package dns import ( "encoding/binary" "strings" "time" "github.com/xtls/xray-core/common" "github.com/xtls/xray-core/common/errors" "github.com/xtls/xray-core/common/net" dns_feature "github.com/xtls/xray-core/features/dns" "golang.org/x/net/dns/dnsmessage" ) // Fqdn normalize domain make sure it ends with '.' func Fqdn(domain string) string { if len(domain) > 0 && strings.HasSuffix(domain, ".") { return domain } return domain + "." } type record struct { A *IPRecord AAAA *IPRecord } // IPRecord is a cacheable item for a resolved domain type IPRecord struct { ReqID uint16 IP []net.Address Expire time.Time RCode dnsmessage.RCode } func (r *IPRecord) getIPs() ([]net.Address, error) { if r == nil || r.Expire.Before(time.Now()) { return nil, errRecordNotFound } if r.RCode != dnsmessage.RCodeSuccess { return nil, dns_feature.RCodeError(r.RCode) } return r.IP, nil } func isNewer(baseRec *IPRecord, newRec *IPRecord) bool { if newRec == nil { return false } if baseRec == nil { return true } return baseRec.Expire.Before(newRec.Expire) } var ( errRecordNotFound = errors.New("record not found") ) type dnsRequest struct { reqType dnsmessage.Type domain string start time.Time expire time.Time msg *dnsmessage.Message } func genEDNS0Options(clientIP net.IP) *dnsmessage.Resource { if len(clientIP) == 0 { return nil } var netmask int var family uint16 if len(clientIP) == 4 { family = 1 netmask = 24 // 24 for IPV4, 96 for IPv6 } else { family = 2 netmask = 96 } b := make([]byte, 4) binary.BigEndian.PutUint16(b[0:], family) b[2] = byte(netmask) b[3] = 0 switch family { case 1: ip := clientIP.To4().Mask(net.CIDRMask(netmask, net.IPv4len*8)) needLength := (netmask + 8 - 1) / 8 // division rounding up b = append(b, ip[:needLength]...) case 2: ip := clientIP.Mask(net.CIDRMask(netmask, net.IPv6len*8)) needLength := (netmask + 8 - 1) / 8 // division rounding up b = append(b, ip[:needLength]...) } const EDNS0SUBNET = 0x08 opt := new(dnsmessage.Resource) common.Must(opt.Header.SetEDNS0(1350, 0xfe00, true)) opt.Body = &dnsmessage.OPTResource{ Options: []dnsmessage.Option{ { Code: EDNS0SUBNET, Data: b, }, }, } return opt } func buildReqMsgs(domain string, option dns_feature.IPOption, reqIDGen func() uint16, reqOpts *dnsmessage.Resource) []*dnsRequest { qA := dnsmessage.Question{ Name: dnsmessage.MustNewName(domain), Type: dnsmessage.TypeA, Class: dnsmessage.ClassINET, } qAAAA := dnsmessage.Question{ Name: dnsmessage.MustNewName(domain), Type: dnsmessage.TypeAAAA, Class: dnsmessage.ClassINET, } var reqs []*dnsRequest now := time.Now() if option.IPv4Enable { msg := new(dnsmessage.Message) msg.Header.ID = reqIDGen() msg.Header.RecursionDesired = true msg.Questions = []dnsmessage.Question{qA} if reqOpts != nil { msg.Additionals = append(msg.Additionals, *reqOpts) } reqs = append(reqs, &dnsRequest{ reqType: dnsmessage.TypeA, domain: domain, start: now, msg: msg, }) } if option.IPv6Enable { msg := new(dnsmessage.Message) msg.Header.ID = reqIDGen() msg.Header.RecursionDesired = true msg.Questions = []dnsmessage.Question{qAAAA} if reqOpts != nil { msg.Additionals = append(msg.Additionals, *reqOpts) } reqs = append(reqs, &dnsRequest{ reqType: dnsmessage.TypeAAAA, domain: domain, start: now, msg: msg, }) } return reqs } // parseResponse parse DNS answers from the returned payload func parseResponse(payload []byte) (*IPRecord, error) { var parser dnsmessage.Parser h, err := parser.Start(payload) if err != nil { return nil, newError("failed to parse DNS response").Base(err).AtWarning() } if err := parser.SkipAllQuestions(); err != nil { return nil, newError("failed to skip questions in DNS response").Base(err).AtWarning() } now := time.Now() ipRecord := &IPRecord{ ReqID: h.ID, RCode: h.RCode, Expire: now.Add(time.Second * 600), } L: for { ah, err := parser.AnswerHeader() if err != nil { if err != dnsmessage.ErrSectionDone { newError("failed to parse answer section for domain: ", ah.Name.String()).Base(err).WriteToLog() } break } ttl := ah.TTL if ttl == 0 { ttl = 600 } expire := now.Add(time.Duration(ttl) * time.Second) if ipRecord.Expire.After(expire) { ipRecord.Expire = expire } switch ah.Type { case dnsmessage.TypeA: ans, err := parser.AResource() if err != nil { newError("failed to parse A record for domain: ", ah.Name).Base(err).WriteToLog() break L } ipRecord.IP = append(ipRecord.IP, net.IPAddress(ans.A[:])) case dnsmessage.TypeAAAA: ans, err := parser.AAAAResource() if err != nil { newError("failed to parse A record for domain: ", ah.Name).Base(err).WriteToLog() break L } ipRecord.IP = append(ipRecord.IP, net.IPAddress(ans.AAAA[:])) default: if err := parser.SkipAnswer(); err != nil { newError("failed to skip answer").Base(err).WriteToLog() break L } continue } } return ipRecord, nil }