Check if an IP falls into an IP range using sh?

Question

Let's suppose I have an IP 173.245.50.16, and I want to check if it falls into the Cloudflare's IP ranges. That basically comes down to:

network_address(173.245.50.16/20) == 173.245.48.0
|| network_address(173.245.50.16/22) == 103.21.244.0
|| ...

Right? Well, I'm not sure about the terminology here, but hopefully you've got the point.

How does that translate into sh code?

Answer 1

What I came up with:

cf_ip_ranges=`curl -sS https://www.cloudflare.com/ips-v4`
is_cf_ip() {
    local ip=$1
    local range=$(echo "$cf_ip_ranges" | while IFS= read -r; do
        net=${REPLY%/*}
        n=${REPLY#*/}
        if [ "`ipv4calc --network "$ip/$n"`" = "$net" ]; then
            echo "$REPLY"
            break
        fi
    done)
    if [ "$range" ]; then
        return 0
    else
        return 1
    fi
}
if is_cf_ip 8.8.8.8; then
    echo true
else
    echo false
fi
if is_cf_ip 173.245.50.16; then
    echo true
else
    echo false
fi

Here I'm using Perl's Net::IPv4Addr module.