#!/bin/sh /etc/rc.common
# Copyright (C) 2019 Ycarus (Yannick Chabanois) <ycarus@zugaina.org> for OpenMPTCProuter project

# network.globals.multipath='disable' means the kernel is running with
# net.mptcp.enabled=0. Asking for an MPTCP socket then fails outright with
# ENOPROTOOPT ("Protocol not available") -- the kernel has no implicit
# fallback to plain TCP, every caller has to do it itself, and most don't.
# Only an explicit "disable" counts, so this package keeps its stock
# behaviour wherever network.globals.multipath doesn't exist at all.
_omr_mptcp_globally_disabled() {
	[ "$(uci -q get network.globals.multipath)" = "disable" ]
}

START=90
STOP=10

USE_PROCD=1
PROG_NAME=dsvpn
PROG=/usr/sbin/${PROG_NAME}

_log() {
	logger -p daemon.info -t ${PROG_NAME} "$@"
}

_err() {
	logger -p daemon.err -t ${PROG_NAME} "$@"
}

validate_section() {
	uci_validate_section dsvpn dsvpn "${1}" \
		'enable:bool:0'       \
		'key:string'          \
		'host:host'           \
		'port:port'           \
		'dev:string'          \
		'localip:host'        \
		'remoteip:host'       \
		'mode:string:client'  \
		'externalip:string:auto'
}

version_over_5_4() {
	MAJOR_VERSION=$(uname -r | awk -F '.' '{print $1}')
	MINOR_VERSION=$(uname -r | awk -F '.' '{print $2}' | awk -F '-' '{print $1}')
	if [ $MAJOR_VERSION -ge 5 ] && [ $MINOR_VERSION -gt 13 ] || [ $MAJOR_VERSION -gt 5 ] ; then
		return 0
	else
		return 1
	fi
}

start_instance() {
	local enable key host port dev mode localip remoteip externalip gateway
	local prog="$PROG"
	local key_dir="/var/run/${PROG_NAME}"
	local key_file="${key_dir}/${1}.key"

	validate_section "${1}" || {
		_err "validation failed"
		return 1
	}

	[ "${enable}" = "1" ] || return 1

	[ -n "${key}" ] || return 1
	[ "${key}" != "secretkey" ] || return 1
	[ -z "${host}" ] && host="auto"
	[ -z "${port}" ] && port="auto"
	[ -n "${dev}" ] || return 1

	mkdir -p "$key_dir"
	chmod 0700 "$key_dir"
	( umask 077; printf '%s\n' "$key" > "$key_file" ) || {
		_err "can't create key file"
		return 1
	}
	key=""

	# "uci get network.omrvpn" is the section type, never the device: this
	# ran on every start, and a bare "uci commit" flushed every package's
	# pending changes, not only this one
	if [ -n "$(uci -q get network.omrvpn)" ] && [ "$(uci -q get network.omrvpn.device)" != "$dev" ]; then
		uci -q set network.omrvpn.device=$dev
		uci -q commit network
	fi

	# dsvpn adds the tun address once, on its first connection, and procd
	# keeps an unchanged instance across a reload: flushing on every reload
	# left the running tunnel without an address. Only the tun of an
	# instance that is going away (restart) needs it. procd_running would
	# reset the jshn message start_service is building, ask ubus directly.
	if [ -d "/sys/class/net/$dev" ] &&
	   [ "$(ubus call service list "{\"name\":\"${PROG_NAME}\"}" 2>/dev/null | jsonfilter -q -l 1 -e "@['${PROG_NAME}'].instances[*].running")" != "true" ]; then
		ip addr flush dev "$dev"
		sleep 2
	fi

	_log "starting ${PROG_NAME} ${1} instance $*"

	# mptcpize LD_PRELOADs a socket() that always asks for IPPROTO_MPTCP and
	# never falls back, so with MPTCP globally off dsvpn cannot create its
	# socket at all ("Couldn't create connection: Protocol not available")
	# and procd just respawns it forever. Run it unwrapped instead.
	if version_over_5_4 && ! _omr_mptcp_globally_disabled; then
		prog="mptcpize run ${PROG}"
	fi

	# The arguments are positional: an empty one would shift the next ones
	# into its place, dsvpn takes "auto" for each instead. The gateway is the
	# route's "via": an on-link route has none, and a name can't be routed
	gateway="$(ip route get "$host" 2>/dev/null | awk '{ for (i = 1; i < NF; i++) if ($i == "via") { print $(i + 1); exit } }')"

	procd_open_instance

	procd_set_param command ${prog} ${mode} \
		"$key_file" \
		$host \
		$port \
		$dev  \
		${localip:-auto} \
		${remoteip:-auto}
	[ "$mode" = "client" ] && procd_append_param command ${gateway:-auto}
	[ "$mode" = "server" ] && procd_append_param command ${externalip:-auto}


	procd_set_param respawn 0 30 5
	procd_set_param nice 10
	procd_set_param file "$key_file"

	procd_set_param stdout 1
	procd_set_param stderr 1

	procd_close_instance


}

start_service() {
	config_load dsvpn
	config_foreach start_instance dsvpn
}

service_triggers() {
	procd_add_reload_trigger dsvpn network
}