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pcap.js
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/*global process require exports console */
var util, IOWatcher,
dns = require('dns'),
Buffer = require('buffer').Buffer,
events = require('events'),
binding = require('./build/default/pcap_binding'),
HTTPParser = process.binding('http_parser').HTTPParser,
url = require('url');
if (process.versions && process.versions.node && process.versions.node.split('.')[1] >= 3) {
util = require("util");
IOWatcher = process.binding('io_watcher').IOWatcher;
} else {
util = require("sys");
IOWatcher = process.IOWatcher;
}
function Pcap() {
this.opened = false;
this.fd = null;
events.EventEmitter.call(this);
}
util.inherits(Pcap, events.EventEmitter);
exports.lib_version = binding.lib_version();
Pcap.prototype.findalldevs = function () {
return binding.findalldevs();
};
Pcap.prototype.open = function (live, device, filter, buffer_size) {
var me = this;
if (typeof buffer_size === 'number' && !isNaN(buffer_size)) {
this.buffer_size = Math.round(buffer_size);
} else {
this.buffer_size = 10 * 1024 * 1024; // Default buffer size is 10MB
}
if (live) {
this.device_name = device || binding.default_device();
this.link_type = binding.open_live(this.device_name, filter || "", this.buffer_size);
} else {
this.device_name = device;
this.link_type = binding.open_offline(this.device_name, filter || "", this.buffer_size);
}
this.fd = binding.fileno();
this.opened = true;
this.readWatcher = new IOWatcher();
this.empty_reads = 0;
this.buf = new Buffer(65535);
// called for each packet read by pcap
function packet_ready(header) {
header.link_type = me.link_type;
header.time_ms = (header.tv_sec * 1000) + (header.tv_usec / 1000);
me.buf.pcap_header = header;
me.emit('packet', me.buf);
}
// readWatcher gets a callback when pcap has data to read. multiple packets may be readable.
this.readWatcher.callback = function pcap_read_callback() {
var packets_read = binding.dispatch(me.buf, packet_ready);
if (packets_read < 1) {
// TODO - figure out what is causing this, and if it is bad.
me.empty_reads += 1;
}
};
this.readWatcher.set(this.fd, true, false);
this.readWatcher.start();
};
Pcap.prototype.close = function () {
this.opened = false;
binding.close();
// TODO - remove listeners so program will exit I guess?
};
Pcap.prototype.stats = function () {
return binding.stats();
};
exports.Pcap = Pcap;
exports.createSession = function (device, filter, buffer_size) {
var session = new Pcap();
session.open(true, device, filter, buffer_size);
return session;
};
exports.createOfflineSession = function (path, filter) {
var session = new Pcap();
session.open(false, path, filter, 0);
return session;
};
//
// Decoding functions
//
function lpad(str, len) {
while (str.length < len) {
str = "0" + str;
}
return str;
}
function dump_bytes(raw_packet, offset) {
for (var i = offset; i < raw_packet.pcap_header.caplen ; i += 1) {
console.log(i + ": " + raw_packet[i]);
}
}
var unpack = {
ethernet_addr: function (raw_packet, offset) {
return [
lpad(raw_packet[offset].toString(16), 2),
lpad(raw_packet[offset + 1].toString(16), 2),
lpad(raw_packet[offset + 2].toString(16), 2),
lpad(raw_packet[offset + 3].toString(16), 2),
lpad(raw_packet[offset + 4].toString(16), 2),
lpad(raw_packet[offset + 5].toString(16), 2)
].join(":");
},
uint16: function (raw_packet, offset) {
return ((raw_packet[offset] * 256) + raw_packet[offset + 1]);
},
uint32: function (raw_packet, offset) {
return (
