Re: nl80211 scanning from userspace

[Christopher Piggott <cpiggott@gmail.com>]

Forgive me if this is an obtuse question but why would one use
nl_socket_add_membership, if all that isn't necessary to get back the
scan results?

On Mon, Aug 16, 2010 at 5:55 PM, Christopher Piggott <cpiggott@gmail.com> wrote:
> OHHH.  I am with you now.  I looked at driver_nl80211.c and somehow
> had a blind spot  when it came to message NLM_F_DUMP.  I see it now,
> and it's sending me back results.
>
> I am tempted to write a slightly higher level API on top of some of
> this, once I understand the semantics of all of this a little better.
> I will search around first and see if any attempts have already been
> made.
>
> Thank you very much for pushing me in the right direction.
>
> --Chris
>
>
> On Mon, Aug 16, 2010 at 5:43 PM, Johannes Berg
> <johannes@sipsolutions.net> wrote:
>> On Mon, 2010-08-16 at 17:22 -0400, Christopher Piggott wrote:
>>> It's hard to figure out what's going on sometimes.  I set up an error handler:
>>>
>>> static int error_handler(struct sockaddr_nl *nla, struct nlmsgerr
>>> *err, void *arg) {
>>>     printf("ERROR %s (%d)\n", strerror(err->error), err->error);
>>>     return NL_SKIP;
>>> }
>>>
>>> which also returns -95 (operation not supported) just as you said.
>>> So, I'll have to figure out what you mean by "dumping."
>>>
>>> I did find this:
>>>
>>>         mcid = nl_get_multicast_id(state->nl_sock, "nl80211", "scan");
>>>
>>> in iw:event.c and traced it to some code in iw:genl.c, a file that
>>> starts out by commenting "This ought to be provided by libnl".  That
>>> situation doesn't seem to have changed.
>>>
>>> Is this the area of the code you mean when you say "dump" ?  That I
>>> need to register myself to receive the scan results?
>>
>> No, you need to use NLM_F_DUMP etc. Really, check wpa_supplicant :)
>>
>> johannes
>>
>>
>