Competence might be a better label than mastery, which is a blue sky or a bottomless pit, depending on your point of view.
Maybe add something to cover graph theory. But it's hard to think of a tool as useful on a small scale (one person, not big data) as the ones you've named.
A simple build system fits the tools listed here and covers graphs. An NFA regex matcher would cover it too.
Maybe add something to do with networking? Maybe also graphics?
Almost everything I've ever done with networking was much closer to applied computer science than pure CS, but writing an HTTP client (open socket, construct and parse headers, deal with character encoding) was one of the more eye-opening experiences when I was getting started.
This is something I'd love to do. Do you have any resources for learning the background info? Everywhere I've looked just plugs in some TCP/socket library, but I think the real learning would come from _making_ the library itself.
You mean instead of using the TCP stack included in the kernel, you want to write your own? You could use raw sockets (described in man 7 raw) for that (but note that they require elevated privilege). Use socket(PF_INET, SOCK_RAW, IPPROTO_TCP) to get a raw TCP socket, then send and receive TCP packets as raw bytes over the socket.
I found an example demonstrating the approach here: http://www.tenouk.com/Module43a.html
Here's one of three parts on coding your own TCP/IP stack. I haven't gotten around to it, but it looks solid.
http://www.saminiir.com/lets-code-tcp-ip-stack-1-ethernet-ar...
More seriously though it is really useful for people who are going into embedded or systems programming to write a command line interpreter at some point in their studies. It blends a couple of disconnected courses (data structures and parsing) into something tangible and useful.
I wonder if there is a good canonical list of chunks that you should be able to create from a blank sheet of paper in order to demonstrate mastery of CS. I would put an interpreter, a database, a CLI (shell), a compiler, a scheduler, and a device driver as the list but there might be others.