mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-27 11:55:06 +00:00
233 lines
6.0 KiB
Groff
233 lines
6.0 KiB
Groff
.\" Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
|
|
.\" 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.
|
|
.\" 3. Neither the name of the project nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE PROJECT 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 PROJECT 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
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $Id: gif.4,v 1.2 1999/09/29 15:36:17 itojun Exp $
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd April 10, 1999
|
|
.Dt GIF 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm gif
|
|
.Nd
|
|
.Tn Generic tunnel interface
|
|
.Sh SYNOPSIS
|
|
.Cd "pseudo-device gif 4"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
interface is a generic tunnelling pseudo device for IPv4 and IPv6.
|
|
It can tunnel IPv[46] traffic over IPv[46].
|
|
Therefore, there can be four possible configurations.
|
|
The behavior of
|
|
.Nm
|
|
is mainly based on RFC1933 IPv6-over-IPv4 configured tunnel.
|
|
.Pp
|
|
To use
|
|
.Nm gif ,
|
|
administrator needs to configure protocol and addresses used for the outer
|
|
header.
|
|
This can be done by using
|
|
.Xr gifconfig 8 ,
|
|
or
|
|
.Dv SIOCSIFPHYADDR
|
|
ioctl.
|
|
Also, administrator needs to configure protocol and addresses used for the
|
|
inner header, by using
|
|
.Xr ifconfig 8 .
|
|
Note that IPv6 link-local address
|
|
.Pq those start with Li fe80::
|
|
will be automatically configured whenever possible.
|
|
You may need to remove IPv6 link-local address manually using
|
|
.Xr ifconfig 8 ,
|
|
when you would like to disable the use of IPv6 as inner header
|
|
.Pq like when you need pure IPv4-over-IPv6 tunnel .
|
|
Finally, use routing table to route the packets toward
|
|
.Nm
|
|
interface.
|
|
.Pp
|
|
.Nm
|
|
interface can be configued to perform bidirectional tunnel, or
|
|
multi-destination tunnel.
|
|
This is controlled by
|
|
.Dv IFF_LINK0
|
|
interface flag.
|
|
Also,
|
|
.Nm
|
|
can be configured to be ECN friendly.
|
|
This can be configured by
|
|
.Dv IFF_LINK1 .
|
|
.\"
|
|
.Ss Bidirectional and multi-destination mode
|
|
Usually,
|
|
.Nm
|
|
implements bidirectional tunnel.
|
|
.Xr gifconfig 8
|
|
should configure a tunnel ingress point
|
|
.Pq this node
|
|
and an egress point
|
|
.Pq tunnel endpoint ,
|
|
and
|
|
one
|
|
.Nm
|
|
interface will tunnel to only a single tunnel endpoint,
|
|
and accept from only a single tunnel endpoint.
|
|
Source and destination address for outer IP header is always the
|
|
ingress and the egress point configued by
|
|
.Xr gifconfig 8 .
|
|
.Pp
|
|
With
|
|
.Dv IFF_LINK0
|
|
interface flag,
|
|
.Nm
|
|
can be configured to implement multi-destination tunnel.
|
|
With
|
|
.Dv IFF_LINK0 ,
|
|
it is able to configure egress point to IPv4 wildcard address
|
|
.Pq Nm 0.0.0.0
|
|
or IPv6 unspecified address
|
|
.Pq Nm 0::0 .
|
|
In this case, destination address for the outer IP header is
|
|
determined based on the routing table setup.
|
|
Therefore, one
|
|
.Nm
|
|
interface can tunnel to multiple destinations.
|
|
Also,
|
|
.Nm
|
|
will accept tunneled traffic from any outer source address.
|
|
.Pp
|
|
When finding a
|
|
.Nm gif
|
|
interface from the inbound tunneled traffic,
|
|
bidirectional mode interface is preferred than multi-destination mode interface.
|
|
For example, if you have the following three
|
|
.Nm
|
|
interfaces on node A, tunneled traffic from C to A will match the second
|
|
.Nm
|
|
interface, not the third one.
|
|
.Bl -bullet -compact -offset indent
|
|
.It
|
|
bidirectional, A to B
|
|
.It
|
|
bidirectional, A to C
|
|
.It
|
|
multi-destination, A to any
|
|
.El
|
|
.Pp
|
|
Please note that multi-destination mode is far less secure
|
|
than bidirectional mode.
|
|
Multi-destination mode
|
|
.Nm
|
|
can accept tunneled packet from anybody,
|
|
and can be attacked from a malicious node.
|
|
.Pp
|
|
.Ss ECN friendly behavior
|
|
.Nm
|
|
can be configured to be ECN friendly, as described in
|
|
.Dv draft-ipsec-ecn-00.txt .
|
|
This is turned off by default, and can be turned on by
|
|
.Dv IFF_LINK1
|
|
interface flag.
|
|
.Pp
|
|
Without
|
|
.Dv IFF_LINK1 ,
|
|
.Nm
|
|
will show a normal behavior, like described in RFC1933.
|
|
This can be summarized as follows:
|
|
.Bl -tag -width "Ingress" -offset indent
|
|
.It Ingress
|
|
Set outer TOS bit to
|
|
.Dv 0 .
|
|
.It Egress
|
|
Drop outer TOS bit.
|
|
.El
|
|
.Pp
|
|
With
|
|
.Dv IFF_LINK1 ,
|
|
.Nm
|
|
will copy ECN bits
|
|
.Po
|
|
.Dv 0x02
|
|
and
|
|
.Dv 0x01
|
|
on IPv4 TOS byte or IPv6 traffic class byte
|
|
.Pc
|
|
on egress and ingress, as follows:
|
|
.Bl -tag -width "Ingress" -offset indent
|
|
.It Ingress
|
|
Copy TOS bits except for ECN CE
|
|
.Po
|
|
masked with
|
|
.Dv 0xfe
|
|
.Pc
|
|
from
|
|
inner to outer.
|
|
set ECN CE bit to
|
|
.Dv 0 .
|
|
.It Egress
|
|
Use inner TOS bits with some change.
|
|
If outer ECN CE bit is
|
|
.Dv 1 ,
|
|
enable ECN CE bit on the inner.
|
|
.El
|
|
.Pp
|
|
Note that the ECN friendly behavior violates RFC1933.
|
|
This should be used in mutual agreement with the tunnel endpoint.
|
|
.Pp
|
|
.Ss Backward compatibility
|
|
.Nm
|
|
interface will capture packets toward IPv4-in-IPv4 tunnel,
|
|
which has been used by
|
|
.Xr vif 4
|
|
multicast tunnel device
|
|
.Pq used in MBone community .
|
|
For compatibility, IPv4-in-IPv4 traffic will be matched to
|
|
.Nm
|
|
interfaces first, and then sent to
|
|
.Xr vif 4
|
|
if no match is found.
|
|
.\"
|
|
.Sh SEE ALSO
|
|
.Xr inet 4 ,
|
|
.Xr inet6 4 ,
|
|
.Xr vif 4 ,
|
|
.Xr gifconfig 8 ,
|
|
RFC1933
|
|
.Rs
|
|
.%A Sally Floyd
|
|
.%A David L. Black
|
|
.%A K. K. Ramakrishnan
|
|
.%T "IPsec Interactions with ECN"
|
|
.%D February 1999
|
|
.%O http://www.aciri.org/floyd/papers/draft-ipsec-ecn-00.txt
|
|
.Re
|
|
.\"
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
device first appeared in WIDE hydrangea IPv6 kit.
|