285 lines
8.4 KiB
Groff
285 lines
8.4 KiB
Groff
.\" $KAME: stf.4,v 1.35 2001/05/02 06:24:49 itojun Exp $
|
|
.\"
|
|
.\" 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.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 28, 2012
|
|
.Dt STF 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm stf
|
|
.Nd
|
|
.Tn 6to4
|
|
tunnel interface
|
|
.Sh SYNOPSIS
|
|
.Cd "device stf"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
interface supports
|
|
.Dq 6to4
|
|
IPv6 in IPv4 encapsulation.
|
|
It can tunnel IPv6 traffic over IPv4, as specified in
|
|
.Li RFC3056 .
|
|
.Pp
|
|
For ordinary nodes in 6to4 site, you do not need
|
|
.Nm
|
|
interface.
|
|
The
|
|
.Nm
|
|
interface is necessary for site border router
|
|
(called
|
|
.Dq 6to4 router
|
|
in the specification).
|
|
.Pp
|
|
Each
|
|
.Nm
|
|
interface is created at runtime using interface cloning.
|
|
This is
|
|
most easily done with the
|
|
.Xr ifconfig 8
|
|
.Cm create
|
|
command or using the
|
|
.Va cloned_interfaces
|
|
variable in
|
|
.Xr rc.conf 5 .
|
|
.Pp
|
|
Due to the way 6to4 protocol is specified,
|
|
.Nm
|
|
interface requires certain configuration to work properly.
|
|
Single
|
|
(no more than 1)
|
|
valid 6to4 address needs to be configured to the interface.
|
|
.Dq A valid 6to4 address
|
|
is an address which has the following properties.
|
|
If any of the following properties are not satisfied,
|
|
.Nm
|
|
raises runtime error on packet transmission.
|
|
Read the specification for more details.
|
|
.Bl -bullet
|
|
.It
|
|
matches
|
|
.Li 2002:xxyy:zzuu::/48
|
|
where
|
|
.Li xxyy:zzuu
|
|
is a hexadecimal notation of an IPv4 address for the node.
|
|
IPv4 address can be taken from any of interfaces your node has.
|
|
Since the specification forbids the use of IPv4 private address,
|
|
the address needs to be a global IPv4 address.
|
|
.It
|
|
Subnet identifier portion
|
|
(48th to 63rd bit)
|
|
and interface identifier portion
|
|
(lower 64 bits)
|
|
are properly filled to avoid address collisions.
|
|
.El
|
|
.Pp
|
|
If you would like the node to behave as a relay router,
|
|
the prefix length for the IPv6 interface address needs to be 16 so that
|
|
the node would consider any 6to4 destination as
|
|
.Dq on-link .
|
|
If you would like to restrict 6to4 peers to be inside certain IPv4 prefix,
|
|
you may want to configure IPv6 prefix length as
|
|
.Dq 16 + IPv4 prefix length .
|
|
.Nm
|
|
interface will check the IPv4 source address on packets,
|
|
if the IPv6 prefix length is larger than 16.
|
|
.Pp
|
|
.Nm
|
|
can be configured to be ECN friendly.
|
|
This can be configured by
|
|
.Dv IFF_LINK1 .
|
|
See
|
|
.Xr gif 4
|
|
for details.
|
|
.Pp
|
|
Please note that 6to4 specification is written as
|
|
.Dq accept tunnelled packet from everyone
|
|
tunnelling device.
|
|
By enabling
|
|
.Nm
|
|
device, you are making it much easier for malicious parties to inject
|
|
fabricated IPv6 packet to your node.
|
|
Also, malicious party can inject an IPv6 packet with fabricated source address
|
|
to make your node generate improper tunnelled packet.
|
|
Administrators must take caution when enabling the interface.
|
|
To prevent possible attacks,
|
|
.Nm
|
|
interface filters out the following packets.
|
|
Note that the checks are no way complete:
|
|
.Bl -bullet
|
|
.It
|
|
Packets with IPv4 unspecified address as outer IPv4 source/destination
|
|
.Pq Li 0.0.0.0/8
|
|
.It
|
|
Packets with loopback address as outer IPv4 source/destination
|
|
.Pq Li 127.0.0.0/8
|
|
.It
|
|
Packets with IPv4 multicast address as outer IPv4 source/destination
|
|
.Pq Li 224.0.0.0/4
|
|
.It
|
|
Packets with limited broadcast address as outer IPv4 source/destination
|
|
.Pq Li 255.0.0.0/8
|
|
.It
|
|
Packets with private address as outer IPv4 source/destination
|
|
.Pq Li 10.0.0.0/8 , 172.16.0.0/12 , 192.168.0.0/16
|
|
.It
|
|
Packets with subnet broadcast address as outer IPv4 source/destination.
|
|
The check is made against subnet broadcast addresses for
|
|
all of the directly connected subnets.
|
|
.It
|
|
Packets that does not pass ingress filtering.
|
|
Outer IPv4 source address must meet the IPv4 topology on the routing table.
|
|
Ingress filter can be turned off by
|
|
.Dv IFF_LINK2
|
|
bit.
|
|
.It
|
|
The same set of rules are applied against the IPv4 address embedded into
|
|
inner IPv6 address, if the IPv6 address matches 6to4 prefix.
