1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
|
package hostname
import (
"errors"
"fmt"
"net"
"strings"
)
var ErrorEmptyDomainName error = errors.New("domain name is empty")
var ErrorDomainNameMisconfigured error = errors.New("your OS domain name is not configured correctly")
// returns 'hostname', 'domainname'
func Split(s string) (string, string) {
parts := strings.Fields(s)
if len(parts) == 0 {
return "", ""
}
if len(parts) == 1 {
return parts[0], ""
}
return parts[0], strings.Join(parts[1:], ".")
}
// checks to make sure there is a domainname
func ValidDomainname(s string) error {
_, domainname := Split(s)
if domainname == "" {
return ErrorEmptyDomainName
}
return nil
}
func ReverseLookupFQDN(hostname string) (string, error) {
addrs, err := net.LookupIP(hostname)
if err != nil || len(addrs) == 0 {
return hostname, fmt.Errorf("failed to lookup IP for hostname %s: %w", hostname, err)
}
// Try reverse lookup on the first IP address
names, err := net.LookupAddr(addrs[0].String())
if err != nil || len(names) == 0 {
return hostname, fmt.Errorf("reverse DNS lookup failed for IP %s: %w", addrs[0].String(), err)
}
return names[0], nil
}
|
