[PATCH v3 4/6] net/tap: add MTU management

[Pascal Mazon <pascal.mazon@6wind.com>]

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.

Signed-off-by: Pascal Mazon <pascal.mazon@6wind.com>
---
 doc/guides/nics/features/tap.ini |  1 +
 drivers/net/tap/rte_eth_tap.c    | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/doc/guides/nics/features/tap.ini b/doc/guides/nics/features/tap.ini
index 6878a9b8fd17..6aa11874e2bc 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
 Multicast MAC filter = Y
 Speed capabilities   = Y
 Unicast MAC filter   = Y
diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 301072f20930..d76f1dc83b03 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -733,6 +733,42 @@ tap_set_mc_addr_list(struct rte_eth_dev *dev __rte_unused,
 	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;
+	int err, s;
+
+	s = socket(AF_INET, SOCK_DGRAM, 0);
+	if (s < 0) {
+		RTE_LOG(ERR, PMD,
+			"Unable to get a socket for %s to set flags: %s\n",
+			pmd->name, strerror(errno));
+		return -1;
+	}
+	memset(&ifr, 0, sizeof(ifr));
+	snprintf(ifr.ifr_name, IFNAMSIZ, "%s", pmd->name);
+	err = ioctl(s, SIOCGIFMTU, &ifr);
+	if (err < 0) {
+		RTE_LOG(WARNING, PMD, "Unable to get %s device MTU: %s\n",
+			pmd->name, strerror(errno));
+		close(s);
+		return -1;
+	}
+	ifr.ifr_mtu = mtu;
+	err = ioctl(s, SIOCSIFMTU, &ifr);
+	if (err < 0) {
+		RTE_LOG(WARNING, PMD, "Unable to set %s mtu %d: %s\n",
+			pmd->name, mtu, strerror(errno));
+		close(s);
+		return -1;
+	}
+	close(s);
+	dev->data->mtu = mtu;
+	return 0;
+}
+
 static const struct eth_dev_ops ops = {
 	.dev_start              = tap_dev_start,
 	.dev_stop               = tap_dev_stop,
@@ -754,6 +790,7 @@ static const struct eth_dev_ops ops = {
 	.mac_addr_add           = tap_mac_add,
 	.mac_addr_set           = tap_mac_set,
 	.set_mc_addr_list       = tap_set_mc_addr_list,
+	.mtu_set                = tap_mtu_set,
 	.stats_get              = tap_stats_get,
 	.stats_reset            = tap_stats_reset,
 };
-- 
2.8.0.rc0