With this CLI I am able to listen for external packets to port 80 from userspace without any elevated permissions and intercept traffic that's going to an application that's bound to that port on the OS?
Edit: I think I understand what you're trying to do, but if I do then traffic is going from the kernel UDP stack to the userland TCP stack, back to the UDP kernel stack. Not sure how that avoids sending the packet to the kernel. If it's to get around the port restrictions, why can you not just use unprivileged ports?
I understand that, I just don't understand any case where that's desirable...
We have 2^32 ports available to applications(and a special `0` port that can be used to request any port) on a single IP(which is usually shared between multiple machines). I have never heard of a case where 2^32 ports is not enough ports for the number of applications that need to be listening.
> To the OS, it's all just ordinary socket code.
Which is what I don't understand. Why not just use ordinary socket code without all of these additional LoC in between that open you up to more bugs(security and functionality).
You can't if your organization prevents you to, for example.
You don't want to if you follow strict rules which are not enforced by the OS, again for example.