(raw_packet[offset] * 16777216) +
(raw_packet[offset + 1] * 65536) +
(raw_packet[offset + 2] * 256) +
raw_packet[offset + 3]
);
},
uint64: function (raw_packet, offset) {
return (
(raw_packet[offset] * 72057594037927936) +
(raw_packet[offset + 1] * 281474976710656) +
(raw_packet[offset + 2] * 1099511627776) +
(raw_packet[offset + 3] * 4294967296) +
(raw_packet[offset + 4] * 16777216) +
(raw_packet[offset + 5] * 65536) +
(raw_packet[offset + 6] * 256) +
raw_packet[offset + 7]
);
},
ipv4_addr: function (raw_packet, offset) {
return [
raw_packet[offset],
raw_packet[offset + 1],
raw_packet[offset + 2],
raw_packet[offset + 3]
].join('.');
},
ipv6_addr: function (raw_packet, offset) {
var ret = '';
var octetpairs = [];
for (var i=offset; i<offset+16; i+=2) {
octetpairs.push(unpack.uint16(raw_packet,i).toString(16));
}
var curr_start, curr_len = undefined;
var max_start, max_len = undefined;
for(var i = 0; i < 8; i++){
if(octetpairs[i] == "0"){
if(curr_start === undefined){
curr_len = 1;
curr_start = i;
}else{
curr_len++;
if(!max_start || curr_len > max_len){
max_start = curr_start;
max_len = curr_len;
}
}
}else{
curr_start = undefined;
}
}
if(max_start !== undefined){
var tosplice = max_start == 0 || (max_start + max_len > 7) ? ":" : "";
octetpairs.splice(max_start, max_len,tosplice);
if(max_len == 8){octetpairs.push("");}
}
ret = octetpairs.join(":");
return ret;
}
};
exports.unpack = unpack;
var decode = {}; // convert raw packet data into JavaScript objects with friendly names
decode.icmp_descs = [
["Echo Reply"],["Reserved"],["Reserved"],
// ICMP Type 3
["Destination Network Unreachable",
"Destination Host Unreachable",
"Destination Protocol Unreachable",
"Destination Port Unreachable",
"Fragmentation required, and DF flag set",
"Source route failed",
"Destination network unknown",
"Destination host unknown",
"Source host isolated",
"Network administratively prohibited",
"Host administratively prohibited",
"Network unreachable for TOS",
"Host unreachable for TOS",
"Communication administratively prohibited"],
["Source Quench"],
["Redirect Network","Redirect Host", "Redirect TOS and Network", "Redirect TOS and Host"],
["Alternate Host Address"],
["Reserved"],
["Echo Request"],
["Router Advertisement"],
["Router Solicitation"],
["TTL expired in transit","Fragment reassembly time exceeded"],
];
decode.icmp_fallbacks = ["","","","Destination Unreachable (unknown code ", "Redirect (unknown code ", "","","","","","Time Exceeded (unknown code "];
decode.packet = function (raw_packet) {
var packet = {};
packet.link_type = raw_packet.pcap_header.link_type;
switch (packet.link_type) {
case "LINKTYPE_ETHERNET":
packet.link = decode.ethernet(raw_packet, 0);
break;
case "LINKTYPE_NULL":
packet.link = decode.nulltype(raw_packet, 0);
break;
case "LINKTYPE_RAW":
packet.link = decode.rawtype(raw_packet, 0);
break;
default:
console.log("pcap.js: decode.packet() - Don't yet know how to decode link type " + raw_packet.pcap_header.link_type);
}
packet.pcap_header = raw_packet.pcap_header; // TODO - merge values here instead of putting ref on packet buffer
return packet;
};
decode.rawtype = function (raw_packet, offset) {
var ret = {};
ret.ip = decode.ip(raw_packet, 0);
return ret;
};
decode.nulltype = function (raw_packet, offset) {
var ret = {};
// an oddity about nulltype is that it starts with a 4 byte header, but I can't find a
// way to tell which byte order is used. The good news is that all address family
// values are 8 bits or less.
