Jacob Stanley « Blog
Written by Jacob Stanley on August 12, 2010
When opening a socket, if you don’t specify the address of the network interface you want to listen on, you’ll actually be listening on all of them. In a secure environment, this isn’t always what you want. That said, it’s quite useful to be able to show an administrator of your system a drop down with the addresses of the various network interfaces available to the software.
When I set out to do this in Haskell I discovered that there wasn’t anything available that would let me get the address information for my network interfaces. So, I set out build network-info and learned how to use the Foreign Function Interface (FFI) in the process.
Getting the IPv4, IPv6 and MAC addresses of your local network interfaces is now just a cabal install away:
cabal install network-info
Once you’ve got the library installed it’s simple to get your network details:
import Network.Info
main = do
ns <- getNetworkInterfaces
mapM_ (putStr . showInterface) ns
showInterface n = name n ++ "\n"
++ " IPv4: " ++ show (ipv4 n) ++ "\n"
++ " IPv6: " ++ show (ipv6 n) ++ "\n"
++ " MAC: " ++ show (mac n) ++ "\n"Running this on my Ubuntu box yields something similar to this:
$ runghc getaddr.hs
lo
IPv4: 127.0.0.1
IPv6: 0:0:0:0:0:0:0:1
MAC: 00:00:00:00:00:00
eth0
IPv4: 10.0.2.5
IPv6: fe80:0:0:0:f00:15ff:fcf9:c677
MAC: 08:00:72:5f:6c:19
And on Windows 7:
> runghc getaddr.hs
Local Area Connection
IPv4: 192.168.0.107
IPv6: fe80:0:0:0:ef54:7861:7df:6b7c
MAC: 00:26:c9:e1:87:8c
VirtualBox Host-Only Network
IPv4: 192.168.56.1
IPv6: fe80:0:0:0:14b4:b3af:557:ad4a
MAC: 08:00:27:00:d8:2a
Loopback Pseudo-Interface 1
IPv4: 127.0.0.1
IPv6: 0:0:0:0:0:0:0:1
MAC: 00:00:00:00:00:00
... snipped out some garbage network interfaces
You’ll notice that the IPv6 addresses don’t have fully collapsed groups of zeros just yet, but they are still valid addresses.
I’ve tested this on Ubuntu 10.04, Windows XP & Windows 7. It won’t install on Mac OS X or BSD just yet because of restrictions in the cabal file. I need to check out how getifaddrs works on those systems so I know what to do in the FFI code.