VTNET(4)

NAME
vtnet - VirtIO Ethernet driver

SYNOPSIS
To compile this driver into the kernel, place the following lines in your kernel configuration file:

device vtnet

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

    if_vtnet_load="YES"

DESCRIPTION
The vtnet device driver provides support for VirtIO Ethernet devices.

If the hypervisor advertises the appreciate features, the vtnet driver supports TCP/UDP checksum offload for both transmit and receive, TCP segmentation offload (TSO), TCP large receive offload (LRO), and hardware VLAN tag stripping/insertion features, as well as a multicast hash filter, as well as Jumbo Frames (up to 9216 bytes), which can be configured via the interface MTU setting. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit Jumbo Frames.

For more information on configuring this device, see ifconfig(8).

LOADER TUNABLES
Tunables can be set at the loader(8) prompt before booting the kernel or stored in loader.conf(5).

hw.vtnet.csum_disable
    This tunable disables receive and send checksum offload. The default value is 0.

hw.vtnet.tso_disable
    This tunable disables TSO. The default value is 1.

hw.vtnet.lro_disable
    This tunable disables LRO. The default value is 0.

SEE ALSO
arp(4), ifmedia(4), netintro(4), ng_ether(4), virtio(4), vlan(4), ifconfig(8)

HISTORY
The vtnet driver was written by Bryan Venteicher <bryanv@FreeBSD.org>. It first appeared in FreeBSD 9.0.

CAVEATS
The vtnet driver only supports LRO when the hypervisor advertises the mergeable buffer feature. The receive checksum offload feature of the vtnet driver is masked for now, because of missing support for receive checksum offload in IPv6 packet handling in DragonFly.