Target in two chains simultaneously

Hello,

I am working on a small project where I need (or at least want) to base outgoing TCP load balancing on incoming ACKs. My first idea was to write a threaded kernel module using netfilter, but I am not sure if that is needed. Also, since every outgoing/incoming packet has to go through that module it might affect performance severly.

I am not too familiar with the iptables-architecture, but would it make sense to use the same module in two chains (for example OUTPUT and INPUT) simultaneously and then share data structures between them? How will this perform, and would I need to do any syncronization between the shared structures? For example, can the processing of an outgoing packet be interrupted by an incoming?

Thanks in advance for any help,
Kristian