Hello,

I was trying to filter packets.. and installed NF_IP_PRE_ROUTING & NF_IP_POST_ROUTING.


// input hook
input_filter.list.next = NULL;
input_filter.list.prev = NULL;
input_filter.hook = input_handler;
input_filter.pf = PF_INET; // IPv4
input_filter.hooknum = NF_IP_PRE_ROUTING;

// output hook
output_filter.list.next = NULL;
output_filter.list.prev = NULL;
output_filter.hook = output_handler;
output_filter.pf = PF_INET; // IPv4
output_filter.hooknum = NF_IP_POST_ROUTING;


result = nf_register_hook(&output_filter);

result = nf_register_hook(&input_filter);

then, other machine sends a packet to this machine, packet is not received at application.

However, I can see the packet is filtered at NF_IP_PRE_ROUTING. I do not touch anything in the packet and just return NF_ACCEPT, like below.

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

I guess packet is dropped between NF_IP_PRE_ROUTING and application.

Does anybody have any clues...

Thanks in advance.

with regards
AlwaysRookie...