#!/usr/bin/env bash
set -euo pipefail
trap 'kill $(jobs -p)' EXIT
SERVER="sir0.dxng.net"
PORT=12022
find_free_tun() {
used=$(echo "$@" | awk -F: '{print $2}' | grep -o 'tun[0-9]\+' | sed 's/tun//' | sort -n)
candidate=0
for n in $used; do
if [ "$n" -eq "$candidate" ]; then
candidate=$((candidate+1))
else
break
fi
done
echo $candidate
}
LOCAL_TUN=$(find_free_tun "$(ip -o link show)")
REMOTE_TUN=$(find_free_tun "$(ssh -np $PORT root@$SERVER ip -o link show)")
SERVER_IP="192.168.98.1"
CLIENT_IP="192.168.98.$((200+REMOTE_TUN))"
echo "[*] Local tun$LOCAL_TUN <-> Remote tun$REMOTE_TUN"
echo "[*] Local addr $CLIENT_IP <-> Remote addr $SERVER_IP"
ssh -w $LOCAL_TUN:$REMOTE_TUN -p $PORT root@$SERVER -o PermitLocalCommand=yes -o LocalCommand="ip link set tun$LOCAL_TUN up && ip addr add $CLIENT_IP peer $SERVER_IP dev tun$LOCAL_TUN" -o RemoteCommand="ip link set tun$REMOTE_TUN up && ip addr add $SERVER_IP peer $CLIENT_IP dev tun$REMOTE_TUN" &
if ping -c 4 $SERVER_IP; then
    echo "[*] Tunnel established successfully"
    wait
else
    echo "[*] Tunnel establishment failed, exiting"
    exit
fi