Golang : How to check if IP address is in range
For security purpose, sometimes a server can only accept connection from clients that are trusted and of certain IP addresses. This tutorial will demonstrate how to use bytes.Compare() function to check to see if an incoming IP address is within the trusted range.
checkip.go
package main
import (
"net"
"bytes"
"fmt"
)
var (
// specify the range of trusted IP addresses
start = net.ParseIP("198.162.1.100")
end = net.ParseIP("198.162.1.199")
)
func checkIP(ip string) bool {
//sanity check
input := net.ParseIP(ip)
if input.To4() == nil {
fmt.Printf("%v is not a valid IPv4 address\n", input)
return false
}
if bytes.Compare(input, start) >= 0 && bytes.Compare(input, end) <= 0 {
fmt.Printf("%v is between %v and %v\n", input, start, end)
return true
}
fmt.Printf("%v is NOT between %v and %v\n", input, start, end)
return false
}
func main() {
fmt.Println(checkIP("216.14.49.185"))
fmt.Println(checkIP("1.2.3.4"))
fmt.Println(checkIP("198.162.1.102"))
fmt.Println(checkIP("1::16"))
}
Output :
216.14.49.185 is NOT between 198.162.1.100 and 198.162.1.199
false
1.2.3.4 is NOT between 198.162.1.100 and 198.162.1.199
false
198.162.1.102 is between 198.162.1.100 and 198.162.1.199
true
1::16 is not an IPv4 address
false
Reference :
By Adam Ng
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