netdev - Re: [PATCH net 1/1] netfilter: conntrack: Check offload bit on table dump

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Date:   Sun, 31 Jan 2021 15:18:34 +0200
From:   Roi Dayan <roid@...dia.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
CC:     <netdev@...r.kernel.org>, Paul Blakey <paulb@...dia.com>,
        Oz Shlomo <ozsh@...dia.com>
Subject: Re: [PATCH net 1/1] netfilter: conntrack: Check offload bit on table
 dump



On 2021-01-31 12:01 PM, Roi Dayan wrote:
> 
> 
> On 2021-01-30 2:01 PM, Pablo Neira Ayuso wrote:
>> Hi Roi,
>>
>> On Thu, Jan 28, 2021 at 09:40:52AM +0200, Roi Dayan wrote:
>>> Currently, offloaded flows might be deleted when executing conntrack -L
>>> or cat /proc/net/nf_conntrack while rules being offloaded.
>>> Ct timeout is not maintained for offloaded flows as aging
>>> of offloaded flows are managed by the flow table offload infrastructure.
>>>
>>> Don't do garbage collection for offloaded flows when dumping the
>>> entries.
>>>
>>> Fixes: 90964016e5d3 ("netfilter: nf_conntrack: add IPS_OFFLOAD status 
>>> bit")
>>> Signed-off-by: Roi Dayan <roid@...dia.com>
>>> Reviewed-by: Oz Shlomo <ozsh@...dia.com>
>>> ---
>>>   include/net/netfilter/nf_conntrack.h | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/include/net/netfilter/nf_conntrack.h 
>>> b/include/net/netfilter/nf_conntrack.h
>>> index 439379ca9ffa..87c85109946a 100644
>>> --- a/include/net/netfilter/nf_conntrack.h
>>> +++ b/include/net/netfilter/nf_conntrack.h
>>> @@ -276,7 +276,7 @@ static inline bool nf_ct_is_expired(const struct 
>>> nf_conn *ct)
>>>   static inline bool nf_ct_should_gc(const struct nf_conn *ct)
>>>   {
>>>       return nf_ct_is_expired(ct) && nf_ct_is_confirmed(ct) &&
>>> -           !nf_ct_is_dying(ct);
>>> +           !nf_ct_is_dying(ct) && !test_bit(IPS_OFFLOAD_BIT, 
>>> &ct->status);
>>
>> The gc_worker() calls nf_ct_offload_timeout() if the flow if
>> offloaded, so it extends the timeout to skip the garbage collection.
>>
>> Could you update ctnetlink_dump_table() and ct_seq_show() to extend
>> the timeout if the flow is offloaded?
>>
>> Thanks.
>>
> 
> sure. i'll submit v2.
> thanks


Hi Pablo,

We did more tests with just updating the timeout in the 2 callers
and it's not enough. We reproduce the issue of rules being timed
out just now frim different place.
There is a 3rd caller nf_ct_gc_expired() which being called by 3
other callers:
____nf_conntrack_find()
nf_conntrack_tuple_taken()
early_drop_list()

only early_drop_list() has a check to skip conns with offload bit
but without extending the timeout.
I didnt do a dump but the issue could be from the other 2 calls.

With current commit as is I didn't need to check more callers as I made
sure all callers will skip the non-offload gc.
Instead of updating more callers and there might be more callers
later why current commit is not enough?
We skip offloaded flows and soon gc_worker() will hit and will update
the timeout anyway.

Thanks,
Roi