[support] wifi interface keeps old CoA even after associating to a new AP advertising a new prefix

[Bokor Laszlo]

Dear All!

During the procedures of setting up a real-life demo we experienced
some interesting problems. (In the tests we move a MR - using umip-0.4
with MCoA patch - between one 3G and two Wifi networks, where the WiFi
networks have the same ESSID and advertise different IPv6 address
spaces).

Our problem is related to the handovers between two WiFi networks
(using the same egress WiFi interface):

During physical movements between the two Wifi coverage areas, when we
watch iwconfig wlan0 (egress interface), we can see that the MR is
associated to one of the APs, then not associated, then it associates
to the second AP (correct behaviour).

However, watching ifconfig wlan0, we see that in the first network it
gets the first CoA, then during the not-associated state it still
holds the first CoA,  and finally when it arrives to the second
network, it gets the new CoA but it still keeps the first CoA and the
BU and other packets can't be sent out and/or received.

The problem is that the wlan0 interface has two addresses. We can
solve manually this issue (without interrupting the correctly running
mip6d) by using either ifconfig wlan0 down and ifconfig wlan0 up, or
by deleting the old CoA address from the wlan0 interface, resulting in
that the MR leaves this strange state. However this behaviour is
probably not the expected one.

(The WiFi egress interface of the MR  is a  Fujitsu-Siemens E-5400 USB
device that works perfectly using ndiswrapper and WlanGUI.inf windows
driver.)

Have anybody experienced such kind of problem?


Br,
goodzi

--
Laszlo Bokor
Research fellow
Budapest University of Technology and Economics
Mobile Innovation Center