if (raw_packet[0] === 0 && raw_packet[1] === 0) { // must be one of the endians
ret.pftype = raw_packet[3];
} else { // and this is the other one
ret.pftype = raw_packet[0];
}
if (ret.pftype === 2) { // AF_INET, at least on my Linux and OSX machines right now
ret.ip = decode.ip(raw_packet, 4);
} else if (ret.pftype === 30) { // AF_INET6, often
ret.ip = decode.ip6(raw_packet, 4);
} else {
console.log("pcap.js: decode.nulltype() - Don't know how to decode protocol family " + ret.pftype);
}
return ret;
};
decode.pppoe_code = {
0x0 :"PPPoE Session",
0x7 : "PADO (PPPoE Active Discovery Offer)",
0x9 : "PADI (PPPoE Active Disovery Initiation)",
0x19 : "PADR (PPPoE Active Discovery Request)",
0x65 : "PADS (PPPoE Active Discovery Session Confirmation)",
0xa7 : "PADT (PPPoE Active Discovery Terminate)"
};
decode.pppoe = function (raw_packet, offset) {
var ret = {};
var vertype = raw_packet[offset];
ret.ver = vertype & 0x15;
ret.type = vertype >> 4;
ret.code = decode.pppoe_code[raw_packet[offset + 1]];
ret.session_id = unpack.uint16(raw_packet, offset + 2);
ret.valid = raw_packet[offset + 1] === 0 && ret.session_id !== 0 && ret.session_id !== 0xFFFF;
ret.length = unpack.uint16(raw_packet, offset + 4);
return ret;
}
decode.pppoe_discovery = function (raw_packet, offset) {
var ret = {};
var vertype = raw_packet[offset];
ret.ver = vertype & 0x15;
ret.type = vertype >> 4;
ret.code = decode.pppoe_code[raw_packet[offset + 1]];
ret.session_id = unpack.uint16(raw_packet, offset + 2);
ret.length = unpack.uint16(raw_packet, offset + 4);
return ret;
}
decode.ethernet = function (raw_packet, offset) {
var ret = {};
ret.dhost = unpack.ethernet_addr(raw_packet, 0);
ret.shost = unpack.ethernet_addr(raw_packet, 6);
ret.ethertype = unpack.uint16(raw_packet, 12);
offset = 14;
// Check for a tagged frame
switch (ret.ethertype) {
case 0x8100: // VLAN-tagged (802.1Q)
ret.vlan = decode.vlan(raw_packet, 14);
// Update the ethertype
ret.ethertype = unpack.uint16(raw_packet, 16);
offset = 18;
break;
}
if (ret.ethertype < 1536) {
// this packet is actually some 802.3 type without an ethertype
ret.ethertype = 0;
} else {
// http://en.wikipedia.org/wiki/EtherType
switch (ret.ethertype) {
case 0x800: // IPv4
ret.ip = decode.ip(raw_packet, offset);
break;
case 0x806: // ARP
ret.arp = decode.arp(raw_packet, offset);
break;
case 0x86dd: // IPv6 - http://en.wikipedia.org/wiki/IPv6
ret.ipv6 = decode.ip6(raw_packet, offset);
break;
case 0x88cc: // LLDP - http://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol
ret.lldp = "need to implement LLDP";
break;
case 0x8863:
ret.pppoe = decode.pppoe_discovery(raw_packet, offset);
break;
case 0x8864:
ret.pppoe = decode.pppoe(raw_packet, offset);
break;
default:
console.log("pcap.js: decode.ethernet() - Don't know how to decode ethertype " + ret.ethertype);
}
}
return ret;
};
decode.vlan = function (raw_packet, offset) {
var ret = {};
http://en.wikipedia.org/wiki/IEEE_802.1Q
ret.priority = (raw_packet[offset] & 0xE0) >> 5;
ret.canonical_format = (raw_packet[offset] & 0x10) >> 4;
ret.id = ((raw_packet[offset] & 0x0F) << 8) | raw_packet[offset + 1];
return ret;
};
decode.arp = function (raw_packet, offset) {
var ret = {};
// http://en.wikipedia.org/wiki/Address_Resolution_Protocol
ret.htype = unpack.uint16(raw_packet, offset); // 0, 1
