change ip and mac address of specified nic

hopip.sh

#!/bin/sh
set -o nounset

network="10.1.1.";
network_bits="24";
gateway="10.1.1.254";
gateway_mac="aa:bb:cc:11:22:33";
nic="$1";
real_macaddr=$(cat /sys/class/net/${nic}/address);
current_ip=$(hostname -I | cut -d ' ' -f1);


generate_ip() {
    local ip;
    for i in $(shuf <(seq $1 $2) | head -n1 ); do ip="${network}${i}"; done;
    echo "$ip";
}


generate_rand_hex() {
    local words="$1";
    local word;
    word=$(strings /dev/urandom | egrep -o "[a-f0-9]" | head -n "$words" | tr -d "\n" | sed -e "s/\(.\{2\}\)/&:/g" -e "s/:$//g");
    echo "$word";
}


generate_macaddr() {
    local macaddr;
    local high4_1st_oct;
    local low4_1st_oct;
    local the_rest;
    high4_1st_oct=$(generate_rand_hex 1);
    low4_1st_oct=$(shuf -e 0 2 4 6 8 a c e | head -n1);
    the_rest=$(generate_rand_hex 10);
    macaddr="${high4_1st_oct}${low4_1st_oct}:${the_rest}";
    echo "$macaddr";
}


check_duplicate() {
    local ip="$1";
    local macaddr="$2";
    sudo arping -i "$nic" -c1 -r "${ip}" > /dev/null || sudo arping -i "$nic" -c1 -r "$macaddr" > /dev/null;
}


while true; do
    echo "$real_macaddr" >> hopip.log;
    ip=$(generate_ip "$2" "$3");
    macaddr=$(generate_macaddr)
    check_duplicate "$ip" "$macaddr" || echo "$ip" "$macaddr"; break;
done

sudo ip addr delete "${current_ip}/${network_bits}" dev "$nic";
sudo ip link set "$nic" down;
sudo ip link set "$nic" address "$macaddr";
sudo ip link set "$nic" up;
sudo ip addr add "${ip}/${network_bits}" dev "$nic";
sudo ip route add default via "$gateway";
sudo arp -s "$gateway" "$gateway_mac";