Cleanup ParseHostOrFile (#2100)

Create plugin/pkg/transport that holds the transport related functions.
This needed to be a new pkg to prevent cyclic import errors.

This cleans up a bunch of duplicated code in core/dnsserver that also
tried to parse a transport (now all done in transport.Parse).

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/pkg/dnsutil/host.go

@@ -5,15 +5,21 @@ import (
 	"net"
 	"os"
 
+	"github.com/coredns/coredns/plugin/pkg/transport"
+
 	"github.com/miekg/dns"
 )
 
-// ParseHostPortOrFile parses the strings in s, each string can either be a address,
-// address:port or a filename. The address part is checked and the filename case a
-// resolv.conf like file is parsed and the nameserver found are returned.
+// ParseHostPortOrFile parses the strings in s, each string can either be a
+// address, [scheme://]address:port or a filename. The address part is checked
+// and in case of filename a resolv.conf like file is (assumed) and parsed and
+// the nameservers found are returned.
 func ParseHostPortOrFile(s ...string) ([]string, error) {
 	var servers []string
-	for _, host := range s {
+	for _, h := range s {
+
+		trans, host := transport.Parse(h)
+
 		addr, _, err := net.SplitHostPort(host)
 		if err != nil {
 			// Parse didn't work, it is not a addr:port combo
@@ -26,13 +32,23 @@ func ParseHostPortOrFile(s ...string) ([]string, error) {
 				}
 				return servers, fmt.Errorf("not an IP address or file: %q", host)
 			}
-			ss := net.JoinHostPort(host, "53")
+			var ss string
+			switch trans {
+			case transport.DNS:
+				ss = net.JoinHostPort(host, "53")
+			case transport.TLS:
+				ss = transport.TLS + "://" + net.JoinHostPort(host, transport.TLSPort)
+			case transport.GRPC:
+				ss = transport.GRPC + "://" + net.JoinHostPort(host, transport.GRPCPort)
+			case transport.HTTPS:
+				ss = transport.HTTPS + "://" + net.JoinHostPort(host, transport.HTTPSPort)
+			}
 			servers = append(servers, ss)
 			continue
 		}
 
 		if net.ParseIP(addr) == nil {
-			// No an IP address.
+			// Not an IP address.
 			ss, err := tryFile(host)
 			if err == nil {
 				servers = append(servers, ss...)
@@ -40,7 +56,7 @@ func ParseHostPortOrFile(s ...string) ([]string, error) {
 			}
 			return servers, fmt.Errorf("not an IP address or file: %q", host)
 		}
-		servers = append(servers, host)
+		servers = append(servers, h)
 	}
 	return servers, nil
 }

plugin/pkg/transport/transport.go

@@ -0,0 +1,49 @@
+package transport
+
+import (
+	"strings"
+)
+
+// Parse returns the transport defined in s and a string where the
+// transport prefix is removed (if there was any). If no transport is defined
+// we default to TransportDNS
+func Parse(s string) (transport string, addr string) {
+	switch {
+	case strings.HasPrefix(s, TLS+"://"):
+		s = s[len(TLS+"://"):]
+		return TLS, s
+
+	case strings.HasPrefix(s, DNS+"://"):
+		s = s[len(DNS+"://"):]
+		return DNS, s
+
+	case strings.HasPrefix(s, GRPC+"://"):
+		s = s[len(GRPC+"://"):]
+		return GRPC, s
+
+	case strings.HasPrefix(s, HTTPS+"://"):
+		s = s[len(HTTPS+"://"):]
+
+		return HTTPS, s
+	}
+
+	return DNS, s
+}
+
+// Supported transports.
+const (
+	DNS   = "dns"
+	TLS   = "tls"
+	GRPC  = "grpc"
+	HTTPS = "https"
+)
+
+// Port numbers for the various protocols
+const (
+	// TLSPort is the default port for DNS-over-TLS.
+	TLSPort = "853"
+	// GRPCPort is the default port for DNS-over-gRPC.
+	GRPCPort = "443"
+	// HTTPSPort is the default port for DNS-over-HTTPS.
+	HTTPSPort = "443"
+)

plugin/pkg/transport/transport_test.go

@@ -0,0 +1,21 @@
+package transport
+
+import "testing"
+
+func TestParse(t *testing.T) {
+	for i, test := range []struct {
+		input    string
+		expected string
+	}{
+		{"dns://.:53", DNS},
+		{"2003::1/64.:53", DNS},
+		{"grpc://example.org:1443 ", GRPC},
+		{"tls://example.org ", TLS},
+		{"https://example.org ", HTTPS},
+	} {
+		actual, _ := Parse(test.input)
+		if actual != test.expected {
+			t.Errorf("Test %d: Expected %s but got %s", i, test.expected, actual)
+		}
+	}
+}