Cilium 1.20: Gateway API ExternalAuth, TCPRoute/UDPRoute, ENI IPAM for IPv6, and more

Cilium 1.20 is a decent argument for finally upgrading your kernel. Datapath mode now auto-selects netkit on kernel 6.8 or newer and falls back to veth otherwise - ByteDance reports about 10% better performance on netkit, and Meta runs it across millions of containers. Gateway API moves to v1.6 with TCPRoute and UDPRoute, so L4 services get the same treatment as HTTP. The cilium-cni binary also went from 76 MB to 16 MB.