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Subject: Re: [Bug] carl9170 + wpa_supplicant: P2P mode doesn't work with
 separate interfaces
From:   =?UTF-8?Q?Frank_Sch=c3=a4fer?= <fschaefer.oss@googlemail.com>
To:     chunkeey@googlemail.com, j@w1.fi
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Date:   Tue, 5 May 2020 17:04:07 +0200
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Christian, Jouni,

I have tracked this down as far as I can get without some help.
It would be nice if you could take a closer look at the results - see 
questions below.


Am 29.04.20 um 18:22 schrieb Frank Schäfer:
>
> Am 27.04.20 um 18:53 schrieb Frank Schäfer:
>>
>> Am 18.04.20 um 13:20 schrieb Frank Schäfer:
>>> Hi,
>>>
>>> I'm currently testing Miraclecast 
>>> (https://github.com/albfan/miraclecast), an open source 
>>> Wifi-Display/Miracast implementation.
>>> In one of my setups, I'm using a carl9170 device as sink, which 
>>> fails with the following debugging output:
>>>
>>> ...
>>> TRACE: wpa: raw message: IFNAME=wlp0s2f1u8 <3>CTRL-EVENT-SCAN-STARTED
>>> TRACE: wpa: raw message: <3>P2P-PROV-DISC-PBC-REQ 8e:79:67:11:22:33 
>>> p2p_dev_addr=8e:79:67:11:22:33 pri_dev_type=10-0050F204-5 name='MY 
>>> DEVICE' config_methods=0x188 dev_capab=0x25 group_capab=0x0
>>> TRACE: wpa: raw message: <3>P2P-GO-NEG-REQUEST 8e:79:67:11:22:33 
>>> dev_passwd_id=4 go_intent=0
>>> DEBUG: supplicant: GO Negotiation Request from 8e:79:67:11:22:33 
>>> (supplicant_event_p2p_go_neg_request() in 
>>> ../../../src/wifi/wifid-supplicant.c:1065)
>>> DEBUG: supplicant: connect to 8e:79:67:11:22:33 via pbc/(null) 
>>> (supplicant_peer_connect() in ../../../src/wifi/wifid-supplicant.c:739)
>>> TRACE: wpa: raw message: <3>P2P-FIND-STOPPED
>>> DEBUG: supplicant: p2p-scanning stopped on wlp0s2f1u8 
>>> (supplicant_event_p2p_find_stopped() in 
>>> ../../../src/wifi/wifid-supplicant.c:904)
>>> TRACE: wpa: raw message: OK
>>>
>>> TRACE: wpa: raw message: <3>P2P-GO-NEG-SUCCESS role=GO freq=2462 
>>> ht40=0 peer_dev=8e:79:67:11:22:33 peer_iface=8e:79:67:11:22:33 
>>> wps_method=PBC
>>> DEBUG: supplicant: set STA-MAC for 8e:79:67:11:22:33 from <none> to 
>>> 8e:79:67:11:22:33 (via GO-NEG-SUCCESS) 
>>> (supplicant_event_p2p_go_neg_success() in 
>>> ../../../src/wifi/wifid-supplicant.c:1194)
>>> TRACE: wpa: raw message: IFNAME=p2p-0 <3>Failed to start AP 
>>> functionality
>>> DEBUG: supplicant: unhandled wpas-event: IFNAME=p2p-0 <3>Failed to 
>>> start AP functionality (supplicant_event() in 
>>> ../../../src/wifi/wifid-supplicant.c:1498)
>>> TRACE: wpa: raw message: <3>P2P-GROUP-FORMATION-FAILURE
>>> DEBUG: supplicant: peer MY DEVICE connection failed 
>>> (supplicant_event_p2p_group_formation_failure() in 
>>> ../../../src/wifi/wifid-supplicant.c:1318)
>>> TRACE: wpa: raw message: <3>P2P-GROUP-REMOVED p2p-0 GO 
>>> reason=FORMATION_FAILED
>>> DEBUG: supplicant: stray P2P-GROUP-REMOVED: <3>P2P-GROUP-REMOVED 
>>> p2p-0 GO reason=FORMATION_FAILED 
>>> (supplicant_event_p2p_group_removed() in 
>>> ../../../src/wifi/wifid-supplicant.c:1286)
>>> DEBUG: supplicant: sent P2P_FIND to wpas on wlp0s2f1u8 
>>> (supplicant_p2p_start_scan() in 
>>> ../../../src/wifi/wifid-supplicant.c:2036)
>>> TRACE: wpa: raw message: OK
>>>
>>> DEBUG: supplicant: p2p-scanning now active on wlp0s2f1u8 
>>> (supplicant_p2p_find_fn() in ../../../src/wifi/wifid-supplicant.c:1917)
>>> TRACE: wpa: raw message: IFNAME=wlp0s2f1u8 <3>CTRL-EVENT-SCAN-STARTED
>>> ...
>>>
>>>
>>> Searching the web for similar problems leads to the following thread:
>>> https://marc.info/?l=hostap&m=135336063022534
>>>
>>> As suggested there, I have patched the Miraclecast sources to use 
>>> the wpa_supplicant configuration parameter p2p_no_group_iface=1.
>>> So far, this works fine.
>>>
>>>
>>> Regards,
>>> Frank Schäfer
>>>
>>
>> I finally managed to create extended logs and to compare the working 
>> ("GOOD") and non-working ("BAD") case.
>> See attachment.
>> If anything is missing, please let me know.
>>
>> Hth,
>> Frank
>>
>
> Ok, this is what I can see happening in carl9170 with regards to the 
> interfaces:
>
> 1) 1 interface is added+initialized: NL80211_IFTYPE_STATION, p2p=false 
> (when miracle-wifid is started)
>
> Non-working case (p2p_no_group_iface=0=default):
> 2a) 1 interface is added: NL80211_IFTYPE_STATION, p2p=true (apparently 
> the p2p group interface)
> 2b) 1 interface is removed: NL80211_IFTYPE_STATION, p2p=true 
> (apparently because setting of the interface flags failed with -EBUSY)
> 3) 1 interface is added+initialized: NL80211_IFTYPE_AP, p2p=true
>    => fails with -EBUSY, because main_vif->p2p is false (main.c, line 
> 656)
>
> Working case (p2p_no_group_iface=1):
> 2) 1 interface is removed: NL80211_IFTYPE_STATION, p2p=false
> 3) 1 interface is added+initialized: NL80211_IFTYPE_AP, p2p=true

