Updated the library to create pcap files

under the hood it makes use of the libpcap's capability to create pcap
the add-on makes use of the Async worker

.gitignore

@@ -30,4 +30,6 @@ node_modules
 build
 
 #OSX garbage
-.DS_Store
+.DS_Store
+examples/*.pcap
+.vscode/

examples/pcap_dump_test.js

@@ -0,0 +1,17 @@
+
+
+
+var pcap = require("../pcap"),
+
+pcap_dump = new pcap.PcapDumpSession('en0', "ip proto \\tcp",10*1024*1024,"tmp95.pcap",false,5);
+
+pcap_dump.on('pcap_write_complete_async',function(message){
+        console.log("done.....",message);
+});
+
+pcap_dump.on('pcap_write_error',function(message){
+        console.log("pcap_write_error.....",message);
+});
+
+//pcap_dump.start();
+pcap_dump.startAsyncCapture();

package.json

@@ -28,6 +28,7 @@
     "istanbul": "^0.3.5",
     "mocha": "^2.1.0",
     "mocha-sinon": "^1.1.4",
+    "rewire": "^2.5.2",
     "should": "^5.0.0",
     "sinon": "^1.14.1"
   },

pcap.js

@@ -6,11 +6,13 @@ var decode        = require("./decode").decode;
 var tcp_tracker   = require("./tcp_tracker");
 var DNSCache      = require("./dns_cache");
 var timers        = require("timers");
+var pcap_dump     = require("./pcap_dump");
 
 exports.decode = decode;
 exports.TCPTracker = tcp_tracker.TCPTracker;
 exports.TCPSession = tcp_tracker.TCPSession;
 exports.DNSCache = DNSCache;
+exports.PcapDumpSession = pcap_dump.PcapDumpSession;
 
 function PcapSession(is_live, device_name, filter, buffer_size, outfile, is_monitor) {
     this.is_live = is_live;

pcap_binding.cc

@@ -12,6 +12,156 @@
 #include "pcap_session.h"
 
