[dpdk-dev] [PATCH 4/7] vhost: Add API to get/set MTU value

[Maxime Coquelin <maxime.coquelin@redhat.com>]

This patch implements two functions for the application to
get/set the MTU value.

rte_vhost_mtu_get() set the mtu parameter with the MTU value
set in QEMU if VIRTIO_NET_F_MTU has been negotiated and returns 0,
-ENOTSUP otherwise.

rte_vhost_mtu_set() doesn't actually permit to change the MTU,
which can only be set once before feature negotiation, but the
function returns 0 if the MTU value the application tries to set
is the same that have been set in QEMU, -EINVAL if different and
-ENOTSUP if VIRTIO_NET_F_MTU hasn't been negotiated.

The two functions returns -EAGAIN if Virtio feature negotiation
didn't happened yet.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 lib/librte_vhost/rte_virtio_net.h | 31 +++++++++++++++++++++++++++++++
 lib/librte_vhost/vhost.c          | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+)

diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
index 926039c..8d84dbf 100644
--- a/lib/librte_vhost/rte_virtio_net.h
+++ b/lib/librte_vhost/rte_virtio_net.h
@@ -100,6 +100,37 @@ int rte_vhost_driver_callback_register(struct virtio_net_device_ops const * cons
 int rte_vhost_driver_session_start(void);
 
 /**
+ * Get the MTU value of the device if set in QEMU.
+ *
+ * @param vid
+ *  virtio-net device ID
+ * @param mtu
+ *  The variable to store the MTU value
+ *
+ * @return
+ *  0: success
+ *  -EAGAIN: device not yet started
+ *  -ENOTSUP: device does not support MTU feature
+ */
+int rte_vhost_mtu_get(int vid, uint16_t *mtu);
+
+/**
+ * Set the MTU value of the device.
+ *
+ * @param vid
+ *  virtio-net device ID
+ * @param mtu
+ *  The MTU value
+ *
+ * @return
+ *  0: success
+ *  -EAGAIN: device not yet started
+ *  -ENOTSUP: device does not support MTU feature
+ *  -EINVAL: MTU value different from the one set in QEMU
+ */
+int rte_vhost_mtu_set(int vid, uint16_t mtu);
+
+/**
  * Get the numa node from which the virtio net device's memory
  * is allocated.
  *
diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
index 3974087..20d0061 100644
--- a/lib/librte_vhost/vhost.c
+++ b/lib/librte_vhost/vhost.c
@@ -313,6 +313,45 @@ vhost_enable_dequeue_zero_copy(int vid)
 }
 
 int
+rte_vhost_mtu_get(int vid, uint16_t *mtu)
+{
+	struct virtio_net *dev = get_device(vid);
+
+	if (!dev)
+		return -ENODEV;
+
+	if (!(dev->flags & VIRTIO_DEV_READY))
+		return -EAGAIN;
+
+	if (!(dev->features & VIRTIO_NET_F_MTU))
+		return -ENOTSUP;
+
+	*mtu = dev->mtu;
+
+	return 0;
+}
+
+int
+rte_vhost_mtu_set(int vid, uint16_t mtu)
+{
+	struct virtio_net *dev = get_device(vid);
+
+	if (!dev)
+		return -ENODEV;
+
+	if (!(dev->flags & VIRTIO_DEV_READY))
+		return -EAGAIN;
+
+	if (!(dev->features & VIRTIO_NET_F_MTU))
+		return -ENOTSUP;
+
+	if (dev->mtu != mtu)
+		return -EINVAL;
+
+	return 0;
+}
+
+int
 rte_vhost_get_numa_node(int vid)
 {
 #ifdef RTE_LIBRTE_VHOST_NUMA
-- 
2.9.3