First version

files/lockdown/contest-restrictions-warning

@@ -0,0 +1,41 @@
+#!/bin/bash
+# Runs as root (contest-restrictions-warning.service). While any contest
+# restriction is off (after maintenance with contest-restrictions off), shows
+# a red banner across the top of the screen, so that the proctors notice it.
+# The banner has no title bar or close button, the team account cannot stop
+# this process, and the banner comes back within seconds if its window is
+# destroyed. It is redrawn every 15 seconds to stay above the other windows.
+export DISPLAY=:0 XAUTHORITY=/var/run/lightdm/root/:0
+off() {
+    ! systemctl is-active --quiet firewall.service ||
+    ! systemctl is-active --quiet usbguard.service ||
+    [ -n "$(ls -A /etc/contest-restrictions/disabled 2>/dev/null)" ]
+}
+show() {
+    width=$(xdpyinfo 2>/dev/null | awk '/dimensions/ {split($2, a, "x"); print a[1]}')
+    [ -n "$width" ] || return
+    xmessage -geometry "${width}x70+0+0" -buttons "" \
+        -xrm "*overrideRedirect: true" \
+        -fg white -bg red3 -fn "-*-helvetica-bold-r-*-*-34-*-*-*-*-*-*-*" \
+        "CONTEST RESTRICTIONS ARE OFF ON THIS MACHINE - CALL THE STAFF" >/dev/null 2>&1 &
+    pid=$!
+    shown=$(date +%s)
+}
+pid=""
+shown=0
+while true; do
+    if off && [ -e "$XAUTHORITY" ]; then
+        if [ -z "$pid" ] || ! kill -0 "$pid" 2>/dev/null; then
+            show
+        elif [ $(( $(date +%s) - shown )) -ge 15 ]; then
+            old=$pid
+            show
+            sleep 1
+            kill "$old" 2>/dev/null
+        fi
+    elif [ -n "$pid" ]; then
+        kill "$pid" 2>/dev/null
+        pid=""
+    fi
+    sleep 3
+done