[dpdk-dev] [PATCH v2 01/22] ethdev: fix MTU size exceeds max rx packet length

[Steve Yang]

If max rx packet length is smaller then MTU + Ether overhead, that will
drop all MTU size packets.

Update the MTU size according to the max rx packet and Ether overhead.

Fixes: 59d0ecdbf0e1 ("ethdev: MTU accessors")

Signed-off-by: Steve Yang <stevex.yang at intel.com>
---
 lib/librte_ethdev/rte_ethdev.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 17ddacc78d..ff6a1e675f 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -1292,6 +1292,7 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
 	struct rte_eth_dev *dev;
 	struct rte_eth_dev_info dev_info;
 	struct rte_eth_conf orig_conf;
+	uint16_t overhead_len;
 	int diag;
 	int ret;
 
@@ -1323,6 +1324,15 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
 	if (ret != 0)
 		goto rollback;
 
+	/* Get the real Ethernet overhead length */
+	if (dev_info.max_mtu &&
+	    dev_info.max_mtu != UINT16_MAX &&
+	    dev_info.max_rx_pktlen &&
+	    dev_info.max_rx_pktlen > dev_info.max_mtu)
+		overhead_len = dev_info.max_rx_pktlen - dev_info.max_mtu;
+	else
+		overhead_len = RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN;
+
 	/* If number of queues specified by application for both Rx and Tx is
 	 * zero, use driver preferred values. This cannot be done individually
 	 * as it is valid for either Tx or Rx (but not both) to be zero.
@@ -1410,13 +1420,18 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
 			goto rollback;
 		}
 	} else {
-		if (dev_conf->rxmode.max_rx_pkt_len < RTE_ETHER_MIN_LEN ||
-			dev_conf->rxmode.max_rx_pkt_len > RTE_ETHER_MAX_LEN)
+		uint16_t pktlen = dev_conf->rxmode.max_rx_pkt_len;
+		if (pktlen < RTE_ETHER_MIN_MTU + overhead_len ||
+			pktlen > RTE_ETHER_MTU + overhead_len)
 			/* Use default value */
 			dev->data->dev_conf.rxmode.max_rx_pkt_len =
-							RTE_ETHER_MAX_LEN;
+						RTE_ETHER_MTU + overhead_len;
 	}
 
+	/* Scale the MTU size to adapt max_rx_pkt_len */
+	dev->data->mtu = dev->data->dev_conf.rxmode.max_rx_pkt_len -
+				overhead_len;
+
 	/*
 	 * If LRO is enabled, check that the maximum aggregated packet
 	 * size is supported by the configured device.
-- 
2.17.1