Interesting issues with CCMP

James Woo jaws
Fri Sep 24 16:28:30 PDT 2004

On Thu, Sep 16, 2004 at 07:36:25PM -0700, Jouni Malinen wrote:
>/ What kind of device do you use as the AP?
/It is a Linksys WAP54g.


Kyle & Jouni,

It's a Linksys WAP54g bug. It's not clearing the PwrMgt bit (bit 12) when constructing
the AAD. You're losing your multicast packets when PwrMgt bit is set. To become bug-compatible,
change line 818 in hostap_crypt_ccmp.c from
	aad[3] = pos[1] & 0xc7; to 	aad[3] = pos[1] & 0xe7;
and then your problem should go away.

James Woo

P.S. Linksys WAP54g has similar CCMP problem with fragmentation too.
It's clearing the fragment number when constructing the AAD. To verify the problem, you'll
see no data traffic when fragmentation is enabled (for example, fragmentation = 256).

More information about the Hostap mailing list