Python: check whether a network interface is up

Question

In Python, is there a way to detect whether a given network interface is up?

In my script, the user specifies a network interface, but I would like to make sure that the interface is up and has been assigned an IP address, before doing anything else.

I'm on Linux and I am root.

What OS? Does this script need to run on different OS's, or is it just one in particular? — Gabriel Samfira, Jul 16 '13 at 14:54
Ops. Linux. ;) In the future I will extend this to OS X and Windows, but for now Linux will be enough — Ricky Robinson, Jul 16 '13 at 14:56
No worries :). http://stackoverflow.com/questions/11735821/python-get-localhost-ip/11736402 <-- have you seen this? The accepted answer works on linux. The netifaces module is portable and will work on the tested os's. — Gabriel Samfira, Jul 16 '13 at 14:58
Wow, that library is awesome! It solved all my problems. Thanks!! — Ricky Robinson, Jul 16 '13 at 15:26
I AM ON LINUX and I AM ROOT sounds like this is my house ,i ll burn it if i have too!!! — Eliethesaiyan, Jan 13 '16 at 11:23

score 14 · Answer 1 · answered Oct 25 '17 at 12:44

The interface can be configured with an IP address and not be up so the accepted answer is wrong. You actually need to check /sys/class/net/<interface>/flags. If the content is in the variable flags, flags & 0x1 is whether the interface is up or not.

Depending on the application, the /sys/class/net/<interface>/operstate might be what you really want, but technically the interface could be up and the operstate down, e.g. when no cable is connected.

All of this is Linux-specific of course.

A warning: in Linux Mint 18.2, the Cinnamon Network Manager applet control to turn off a network adapter leaves it both UP and operational. It removes the IP address, though. — Harvey, Feb 21 '18 at 18:29

Ricky Robinson · Accepted Answer · 2015-10-21T14:04:42.450

10

As suggested by @Gabriel Samfira, I used netifaces. The following function returns True when an IP address is associated to a given interface.

def is_interface_up(interface):
    addr = netifaces.ifaddresses(interface)
    return netifaces.AF_INET in addr

The documentation is here

edited Oct 21 '15 at 14:04

answered Jul 16 '13 at 15:28

Ricky Robinson

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1

A useful check before calling the above function is: `if anInterface in netifaces.interfaces() #...` – Ricky Robinson Jul 16 '13 at 19:52
2

Unfortunately, this does work only half for IPv6/AF_INET6: while an interface becomming RUNNING gets its LLA, when the same interface goes offline, the LLA still lives on. – TheDiveO Jul 25 '17 at 15:36

ofirule · Answer 3 · 2018-11-04T15:09:30.490

7

Answer using psutil:

import psutil
import socket

def check_interface(interface):
    interface_addrs = psutil.net_if_addrs().get(interface) or []
    return socket.AF_INET in [snicaddr.family for snicaddr in interface_addrs]

edited Nov 04 '18 at 15:09

answered Nov 04 '18 at 15:03

ofirule

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score 3 · Answer 4 · answered Feb 17 '15 at 16:24

With pyroute2.IPRoute:

from pyroute2 import IPRoute
ip = IPRoute()
state = ip.get_links(ip.link_lookup(ifname='em1'))[0].get_attr('IFLA_OPERSTATE')
ip.close()

With pyroute2.IPDB:

from pyroute2 import IPDB
ip = IPDB()
state = ip.interfaces.em1.operstate
ip.release()

score 2 · Answer 5 · answered Sep 21 '17 at 16:42

2

You can see the content of the file in /sys/class/net/<interface>/operstate. If the content is not down then the interface is up.

answered Sep 21 '17 at 16:42

André Pires

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score 0 · Answer 6 · answered Mar 13 '19 at 13:21

0

If the question is about checking if the cable is conencted (FreeBSD);

[status for status in run.cmd(' /usr/local/bin/sudo ifconfig %s ' % interface).split("\t") if status.strip().startswith("status")][0].strip().endswith("active")

For this, no api support so far :( ...

answered Mar 13 '19 at 13:21

myuce

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That's a bit of an overkill if we can simply read `/sys/class/net//operstate`... – Ricky Robinson Mar 13 '19 at 16:00
on FreeBSD 11 `cat: /sys/class/net/em0/operstate: No such file or directory` – myuce Mar 14 '19 at 08:26
I see. Is there an equivalent to `/sys/class/net`? – Ricky Robinson Mar 14 '19 at 16:31
I could not see. I would love to know the equivalent in FreeBSD. – myuce Mar 15 '19 at 05:52

Python: check whether a network interface is up

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