Fix Port Conflict Error (#1033)

(closes #831 )

* Added ports pre checking

To find out whether they are being used by other applications.

* Check which process is using target port, if any

* Moved excludeWhitespace() function to util package

cmd/cmd_pkg.go

@@ -217,7 +217,6 @@ func loadCommandHandler(cmd *cobra.Command, args []string) {
 	buildImageFlags := NewBuildImageCommandFlags(flags)
 	runLocalInstanceFlags := NewRunLocalInstanceCommandFlags(flags)
 	pkgFlags := NewPkgCommandFlags(flags)
-
 	pkgFlags.Package = args[0]
 
 	c := lepton.NewConfig()

cmd/cmd_root.go

@@ -14,21 +14,20 @@ func GetRootCommand() *cobra.Command {
 	var rootCmd = &cobra.Command{
 		Use: "ops",
 		PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
-			var config *types.Config
+			config := &types.Config{}
 
 			configFlag, _ := cmd.Flags().GetString("config")
 			configFlag = strings.TrimSpace(configFlag)
 
 			if configFlag != "" {
-				config := &types.Config{}
 				if err := unWarpConfig(configFlag, config); err != nil {
 					return err
 				}
+			}
 
-				globalFlags := NewGlobalCommandFlags(cmd.Flags())
-				if err := globalFlags.MergeToConfig(config); err != nil {
-					return err
-				}
+			globalFlags := NewGlobalCommandFlags(cmd.Flags())
+			if err := globalFlags.MergeToConfig(config); err != nil {
+				return err
 			}
 
 			log.InitDefault(os.Stdout, config)

cmd/flags_run_local_instance.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"strconv"
+	"time"
 
 	"github.com/nanovms/ops/types"
 
@@ -32,7 +33,7 @@ type RunLocalInstanceCommandFlags struct {
 }
 
 // MergeToConfig overrides configuration passed by argument with command flags values
-func (flags *RunLocalInstanceCommandFlags) MergeToConfig(c *types.Config) (err error) {
+func (flags *RunLocalInstanceCommandFlags) MergeToConfig(c *types.Config) error {
 	c.Debugflags = []string{}
 
 	if flags.Trace {
@@ -46,9 +47,9 @@ func (flags *RunLocalInstanceCommandFlags) MergeToConfig(c *types.Config) (err e
 
 		var elfFile *elf.File
 
-		elfFile, err = api.GetElfFileInfo(c.ProgramPath)
+		elfFile, err := api.GetElfFileInfo(c.ProgramPath)
 		if err != nil {
-			return
+			return err
 		}
 
 		if api.IsDynamicLinked(elfFile) {
@@ -91,8 +92,7 @@ func (flags *RunLocalInstanceCommandFlags) MergeToConfig(c *types.Config) (err e
 
 	ports, err := PrepareNetworkPorts(flags.Ports)
 	if err != nil {
-		exitWithError(err.Error())
-		return
+		return err
 	}
 
 	for _, p := range ports {
@@ -116,7 +116,28 @@ func (flags *RunLocalInstanceCommandFlags) MergeToConfig(c *types.Config) (err e
 
 	}
 
-	return
+	for _, port := range flags.Ports {
+		conn, err := net.DialTimeout("tcp", ":"+port, time.Second)
+		if err != nil {
+			continue // assume port is not being used
+		}
+
+		if conn != nil {
+			conn.Close()
+
+			message := fmt.Sprintf("Port %v is being used by other application", port)
+			pid, err := checkPortUserPID(port)
+			if err != nil {
+				return err
+			}
+			if pid != "" {
+				message += fmt.Sprintf(" (PID %s)", pid)
+			}
+			return errors.New(message)
+		}
+	}
+
+	return nil
 }
 
 // NewRunLocalInstanceCommandFlags returns an instance of RunLocalInstanceCommandFlags initialized with command flags values

cmd/flags_run_local_instance_unix.go

@@ -0,0 +1,41 @@
+package cmd
+
+import (
+	"bufio"
+	"os/exec"
+	"strings"
+
+	"github.com/nanovms/ops/util/slice"
+)
+
+// Checks which process is using given port number
+func checkPortUserPID(portNumber string) (string, error) {
+	var (
+		pid string
+		cmd = exec.Command("lsof", "-i", ":"+portNumber)
+	)
+	out, err := cmd.Output()
+	if err != nil {
+		return pid, err
+	}
+
+	scanner := bufio.NewScanner(strings.NewReader(string(out)))
+	scanner.Scan() // check header first
+	cols := slice.ExcludeWhitespaces(strings.Split(scanner.Text(), " "))
+	headerIdx := -1
+	for i, v := range cols {
+		if strings.ToLower(v) == "pid" {
+			headerIdx = i
+			break
+		}
+	}
+
+	scanner.Scan()
+	line := strings.Trim(scanner.Text(), " ")
+	if line != "" {
+		cols = slice.ExcludeWhitespaces(strings.Split(line, " "))
+		pid = cols[headerIdx]
+	}
+
+	return pid, err
+}

util/slice/string.go

@@ -0,0 +1,15 @@
+package slice
+
+import "strings"
+
+// ExcludeWhitespaces removes whitespaces from given slice
+func ExcludeWhitespaces(arr []string) []string {
+	result := make([]string, 0)
+	for _, h := range arr {
+		if strings.Trim(h, " ") == "" {
+			continue
+		}
+		result = append(result, h)
+	}
+	return result
+}

util/slice/string_test.go

@@ -0,0 +1,24 @@
+package slice
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestExcludeWhitespaces(t *testing.T) {
+	arr := []string{
+		"lorem", "ipsum", " ", "dolor", "", "sit", "amet",
+	}
+	trimmed := ExcludeWhitespaces(arr)
+	for _, v := range trimmed {
+		if v == "" {
+			t.Error("found unstripped whice space")
+		}
+	}
+
+	expected := "lorem,ipsum,dolor,sit,amet"
+	str := strings.Join(trimmed, ",")
+	if str != expected {
+		t.Errorf("expected '%s', got '%s'", expected, str)
+	}
+}