Make dns resolve paths under _dnslink.

Thus allowing to CNAME main site entry to gateway and stil specify
dnslink.

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@gmail.com>

namesys/dns.go

@@ -41,33 +41,76 @@ func (r *DNSResolver) ResolveN(ctx context.Context, name string, depth int) (pat
 	return resolve(ctx, r, name, depth, "/ipns/")
 }
 
+type lookupRes struct {
+	path  path.Path
+	error error
+}
+
 // resolveOnce implements resolver.
 // TXT records for a given domain name should contain a b58
 // encoded multihash.
 func (r *DNSResolver) resolveOnce(ctx context.Context, name string) (path.Path, error) {
 	segments := strings.SplitN(name, "/", 2)
+	domain := segments[0]
 
-	if !isd.IsDomain(segments[0]) {
+	if !isd.IsDomain(domain) {
 		return "", errors.New("not a valid domain name")
 	}
+	log.Infof("DNSResolver resolving %s", domain)
+
+	rootChan := make(chan lookupRes, 1)
+	go workDomain(r, domain, rootChan)
+
+	subChan := make(chan lookupRes, 1)
+	go workDomain(r, "_dnslink."+domain, subChan)
+
+	var subRes lookupRes
+	select {
+	case subRes = <-subChan:
+	case <-ctx.Done():
+		return "", ctx.Err()
+	}
+
+	var p path.Path
+	if subRes.error == nil {
+		p = subRes.path
+	} else {
+		var rootRes lookupRes
+		select {
+		case rootRes = <-rootChan:
+		case <-ctx.Done():
+			return "", ctx.Err()
+		}
+		if rootRes.error == nil {
+			p = rootRes.path
+		} else {
+			return "", ErrResolveFailed
+		}
+	}
+	if len(segments) > 1 {
+		return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[1])
+	} else {
+		return p, nil
+	}
+}
+
+func workDomain(r *DNSResolver, name string, res chan lookupRes) {
+	txt, err := r.lookupTXT(name)
 
-	log.Infof("DNSResolver resolving %s", segments[0])
-	txt, err := r.lookupTXT(segments[0])
 	if err != nil {
-		return "", err
+		// Error is != nil
+		res <- lookupRes{"", err}
+		return
 	}
 
 	for _, t := range txt {
 		p, err := parseEntry(t)
 		if err == nil {
-			if len(segments) > 1 {
-				return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[1])
-			}
-			return p, nil
+			res <- lookupRes{p, nil}
+			return
 		}
 	}
-
-	return "", ErrResolveFailed
+	res <- lookupRes{"", ErrResolveFailed}
 }
 
 func parseEntry(txt string) (path.Path, error) {

namesys/dns_test.go

@@ -65,6 +65,9 @@ func newMockDNS() *mockDNS {
 			"ipfs.example.com": []string{
 				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD",
 			},
+			"_dnslink.dipfs.example.com": []string{
+				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD",
+			},
 			"dns1.example.com": []string{
 				"dnslink=/ipns/ipfs.example.com",
 			},
@@ -85,6 +88,12 @@ func newMockDNS() *mockDNS {
 			"loop2.example.com": []string{
 				"dnslink=/ipns/loop1.example.com",
 			},
+			"_dnslink.dloop1.example.com": []string{
+				"dnslink=/ipns/loop2.example.com",
+			},
+			"_dnslink.dloop2.example.com": []string{
+				"dnslink=/ipns/loop1.example.com",
+			},
 			"bad.example.com": []string{
 				"dnslink=",
 			},
@@ -100,6 +109,18 @@ func newMockDNS() *mockDNS {
 			"withtrailingrec.example.com": []string{
 				"dnslink=/ipns/withtrailing.example.com/segment/",
 			},
+			"double.example.com": []string{
+				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD",
+			},
+			"_dnslink.double.example.com": []string{
+				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD",
+			},
+			"double.conflict.com": []string{
+				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD",
+			},
+			"_dnslink.conflict.example.com": []string{
+				"dnslink=/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjE",
+			},
 		},
 	}
 }
@@ -109,6 +130,7 @@ func TestDNSResolution(t *testing.T) {
 	r := &DNSResolver{lookupTXT: mock.lookupTXT}
 	testResolution(t, r, "multihash.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
 	testResolution(t, r, "ipfs.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
+	testResolution(t, r, "dipfs.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
 	testResolution(t, r, "dns1.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
 	testResolution(t, r, "dns1.example.com", 1, "/ipns/ipfs.example.com", ErrResolveRecursion)
 	testResolution(t, r, "dns2.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
@@ -122,6 +144,10 @@ func TestDNSResolution(t *testing.T) {
 	testResolution(t, r, "loop1.example.com", 2, "/ipns/loop1.example.com", ErrResolveRecursion)
 	testResolution(t, r, "loop1.example.com", 3, "/ipns/loop2.example.com", ErrResolveRecursion)
 	testResolution(t, r, "loop1.example.com", DefaultDepthLimit, "/ipns/loop1.example.com", ErrResolveRecursion)
+	testResolution(t, r, "dloop1.example.com", 1, "/ipns/loop2.example.com", ErrResolveRecursion)
+	testResolution(t, r, "dloop1.example.com", 2, "/ipns/loop1.example.com", ErrResolveRecursion)
+	testResolution(t, r, "dloop1.example.com", 3, "/ipns/loop2.example.com", ErrResolveRecursion)
+	testResolution(t, r, "dloop1.example.com", DefaultDepthLimit, "/ipns/loop1.example.com", ErrResolveRecursion)
 	testResolution(t, r, "bad.example.com", DefaultDepthLimit, "", ErrResolveFailed)
 	testResolution(t, r, "withsegment.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD/sub/segment", nil)
 	testResolution(t, r, "withrecsegment.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD/sub/segment/subsub", nil)
@@ -129,4 +155,6 @@ func TestDNSResolution(t *testing.T) {
 	testResolution(t, r, "withrecsegment.example.com/test2", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD/sub/segment/subsub/test2", nil)
 	testResolution(t, r, "withrecsegment.example.com/test3/", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD/sub/segment/subsub/test3/", nil)
 	testResolution(t, r, "withtrailingrec.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD/sub/segment/", nil)
+	testResolution(t, r, "double.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjD", nil)
+	testResolution(t, r, "conflict.example.com", DefaultDepthLimit, "/ipfs/QmY3hE8xgFCjGcz6PHgnvJz5HZi1BaKRfPkn1ghZUcYMjE", nil)
 }