Re: [PATCH 1/1 ] Conntrack extensions : Interrupt timeout

["James King" <t.james.king@gmail.com>]

On Wed, Dec 17, 2008 at 12:22 PM, Piotr Duszynski <regis44@gmail.com> wrote:
> I wanted to write a module that would track all the MAC information for
> all established connections. Unfortunately, after the module is loaded
> and all the information is being properly recorded to the conntrack
> computer hangs . I can read that it is related with interrupt timeout,
> but after several hours of trying to fix this I am still in the same
> spot . I would really appreciate any guidance in this matter .
>
> +               l2info = nfct_l2info(ct);
> +               if (!l2info) {
> +                       printk(KERN_INFO "Adding L2INFO extension\n");
> +                       l2info = nf_ct_ext_add(ct, NF_CT_EXT_L2INFO,GFP_ATOMIC);

You shouldn't call nf_ct_ext_add from within your target, as your
private structure needs to be added before the conntrack is confirmed
(preferably at allocation time).  From _nf_ct_ext_add() in
nf_conntrack_extend.c:

 /* Conntrack must not be confirmed to avoid races on reallocation. */
NF_CT_ASSERT(!nf_ct_is_confirmed(ct));

Take a look at init_conntrack() in nf_conntrack_core.c to see how
nf_conntrack_acct does it.  lxr.linux.no is your friend :)

HTH,
James