Don't buffer packets in channels

Instead, buffer packet headers in in-memory files.

Fixes #20

saver/tcp.go

@@ -132,35 +132,9 @@ func (t *TCP) start(ctx context.Context, duration time.Duration) {
 	derivedCtx, derivedCancel := context.WithTimeout(ctx, duration)
 	defer derivedCancel()
 
-	// First read the UUID
-	t.state.Set("uuidwait")
-	var uuidEvent UUIDEvent
-	var ok bool
-	select {
-	case uuidEvent, ok = <-t.uuidchanRead:
-		if !ok {
-			log.Println("UUID channel closed, PCAP capture cancelled with no UUID")
-			t.error("uuidchan")
-			return
-		}
-	case <-ctx.Done():
-		log.Println("Context cancelled, PCAP capture cancelled with no UUID")
-		t.error("uuid")
-		return
-	}
-
-	// Create a file and directory based on the UUID and the time.
-	t.state.Set("dircreation")
-	dir, fname := filename(t.dir, uuidEvent)
-	err := os.MkdirAll(dir, 0777)
-	if err != nil {
-		log.Println("Could not create directory", dir, err)
-		t.error("mkdir")
-		return
-	}
 	buff := &bytes.Buffer{}
 
-	// Write PCAP data to the new file.
+	// Write PCAP data to the buffer.
 	w := pcapgo.NewWriterNanos(buff)
 	// Now save packets until the stream is done or the context is canceled.
 	t.state.Set("readingpackets")
@@ -194,6 +168,33 @@ func (t *TCP) start(ctx context.Context, duration time.Duration) {
 		t.savePacket(w, p, headerLen)
 	}
 
+	// Read the UUID to determine the filename
+	t.state.Set("uuidwait")
+	var uuidEvent UUIDEvent
+	select {
+	case uuidEvent, ok = <-t.uuidchanRead:
+		if !ok {
+			log.Println("UUID channel closed, PCAP capture cancelled with no UUID")
+			t.error("uuidchan")
+			return
+		}
+	case <-ctx.Done():
+		log.Println("Context cancelled, PCAP capture cancelled with no UUID")
+		t.error("uuid")
+		return
+	}
+	// uuidEvent is now set to a good value.
+
+	// Create a file and directory based on the UUID and the time.
+	t.state.Set("dircreation")
+	dir, fname := filename(t.dir, uuidEvent)
+	err := os.MkdirAll(dir, 0777)
+	if err != nil {
+		log.Println("Could not create directory", dir, err)
+		t.error("mkdir")
+		return
+	}
+
 	t.state.Set("savingfile")
 	fullFilename := path.Join(dir, fname)
 	err = ioutil.WriteFile(fullFilename, buff.Bytes(), 0664)

saver/tcp_test.go

@@ -101,7 +101,7 @@ func TestSaverDryRun(t *testing.T) {
 	s.start(ctx, 10*time.Second) // Give the disk IO 10 seconds to happen.
 	expected := statusTracker{
 		status: "stopped",
-		past:   []string{"notstarted", "uuidwait", "dircreation", "readingpackets", "nopacketserror"},
+		past:   []string{"notstarted", "readingpackets", "nopacketserror"},
 	}
 	if !reflect.DeepEqual(&tracker, &expected) {
 		t.Errorf("%+v != %+v", &tracker, &expected)
@@ -120,12 +120,19 @@ func TestSaverNoUUID(t *testing.T) {
 	tracker := statusTracker{status: s.state.Get()}
 	s.state = &tracker
 
+	h, err := pcap.OpenOffline("../testdata/v4.pcap")
+	rtx.Must(err, "Could not open v4.pcap")
+	ps := gopacket.NewPacketSource(h, h.LinkType())
+	for p := range ps.Packets() {
+		s.Pchan <- p
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
 	defer cancel()
 	s.start(ctx, 10*time.Second)
 	expected := statusTracker{
 		status: "stopped",
-		past:   []string{"notstarted", "uuidwait", "uuiderror"},
+		past:   []string{"notstarted", "readingpackets", "uuidwait", "uuiderror"},
 	}
 	if !reflect.DeepEqual(&tracker, &expected) {
 		t.Errorf("%+v != %+v", &tracker, &expected)
@@ -144,11 +151,19 @@ func TestSaverNoUUIDClosedUUIDChan(t *testing.T) {
 	tracker := statusTracker{status: s.state.Get()}
 	s.state = &tracker
 
+	h, err := pcap.OpenOffline("../testdata/v4.pcap")
+	rtx.Must(err, "Could not open v4.pcap")
+	ps := gopacket.NewPacketSource(h, h.LinkType())
+	for p := range ps.Packets() {
+		s.Pchan <- p
+	}
+	close(s.Pchan)
 	close(s.UUIDchan)
+
 	s.start(context.Background(), 10*time.Second)
 	expected := statusTracker{
 		status: "stopped",
-		past:   []string{"notstarted", "uuidwait", "uuidchanerror"},
+		past:   []string{"notstarted", "readingpackets", "uuidwait", "uuidchanerror"},
 	}
 	if !reflect.DeepEqual(&tracker, &expected) {
 		t.Errorf("%+v != %+v", &tracker, &expected)
@@ -169,11 +184,20 @@ func TestSaverCantMkdir(t *testing.T) {
 	s.state = &tracker
 
 	s.UUIDchan <- UUIDEvent{"testUUID", time.Now()}
+
+	h, err := pcap.OpenOffline("../testdata/v4.pcap")
+	rtx.Must(err, "Could not open v4.pcap")
+	ps := gopacket.NewPacketSource(h, h.LinkType())
+	for p := range ps.Packets() {
+		s.Pchan <- p
+	}
+	close(s.Pchan)
+
 	s.start(context.Background(), 10*time.Second)
 
 	expected := statusTracker{
 		status: "stopped",
-		past:   []string{"notstarted", "uuidwait", "dircreation", "mkdirerror"},
+		past:   []string{"notstarted", "readingpackets", "uuidwait", "dircreation", "mkdirerror"},
 	}
 	if !reflect.DeepEqual(&tracker, &expected) {
 		t.Errorf("%+v != %+v", &tracker, &expected)
@@ -203,14 +227,15 @@ func TestSaverCantCreate(t *testing.T) {
 	for p := range ps.Packets() {
 		s.Pchan <- p
 	}
+	close(s.Pchan)
 
 	ctx, cancel := context.WithTimeout(context.Background(), 1*time.Second)
 	defer cancel()
 	s.start(ctx, 100*time.Millisecond)
 
 	expected := statusTracker{
 		status: "stopped",
-		past:   []string{"notstarted", "uuidwait", "dircreation", "readingpackets", "savingfile", "filewriteerror", "discardingpackets"},
+		past:   []string{"notstarted", "readingpackets", "uuidwait", "dircreation", "savingfile", "filewriteerror", "discardingpackets"},
 	}
 	if !reflect.DeepEqual(&tracker, &expected) {
 		t.Errorf("%+v != %+v", &tracker, &expected)