libifconfig: A C API for ifconfig

[Marie Helene Kvello-Aune]

Hey!

Yes, I am aware of libxo, and I hope that libxo-ification of /sbin/ifconfig
will be easier to do once the 'hairy' bits aren't a part of /sbin/ifconfig
any more. :)

- Marie Helene

On Fri, Mar 4, 2016 at 4:20 PM Alan Somers <asomers at freebsd.org> wrote:

> On Fri, Mar 4, 2016 at 8:10 AM, Marie Helene Kvello-Aune <
> marieheleneka at gmail.com> wrote:
>
>> 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
>>
>
> This sounds like an awesome idea.  ifconfig is my least favorite program
> to parse.  BTW, are you aware of the ongoing libxo work?  That effort fixes
> the problem of parsing the output of utilities like ifconfig, though it
> doesn't do anything to simplify their maintenance.
>
> -Alan
>
>