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Python C extension to query the Kernel ARP cache for the MAC address of a given IP address.
The arpreq
module exposes two functions arpreq
and arpreqb
, that
try to resolve a given IPv4 address into a MAC address by querying the ARP
cache of the Kernel.
An IP address can only be resolved to a MAC address if it is on the same subnet as your machine.
Please note, that no ARP request packet is sent out by this module, only the cache is queried. If the IP address hasn't been communicated with recently, there may not be cache entry for it. You can refresh the cache, by trying to communicate with IP (e.g. by sending and ICMP Echo-Request aka ping) before probing the ARP cache.
Let's assume your current machine has the address 192.0.2.10
and
another machine with the address 192.0.2.1
is on the same subnet:
.. code:: python
>>> import arpreq
>>> arpreq.arpreq('192.0.2.1')
'00:11:22:33:44:55'
If an IP address can not be resolved to an MAC address, None is returned.
.. code:: python
>>> arpreq.arpreq('8.8.8.8') is None
True
IP addresses may be also be specified as int or rich IP address data type
of the common ipaddr
, ipaddress
, or netaddr
modules.
.. code:: python
>>> arpreq.arpreq(0x7F000001)
'00:00:00:00:00:00'
>>> import netaddr
>>> arpreq.arpreq(netaddr.IPAddress('127.0.0.1'))
'00:00:00:00:00:00'
>>> import ipaddr # on Python 2
>>> arpreq.arpreq(ipaddr.IPv4Address('127.0.0.1'))
'00:00:00:00:00:00'
>>> import ipaddress
>>> arpreq.arpreq(ipaddress.IPv4Address(u'127.0.0.1'))
'00:00:00:00:00:00'
Instead of a hexadecimal string representation, MAC addresses may also be
returned as native bytes when using the arpreqb
function:
.. code:: python
>>> arpreq.arpreqb('127.0.0.1')
b'\x00\x00\x00\x00\x00\x00'
>>> arpreq.arpreqb('192.0.2.1')
b'\x00\x11"3DU'
This extension has only been tested on Linux, it should however work on
any platform that supports the SIOCGARP
ioctl, which is virtually
every BSD and Linux. MacOS X does not work anymore, because Apple has
removed the interface.
The SIOCGARP
ioctl interface described in arp(7)
and used by this
module is a fairly old mechanism and as the name suggests, works only for ARP
and therefore only for IPv4. For IPv6 the Linux Kernel uses the modern and
extensible rtnetlink(7)
interface based on netlink(7)
_ to manage
link-layer neighbor information.
Until Linux 5.0 however only whole tables could be dumped via rtnetlink(7)
_
RTM_GETNEIGH
messages and it was not possible to query for specific IP
addresses. If entries need to be queried often or there are a lot of entries,
this might be too inefficient. As an optimization querying the tables only
once and subscribing to change events afterwards was possible, albeit more
complicated. Since
Linux 5.0 <https://github.com/torvalds/linux/commit/24894bc6eabc43f55f5470767780ac07db18e797>
_
RTM_GETNEIGH
messages can be used to query specific addresses on specific
interfaces.
The pure-python netlink implementation pyroute2
can be used to access the
rtnetlink(7)
and other netlink(7)
interfaces.
Since version 0.5.14 <https://github.com/svinota/pyroute2/commit/b1f2af00689e17a50eb09b1560acfd0dc96b1a7a>
specific addresses can be queried.
.. _arp(7): https://manpages.debian.org/stable/manpages/arp.7.en.html .. _netlink(7): https://manpages.debian.org/stable/manpages/netlink.7.en.html .. _rtnetlink(7): https://manpages.debian.org/stable/manpages/rtnetlink.7.en.html .. _pyroute2: https://pyroute2.org/
v0.3.4 (2021-12-21) ^^^^^^^^^^^^^^^^^^^
arpreqb
function, which returns the MAC as Python bytes
objectv0.3.3 (2017-05-03) ^^^^^^^^^^^^^^^^^^^
v0.3.2 (2017-05-03) ^^^^^^^^^^^^^^^^^^^
v0.3.1 (2016-07-06) ^^^^^^^^^^^^^^^^^^^
v0.3.0 (2016-06-26) ^^^^^^^^^^^^^^^^^^^
v0.2.1 (2016-06-26) ^^^^^^^^^^^^^^^^^^^
v0.2.0 (2016-06-09) ^^^^^^^^^^^^^^^^^^^
v0.1.0 (2015-11-28) ^^^^^^^^^^^^^^^^^^^