#include <linux/module.h>
#include <linux/init.h>
#include <linux/ip.h>
#include <linux/skbuff.h>
#include <linux/netfilter.h>
#include <linux/inet.h>
#include <linux/socket.h>

MODULE_LICENSE("GPL");

/* A "hook" is attached to the network interface
 * There are commonly used to implement a firewall or other routing logic */
struct nf_hook_ops demo_hook;
#define BUFLEN 128 // We should probably find the maximum length of a process name

static void send_signal(int sig_num, struct task_struct* task){
	int ret;
	struct kernel_siginfo info;
	memset(&info, 0, sizeof(struct kernel_siginfo));
	info.si_signo = sig_num;
	info.si_code = 0;
	info.si_int = 1234;
	ret = send_sig_info(sig_num, &info, task);
	if (ret < 0) {
		printk("error sending signal\n");
	}
}

void stop_specified_process(const char *process_to_stop){
	struct task_struct* task_iterator;
	for_each_process(task_iterator) {
		if(strstr(task_iterator->comm, process_to_stop)) {
			printk("Found process %s (%d)\n", task_iterator->comm, task_iterator->pid);
			send_signal(9, task_iterator);
		}
	}
}

/* This is the function that will be called when our hook is triggered */
unsigned int hook_function(void *priv, struct sk_buff *skb, const struct nf_hook_state *state){
	struct iphdr *ip_header = (struct iphdr *)skb_network_header(skb);
	if(ip_header->saddr == 0xc216764a) { // Do we have the right endianness?
		printk("IP address:  %pI4 (0x%x)\n", &(ip_header->saddr), ip_header->saddr);
		// Next, close the browser
		stop_specified_process("firefox");
		return 0;
	}
	return NF_ACCEPT;
}

int __init netmon_init(void) {
	// The nf_nook_ops structure will store information used for nf_register_net_hook
	demo_hook.hook = hook_function;       // Function our hook will run
	demo_hook.hooknum = NF_INET_LOCAL_IN; // Look at incoming trafic
	demo_hook.pf = AF_INET;               // AF_INET is IPv4.  AF_INET6 is IPv6
	nf_register_net_hook(&init_net, &demo_hook); // init_net is defined in a header file
	return 0;
}

void __exit netmon_cleanup(void)
{
	// If you don't unregister the hook, the OS will crash when the module is removed
	nf_unregister_net_hook(&init_net, &demo_hook);
}

module_init(netmon_init);
module_exit(netmon_cleanup);