I'm about to learn something of kernel module programming. I found a cool article on phrack61 about the network-stack of Linux, so I started out coding... however, i fail to compile my second module - here are the relevant lines:

static const __u32 deny_ip1 = 0x2171e4d8; (Globally defined)

if(sb->nh.iph->daddr == deny_ip1) <- compiling fails here.
return NF_DROP;

The Error-message I get from gcc is:

/home/benjamin/programming/net.c:17: error: dereferencing pointer to incomplete type

daddr is of type __u32.
Ah, I forgot one thing: I'm compiling this on a amd64 operating in 64-bit mode - so sizeof(void*) is 8 bytes.

Any help is welcome.

You haven't #include'd the definition of one of the structs you dereference in that line. So either sb, sb->nh, or sb->nh.iph is of a type unknown to the compiler.

Depending on what kernel version you're doing this for, you might need to #define __KERNEL__ or __MODULE__ before #include'ing the relevant header to get the definition.

Ahhh... why am I this stupid...

#include <linux/ip.h>
and it all compiles fine :/

Well, thanks anyway