Unable to establish P2P connection for miracast using gnome-network-displays

[Benjamin Berg]

Hi,

On Sun, 2024-01-14 at 19:28 +0100, Julian Sikorski wrote:
> Am 14.01.24 um 19:00 schrieb Jouni Malinen:
> > On Fri, Jan 05, 2024 at 10:46:57AM +0100, Julian Sikorski wrote:
> > > I am trying to figure out why gnome-network-displays is unable to establish
> > > a P2P connection with my Fire TV stick. I originally reported it to
> > > gnome-network displays, then to NetworkManager before being directed here.
> > > In brief, the p2p connection never goes up so I can never attempt to capture
> > > packets using wireshark or tcpdump. Same laptop and same Fire TV Stick work
> > > fine from Windows 11.
> > > I am attaching the wpa_supplicant debug log. Thank you for your help in
> > > advance.
> > 
> > Which WLAN driver are you using on this device (wlp1s0)?
> 
> I am using iwlwifi/iwlmvm. The hardware is Intel Wi-Fi 6 AX200.

Hmm, OK, I would have expected that to work fine.

> > It looks like the peer device might be using power saving mechanism
> > (Notice of Absence) that would require the local driver to be able to
> > synchronize the transmissions appropriately to be able to get them
> > through. The debug log here indicated that none of the numerous attempts
> > of sending a GO Negotiation Request to the peer resulted in the frame
> > being acknowledged which could imply that it was not listening at the
> > time the request went out. That said, it is difficult to say for certain
> > since the peer discovery part did succeed. In any case, this type of an
> > issue might require looking in more detail to a sniffer capture of the
> > IEEE 802.11 frames and the exact timing of them and/or figuring out what
> > kind of capabilities the local driver has for P2P.
> > 
> Sniffer would be a special hardware, correct? Like rtl-sdr? I have a 2.4 
> GHz Spectrum Analyzer but this is probably not what we need. Can a 
> sniffer be fashioned out of a second laptop?
> A while back miracast used to work intermittently, which is when I filed 
> https://gitlab.gnome.org/GNOME/gnome-network-displays/-/issues/285, 
> suspecting the issue is caused by IPv6 vs IPv4. Now I can no longer get 
> the connection to work under linux at all.

No need for special hardware. You can e.g. use a second (Intel) card,
change it into monitor mode "iw dev X set type monitor". Then put the
interface into the UP state ("ip link set X up"), configure the channel
and bandwidth using "iw" and grab a packet dump using tcpdump or
wireshark.

Now, if the peer device is using NoA's, that could be because the
FireTV stick is associated to another network at the same time. You
could try disconnecting it (and possibly the laptop) just to see if
that makes a difference.

Benjamin