Wifi Direct GO Negotiation

Dmitry Shmidt dimitrysh
Fri May 16 10:58:57 PDT 2014 

+ Vinit

On Fri, May 16, 2014 at 8:10 AM, Arend van Spriel <arend at broadcom.com> wrote:
> + Dmitry
>
>
> On 05/16/14 11:39, Andrea Chittano wrote:
>>
>> Hi Arend,
>> first of all thank you for your time.
>> I' m going to try to give you a summary of what I want to do.
>>
>> I want to develop an app which implements WiFi Direct Protocol.
>> In particular I need to be sure that it performs GO Negotiation
>> procedure correctly.
>> According to what android guide says, if I want that a device (D1)
>> starts a connection with another device (D2),
>> D1 has to call connect() method.
>> This method admits as parameter an object called config.
>> config contains 3 fields:
>>
>>     * The device MAC address that uniquely identifies a Wi-Fi p2p device
>>
>>       to connect to (in my example it will be MAC of D2)
>>     * groupOwnerIntent of D1 (since it is starting the connection)
>>     * wps info of D1 (since it is starting the connection)
>
>
> Yup. Going through the online pages I only see described how to do it from
> D1 perspective, but unclear what should be done in D2. Maybe Dmitry can
> elaborate on that. I get the impression that the whole GO negotiation is
> done between wpa_supplicants on D1 and D2. The group owner intent should be
> configured when a device is enabled for P2P as you can never know when
> another device will initiate a GO negotiation procedure.

As far as I know in Android Wifi Direct negotiation is using default go_intent=6
(from 0..15 range), so it is not certain if D1 or D2 will be GO. For
Miracast API
go_intent=0 is used, so phone it trying to be GC.
My point is that connection initiator is not GO by default.


