vendor: Replace github.com/jackpal/gateway with github.com/calmh/gateway (fixes #3142)

Switch to my forked version which contains a fix for this issue. I'll
track upstream in the future if things update there, and attempt to
contribute back fixes...

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3149

vendor/github.com/calmh/gateway/gateway_common.go

@@ -2,25 +2,13 @@ package gateway
 
 import (
 	"bytes"
-	"io/ioutil"
+	"errors"
 	"net"
-	"os/exec"
 )
 
-func DiscoverGateway() (ip net.IP, err error) {
-	routeCmd := exec.Command("route", "print", "0.0.0.0")
-	stdOut, err := routeCmd.StdoutPipe()
-	if err != nil {
-		return
-	}
-	if err = routeCmd.Start(); err != nil {
-		return
-	}
-	output, err := ioutil.ReadAll(stdOut)
-	if err != nil {
-		return
-	}
+var errNoGateway = errors.New("no gateway found")
 
+func parseRoutePrint(output []byte) (net.IP, error) {
 	// Windows route output format is always like this:
 	// ===========================================================================
 	// Active Routes:
@@ -33,11 +21,18 @@ func DiscoverGateway() (ip net.IP, err error) {
 	outputLines := bytes.Split(output, []byte("\n"))
 	for idx, line := range outputLines {
 		if bytes.Contains(line, []byte("Active Routes:")) {
+			if len(outputLines) <= idx+2 {
+				return nil, errNoGateway
+			}
+
 			ipFields := bytes.Fields(outputLines[idx+2])
-			ip = net.ParseIP(string(ipFields[2]))
-			break
+			if len(ipFields) < 3 {
+				return nil, errNoGateway
+			}
+
+			ip := net.ParseIP(string(ipFields[2]))
+			return ip, nil
 		}
 	}
-	err = routeCmd.Wait()
-	return
+	return nil, errNoGateway
 }

vendor/github.com/calmh/gateway/gateway_windows.go

@@ -0,0 +1,16 @@
+package gateway
+
+import (
+	"net"
+	"os/exec"
+)
+
+func DiscoverGateway() (ip net.IP, err error) {
+	routeCmd := exec.Command("route", "print", "0.0.0.0")
+	output, err := routeCmd.CombinedOutput()
+	if err != nil {
+		return nil, err
+	}
+
+	return parseRoutePrint(output)
+}

vendor/github.com/jackpal/gateway/README.md

@@ -1,7 +0,0 @@
-# gateway
-
-A very simple library for discovering the IP address of the local LAN gateway.
-
-Provides implementations for Linux, OS X (Darwin) and Windows.
-
-Pull requests for other OSs happily considered!

vendor/github.com/jackpal/gateway/gateway_test.go

@@ -1,10 +0,0 @@
-package gateway
-
-import "testing"
-
-func TestGateway(t *testing.T) {
-	ip, err := DiscoverGateway()
-	if err != nil {
-		t.Errorf("DiscoverGateway() = %v,%v", ip, err)
-	}
-}