libifconfig: A C API for ifconfig

[Pavel Odintsov]

Hello!

Great idea! Amazing! :)

On Fri, Mar 4, 2016 at 6:25 PM, Marie Helene Kvello-Aune
<marieheleneka at gmail.com> wrote:
> 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
>>
>>
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-- 
Sincerely yours, Pavel Odintsov