ipe —
Internet
Encapsulation Protocol network device
pseudo-device ipe
The
ipe driver provides IP tunnel construction
using A Scheme for an Internet Encapsulation Protocol: Version 1 (RFC 1241).
ipe datagrams (IP protocol number 98 as per RFC
1700) are encapsulated into IP using a small encapsulation header. Different
tunnels between the same endpoints are distinguished by a Flow Identifier in
the header. This protocol according to the RFC only supports encapsulating
IPv4 in IPv4, but the driver also supports IPv6.
A
ipe interface can be created at runtime using the
ifconfig
ipeN
create command or by setting up a
hostname.if(5) configuration file for
netstart(8).
The MTU is set to 1452 by default. This may not be an optimal value depending on
the link between the two tunnel endpoints, but it can be adjusted via
ifconfig(8).
For correct operation, the route to the tunnel destination must not go over the
interface itself. This can be implemented by adding a distinct or a more
specific route to the tunnel destination than the hosts or networks routed via
the tunnel interface. Alternatively, the tunnel traffic may be configured in a
separate routing table to the encapsulated traffic.
ipe interfaces support the following
ioctl(2)s for configuring tunnel options:
SIOCSLIFPHYADDR
struct if_laddrreq *- Set the addresses of the outer IP header. The addresses may
only be configured while the interface is down.
SIOCGLIFPHYADDR
struct if_laddrreq *- Get the addresses of the outer IP header.
SIOCDIFPHYADDR- Clear the outer IP header addresses. The addresses may only
be cleared while the interface is down.
SIOCSVNETID
struct ifreq *- Set a 32 bit virtual network identifier used as the Flow
Identifier in the IP Encapsulation header. The virtual network identifier
may only be configured while the interface is down.
SIOCGVNETID
struct ifreq *- Get the virtual network identifer used as the Flow
Identifier in the IP Encapsulation header.
SIOCSLIFPHYRTABLE
struct ifreq *- Set the routing table the encapsulated IP packets operate
within. The routing table may only be configured while the interface is
down.
SIOCGLIFPHYRTABLE
struct ifreq *- Get the routing table the encapsulated IP packets operate
within.
SIOCSLIFPHYTTL
struct ifreq *- Set the Time-To-Live field in IPv4 encapsulation headers,
or the Hop Limit field in IPv6 encapsulation headers.
SIOCGLIFPHYTTL
struct ifreq *- Get the value used in Time-To-Live field in a IPv4
encapsulation header or the Hop Limit field in a IPv6 encapsulation
header.
Configuration example:
Host X --- Host A ----------- IP Encap ------------ Host D --- Host E
\ /
\ /
+------ Host B ------ Host C ------+
On Host A (
OpenBSD):
# route add default B
# ifconfig ipeN create
# ifconfig ipeN tunnel A D
# ifconfig ipeN A D netmask 255.255.255.255
# route add E D
On Host D (
OpenBSD):
# route add default C
# ifconfig ipeN create
# ifconfig ipeN tunnel D A
# ifconfig ipeN D A netmask 255.255.255.255
# route add D E
The Flow Identifier may be set using
ifconfig(8)
and the vnetid argument:
# ifconfig ipeN vnetid 128
The route domain used for the encapsulated traffic may be set using
ifconfig(8) and the tunneldomain argument:
# ifconfig ipeN tunneldomain 1
inet(4),
ip(4),
netintro(4),
options(4),
hostname.if(5),
protocols(5),
ifconfig(8),
netstart(8)
R. Woodburn and
D. Mills, A Scheme for an Internet
Encapsulation Protocol: Version 1, RFC 1241,
July 1991.
J. Reynolds and
J. Postel, Assigned Numbers,
RFC 1700, October
1994.
The
ipe driver first appeared in
OpenBSD 6.3.
David Gwynne
<
dlg@openbsd.org>
The
ipe driver only handles data packets within the
protocol, it does not implement support for error handling as described in the
RFC.