This patch checks the feature bit for the VIRTIO_NET_F_MTU feature. If it
exists, read the advised MTU and use it.
No proper error handling is provided for the case where a user changes the
negotiated MTU. A future commit will add proper error handling. Instead, a
warning is emitted if the guest changes the device MTU after previously being
given advice.
Signed-off-by: Aaron Conole <aconole@xxxxxxxxxx>
---
drivers/net/virtio_net.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 767ab11..7175563 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -146,6 +146,7 @@ struct virtnet_info {
virtio_net_ctrl_ack ctrl_status;
u8 ctrl_promisc;
u8 ctrl_allmulti;
+ bool negotiated_mtu;
};
struct padded_vnet_hdr {
@@ -1390,8 +1391,12 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
{
+ struct virtnet_info *vi = netdev_priv(dev);
if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
return -EINVAL;
+ if (vi->negotiated_mtu == true) {
+ pr_warn("changing mtu from negotiated mtu.");
+ }
dev->mtu = new_mtu;
return 0;
}
@@ -1836,6 +1841,13 @@ static int virtnet_probe(struct virtio_device *vdev)
if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_VQ))
vi->has_cvq = true;
+ if (virtio_has_feature(vdev, VIRTIO_NET_F_MTU)) {
+ vi->negotiated_mtu = true;
+ dev->mtu = virtio_cread16(vdev,
+ offsetof(struct virtio_net_config,
+ mtu));
+ }
+
if (vi->any_header_sg)
dev->needed_headroom = vi->hdr_len;
@@ -2017,8 +2029,9 @@ static unsigned int features[] = {
VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ,
- VIRTIO_NET_F_CTRL_MAC_ADDR,
+ VIRTIO_NET_F_CTRL_MAC_ADDR,
VIRTIO_F_ANY_LAYOUT,
+ VIRTIO_NET_F_MTU,
};
static struct virtio_driver virtio_net_driver = {
--
2.5.0
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