commit the backend!!!! 🎉

backend/container/bin/boot.rb

@@ -0,0 +1,120 @@
+#!/usr/bin/env ruby
+# encoding: BINARY
+
+# This script starts a QEMU child process wearing a VNC sock and acts as
+# middleman between the socket and stdin/out. Perfect for VNC clients that
+# utilize binary websockets (ex: noVNC.js).
+#
+# Usage: ./boot.rb /root/images [/usr/local/bin/qemu-system-i386]
+
+require "fileutils"
+require "socket"
+require "timeout"
+
+# folder containing the OS's hdd.img, other instance files will also go here
+# default for container is set, can be optionally overridden by first argument
+base_path = ARGV[0] || "/home/vm"
+
+# location of QEMU binary (`qemu-system-i386` here, or `-x86_64` for 64-bit)
+# default for container is set, can be optionally overridden by second argument
+qemu_path = ARGV[1] || "/usr/bin/qemu-system-i386"
+
+# create a temporary directory for each instance from PID
+# NOTE: not needed when containerized, everything's already ephemeral
+# instance_dir = "/tmp/y2k.#{$$}"
+
+# flush data immediately to stdout instead of buffering
+# https://ruby-doc.org/core-2.7.0/IO.html#method-i-sync-3D
+$stdout.sync = true
+
+begin
+  # make the temp dir for our new instance & grab a fresh copy of the OS
+  # NOTE: not needed when containerized, everything's already ephemeral
+  # FileUtils.makedirs(instance_dir)
+  # FileUtils.cp(base_img, "#{instance_dir}/hdd.img")
+
+  # open a catch-all log file
+  log_file = File.open("#{base_path}/out.log", "w")
+
+  # start QEMU as a child process (TODO: put config somewhere more manageable)
+  qemu = spawn qemu_path,
+    "-hda", "#{base_path}/hdd.img",
+    "-cpu", "pentium3,enforce",
+    "-smp", "1",
+    "-m", "128",
+    "-net", "none",
+    "-serial", "none",
+    "-parallel", "none",
+    "-vga", "std",
+    "-usb",
+    "-device", "usb-tablet",
+    "-rtc", "base=localtime",
+    "-no-acpi",
+    "-no-reboot",
+    "-nographic",
+    "-vnc", "unix:#{base_path}/vnc.sock",
+    { :in => :close, :out => log_file, :err => log_file }
+
+  # limit CPU usage of each VM (if host supports it)
+  # NOTE: setting --cpus with Docker makes this redundant
+  # if File.exist?("/usr/bin/cpulimit")
+  #   cpulimit = spawn "/usr/bin/cpulimit",
+  #     "--pid", "#{qemu}",
+  #     "--limit", "90",
+  #     { :in => :close, :out => log_file, :err => log_file }
+  # end
+
+  # wait until the VNC socket is created; only takes a fraction of a second (if
+  # the server load is low) but everything following this will freak the f*ck
+  # out if it's not there yet
+  Timeout.timeout(15) do
+    until File.exist?("#{base_path}/vnc.sock")
+      sleep 0.02
+    end
+  end
+
+  # attach ourselves to the VM's VNC socket made by QEMU
+  sock = UNIXSocket.new("#{base_path}/vnc.sock")
+
+  # everything's all set up now, time to simply pass data between user and VM
+  while $stdin do
+    begin
+      # monitor the IO buffer for unprocessed data (read from both directions)
+      read, _, err = IO.select([$stdin, sock], nil)
+
+      # break out of loop if anything goes wrong, doesn't really matter what tbh
+      if err.any?
+        break
+      end
+
+      # pass input from user to VM
+      if read.include?($stdin)
+        data = $stdin.readpartial(4096)
+        sock.write(data) unless data.empty?
+      end
+
+      # pass output from VM to user
+      if read.include?(sock)
+        data = sock.readpartial(4096)
+        $stdout.write(data) unless data.empty?
+
+        # send output immediately (see $stdout.sync above)
+        $stdout.flush
+      end
+    rescue EOFError
+      # we stopped receiving input from the user's end, so don't expect any more
+      break
+    end
+  end
+ensure
+  # the user's done (or we crashed) so stop their personal VM; everything else
+  # will be deleted along with the Docker container
+  Process.kill(:SIGTERM, qemu) if qemu
+
+  # kill cpulimit if it didn't stop itself already
+  # Process.kill(:SIGTERM, cpulimit) if cpulimit
+
+  # ...and delete their hard drive, logs, etc.
+  # NOTE: not needed when containerized
+  # FileUtils.rm_rf(instance_dir)
+end