[dpdk-stable] [PATCH] app/testpmd: fix random number of Tx segments

[Alvin Zhang <alvinx.zhang@intel.com>]

When random number of segments in Tx packets is enabled,
the total data space length of all segments must be greater
or equal than the size of an Eth/IP/UDP/timestamp packet,
that's total 14 + 20 + 8 + 16 bytes. Otherwise the Tx engine
may cause the application to crash.

Bugzilla ID: 797
Fixes: 79bec05b32b7 ("app/testpmd: add ability to split outgoing packets")
Cc: stable@dpdk.org

Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
---
 app/test-pmd/config.c  | 16 +++++++++++-----
 app/test-pmd/testpmd.c |  5 +++++
 app/test-pmd/testpmd.h |  5 +++++
 app/test-pmd/txonly.c  |  7 +++++--
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
index 31d8ba1..5105b3b 100644
--- a/app/test-pmd/config.c
+++ b/app/test-pmd/config.c
@@ -3837,10 +3837,11 @@ struct igb_ring_desc_16_bytes {
 	 * Check that each segment length is greater or equal than
 	 * the mbuf data size.
 	 * Check also that the total packet length is greater or equal than the
-	 * size of an empty UDP/IP packet (sizeof(struct rte_ether_hdr) +
-	 * 20 + 8).
+	 * size of an Eth/IP/UDP + timestamp packet
+	 * (sizeof(struct rte_ether_hdr) + 20 + 8 + 16).
 	 */
 	tx_pkt_len = 0;
+	tx_pkt_nb_min_segs = 0;
 	for (i = 0; i < nb_segs; i++) {
 		if (seg_lengths[i] > mbuf_data_size[0]) {
 			fprintf(stderr,
@@ -3849,11 +3850,16 @@ struct igb_ring_desc_16_bytes {
 			return;
 		}
 		tx_pkt_len = (uint16_t)(tx_pkt_len + seg_lengths[i]);
+
+		if (!tx_pkt_nb_min_segs &&
+		    tx_pkt_len >= (sizeof(struct rte_ether_hdr) + 20 + 8 + 16))
+			tx_pkt_nb_min_segs = i + 1;
 	}
-	if (tx_pkt_len < (sizeof(struct rte_ether_hdr) + 20 + 8)) {
+
+	if (!tx_pkt_nb_min_segs) {
 		fprintf(stderr, "total packet length=%u < %d - give up\n",
-				(unsigned) tx_pkt_len,
-				(int)(sizeof(struct rte_ether_hdr) + 20 + 8));
+			(unsigned int) tx_pkt_len,
+			(int)(sizeof(struct rte_ether_hdr) + 20 + 8 + 16));
 		return;
 	}
 
diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
index 6cbe9ba..c496e59 100644
--- a/app/test-pmd/testpmd.c
+++ b/app/test-pmd/testpmd.c
@@ -232,6 +232,11 @@ struct fwd_engine * fwd_engines[] = {
 };
 uint8_t  tx_pkt_nb_segs = 1; /**< Number of segments in TXONLY packets */
 
+/**< Minimum number of segments in TXONLY packets to accommodate all packet
+ * headers.
+ */
+uint8_t  tx_pkt_nb_min_segs = 1;
+
 enum tx_pkt_split tx_pkt_split = TX_PKT_SPLIT_OFF;
 /**< Split policy for packets to TX. */
 
diff --git a/app/test-pmd/testpmd.h b/app/test-pmd/testpmd.h
index 16a3598..f5bc427 100644
--- a/app/test-pmd/testpmd.h
+++ b/app/test-pmd/testpmd.h
@@ -464,6 +464,11 @@ enum dcb_mode_enable
 extern uint16_t tx_pkt_length; /**< Length of TXONLY packet */
 extern uint16_t tx_pkt_seg_lengths[RTE_MAX_SEGS_PER_PKT]; /**< Seg. lengths */
 extern uint8_t  tx_pkt_nb_segs; /**< Number of segments in TX packets */
+
+/**< Minimum number of segments in TXONLY packets to accommodate all packet
+ * headers.
+ */
+extern uint8_t  tx_pkt_nb_min_segs;
 extern uint32_t tx_pkt_times_intra;
 extern uint32_t tx_pkt_times_inter;
 
diff --git a/app/test-pmd/txonly.c b/app/test-pmd/txonly.c
index aed820f..27e4458 100644
--- a/app/test-pmd/txonly.c
+++ b/app/test-pmd/txonly.c
@@ -195,8 +195,11 @@
 	uint32_t nb_segs, pkt_len;
 	uint8_t i;
 
-	if (unlikely(tx_pkt_split == TX_PKT_SPLIT_RND))
-		nb_segs = rte_rand() % tx_pkt_nb_segs + 1;
+	if (unlikely(tx_pkt_split == TX_PKT_SPLIT_RND) &&
+	    tx_pkt_nb_segs > tx_pkt_nb_min_segs)
+		nb_segs = rte_rand() %
+			  (tx_pkt_nb_segs - tx_pkt_nb_min_segs + 1) +
+			  tx_pkt_nb_min_segs;
 	else
 		nb_segs = tx_pkt_nb_segs;
 
-- 
1.8.3.1