ppp: Extend uci datamodel with persistency sypport

PPP daemon can be put into persist mode meaning the
daemon will not exit after a connection gets terminated
but will instead try to reopen the connection.
The re-initiation after the link has been terminated
can be controlled via holdoff; this is helpfull in
scenarios where a BRAS is in denial of service mode
due to link setup requests after a BRAS has gone down

Following uci parameters have been added :
persist (boolean) : Puts the ppp daemon in persist mode
maxfail (integer) : Number of consecutive fail attempts which
puts the PPP daemon in exit mode
holdoff (interget) : Specifies how many seconds to wait
before re-initiating link setup after it has been terminated

Signed-off-by: Alin Nastac <alin.nastac@gmail.com>
Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

package/network/services/ppp/Makefile

@@ -10,7 +10,7 @@ include $(INCLUDE_DIR)/kernel.mk
 
 PKG_NAME:=ppp
 PKG_VERSION:=2.4.7
-PKG_RELEASE:=9
+PKG_RELEASE:=10
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://download.samba.org/pub/ppp/

package/network/services/ppp/files/ppp.sh

@@ -79,13 +79,16 @@ ppp_generic_init_config() {
 	proto_config_add_int mtu
 	proto_config_add_string pppname
 	proto_config_add_string unnumbered
+	proto_config_add_boolean persist
+	proto_config_add_int maxfail
+	proto_config_add_int holdoff
 }
 
 ppp_generic_setup() {
 	local config="$1"; shift
 	local localip
 
-	json_get_vars ipv6 demand keepalive keepalive_adaptive username password pppd_options pppname unnumbered
+	json_get_vars ipv6 demand keepalive keepalive_adaptive username password pppd_options pppname unnumbered persist maxfail holdoff
 	if [ "$ipv6" = 0 ]; then
 		ipv6=""
 	elif [ -z "$ipv6" -o "$ipv6" = auto ]; then
@@ -98,6 +101,12 @@ ppp_generic_setup() {
 	else
 		demand=""
 	fi
+	if [ -n "$persist" ]; then
+		[ "${persist}" -lt 1 ] && persist="nopersist" || persist="persist"
+	fi
+	if [ -z "$maxfail" ]; then
+		[ "$persist" = "persist" ] && maxfail=0 || maxfail=1
+	fi
 	[ -n "$mtu" ] || json_get_var mtu mtu
 	[ -n "$pppname" ] || pppname="${proto:-ppp}-$config"
 	[ -n "$unnumbered" ] && {
@@ -129,7 +138,8 @@ ppp_generic_setup() {
 		${autoipv6:+set AUTOIPV6=1} \
 		nodefaultroute \
 		usepeerdns \
-		$demand maxfail 1 \
+		$demand $persist maxfail $maxfail \
+		${holdoff:+holdoff "$holdoff"} \
 		${username:+user "$username" password "$password"} \
 		${connect:+connect "$connect"} \
 		${disconnect:+disconnect "$disconnect"} \