Re: [B.A.T.M.A.N.] [PATCH] [batman] Add padding around allocation debugger structures

[Nathan Wharton <naw@greptar.com>]

On Mon, Jun 1, 2009 at 2:35 PM, Sven Eckelmann <sven.eckelmann@gmx.de> wrote:
> Ok, I think I see the problem. The malloc returned a valid aligned adress.
> list_add_tail will get a pointer to an element in hna_global_entry. This
> structure is packed and all operations on it should be non-alignment safe. If
> you look at it further you will notice that orig_list is at position 9
> (assuming 4 bytes for a pointer) - which will not be aligned to 4 bytes of
> course.....
> And here comes the problem: the compiler will only do the safe operations on
> non-aligned data if it knows that it is not alignent. Since a cast is done by
> calling list_add_tail it will not know that this parameter is not aligned and
> the non-alignment bug will occur.
>
> So my question to marek: Is it really needed to have "struct hna_global_entry"
> packed in hna.h:57? If not then we should remove it and this problem should be
> gone. And what is with "struct hna_element".
>
> Thank you for your work, Nathan :)

You are welcome, thanks for your help.

The crashing of batgat on unloading turns out to be socket 4306 not
being ready to be reused yet.
I worked around this by using:
batmand -c -r 0 ; sleep 1 ; batmand -c -g 11000
and
batmand -c -g 0 ; sleep 1 ; batmand -c -r 2

Marek helped figure that out on irc.