.\"     $OpenBSD: vio.4,v 1.16 2021/05/24 17:29:56 dv Exp $
.\"
.\" Copyright (c) 2012 Stefan Fritsch <sf@sfritsch.de>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: May 24 2021 $
.Dt VIO 4
.Os
.Sh NAME
.Nm vio
.Nd VirtIO network device
.Sh SYNOPSIS
.Cd "vio* at virtio? flags 0x00"
.Sh DESCRIPTION
The
.Nm
driver provides support for the
.Xr virtio 4
network interface provided by bhyve, KVM, QEMU, VirtualBox, and
.Xr vmd 8 .
.Pp
Setting the bit 0x2 in the flags disables the RingEventIndex feature.
This can be tried as a workaround for possible bugs in host implementations of
.Nm
at the cost of slightly reduced performance.
.Pp
Setting the bit 0x100 in the flags forces the interface to be always in
promiscuous mode.
This can be used as a workaround for a bug in QEMU before version 1.7.2 that
prevents packets with a VLAN tag from being sent to the guest.
.Sh SEE ALSO
.Xr intro 4 ,
.Xr virtio 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 5.3 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was ported to
.Ox
and improved by
.An Stefan Fritsch Aq Mt sf@sfritsch.de .
It is based on the
.Nx
.Nm vioif
driver by
.An Minoura Makoto .