gue-tunnel

#!/bin/bash
set -e

usage() {
	bin=$(basename $0)
	echo >&2 "Usage:"
	echo >&2 "  $bin { add | del } [-v]"
	echo >&2 "    [ -n tun-num ] [ -o tun-num-offset ]"
	echo >&2 "    tun-name tun-dst-addr tun-port-base  addr-local addr-peer"
	echo >&2
	echo >&2 "Creates GUE tunnel to specified tun-dst-addr,"
	echo >&2 " with src/dst port calculated as: tun-port-base [+tun-num [-tun-num-offset]]"
	echo >&2 "If tun-num-offset is specified without tun-num,"
	echo >&2 " latter is picked as last arg from led-blink-arg pid cmdline."
	echo >&2 "Resulting tun-num is substituted instead of @ in all addrs."
	exit ${1:-0}
}

op=$1
case "$op" in
	a|add) op=add;;
	d|del) op=del;;
	*) usage 1;;
esac
shift

verbose= tun_num= tun_offset=
while getopts ":hvn:o:" opt
do case "$opt" in
	h) usage 0;;
	n) tun_num=$OPTARG;;
	o) tun_offset=$OPTARG;;
	v) verbose=t;;
	*) echo >&2 "ERROR: Invalid option: -$OPTARG"; usage 1;;
esac; done
shift $((OPTIND-1))
[[ $# -eq 5 ]] || usage 1
tun=$1 tun_dst=$2 tun_base=$3 iface_addr=$4 iface_peer=$5

[[ -n "$tun_num" || -z "$tun_offset" ]] || {
	tun_num=$(pgrep -ofa -U0 '\<led-blink-arg\>' | awk '{print $NF}')
	[[ -n "$tun_num" ]] || {
		echo >&2 "Failed to auto-detect tun-num from led-blink-arg cmd"
		exit 1
	}
}
[[ -z "$tun_offset" ]] || tun_num=$(( "$tun_num" - "$tun_offset" ))
[[ -n "$tun_num" ]] || tun_num=0
tun_port=$(( "$tun_base" + "$tun_num" ))

tun_dst=${tun_dst//@/$tun_num}
iface_addr=${iface_addr//@/$tun_num}
iface_peer=${iface_peer//@/$tun_num}

if [[ "$op" = add ]]; then
	[[ -z "$verbose" ]] || { echo "Tunnel [$tun] port: $tun_port"; set -x; }
	modprobe fou
	modprobe gre
	ip link add name "$tun" type gre remote "$tun_dst" ttl 225 \
		encap gue encap-sport "$tun_port" encap-dport "$tun_port" \
		noencap-csum noencap-remcsum
	ip addr add "$iface_addr" peer "$iface_peer" dev "$tun"
	ip link set "$tun" up
	ip fou add port "$tun_port" gue
	exit 0
fi

if [[ "$op" = del ]]; then
	[[ -z "$verbose" ]] || set -x
	ip addr flush dev "$tun"
	ip link set "$tun" down
	ip link del "$tun"
	ip fou del port "$tun_port"
	exit 0
fi