dnsforward -- if given addresses without ports, assign default ports

dnsforward/upstream.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"log"
 	"math/rand"
+	"net"
 	"net/http"
 	"net/url"
 	"strings"
@@ -172,16 +173,31 @@ func GetUpstream(address string) (Upstream, error) {
 		}
 		switch url.Scheme {
 		case "dns":
-			return &plainDNS{Address: address}, nil
+			if url.Port() == "" {
+				url.Host += ":53"
+			}
+			return &plainDNS{Address: url.String()}, nil
 		case "tls":
-			return &dnsOverTLS{Address: address}, nil
+			if url.Port() == "" {
+				url.Host += ":853"
+			}
+			return &dnsOverTLS{Address: url.String()}, nil
 		case "https":
-			return &dnsOverHTTPS{Address: address}, nil
+			return &dnsOverHTTPS{Address: url.String()}, nil
 		default:
-			return &plainDNS{Address: address}, nil
+			// assume it's plain DNS
+			if url.Port() == "" {
+				url.Host += ":53"
+			}
+			return &plainDNS{Address: url.String()}, nil
 		}
 	}
 
 	// we don't have scheme in the url, so it's just a plain DNS host:port
+	_, _, err := net.SplitHostPort(address)
+	if err != nil {
+		// doesn't have port, default to 53
+		address = net.JoinHostPort(address, "53")
+	}
 	return &plainDNS{Address: address}, nil
 }