wtap(4): support hostap/sta mode and WPA/WPA2

Wtap originally only supported mesh/ad-hoc mode, and cannot be combined with wpa_supplicant(8)
and hostapd(8) since it's unaware of encryption/decryption. Now I have supported hostap and sta mode
with WPA/WPA2, thus now wtap(4) can be used with hostapd(8) and wpa_supplicant(8).

There is a problem when combining wtap(4) with wpa_supplicant(8):
A race between net80211's scan request and wpa_supplicant's scan request which
all of the net80211(4) drivers will face. D38753 introduces the problem, and D38807 fixes the problem with
only real world NIC, wtap(4) still fails because ic->ic_parent() finish too quick (more details
can be found in D38508). I have solved this problem by making wtap(4) sleep for a while in
ic->ic_parent(). Now wtap(4) supports wpa_supplicant(8) and hostapd(8) well.

This patch depends on D37973 and D38807.

create wtap devices

wtapctl device create 0
wtapctl device create 1

add links in visibility tool

wtapctl vis open
wtapctl vis add 0 1
wtapctl vis add 1 0

create vaps

ifconfig wlan0 create wlandev wtap0 wlanmode hostap ssid test
ifconfig wlan1 create wlandev wtap1 wlanmode sta ssid test

run hostapd on wlan0

hostapd -i wlan0 hostapd.conf

Here is the hostapd.conf for example:

interface=wlan0
debug=1
ctrl_interface=/var/run/hostapd
ctrl_interface_group=wheel
ssid=test
wpa=2
wpa_passphrase=12345678
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP

run wpa_supplicant on wlan1

wpa_supplicant -i wlan1 -dd -c wpa.conf

Here is the wpa.conf for example:

network={
	ssid="test"
	psk=fe727aa8b64ac9b3f54c72432da14faed933ea511ecab15bbc6c52e7522f709a
}

see connection result

After running wpa_supplicant, one may check whether wlan1 connects to wlan0 by ifconfig(8):

ifconfig wlan1 | grep bssid

If one wants to do ping test between the two interfaces, he or she may need jail(8) for isolating network stack.