Feature: support PTR records

Signed-off-by: Fxzx micah <[email protected]>

dns/hosts.go

@@ -8,7 +8,6 @@ import (
 	"path"
 	"runtime"
 	"strings"
-	"unicode/utf8"
 
 	"github.com/Dreamacro/clash/component/trie"
 )
@@ -18,9 +17,11 @@ func LoadHosts() *trie.DomainTrie {
 	if err != nil {
 		return nil
 	}
+	defer f.Close()
 
 	t := trie.New()
 	h := map[string][]net.IP{}
+	p := map[string][]string{}
 
 	sc := bufio.NewScanner(f)
 	for sc.Scan() {
@@ -32,10 +33,8 @@ func LoadHosts() *trie.DomainTrie {
 		}
 
 		// ignore records with non-ascii character
-		for i := 0; i < len(line); i++ {
-			if line[i] >= utf8.RuneSelf {
-				continue
-			}
+		if containNonASCII(line) {
+			continue
 		}
 
 		buf := bytes.NewBuffer([]byte(line))
@@ -54,14 +53,19 @@ func LoadHosts() *trie.DomainTrie {
 			}
 
 			h[name] = append(h[name], ip)
+			ptr := IPtoPTR(ip)
+			p[ptr] = append(p[ptr], name+".")
 		}
 	}
 
 	for name, ips := range h {
 		t.Insert(strings.ToLower(name), ips)
 	}
 
-	defer f.Close()
+	for ptr, names := range p {
+		t.Insert(ptr, names)
+	}
+
 	return t
 }
 

dns/middleware.go

@@ -25,7 +25,7 @@ func withHosts(hosts *trie.DomainTrie) middleware {
 		return func(ctx *context.DNSContext, r *D.Msg) (*D.Msg, error) {
 			q := r.Question[0]
 
-			if !isIPRequest(q) {
+			if !isIPorPTRRequest(q) {
 				return next(ctx, r)
 			}
 
@@ -35,19 +35,32 @@ func withHosts(hosts *trie.DomainTrie) middleware {
 			}
 
 			msg := r.Copy()
-			for _, data := range record.Data.([]net.IP) {
-				if v4 := data.To4(); v4 != nil && q.Qtype == D.TypeA {
-					rr := &D.A{}
-					rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeA, Class: D.ClassINET, Ttl: 10}
-					rr.A = v4
-
-					msg.Answer = append(msg.Answer, rr)
-				} else if v6 := data.To16(); v6 != nil && q.Qtype == D.TypeAAAA {
-					rr := &D.AAAA{}
-					rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeAAAA, Class: D.ClassINET, Ttl: 10}
-					rr.AAAA = v6
-
-					msg.Answer = append(msg.Answer, rr)
+			switch data := record.Data.(type) {
+			case []net.IP:
+				for _, ip := range data {
+					if v4 := ip.To4(); v4 != nil && q.Qtype == D.TypeA {
+						rr := &D.A{}
+						rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeA, Class: D.ClassINET, Ttl: 60}
+						rr.A = v4
+
+						msg.Answer = append(msg.Answer, rr)
+					} else if v6 := ip.To16(); v6 != nil && q.Qtype == D.TypeAAAA {
+						rr := &D.AAAA{}
+						rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeAAAA, Class: D.ClassINET, Ttl: 60}
+						rr.AAAA = v6
+
+						msg.Answer = append(msg.Answer, rr)
+					}
+				}
+			case []string:
+				for _, ptr := range data {
+					if q.Qtype == D.TypePTR {
+						rr := &D.PTR{}
+						rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypePTR, Class: D.ClassINET, Ttl: 60}
+						rr.Ptr = ptr
+
+						msg.Answer = append(msg.Answer, rr)
+					}
 				}
 			}
 
@@ -177,14 +190,14 @@ func compose(middlewares []middleware, endpoint handler) handler {
 func newHandler(resolver *Resolver, mapper *ResolverEnhancer) handler {
 	middlewares := []middleware{}
 
-	if resolver.hosts != nil {
-		middlewares = append(middlewares, withHosts(resolver.hosts))
-	}
-
 	if resolver.localHosts != nil {
 		middlewares = append(middlewares, withHosts(resolver.localHosts))
 	}
 
+	if resolver.hosts != nil {
+		middlewares = append(middlewares, withHosts(resolver.hosts))
+	}
+
 	if mapper.mode == C.DNSFakeIP {
 		middlewares = append(middlewares, withFakeIP(mapper.fakePool))
 	}

dns/util.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"strings"
 	"time"
+	"unicode/utf8"
 
 	"github.com/Dreamacro/clash/common/cache"
 	"github.com/Dreamacro/clash/common/picker"
@@ -57,6 +58,10 @@ func isIPRequest(q D.Question) bool {
 	return q.Qclass == D.ClassINET && (q.Qtype == D.TypeA || q.Qtype == D.TypeAAAA)
 }
 
+func isIPorPTRRequest(q D.Question) bool {
+	return q.Qclass == D.ClassINET && (q.Qtype == D.TypeA || q.Qtype == D.TypeAAAA || q.Qtype == D.TypePTR)
+}
+
 func transform(servers []NameServer, resolver *Resolver) []dnsClient {
 	ret := []dnsClient{}
 	for _, s := range servers {
@@ -141,3 +146,27 @@ func batchExchange(ctx context.Context, clients []dnsClient, m *D.Msg) (msg *D.M
 	msg = elm.(*D.Msg)
 	return
 }
+
+func containNonASCII(s string) bool {
+	for _, c := range s {
+		if c >= utf8.RuneSelf {
+			return true
+		}
+	}
+	return false
+}
+
+func IPtoPTR(ip net.IP) string {
+	if v4 := ip.To4(); v4 != nil {
+		// IPv4
+		return fmt.Sprintf("%d.%d.%d.%d.in-addr.arpa", v4[3], v4[2], v4[1], v4[0])
+	} else {
+		// IPv6
+		ptr := make([]string, len(ip)*2)
+		for i := 0; i < len(ip); i++ {
+			ptr[i*2] = fmt.Sprintf("%x", ip[len(ip)-i-1]&0xF)
+			ptr[i*2+1] = fmt.Sprintf("%x", ip[len(ip)-i-1]>>4)
+		}
+		return strings.Join(ptr, ".") + ".ip6.arpa"
+	}
+}