>
> Regards,
> Arend
>
>> After that android will use WifiNative class to send the command to
>> wpa_supplicant.
>> Now, wpa_supplicant takes charge of building the GO negotiation request
>> to send it to D2.
>>
>> Which is the behaviour of D2 after receiving D1 GO negotiation request?
>>
>> In my app I've tried to instantiate a configobject containing GO intent
>>
>> of D2, but D1 becames always GO, even if GO intent of D2 is greater than
>> D1 one.
>>
>>
>> Thanks
>> Andrea
>>
>>  > Date: Thu, 15 May 2014 21:27:28 +0200
>>  > From: arend at broadcom.com
>>  > To: andrea.chittano at hotmail.it
>>  > CC: moon.linux at yahoo.com; hostap at lists.shmoo.com
>>  > Subject: Re: Wifi Direct GO Negotiation
>>  >
>>  > On 05/15/14 18:25, Andrea Chittano wrote:
>>  > > Sorry guys for my inexperience, but this thing are driving me mad.
>>  > >
>>  > > Tell me if i'm wrong.
>>  > > Does the function at line 525 of the following link
>>  > >
>>  > >
>>
>> http://code.metager.de/source/xref/hostapd-wpa_supplicant/src/p2p/p2p_go_neg.c?r=0e0e1e564f3dd8d2a6b645d079b46eba0acc7f83
>>  > >
>>  > > that is
>>  > >
>>  > > *void* p2p_process_go_neg_req
>>
>> <http://code.metager.de/source/s?defs=p2p_process_go_neg_req&project=hostapd-wpa_supplicant>(*struct*
>> p2p_data
>>
>> <http://code.metager.de/source/s?defs=p2p_data&project=hostapd-wpa_supplicant>
>> *p2p
>>
>> <http://code.metager.de/source/s?defs=p2p&project=hostapd-wpa_supplicant>,*const*
>> u8
>> <http://code.metager.de/source/s?defs=u8&project=hostapd-wpa_supplicant>
>> *sa
>> <http://code.metager.de/source/s?defs=sa&project=hostapd-wpa_supplicant>,
>>  > > *const* u8
>> <http://code.metager.de/source/s?defs=u8&project=hostapd-wpa_supplicant>
>> *data
>>
>> <http://code.metager.de/source/s?defs=data&project=hostapd-wpa_supplicant>,size_t
>>
>> <http://code.metager.de/source/s?defs=size_t&project=hostapd-wpa_supplicant>
>> len
>>
>> <http://code.metager.de/source/s?defs=len&project=hostapd-wpa_supplicant>,*int*
>> rx_freq
>>
>> <http://code.metager.de/source/s?defs=rx_freq&project=hostapd-wpa_supplicant>)
>>  > >
>>  > >
>>  > > represent the processing (performed by Device2) of the GO negotiation
>>  > > request that Device1 sent Device2?
>>  > >
>>  > > This function performs at line 687
>>  > >
>>  > > p2p_go_det
>>
>> <http://code.metager.de/source/s?refs=p2p_go_det&project=hostapd-wpa_supplicant>(p2p
>>
>> <http://code.metager.de/source/s?defs=p2p&project=hostapd-wpa_supplicant>->go_intent
>>
>> <http://code.metager.de/source/s?defs=go_intent&project=hostapd-wpa_supplicant>,
>> *msg
>>
>> <http://code.metager.de/source/s?defs=msg&project=hostapd-wpa_supplicant>.go_inten
>>
>> <http://code.metager.de/source/s?defs=go_intent&project=hostapd-wpa_supplicant>t)
>>  > >
>>  > >
>>  > > which returns the highest GO intent between local GO intent and
>> received
>>  > > one.
>>  > > If I'm not wrong, according to what Arend told me Device2 get local
>> GO
>>  > > intent from wpa_supplicant configuration file. But I've found only
>> one
>>  > > way to set the local GO intent and it is here :
>>  > >
>>  > >
>> http://code.metager.de/source/xref/hostapd-wpa_supplicant/src/p2p/p2p.c
>>  > >
>>  > > at line 1387, into the function
>>  > >
>>  > > *int* p2p_connect
>>
>> <http://code.metager.de/source/s?refs=p2p_connect&project=hostapd-wpa_supplicant>(*struct*
>> p2p_data
>>
>> <http://code.metager.de/source/s?defs=p2p_data&project=hostapd-wpa_supplicant>
>> *p2p
>>
>> <http://code.metager.de/source/s?refs=p2p&project=hostapd-wpa_supplicant>,*const*
>> u8
>> <http://code.metager.de/source/s?defs=u8&project=hostapd-wpa_supplicant>
>> *peer_addr
>>
>> <http://code.metager.de/source/s?refs=peer_addr&project=hostapd-wpa_supplicant>,
>>  > > *enum* p2p_wps_method
>>
>> <http://code.metager.de/source/s?defs=p2p_wps_method&project=hostapd-wpa_supplicant>
>> wps_method
>>
>> <http://code.metager.de/source/s?defs=wps_method&project=hostapd-wpa_supplicant>,
>>  > > *int* go_intent
>>
>> <http://code.metager.de/source/s?defs=go_intent&project=hostapd-wpa_supplicant>,*const*
>> u8
>> <http://code.metager.de/source/s?defs=u8&project=hostapd-wpa_supplicant>
>> *own_interface_addr
>>
>> <http://code.metager.de/source/s?defs=own_interface_addr&project=hostapd-wpa_supplicant>,
>>  > > *unsigned* *int* force_freq
>>
>> <http://code.metager.de/source/s?defs=force_freq&project=hostapd-wpa_supplicant>,*int*
>> persistent_group
>>
>> <http://code.metager.de/source/s?defs=persistent_group&project=hostapd-wpa_supplicant>,
>>  > > *const* u8
>> <http://code.metager.de/source/s?defs=u8&project=hostapd-wpa_supplicant>
>> *force_ssid
>>
>> <http://code.metager.de/source/s?defs=force_ssid&project=hostapd-wpa_supplicant>,size_t
>>
>> <http://code.metager.de/source/s?defs=size_t&project=hostapd-wpa_supplicant>
>> force_ssid_len
>>
>> <http://code.metager.de/source/s?defs=force_ssid_len&project=hostapd-wpa_supplicant>,
