder) {
+					for (i = 0; i < nb_rx_pkts;) {
+						*rte_reorder_seqn(pkts[i++]) = seqn++;              
+					}
+				}
 
 				/* enqueue to rx_to_workers ring */
 				ret = rte_ring_enqueue_burst(ring_out,
-- 
2.34.1