On Thursday 26 Jan 2012, Victor Goldenshtein wrote:

This patch set (with nl/cfg/mac80211 patch series) adds support for DFS
(Dynamic Frequency Selection) according 802.11h.


Main idea
===================

DFS master algorithm is implemented in the hostapd, while nl/cfg/mac80211
will pipe relevant commands/events to the driver/hostapd.

As I understand it hostapd is not involved in mesh (802.11s) networks,
so how does this integrate there?  As I understand it 802.11s is entirely
done in the kernel.

David

Based on the assumption that the device/driver supports radar interference
detection i.e., it is capable to generate radar_detected event by using
different pattern detection techniques:


1. Pattern detection in the HW: the device generates 'radar_detected'
event. 2. Pattern detection in the driver: the driver receives radar
pulses from the device and generates 'radar detected' event.


Main DFS procedures
===================

1. Hostapd gets driver's dfs capabilities.

2. If 80211h is enabled in the hostapd.conf and the driver supports one of
the above radar detection techniques, hostapd may use DFS channels.

3. Hostapd selects an operational channel (default from hostapd.conf), if
selected channel is a DFS channel, hostapd sends start_radar_detection
command to the device/driver which starts monitoring for radar
interference while hostapd sets a timer for a CAC (Channel Availability
Check) time, which is 60 seconds.

4. As CAC timer expires and no radar has been detected, hostapd may
continue with the init flow, otherwise if interference is detected hostapd
selects another channel (random selection) and repeats the CAC on the new
channel (in case the new channel is also a DFS channel), while the
original channel is added to a "black list" for a period of
''No-Occupancy'' time (time that the channel can't be used/selected).

5. While using the channel the device/driver continuously monitors for
potential radar interference. If interference is detected hostapd notified
with 'radar detected' event, which selects a new channel and triggers a
channel switch procedure, if the new channel is also a DFS channel,
hostapd performs the CAC test, once it's successfully passed hostapd
instructs the driver to initiate the transmission on the channel.


Victor Goldenshtein (7):
  hostapd: implement dfs drv ops functions
  hostapd: add channel switch ability
  hostapd: add dfs events
  hostapd: add dfs support into interface init flow
  nl80211: add support to enable TX on oper-channel
  nl80211: add channel switch command/event
  nl80211: add start radar detection command/event

 hostapd/config_file.c        |   10 +++
 src/ap/ap_config.h           |    4 +
 src/ap/ap_drv_ops.c          |   34 +++++++++
 src/ap/ap_drv_ops.h          |    4 +
 src/ap/beacon.c              |   16 ++++
 src/ap/drv_callbacks.c       |   40 +++++++++++
 src/ap/hostapd.c             |  158
++++++++++++++++++++++++++++++++++++++++-- src/ap/hostapd.h             | 
 10 +++
 src/ap/hw_features.c         |   48 ++++++++++---
 src/ap/hw_features.h         |   10 +++
 src/ap/ieee802_11.c          |  116 +++++++++++++++++++++++++++++++
 src/ap/ieee802_11.h          |    4 +
 src/drivers/driver.h         |   87 +++++++++++++++++++++++-
 src/drivers/driver_common.c  |    2 +
 src/drivers/driver_nl80211.c |  125 +++++++++++++++++++++++++++++++++
 src/utils/eloop.c            |    4 +
 src/utils/eloop.h            |    7 ++
 17 files changed, 662 insertions(+), 17 deletions(-)