fastd: make secret key update-safe

To use a whitelist easily, it is necessary to make the fastd key
update-safe.
This patch saves the key to uci fff config and recovers it for
use after a firmware upgrade.

Signed-off-by: Christian Dresel <fff@chrisi01.de>
Reviewed-by: lemmi <lemmi@nerd2nerd.org>
Reviewed-by: Robert Langhammer <rlanghammer@web.de>
Reviewed-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
[bump PKG_RELEASE, rephrase commit message]
Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

src/packages/fff/fff-fastd/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=fff-fastd
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_BUILD_DIR:=$(BUILD_DIR)/$(PKG_NAME)
 
@@ -17,7 +17,8 @@ define Package/$(PKG_NAME)
 			 +@FASTD_ENABLE_CIPHER_NULL \
 			 +@FASTD_WITH_STATUS_SOCKET \
 			 +fastd \
-			 +fff-random
+			 +fff-random \
+			 +fff-config
 endef
 
 define Package/$(PKG_NAME)/description

src/packages/fff/fff-fastd/files/etc/uci-defaults/55_fff-fastd

@@ -15,9 +15,17 @@ uci batch <<EOF
   set fastd.fff.mtu='1426'
   set fastd.fff.on_up="/etc/fastd/fff/up.sh"
   set fastd.fff.secure_handshakes='0'
-  set fastd.fff.secret="generate"
 EOF
 
+if ! secret=$(uci -q get fff.fastd.secret); then
+	secret=$(/usr/bin/fastd --generate-key --machine-readable)
+	uci set fff.fastd='fff'
+	uci set fff.fastd.secret="$secret"
+	uci commit fff
+fi
+uci set fastd.fff.secret="$secret"
+uci commit fastd
+
 [ ! -d /etc/fastd/fff ] &&  mkdir -p /etc/fastd/fff
 ln -s /tmp/fastd_fff_peers /etc/fastd/fff/peers
 echo "#!/bin/sh" > /etc/fastd/fff/up.sh