Merge pull request #28 from kffl/feat/specify-network-interface

feat: add `--host` cli flag and config param

README.md

@@ -58,6 +58,8 @@ TCP proxy for simulating variable network latency.
 Flags:
   --help                  Show context-sensitive help (also try --help-long and
                           --help-man).
+  --host=""               IP or hostname to listen on. Speedbump will bind to
+                          all available network interfaces if unspecified.
   --port=8000             Port number to listen on.
   --buffer=64KB           Size of the buffer used for TCP reads.
   --queue-size=1024       Size of the delay queue storing read buffers.

args.go

@@ -9,6 +9,9 @@ func parseArgs(args []string) (*lib.SpeedbumpCfg, error) {
 	var app = kingpin.New("speedbump", "TCP proxy for simulating variable network latency.")
 
 	var (
+		host = app.Flag("host", "IP or hostname to listen on. Speedbump will bind to all network interfaces if unspecified.").
+			Default("").
+			String()
 		port       = app.Flag("port", "Port number to listen on.").Default("8000").Int()
 		bufferSize = app.Flag("buffer", "Size of the buffer used for TCP reads.").
 				Default("64KB").
@@ -51,14 +54,15 @@ func parseArgs(args []string) (*lib.SpeedbumpCfg, error) {
 				String()
 	)
 
-	app.Version("1.0.0")
+	app.Version("1.1.0")
 	_, err := app.Parse(args)
 
 	if err != nil {
 		return nil, err
 	}
 
 	var cfg = lib.SpeedbumpCfg{
+		Host:       *host,
 		Port:       *port,
 		DestAddr:   *destAddr,
 		BufferSize: int(*bufferSize),

args_test.go

@@ -25,6 +25,7 @@ func TestParseArgsError(t *testing.T) {
 func TestParseArgsAll(t *testing.T) {
 	cfg, err := parseArgs(
 		[]string{
+			"--host=somehost",
 			"--port=1234",
 			"--buffer=200B",
 			"--latency=100ms",
@@ -39,6 +40,7 @@ func TestParseArgsAll(t *testing.T) {
 	)
 	assert.Nil(t, err)
 	assert.Equal(t, cfg.DestAddr, "host:777")
+	assert.Equal(t, cfg.Host, "somehost")
 	assert.Equal(t, cfg.Port, 1234)
 	assert.Equal(t, 200, cfg.BufferSize)
 	assert.Equal(t, time.Millisecond*100, cfg.Latency.Base)

lib/speedbump.go

@@ -30,6 +30,8 @@ type Speedbump struct {
 
 // SpeedbumpCfg contains Spedbump instance configuration
 type SpeedbumpCfg struct {
+	// IP or a hostname to listen on (binds to all network interfaces if unspecified)
+	Host string
 	// Port specifies the local port number to listen on
 	Port int
 	// DestAddr specifies the proxy desination address in host:port format
@@ -46,7 +48,7 @@ type SpeedbumpCfg struct {
 
 // NewSpeedbump creates a Speedbump instance based on a provided config
 func NewSpeedbump(cfg *SpeedbumpCfg) (*Speedbump, error) {
-	localTCPAddr, err := net.ResolveTCPAddr("tcp", fmt.Sprintf(":%d", cfg.Port))
+	localTCPAddr, err := net.ResolveTCPAddr("tcp", fmt.Sprintf("%s:%d", cfg.Host, cfg.Port))
 	if err != nil {
 		return nil, fmt.Errorf("Error resolving local address: %s", err)
 	}

lib/speedbump_test.go

@@ -37,6 +37,7 @@ func startEchoSrv(port int) error {
 
 func TestNewSpeedbump(t *testing.T) {
 	cfg := SpeedbumpCfg{
+		"localhost",
 		8000,
 		"localhost:1234",
 		0xffff,
@@ -49,8 +50,24 @@ func TestNewSpeedbump(t *testing.T) {
 	assert.Equal(t, 0xffff, s.bufferSize)
 }
 
+func TestNewSpeedbumpInvalidHost(t *testing.T) {
+	cfg := SpeedbumpCfg{
+		"nope",
+		8080,
+		"localhost:1234",
+		0xffff,
+		100,
+		defaultLatencyCfg,
+		"WARN",
+	}
+	s, err := NewSpeedbump(&cfg)
+	assert.Nil(t, s)
+	assert.ErrorContains(t, err, "lookup nope")
+}
+
 func TestNewSpeedbumpErrorResolvingLocal(t *testing.T) {
 	cfg := SpeedbumpCfg{
+		"localhost",
 		-1,
 		"localhost:1234",
 		0xffff,
@@ -65,6 +82,7 @@ func TestNewSpeedbumpErrorResolvingLocal(t *testing.T) {
 
 func TestNewSpeedbumpErrorResolvingDest(t *testing.T) {
 	cfg := SpeedbumpCfg{
+		"localhost",
 		8000,
 		"nope:1234",
 		0xffff,
@@ -93,6 +111,7 @@ func TestNewSpeedbumpDefaultQueueSize(t *testing.T) {
 
 func TestStartListenError(t *testing.T) {
 	cfg := SpeedbumpCfg{
+		"localhost",
 		1, // a privileged port
 		"localhost:1234",
 		0xffff,
@@ -123,6 +142,7 @@ func TestSpeedbumpWithEchoServer(t *testing.T) {
 	go startEchoSrv(port)
 
 	cfg := SpeedbumpCfg{
+		"localhost",
 		8000,
 		testSrvAddr,
 		0xffff,