Re: [PATCH] scan: limit COLOCATED_6GHZ flag to 6ghz devices

KeithG
2024-01-03T14:58:11Z

On Wed, Jan 3, 2024 at 6:58 AM James Prestwood <prestwoj@gmail.com> wrote:
>
> Hi Keith,
>
> On 1/3/24 4:56 AM, James Prestwood wrote:
> > It was seen that this flag seems to cause issues when in AP mode on
> > brcmfmac devices (e.g. the raspberry Pi 3). When in AP mode an a
> > scan is issued clients will disconnect. After testing this behavior
> > was isolated to the use of the COLOCATED_6GHZ flag.
> >
> > Besides working around the problem on this specific hardware the
> > patch itself makes sense as a non-6GHz capable device shouldn't use
> > this flag anyways.
> >
> > As stated in the patch comment, this isn't really a catch all
> > workaround since the flag is still used for devices supporting 6GHz.
> > If additional hardware exhibits this behavior we may need additional
> > changes like a hardware blacklist or an explicit option to disable
> > the flag.
> >
> > Reported-By: Keith G <ys3al35l@gmail.com>
>
> Could you double check it still fixes the issue you were seeing on brcmfmac?
>
> Thanks,
>
> James
>
> > ---
> > src/scan.c | 15 ++++++++++++++-
> > 1 file changed, 14 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/scan.c b/src/scan.c
> > index f48ffdef..8c6fdc08 100644
> > --- a/src/scan.c
> > +++ b/src/scan.c
> > @@ -394,7 +394,20 @@ static struct l_genl_msg *scan_build_cmd(struct scan_context *sc,
> > if (params->ap_scan)
> > flags |= NL80211_SCAN_FLAG_AP;
> >
> > - flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
> > + /*
> > + * TODO: This flag appears to cause some undesired behavior on brcmfmac
> > + * when the device is in AP mode, or has a secondary AP interface
> > + * running, causing clients to disconnect when a scan is issued.
> > + *
> > + * Only using this flag for 6GHz capable devices will limit this
> > + * behavior to only 6GHz devices and in reality makes sense
> > + * because a non-6GHz device shouldn't use this flag anyways. If
> > + * more issues still are seen related to this we may need an
> > + * explicit workaround, either brcmfmac-specific or a disable
> > + * option.
> > + */
> > + if (wiphy_band_is_disabled(sc->wiphy, BAND_FREQ_6_GHZ) != -ENOTSUP)
> > + flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;
> >
> > if (flags)
> > l_genl_msg_append_attr(msg, NL80211_ATTR_SCAN_FLAGS, 4, &flags);
James,

I will do this tonight. I was playing a lot with iwd that I had
patched with your suggestion last night. I was trying to resolve a
related problem and I did note that it was significantly more stable
with this patch, but I was still getting disconnected periodically. I
do not yet know if those disconnects were due to me or iwd and am
still investigating. I will continue this investigation with this new
patch applied. SHould this patch be against HEAD or can I safely patch
2.12?

Keith