register an hook

register an hook

[Nicola Padovano]

hi all.
i've read how to register an hook in netfilter. and i found two ways.

the first uses, this routines:


 unsigned int my_hook(unsigned int hooknum,
                      struct sk_buff *skb,
                      const struct net_device *in,
                      const struct net_device *out,
                      int (*okfn)(struct sk_buff *))
 {
 }

int nf_register_hook(struct nf_hook_ops *reg)
int nf_unregister_hook(struct nf_hook_ops *reg)

the second instead:

static unsigned int xt_tarpit_target(struct sk_buff *skb,
				     const struct xt_target_param *par)

and:
xt_register_target(&xt_tarpit_reg);
xt_unregister_target(&xt_tarpit_reg);


which is the difference?

thank you!

Re: register an hook

[Jan Engelhardt]

On Friday 2010-04-23 10:55, Nicola Padovano wrote:

>hi all.
>i've read how to register an hook in netfilter. and i found two ways.
>
>the first uses, this routines:
>
>
> unsigned int my_hook(unsigned int hooknum,
>                      struct sk_buff *skb,
>                      const struct net_device *in,
>                      const struct net_device *out,
>                      int (*okfn)(struct sk_buff *))
> {
> }
>
>int nf_register_hook(struct nf_hook_ops *reg)
>int nf_unregister_hook(struct nf_hook_ops *reg)
>
>the second instead:
>
>static unsigned int xt_tarpit_target(struct sk_buff *skb,
>				     const struct xt_target_param *par)
>
>and:
>xt_register_target(&xt_tarpit_reg);
>xt_unregister_target(&xt_tarpit_reg);
>
>
>which is the difference?

That a target is not a hook.

Re: register an hook

[Nicola Padovano]

what's the difference? what is a target?
I'm analyzing the tarpit patch
(http://enterprise.bih.harvard.edu/pub/tarpit-updates/tarpit-2.6.29.patch)
and i've found only the registration of that target. and so, how it
works, if there isn't an hook registration?

help me, please :(


On Fri, Apr 23, 2010 at 12:27 PM, Jan Engelhardt <jengelh@medozas.de> wrote:
> On Friday 2010-04-23 10:55, Nicola Padovano wrote:
>
>>hi all.
>>i've read how to register an hook in netfilter. and i found two ways.
>>
>>the first uses, this routines:
>>
>>
>> unsigned int my_hook(unsigned int hooknum,
>>                      struct sk_buff *skb,
>>                      const struct net_device *in,
>>                      const struct net_device *out,
>>                      int (*okfn)(struct sk_buff *))
>> {
>> }
>>
>>int nf_register_hook(struct nf_hook_ops *reg)
>>int nf_unregister_hook(struct nf_hook_ops *reg)
>>
>>the second instead:
>>
>>static unsigned int xt_tarpit_target(struct sk_buff *skb,
>>                                    const struct xt_target_param *par)
>>
>>and:
>>xt_register_target(&xt_tarpit_reg);
>>xt_unregister_target(&xt_tarpit_reg);
>>
>>
>>which is the difference?
>
> That a target is not a hook.
>



-- 
Nicola Padovano
e-mail: nicola.padovano@gmail.com
web: http://npadov.blogspot.com/
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Re: register an hook

[Jan Engelhardt]

On Friday 2010-04-23 12:50, Nicola Padovano wrote:

>what's the difference? what is a target?
>I'm analyzing the tarpit patch
>(http://enterprise.bih.harvard.edu/pub/tarpit-updates/tarpit-2.6.29.patch)
>and i've found only the registration of that target. and so, how it
>works, if there isn't an hook registration?
>
>help me, please :(

Targets are invoked via Xtables which is a hook user.

targets: http://en.wikipedia.org/wiki/Iptables
tarpit: http://xtables-addons.sf.net/
and subsequently: http://jengelh.medozas.de/documents/Netfilter_Modules.pdf

Re: register an hook

[Nicola Padovano]

ok jan, thank you! i'm sorry but i'm a very newbie in this field.
anyway i've have some questions.

first of all: if i program a new target i don't have interest in the
management of the hooks? is it right? and why?

second question: when the checkentry function is used?

thank you again :)

On Fri, Apr 23, 2010 at 2:25 PM, Jan Engelhardt <jengelh@medozas.de> wrote:
> On Friday 2010-04-23 12:50, Nicola Padovano wrote:
>
>>what's the difference? what is a target?
>>I'm analyzing the tarpit patch
>>(http://enterprise.bih.harvard.edu/pub/tarpit-updates/tarpit-2.6.29.patch)
>>and i've found only the registration of that target. and so, how it
>>works, if there isn't an hook registration?
>>
>>help me, please :(
>
> Targets are invoked via Xtables which is a hook user.
>
> targets: http://en.wikipedia.org/wiki/Iptables
> tarpit: http://xtables-addons.sf.net/
> and subsequently: http://jengelh.medozas.de/documents/Netfilter_Modules.pdf
>



-- 
Nicola Padovano
e-mail: nicola.padovano@gmail.com
web: http://npadov.blogspot.com/