Bug 690244

Summary:	Can't monitor 802.11n IP traffic for RT3070 devices in monitor mode
Product:	[Fedora] Fedora	Reporter:	Martin <martind1111>
Component:	kernel	Assignee:	John W. Linville <linville>
Status:	CLOSED NOTABUG	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	high	Docs Contact:
Priority:	unspecified
Version:	15	CC:	gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-03-29 17:07:24 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description Martin 2011-03-23 17:09:47 UTC

It is not possible to monitor 802.11n IP traffic for RT3070 based devices when interface is set to monitor mode in Fedora 15 Alpha. 802.11b and 802.11g traffic can be monitored.

Tested with kernel release 2.6.38-1.fc15.i686


How reproducible:


Steps to Reproduce:
1. Insert a RT3070 device in a system running Fedora 15 Alpha
2. ifconfig -a (to determine if device is present and the interface name assigned to this device - asssume here interface is wlan1)
3. ifconfig wlan1 down
4. iwconfig wlan1 mode monitor
5. iwconfig wlan1 channel 1
6. ifconfig wlan1 up
7. tcpdump -i wlan1 ip
  
Actual results:

No traffic is reported.

Expected results:

IP traffic should be reported by tcpdump


Additional info:

Tested on lenovo ThinkPad T61p

Comment 1 John W. Linville 2011-03-28 19:09:38 UTC

The iwconfig tool is old and ignorant of 802.11n.  I would advise the following sequence:

ifconfig wlan1 down
iw dev wlan1 set monitor none
iw dev wlan1 set channel 1 HT20
ifcofnig wlan1 up
tcpdump -i wlan1

I'm not sure that the ip filter is appropriate for tcpdump for a wireless device in monitor mode, but YMMV...

Does this give you output from tcpdump?  It is possible that the driver needs something more as well.

Comment 2 Martin 2011-03-28 20:35:20 UTC

With the "iw dev" commands listed in the previous comment, I am now able to get 802.11n traffic with a RT3070 device. Note that with an Intel IWP4965 device and a number of other devices (Atheros 9170, RT2870), it is possible to capture 802.11n traffic in monitor mode using the iwconfig commands. I am not sure why the same commands do not work for the RT3070 chipset, but it is good to know there is a workaround.

Comment 3 John W. Linville 2011-03-29 17:07:24 UTC

I'm glad it's working for you.  But, it isn't a workaround -- it is how things work.  In fact, if you use the older tools (e.g. iwconfig) then the command that comes to the driver to change the channel actually specifies _not_ to do HT (i.e. 802.11n).

So, you could argue that if it works for the other devices you cite then it is a bug in _those_ drivers.  But, more likely it is just an artifact of how that other hardware works.  I think we'll let it slide... :-)

Anyway, it seems that your issue is resolved.  Closing on the basis of comment 2.