nvme-cli: Add script to determine host NQN

* Based on the system-UUID, via dmidecode
* verifies UUID format
* tries to catch fake/lazy UUIDs

diff --git a/scripts/gen-hostnqn.sh b/scripts/gen-hostnqn.sh
new file mode 100644 (file)
index 0000000..d8783cf
--- /dev/null
+++ b/scripts/gen-hostnqn.sh
@@ -0,0 +1,42 @@
+#!/bin/bash
+
+LC_ALL=C
+
+UUID=$(dmidecode -s system-uuid | tr -d '[:space:]')
+
+if [ -z "$UUID" ] ; then
+       >&2 echo "No UUID found, can't determine hostnqn."
+       exit 1
+fi
+
+# convert UUID to lower-case only:
+UUID=$(echo $UUID | tr '[:upper:]' '[:lower:]')
+
+# check UUID format, e.g.: 4c4c4544-0156-4a10-8134-b7d04f383232, so: 8-4-4-4-12
+if ! [[ $UUID =~ ^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$ ]] ; then
+       >&2 echo "UUID has invalid format."
+       >&2 echo "Invalid UUID: ${UUID}"
+       exit 2
+fi
+
+# HEURISTIC:
+# (1) if any one given character occurs more than 50% of the time, it is likely
+# that the UUID is fake.
+# (2) if the first or the last group consists of mostly the same character, it
+# is likely that the UUID is fake.
+FIRST_GROUP="$(echo $UUID | cut -d'-' -f1)"
+LAST_GROUP="$(echo $UUID | cut -d'-' -f5)"
+for i in {{0..9},{a..f}} ; do
+       COUNT_TOTAL="${UUID//[^$i]}"
+       COUNT_FIRST="${FIRST_GROUP//[^$i]}"
+       COUNT_LAST="${LAST_GROUP//[^$i]}"
+       if [ ${#COUNT_TOTAL} -ge 16 ] || [ ${#COUNT_FIRST} -ge 7 ] || [ ${#COUNT_LAST} -ge 11 ] ; then
+               >&2 echo "UUID is too repetitive. This may be a false alert."
+               >&2 echo "Repetitive UUID: ${UUID}"
+               exit 3
+       fi
+done
+
+HOSTNQN="nqn.2014-08.org.nvmexpress:uuid:${UUID}"
+
+echo $HOSTNQN