UPDATE (removed some confusion due to async output to the log, added 
disconnection/exit):

1) STA non-p2p interface is added+initialized (miracle-wifid start)

Connection attempt:

BAD case (p2p_no_group_iface=0=default):
2a) STA p2p interface is added (p2p group interface)
2b) STA p2p interface is removed (p2p group interface)
3) AP p2p interface is added: fails with -EBUSY (carl9170 main.c, line 
654), because main_vif->p2p is false in line 648
=> connection fails

GOOD case (p2p_no_group_iface=1):
2) STA non-p2p interface is removed
3) AP p2p interface is added+initialized
=> connection established, streaming

Disconnection (GOOD case (p2p_no_group_iface=1)):
4) AP p2p interface is removed
5) STA non-p2p interface is added+initialized

miracle-wifid exit:
6) STA non-p2p is interface is removed


So there are two things to investigate further: BAD 3) and GOOD 2)

@Christian:
Can you please check if the behavior of carl9170 (BAD 3)) is correct ?
Reading the comments and the rest of the code in the switch 
(main_vif->type) {} section, I wonder if the main_vif->p2p check in line 
654 is correct/required.
Isn't all we have to make sure, that the AP interface always becomes the 
main interface ? Why does main_vif->p2p matter here ?
A few lines below (660/661), STA interfaces are always added if the main 
interface is a AP interface, no matter if any of them is p2p or not.

@Jouni:
Why does wpa_supplicant remove the STA non-p2p interface before creating 
the AP p2p interface if p2p_no_group_iface=1, but not if 
p2p_no_group_iface=0 ?
That seems to be inconsistent.
In case the driver doesn't support concurrent interfaces, the behavior 
of p2p_no_group_iface=1 seems to make things work.
But I don't know if there might be any disadvantages.
In my case, the removed interface is added again later (5)) and 
everything works fine.

Regards,
Frank