NAME
etherip —
EtherIP tunneling device
SYNOPSIS
pseudo-device etherip
DESCRIPTION
Theetherip interface is a tunneling pseudo device for
Ethernet frames. It can tunnel Ethernet traffic over IPv4 and IPv6 using the
EtherIP protocol specified in RFC 3378.
The only difference between an etherip
interface and a real Ethernet interface is that there is an IP tunnel
instead of a wire. Therefore, to use etherip the
administrator must first create the interface and then configure protocol
and addresses used for the outer header. This can be done by using
ifconfig(8) create and
tunnel subcommands, or
SIOCIFCREATE and
SIOCSLIFPHYADDR ioctls.
Packet format
Ethernet frames are prepended with a EtherIP header as described by RFC 3378. The resulting EtherIP packets will be encapsulated in an outer packet, which may be either an IPv4 or IPv6 packet, with IP protocol number 97.
Ethernet address
When a etherip device is created, it is
assigned an Ethernet address of the form f2:0b:a5:xx:xx:xx. This address can
later be changed through a sysctl node.
The sysctl node is net.link.etherip.<iface>. Any string of six colon-separated hexadecimal numbers will be accepted. Reading that node will provide a string representation of the current Ethernet address.
Security
The EtherIP header of incoming packets is not checked for validity. This is because there seems to be some confusion about how such a header has to look like. For outgoing packets, the header is set up the same way as done in OpenBSD, FreeBSD, and Linux to be compatible with those systems.
Converting from previous implementation
A tunnel configured for the previous (undocumented) implementation
will work with just renaming the device from gif to
etherip.
SEE ALSO
HISTORY
The etherip device first appeared in
NetBSD 4.0, it is based on
tap(4), gif(4), and the former gif-based EtherIP implementation
ported from OpenBSD.
BUGS
Probably many. There is lots of code duplication between
etherip,
tap(4), gif(4), and probably other tunnelling drivers which should be
cleaned up.