Re: Limit on number of APs? Some way to force-rescan?

[Derek Atkins <warlord MIT EDU>]

Quoting Dan Williams <dcbw redhat com>:

> It pulls them down and enlarges the buffer a few times before failing
> out if the buffer required is too large.  But I don't think you're
> hitting this for a number of reasons:
>
> 1) if ((errno == E2BIG) && (buflen < 100000)) <---- that means NM will
> stop trying to get results of the required buffer is greater than 100K.
> That should _never_ happen unless you have LOTS of APs, like probably >
> 100.  An AP record is 99% of the time be less than 200 bytes.
>
> 2) You should be seeing the message "unknown error, or the card returned
> too much scan info" in the logs if NM truncates scan results

Here's what I see:

[root cliodev ~]# grep -i scan /var/log/messages | tail
Jul 12 15:53:55 cliodev NetworkManager: <information>   wpa_supplicant(11966):
Received 2988 bytes of scan results (21 BSSes)
Jul 12 15:53:55 cliodev NetworkManager: <information>   wpa_supplicant(11966):
Scan results: 21
Jul 12 16:27:09 cliodev NetworkManager: <information>   SUP: sending command
'AP_SCAN 1'
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
Setting scan request: 0 sec 100000 usec
Jul 12 16:27:19 cliodev NetworkManager: <information>   
wpa_supplicant(12144):   41 50 5f 53 43 41 4e 20 31                     
   AP_SCAN 1
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
Setting scan request: 0 sec 0 usec
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
State: DISCONNECTED -> SCANNING
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
Starting AP scan (broadcast SSID)
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
Received 3479 bytes of scan results (24 BSSes)
Jul 12 16:27:19 cliodev NetworkManager: <information>   wpa_supplicant(12144):
Scan results: 24

> 3) ipw2200 can do just fine with > 30 access points, which tells me that
> the buffer being not large enough for all the results is just not the
> problem

Yeah.  It certainly looks like the scan data is under 3KB..   On the other
hand all the logs are about wpa_supplicant scan results.  NM itself isn't
reporting anything.

> You can try to do something like this to print out the results (for
> HEAD):

I'm not running head.  I'm running 0.6.3.  Will this patch apply to
0.6.3, too?  (I can try to add it to the SRPM and test it).

> --- nm-device-802-11-wireless.c.foo	2006-07-12 15:58:35.000000000 -0400
> +++ nm-device-802-11-wireless.c	2006-07-12 16:00:19.000000000 -0400
> @@ -3443,6 +3443,9 @@
> 				/* New AP with some defaults */
> 				ap = nm_ap_new ();
> 				nm_ap_set_address (ap, (const struct ether_addr 
> *)(iwe->u.ap_addr.sa_data));
> +#define MAC2STR(a) (a)[0], (a)[1], (a)[2], (a)[3], (a)[4], (a)[5]
> +#define MACSTR "%02x:%02x:%02x:%02x:%02x:%02x"
> +nm_debug("New AP found: " MACSTR "\n", MAC2STR(iwe->u.ap_addr.sa_data));
> 				break;
> 			case SIOCGIWMODE:
> 				switch (iwe->u.mode)
>
> Dan
>
> > Is the scan logged anywhere by NM?

A new AP showed up in my list..  And it's #1 in my scan list.   So I'm
still thinking that NM isn't seeing the full scan results.

-derek

--
      Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
      Member, MIT Student Information Processing Board  (SIPB)
      URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
      warlord MIT EDU                        PGP key available