routers: Fix a crash while initializing network fs. (#1382)

Crash happens when 'minio server filename' a file name is
provided instead of a directory on command line argument.

```
panic: runtime error: slice bounds out of range

goroutine 1 [running]:
panic(0x5eb460, 0xc82000e0b0)
	/usr/local/opt/go/libexec/src/runtime/panic.go:464 +0x3e6
main.splitNetPath(0x7fff5fbff9bd, 0x7, 0x0, 0x0, 0x0, 0x0)
	/Users/harsha/mygo/src/github.com/minio/minio/network-fs.go:49 +0xb7
main.newNetworkFS(0x7fff5fbff9bd, 0x7, 0x0, 0x0, 0x0, 0x0)
	/Users/harsha/mygo/src/github.com/minio/minio/network-fs.go:90 +0x20a
main.configureServerHandler(0xc82024e1c8, 0x5, 0xc8200640e0, 0x1, 0x1, 0x0, 0x0)
	/Users/harsha/mygo/src/github.com/minio/minio/routers.go:43 +0x6ce
main.configureServer(0xc82024e1c8, 0x5, 0xc8200640e0, 0x1, 0x1, 0x5)
	/Users/harsha/mygo/src/github.com/minio/minio/server-main.go:86 +0x67
```

network-fs.go

@@ -79,7 +79,7 @@ func toStorageErr(err error) error {
 // Initialize new network file system.
 func newNetworkFS(networkPath string) (StorageAPI, error) {
 	// Input validation.
-	if networkPath == "" && strings.LastIndex(networkPath, ":") != -1 {
+	if networkPath == "" || strings.LastIndex(networkPath, ":") == -1 {
 		log.WithFields(logrus.Fields{
 			"networkPath": networkPath,
 		}).Debugf("Network path is malformed, should be of form <ip>:<port>:<export_dir>")

object-api_test.go

@@ -32,7 +32,8 @@ func (s *MySuite) TestFSAPISuite(c *C) {
 	create := func() objectAPI {
 		path, err := ioutil.TempDir(os.TempDir(), "minio-")
 		c.Check(err, IsNil)
-		storageAPI, err := newFS(path)
+		storageAPI, err := newStorageAPI(path)
+		c.Check(err, IsNil)
 		objAPI := newObjectLayer(storageAPI)
 		storageList = append(storageList, path)
 		return objAPI
@@ -52,7 +53,7 @@ func (s *MySuite) TestXLAPISuite(c *C) {
 			erasureDisks = append(erasureDisks, path)
 		}
 		storageList = append(storageList, erasureDisks...)
-		storageAPI, err := newXL(erasureDisks...)
+		storageAPI, err := newStorageAPI(erasureDisks...)
 		c.Check(err, IsNil)
 		objAPI := newObjectLayer(storageAPI)
 		return objAPI

routers.go

@@ -17,40 +17,33 @@
 package main
 
 import (
-	"errors"
 	"net/http"
-	"os"
-	"runtime"
+	"path/filepath"
+	"strings"
 
 	router "github.com/gorilla/mux"
 	"github.com/minio/minio/pkg/probe"
 )
 
+// newStorageAPI - initialize any storage API depending on the export path style.
+func newStorageAPI(exportPaths ...string) (StorageAPI, error) {
+	if len(exportPaths) == 1 {
+		exportPath := exportPaths[0]
+		if !strings.ContainsRune(exportPath, ':') || filepath.VolumeName(exportPath) != "" {
+			// Initialize filesystem storage API.
+			return newFS(exportPath)
+		}
+		// Initialize network storage API.
+		return newNetworkFS(exportPath)
+	}
+	// Initialize XL storage API.
+	return newXL(exportPaths...)
+}
+
 // configureServer handler returns final handler for the http server.
 func configureServerHandler(srvCmdConfig serverCmdConfig) http.Handler {
-	var storageAPI StorageAPI
-	var e error
-	if len(srvCmdConfig.exportPaths) == 1 {
-		// Verify if export path is a local file system path.
-		var st os.FileInfo
-		st, e = os.Stat(srvCmdConfig.exportPaths[0])
-		if e == nil && st.Mode().IsDir() {
-			// Initialize storage API.
-			storageAPI, e = newFS(srvCmdConfig.exportPaths[0])
-			fatalIf(probe.NewError(e), "Initializing fs failed.", nil)
-		} else {
-			// Initialize network storage API.
-			storageAPI, e = newNetworkFS(srvCmdConfig.exportPaths[0])
-			fatalIf(probe.NewError(e), "Initializing network fs failed.", nil)
-		}
-	} else {
-		if runtime.GOOS == "windows" {
-			fatalIf(probe.NewError(errors.New("")), "Initializing XL failed, not supported on windows yet.", nil)
-		}
-		// Initialize XL storage API.
-		storageAPI, e = newXL(srvCmdConfig.exportPaths...)
-		fatalIf(probe.NewError(e), "Initializing XL failed.", nil)
-	}
+	storageAPI, e := newStorageAPI(srvCmdConfig.exportPaths...)
+	fatalIf(probe.NewError(e), "Initializing storage API failed.", nil)
 
 	// Initialize object layer.
 	objAPI := newObjectLayer(storageAPI)

server-main.go

@@ -162,7 +162,7 @@ func initServerConfig(c *cli.Context) {
 
 // Check server arguments.
 func checkServerSyntax(c *cli.Context) {
-	if !c.Args().Present() && c.Args().First() == "help" {
+	if !c.Args().Present() || c.Args().First() == "help" {
 		cli.ShowCommandHelpAndExit(c, "server", 1)
 	}
 }