Add script to show packets count from debug logs

Mineclonia has inherited mods from MineClone 2 that send a lot of network
packets. This behaviour wastes bandwith and is most likely a major reason
for the unusually high amount of lag that MineClone2 and Mineclonia have.

Many network packets that are sent by Mineclonia are entirely useless.
Analyzing minetest log files to figure out what kind of packets are
sent and how often is a first step in getting rid of useless traffic.

tools/analyze-packet-spam

@@ -0,0 +1,60 @@
+#!/bin/sh -eu
+# analyze-packet-spam – show minetest client packet count per second
+# Copyright © 2021  Nils Dagsson Moskopp (erlehmann)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+
+# Dieses Programm hat das Ziel, die Medienkompetenz der Leser zu
+# steigern. Gelegentlich packe ich sogar einen handfesten Buffer
+# Overflow oder eine Format String Vulnerability zwischen die anderen
+# Codezeilen und schreibe das auch nicht dran.
+
+# This script takes a minetest log with at least INFO log level and
+# outputs the MINETEST network protocol packet count per second.
+
+# To collect such a log file of minetest running for 10 minutes, run:
+# timeout 600 minetest --info >log.txt 2>&1 >/dev/null
+
+# To get packet counts from that file, run:
+# ./analyze-packet-spam <log.txt
+
+TEMPFILE=$(mktemp /tmp/minetest.analyze-packet-spam.XXXXXXXX)
+
+grep -F 'INFO[Main]: cmd' \
+ |while read DATE TIME _ _ PACKET_ID PACKET_NAME _ PACKET_COUNT; do
+  TIMESTAMP=$(date +%s --date "${DATE} ${TIME%:}")
+  PACKET_NAME=${PACKET_NAME#(}
+  PACKET_NAME=${PACKET_NAME%)}
+  VARIABLE=PACKET_COUNT_"${PACKET_NAME}"
+  eval "$( echo $VARIABLE=\$\(\( \${$VARIABLE:-0} + ${PACKET_COUNT} \)\) )"
+  printf '%s ' \
+   "${TIMESTAMP}" \
+   "${VARIABLE}"
+  eval echo \$${VARIABLE}
+done >"${TEMPFILE}"
+
+TIMESTAMP_START=$( <"${TEMPFILE}" head -n1 |cut -d' ' -f1 )
+TIMESTAMP_END=$( <"${TEMPFILE}" tail -n1 |cut -d' ' -f1 )
+DURATION=$(( 30 + ${TIMESTAMP_END} - ${TIMESTAMP_START} ))
+
+PACKET_NAME_SEEN=''
+<"${TEMPFILE}" tac \
+ |while read _ PACKET_NAME PACKET_COUNT; do
+  case "${PACKET_NAME_SEEN}" in
+   *"${PACKET_NAME}"*)
+   ;;
+   *)
+    PACKET_COUNT_PER_SECOND=$(
+     printf '1k %s %s /p' "${PACKET_COUNT}" "${DURATION}" \
+      |dc
+    )
+    printf '%s\t%s\n' "${PACKET_COUNT_PER_SECOND}" "${PACKET_NAME}"
+    PACKET_NAME_SEEN="${PACKET_NAME_SEEN} ${PACKET_NAME}"
+   ;;
+  esac
+ done
+
+unlink "${TEMPFILE}"