>>  > > *int* pd_before_go_neg
>>
>> <http://code.metager.de/source/xref/hostapd-wpa_supplicant/src/p2p/p2p.c#pd_before_go_neg>,*unsigned*
>> *int* pref_freq
>>
>> <http://code.metager.de/source/s?defs=pref_freq&project=hostapd-wpa_supplicant>,u16
>> <http://code.metager.de/source/s?defs=u16&project=hostapd-wpa_supplicant>
>> oob_pw_id
>>
>> <http://code.metager.de/source/s?defs=oob_pw_id&project=hostapd-wpa_supplicant>)
>>  > >
>>  > >
>>  > >
>>  > >
>>  > >
>>  > > According to what specifications say, it is used to start a GO
>> negotiation.
>>  > > So my question is, how can I set the local GO intent for Device2
>> without
>>  > > using p2p_connect() function?
>>  > > I would make it by means of an android application. Can I do this?
>>  >
>>  > Maybe it would help to give some high-level information on what you are
>>  > trying to do. I am not familiar with Android solution, but most likely
>>  > Android provides an API for applications that is handled by their
>>  > framework/middleware to get it in wpa_supplicant (see [1]).
>>  >
>>  > Regards,
>>  > Arend
>>  >
>>  > [1] http://developer.android.com/guide/topics/connectivity/wifip2p.html
>>  >
>>  > > Thanks for your help.
>>  > > Andrea
>>  > >
>>  > >
>>  > > > Date: Wed, 14 May 2014 10:21:56 -0700
>>  > > > From: moon.linux at yahoo.com
>>  > > > Subject: Re: Wifi Direct GO Negotiation
>>  > > > To: arend at broadcom.com; andrea.chittano at hotmail.it
>>  > > > CC: hostap at lists.shmoo.com
>>  > > >
>>  > > > Hi Arend,
>>  > > >
>>  > > > I agree with what you said regarding the AP.
>>  > > >
>>  > > > One more question: Any device with WPS capabilty can join a P2P
>> network.
>>  > > >
>>  > > > Thanks.
>>  > > > -Anand Moon
>>  > > >
>>  > > >
>>  > > >
>>  > > > On Wednesday, May 14, 2014 2:56 PM, Arend van Spriel
>>  > > <arend at broadcom.com> wrote:
>>  > > > On 14-05-14 05:03, Anand Moon wrote:
>>  > > > > Hi All,
>>  > > > >
>>  > > > > I would like to add new question to this thread.
>>  > > > >
>>  > > > > If the AP has the capability to support p2p and wps, how will
>>  > > > > these two devices communicate with the AP.
>>  > > > > Will this AP become P2P group owner (P2P Go) and the other
>> devices
>>  > > P2P Clients ?
>>  > > >
>>  > > > I am not sure whether this scenario makes sense. P2P typically
>> involves
>>  > > > two STAs. They may be connected to some AP, but if both are
>> connected to
>>  > > > the same AP there may be not so much need to setup a P2P
>> connection.
>>  > > >
>>  > > > > I would like to know how to judge if the wireless interface
>>  > > supports P2P
>>  > > > > is it with the "Supported interface modes" or "Supported RX frame
>>  > > types" ?
>>  > > > >
>>  > > > > If the device support following p2p mode then how do we need to
>>  > > configure them.
>>  > > > >
>>  > > > > Supported interface modes:
>>  > > > > * IBSS
>>  > > > > * managed
>>  > > > > * AP * AP/VLAN
>>  > > > > * monitor
>>  > > > > * mesh point
>>  > > > > * P2P-client
>>  > > > > * P2P-GO
>>  > > > >
>>  > > > > How do we configure these P2P modes for interface?
>>  > > > > Please share your thoughts.
>>  > > >
>>  > > > Just use nl80211 API, ie. NL80211_CMD_SET_INTERFACE.
>> wpa_supplicant is
>>  > > > doing that in src/drivers/driver_nl80211.c
>>  > > >
>>  > > > Regards,
>>  > > > Arend
>>  > > >
>>  > > >
>>  > > > > -Anand Moon
>>  > > > >
>>  > > > >
>>  > > > > On Tuesday, May 13, 2014 6:31 PM, Arend van Spriel
>>  > > <arend at broadcom.com> wrote:
>>  > > > > On 05/13/14 14:03, Andrea Chittano wrote:
>>  > > > >> Hi, my name is Andrea.
>>  > > > >> I'm working on WiFi Direct and I found a thread about it.
>>  > > > >> I've some doubts about it.
>>  > > > >> Let's suppose we have 2 devices. Let's call D1 and D2.
>>  > > > >> Let's suppose D1 sends a request of connection to D2 (D1
>> doesn't known
>>  > > > >> D2 so no persistent connection there exist).
>>  > > > >> The first step that wpa_supplicant on D1 is to send a GO
>> negotiation
>>  > > > >> request containing, among all,GO intent (of D1).
>>  > > > >> I want to understand how wpa_supplicant on D2 acquires the GO
>>  > > intent of
>>  > > > >> D2 in order to compare it with whichone sent by D1.
>>  > > > >> Can someone explain me this?
>>  > > > >
>>  > > > > Both devices have their own go intent configuration in
>> wpa_supplicant
>>  > > > > configuration file. D2 sends own go intent value in the GO
>> negotiation
>>  > > > > response. The device with the highest GO intent will become GO.
>>  > > > >
>>  > > > > Regards,
>>  > > > > Arend
>>  > > > >
>>  > > > >> Thanks,
>>  > > > >> Andrea
>>  > > > >>
>>  > > > >>
>>  > > > >>
>>  > > > >> _______________________________________________
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>>  > > > >
>>  > > > >
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>>  > > >
>>  >
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