[dpdk-stable] patch 'ethdev: fix max Rx packet length check' has been queued to stable release 20.11.1

[luca.boccassi at gmail.com]

Hi,

FYI, your patch has been queued to stable release 20.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 02/07/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/bluca/dpdk-stable

This queued commit can be viewed at:
https://github.com/bluca/dpdk-stable/commit/be78a4db33176cc20cea883d2702972ac60aa8b4

Thanks.

Luca Boccassi

---
>From be78a4db33176cc20cea883d2702972ac60aa8b4 Mon Sep 17 00:00:00 2001
From: Steve Yang <stevex.yang at intel.com>
Date: Mon, 18 Jan 2021 07:04:07 +0000
Subject: [PATCH] ethdev: fix max Rx packet length check

[ upstream commit bf0f90d92d3010431c9187ed9a2b412030cded4e ]

Ethdev is using default Ethernet overhead to decide if provided
'max_rx_pkt_len' value is bigger than max (non jumbo) MTU value,
and limits it to MAX if it is.

Since the application/driver used Ethernet overhead is different than
the ethdev one, check result is wrong.

If the driver is using Ethernet overhead bigger than the default one,
the provided 'max_rx_pkt_len' is trimmed down, and in the driver when
correct Ethernet overhead is used to convert back, the resulting MTU is
less than the intended one, causing some packets to be dropped.

Like,
app     -> max_rx_pkt_len = 1500/*mtu*/ + 22/*overhead*/ = 1522
ethdev  -> 1522 > 1518/*MAX*/; max_rx_pkt_len = 1518
driver  -> MTU = 1518 - 22 = 1496
Packets with size 1497-1500 are dropped although intention is to be able
to send/receive them.

The fix is to make ethdev use the correct Ethernet overhead for port,
instead of default one.

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

Signed-off-by: Steve Yang <stevex.yang at intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit at intel.com>
---
 lib/librte_ethdev/rte_ethdev.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
index 17ddacc78d..71e1e9a6db 100644
--- a/lib/librte_ethdev/rte_ethdev.c
+++ b/lib/librte_ethdev/rte_ethdev.c
@@ -1292,8 +1292,10 @@ 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;
+	uint16_t old_mtu;
 
 	RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
 
@@ -1319,10 +1321,20 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
 		memcpy(&dev->data->dev_conf, dev_conf,
 		       sizeof(dev->data->dev_conf));
 
+	/* Backup mtu for rollback */
+	old_mtu = dev->data->mtu;
+
 	ret = rte_eth_dev_info_get(port_id, &dev_info);
 	if (ret != 0)
 		goto rollback;
 
+	/* Get the real Ethernet overhead length */
+	if (dev_info.max_mtu != UINT16_MAX &&
+	    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.
@@ -1409,12 +1421,17 @@ rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_q, uint16_t nb_tx_q,
 			ret = -EINVAL;
 			goto rollback;
 		}
+
+		/* Scale the MTU size to adapt max_rx_pkt_len */
+		dev->data->mtu = dev->data->dev_conf.rxmode.max_rx_pkt_len -
+				overhead_len;
 	} 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;
 	}
 
 	/*
@@ -1549,6 +1566,8 @@ reset_queues:
 	eth_dev_tx_queue_config(dev, 0);
 rollback:
 	memcpy(&dev->data->dev_conf, &orig_conf, sizeof(dev->data->dev_conf));
+	if (old_mtu != dev->data->mtu)
+		dev->data->mtu = old_mtu;
 
 	rte_ethdev_trace_configure(port_id, nb_rx_q, nb_tx_q, dev_conf, ret);
 	return ret;
-- 
2.29.2

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-02-05 11:18:35.689108179 +0000
+++ 0143-ethdev-fix-max-Rx-packet-length-check.patch	2021-02-05 11:18:29.030695376 +0000
@@ -1 +1 @@
-From bf0f90d92d3010431c9187ed9a2b412030cded4e Mon Sep 17 00:00:00 2001
+From be78a4db33176cc20cea883d2702972ac60aa8b4 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit bf0f90d92d3010431c9187ed9a2b412030cded4e ]
+
@@ -29 +30,0 @@
-Cc: stable at dpdk.org
@@ -38 +39 @@
-index e19dbd838b..9fe1c9d769 100644
+index 17ddacc78d..71e1e9a6db 100644