Tips and Tricks: 2023

root@socks:~/antifilter# cat subnet-cidr-to-openvpn-netmask.sh
#!/bin/bash
# Author: danitfk (Daniel Gordi)
# Date: 15/Dec/2018
# A function to declare variables CDIR -> NETMASK
# Get IP Input

while IFS= read -r line; do
export IP_CIDR="$line"

function set_variables {
export cidr_32=255.255.255.255
export cidr_31=255.255.255.254
export cidr_30=255.255.255.252
export cidr_29=255.255.255.248
export cidr_28=255.255.255.240
export cidr_27=255.255.255.224
export cidr_26=255.255.255.192
export cidr_25=255.255.255.128
export cidr_24=255.255.255.0
export cidr_23=255.255.254.0
export cidr_22=255.255.252.0
export cidr_21=255.255.248.0
export cidr_20=255.255.240.0
export cidr_19=255.255.224.0
export cidr_18=255.255.192.0
export cidr_17=255.255.128.0
export cidr_16=255.255.0.0
export cidr_15=255.254.0.0
export cidr_14=255.252.0.0
export cidr_13=255.248.0.0
export cidr_12=255.240.0.0
export cidr_11=255.224.0.0
export cidr_10=255.192.0.0
export cidr_9=255.128.0.0
export cidr_8=255.0.0.0
export cidr_7=254.0.0.0
export cidr_6=252.0.0.0
export cidr_5=248.0.0.0
export cidr_4=240.0.0.0
export cidr_3=224.0.0.0
export cidr_2=192.0.0.0
export cidr_1=128.0.0.0
}
# A function to detect CIDR like /32
function detect_cidr {
export IP=`echo $IP_CIDR | cut -d"/" -f1`
export CIDR=`echo $IP_CIDR | cut -d"/" -f2`
export CIDR_TEST=`echo $CIDR | grep "\."`
if [[ "$CIDR_TEST" != "" ]]
then
echo "CDIR is not valid"
exit 1
fi
if [[ "$CIDR" -gt "32" ]] || [[ "$CIDR" -lt "1" ]] || [[ "$CIDR" == "" ]]
then
echo "CIDR is not valid"
exit 1
fi
}

# Function to convert CIDR like /32 to 255.255.255.255

function print_subnet {
echo "echo $IP \$cidr"_$CIDR | bash | awk '{print "push \"route "$1" "$2"\""}'

}

set_variables
detect_cidr
print_subnet

done < "$1"

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