Re: NFQUEUE verdicts - adding non-termination

[Patrick McHardy <kaber@trash.net>]

On 12.11.2010 12:11, Patrick McHardy wrote:
> Am 12.11.2010 12:01, schrieb Andrew Watts:
>> --- On Thu, 11/11/10, Patrick McHardy <kaber@trash.net> wrote:
>>
>>> On 11.11.2010 10:01, Andrew Watts wrote:
>>>> Hi.
>>>>
>>>> The NF_CONTINUE verdict that Darryl Miles brings up in his 11/4
>>>> post is very interesting. NF_CONTINUE would provide the NFQUEUE
>>>> target the added flexibility of, say, partial handling in
>>>> userspace. A queue-handler could have a set of criteria that,
>>>> when satisfied, would result in an immediate drop or accept. One
>>>> could then leave the rest of the packets to find their fate in the
>>>> chains/rules left to traverse. I would be interested in helping
>>>> to add this verdict if someone will take the lead (assuming a patch
>>>> hasn't already been written - has it?).
>>
>>> There's no difference between returning NF_ACCEPT or a new NF_CONTINUE.
>>> Queueing happens outside of the ruleset context, so in either case the
>>> packet would continue through the network stack directly, not after
>>> the NFQUEUE rule.
>>
>> I see. Is there a way to achieve this result under the current
>> infrastructure?
> 
> Having the packet continue after the NFQUEUE rule? No, once the packet
> is reinjected, that rule might not even be there anymore.

Actually, what you can do is use NF_REPEAT as verdict and have the
packet continue at the next rule based on marks. Something like this:

Chain INPUT:
-m mark --mark 0 -j NOT_QUEUED
-m mark --mark 1 -j BACK_FROM_QUEUE

Chain NOT_QUEUED:
... rules ...
-j NFQUEUE

[ nfqueue: return NF_REPEAT, set mark = 1 ]

Chain BACK_FROM_QUEUE:
... further rules ...