[dpdk-dev] [PATCH v4 4/8] net/tap: add MTU management

[Pascal Mazon]

The MTU is assigned to the tap netdevice according to the argument, but
packet transmission and reception just write/read on an fd with the
default limit being the socket buffer size.

As a new rte_eth_dev_data is allocated during tap device init, ensure it
is set again dev->data->mtu.
Once the actual netdevice is created via tun_alloc(), make sure to apply
the desired MTU to the netdevice.

Signed-off-by: Pascal Mazon <pascal.mazon at 6wind.com>
---
 doc/guides/nics/features/tap.ini |  1 +
 drivers/net/tap/rte_eth_tap.c    | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/doc/guides/nics/features/tap.ini b/doc/guides/nics/features/tap.ini
index d9b47a003654..b80577753240 100644
--- a/doc/guides/nics/features/tap.ini
+++ b/doc/guides/nics/features/tap.ini
@@ -9,6 +9,7 @@ Jumbo frame          = Y
 Promiscuous mode     = Y
 Allmulticast mode    = Y
 Basic stats          = Y
+MTU update           = Y
 Unicast MAC filter   = Y
 Other kdrv           = Y
 ARMv7                = Y
diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 06c1faa92dce..3e61f7bda555 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -302,6 +302,7 @@ tap_ioctl(struct pmd_internals *pmd, unsigned long request,
 		break;
 	case SIOCGIFHWADDR:
 	case SIOCSIFHWADDR:
+	case SIOCSIFMTU:
 		break;
 	default:
 		RTE_LOG(WARNING, PMD, "%s: ioctl() called with wrong arg\n",
@@ -547,6 +548,15 @@ tap_setup_queue(struct rte_eth_dev *dev,
 					pmd->name, qid);
 				return -1;
 			}
+			if (qid == 0) {
+				struct ifreq ifr;
+
+				ifr.ifr_mtu = dev->data->mtu;
+				if (tap_ioctl(pmd, SIOCSIFMTU, &ifr, 1) < 0) {
+					close(fd);
+					return -1;
+				}
+			}
 		}
 	}
 
@@ -642,6 +652,20 @@ tap_tx_queue_setup(struct rte_eth_dev *dev,
 	return 0;
 }
 
+static int
+tap_mtu_set(struct rte_eth_dev *dev, uint16_t mtu)
+{
+	struct pmd_internals *pmd = dev->data->dev_private;
+	struct ifreq ifr = { .ifr_mtu = mtu };
+	int err = 0;
+
+	err = tap_ioctl(pmd, SIOCSIFMTU, &ifr, 1);
+	if (!err)
+		dev->data->mtu = mtu;
+
+	return err;
+}
+
 static const struct eth_dev_ops ops = {
 	.dev_start              = tap_dev_start,
 	.dev_stop               = tap_dev_stop,
@@ -660,6 +684,7 @@ static const struct eth_dev_ops ops = {
 	.allmulticast_enable    = tap_allmulti_enable,
 	.allmulticast_disable   = tap_allmulti_disable,
 	.mac_addr_set           = tap_mac_set,
+	.mtu_set                = tap_mtu_set,
 	.stats_get              = tap_stats_get,
 	.stats_reset            = tap_stats_reset,
 };
@@ -710,6 +735,7 @@ eth_dev_tap_create(const char *name, char *tap_name)
 	/* Setup some default values */
 	data->dev_private = pmd;
 	data->port_id = dev->data->port_id;
+	data->mtu = dev->data->mtu;
 	data->dev_flags = RTE_ETH_DEV_DETACHABLE;
 	data->kdrv = RTE_KDRV_NONE;
 	data->drv_name = pmd_tap_drv.driver.name;
-- 
2.8.0.rc0