On Tue, 2010-02-02 at 13:16 -0500, Jon Masters wrote:

On Tue, 2010-02-02 at 19:58 +0200, Alexey Dobriyan wrote:

quoted

Yes, moving to init_net-only function is fine.

So moving the "setup up fake conntrack" bits to init_init_net from
init_net still results in the panic, which means that the use count
really is dropping to zero and we really are trying to free it when
using multiple namespaces. Per ns is probably an easier way to go.

Just for kicks, I'll have it error out on attempting to free to see if I
can get this box to stay up for a while.

Confirmed. It boots and the hashsize is not inadvertedly corrupted if I
do the following:

void nf_conntrack_destroy(struct nf_conntrack *nfct)
{
        void (*destroy)(struct nf_conntrack *);

        if ((struct nf_conn *)nfct == &nf_conntrack_untracked) {
                printk("JCM: nf_conntrack_destroy: trying to destroy
nf_conntrack_untracked! CONTINUING...\n");
                //panic("JCM: nf_conntrack_destroy: trying to destroy
nf_conntrack_untracked!\n");
                return; /* refuse to free nf_conntrack_untracked */
        }

        rcu_read_lock();
        destroy = rcu_dereference(nf_ct_destroy);
        BUG_ON(destroy == NULL);
        destroy(nfct);
        rcu_read_unlock();
}
EXPORT_SYMBOL(nf_conntrack_destroy);

Clearly that's just a hack (though catching the specific attempt to free
the untracked conntrack sounds like a very good idea in general). I will
leave this running for a while, but so far no problems:

[jcm@perihelion jcm_26]$ dmesg|grep JCM
[   29.952717] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   30.207091] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   30.403248] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   31.403319] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   32.977106] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   33.347100] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   33.966092] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   34.967111] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   35.404323] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   35.911430] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   35.912442] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   38.967061] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   39.403342] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   41.288392] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   42.966063] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   44.036451] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   95.621174] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   95.673061] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   95.741180] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   96.273429] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   96.741296] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   97.246108] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[   98.246486] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  100.747170] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  102.252067] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  104.747066] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  105.762433] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  106.252084] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  147.260998] JCM: nf_conntrack_destroy: trying to destroy
nf_conntrack_untracked! CONTINUING...
[  155.485160] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  156.403661] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  157.402928] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  161.402477] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  163.270622] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  163.277368] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  167.718677] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  176.901877] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  182.554024] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  182.616693] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  183.616932] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  187.617026] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  188.362002] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  191.617001] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  193.574899] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  197.455338] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  214.163491] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  214.311528] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  215.311577] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  219.317496] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  220.693493] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  223.317095] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  240.326198] JCM: nf_conntrack_destroy: trying to destroy
nf_conntrack_untracked! CONTINUING...
[  252.481116] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  252.881087] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  253.881251] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  257.922816] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  258.882989] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  261.413093] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  261.921943] JCM: icmpv6_error: attaching to nf_conntrack_untracked.
[  266.350983] JCM: icmpv6_error: attaching to nf_conntrack_untracked.

So, over to you :)

Jon.