|
|
.El
|
|
.Pp
|
|
It is recommended to filter/audit
|
|
incoming IPv4 packet with IP protocol number 41, as necessary.
|
|
It is also recommended to filter/audit encapsulated IPv6 packets as well.
|
|
You may also want to run normal ingress filter against inner IPv6 address
|
|
to avoid spoofing.
|
|
.Pp
|
|
By setting the
|
|
.Dv IFF_LINK0
|
|
flag on the
|
|
.Nm
|
|
interface, it is possible to disable the input path,
|
|
making the direct attacks from the outside impossible.
|
|
Note, however, there are other security risks exist.
|
|
If you wish to use the configuration,
|
|
you must not advertise your 6to4 address to others.
|
|
.\"
|
|
.Sh SYSCTL VARIABLES
|
|
The following
|
|
.Xr sysctl 8
|
|
variables can be used to control the behavior of the
|
|
.Nm stf .
|
|
The default value is shown next to each variable.
|
|
.Bl -tag -width indent
|
|
.It Va net.link.stf.permit_rfc1918 : No 0
|
|
The RFC3056 requires the use of globally unique 32-bit IPv4
|
|
addresses.
|
|
This sysctl variable controls the behaviour of this requirement.
|
|
When it set to not 0,
|
|
.Nm stf
|
|
allows the use of private IPv4 addresses described in the RFC1918.
|
|
This may be useful for an Intranet environment or when some mechanisms
|
|
of network address translation (NAT) are used.
|
|
.El
|
|
.Sh EXAMPLES
|
|
Note that
|
|
.Li 8504:0506
|
|
is equal to
|
|
.Li 133.4.5.6 ,
|
|
written in hexadecimals.
|
|
.Bd -literal
|
|
# ifconfig ne0 inet 133.4.5.6 netmask 0xffffff00
|
|
# ifconfig stf0 inet6 2002:8504:0506:0000:a00:5aff:fe38:6f86 \\
|
|
prefixlen 16 alias
|
|
.Ed
|
|
.Pp
|
|
The following configuration accepts packets from IPv4 source
|
|
.Li 9.1.0.0/16
|
|
only.
|
|
It emits 6to4 packet only for IPv6 destination 2002:0901::/32
|
|
(IPv4 destination will match
|
|
.Li 9.1.0.0/16 ) .
|
|
.Bd -literal
|
|
# ifconfig ne0 inet 9.1.2.3 netmask 0xffff0000
|
|
# ifconfig stf0 inet6 2002:0901:0203:0000:a00:5aff:fe38:6f86 \\
|
|
prefixlen 32 alias
|
|
.Ed
|
|
.Pp
|
|
The following configuration uses the
|
|
.Nm
|
|
interface as an output-only device.
|
|
You need to have alternative IPv6 connectivity
|
|
(other than 6to4)
|
|
to use this configuration.
|
|
For outbound traffic, you can reach other 6to4 networks efficiently via
|
|
.Nm stf .
|
|
For inbound traffic, you will not receive any 6to4-tunneled packets
|
|
(less security drawbacks).
|
|
Be careful not to advertise your 6to4 prefix to others
|
|
.Pq Li 2002:8504:0506::/48 ,
|
|
and not to use your 6to4 prefix as a source.
|
|
.Bd -literal
|
|
# ifconfig ne0 inet 133.4.5.6 netmask 0xffffff00
|
|
# ifconfig stf0 inet6 2002:8504:0506:0000:a00:5aff:fe38:6f86 \\
|
|
prefixlen 16 alias deprecated link0
|
|
# route add -inet6 2002:: -prefixlen 16 ::1
|
|
# route change -inet6 2002:: -prefixlen 16 ::1 -ifp stf0
|
|
.Ed
|
|
.\"
|
|
.Sh SEE ALSO
|
|
.Xr gif 4 ,
|
|
.Xr inet 4 ,
|
|
.Xr inet6 4
|
|
.Pp
|
|
.Pa http://www.ipv6day.org/action.php?n=En.IPv6day
|
|
.Rs
|
|
.%A Brian Carpenter
|
|
.%A Keith Moore
|
|
.%T "Connection of IPv6 Domains via IPv4 Clouds"
|
|
.%D February 2001
|
|
.%R RFC
|
|
.%N 3056
|
|
.Re
|
|
.Rs
|
|
.%A Jun-ichiro itojun Hagino
|
|
.%T "Possible abuse against IPv6 transition technologies"
|
|
.%D July 2000
|
|
.%N draft-itojun-ipv6-transition-abuse-01.txt
|
|
.%O work in progress
|
|
.Re
|
|
.\"
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
device first appeared in WIDE/KAME IPv6 stack.
|
|
.\"
|
|
.Sh BUGS
|
|
No more than one
|
|
.Nm
|
|
interface is allowed for a node,
|
|
and no more than one IPv6 interface address is allowed for an
|
|
.Nm
|
|
interface.
|
|
It is to avoid source address selection conflicts
|
|
between IPv6 layer and IPv4 layer,
|
|
and to cope with ingress filtering rule on the other side.
|
|
This is a feature to make
|
|
.Nm
|
|
work right for all occasions.
|