# shellcheck shell=sh disable=SC1008

# shellcheck shell=sh disable=SC2094

_random()

_random_bytes_as_int()

	local r=${RANDOM} # checkbashisms: false positive, we handle it AFTERWARDS

	local hex num_bytes="$1"

	if [ -n "${r}" ]; then

		echo "${r}"

	# While POSIX does not require that /dev/urandom exist, it is a

	# de-facto standard. Therefore, the following approach should be

	# highly portable in practice. In the case of Linux, and unlike BSD

	# this interface does not block in the event that the CSRNG has not

	# yet been seeded. Still, this is acceptable because we do not

	# require a guarantee that the entropy be cryptographically secure.

	# It's also worth noting that Linux >=5.4 is faster at seeding in

	# the absence of RDRAND/RDSEED than previous versions were.

	test -e /dev/urandom &&

	hex=$(

		LC_ALL=C tr -dc '[:xdigit:]' < /dev/urandom |

		dd bs="$(( num_bytes * 2 ))" count=1 2>/dev/null) &&

	test "${#hex}" = "$(( num_bytes * 2 ))" &&

	printf '%d\n' "0x${hex}"

}

_random_apipa_octets()

{

	local seed

	# Obtain a high-entropy 16-bit seed for use by awk's RNG. In the

	# unlikely event that the seed ends up being empty, awk will seed

	# based on the time of day, with a granularity of one second.

	seed=$(_random_bytes_as_int 2)

	# For APIPA (RFC 3927), the 169.254.0.0/16 address block is

	# reserved. This provides 65534 addresses, having accounted for the

	# network and broadcast address. Note that we must count from 1.

	awk "BEGIN {

		srand($seed)

		for (i=1; i<65535; i++) print rand() \" \" i

	}" |

	sort -k 1,1 -n |

	POSIXLY_CORRECT=1 awk '{

		hex = sprintf("%04x",$2)

		printf("%d %d\n", "0x" substr(hex,1,2), "0x" substr(hex,3,2))

	}'

}

_mktemp() {

	local tmpfile randchars

	# Try to use the non-standard mktemp(1) utility first.

	if command -v mktemp >/dev/null; then

		tmpfile=$(mktemp)

		uuidgen | sed -n -e 's/[^[:digit:]]//g' -e 's/\(^.\{1,7\}\).*/\1/p'

		# See the definition of _random_bytes_as_int() for a

	fi

		# justification of this method. It would have been nice to use

		# the mkstemp function of m4(1) but, despite being defined by

		# POSIX-1.2008, support is not yet sufficiently widespread.

		randchars=$(

			LC_ALL=C tr -dc '[:alnum:]' < /dev/urandom |

			dd bs=10 count=1 2>/dev/null) &&

		test "${#randchars}" = 10 &&

		tmpfile="${TMPDIR:-/tmp}/tmp.${randchars}" &&

		: >"${tmpfile}"

	fi &&

	printf '%s\n' "${tmpfile}"

	local iface="$1" i1= i2= addr= i=0

	local tmpfile i1 i2 addr

	_exists true || return 1

	_exists &&

	tmpfile=$(_mktemp) &&

	_random_apipa_octets > "${tmpfile}" || return

	while [ ${i} -lt 64516 ]; do

	while read -r i1 i2; do

		: $(( i1 = (_random % 255) + 1 ))

		: $(( i2 = (_random % 255) + 1 ))

			eval config_${config_index}="\"${addr}/16 broadcast 169.254.255.255\""

			eval "config_${config_index}=\"\${addr}/16 broadcast 169.254.255.255\""

	done < "${tmpfile}"

		: $(( i += 1 ))

	done