// LookupDNSSEC sends the provided DNS message to a randomly chosen server (see
// ExchangeOne) with DNSSEC enabled. If the lookup fails, this method sends a
// clarification query to determine if it's because DNSSEC was invalid or just
// a run-of-the-mill error. If it's because of DNSSEC, it returns ErrorDNSSEC.
func (dnsResolver *DNSResolver) LookupDNSSEC(m *dns.Msg) (*dns.Msg, time.Duration, error) {
// Set DNSSEC OK bit
m.SetEdns0(4096, true)
r, rtt, err := dnsResolver.ExchangeOne(m)
if err != nil {
return r, rtt, err
}
if r.Rcode != dns.RcodeSuccess && r.Rcode != dns.RcodeNameError && r.Rcode != dns.RcodeNXRrset {
if r.Rcode == dns.RcodeServerFailure {
// Re-send query with +cd to see if SERVFAIL was caused by DNSSEC
// validation failure at the resolver
m.CheckingDisabled = true
checkR, _, err := dnsResolver.ExchangeOne(m)
if err != nil {
return r, rtt, err
}
if checkR.Rcode != dns.RcodeServerFailure {
// DNSSEC error, so we return the testable object.
err = DNSSECError{}
return r, rtt, err
}
}
err = fmt.Errorf("Invalid response code: %d-%s", r.Rcode, dns.RcodeToString[r.Rcode])
return r, rtt, err
}
return r, rtt, err
}