Setup “monitor” mode and disable CRC checking

1. Live Monitoring and Writing Raw 802.11 Packets — From madwifi README

The driver can be used in a live “monitor” mode, by creating a monitor
VAP and sending packets to it. All packets sent to a monitor mode VAP
will bypass any state machine.

To create a monitor VAP, use:

wlanconfig ath1 create wlandev wifi0 wlanmode monitor
ifconfig ath1 up

Finally, you can choose to receive packets on ath1 in several different
packet formats:

echo ’801′ > /proc/sys/net/ath1/dev_type # only 802.11 headers
echo ’802′ > /proc/sys/net/ath1/dev_type # prism2 headers
echo ’803′ > /proc/sys/net/ath1/dev_type # radiotap headers
echo ’804′ > /proc/sys/net/ath1/dev_type # atheros descriptors

2. Disable CRC and PHY error checking

Allows monitor VAPs to process frames that have been marked
as errors by the hardware. Two new sysctl entries are created,
“monitor_crc_errors” and “monitor_phy_errors”. When these are set
to 1, the monitor mode interface will pass through frames that have
been marked with HAL_RXERR_CRC and HAL_RXERR_PHY respectively.
Default is to maintain current behaviour – no rx errors are passed
through.

echo ’1′ > /proc/sys/net/ath1/monitor_crc_errors # Disable CRC error checking

echo ’1′ > /proc/sys/net/ath1/monitor_phy_errors # Disable PHY error checking