ret.ptype = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.hlen = raw_packet[offset + 4];
ret.plen = raw_packet[offset + 5];
ret.operation = unpack.uint16(raw_packet, offset + 6); // 6, 7
if (ret.operation === 1) {
ret.operation = "request";
}
else if (ret.operation === 2) {
ret.operation = "reply";
}
else {
ret.operation = "unknown";
}
if (ret.hlen === 6 && ret.plen === 4) { // ethernet + IPv4
ret.sender_ha = unpack.ethernet_addr(raw_packet, offset + 8); // 8, 9, 10, 11, 12, 13
ret.sender_pa = unpack.ipv4_addr(raw_packet, offset + 14); // 14, 15, 16, 17
ret.target_ha = unpack.ethernet_addr(raw_packet, offset + 18); // 18, 19, 20, 21, 22, 23
ret.target_pa = unpack.ipv4_addr(raw_packet, offset + 24); // 24, 25, 26, 27
}
// don't know how to decode more exotic ARP types
return ret;
};
decode.ip = function (raw_packet, offset) {
var ret = {};
// http://en.wikipedia.org/wiki/IPv4
ret.version = (raw_packet[offset] & 240) >> 4; // first 4 bits
ret.header_length = raw_packet[offset] & 15; // second 4 bits
ret.header_bytes = ret.header_length * 4;
ret.diffserv = raw_packet[offset + 1];
ret.total_length = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.identification = unpack.uint16(raw_packet, offset + 4); // 4, 5
ret.flags = {};
ret.flags.reserved = (raw_packet[offset + 6] & 128) >> 7;
ret.flags.df = (raw_packet[offset + 6] & 64) >> 6;
ret.flags.mf = (raw_packet[offset + 6] & 32) >> 5;
ret.fragment_offset = ((raw_packet[offset + 6] & 31) * 256) + raw_packet[offset + 7]; // 13-bits from 6, 7
ret.ttl = raw_packet[offset + 8];
ret.protocol = raw_packet[offset + 9];
ret.header_checksum = unpack.uint16(raw_packet, offset + 10); // 10, 11
ret.saddr = unpack.ipv4_addr(raw_packet, offset + 12); // 12, 13, 14, 15
ret.daddr = unpack.ipv4_addr(raw_packet, offset + 16); // 16, 17, 18, 19
// TODO - parse IP "options" if header_length > 5
switch (ret.protocol) {
case 1:
ret.protocol_name = "ICMP";
ret.icmp = decode.icmp(raw_packet, offset + (ret.header_length * 4));
break;
case 2:
ret.protocol_name = "IGMP";
ret.igmp = decode.igmp(raw_packet, offset + (ret.header_length * 4));
break;
case 6:
ret.protocol_name = "TCP";
ret.tcp = decode.tcp(raw_packet, offset + (ret.header_length * 4), ret);
break;
case 17:
ret.protocol_name = "UDP";
ret.udp = decode.udp(raw_packet, offset + (ret.header_length * 4));
break;
default:
ret.protocol_name = "Unknown";
}
return ret;
};
decode.ip6_headernames = { 0 : "Hop By Hop", 43 : "Routing", 44 : "Fragment", 50 : "ESP", 51 : "AH",
60 : "Destination Options"};
decode.ip6_pad0Option = function(raw_packet, offset, header){
var opt = {};
opt.name = "Pad0";
opt.length = 1;
return opt;
}
decode.ip6_padNOption = function(raw_packet, offset, header){
var opt = {};
opt.name = "PadN";
opt.length = raw_packet[offset + 1] - 2;
return opt;
}
decode.ip6_routerAlertOption = function(raw_packet, offset, header){
var opt = {};
opt.name = "Router Alert";
opt.length = raw_packet[offset + 1];
if(opt.length != 2){opt.valid = false; header.valid = false;}
opt.value = unpack.uint16(raw_packet,offset + 2);
switch(opt.value){
case 0:
opt.message = "Multicast Listener Discovery";
break;
case 1:
opt.message = "RSVP Message";
break;
case 2:
opt.message = "Active Networks Message";
break;
default:
opt.message = "Unknown Router Alert";
break;
}
return opt;
}
// TODO: More options...
