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wext: Fix scan result signal levels when driver reports in dBm

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wpa_supplicant showed signal levels incorrectly with some drivers:
Jun  6 16:29:36 rupert wpa_supplicant[18945]: Current BSS: 00:0d:97:11:40:d6
level=190
Jun  6 16:29:36 rupert wpa_supplicant[18945]: Selected BSS: 00:0d:97:11:50:09
level=192

Judging from output from other tools (iwlist) and the min_diff block
at the end of wpa_supplicant_need_to_roam, it seems these values
should actually be negative. Specifically, if one treats that number
as a signed char instead of unsigned, everything matches up.

To be honest, I've little to no understanding of wireless, but looking
at the source code for wireless-tools (iw_print_stats in iwlib.c), it
seems that the fields of the iw_quality struct need to be decoded
differently depending on various flags. I guess
src/drivers/driver_wext.c should have similar logic in
wext_get_scan_qual.

I wrote a patch that attempts to replicate some of that logic,
although it may be more complicated than is necessary; I think some of
the complexity is for backwards-compatibility, which might not be
necessary depending on wpa_supplicant's dependencies? In any case, it
is attached. Again, I don't know how any of this works, so it's likely
the patch is a bit off. But I think at least the logic to determine
min_diff in wpa_supplicant_need_to_roam would be more accurate if
level were determined correctly.
This commit is contained in:
David A Benjamin 2010-09-05 19:04:10 +03:00 committed by Jouni Malinen
parent 8602b0f213
commit 32f4e7b124
2 changed files with 15 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

15
src/drivers/driver_wext.c
View file

@ -1117,7 +1117,8 @@ static void wext_get_scan_freq(struct iw_event *iwe,
}
static void wext_get_scan_qual(struct iw_event *iwe,
static void wext_get_scan_qual(struct wpa_driver_wext_data *drv,
struct iw_event *iwe,
struct wext_scan_data *res)
{
res->res.qual = iwe->u.qual.qual;
@ -1131,6 +1132,14 @@ static void wext_get_scan_qual(struct iw_event *iwe,
res->res.flags |= WPA_SCAN_NOISE_INVALID;
if (iwe->u.qual.updated & IW_QUAL_DBM)
res->res.flags |= WPA_SCAN_LEVEL_DBM;
if ((iwe->u.qual.updated & IW_QUAL_DBM) ||
((iwe->u.qual.level != 0) &&
(iwe->u.qual.level > drv->max_level))) {
if (iwe->u.qual.level >= 64)
res->res.level -= 0x100;
if (iwe->u.qual.noise >= 64)
res->res.noise -= 0x100;
}
}
@ -1406,7 +1415,7 @@ struct wpa_scan_results * wpa_driver_wext_get_scan_results(void *priv)
wext_get_scan_freq(iwe, &data);
break;
case IWEVQUAL:
wext_get_scan_qual(iwe, &data);
wext_get_scan_qual(drv, iwe, &data);
break;
case SIOCGIWENCODE:
wext_get_scan_encode(iwe, &data);
@ -1504,6 +1513,8 @@ static int wpa_driver_wext_get_range(void *priv)
"assuming WPA is not supported");
}
drv->max_level = range->max_qual.level;
os_free(range);
return 0;
}

2
src/drivers/driver_wext.h
View file

@ -47,6 +47,8 @@ struct wpa_driver_wext_data {
int scan_complete_events;
int cfg80211; /* whether driver is using cfg80211 */
u8 max_level;
};
int wpa_driver_wext_get_bssid(void *priv, u8 *bssid);