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.\"
.\" Copyright (c) 2016 Alexander Motin <mav@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" $FreeBSD$
.\"
.Dd July 29, 2016
.Dt IF_NTB 4
.Os
.Sh NAME
.Nm if_ntb
.Nd Virtual Ethernet interface for Non-Transparent Bridges
.Sh SYNOPSIS
To compile this driver into your kernel,
place the following lines in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "device if_ntb"
.Ed
.Pp
Or, to load the driver as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
if_ntb_load="YES"
.Ed
.Pp
The following tunables are settable from the
.Xr loader 8 :
.Bl -ohang
.It Va hw.if_ntb.num_queues
Number of transport queues to use per interface.
Default is unlimited.
.El
.Sh DESCRIPTION
The
.Nm
driver attaches on top of the
.Xr ntb_transport 4
driver to utilize its resources to create virtual Ethernet interface between
the systems.
Interface capabilities depend on the underlying transport.
Typical MTU is about 64KB to reduce overhead.
By default one queue is used, but more may be configured.
The MAC address for interface is randomly generated.
.Pp
The
.Nm
driver does not implement any real hardware offload, but since PCIe link is
protected by CRC32, in some situations it may be possible to save some CPU
cycles by enabling fake checksum offload on both link sides via setting
.Cm rxcsum
and
.Cm txcsum
interface options.
.Sh SEE ALSO
.Xr ntb_transport 4
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was developed by Intel and originally written by
.An Carl Delsey Aq Mt carl@FreeBSD.org .
Later improvements were done by
.An Conrad E. Meyer Aq Mt cem@FreeBSD.org
and
.An Alexander Motin Aq Mt mav@FreeBSD.org .
.Sh BUGS
Linux supports only one queue per interface, so manual configuration
may be required for compatibility.