[PATCH v3 1/2] net/mana: fix transmit burst error handling

[Tathagat Priyadarshi]

mana_tx_burst() skipped, using continue, a packet that exceeded the
segment limit or whose SGL could not be populated. rte_eth_tx_burst()
callers treat the return value as a contiguous prefix of consumed
packets, so later packets were posted while the caller considered them
unsent and freed them, and their completions then freed them again.

Drop such a packet instead: count it in stats.errors, free it and
include it in the returned count. Return early only when the ring is
full, since a packet that fails validation would fail again on every
retry and stall applications that loop until all packets are sent.

sgl.gdma_sgl[] holds MAX_SGL_ENTRIES_FOR_TRANSMIT entries, but
max_send_sge comes from the device and was not limited, so a packet with
more segments could write past the array. Reject such packets and limit
the advertised nb_seg_max and nb_mtu_seg_max to the same value.

Fixes: 7f322844f427 ("net/mana: send packets")
Fixes: d878cb09501d ("net/mana: report device info")
Cc: stable at dpdk.org

Signed-off-by: Tathagat Priyadarshi <tathagat.dpdk at gmail.com>
---
v2:
- Drop unsendable packets and return a separate consumed count (nb_done)
  instead of breaking out of the burst; break only when the ring is full.
- Move MAX_SGL_ENTRIES_FOR_TRANSMIT clamp from patch 2 to patch 1, and
  clamp dev_info nb_seg_max and nb_mtu_seg_max.

 drivers/net/mana/mana.c |  4 ++--
 drivers/net/mana/tx.c   | 18 ++++++++++++++----
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/mana/mana.c b/drivers/net/mana/mana.c
index 30b0ce90d6..5ddbbdc3d0 100644
--- a/drivers/net/mana/mana.c
+++ b/drivers/net/mana/mana.c
@@ -410,9 +410,9 @@ mana_dev_info_get(struct rte_eth_dev *dev,
 	dev_info->tx_desc_lim.nb_max = RTE_MIN(priv->max_tx_desc, UINT16_MAX);
 	dev_info->tx_desc_lim.nb_align = MIN_BUFFERS_PER_QUEUE;
 	dev_info->tx_desc_lim.nb_seg_max =
-		RTE_MIN(priv->max_send_sge, UINT16_MAX);
+		RTE_MIN(priv->max_send_sge, MAX_SGL_ENTRIES_FOR_TRANSMIT);
 	dev_info->tx_desc_lim.nb_mtu_seg_max =
-		RTE_MIN(priv->max_send_sge, UINT16_MAX);
+		RTE_MIN(priv->max_send_sge, MAX_SGL_ENTRIES_FOR_TRANSMIT);
 
 	/* Speed */
 	dev_info->speed_capa = RTE_ETH_LINK_SPEED_100G;
diff --git a/drivers/net/mana/tx.c b/drivers/net/mana/tx.c
index 10f2212b5d..16e63e89c9 100644
--- a/drivers/net/mana/tx.c
+++ b/drivers/net/mana/tx.c
@@ -192,6 +192,7 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	int ret;
 	void *db_page;
 	uint16_t pkt_sent = 0;
+	uint16_t nb_done = 0;
 	uint32_t num_comp, i;
 	uint32_t expected = 0;
 #ifdef RTE_ARCH_32
@@ -278,10 +279,11 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			break;
 
 		/* Drop the packet if it exceeds max segments */
-		if (m_pkt->nb_segs > priv->max_send_sge) {
+		if (unlikely(m_pkt->nb_segs > priv->max_send_sge ||
+			     m_pkt->nb_segs > MAX_SGL_ENTRIES_FOR_TRANSMIT)) {
 			DP_LOG(ERR, "send packet segments %d exceeding max",
 			       m_pkt->nb_segs);
-			continue;
+			goto drop;
 		}
 
 		/* Fill in the oob */
@@ -432,7 +434,7 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 
 		/* Skip this packet if we can't populate all segments */
 		if (seg_idx != m_pkt->nb_segs)
-			continue;
+			goto drop;
 
 		/* If we can at least queue post two WQEs and there are at
 		 * least two packets to send, use TX CQE suppression for the
@@ -477,6 +479,7 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			txq->desc_ring_len++;
 
 			pkt_sent++;
+			nb_done++;
 
 			DP_LOG(DEBUG, "nb_pkts %u pkt[%d] sent",
 			       nb_pkts, pkt_idx);
@@ -499,6 +502,13 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 			       pkt_idx, ret);
 			break;
 		}
+
+		continue;
+
+drop:
+		txq->stats.errors++;
+		rte_pktmbuf_free(m_pkt);
+		nb_done++;
 	}
 
 	/* Ring hardware door bell */
@@ -523,5 +533,5 @@ mana_tx_burst(void *dpdk_txq, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 	rte_atomic_fetch_and_explicit(&txq->burst_state, ~(uint32_t)1,
 				     rte_memory_order_release);
 
-	return pkt_sent;
+	return nb_done;
 }
-- 
2.43.0