decode.ip6_options = {0 : decode.ip6_pad0Option, 1: decode.ip6_padNOption, 5 : decode.ip6_routerAlertOption};
decode.ip6_optionsheader = function(raw_packet, ip, offset, header){
header.options = [];
offset += 2;
var cursor = 0;
while(cursor < header.length){
var opttype = raw_packet[offset + cursor];
var f = decode.ip6_options[opttype];
if(f){
var opt = f(raw_packet, offset + cursor, header);
cursor += opt.length;
header.options.push(opt);
}else{
// todo: RFC compliant option parsing (use high bits of option type)
var opt = {};
opt.name = "Unknown option";
header.options.push(opt);
break;
}
}
}
decode.ip6_routingheader = function(raw_packet, ip, offset, header){
header.routing_type = raw_packet[offset + 2];
header.segments_left = raw_packet[offset + 3];
header.segments = [];
var seg_size = 0;
if(header.routing_type == 0){
header.segments_valid = decode.check_length(raw_packet, offset + 4, header.segments_left * 16);
var segment_cursor = offset + 4;
for(var i = 0; i < header.segments_left; i++){
header.segments.push(unpack.ipv6_addr(raw_packet, segment_cursor));
segment_cursor += s;
}
}// TODO: other cases (type 1, type 2)
}
decode.ip6_fragmentheader = function(raw_packet, ip, offset, header){
header.reserved1 = raw_packet[offset + 1];
var frag_off = unpack.uint16(raw_packet,offset + 2);
header.fragment_offset = (frag_off >> 3) * 8;
if(offset != 0){
header.next_header = 59;
}
header.reserved2 = frag_off & 0x6;
header.morefragments = frag_off & 0x1;
header.identification = unpack.uint32(raw_packet,offset + 4);
}
decode.ip6_ahheader = function(raw_packet, ip, offset, header){
header.reserved = unpack.uint16(raw_packet, offset + 2);
header.spi = unpack.uint32(raw_packet, offset + 4);
header.sequence_number = unpack.uint32(raw_packet, 8);
// TODO: what to do with auth data?
}
decode.ip6_parsers = {0 : decode.ip6_optionsheader, 43 : decode.ip6_routingheader, 44 : decode.ip6_fragmentheader, 51 : decode.ip6_ahheader, 60 : decode.ip6_optionsheader};
decode.ip6_ext_header = function(raw_packet, ip, offset, next_header){
var header = {};
header.next_header = raw_packet[offset];
header.name = decode.ip6_headernames[next_header];
if(next_header == 44){
header.length = 8;
}else if(next_header == 51){
var lengthfield = raw_packet[offset + 1];
header.length = (lengthfield + 2) * 4;
}else{
var lengthfield = raw_packet[offset + 1];
header.length = (lengthfield + 1) * 8;
}
header.valid = decode.check_length(raw_packet, offset, header.length);
decode.ip6_parsers[next_header](raw_packet, ip, offset, header);
return header;
}
decode.ip6_header = function(raw_packet, next_header, ip, offset) {
ip.protocol_name = "IPv6";
while(true){
switch (next_header) {
case 0:
case 43:
case 44:
case 51:
case 60:
var header = decode.ip6_ext_header(raw_packet, ip, offset, next_header);
ip.extension_headers.push(header);
if(header.valid){
offset += header.length;
next_header = header.next_header;
}else{
ip.valid = false;
return;
}
break;
case 1:
ip.protocol_name = "ICMP";
ip.icmp = decode.icmp(raw_packet, offset);
return;
case 2:
ip.protocol_name = "IGMP";
ip.igmp = decode.igmp(raw_packet, offset);
return;
case 6:
ip.protocol_name = "TCP";
ip.tcp = decode.tcp(raw_packet, offset, ip);
return;
case 17:
ip.protocol_name = "UDP";
ip.udp = decode.udp(raw_packet, offset);
return;
case 50:
ip.protocol_name = "ESP";
return;
case 58:
ip.protocol_name = "ICMPv6";
ip.icmp6 = decode.icmp6(raw_packet, offset);
return;
case 59:
default:
return;
}
}
};
// Prevent stale values sneaking in due to reading off the end of a packet (instead we read 0 and mark the packet as invalid)
decode.check_length = function(raw_packet, offset, needed){
var remaining = raw_packet.pcap_header.caplen - offset;
