netifaces-merged 0.9.0

1. What is this?

It’s been annoying me for some time that there’s no easy way to get the address(es) of the machine’s network interfaces from Python. There is a good reason for this difficulty, which is that it is virtually impossible to do so in a portable manner. However, it seems to me that there should be a package you can easy_install that will take care of working out the details of doing so on the machine you’re using, then you can get on with writing Python code without concerning yourself with the nitty gritty of system-dependent low-level networking APIs.

This package attempts to solve that problem.

2. How do I use it?

First you need to install it, which you can do by typing

tar xvzf netifaces-0.4.tar.gz cd netifaces-0.4 python setup.py install

Once that’s done, you’ll need to start Python and do something like the following:

>>> import netifaces

Then if you enter

>>> netifaces.interfaces()
['lo0', 'gif0', 'stf0', 'en0', 'en1', 'fw0']

you’ll see the list of interface identifiers for your machine.

You can ask for the addresses of a particular interface by doing

>>> netifaces.ifaddresses('lo0')
{18: [{'addr': ''}], 2: [{'peer': '127.0.0.1', 'netmask': '255.0.0.0', 'addr': '127.0.0.1'}], 30: [{'peer': '::1', 'netmask': 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff', 'addr': '::1'}, {'peer': '', 'netmask': 'ffff:ffff:ffff:ffff::', 'addr': 'fe80::1%lo0'}]}

Hmmmm. That result looks a bit cryptic; let’s break it apart and explain what each piece means. It returned a dictionary, so let’s look there first:

{ 18: […], 2: […], 30: […] }

Each of the numbers refers to a particular address family. In this case, we have three address families listed; on my system, 18 is AF_LINK (which means the link layer interface, e.g. Ethernet), 2 is AF_INET (normal Internet addresses), and 30 is AF_INET6 (IPv6).

But wait! Don’t use these numbers in your code. The numeric values here are system dependent; fortunately, I thought of that when writing netifaces, so the module declares a range of values that you might need. e.g.

>>> netifaces.AF_LINK
18

Again, on your system, the number may be different.

So, what we’ve established is that the dictionary that’s returned has one entry for each address family for which this interface has an address. Let’s take a look at the AF_INET addresses now:

>>> addrs = netifaces.ifaddresses('lo0')
>>> addrs[netifaces.AF_INET]
[{'peer': '127.0.0.1', 'netmask': '255.0.0.0', 'addr': '127.0.0.1'}]

You might be wondering why this value is a list. The reason is that it’s possible for an interface to have more than one address, even within the same family. I’ll say that again: you can have more than one address of the same type associated with each interface.

Asking for “the” address of a particular interface doesn’t make sense.

Right, so, we can see that this particular interface only has one address, and, because it’s a loopback interface, it’s point-to-point and therefore has a peer address rather than a broadcast address.

Let’s look at a more interesting interface.

>>> addrs = netifaces.ifaddresses('en0')
>>> addrs[netifaces.AF_INET]
[{'broadcast': '10.15.255.255', 'netmask': '255.240.0.0', 'addr': '10.0.1.4'}, {'broadcast': '192.168.0.255', 'addr': '192.168.0.47'}]

This interface has two addresses (see, I told you…) Both of them are regular IPv4 addresses, although in one case the netmask has been changed from its default. The netmask may not appear on your system if it’s set to the default for the address range.

Because this interface isn’t point-to-point, it also has broadcast addresses.

Now, say we want, instead of the IP addresses, to get the MAC address; that is, the hardware address of the Ethernet adapter running this interface. We can do

>>> addrs[netifaces.AF_LINK]
[{'addr': '00:12:34:56:78:9a'}]

Note that this may not be available on platforms without getifaddrs(), unless they happen to implement SIOCGIFHWADDR. Note also that you just get the address; it’s unlikely that you’ll see anything else with an AF_LINK address. Oh, and don’t assume that all AF_LINK addresses are Ethernet; you might, for instance, be on a Mac, in which case:

>>> addrs = netifaces.ifaddresses('fw0')
>>> addrs[netifaces.AF_LINK]
[{'addr': '00:12:34:56:78:9a:bc:de'}]

No, that isn’t an exceptionally long Ethernet MAC address—it’s a FireWire address.

3. This is great! What platforms does it work on?

Well, see, here’s the thing. It’s been tested on Mac OS X, and it seems to work. (OS X helpfully has some of the SIOCGIFxxx ioctl()s, which means that most of those have been tested too, the only glaring exception being the SIOCGIFHWADDR ioctl(), which OS X just doesn’t have.)

It should probably work on most of the other UNIX-like systems with relatively minor changes. If you do have to change something, send it to me at <alastair AT alastairs-place.net> and I’ll see if I can merge it in.

It also works just fine on Windows, using the GetAdaptersInfo() function. Note, though, that on Windows it isn’t possible (yet) to retrieve IPv6 addresses. I don’t use Windows at the moment, so this isn’t a priority for me. If you know how to fix it, drop me a line and I’ll consider adding any necessary code.

4. What license is this under?

It’s an MIT-style license. Here goes:

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.