Re: WiFi AP selection

[Dan Williams <dcbw redhat com>]

On Tue, 2019-10-22 at 11:17 -0700, Clive McCarthy wrote:
> Thanks for your reply.
> My laptop, when first opened, reports (via the Network Manage, I
> suppose) that it is disconnected from the network. After a second or
> two it reports being connected. And it is. However, as I noted, the
> manager seems to choose the last known connection. This is a
> satisfactory algorithm for a fixed computer and for a computer
> connecting to a single AP. It isn't good for a movable computer with
> multiple APs.
>
> The Intel WiFi adapter is forced to shutdown when the computer is
> closed because there is a bug in the Intel-WiFi driver that doesn't
> handle suspend correctly. That is why there is a disconnect-connect
> sequence.

In this case we'd need the wpa_supplicant logs described below to
diagnose why the supplicant is picking that specific AP rather than
another.

Dan


> On 10/22/19 10:05 AM, Dan Williams wrote:
> > On Mon, 2019-10-21 at 20:42 -0700, Clive McCarthy via
> > networkmanager-
> > list wrote:
> > > I have a situation where I have multiple APs in a building all
> > > with
> > > the same SSID and WPA key but set to non-clashing frequencies.
> > > When I
> > > close my laptop and WiFi shuts down and I move to a new location
> > > the
> > > Network Manager seems to connect to the original AP, rather than
> > > one
> > > with a much stronger signal.
> > >
> > > The algorithm for AP connection is suboptimal (in other words
> > > dumb).
> > > The selection process should scan ALL APs, figure out which ones
> > > are
> > > known (SSID and WPA); measure their signal strength and then
> > > choose
> > > the known AP with the strongest signal.
> > >
> > > How hard is that?
> >
> > This is what NetworkManager should already be doing.
> >
> > Two things to check:
> >
> > 1) NetworkManager depends on being notified by systemd or upower
> > that
> > the laptop has suspended so that it can reconfigure when it wakes
> > up.
> > It should be pretty clear if that's happening through the
> > NetworkManager logs because it will say that it's going to sleep
> > and
> > waking up. For example:
> >
> > NetworkManager[1198]: <info>  [1571720491.7590] manager: sleep:
> > sleep requested (sleeping: no  enabled: yes)
> > NetworkManager[1198]: <info>  [1571720491.7599] device (wlp61s0):
> > state change: disconnected -> unmanaged (reason 'sleeping', sys-
> > iface-state: 'managed')
> > NetworkManager[1198]: <info>  [1571720491.7615] manager:
> > NetworkManager state is now ASLEEP
> > NetworkManager[1198]: <warn>  [1571752873.5481] sup-
> > iface[0x55f38553aaa0,wlp61s0]: connection disconnected (reason -3)
> > NetworkManager[1198]: <info>  [1571752873.5504] device (wlp61s0):
> > supplicant interface state: completed -> disconnected
> > NetworkManager[1198]: <info>  [1571752873.5803] manager: sleep:
> > wake requested (sleeping: yes  enabled: yes)
> > NetworkManager[1198]: <info>  [1571752873.6556] device (wlp61s0):
> > state change: activated -> unmanaged (reason 'sleeping', sys-iface-
> > state: 'managed')
> >
> > 2) enabling debug logging in wpa_supplicant with these two commands
> > will show you exactly what's going on:
> >
> > sudo dbus-send --system --print-reply --dest=fi.w1.wpa_supplicant1
> > /fi/w1/wpa_supplicant1 org.freedesktop.DBus.Properties.Set
> > string:fi.w1.wpa_supplicant1 string:DebugTimestamp
> > variant:boolean:true
> > sudo dbus-send --system --print-reply --dest=fi.w1.wpa_supplicant1
> > /fi/w1/wpa_supplicant1 org.freedesktop.DBus.Properties.Set
> > string:fi.w1.wpa_supplicant1 string:DebugLevel
> > variant:string:"msgdump"
> >
> > this will dump logs to wherever your system typically sends system
> > logs, like the systemd journal or syslog. Once you have these logs,
> > please review them to ensure there is no private information and
> > then
> > attach them to a reply so that we can figure out what's going on.
> >
> > Thanks!
> > Dan
>