[e2e] ICMP & TCP segments with IP ID = 0?

[Dan McDonald]

> In addition the classic global ipid counter is a contended global resource
> on a multiprocessor stack, and maintaining it per destination also has its
> problems.

All CPUs I know of that live in MP machines have primitives that make
atomic-add-return-newval at worst a small spin.  A clean atomic add primitive
in one's kernel or library should solve that problem w/o pain.

Dan