#!/bin/bash

number_int="$1"
my_bridge='br0'
bridge_ip='172.17.100.80/16'
ethernet='enp4s0f2'
my_gw='172.17.100.1'
google_dns='8.8.8.8'

c=0

[ $(id -u) != 0 ] && echo "Run the script as sudo" && exit 1

check_arg () {
 if [ -z "$number_int" ]; then
   echo "Run '$0' with number of tap interfaces as script's argument"
 elif [[ ! "$number_int" =~ ^[0-9]+$ ]] || [[ "$number_int" -eq 0 ]]; then
   echo "'$number_int' is NOT correct number of interfaces"
 fi
}

create_br0 () {
 ip link show dev "$my_bridge" &>/dev/null; bridge_exists="$?"
 if [ "$bridge_exists" == 0 ]; then
   echo "Interface '$my_bridge' found, exiting" && exit 1
 elif [ "$bridge_exists" == 1 ]; then
   ip link add dev "$my_bridge" type bridge
   echo -e "Interface '$my_bridge' has been created"
 fi

 sudo ip link set dev "$my_bridge" up
 ip addr add "$bridge_ip" dev "$my_bridge"
 echo -e "IP address '$bridge_ip' configured for bridge '$my_bridge'\n"
} 
	
add_ethernet () {
 sudo ip addr add dev "$ethernet" 0.0.0.0
 sudo ip link set dev "$ethernet" up
 sudo  ip link set dev "$ethernet" master "$my_bridge"
 echo -e "Interface '$ethernet' has been added to bridge '$my_bridge'\n"
}

add_tap () {
 ip link show dev "tap$c" &>/dev/null; tap_exists="$?"
 if [ "$tap_exists" == 1 ]; then
   sudo ip tuntap add dev "tap$c" mode tap
   echo "Interface 'tap$c' has been created"
 elif [ "$tap_exists" == 0 ]; then
   echo "Interface 'tap$c' found, nothing to do"
 fi

 sudo ip link set dev "tap$c" up
 sudo ip link set dev "tap$c" master "$my_bridge"
 echo -e "Interface 'tap$c' has been added to bridge '$my_bridge'\n"
}

add_internet () {
 sudo ip route add 0.0.0.0/0 via "$my_gw"
 grep "$google_dns" /etc/resolv.conf &>/dev/null; google_dns_exists="$?"
 if [ "$google_dns_exists" != 0 ]; then
   echo "nameserver $google_dns" >> /etc/resolv.conf
   echo -e "Google DNS '$google_dns' added into /etc/resolv.conf\n"
 fi
}

### BODY ###
 
check_arg 
create_br0
add_ethernet
add_internet

for ((c; c<=$number_int-1; c+=1)); do
  add_tap
done