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	1	.\"
	2	.\" Copyright (c) 2008 The DragonFly Project. All rights reserved.
	3	.\"
	4	.\" This code is derived from software contributed to The DragonFly Project
	5	.\" by Matthew Dillon <dillon@backplane.com>
	6	.\"
	7	.\" Redistribution and use in source and binary forms, with or without
	8	.\" modification, are permitted provided that the following conditions
	9	.\" are met:
	10	.\"
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in
	15	.\" the documentation and/or other materials provided with the
	16	.\" distribution.
	17	.\" 3. Neither the name of The DragonFly Project nor the names of its
	18	.\" contributors may be used to endorse or promote products derived
	19	.\" from this software without specific, prior written permission.
	20	.\"
	21	.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	22	.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	23	.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
	24	.\" FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
	25	.\" COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	26	.\" INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
	27	.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	28	.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
	29	.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	30	.\" OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	31	.\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" $DragonFly: src/usr.sbin/vknetd/vknetd.8,v 1.1 2008/05/27 01:58:01 dillon Exp $
	35	.\"
	36	.Dd May 26, 2008
	37	.Dt vknet 8
	38	.Os
	39	.Sh NAME
	40	.Nm vknet
	41	.Nd create a bridged network for (typically user-run) vkernel's
	42	.Sh SYNOPSIS
	43	.Nm
	44	.Op Fl cdU
	45	.Op Fl b Ar bridgeN
	46	.Op Fl p Ar socket_path
	47	.Op Fl t Ar tapN
	48	.Op Ar address/cidrbits
	49	.Sh DESCRIPTION
	50	The
	51	.Nm
	52	utility creates a virtualized bridged network suitable for vkernel use.
	53	The utility was created to simplify vkernel oprations and to allow user-run
	54	vkernels to have access to a network.
	55	General use is to specify a large 10-dot network which multiple vkernels are
	56	then able to connect to, and backfeed the whole mess to a TAP interface.
	57	.Pp
	58	A vkernel would make use of the virtualized network by specifying
	59	.Fl I Ar /dev/vknet
	60	instead of a
	61	.Xr tap 4
	62	interface.
	63	Any number of vkernels may connect to the virtual network.
	64	.Pp
	65	.Nm
	66	Implements a simple bridge for all entities connected to it. A cache
	67	of MAC addresses is built up (just like an etherswitch does) and matching
	68	packets will be forwarded directly to the proper 'port' (connected clients
	69	or TAP interface). Unknown MACs will be broadcast.
	70	.Pp
	71	The following options are available:
	72	.Bl -tag -width flag
	73	.It Fl c
	74	Connect into the bridge and monitor activity. This option currently only
	75	monitors broadcast packets. Packets with cached MACs are not monitored.
	76	.It Fl d
	77	Debug mode. Do not go into the background.
	78	.It Fl U
	79	Unsecure mode. Act as a pure bridge and do not try to secure the IP
	80	space from host visibility. This is typically used with the
	81	.Fl b
	82	option to directly bridge
	83	.Nm
	84	into the host rather then operating it as a separate subnet.
	85	.It Fl b Ar bridgeN
	86	The
	87	.Xr tap 4
	88	interface
	89	will be bridged into the specified bridge.
	90	.It Fl p Ar socket_path
	91	Specify where to create the unix domain socket in the filesystem space.
	92	By default the socket is called
	93	.Pa /dev/vknet .
	94	.It Fl t Ar tapN
	95	Specify a particular
	96	.Xr tap 4
	97	interface to use. If not specified,
	98	.Nm
	99	will search for an unused tap interface.
	100	.It Ar address/cidrbits
	101	When operating in secure mode (which is the default), a CIDR block must be
	102	specified. The address is the address you wish to assign to the TAP
	103	interface and will sit on both the host and virtual networks if not bridged.
	104	The
	105	.Ar cidrbits
	106	is the number of bits representing the virtual subnet. For example,
	107	10.1.0.1/24 places the tap interface on 10.1.0.1 and gives you an 8 bit
	108	subnet capable of handling 254 hosts.
	109	.El
	110	.Sh EXAMPLES
	111	.Li "vknetd 10.1.0.1/16"
	112	.Pp
	113	.Sh REQUIREMENTS
	114	.Nm
	115	requires that the
	116	.Ar if_tap
	117	and
	118	.Ar if_bridge
	119	modules be loaded.
	120	In addition, a 'vknet' group must exist in /etc/groups.
	121	.Sh FILES
	122	.Bl -tag -width /var/log/lastlog -compact
	123	.It Pa /dev/tap*
	124	TAP interface used to route packets from userland providers back into the
	125	real machine. If not otherwise specified an unused tap interface will be
	126	selected.
	127	.It Pa /dev/vknet
	128	Default socket
	129	.Nm
	130	sits on waiting for connections.
	131	.El
	132	.Sh BUGS
	133	.Nm
	134	defaults to secure mode and will prevent IP spoofing, but the security
	135	does not yet handle ARP issues so ARP spoofing can be used to create a
	136	denial of service attack on the host network.
	137	.Pp
	138	.Nm
	139	does not currently implement a timeout for its MAC cache.
	140	.Sh SEE ALSO
	141	.Xr vkernel 7 ,
	142	.Xr vke 7
	143	.Sh HISTORY
	144	The
	145	.Nm
	146	command was written by Matthew Dillon and first appeared in
	147	.Dx 1.13
	148	in May 2008.