I’ve been trying to understand the connection tracking (conntrack) source code (specifically nf_conntrack_proto_tcp.c and nf_conntrack_proto_udp.c) by sending packets between virtual machines and observing the connection states, looking to possibly find vulnerabilities or perhaps weaknesses.

I’ve downloaded the exact version of the kernel my VM is using and added the printk statements in the nf_conntrack_proto_tcp.c and nf_conntrack_proto_udp.c files. However when I try compiling the net/netfilter folder, I’m encountering an error net/netfilter/nfnetlink.ko undefined. How do I fix this and what should be my next steps? I would be sending pings from one machine to another,so I can see which conntrack functions are being executed or which lines are being processed.

I’ve tried compiling the net/netfilter folder, but I’ve been encountering errors.