[pkg-wpa-devel] Bug#777170: Bug#777170: wpasupplicant: lots of CTRL-EVENT-SIGNAL-CHANGE messages in syslog and couldn't connect to wireless network

[Stefan Lippers-Hollmann]

tags -1 moreinfo

Hi

On 2015-02-05, Julian Gilbey wrote:
> Package: wpasupplicant
> Version: 2.3-1
> Severity: normal
> 
> I was trying to connect to a wireless network from my MacBook Pro
> running testing today, and it connected only intermittently.  I'm
> using network-manager, if that makes any difference.  It may be the
> network involved, as I can connect to my home network with no
> difficulties.

What wireless card are you using in your system/ which kernel driver
is in use? Overcrowded and noisy environments can certainly make the
situation worse, especially when you're almost out of reach of your
AP and may even hop between different, equally bad APs. I guess this
part of the issue is more of kernel issue though.

> The log file was filled with thousands of lines of the form:
> 
> Feb  5 16:54:18 redfield wpa_supplicant[2925]: wlan0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=0 noise=0 txrate=48000
> 
> which were appearing at the rate of about 10 per second.

CTRL-EVENT-SIGNAL-CHANGE is emitted at the MSG_INFO (default) logging
level - you can tune wpa_supplicant's logging level to reduce (and
subsequently hide) these messages. If you start wpa_supplicant by hand,
the parameters are -d, -dd, ... (to increase the logging level) or -q, 
-qq, ... (to reduce the logging level. ifupdown's wpa_supplicant 
integration allows you to set a debugging level via 
"wpa-debug-level %d" (where %d stands for positive or negative numbers,
e.g. -3, ..., 0, ..., 3). I do not know how (or if) networkmanager 
exposes access to these settings.

As long as your kernel driver/ module is working fine, you're usually
not supposed to get bothered by this event - it may be emitted 
occassionally, but rarely enough not to be noticed.

> I had a similar problem last week, and I wonder whether the same was
> happening then.
> 
> A reboot did not help.

Try to move around, closer to an access point, and check if the 
situation improves. Chances for wireless problems typically increase
in noisy environments.

> It made no difference whether I was plugged in or working on battery
> power, and I have also uninstalled laptop-mode-tools thinking that
> this might have been a contributory factor.

This should not affect your problem (but you never know).

> I can happily do further experiments next week if that would help.
[...]

Unless you're simply having problems with your signal level (too much
noise, APs (almost) out of range), this is most likely a kernel 
problem (and probably needs to get re-assigned there, wpa_supplicant
emitting these event notices is then merely a consequence of your
network going away/ re-appearing. While it's not impossible that this
might also be an interoperability problem between the AP and your 
client (where either kernel or wpa_supplicant might be to blame, but
given that hostapd, the other component of src:wpa, is the effective
reference implementation for APs, this is slightly less likely), I 
don't think this to be the issue here.

Regards
	Stefan Lippers-Hollmann
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