(Cc'ing netdev and netfilter-devel lists)
On Wed, Feb 11, 2015 at 10:31 AM, Chris Vine
<chris@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, 11 Feb 2015 09:28:34 +0000
> Chris Vine <chris@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> With kernel 3.19.0, the following iptables rule, where SSH_TRIES is
>> set to 4:
>>
>> iptables -D SSH_CHAIN -m conntrack --ctstate NEW \
>> -m recent --update --seconds $SSH_LOGIN_PERIOD --hitcount
>> $SSH_TRIES -j DROP
>>
>> generates this error message in syslog:
>>
>> kernel: xt_recent: hitcount (4) is larger than packets to be
>> remembered (4) for table DEFAULT
>>
>> and the rule fails to install in the table. No error is generated
>> with kernel 3.18.6.
>
> The rule provoking this should of course have been the one appending
> the rule, which is:
>
> iptables -A SSH_CHAIN -m conntrack --ctstate NEW \
> -m recent --update --seconds $SSH_LOGIN_PERIOD --hitcount $SSH_TRIES -j DROP
>
> On looking at the code, the changes in the 3.19 kernel seem not to have
> been tested and there is an off-by-one error. The patch below restores
> behaviour to be identical to that found in the 3.18 kernel.
>
> Chris
>
> --- linux-3.19.0/net/netfilter/xt_recent.c~ 2015-02-10 09:18:44.657376355 +0000
> +++ linux-3.19.0/net/netfilter/xt_recent.c 2015-02-11 17:58:33.311608835 +0000
> @@ -378,7 +378,7 @@
> mutex_lock(&recent_mutex);
> t = recent_table_lookup(recent_net, info->name);
> if (t != NULL) {
> - if (info->hit_count > t->nstamps_max_mask) {
> + if (info->hit_count > t->nstamps_max_mask + 1) {
> pr_info("hitcount (%u) is larger than packets to be remembered (%u) for table %s\n",
> info->hit_count, t->nstamps_max_mask + 1,
> info->name);
> --
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