/
reverse_dns.go
49 lines (41 loc) · 1.07 KB
/
reverse_dns.go
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/*
* SPDX-FileCopyrightText: The terraform-provider-ipcalc Authors
* SPDX-License-Identifier: 0BSD
*/
package provider
import (
"fmt"
"net"
"strings"
)
func ReverseDNSIPv4(ipAddress string) string {
splitted := strings.Split(ipAddress, ".")
parts := make([]string, 0)
for i := len(splitted) - 1; i >= 0; i-- {
parts = append(parts, splitted[i])
}
joined := strings.Join(parts, ".")
return fmt.Sprintf("%v.in-addr.arpa.", joined)
}
func ReverseDNSIPv6(ipAddress net.IP) string {
expandedAddress := expandIPv6Address(ipAddress)
splitted := strings.Split(strings.ReplaceAll(expandedAddress, ":", ""), "")
parts := make([]string, 0)
for i := len(splitted) - 1; i >= 0; i-- {
parts = append(parts, splitted[i])
}
joined := strings.Join(parts, ".")
return fmt.Sprintf("%v.ip6.arpa.", joined)
}
func expandIPv6Address(ip net.IP) string {
b := make([]byte, 0, len(ip))
for i := 0; i < len(ip); i += 2 {
if i > 0 {
b = append(b, ':')
}
s := (uint32(ip[i]) << 8) | uint32(ip[i+1])
bHex := fmt.Sprintf("%04x", s)
b = append(b, bHex...)
}
return string(b)
}