dns: imporve dns client to be compatible with upstream dnsmasq servers

dns.go

@@ -4,7 +4,7 @@ package main
 
 import (
 	"encoding/binary"
-	"io/ioutil"
+	"io"
 	"net"
 	"strings"
 )
@@ -98,13 +98,11 @@ func (s *DNS) ListenAndServe() {
 		data = data[:n]
 
 		go func() {
-			// TODO: check domain rules and get a proper upstream name server.
 			query := parseQuery(data)
 			domain := query.DomainName
 
 			dnsServer := s.GetServer(domain)
 
-			// TODO: check here; ADD dnsServer to rule ip lists
 			rc, err := s.sDialer.NextDialer(domain+":53").Dial("tcp", dnsServer)
 			if err != nil {
 				logf("failed to connect to server %v: %v", dnsServer, err)
@@ -113,26 +111,36 @@ func (s *DNS) ListenAndServe() {
 			defer rc.Close()
 
 			// 2 bytes length after tcp header, before dns message
-			length := make([]byte, 2)
-			binary.BigEndian.PutUint16(length, uint16(len(data)))
-			rc.Write(length)
+			reqLen := make([]byte, 2)
+			binary.BigEndian.PutUint16(reqLen, uint16(len(data)))
+			rc.Write(reqLen)
 			rc.Write(data)
 
-			resp, err := ioutil.ReadAll(rc)
+			// fmt.Printf("dns req len %d:\n%s\n\n", reqLen, hex.Dump(data[:]))
+
+			var respLen uint16
+			err = binary.Read(rc, binary.BigEndian, &respLen)
 			if err != nil {
-				logf("error in ioutil.ReadAll: %s\n", err)
+				logf("proxy-dns: error in read respLen %s\n", err)
 				return
 			}
 
+			respMsg := make([]byte, respLen)
+			_, err = io.ReadFull(rc, respMsg)
+			if err != nil {
+				logf("proxy-dns: error in read respMsg %s\n", err)
+				return
+			}
+
+			// fmt.Printf("dns resp len %d:\n%s\n\n", respLen, hex.Dump(respMsg[:]))
+
 			var ip string
 			// length is not needed in udp dns response. (2 bytes)
 			// SEE RFC1035, section 4.2.2 TCP: The message is prefixed with a two byte length field which gives the message length, excluding the two byte length field.
-			if len(resp) > 2 {
-				msg := resp[2:]
-				// TODO: Get IP from response, check and add to ipset
-				query := parseQuery(msg)
-				if len(msg) > query.Offset {
-					answers := parseAnswers(msg[query.Offset:])
+			if respLen > 0 {
+				query := parseQuery(respMsg)
+				if len(respMsg) > query.Offset {
+					answers := parseAnswers(respMsg[query.Offset:])
 					for _, answer := range answers {
 						if answer.IP != "" {
 							ip += answer.IP + ","
@@ -146,7 +154,7 @@ func (s *DNS) ListenAndServe() {
 
 				}
 
-				_, err = c.WriteTo(msg, clientAddr)
+				_, err = c.WriteTo(respMsg, clientAddr)
 				if err != nil {
 					logf("error in local write: %s\n", err)
 				}

main.go

@@ -9,7 +9,7 @@ import (
 )
 
 // VERSION .
-const VERSION = "0.4.2"
+const VERSION = "0.4.3"
 
 func dialerFromConf() Dialer {
 	// global forwarders in xx.conf

rule.go

@@ -61,7 +61,6 @@ func (rd *RuleDialer) Addr() string { return "RULES" }
 // NextDialer return next dialer according to rule
 func (rd *RuleDialer) NextDialer(dstAddr string) Dialer {
 
-	// TODO: change to index finders
 	host, _, err := net.SplitHostPort(dstAddr)
 	if err != nil {
 		// TODO: check here