xref: /dflybsd-src/share/man/man4/vtnet.4 (revision dddbf4cd54036c88ab90de54668f542d70b771b0)

.\" Copyright (c) 2011 Bryan Venteicher
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.\" $FreeBSD: head/share/man/man4/vtnet.4 255112 2013-09-01 04:33:47Z bryanv $
.\"
.Dd October 17, 2017
.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 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
.\".It Va hw.vtnet. Ns Ar X Ns Va .csum_disable
This tunable disables receive and send checksum offload.
The default value is 0.
.It Va hw.vtnet.tso_disable
.\".It Va hw.vtnet. Ns Ar X Ns Va .tso_disable
This tunable disables TSO.
The default value is 1.
.It Va hw.vtnet.lro_disable
.\".It Va hw.vtnet. Ns Ar X Ns Va .lro_disable
This tunable disables LRO.
The default value is 0.
.\".It Va hw.vtnet.mq_disable
.\".It Va hw.vtnet. Ns Ar X Ns Va .mq_disable
.\"This tunable disables multiqueue.
.\"The default value is 0.
.\".It Va hw.vtnet.mq_max_pairs
.\".It Va hw.vtnet. Ns Ar X Ns Va .mq_max_pairs
.\"This tunable sets the maximum number of transmit and receive queue pairs.
.\"Multiple queues are only supported when the Multiqueue feature is negotiated.
.\"This driver supports a maximum of 8 queue pairs.
.\"The number of queue pairs used is the lesser of the maximum supported by the
.\"driver and the hypervisor, the number of CPUs present in the guest, and this
.\"tunable if not zero.
.\"The default value is 0.
.El
.Sh SEE ALSO
.Xr arp 4 ,
.Xr ifmedia 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 Mt bryanv@FreeBSD.org .
It first appeared in
.Fx 9.0 .
.Sh CAVEATS
The
.Nm
driver only supports LRO when the hypervisor advertises the
mergeable buffer feature.
The receive checksum offload feature of the
.Nm
driver is masked for now, because of missing support for receive checksum
offload in IPv6 packet handling in
.Dx .