 using namespace v8;
+using Nan::Callback;
+using Nan::AsyncQueueWorker;
+using Nan::AsyncWorker;
+using Nan::Callback;
+using Nan::HandleScope;
+using Nan::New;
+using Nan::Null;
+using Nan::To;
+
+class PcapWorker : public AsyncWorker {
+ public:
+  PcapWorker(
+        Callback *callback,
+        std::string device,
+        std::string filter,
+        int buffer_size,
+        std::string pcap_output_filename,
+        int num_packets
+    )
+    : 
+    AsyncWorker(callback), 
+    device(device), 
+    filter(filter),
+    buffer_size(buffer_size),
+    pcap_output_filename(pcap_output_filename),
+    num_packets(num_packets)
+    {}
+  ~PcapWorker() {}
+
+  // Executed inside the worker-thread.
+  // It is not safe to access V8, or V8 data structures
+  // here, so everything we need for input and output
+  // should go on `this`.
+  void Execute () {
+    if (pcap_lookupnet(device.c_str(), &net, &mask, errbuf) == -1) {
+        net = 0;
+        mask = 0;
+        fprintf(stderr, "warning: %s - this may not actually work\n", errbuf);
+        SetErrorMessage(errbuf);
+        return;
+    }
+    pcap_handle = pcap_create(device.c_str(), errbuf);
+    if (pcap_handle == NULL) {
+        SetErrorMessage(errbuf);
+        return;
+    }
+
+    // 64KB is the max IPv4 packet size
+    if (pcap_set_snaplen(pcap_handle, 65535) != 0) {
+       SetErrorMessage("error setting snaplen");
+        return;
+    }
+
+    // always use promiscuous mode
+    if (pcap_set_promisc(pcap_handle, 1) != 0) {
+        SetErrorMessage("error setting promiscuous mode");
+        return;
+    }
+
+    // Try to set buffer size.  Sometimes the OS has a lower limit that it will silently enforce.
+    if (pcap_set_buffer_size(pcap_handle, buffer_size) != 0) {
+        SetErrorMessage("error setting buffer size");
+        return;
+    }
+
+
+    // set "timeout" on read, even though we are also setting nonblock below.  On Linux this is required.
+    if (pcap_set_timeout(pcap_handle, 1000) != 0) {
+        SetErrorMessage("error setting read timeout");
+        return;
+    }
+
+    if (pcap_activate(pcap_handle) != 0) {
+        SetErrorMessage(pcap_geterr(pcap_handle));
+        return;
+    }
+    if ((pcap_output_filename.size()) > 0) {
+        pcap_dump_handle = pcap_dump_open(pcap_handle,pcap_output_filename.c_str());
+        if (pcap_dump_handle == NULL) {
+            SetErrorMessage("error opening dump");
+            return;
+        }
+    }
+
+
+    if (filter.size() != 0) {
+        if (pcap_compile(pcap_handle, &fp, filter.c_str(), 1, net) == -1) {
+            SetErrorMessage(pcap_geterr(pcap_handle));
+            return;
+        }
+
+        if (pcap_setfilter(pcap_handle, &fp) == -1) {
+            SetErrorMessage(pcap_geterr(pcap_handle));
+            return;
+        }
+
+        pcap_loop(pcap_handle, num_packets, OnPacketReady, (unsigned char *)pcap_dump_handle);
+        pcap_freecode(&fp);
+        /*
+         * Close the savefile opened in pcap_dump_open().
+         */
+        pcap_dump_close(pcap_dump_handle);
+        /*
+         * Close the packet capture device and free the memory used by the
+         * packet capture descriptor.
+         */     
+        pcap_close(pcap_handle);
+    }
+  }
+
+  // Executed when the async work is complete
+  // this function will be run inside the main event loop
+  // so it is safe to use V8 again
+  void HandleOKCallback () {
+
+    Nan::HandleScope scope;
+
+    Local<Value> argv[] = {
+        Nan::Null()
+      , New<Number>(num_packets)
+    };
+
+    callback->Call(2, argv);
+  }
+
+
+
+static void OnPacketReady(u_char *s, const struct pcap_pkthdr* pkthdr, const u_char* packet) {
+   pcap_dump(s, pkthdr, packet);
+}
+
+ private:
+
+    std::string device;
+    std::string filter;
+    int buffer_size;
+    std::string pcap_output_filename;
+    int num_packets;
+    struct bpf_program fp;
+    bpf_u_int32 mask;
+    bpf_u_int32 net;
+    pcap_t *pcap_handle;
+    pcap_dumper_t *pcap_dump_handle;
+    char errbuf[PCAP_ERRBUF_SIZE];
+
+
+
+
+};
+
 
 // Helper method, convert a sockaddr* (AF_INET or AF_INET6) to a string, and set it as the property
 // named 'key' in the Address object you pass in.
@@ -135,6 +285,57 @@ NAN_METHOD(LibVersion)
     info.GetReturnValue().Set(Nan::New(pcap_lib_version()).ToLocalChecked());
 }
 
