Re: WiFi AP selection



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.

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




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