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[dragonfly.git] / usr.sbin / vknetd / vknetd.8

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.\" $DragonFly: src/usr.sbin/vknetd/vknetd.8,v 1.3 2008/05/31 12:04:15 swildner Exp $
.\"
.Dd May 21, 2009
.Dt vknetd 8
.Os
.Sh NAME
.Nm vknetd
.Nd create a bridged network for (typically user-run) vkernels
.Sh SYNOPSIS
.Nm
.Op Fl cdU
.Op Fl b Ar bridgeN
.Op Fl p Ar socket_path
.Op Fl t Ar tapN
.Op Ar address/cidrbits
.Sh DESCRIPTION
The
.Nm
utility creates a virtualized bridged network suitable for vkernel use.
The utility was created to simplify vkernel oprations and to allow user-run
vkernels to have access to a network.
General use is to specify a large 10-dot network which multiple vkernels are
then able to connect to, and backfeed the whole mess to a TAP interface.
.Pp
A vkernel would make use of the virtualized network by specifying
.Fl I Ar /var/run/vknet
instead of a
.Xr tap 4
interface.
Any number of vkernels may connect to the virtual network.
.Pp
.Nm
Implements a simple bridge for all entities connected to it.
A cache
of MAC addresses is built up (just like an etherswitch does) and matching
packets will be forwarded directly to the proper 'port' (connected clients
or TAP interface).
Unknown MACs will be broadcast.
.Pp
The following options are available:
.Bl -tag -width flag
.It Fl c
Connect into the bridge and monitor activity.
This option currently only monitors broadcast packets.
Packets with cached MACs are not monitored.
.It Fl d
Debug mode.
Do not go into the background.
.It Fl U
Unsecure mode.
Act as a pure bridge and do not try to secure the IP
space from host visibility.
This is typically used with the
.Fl b
option to directly bridge
.Nm
into the host rather then operating it as a separate subnet.
.It Fl b Ar bridgeN
The
.Xr tap 4
interface
will be bridged into the specified bridge.
.It Fl p Ar socket_path
Specify where to create the unix domain socket in the filesystem space.
By default the socket is called
.Pa /var/run/vknet .
.It Fl t Ar tapN
Specify a particular
.Xr tap 4
interface to use.
If not specified,
.Nm
will search for an unused tap interface.
.It Ar address/cidrbits
When operating in secure mode (which is the default), a CIDR block must be
specified.
It is optional in unsecure mode.
The address is the address you wish to assign to the TAP
interface and will sit on both the host and virtual networks if not bridged.
The
.Ar cidrbits
is the number of bits representing the virtual subnet.
For example,
10.1.0.1/24 places the tap interface on 10.1.0.1 and gives you an 8 bit
subnet capable of handling 254 hosts.
An address of 0.0.0.0 is allowed as a special case in secure mode so that
bootp
.Xr ( dhclient 8 )
can get through.
.El
.Sh FILES
.Bl -tag -width /var/log/lastlog -compact
.It Pa /dev/tap*
TAP interface used to route packets from userland providers back into the
real machine.
If not otherwise specified an unused tap interface will be selected.
.It Pa /var/run/vknet
Default socket
.Nm
sits on waiting for connections.
.El
.Sh EXAMPLES
.Li "vknetd 10.1.0.1/16"
.Sh REQUIREMENTS
.Nm
requires that the
.Ar if_tap
and
.Ar if_bridge
modules be loaded.
In addition, a 'vknet' group must exist in /etc/groups.
.Sh SEE ALSO
.Xr vknet 1 ,
.Xr vke 4 ,
.Xr vkernel 7
.Sh HISTORY
The
.Nm
command was written by Matthew Dillon and first appeared in
.Dx 1.13
in May 2008.
.Sh BUGS
.Nm
defaults to secure mode and will prevent IP spoofing, but the security
does not yet handle ARP issues so ARP spoofing can be used to create a
denial of service attack on the host network.
.Pp
.Nm
does not currently implement a timeout for its MAC cache.