[OE-core] [PATCH 3/3] rng-tools: Add support for Atheros 9170 hwrng

[Jan Kiszka]

From: Jan Kiszka <jan.kiszka at siemens.com>

Useful only on devices with no other sources: USB WLAN sticks based on
the Atheros 9170 (carl9170 kernel driver) provide a hardware random
generator. However, the interface needs to be up in order to is the
generator. That's not the case until ifup ran, but wpa_supplicant will
block this until the random pool is initialized.

Signed-off-by: Jan Kiszka <jan.kiszka at siemens.com>
---
 meta/recipes-support/rng-tools/rng-tools/default | 4 ++++
 meta/recipes-support/rng-tools/rng-tools/init    | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/meta/recipes-support/rng-tools/rng-tools/default b/meta/recipes-support/rng-tools/rng-tools/default
index b968f2b789..85c5833a32 100644
--- a/meta/recipes-support/rng-tools/rng-tools/default
+++ b/meta/recipes-support/rng-tools/rng-tools/default
@@ -4,3 +4,7 @@ RNG_DEVICE=/dev/hwrng
 # Don't use urandom as source unless you fully understood what that does to
 # your system security!
 #RNG_DEVICE=/dev/urandom
+
+# Specify wlan interface to enable if rngd should use Atheros 9170 as source.
+# See kernel config help for the security limitations of this.
+#CARL9170_HWRNG_INTERFACE="wlan0"
diff --git a/meta/recipes-support/rng-tools/rng-tools/init b/meta/recipes-support/rng-tools/rng-tools/init
index 7cf78393a4..30cfc0f3d5 100644
--- a/meta/recipes-support/rng-tools/rng-tools/init
+++ b/meta/recipes-support/rng-tools/rng-tools/init
@@ -20,6 +20,9 @@ fi
 case "$1" in
   start)
     echo -n "Starting random number generator daemon"
+    if [ -n "$CARL9170_HWRNG_INTERFACE" ]; then
+        ip link set $CARL9170_HWRNG_INTERFACE up
+    fi
     start-stop-daemon -S -q -x $rngd $EXTRA_ARGS
     echo "."
     ;;
-- 
2.12.3