48 lines
1.1 KiB
Go
48 lines
1.1 KiB
Go
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
|
|
}
|