Function msgToKeyWithSubnet

proxy/cache.go:565–596

msgToKeyWithSubnet constructs the cache key from DO bit, type, class, subnet mask, client's IP address and question's name of m. ecsIP is expected to be masked already.

(m *dns.Msg, ecsIP net.IP, mask int)

// mask, client's IP address and question's name of m.  ecsIP is expected to be
// masked already.
func msgToKeyWithSubnet(m *dns.Msg, ecsIP net.IP, mask int) (key []byte) {
	q := m.Question[0]
	keyLen := keyIPIndex + len(q.Name)
	masked := mask != 0
	if masked {
		keyLen += len(ecsIP)
	}

	// Initialize the slice.
	key = make([]byte, keyLen)

	// Put DO.
	opt := m.IsEdns0()
	key[0] = mathutil.BoolToNumber[byte](opt != nil && opt.Do())

	// Put Qtype.
	binary.BigEndian.PutUint16(key[1:], q.Qtype)

	// Put Qclass.
	binary.BigEndian.PutUint16(key[1+packedMsgLenSz:], q.Qclass)

	// Add mask.
	key[keyMaskIndex] = uint8(mask)
	k := keyIPIndex
	if masked {
		k += copy(key[keyIPIndex:], ecsIP)
	}

	copy(key[k:], strings.ToLower(q.Name))

	return key
}

// isDNSSEC returns true if r is a DNSSEC RR.  NSEC, NSEC3, DS, DNSKEY and
// RRSIG/SIG are DNSSEC records.