.\"	$OpenBSD: mobileip.4,v 1.3 2018/02/07 08:45:17 dlg Exp $
.\"
.\" Copyright (c) 2018 David Gwynne <dlg@openbsd.org>
.\"
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.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: February 7 2018 $
.Dt MOBILEIP 4
.Os
.Sh NAME
.Nm mobileip
.Nd MobileIP encapsulating network device
.Sh SYNOPSIS
.Cd "pseudo-device mobileip"
.Sh DESCRIPTION
The
.Nm
driver provides IP tunnel construction using
the Mobile IP (RFC 2004) encapsulation protocol
.Pp
.Nm
datagrams (IP protocol number 55)
are encapsulated into IP using a small encapsulation header.
This protocol, in line with the RFC, only supports encapsulating
IPv4.
.Pp
A
.Nm
interface can be created at runtime using the
.Ic ifconfig Nm Ns Ar N Ic create
command or by setting up a
.Xr hostname.if 5
configuration file for
.Xr netstart 8 .
.Pp
The MTU is set to 1488 by default.
This may not be an optimal value
depending on the link between the two tunnel endpoints,
but it can be adjusted via
.Xr ifconfig 8 .
.Pp
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.
.Pp
.Nm
interfaces support the following
.Xr ioctl 2 Ns s
for configuring tunnel options:
.Bl -tag -width indent -offset 3n
.It Dv SIOCSLIFPHYADDR Fa "struct if_laddrreq *"
Set the addresses of the outer IP header.
The addresses may only be configured while the interface is down.
.It Dv SIOCGLIFPHYADDR Fa "struct if_laddrreq *"
Get the addresses of the outer IP header.
.It Dv SIOCDIFPHYADDR
Clear the outer IP header addresses.
The addresses may only be cleared while the interface is down.
.It Dv SIOCSLIFPHYRTABLE Fa "struct ifreq *"
Set the routing table the encapsulated IP packets operate within.
The routing table may only be configured while the interface is down.
.It Dv SIOCGLIFPHYRTABLE Fa "struct ifreq *"
Get the routing table the encapsulated IP packets operate within.
.El
.Sh EXAMPLES
Configuration example:
.Bd -literal
Host X --- Host A ----------- MobileIP ------------ Host D --- Host E
              \e                                      /
               \e                                    /
                +------ Host B ------ Host C ------+
.Ed
.Pp
On Host A
.Pq Ox :
.Bd -literal -offset indent
# route add default B
# ifconfig mobileipN create
# ifconfig mobileipN tunnel A D
# ifconfig mobileipN A D netmask 255.255.255.255
# route add E D
.Ed
.Pp
On Host D
.Pq Ox :
.Bd -literal -offset indent
# route add default C
# ifconfig mobileipN create
# ifconfig mobileipN tunnel D A
# ifconfig mobileipN D A netmask 255.255.255.255
# route add D E
.Ed
.Pp
The route domain used for the encapsulated traffic may be set using
.Xr ifconfig 8
and the tunneldomain argument:
.Bd -literal -offset indent
# ifconfig mobileipN tunneldomain 1
.Ed
.Sh SEE ALSO
.Xr inet 4 ,
.Xr ip 4 ,
.Xr netintro 4 ,
.Xr options 4 ,
.Xr hostname.if 5 ,
.Xr protocols 5 ,
.Xr ifconfig 8 ,
.Xr netstart 8
.Sh STANDARDS
.Rs
.%A C. Perkins
.%D October 1996
.%R RFC 2004
.%T Minimal Encapsulation within IP
.Re
.Sh HISTORY
Support for the MobileIP protocol was originally implemented as part of the
.Xr gre 4
driver.
The
.Nm
driver was split off from
.Xr gre 4
in
.Ox 6.3 .