> Interesting. Pinging is handled entirely by the kernel. I wonder if the ACK code path has to enter and leave userspace before the response comes out the netwo

> Interesting. Pinging is handled entirely by the kernel. I wonder if the ACK code path has to enter and leave userspace before the response comes out the network card? Normally there is an incoming backlog, i.e. the kernel accepts (SYN/ACKs) incoming connections before accept(2) happens; accept(2) just pops a connection off the backlog.