[maemo-developers] Custom kernel - WLAN problem (sk_buff, panic)

[From: Nils Faerber]

Hello!

I've been trying to add additional features to the N800's kernel which
change the size (and contents) of the sk_buff struct
(include/linux/skbuff.h). In short, I want to mark some network packages
and add some information about them.

The problem is that the sk_buff struct is shared by both the open and
closed source part of the cx3110x WLAN driver. While I can recompile the
open source part, I can't change the struct for the closed source part
(umac.ko). When I try to access WLAN on my custom kernel it instantly
crashes with a kernel panic.

If you want to see the effect, just enable CONFIG_NETWORK_SECMARK in
your kernel .config. This adds an __u32 secmark to the sk_buff struct,
thus changes it and introduces the incompatibility. This may lead to a
watchdog reset loop, so please don't try this without knowing how to
restore your original kernel.

If anybody has an idea how to fix this, please let me know. If someone
with access to the full source of the WLAN driver could recompile the
real umac.ko for me, I'd send him/her the modified skbuff.h.

Any hint is very much appreciated...
Thanks a lot!

Cheers
  nils faerber

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