strongswan: allow to specify per-connection reqid with UCI

This is useful to assign all traffic to a fw3 zone, e.g.:

/etc/config/ipsec:

config remote 'test'
	list tunnel		'dev'
...

config 'tunnel' 'dev'
	option reqid		'33'
...

/etc/config/firewall:

config zone
	option name		wan
	option extra_src	"-m policy --pol none --dir in"
	option extra_dest	"-m policy --pol none --dir out"
...

config zone
	option name		vpn
	# subnet needed for firewall3 before 22 Nov 2019, 8174814a
	list subnet		'0.0.0.0/0'
	option extra_src	"-m policy --pol ipsec --dir in --reqid 33"
	option extra_dest	"-m policy --pol ipsec --dir out --reqid 33"
...

Signed-off-by: Paul Fertser <fercerpav@gmail.com>

net/strongswan/files/ipsec.init

@@ -140,6 +140,7 @@ config_conn() {
 	local dpddelay
 	local inactivity
 	local keyexchange
+	local reqid
 
 	config_get mode                     "$1"           mode "route"
 	config_get local_subnet             "$1"           local_subnet ""
@@ -159,6 +160,7 @@ config_conn() {
 	config_get dpddelay                 "$1"           dpddelay "30s"
 	config_get inactivity               "$1"           inactivity
 	config_get keyexchange              "$1"           keyexchange "ikev2"
+	config_get reqid                    "$1"           reqid
 
 	[ -n "$local_nat" ] && local_subnet=$local_nat
 
@@ -180,6 +182,7 @@ config_conn() {
 	ipsec_xappend "  dpddelay=$dpddelay"
 
 	[ -n "$inactivity" ] && ipsec_xappend "  inactivity=$inactivity"
+	[ -n "$reqid" ] && ipsec_xappend "  reqid=$reqid"
 
 	if [ "$auth_method" = "psk" ]; then
 		ipsec_xappend "  leftauth=psk"