netdev-dpdk: use rte_eth_dev_set_mtu.

DPDK provides an API to set the MTU of compatible physical devices -
rte_eth_dev_set_mtu(). Prior to DPDK v16.07 however, this API was not
implemented in some DPDK PMDs (i40e, specifically). To allow the use
of jumbo frames with affected NICs in OvS-DPDK, MTU configuration was
achieved by setting the jumbo frame flag, and corresponding maximum
permitted Rx frame size, in an rte_eth_conf structure for the NIC
port, and subsequently invoking rte_eth_dev_configure() with that
configuration.

However, that method does not set the MTU field of the underlying DPDK
structure (rte_eth_dev) for the corresponding physical device;
consequently, rte_eth_dev_get_mtu() reports the incorrect MTU for an
OvS-DPDK phy device with non-standard MTU.

Resolve this issue by invoking rte_eth_dev_set_mtu() when setting up
or modifying the MTU of a DPDK phy port.

Fixes: 0072e93 ("netdev-dpdk: add support for jumbo frames")
Reported-by: Aaron Conole <[email protected]>
Reported-by: Vipin Varghese <[email protected]>
Reviewed-by: Aaron Conole <[email protected]>
Acked-by: Sugesh Chandran <[email protected]>
Tested-by: Sugesh Chandran <[email protected]>
Signed-off-by: Mark Kavanagh <[email protected]>
Signed-off-by: Darrell Ball <[email protected]>
Signed-off-by: Ben Pfaff <[email protected]>

lib/netdev-dpdk.c

@@ -650,13 +650,12 @@ dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev, int n_rxq, int n_txq)
     int i;
     struct rte_eth_conf conf = port_conf;
 
+    /* For some NICs (e.g. Niantic), scatter_rx mode needs to be explicitly
+     * enabled. */
     if (dev->mtu > ETHER_MTU) {
-        conf.rxmode.jumbo_frame = 1;
-        conf.rxmode.max_rx_pkt_len = dev->max_packet_len;
-    } else {
-        conf.rxmode.jumbo_frame = 0;
-        conf.rxmode.max_rx_pkt_len = 0;
+        conf.rxmode.enable_scatter = 1;
     }
+
     conf.rxmode.hw_ip_checksum = (dev->hw_ol_features &
                                   NETDEV_RX_CHECKSUM_OFFLOAD) != 0;
     /* A device may report more queues than it makes available (this has
@@ -676,6 +675,13 @@ dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev, int n_rxq, int n_txq)
             break;
         }
 
+        diag = rte_eth_dev_set_mtu(dev->port_id, dev->mtu);
+        if (diag) {
+            VLOG_ERR("Interface %s MTU (%d) setup error: %s",
+                    dev->up.name, dev->mtu, rte_strerror(-diag));
+            break;
+        }
+
         for (i = 0; i < n_txq; i++) {
             diag = rte_eth_tx_queue_setup(dev->port_id, i, dev->txq_size,
                                           dev->socket_id, NULL);