A tc-bpf action to rewrite ip->protocol to ICMP for outgoing UDP packets with source port = 0x1919, and vice versa for ingress.
- Your ISP have an interesting "management network" connecting all subscribers in the city.
- They block all traffic between subscribers, except when
ip->protocol = 1. - You want to have fun with your friend. (and discover that the link is throttled to 20Mbps)
- You heard that in 2021 there are 114514 eBPF hook points in kernel but never tried any one of them thus want a toy example slightly more complex than hello world.