Tracing a packet journey using Linux tracepoints, perf and eBPF

I’ve been looking for a low level Linux network debugging tool for quite some time. Linux allows to build complex networks running directly on the host, using a combination of virtual interfaces and network namespaces. When something goes wrong, troubleshooting is rather tedious. If this is a L3 routing issue, mtr has a good chance of being of some help. But if this is a lower level issue, I typically end up manually checking each interface / bridge / network namespace / iptables and firing up a couple of tcpdumps as an attempt to get a sense of what’s going on. If you have no prior knowledge of the network setup, this may feel like a maze.