if(remaining >= needed){
return true;
}else{
var packet_end = offset + remaining;
var needed_end = offset + needed;
for(i = packet_end; i < needed_end; i++){
raw_packet[i] = 0;
}
return false;
}
}
decode.ip6 = function (raw_packet, offset) {
var ret = {};
var long_enough = decode.check_length(raw_packet, offset, 40);
// http://en.wikipedia.org/wiki/IPv6
ret.version = (raw_packet[offset] & 240) >> 4; // first 4 bits
ret.traffic_class = ((raw_packet[offset] & 15) << 4) + ((raw_packet[offset+1] & 240) >> 4);
ret.flow_label = ((raw_packet[offset + 1] & 15) << 16) +
(raw_packet[offset + 2] << 8) +
raw_packet[offset + 3];
ret.payload_length = unpack.uint16(raw_packet, offset+4);
ret.total_length = ret.payload_length + 40;
ret.next_header = raw_packet[offset+6];
ret.hop_limit = raw_packet[offset+7];
ret.saddr = unpack.ipv6_addr(raw_packet, offset+8);
ret.daddr = unpack.ipv6_addr(raw_packet, offset+24);
ret.header_bytes = 40;
ret.extension_headers = [];
if(long_enough){
decode.ip6_header(raw_packet, ret.next_header, ret, offset+40);
}else{
ret.valid = false;
}
return ret;
};
decode.icmp = function (raw_packet, offset) {
var ret = {};
// http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol
ret.type = raw_packet[offset];
ret.code = raw_packet[offset + 1];
ret.checksum = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.id = unpack.uint16(raw_packet, offset + 4); // 4, 5
ret.sequence = unpack.uint16(raw_packet, offset + 6); // 6, 7
var descs = decode.icmp_descs[ret.type];
if(descs){
var str = descs[ret.code];
if(!str){
str = decode.icmp_fallbacks[ret.type];
if(str){
str = str + ret.code + ")";
}else{
str = descs[0];
}
}
ret.type_desc = str;
}else{
ret.type_desc = "type " + ret.type + " code " + ret.code;
}
// There are usually more exciting things hiding in ICMP packets after the headers
return ret;
};
decode.icmp6 = function(raw_packet, offset){
var ret = {};
ret.type = raw_packet[offset];
ret.code = raw_packet[offset + 1];
ret.checksum = unpack.uint16(raw_packet, offset + 2); // 2, 3
var descs = decode.icmp_descs[ret.type];
if(descs){
var str = descs[ret.code];
if(!str){
str = decode.icmp_fallbacks[ret.type];
if(str){
str = str + ret.code + ")";
}else{
str = descs[0];
}
}
ret.type_desc = str;
}else{
ret.type_desc = "type " + ret.type + " code " + ret.code;
}
// TODO: would be nice to verify the checksum
return ret;
}
decode.igmp = function (raw_packet, offset) {
var ret = {};
// http://en.wikipedia.org/wiki/Internet_Group_Management_Protocol
ret.type = raw_packet[offset];
ret.max_response_time = raw_packet[offset + 1];
ret.checksum = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.group_address = unpack.ipv4_addr(raw_packet, offset + 4); // 4, 5, 6, 7
switch (ret.type) {
case 0x11:
ret.version = ret.max_response_time > 0 ? 2 : 1;
ret.type_desc = "Membership Query"
break;
case 0x12:
ret.version = 1;
ret.type_desc = "Membership Report"
break;
case 0x16:
ret.version = 2;
ret.type_desc = "Membership Report"
break;
case 0x17:
ret.version = 2;
ret.type_desc = "Leave Group"
break;
case 0x22:
ret.version = 3;
ret.type_desc = "Membership Report"
// TODO: Decode v3 message
break;
default:
ret.type_desc = "type " + ret.type;
break;
}
return ret;
}
decode.udp = function (raw_packet, offset) {
var ret = {};
// http://en.wikipedia.org/wiki/User_Datagram_Protocol
ret.sport = unpack.uint16(raw_packet, offset); // 0, 1
ret.dport = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.length = unpack.uint16(raw_packet, offset + 4); // 4, 5
ret.checksum = unpack.uint16(raw_packet, offset + 6); // 6, 7
if (ret.sport === 53 || ret.dport === 53) {
ret.dns = decode.dns(raw_packet, offset + 8);
}
return ret;
};
decode.tcp = function (raw_packet, offset, ip) {
