Monitor interface added to Master interface

[Johannes Berg]

On Tue, 2011-03-29 at 18:02 -0700, Lara Deek wrote:

> 
> I am running tcpdump on a monitor interface. The issue that I am
> facing is that the monitor interface that is added to the master (AP
> mode) interface by running hostapd does not report SNR on beacon
> messages, and does not receive packets destined to the master
> interface. However, a monitor interface added to a managed mode
> interface (not using hostapd) reports packet SNR and captures packets
> destined to the managed interface.
> 
> 
> Is there a reason for this difference? How is the monitor interface
> created/setup by hostapd, and is it not setting the interface to
> promiscuous mode? 

To reduce CPU usage, hostapd creates the interface in "cooked" mode,
where the kernel will report only frames that are not handled in the
kernel already.

johannes