eBPF, Sockets, Hop Distance and manually writing eBPF assembly

This post introduces the use of eBPF (extended Berkeley Packet Filter) and socket options (`SO_ATTACH_BPF`) for advanced network introspection. It details how eBPF can be used to extract IP TTL values from TCP connections to determine hop distance, a novel approach to verifying traffic routing outside of the datacenter. The post also delves into the technical challenges and implementation details of writing eBPF assembly, including the use of eBPF maps for data sharing between kernel and userspace.