Very Strange Problem With NAT in UDP

[francescpages]

Hello, today I've seen a big problem with NAT in PFSENSE 2.0.3. My pfsense had a complex configuration but I'm sure that problem will exist in any kind of PFSENSE in these release.

The problem is about NAT and UDP traffic

1 WAN IP 192.168.100.2
1 LAN IP 192.168.22.1

In NAT I put all traffic with ip destination 192.168.100.2 udp port 6000 –> redirect to 192.168.22.2, I put also in firewall rule a log

If I try outside this rule. It works good. But I encountered one situation that it not works:

If are inside (192.168.22.2) and outside (192.168.100.1)with a with a udp program:
sent udp datagram from 192.168.22.2 udpsrc=6000 to 192.168.100.1 udpdst=3710
and with less than 5 secons you send another udp datagram from 192.168.100.1 udpdst=3710 to 192.168.22.2 udpsrc=6000 then the second datagram is logged in firewall with pass but router doens't do the NAT(datagram is not leavin out from LAN nic) (I don't understand why??????)

I tried a lot of things and I can explain that:

If you did the same but the answer from 192.168.100.1 is from another udpsrc diferent that form I request before then the nat rule logs and works correctly.

If you wait some time before answer (not answer in few seconds), then with the same datagram and ports it works.

Thanks a lot