dynamic calculation of event message size for ctnetlin

Index: net-next-2.6.git/net/netfilter/nf_conntrack_netlink.c
===================================================================
@@ -402,6 +402,127 @@ nla_put_failure:
 }
 
 #ifdef CONFIG_NF_CONNTRACK_EVENTS
+static inline size_t calculate_tuple_room_size(const struct nf_conn *ct)
+{
+	size_t size = nla_total_size(0);		/* CTA_TUPLE_XYZ */
+
+	size += nla_total_size(0);			/* CTA_TUPLE_IP */
+	switch(nf_ct_l3num(ct)) {
+	case AF_INET:
+		size += nla_total_size(sizeof(u_int32_t))*2;
+		break;
+	case AF_INET6:
+		size += nla_total_size(sizeof(u_int32_t)*4)*2;
+		break;
+	}
+
+	size += nla_total_size(0);			/* CTA_TUPLE_PROTO */
+	size += nla_total_size(sizeof(u_int8_t));	/* CTA_PROTONUM */
+	switch(nf_ct_protonum(ct)) {
+	case IPPROTO_TCP:
+	case IPPROTO_UDP:
+	case IPPROTO_UDPLITE:
+	case IPPROTO_DCCP:
+	case IPPROTO_SCTP:
+		size += nla_total_size(sizeof(u_int16_t))*2;
+		break;
+	case IPPROTO_ICMP:
+	case IPPROTO_ICMPV6:
+		size += nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(u_int16_t));
+		break;
+	}
+
+	return size;
+}
+
+static inline size_t calculate_protoinfo_room_size(const struct nf_conn *ct)
+{
+	size_t size = 0;
+
+	switch(nf_ct_protonum(ct)) {
+	case IPPROTO_TCP:
+		size += nla_total_size(0)*2 +		/* CTA_PROTOINFO */
+			nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(struct nf_ct_tcp_flags)) +
+			nla_total_size(sizeof(struct nf_ct_tcp_flags));
+		break;
+	case IPPROTO_SCTP:
+		size += nla_total_size(0)*2 +		/* CTA_PROTOINFO */
+			nla_total_size(sizeof(u_int8_t)) +
+			nla_total_size(sizeof(u_int32_t)) +
+			nla_total_size(sizeof(u_int32_t));
+		break;
+	case IPPROTO_DCCP:
+		size += nla_total_size(0)*2 +		/* CTA_PROTOINFO */
+			nla_total_size(sizeof(u_int8_t));
+		break;
+	}
+	return size;
+}
+
+static inline size_t calculate_helper_room_size(const struct nf_conn *ct)
+{
+	const struct nf_conn_help *help = nfct_help(ct);
+	struct nf_conntrack_helper *helper;
+	size_t size = 0;
+
+	if (!help)
+		goto out;
+
+	rcu_read_lock();
+	helper = rcu_dereference(help->helper);
+	if (!helper)
+		goto out_unlock;
+
+	size += nla_total_size(0) + 			/* CTA_HELP */
+		nla_total_size(strlen(helper->name));
+out_unlock:
+	rcu_read_unlock();
+out:
+	return size;
+}
+
+static inline size_t
+ctnetlink_calculate_room_size(const struct nf_conn *ct, unsigned long events)
+{
+	size_t size = NLMSG_SPACE(sizeof(struct nfgenmsg));
+
+	size += calculate_tuple_room_size(ct) * 2 +  /* original and reply */
+		nla_total_size(sizeof(u_int32_t)) +  /* status */
+		nla_total_size(sizeof(u_int32_t));   /* id */
+
+#ifdef CONFIG_NF_CONNTRACK_MARK
+	if (events & IPCT_MARK || ct->mark)
+		size += nla_total_size(sizeof(u_int32_t));
+#endif
+
+	if (events & IPCT_DESTROY || (events & IPCT_COUNTER_FILLING)) {
+		size += nla_total_size(0) * 2 +
+			nla_total_size(sizeof(u_int32_t)) * 2 * 2;
+		return size;
+	}
+
+	size += nla_total_size(sizeof(u_int32_t));	/* CTA_TIMEOUT */
+	if (events & IPCT_PROTOINFO) {
+		size += calculate_protoinfo_room_size(ct);
+	}if (events & IPCT_HELPER || nfct_help(ct))
+		size += calculate_helper_room_size(ct);
+	if (events & IPCT_RELATED)
+		size += calculate_tuple_room_size(ct->master);
+	if (events & IPCT_NATSEQADJ)
+		size += nla_total_size(0) * 2 +
+			nla_total_size(sizeof(u_int32_t)) * 3 * 2;
+#ifdef CONFIG_NF_CONNTRACK_SECMARK
+	if (events & IPCT_SECMARK || ct->secmark)
+		size += nla_total_size(sizeof(u_int32_t));
+#endif
+	return size;
+}
+
 static int ctnetlink_conntrack_event(struct notifier_block *this,
 				     unsigned long events, void *ptr)
 {

@@ -435,7 +556,7 @@ static int ctnetlink_conntrack_event(str
 	if (!nfnetlink_has_listeners(group))
 		return NOTIFY_DONE;
 
-	skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
+	skb = alloc_skb(ctnetlink_calculate_room_size(ct, events), GFP_ATOMIC);
 	if (!skb)
 		return NOTIFY_DONE;