dns: add experimental codes to specify different remote dns server in rule file

dns.go

@@ -6,6 +6,7 @@ import (
 	"encoding/binary"
 	"io/ioutil"
 	"net"
+	"strings"
 )
 
 // UDPDNSHeaderLen is the length of UDP dns msg header
@@ -23,23 +24,26 @@ const TCPDNSHEADERLen = 2 + UDPDNSHeaderLen
 // so we should also serve tcp requests.
 const MaxUDPDNSLen = 512
 
-type dns struct {
+type DNS struct {
 	*proxy
-	raddr string
+	dnsServer string
+
+	dnsServerMap map[string]string
 }
 
 // DNSForwarder returns a dns forwarder. client -> dns.udp -> glider -> forwarder -> remote dns addr
-func DNSForwarder(addr, raddr string, upProxy Proxy) (Proxy, error) {
-	s := &dns{
-		proxy: newProxy(addr, upProxy),
-		raddr: raddr,
+func DNSForwarder(addr, raddr string, upProxy Proxy) (*DNS, error) {
+	s := &DNS{
+		proxy:        newProxy(addr, upProxy),
+		dnsServer:    raddr,
+		dnsServerMap: make(map[string]string),
 	}
 
 	return s, nil
 }
 
 // ListenAndServe .
-func (s *dns) ListenAndServe() {
+func (s *DNS) ListenAndServe() {
 	l, err := net.ListenPacket("udp", s.addr)
 	if err != nil {
 		logf("failed to listen on %s: %v", s.addr, err)
@@ -62,16 +66,18 @@ func (s *dns) ListenAndServe() {
 
 		go func() {
 			// TODO: check domain rules and get a proper upstream name server.
-			domain := getDomain(data)
+			domain := string(getDomain(data))
 
-			rc, err := s.GetProxy(s.raddr).Dial("tcp", s.raddr)
+			dnsServer := s.GetServer(domain)
+			// TODO: check here
+			rc, err := s.GetProxy(domain+":53").GetProxy(domain+":53").Dial("tcp", dnsServer)
 			if err != nil {
-				logf("failed to connect to server %v: %v", s.raddr, err)
+				logf("failed to connect to server %v: %v", dnsServer, err)
 				return
 			}
 			defer rc.Close()
 
-			logf("proxy-dns %s, %s <-> %s", domain, clientAddr.String(), s.raddr)
+			logf("proxy-dns %s, %s <-> %s", domain, clientAddr.String(), dnsServer)
 
 			// 2 bytes length after tcp header, before dns message
 			length := make([]byte, 2)
@@ -99,6 +105,27 @@ func (s *dns) ListenAndServe() {
 	}
 }
 
+// SetServer .
+func (s *DNS) SetServer(domain, server string) {
+	s.dnsServerMap[domain] = server
+}
+
+// GetServer .
+func (s *DNS) GetServer(domain string) string {
+
+	domainParts := strings.Split(domain, ".")
+	length := len(domainParts)
+	for i := length - 2; i >= 0; i-- {
+		domain := strings.Join(domainParts[i:length], ".")
+
+		if server, ok := s.dnsServerMap[domain]; ok {
+			return server
+		}
+	}
+
+	return s.dnsServer
+}
+
 // getDomain from dns request playload, return []byte like:
 // []byte{'w', 'w', 'w', '.', 'm', 's', 'n', '.', 'c', 'o', 'm', '.'}
 // []byte("www.msn.com.")

main.go

@@ -22,6 +22,11 @@ var conf struct {
 	Listen        []string
 	Forward       []string
 	RuleFile      []string
+
+	DNS       string
+	DNSServer []string
+
+	IPSet string
 }
 
 var flag = conflag.New()
@@ -118,6 +123,11 @@ func main() {
 	flag.StringSliceUniqVar(&conf.Forward, "forward", nil, "forward url, format: SCHEMA://[USER|METHOD:PASSWORD@][HOST]:PORT[,SCHEMA://[USER|METHOD:PASSWORD@][HOST]:PORT]")
 	flag.StringSliceUniqVar(&conf.RuleFile, "rulefile", nil, "rule file path")
 
+	flag.StringVar(&conf.DNS, "dns", "", "dns listen address")
+	flag.StringSliceUniqVar(&conf.DNSServer, "dnsserver", []string{"8.8.8.8:53"}, "remote dns server")
+
+	flag.StringVar(&conf.IPSet, "ipset", "glider", "ipset name")
+
 	flag.Usage = usage
 	err := flag.Parse()
 	if err != nil {
@@ -125,7 +135,7 @@ func main() {
 		return
 	}
 
-	if len(conf.Listen) == 0 {
+	if len(conf.Listen) == 0 && conf.DNS == "" {
 		flag.Usage()
 		fmt.Fprintf(os.Stderr, "ERROR: listen url must be specified.\n")
 		return
@@ -177,6 +187,24 @@ func main() {
 		}
 	}
 
+	if conf.DNS != "" {
+		dns, err := DNSForwarder(conf.DNS, conf.DNSServer[0], forwarder)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		// rule
+		for _, frwder := range ruleForwarders {
+			for _, domain := range frwder.Domain {
+				if len(frwder.DNSServer) > 0 {
+					dns.SetServer(domain, frwder.DNSServer[0])
+				}
+			}
+		}
+
+		go dns.ListenAndServe()
+	}
+
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
 	<-sigCh

rule.go

@@ -16,6 +16,9 @@ type ruleForwarder struct {
 	CheckWebSite  string
 	CheckDuration int
 
+	DNSServer []string
+	IPSet     string
+
 	Domain []string
 	IP     []string
 	CIDR   []string
@@ -34,6 +37,9 @@ func newRuleProxyFromFile(ruleFile string) (*ruleForwarder, error) {
 	f.StringVar(&p.CheckWebSite, "checkwebsite", "www.apple.com", "proxy check HTTP(NOT HTTPS) website address, format: HOST[:PORT], default port: 80")
 	f.IntVar(&p.CheckDuration, "checkduration", 30, "proxy check duration(seconds)")
 
+	f.StringSliceUniqVar(&p.DNSServer, "dnsserver", nil, "remote dns server")
+	f.StringVar(&p.IPSet, "ipset", "", "ipset name")
+
 	f.StringSliceUniqVar(&p.Domain, "domain", nil, "domain")
 	f.StringSliceUniqVar(&p.IP, "ip", nil, "ip")
 	f.StringSliceUniqVar(&p.CIDR, "cidr", nil, "cidr")

rules.go

@@ -42,7 +42,7 @@ func newRulesForwarder(ruleForwarders []*ruleForwarder, globalForwarder Proxy) P
 	return p
 }
 
-func (p *rulesForwarder) Addr() string        { return "rule forwarder" }
+func (p *rulesForwarder) Addr() string        { return "rules forwarder" }
 func (p *rulesForwarder) ListenAndServe()     {}
 func (p *rulesForwarder) Serve(c net.Conn)    {}
 func (p *rulesForwarder) CurrentProxy() Proxy { return p.globalForwarder.CurrentProxy() }