I'm working on an application that should relay udp packets from one host to another according to some rules. It is basically NAT.
I negotiate UDP ports with both hosts and after that I need to receive from host A and send to host B with the negotiated ports.
So i'm dinamically adding and removing
# my address is 10.1.1.1 # A is 10.10.10.10:30590 - 10.1.1.1:36232 # B is 10.20.20.20:30588 - 10.1.1.1:36230 # A to B iptables -t nat -A PREROUTING -s 10.10.10.10/32 -i eth0 -p udp -m udp --sport 30590 -j DNAT --to-destination 10.20.20.20:30588 iptables -t nat -A POSTROUTING -d 10.20.20.20/32 -p udp -m udp --dport 30588 -j SNAT --to-source 10.1.1.1:36232 # B to A iptables -t nat -A PREROUTING -s 10.20.20.20/32 -i eth0 -p udp -m udp --sport 30588 -j DNAT --to-destination 10.10.10.10:30590 iptables -t nat -A POSTROUTING -d 10.10.10.10/32 -p udp -m udp --dport 30590 -j SNAT --to-source 10.1.1.1:36230
And this works most of the time, however, sometimes the first packets start to arrive before the rules are added. Clearing UDP "connections" makes the rules work (
conntrack -D -p udp ).
I've triyed to disable connection tracking using rules like:
iptables -t raw -A PREROUTING -j NOTRACK iptables -t raw -A OUTPUT -j NOTRACK # or iptables -t raw -A PREROUTING -j CT --notrack iptables -t raw -A OUTPUT -j CT --notrack
But none of these seem to work.
Will the only solution be to clear the UDP connection tracking for every stream?
I need to support thousands of concurrent streams, and several being added and removed every second.