var ret = {}, option_offset, options_end;
// http://en.wikipedia.org/wiki/Transmission_Control_Protocol
ret.sport = unpack.uint16(raw_packet, offset); // 0, 1
ret.dport = unpack.uint16(raw_packet, offset + 2); // 2, 3
ret.seqno = unpack.uint32(raw_packet, offset + 4); // 4, 5, 6, 7
ret.ackno = unpack.uint32(raw_packet, offset + 8); // 8, 9, 10, 11
ret.data_offset = (raw_packet[offset + 12] & 0xf0) >> 4; // first 4 bits of 12
ret.header_bytes = ret.data_offset * 4; // convenience for using data_offset
ret.reserved = raw_packet[offset + 12] & 15; // second 4 bits of 12
ret.flags = {};
ret.flags.cwr = (raw_packet[offset + 13] & 128) >> 7; // all flags packed into 13
ret.flags.ece = (raw_packet[offset + 13] & 64) >> 6;
ret.flags.urg = (raw_packet[offset + 13] & 32) >> 5;
ret.flags.ack = (raw_packet[offset + 13] & 16) >> 4;
ret.flags.psh = (raw_packet[offset + 13] & 8) >> 3;
ret.flags.rst = (raw_packet[offset + 13] & 4) >> 2;
ret.flags.syn = (raw_packet[offset + 13] & 2) >> 1;
ret.flags.fin = raw_packet[offset + 13] & 1;
ret.window_size = unpack.uint16(raw_packet, offset + 14); // 14, 15
ret.checksum = unpack.uint16(raw_packet, offset + 16); // 16, 17
ret.urgent_pointer = unpack.uint16(raw_packet, offset + 18); // 18, 19
ret.options = {};
option_offset = offset + 20;
options_end = offset + (ret.data_offset * 4);
while (option_offset < options_end) {
switch (raw_packet[option_offset]) {
case 0:
option_offset += 1;
break;
case 1:
option_offset += 1;
break;
case 2:
ret.options.mss = unpack.uint16(raw_packet, option_offset + 2);
option_offset += 4;
break;
case 3:
ret.options.window_scale = Math.pow(2, (raw_packet[option_offset + 2]));
option_offset += 3;
break;
case 4:
ret.options.sack_ok = true;
option_offset += 2;
break;
case 5:
ret.options.sack = [];
switch (raw_packet[option_offset + 1]) {
case 10:
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 2), unpack.uint32(raw_packet, option_offset + 6)]);
option_offset += 10;
break;
case 18:
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 2), unpack.uint32(raw_packet, option_offset + 6)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 10), unpack.uint32(raw_packet, option_offset + 14)]);
option_offset += 18;
break;
case 26:
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 2), unpack.uint32(raw_packet, option_offset + 6)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 10), unpack.uint32(raw_packet, option_offset + 14)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 18), unpack.uint32(raw_packet, option_offset + 22)]);
option_offset += 26;
break;
case 34:
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 2), unpack.uint32(raw_packet, option_offset + 6)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 10), unpack.uint32(raw_packet, option_offset + 14)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 18), unpack.uint32(raw_packet, option_offset + 22)]);
ret.options.sack.push([unpack.uint32(raw_packet, option_offset + 26), unpack.uint32(raw_packet, option_offset + 30)]);
option_offset += 34;
break;
default:
console.log("Invalid TCP SACK option length " + raw_packet[option_offset + 1]);
option_offset = options_end;
}
break;
case 8:
ret.options.timestamp = unpack.uint32(raw_packet, option_offset + 2);
ret.options.echo = unpack.uint32(raw_packet, option_offset + 6);
option_offset += 10;
break;
default:
throw new Error("Don't know how to process TCP option " + raw_packet[option_offset]);
}
}
ret.data_offset = offset + ret.header_bytes;
ret.data_end = offset + ip.total_length - ip.header_bytes;
ret.data_bytes = ret.data_end - ret.data_offset;
if (ret.data_bytes > 0) {
// add a buffer slice pointing to the data area of this TCP packet.
