unsigned int FirewallExtensionHook (const struct nf_hook_ops *ops, struct sk_buff *skb, const struct net_device *in, const struct net_device *out, int (*okfn)(struct sk_buff *))
{
    struct tcphdr *tcp;
    struct tcphdr _tcph;
    struct mm_struct *mm;
    struct sock *sk;
    struct path path;
    pid_t mod_pid;
    struct dentry *procDentry;
    char cmdlineFile[BUFFERSIZE];
    int res;
    char* fullpath;
    char pathBuffer[BUFFERSIZE];

    sk = skb->sk;
    if (!sk)
    {
        printk (KERN_INFO "firewall: netfilter called with empty socket!\n");;
        return NF_ACCEPT;
    }

    if (sk->sk_protocol != IPPROTO_TCP)
    {
        printk (KERN_INFO "firewall: netfilter called with non-TCP-packet.\n");
        return NF_ACCEPT;
    }

    tcp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(struct tcphdr), &_tcph);
    if (!tcp)
    {
        printk (KERN_INFO "Could not get tcp-header!\n");
        return NF_ACCEPT;
    }
    if (tcp->syn)
    {
        struct iphdr *ip;

        printk (KERN_INFO "firewall: Starting connection \n");
        ip = ip_hdr (skb);
        if (!ip)
        {
            printk (KERN_INFO "firewall: Cannot get IP header!\n!");
        }
        else
        {
            printk (KERN_INFO "firewall: Destination address = %u.%u.%u.%u\n", NIPQUAD(ip->daddr));
        }
        printk (KERN_INFO "firewall: destination port = %d\n", htons(tcp->dest));



        if (in_irq() || in_softirq() || !(mm = get_task_mm(current)))
        {
            printk (KERN_INFO "Not in user context - retry packet\n");
            return NF_DROP;
        }
        mmput (mm); /* decrease counter controlling access to memory mapping tables */

        if (htons (tcp->dest) == 80)
        {
            tcp_done (sk); /* terminate connection immediately */
            return NF_DROP;
        }
    }

    mod_pid = current->pid;
    snprintf (cmdlineFile, BUFFERSIZE, "/proc/%d/exe", mod_pid);
    res = kern_path (cmdlineFile, LOOKUP_FOLLOW, &path);

    if (res)
    {
        printk (KERN_INFO "Could not get dentry for %s!\n", cmdlineFile);
        return -EFAULT;
    }

    procDentry = path.dentry;
    fullpath = dentry_path_raw (procDentry, pathBuffer, BUFFERSIZE);

    if(canAccess(htons (tcp->dest), fullpath))
    {
        printk (KERN_INFO "Access allowed for %s on %i", fullpath, htons (tcp->dest));
        return NF_ACCEPT;
    }
    else
    {
        printk (KERN_INFO "Access denied for %s on %i", fullpath, htons (tcp->dest));
        return NF_DROP;
    }
}