networking - Python: check whether a network interface is up

8
votes

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.

6
pythonnetworkingipdhcpnetwork-interface
What OS? Does this script need to run on different OS's, or is it just one in particular? - Gabriel Samfira
Ops. Linux. ;) In the future I will extend this to OS X and Windows, but for now Linux will be enough - Ricky Robinson
No worries :). stackoverflow.com/questions/11735821/python-get-localhost-ip/… <-- 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
Wow, that library is awesome! It solved all my problems. Thanks!! - Ricky Robinson
I AM ON LINUX and I AM ROOT sounds like this is my house ,i ll burn it if i have too!!! - Eliethesaiyan

6 Answers

12
votes

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.

8
votes

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

4
votes

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]
3
votes

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()
2
votes

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.

0
votes

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 :( ...