抓包前使用iw命令创建一个监听模式（monitor)的接口
iw phy phy0 interface add mon0 type monitor
tcpdum抓包命令：
tcpdump -nei mon0 type WLAN_TYPE subtype SUB_WLAN_TYPE
WLAN_TYPE的可选值为：management(mgt) | control(ctl) | data
mgt对应的可选的SUB_WLAN_TYPE为：assoc-req, assoc-resp, reassoc-req, reassoc-resp, probe-req, probe-resp, beacon, atim, disassoc, auth， deauth
ctl对应的可选的SUB_WLAN_TYPE为： ps-poll, rts, cts, ack, cf-end, cf-end-ack
data对应的可选SUB_WLAN_TYPE为： data, data-cf-ack, data-cf-poll, data-cf-ack-poll, null, cf-ack, cf-poll, cf-ack-poll, qos-data, qos-data-cf-ack, qos-data-cf-poll, qos-data-cf-ack-poll, qos, qos-cf-poll, qos-cf-ack-poll
源自man pcap-filter