Linux IPv6 improvement: Routing cache on demand

What this post added

This post details the implementation and upstream contribution of an on-demand routing cache for Linux IPv6. This solution addresses scalability issues caused by large routing trees in IPv6 deployments by creating routing caches only when needed, rather than pre-emptively. Key technical contributions include a patch series to the upstream kernel, per-CPU entry optimization for gateway routes to mitigate cache bouncing, and ensuring compatibility with subsystems that expect '/128' routes. The post also highlights performance improvements observed in benchmarks and discusses future work to further optimize IPv6 performance and integrate IPv4/IPv6 routing.