// Note that this does not make a copy, so ret.data is only valid for this current
// trip through the capture loop.
ret.data = raw_packet.slice(ret.data_offset, ret.data_end);
ret.data.length = ret.data_bytes;
}
// automatic protocol decode ends here. Higher level protocols can be decoded by using payload.
return ret;
};
// helpers for DNS decoder
var dns_util = {
type_to_string: function (type_num) {
switch (type_num) {
case 1:
return "A";
case 2:
return "NS";
case 3:
return "MD";
case 4:
return "MF";
case 5:
return "CNAME";
case 6:
return "SOA";
case 7:
return "MB";
case 8:
return "MG";
case 9:
return "MR";
case 10:
return "NULL";
case 11:
return "WKS";
case 12:
return "PTR";
case 13:
return "HINFO";
case 14:
return "MINFO";
case 15:
return "MX";
case 16:
return "TXT";
default:
return ("Unknown (" + type_num + ")");
}
},
qtype_to_string: function (qtype_num) {
switch (qtype_num) {
case 252:
return "AXFR";
case 253:
return "MAILB";
case 254:
return "MAILA";
case 255:
return "*";
default:
return dns_util.type_to_string(qtype_num);
}
},
class_to_string: function (class_num) {
switch (class_num) {
case 1:
return "IN";
case 2:
return "CS";
case 3:
return "CH";
case 4:
return "HS";
default:
return "Unknown (" + class_num + ")";
}
},
qclass_to_string: function (qclass_num) {
if (qclass_num === 255) {
return "*";
} else {
return dns_util.class_to_string(qclass_num);
}
}
};
decode.dns = function (raw_packet, offset) {
var ret = {}, i, internal_offset, question_done, len, parts;
// http://tools.ietf.org/html/rfc1035
ret.header = {};
ret.header.id = unpack.uint16(raw_packet, offset); // 0, 1
ret.header.qr = (raw_packet[offset + 2] & 128) >> 7;
ret.header.opcode = (raw_packet[offset + 2] & 120) >> 3;
ret.header.aa = (raw_packet[offset + 2] & 4) >> 2;
ret.header.tc = (raw_packet[offset + 2] & 2) >> 1;
ret.header.rd = raw_packet[offset + 2] & 1;
ret.header.ra = (raw_packet[offset + 3] & 128) >> 7;
ret.header.z = 0; // spec says this MUST always be 0
ret.header.rcode = raw_packet[offset + 3] & 15;
ret.header.qdcount = unpack.uint16(raw_packet, offset + 4); // 4, 5
ret.header.ancount = unpack.uint16(raw_packet, offset + 6); // 6, 7
ret.header.nscount = unpack.uint16(raw_packet, offset + 8); // 8, 9
ret.header.arcount = unpack.uint16(raw_packet, offset + 10); // 10, 11
internal_offset = offset + 12;
ret.question = [];
for (i = 0; i < ret.header.qdcount ; i += 1) {
ret.question[i] = {};
question_done = false;
parts = [];
while (!question_done && internal_offset < raw_packet.pcap_header.caplen) {
len = raw_packet[internal_offset];
if (len > 0) {
parts.push(raw_packet.toString("ascii", internal_offset + 1, internal_offset + 1 + len));
} else {
question_done = true;
}
internal_offset += (len + 1);
}
ret.question[i].qname = parts.join('.');
ret.question[i].qtype = dns_util.qtype_to_string(unpack.uint16(raw_packet, internal_offset));
internal_offset += 2;
ret.question[i].qclass = dns_util.qclass_to_string(unpack.uint16(raw_packet, internal_offset));
internal_offset += 2;
}
// TODO - actual hard parts here, understand RR compression scheme, etc.
ret.answer = {};
ret.authority = {};
ret.additional = {};
return ret;
};
exports.decode = decode;