On Sun, May 21, 2017 at 08:59:45AM +0800, Liping Zhang wrote:
> Hi Florian,
>
> 2017-05-21 8:00 GMT+08:00 Florian Westphal <[email protected]>:
> [...]
> > Yes, you're right, seems this was added in
> > 93bb0ceb75be2fdfa9fc0dd1fb522d9ada515d9c (it adds the 'goto out').
>
> I added some trace logs, and when the hash size reduced, for example,
> from 60000 to 500, then the issue would happen.
>
> Actually, hitting 'goto out' is not easy, so the issue exists for a very long
> time. Maybe commit 89f2e21883b5("[NETFILTER]: ctnetlink: change
> table dumping not to require an unique ID") is to blame for it.
>
> > Your patch looks correct.
> >
> > However, why do we bump refcnt of 'last' in the first place?
> >
> > Its only the continuation marker, i.e. its expected to reside
> > in the hash slot at cb->args[0], but after rehash this might not
> > be true either.
> >
> > I think we should simplify this, just take the verbatim address,
> > and clear it right at start of ctnetlink_dump_table, i.e.
> >
> > unsigned long last = cb->args[1];
> > cb->args[1] = 0;
> >
> > for (; cb->args[0] < nf_conntrack_htable_size; cb->args[0]++) {
> > ...
> > hlist_nulls_for_each_entry ... {
> > ...
> > if (last) {
> > if (last != (unsigned long)ct))
> > cont;
> > last = 0;
> > }
> > ...
> > dump();
> > }
> > last = 0; /* reset it, as it wasn't in args[0] slot */
> > }
> >
> > Do you see any problem with that?
>
> I think this will be better, this will make code more clean.
> Also we can clean up the ctnetlink_exp_ct_dump_table too.
@Florian, no objection then if I place this into nf.git?
I will append the Fixes: tag:
Fixes: 89f2e21883b5 ("[NETFILTER]: ctnetlink: change table dumping not to
require an unique ID")
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