Updates to subnet generation and client creation (#1782)

* refactor(core): allow any subnet and netmask

* fix(scripts): prevent adding more clients than the subnet allows

* fix(scripts): correctly remove leading zeros from ipv6 quartets

* refactor(core): new probabilistic subnet generation with fallback to other RFC1918 subnets

scripts/ipaddr_utils.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+
+decIPv4ToDot() {
+  local a b c d
+  a=$((($1 & 4278190080) >> 24))
+  b=$((($1 & 16711680) >> 16))
+  c=$((($1 & 65280) >> 8))
+  d=$(($1 & 255))
+  printf "%s.%s.%s.%s\n" $a $b $c $d
+}
+
+dotIPv4ToDec() {
+  local original_ifs=$IFS
+  IFS='.'
+  read -r -a array_ip <<< "$1"
+  IFS=$original_ifs
+  printf "%s\n" $((array_ip[0] * 16777216 + array_ip[1] * 65536 + array_ip[2] * 256 + array_ip[3]))
+}
+
+dotIPv4FirstDec() {
+  local decimal_ip decimal_mask
+  decimal_ip=$(dotIPv4ToDec "$1")
+  decimal_mask=$((2 ** 32 - 1 ^ (2 ** (32 - $2) - 1)))
+  printf "%s\n" "$((decimal_ip & decimal_mask))"
+}
+
+dotIPv4LastDec() {
+  local decimal_ip decimal_mask_inv
+  decimal_ip=$(dotIPv4ToDec "$1")
+  decimal_mask_inv=$((2 ** (32 - $2) - 1))
+  printf "%s\n" "$((decimal_ip | decimal_mask_inv))"
+}
+
+decIPv4ToHex() {
+  local hex
+  hex="$(printf "%08x\n" "$1")"
+  quartet_hi=${hex:0:4}
+  quartet_lo=${hex:4:4}
+  # Removes leading zeros from quartets, purely for aesthetic reasons
+  # Source: https://stackoverflow.com/a/19861690
+  leading_zeros_hi="${quartet_hi%%[!0]*}"
+  leading_zeros_lo="${quartet_lo%%[!0]*}"
+  printf "%s:%s\n" "${quartet_hi#"${leading_zeros_hi}"}" "${quartet_lo#"${leading_zeros_lo}"}"
+}
+
+cidrToMask() {
+  # Source: https://stackoverflow.com/a/20767392
+  set -- $((5 - (${1} / 8))) \
+    255 255 255 255 \
+    $(((255 << (8 - (${1} % 8))) & 255)) \
+    0 0 0
+  shift "${1}"
+  echo "${1-0}.${2-0}.${3-0}.${4-0}"
+}