Bug 748075

Summary: Wifi signal calculation always shows 100%
Product: Red Hat Enterprise Linux 6 Reporter: Dan Williams <dcbw>
Component: NetworkManagerAssignee: Dan Williams <dcbw>
Status: CLOSED DUPLICATE QA Contact: Desktop QE <desktop-qa-list>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.2CC: jklimes, tpelka, vbenes
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2011-10-24 08:01:31 UTC Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Flags
Fix signal quality handling with mac80211-based drivers none

Description Dan Williams 2011-10-21 23:19:23 UTC 
Loading up latest RHEL 6.2 nightly, all APs show 100% signal even if they are really far away.  This appears to be due to how mac80211 kernel wifi drivers return signal levels, which isn't something NM handled.  NM hasn't changed code here, so I can only suspect that the kernel changed.  My configuration is:

NetworkManager-0.8.1-14.el6.i686
kernel-2.6.32-211.el6.i686
Intel 5150 WiFi card (iwlagn)

Many mac80211 drivers return signal quality in dBm but use a slightly different way of reporting it, which NM was interpreting as RSSI (instead of dBm).  We need to update NM to look for the IW_QUAL_DBM flag, which mac80211-capable drivers will set to indicate that their signal levels are explicitly in dBm.
Comment 1 Dan Williams 2011-10-21 23:20:39 UTC 
This is only one piece of hardware that shows this issue; we'd do well to get testing on a wider variety of hardware.  We should test at least Intel 4965 and 6000-based cards, an Atheros ath5k card, and some Ralink or Realtek cards too to see if this kernel change affects those devices too.
Comment 3 Dan Williams 2011-10-22 00:16:47 UTC 
Created attachment 529577 [details]
Fix signal quality handling with mac80211-based drivers

This patch produces reasonable signal levels with the cards I have available on my RHEL6 system, which include the airo, zd1211, iwlagn, ath5k.  We should test with Intel 3945/4965, ath9k,and Broadcom cards too though.
Comment 4 Dan Williams 2011-10-23 21:16:06 UTC 
So the reason this bug is appearing is because wpa_supplicant will now use nl80211 instead of WEXT for talking to many kernel drivers (to fix some roaming issues), and the supplicant's nl80211 code doesn't provide a 'qual' item for scan results, just a 'level'.  But that 'level' was encoded in dBm, and NetworkManager wasn't looking for the IW_QUAL_DBM flag to handle the 'level' item correctly.  This didn't used to be a problem, because the WEXT code in the supplicant does provide both 'level' and 'qual', but now that we're using the nl80211 stuff we don't get the 'qual'.
Comment 5 Vladimir Benes 2011-10-24 08:01:31 UTC 

*** This bug has been marked as a duplicate of bug 743555 ***