Hello, I put his question to netfilter-devel, but did get no reply. I'm just wondering if my problem is too trivial or impossible with iptables, here it is: I want to write an extended logging of TCP-Connections: iptables -A INPUT -j LOGTCP LOGTCP should just be a copy of ipt_LOG.c: /* --------copy------------ static void dump_packet(const struct ipt_log_info *info, const struct sk_buff *skb, unsigned int iphoff) { ... case IPPROTO_TCP: { struct tcphdr _tcph, *th; /* Max length: 10 "PROTO=TCP " */ printk("PROTO=TCP "); ... [*] ... break; --------copy------------ /* And here [*] I want to call some functions from tcp_conntrack: printk("tcp_in_window, sender->td_end, sender->td_maxend, sender->maxwin, receiver->td_end, receiver->td_maxend, receiver->td_maxwin); The problem: I just don't know how to access these values from there. ip_conntrack_get gives me a pointer to nowhere. I looked through several other modules, but didn't find the idea to get started.