From 5cad7dba4195b8f6e08717d25af31fce7163aa16 Mon Sep 17 00:00:00 2001
From: Jan-Philipp Litza <janphilipp@litza.de>
Date: Sun, 19 Jan 2014 16:43:25 +0100
Subject: [PATCH] gluon-autoupdater: get random number from urandom

The approach with awk's rand() wasn't really random between across
devices: When srand() was called without arguments, time() was used as
seed, which of course is the same on all devices when the script is
called via cron at HH:00:00.

This patch instead uses /dev/urandom as source of random (we don't need
cryptographically strong random numbers, so urandom is just fine) but
still uses awk for the comparison as busybox's ash cannot deal with
floats in $(())
---
 gluon/gluon-autoupdater/files/usr/sbin/autoupdater | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gluon/gluon-autoupdater/files/usr/sbin/autoupdater b/gluon/gluon-autoupdater/files/usr/sbin/autoupdater
index bdd2324..c18e27f 100755
--- a/gluon/gluon-autoupdater/files/usr/sbin/autoupdater
+++ b/gluon/gluon-autoupdater/files/usr/sbin/autoupdater
@@ -10,7 +10,9 @@ BRANCH=$(uci get autoupdater.settings.branch)
 PROBABILITY=$(uci get autoupdater.${BRANCH}.probability)
 
 if test "a$1" != "a-f"; then
-  echo | awk "END{srand();exit rand() > $PROBABILITY}"
+  # get one random byte from /dev/urandom, convert it to decimal and check
+  # against update_probability*255
+  hexdump -n1 -e '/1 "%d"' /dev/urandom | awk "{exit \$1 > $PROBABILITY * 255}"
   if test $? -ne 0; then
     echo "No autoupdate this time. Use -f to override"
     exit 0