wpa_supplicant and dhclient

[Urs Thuermann <urs@isnogud.escape.de>]

I want to connect an embeded mobile WLAN station to a WLAN network
with WPA-PSK and DHCP.  In /etc/network/interfaces I have

    auto ath0
    iface ath0 inet dhcp
        wpa-driver wext
        wpa-conf /etc/wpa_supplicant/ww.conf

My problem is when I boot while the WLAN is not available.  Then ifup
automatically starts wpa_supplicant and dhclient to set up the
interface.  But dhclient will not be able to get a configuration by
DHCP and waits for a number of intervalls which causes quite a long
delay in boot time.  Then ifup returns and the boot process continues,
while wpa_supplicant and dhclient continue to work in the background.

The second problem is this: When at some time the WLAN becomes
available, wpa_supplicant will establish the connection to the access
point but it doesn't inform dhclient to send a new DHCP request
immediately.  Instead, dhclient sends it DHCP request in very long,
randomized intervalls, so it can take very long (like 20 or 30
minutes) until the interface is configured from the time the WLAN
becomes available.

Therefore, my questions are:

1. Is it possible to configure ifup so that it goes to backgound
   immediately so that the boot process isn't delayed?

2. Can wpa_supplicant and dhclient talk to each other so that dhclient
   doesn't start to send DHCP requests before the WPA connection is
   established but then after connection sends its requests in short
   intervalls?

urs