[Buildroot] [Next] package/haveged: set write_wakeup_threshold to 2048

Adjust the low water mark to wake-up the haveged daemon at the
same time that rngd would wake-up when a hardware RNG is present.

This supports the theory that rngd then can't dominate the entropy
pool. Instead haveged and rngd would complete to fill the pool.
https://tails.boum.org/contribute/design/random/#index5h2

If rngd isn't enabled or there isn't a hardware RNG, this change
should not impact the behavior of the entropy pool other then
the pool should be less likely to deplete and cause an entropy
starve with haveged filling it earlier.

Cc: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Matthew Weber <redacted>
---

Peter I believe this one also applys to 2020.02.x
---
 package/haveged/S21haveged | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/package/haveged/S21haveged b/package/haveged/S21haveged
index 4b6e6ced4e..22b84e4f27 100644
--- a/package/haveged/S21haveged
+++ b/package/haveged/S21haveged

@@ -3,7 +3,7 @@
 case "$1" in
 	start)
 		printf "Starting haveged: "
-		start-stop-daemon -S -x /usr/sbin/haveged -- -w 1024 -r 0
+		start-stop-daemon -S -x /usr/sbin/haveged -- -w 2048 -r 0
 		[ $? = 0 ] && echo "OK" || echo "FAIL"
 		;;
 	stop)

-- 
2.17.1

Thomas,

On Tue, May 12, 2020 at 6:39 PM Matt Weber
[off-list ref] wrote:

Adjust the low water mark to wake-up the haveged daemon at the
same time that rngd would wake-up when a hardware RNG is present.

This supports the theory that rngd then can't dominate the entropy
pool. Instead haveged and rngd would complete to fill the pool.
https://tails.boum.org/contribute/design/random/#index5h2

If rngd isn't enabled or there isn't a hardware RNG, this change
should not impact the behavior of the entropy pool other then
the pool should be less likely to deplete and cause an entropy
starve with haveged filling it earlier

I marked this as a Next item but I guess it really is sort of a bug
that should be merged before release as I believe it should apply to
LTS as well.
.

-- 

Matthew Weber | Associate Director Software Engineer | Commercial Avionics

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