= arper.lsp(8)
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== NAME

arper.lsp - Emulate ipv4 presence on a tap by responding to ARP and ICMP.

== SYNOPSIS

*./arper.lsp* *-t* _tap_ _conf__

== DESCRIPTION

The *arper.lsp* program implements ARP and ICMP responding on a given
_tap_ interface for a selection of ipv4 addresses as specified in the
given configuration file. This emulates the presence of one or more
ipv4 hosts, as if the _tap_ was interfacing a network.

The configuration file has lines of "ipv4 mac comment" to declare
pairs of IP and MAC addresses to emulate.

Note that the _tap_ must be configured separately.

== EXAMPLE

=== Emulating a single host

The configuration, "single", is as follows:
----
    192.168.1.2 02:00:00:00:00:02 some "random" host
----

Commandline:
----
# ./arper.lsp -t tap0 single &
# ifconfig tap0 192.168.1.1/24 up
# ping -n 192.168.1.2
# fg^C
----

=== Emulating three host on local network

The configuration, "triple", is as follows:
----
    192.168.1.2 02:00:00:00:00:02 some "random" host
    192.168.1.20 02:00:00:00:00:02 another "random" host
    192.168.1.200 02:00:00:00:00:02 and another "random" host
----

Commandline:
----
# ./arper.lsp -t tap0 single &
# ifconfig tap0 192.168.1.1/24 up
# ping -c 3 -n 192.168.1.2
# ping -c 3 -n 192.168.1.20
# ping -c 3 -n 192.168.1.22
# ping -c 3 -n 192.168.1.200
# fg^C
----

Note that +192.168.1.22+ is not emulated.

=== Emulating hosts on several network

The configuration, "triss", is as follows:
----
    192.168.1.2 02:00:00:00:00:02 some "random" host
    192.168.2.2 02:00:00:00:00:02 another "random" host
    192.168.3.2 02:00:00:00:00:02 and another "random" host
----

Commandline:
----
# ./arper.lsp -t tap0 single &
# ifconfig tap0 192.168.1.1/24 up
# ip addr add 192.168.2.1/24 dev tap0
# ip addr add 192.168.3.1/24 dev tap0
# ping -c 3 -n 192.168.1.2
# ping -c 3 -n 192.168.2.2
# ping -c 3 -n 192.168.3.2
# fg^C
----

=== NOTES

The *arper.lsp* script is prepared for handling ipv6 packets, but it
does not include any Neighbor Discovery activity.

== AUTHOR

Copyright 2021 Ralph Ronnquist <ralph.ronnquist@gmail.com>