freebsd-skq/share/man/man4/vtnet.4

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.Dd January 22, 2012
.Dt VTNET 4
.Os
.Sh NAME
.Nm vtnet
.Nd VirtIO Ethernet driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device if_vtnet"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_vtnet_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
device driver provides support for VirtIO Ethernet devices.
.Pp
If the hypervisor advertises the appreciate features, the
.Nm
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
.Xr ifconfig 8
utility configures the adapter to receive and transmit Jumbo Frames.
.Pp
For more information on configuring this device, see
.Xr ifconfig 8 .
.Sh LOADER TUNABLES
Tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Xr loader.conf 5 .
.Bl -tag -width "xxxxxx"
.It Va hw.vtnet.csum_disable
This tunable disables receive and send checksum offload.
The default value is 0.
.It Va hw.vtnet.tso_disable
This tunable disables TSO.
The default value is 0.
.It Va hw.vtnet.lro_disable
This tunable disables LRO.
The default value is 0.
.El
.Sh SEE ALSO
.Xr arp 4 ,
.Xr netintro 4 ,
.Xr ng_ether 4 ,
.Xr virtio 4 ,
.Xr vlan 4 ,
.Xr ifconfig 8
.Sh HISTORY
The
.Nm
driver was written by
.An Bryan Venteicher Aq bryanv@daemoninthecloset.org .
It first appeared in
.Fx 9.0 .
.Sh CAVEATS
The
.Nm
driver only supports LRO when the hypervisor advertises the
mergeable buffer feature.