libifconfig: A C API for ifconfig

[Marie Helene Kvello-Aune]

Hey!

I'm currently working on a library called 'libifconfig' which will provide
a C API to do the actual work that /sbin/ifconfig currently does, except
that of lib80211. What sparked this project was a wish to simplify
maintenance of the ifconfig program by making it primarily focus on the
user's command line interaction, and not so much on the specifics of how
those things are done behind the scenes.

One advantage to having such a library is to reduce code duplication  and
thus improve maintainability, and another is that it would make it easier
for third party programs to query the network stack without having to spawn
ifconfig and parse its output. I'm sure there's more, but those were the
ones at the top of my head when writing this e-mail.

Currently, the API is implemented so that the application provides an
interface name, required value if any (say, to set description or name), or
a reference to a value if retrieving information, such as an interfaces
description or MTU.

The calling application won't have to provide a socket, as this is part of
the 'behind the scenes' things that the library takes care of. The API will
ask only for the information that is required to do what it's supposed to
do, nothing more and nothing less.

Each API call will return a value of either "0" for success or "-1" for
failure and there will be an instance (libifconfig_errstate) of a struct
containing all information relevant to the error. I found this was the most
sensible way of properly communicating exactly what went wrong with a call,
as some API methods do several system calls behind the scenes. I found it
necessary for the API to be this communicative as /sbin/ifconfig is rather
detailed in its error messages, and  I don't want /sbin/ifconfig's
behaviour to be altered in any way as a result of this libification.

The implementation of libifconfig currently exist only on my machine, but I
will submit a patch to reviews.freebsd.org to solicit feedback once I've
cleaned up the code some and implemented & verified the error feedback
mechanism.

Copy-pasting some of the simple stuff from the header file to give a feel
for how I envision the API:

int libifconfig_get_description(const char *name, char **description);
int libifconfig_set_description(const char *name, const char
*newdescription);
int libifconfig_unset_description(const char *name);

int libifconfig_set_mtu(const char *name, const int mtu);
int libifconfig_get_mtu(const char *name, int *mtu);


Your feedback is quite welcome. :)

Regards,
Marie Helene Kvello-Aune