openconnect: new option mtu

According to openconnect --help output:

  -m, --mtu=MTU                   Request MTU from server
      --base-mtu=MTU              Indicate path MTU to/from server

Fixes #2099 by allowing setting tunnel mtu

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

net/openconnect/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=openconnect
 PKG_VERSION:=7.08
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_USE_MIPS16:=0
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz

net/openconnect/files/openconnect.sh

@@ -6,6 +6,7 @@ init_proto "$@"
 proto_openconnect_init_config() {
 	proto_config_add_string "server"
 	proto_config_add_int "port"
+	proto_config_add_int "mtu"
 	proto_config_add_string "username"
 	proto_config_add_string "serverhash"
 	proto_config_add_string "authgroup"
@@ -22,7 +23,7 @@ proto_openconnect_init_config() {
 proto_openconnect_setup() {
 	local config="$1"
 
-	json_get_vars server port username serverhash authgroup password password2 token_mode token_secret os csd_wrapper
+	json_get_vars server port username serverhash authgroup password password2 token_mode token_secret os csd_wrapper mtu
 
 	grep -q tun /proc/modules || insmod tun
 	ifname="vpn-$config"
@@ -38,6 +39,7 @@ proto_openconnect_setup() {
 	[ -n "$port" ] && port=":$port"
 
 	cmdline="$server$port -i "$ifname" --non-inter --syslog --script /lib/netifd/vpnc-script"
+	[ -n "$mtu" ] && cmdline="$cmdline --mtu $mtu"
 
 	# migrate to standard config files
 	[ -f "/etc/config/openconnect-user-cert-vpn-$config.pem" ] && mv "/etc/config/openconnect-user-cert-vpn-$config.pem" "/etc/openconnect/user-cert-vpn-$config.pem"