196 lines
8.2 KiB
ReStructuredText
196 lines
8.2 KiB
ReStructuredText
netifaces 0.10.4
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================
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.. image:: https://drone.io/bitbucket.org/al45tair/netifaces/status.png
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:target: https://drone.io/bitbucket.org/al45tair/netifaces/latest
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:alt: Build Status
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1. What is this?
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----------------
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It's been annoying me for some time that there's no easy way to get the
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address(es) of the machine's network interfaces from Python. There is
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a good reason for this difficulty, which is that it is virtually impossible
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to do so in a portable manner. However, it seems to me that there should
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be a package you can easy_install that will take care of working out the
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details of doing so on the machine you're using, then you can get on with
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writing Python code without concerning yourself with the nitty gritty of
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system-dependent low-level networking APIs.
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This package attempts to solve that problem.
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2. How do I use it?
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-------------------
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First you need to install it, which you can do by typing::
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tar xvzf netifaces-0.10.4.tar.gz
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cd netifaces-0.10.4
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python setup.py install
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Once that's done, you'll need to start Python and do something like the
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following::
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>>> import netifaces
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Then if you enter
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>>> netifaces.interfaces()
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['lo0', 'gif0', 'stf0', 'en0', 'en1', 'fw0']
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you'll see the list of interface identifiers for your machine.
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You can ask for the addresses of a particular interface by doing
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>>> netifaces.ifaddresses('lo0')
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{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'}]}
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Hmmmm. That result looks a bit cryptic; let's break it apart and explain
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what each piece means. It returned a dictionary, so let's look there first::
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{ 18: [...], 2: [...], 30: [...] }
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Each of the numbers refers to a particular address family. In this case, we
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have three address families listed; on my system, 18 is ``AF_LINK`` (which means
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the link layer interface, e.g. Ethernet), 2 is ``AF_INET`` (normal Internet
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addresses), and 30 is ``AF_INET6`` (IPv6).
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But wait! Don't use these numbers in your code. The numeric values here are
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system dependent; fortunately, I thought of that when writing netifaces, so
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the module declares a range of values that you might need. e.g.
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>>> netifaces.AF_LINK
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18
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Again, on your system, the number may be different.
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So, what we've established is that the dictionary that's returned has one
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entry for each address family for which this interface has an address. Let's
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take a look at the ``AF_INET`` addresses now:
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>>> addrs = netifaces.ifaddresses('lo0')
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>>> addrs[netifaces.AF_INET]
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[{'peer': '127.0.0.1', 'netmask': '255.0.0.0', 'addr': '127.0.0.1'}]
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You might be wondering why this value is a list. The reason is that it's
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possible for an interface to have more than one address, even within the
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same family. I'll say that again: *you can have more than one address of
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the same type associated with each interface*.
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*Asking for "the" address of a particular interface doesn't make sense.*
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Right, so, we can see that this particular interface only has one address,
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and, because it's a loopback interface, it's point-to-point and therefore
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has a *peer* address rather than a broadcast address.
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Let's look at a more interesting interface.
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>>> addrs = netifaces.ifaddresses('en0')
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>>> addrs[netifaces.AF_INET]
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[{'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'}]
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This interface has two addresses (see, I told you...) Both of them are
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regular IPv4 addresses, although in one case the netmask has been changed
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from its default. The netmask *may not* appear on your system if it's set
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to the default for the address range.
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Because this interface isn't point-to-point, it also has broadcast addresses.
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Now, say we want, instead of the IP addresses, to get the MAC address; that
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is, the hardware address of the Ethernet adapter running this interface. We
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can do
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>>> addrs[netifaces.AF_LINK]
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[{'addr': '00:12:34:56:78:9a'}]
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Note that this may not be available on platforms without getifaddrs(), unless
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they happen to implement ``SIOCGIFHWADDR``. Note also that you just get the
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address; it's unlikely that you'll see anything else with an ``AF_LINK`` address.
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Oh, and don't assume that all ``AF_LINK`` addresses are Ethernet; you might, for
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instance, be on a Mac, in which case:
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>>> addrs = netifaces.ifaddresses('fw0')
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>>> addrs[netifaces.AF_LINK]
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[{'addr': '00:12:34:56:78:9a:bc:de'}]
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No, that isn't an exceptionally long Ethernet MAC address---it's a FireWire
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address.
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As of version 0.10.0, you can also obtain a list of gateways on your
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machine:
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>>> netifaces.gateways()
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{2: [('10.0.1.1', 'en0', True), ('10.2.1.1', 'en1', False)], 30: [('fe80::1', 'en0', True)], 'default': { 2: ('10.0.1.1', 'en0'), 30: ('fe80::1', 'en0') }}
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This dictionary is keyed on address family---in this case, ``AF_INET``---and
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each entry is a list of gateways as ``(address, interface, is_default)`` tuples.
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Notice that here we have two separate gateways for IPv4 (``AF_INET``); some
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operating systems support configurations like this and can either route packets
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based on their source, or based on administratively configured routing tables.
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For convenience, we also allow you to index the dictionary with the special
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value ``'default'``, which returns a dictionary mapping address families to the
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default gateway in each case. Thus you can get the default IPv4 gateway with
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>>> gws = netifaces.gateways()
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>>> gws['default'][netifaces.AF_INET]
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('10.0.1.1', 'en0')
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Do note that there may be no default gateway for any given address family;
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this is currently very common for IPv6 and much less common for IPv4 but it
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can happen even for ``AF_INET``.
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BTW, if you're trying to configure your machine to have multiple gateways for
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the same address family, it's a very good idea to check the documentation for
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your operating system *very* carefully, as some systems become extremely
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confused or route packets in a non-obvious manner.
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I'm very interested in hearing from anyone (on any platform) for whom the
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``gateways()`` method doesn't produce the expected results. It's quite
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complicated extracting this information from the operating system (whichever
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operating system we're talking about), and so I expect there's at least one
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system out there where this just won't work.
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3. This is great! What platforms does it work on?
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--------------------------------------------------
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It gets regular testing on OS X, Linux and Windows. It has also been used
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successfully on Solaris, and it's expected to work properly on other UNIX-like
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systems as well. If you are running something that is not supported, and
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wish to contribute a patch, please use BitBucket to send a pull request.
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4. What license is this under?
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------------------------------
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It's an MIT-style license. Here goes:
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Copyright (c) 2007-2014 Alastair Houghton
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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5. Why the jump to 0.10.0?
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--------------------------
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Because someone released a fork of netifaces with the version 0.9.0.
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Hopefully skipping the version number should remove any confusion. In
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addition starting with 0.10.0 Python 3 is now supported and other
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features/bugfixes have been included as well. See the CHANGELOG for a
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more complete list of changes.
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