v1.0.0

app/dns/dnscommon.go

@@ -0,0 +1,230 @@
+// +build !confonly
+
+package dns
+
+import (
+	"encoding/binary"
+	"time"
+
+	"github.com/xtls/xray-core/v1/common"
+	"github.com/xtls/xray-core/v1/common/errors"
+	"github.com/xtls/xray-core/v1/common/net"
+	dns_feature "github.com/xtls/xray-core/v1/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 && domain[len(domain)-1] == '.' {
+		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 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
+}