netmenu_setup_iface

#!/bin/bash
#https://www.opennet.ru/base/sys/sed_edit_interfaces.txt.html

[ -z "$1" -o -z "$2" ] && echo "iface action" && exit 0

interfaces="/etc/network/interfaces"

function ip_prompt() {
while true; do
    read -p "$1: " new_par
    if [ -z `echo $new_par` ]; then
        new_par="$1"
        break
    elif [ -z `echo $new_par | sed -n -r '/((1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])\.){3}(1?[0-9][0-9]?|2[0-4][0-9]|25[0-5])/p'` ]; then
        echo "xxx.xxx.xxx.xxx"
        :
    else
        break
    fi
done
}

dhclient $1 -r

if [[ "$2" == "d" ]]; then
    ip -4 addr flush dev $1
    if [[ -z `cat /etc/network/interfaces | grep $1` ]]; then
        ip route del default  dev $1 2>&1 1>/dev/null || true
        ip link set dev $1 down
        echo "" > /etc/resolve.conf
    else
        sed -i -r  "s/iface $1.*$/iface $1 inet dhcp/" "$interfaces"
        sed -i -r  "/iface $1/!b;:x;n;s/^./#\0/;/^$/b;bx" "$interfaces"
        ifdown $1
        #echo "" > /etc/resolve.conf
    fi
    dhclient $1
fi

if [[ "$2" == "s" ]]; then
    echo "Static configuration $1"
    sed -i -r "s/iface $1.*$/iface $1 inet static/" "$interfaces"
    sed -i "/iface $1/!b;:x;n;s/^#\+//;/^$/b;bx" "$interfaces"
    old_address=$(sed -n -r "/iface $1/!b;:x;n;/^.*address/s/^.*address([ ])*//p;/iface/b;bx" "$interfaces")
    old_netmask=$(sed -n -r "/iface $1/!b;:x;n;/^.*netmask/s/^.*netmask([ ])*//p;/iface/b;bx" "$interfaces")
    old_gateway=$(sed -n -r "/iface $1/!b;:x;n;/^.*gateway/s/^.*gateway([ ])*//p;/iface/b;bx" "$interfaces")

    echo -n "Enter new address: "
    ip_prompt $old_address
    new_address=$new_par
    clear
    echo "Address - $new_address"
    echo -n "Enter new netmask: "
    ip_prompt $old_netmask
    new_netmask=$new_par
    clear
    echo "Address - $new_address"
    echo "Netmask - $new_netmask"
    echo -n "Enter new gateway: "
    ip_prompt $old_gateway
    new_gateway=$new_par
    clear
    echo "Address - $new_address"
    echo "Netmask - $new_netmask"
    echo "Gateway - $new_gateway"

    echo -n "Enter new DNS1: "
    read dns1
    echo -n "Enter new DNS2: "
    read dns2

    clear
    echo "Address - $new_address"
    echo "Netmask - $new_netmask"
    echo "Gateway - $new_gateway"
    echo "DNS - $dns1 $dns2"

    read -p "Apply changes? [y/n]" apply
    if [ "$apply" ] && [ "$apply" == "y" ]; then
        if [[ -z `cat $interfaces | grep $1` ]]; then
            ip link set dev $1 up
            ip addr add $new_address/$new_netmask dev $1 label $1
            ip route add default via $new_gateway  dev $1 onlink
        else
            sed -i -r "/iface $1/!b;:x;n;s/address.*/address $new_address/;t;/iface/b;bx" $interfaces
            sed -i -r "/iface $1/!b;:x;n;s/netmask.*/netmask $new_netmask/;t;/iface/b;bx" $interfaces
            sed -i -r "/iface $1/!b;:x;n;s/gateway.*/gateway $new_gateway/;t;/iface/b;bx" $interfaces
            ifdown $1
            ifup $1
        fi
        if [ "$dns1" ]; then
            echo -e "nameserver $dns1" > /etc/resolv.conf
            if [ "$dns2" ]; then
                 echo -e "nameserver $dns2" >> /etc/resolv.conf
            fi
        else echo "" > /etc/resolv.conf
        fi
    fi
fi

if [[ "$2" == "m" ]]; then
    ip -4 addr flush dev $1
    echo "" > /etc/resolve.conf
    if [[ -z `cat /etc/network/interfaces | grep $1` ]]; then
        ip route del default  dev $1 2>&1 1>/dev/null || true
    else
        sed -i -r  "s/iface $1.*$/iface $1 inet manual/" "$interfaces"
        sed -i -r  "/iface $1/!b;:x;n;s/^./#\0/;/^$/b;bx" "$interfaces"
        ifdown $1
    fi
fi

exit 0