mrash/fwknop — pull request #15 by fjoncourt (2013-01-17 21:01:43+00:00)
Title: Avoid duplicate rules in the iptables ruleset for the same timestamp

I have played with fwknop on android and it works fine. Here is a part of my
iptables ruleset dump after sending multiple packets

```
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764373 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764374 */
0 0 ACCEPT tcp -- any any 192.168.1.14 \
anywhere tcp dpt:ssh /* _exp_1357764375 */
```
Using the check option (-C) from iptables will allow fwknop to make sure not to insert duplicate rule (same timestamp). However, I do see any way to avoid adding the same access rule with different timestamps.