+// Asynchronous access to the `Estimate()` function
+NAN_METHOD(PcapDumpAsync) {
+
+    if (info.Length() == 8) {
+        if (!info[0]->IsString()) {
+            Nan::ThrowTypeError("pcap Open: info[0] must be a String");
+            return;
+        }
+        if (!info[1]->IsString()) {
+            Nan::ThrowTypeError("pcap Open: info[1] must be a String");
+            return;
+        }
+        if (!info[2]->IsInt32()) {
+            Nan::ThrowTypeError("pcap Open: info[2] must be a Number");
+            return;
+        }
+        if (!info[3]->IsString()) {
+            Nan::ThrowTypeError("pcap Open: info[3] must be a String");
+            return;
+        }
+        if (!info[4]->IsFunction()) {
+            Nan::ThrowTypeError("pcap Open: info[4] must be a Function");
+            return;
+        }
+        if (!info[5]->IsBoolean()) {
+            Nan::ThrowTypeError("pcap Open: info[5] must be a Boolean");
+            return;
+        }
+        if (!info[6]->IsInt32()) {
+            Nan::ThrowTypeError("pcap Open: info[6] must be a Number");
+            return;
+        }
+        if (!info[7]->IsFunction()) {
+            Nan::ThrowTypeError("pcap Open: info[7] must be a Function");
+            return;
+        }
+    } else {
+        Nan::ThrowTypeError("pcap CreatePcapDump: expecting 7 arguments");
+        return;
+    }
+    Nan::Utf8String device(info[0]->ToString());
+    Nan::Utf8String filter(info[1]->ToString());
+    int buffer_size = info[2]->Int32Value();
+    Nan::Utf8String pcap_output_filename(info[3]->ToString());
+    int num_packets = info[6]->Int32Value();
+    Callback *callback = new Callback(info[7].As<Function>()); 
+
+  AsyncQueueWorker(new PcapWorker(callback, std::string(*device),std::string(*filter),buffer_size, std::string(*pcap_output_filename),num_packets));
+}
+
+
 void Initialize(Handle<Object> exports)
 {
     Nan::HandleScope scope;
@@ -144,6 +345,7 @@ void Initialize(Handle<Object> exports)
     exports->Set(Nan::New("findalldevs").ToLocalChecked(), Nan::New<FunctionTemplate>(FindAllDevs)->GetFunction());
     exports->Set(Nan::New("default_device").ToLocalChecked(), Nan::New<FunctionTemplate>(DefaultDevice)->GetFunction());
     exports->Set(Nan::New("lib_version").ToLocalChecked(), Nan::New<FunctionTemplate>(LibVersion)->GetFunction());
+    exports->Set(Nan::New("create_pcap_dump_async").ToLocalChecked(), Nan::New<FunctionTemplate>(PcapDumpAsync)->GetFunction());
 }
 
 NODE_MODULE(pcap_binding, Initialize)

pcap_dump.js

@@ -0,0 +1,90 @@
+var util = require("util");
+var events = require("events");
+var binding = require("./build/Release/pcap_binding");
+
+
+function PcapDumpSession(device_name, filter, buffer_size, outfile, is_monitor, number_of_packets_to_be_read) {
+
+    this.device_name = device_name;
+    this.filter = filter || "";
+    this.buffer_size = buffer_size;
+    this.outfile = outfile || "tmp.pcap";
+    this.is_monitor = Boolean(is_monitor);
+    this.opened = null;
+    this.packets_read = 0;
+    this.number_of_packets_to_be_read = number_of_packets_to_be_read || 1;
+    this.session = new binding.PcapSession();
+
+    if (typeof this.buffer_size === "number" && !isNaN(this.buffer_size)) {
+        this.buffer_size = Math.round(this.buffer_size);
+    } else {
+        this.buffer_size = 10 * 1024 * 1024; // Default buffer size is 10MB
+    }
+
+    this.device_name = this.device_name || binding.default_device();
+    events.EventEmitter.call(this);
+}
+
+util.inherits(PcapDumpSession, events.EventEmitter);
+
+exports.lib_version = binding.lib_version();
+
+exports.findalldevs = function () {
+    return binding.findalldevs();
+};
+
+
+PcapDumpSession.prototype.startAsyncCapture = function () {
+
+    this.opened = true;
+    binding.create_pcap_dump_async(
+        this.device_name,
+        this.filter,
+        this.buffer_size,
+        this.outfile,
+        PcapDumpSession.prototype.on_packet.bind(this),
+        this.is_monitor,
+        this.number_of_packets_to_be_read,
+        PcapDumpSession.prototype.on_pcap_write_complete_async.bind(this)
+    );
+};
+
+
+PcapDumpSession.prototype.close = function () {
+    this.opened = false;
+    this.session.close();
+};
+
+PcapDumpSession.prototype.stats = function () {
+    return this.session.stats();
+};
+
+PcapDumpSession.prototype.on_pcap_write_complete_async = function (err, packet_count) {
+
+    if (err) {
+        this.emit("pcap_write_error", err);
+
+    } else {
+        this.emit("pcap_write_complete_async", {
+            "packets_read": packet_count,
+            "fileName": this.outfile
+        });
+    }
+
+};
+
+
+PcapDumpSession.prototype.on_packet = function (packet) {
+    this.emit("packet", packet);
+
+};
+
+
+
+
+exports.PcapDumpSession = PcapDumpSession;
+
+
+exports.createPcapDumpSession = function (device, filter, buffer_size, path, monitor, number_of_packets) {
+    return new PcapDumpSession(device, filter, buffer_size, path, monitor, number_of_packets);
+};