// Method used to retrieve addresses of a given nameserver, if the address does not exist
// in the local cache the system will lookup for the domain and will store the result
func (q *QuerierCache) Get(nameserver model.Nameserver, fqdn string) ([]net.IP, error) {
q.hostsMutex.RLock()
host, found := q.hosts[nameserver.Host]
q.hostsMutex.RUnlock()
if found {
if host.timeoutsPerHostExceeded() {
return nil, ErrHostTimeout
} else if host.queriesPerSecondExceeded() {
return nil, ErrHostQPSExceeded
} else {
return host.addresses, nil
}
}
// Not found in cache, lets discover the address of this name sending DNS requests or
// retrieving from the namserver object (glue record)
var addresses []net.IP
if nameserver.NeedsGlue(fqdn) {
if nameserver.IPv4 != nil {
addresses = append(addresses, nameserver.IPv4)
}
if nameserver.IPv6 != nil {
addresses = append(addresses, nameserver.IPv6)
}
}
// In case that the nameserver doesn't have a glue record we try to resolve the hostname
if len(addresses) == 0 {
var err error
addresses, err = net.LookupIP(nameserver.Host)
if err != nil {
return nil, err
}
}
q.hostsMutex.Lock()
q.hosts[nameserver.Host] = &hostCache{
addresses: addresses,
lastEpoch: 0,
queriesPerSecond: 0,
timeouts: 0,
}
q.hostsMutex.Unlock()
return addresses, nil
}
