49 lines
798 B
Go

package middleware
import (
"net"
"sync"
"time"
cache "github.com/patrickmn/go-cache"
)
var ipToHosts = cache.New(60*time.Minute, 30*time.Minute)
var ipToHostsMutex sync.Mutex
// GetHostsForIP returns all host names for the given IP (if cached).
func GetHostsForIP(ip string) ([]string, bool) {
ipToHostsMutex.Lock()
defer ipToHostsMutex.Unlock()
hosts, found := ipToHosts.Get(ip)
if !found {
hosts = findHostsForIP(ip)
}
if hosts == nil {
return nil, found
}
return hosts.([]string), found
}
// Finds all host names for the given IP
func findHostsForIP(ip string) []string {
hosts, err := net.LookupAddr(ip)
if err != nil {
return nil
}
if len(hosts) == 0 {
return nil
}
// Cache host names
ipToHosts.Set(ip, hosts, cache.DefaultExpiration)
return hosts
}