SKB BUG: Invalid truesize

Jouni Malinen j
Mon Mar 9 02:12:17 PDT 2009

On Mon, Mar 09, 2009 at 02:16:03PM +0800, Sylvain wrote:

> I just reported this bug at Ubuntu:

That bug is about 2.6.20 and was filed almost two years ago.. Are you
sure the issue you are seeing is for the same problem?

> Basically, I often get 'SKB BUG: Invalid truesize' messages in my logs 
> when a client connects to my AP (and subsequently uses the connection). 
> You can see the whole trace in the bug report.

Would it be possible for you to test this with a more recent kernel
version or well, something that is closer to mainline development
kernels. The warning in skbuff.c is from code that does not seem to
exist in the current kernel development tree and as such, may only
interest people who happen to be working with that distro kernel tree.

> So, I am looking for any advice that would help me fix that SKB BUG 
> problem. Probably the first piece of advice that comes to mind is to 
> upgrade to 0.6.8, but I am kind of reluctant to abandon the deb/apt-get 
> convenience. Of course if it is a known fact that 0.6.8 fixes that 
> particular problem I will happily compile it.

The SKB truesize issue should have nothing to do with hostapd, i.e., it
is a kernel side problem. However, since the current wireless-testing
git tree does not seem to have code that would generate such a warning,
it may be more difficult to find people interesting in researching this
with the old/distro version of the kernel.

> Bonus question: the chip is supposed to support draft n, but
> 1/ iw list shows 54.0 Mbps as the highest bitrate

Update iw and you'll get list of supported MCS indexes (0..15) for HT

> 2/ on my eee pc, "iwlist ra0 scan" lists my AP with Bit Rates:118 Mb/s
> Who is right, and what should I do to use the chip at its maximum speed?

It was probably already running at maximum speed. However, you should
probably update hostapd and kernel to the latest development snapshots
to get some of the recent bug fixes for AP mode operations.

Jouni Malinen                                            PGP id EFC895FA

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