kcptun: add new package

kcptun is a stable & secure tunnel based on kcp with N:M multiplexing.
https://github.com/xtaci/kcptun

Signed-off-by: Dengfeng Liu <liudf0716@gmail.com>

net/kcptun/files/kcptun-s.init

@@ -0,0 +1,56 @@
+#!/bin/sh /etc/rc.common
+# Copyright (C) 2019 Dengfeng Liu
+
+START=99
+
+USE_PROCD=1
+NAME=kcptun-s
+PROG=/usr/bin/${NAME}
+
+validate_section_kcptun() 
+{
+	uci_load_validate "${NAME}" kcptun "$1" "$2" \
+		'local_port:port' \
+		'target_ip:string' \
+		'target_port:port' \
+		'mode:string' \
+		'nocomp:bool' \
+		'sndwnd:uinteger' \
+		'rcvwnd:uinteger' \
+		'disabled:bool'
+}
+
+kcptun_instance() 
+{
+	[ "$2" = 0 ] || {
+		echo "validation failed"
+		return 1
+	}
+
+	[ "${disabled}" = "1" ] && return 1
+
+	[ "${local_port}" -gt 0 ] && [ "${local_port}" -lt 65536 ] || return 1
+
+	[ "${target_port}" -gt 0 ] && [ "${target_port}" -lt 65536 ] || return 1
+	
+	[ -n "${target_ip}" ] || {
+		return 1
+	}
+
+	procd_open_instance
+	procd_set_param command "${PROG}"
+	procd_append_param command --listen ":${local_port}"
+	procd_append_param command --target "${target_ip}:${target_port}"
+	[ -n "${mode}" ] && procd_append_param command --mode "${mode}"
+	[ "${nocomp}" -eq 1 ] && procd_append_param command --nocomp
+	[ "${sndwnd}" -gt 0 ] && procd_append_param command --sndwnd "${sndwnd}"
+	[ "${rcvwnd}" -gt 0 ] && procd_append_param command --rcvwnd "${rcvwnd}"
+	procd_set_param respawn
+	procd_close_instance
+}
+
+start_service() 
+{
+	config_load "${NAME}"
+	config_foreach validate_section_kcptun kcptun kcptun_instance
+}