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PacketFu::PcapFile

PcapFile is a complete libpcap file struct, made up of two elements, a PcapHeader and PcapPackets.

See wiki.wireshark.org/Development/LibpcapFileFormat

PcapFile also can behave as a singleton class, which is usually the better way to handle pcap files of really any size, since it doesn't require storing packets before handing them off to a given block. This is really the way to go.

Public Class Methods

file_to_array(fname) click to toggle source

Takes a given file and returns an array of the packet bytes. Here for backwards compatibilty.

# File lib/packetfu/pcap.rb, line 243
def file_to_array(fname)
        PcapFile.new.file_to_array(:f => fname)
end
new(args={}) click to toggle source
# File lib/packetfu/pcap.rb, line 321
def initialize(args={})
        init_fields(args)
        @filename = args.delete :filename
        super(args[:endian], args[:head], args[:body])
end
read(fname,&block) click to toggle source

Takes a given file name, and reads out the packets. If given a block, it will yield back a PcapPacket object per packet found.

# File lib/packetfu/pcap.rb, line 249
def read(fname,&block) 
        file_header = PcapHeader.new
        pcap_packets = PcapPackets.new 
        unless File.readable? fname
                raise ArgumentError, "Cannot read file `#{fname}'"
        end
        begin
        file_handle = File.open(fname, "rb")
        file_header.read file_handle.read(24)
        packet_count = 0
        pcap_packet = PcapPacket.new(:endian => file_header.endian)
        while pcap_packet.read file_handle.read(16) do
                len = pcap_packet.incl_len
                pcap_packet.data = StructFu::String.new.read(file_handle.read(len.to_i))
                packet_count += 1
                if pcap_packet.data.size < len.to_i
                        warn "Packet ##{packet_count} is corrupted: expected #{len.to_i}, got #{pcap_packet.data.size}. Exiting."
                        break
                end
                if block
                        yield pcap_packet
                else
                        pcap_packets << pcap_packet.clone
                end
        end
        ensure
                file_handle.close
        end
        block ? packet_count : pcap_packets
end
read_packet_bytes(fname,&block) click to toggle source

Takes a filename, and an optional block. If a block is given, yield back the raw packet data from the given file. Otherwise, return an array of parsed packets.

# File lib/packetfu/pcap.rb, line 283
def read_packet_bytes(fname,&block)
        count = 0
        packets = [] unless block
        read(fname) do |packet| 
                if block
                        count += 1
                        yield packet.data.to_s
                else
                        packets << packet.data.to_s
                end
        end
        block ? count : packets
end
Also aliased as: file_to_array
read_packets(fname,&block) click to toggle source

Takes a filename, and an optional block. If a block is given, yield back parsed packets from the given file. Otherwise, return an array of parsed packets.

This is a brazillian times faster than the old methods of extracting packets from files.

# File lib/packetfu/pcap.rb, line 305
def read_packets(fname,&block)
        count = 0
        packets = [] unless block
        read_packet_bytes(fname) do |packet| 
                if block
                        count += 1
                        yield Packet.parse(packet)
                else
                        packets << Packet.parse(packet)
                end
        end
        block ? count : packets
end

Public Instance Methods

a2f(args={}) click to toggle source
Alias for: array_to_file
a2f!(arr) click to toggle source
Alias for: array_to_file!
append(filename='out.pcap') click to toggle source

Shorthand method for appending to a file. Can take either :file => 'name.pcap' or simply 'name.pcap'

# File lib/packetfu/pcap.rb, line 496
def append(filename='out.pcap')
        if filename.kind_of?(Hash)
                f = filename[:filename] || filename[:file] || filename[:f] || 'out.pcap'
        else
                f = filename.to_s
        end
        self.to_file(:filename => f, :append => true)
end
array_to_file(args={}) click to toggle source

Takes an array of packets (as generated by file_to_array), and writes them to a file. Valid arguments are:

:filename
:array      # Can either be an array of packet data, or a hash-value pair of timestamp => data.
:timestamp  # Sets an initial timestamp
:ts_inc     # Sets the increment between timestamps. Defaults to 1 second.
:append     # If true, then the packets are appended to the end of a file.
# File lib/packetfu/pcap.rb, line 406
def array_to_file(args={})
        if args.kind_of? Hash
                filename = args[:filename] || args[:file] || args[:f]
                arr = args[:array] || args[:arr] || args[:a]
                ts = args[:timestamp] || args[:ts] || Time.now.to_i
                ts_inc = args[:timestamp_increment] || args[:ts_inc] || 1
                append = !!args[:append]
        elsif args.kind_of? Array
                arr = args
                filename = append = nil
        else
                raise ArgumentError, "Unknown argument. Need either a Hash or Array."
        end
        unless arr.kind_of? Array
                raise ArgumentError, "Need an array to read packets from"
        end
        arr.each_with_index do |p,i|
                if p.kind_of? Hash # Binary timestamps are included
                        this_ts = p.keys.first
                        this_incl_len = p.values.first.size
                        this_orig_len = this_incl_len
                        this_data = p.values.first
                else # it's an array
                        this_ts = Timestamp.new(:endian => self[:endian], :sec => ts + (ts_inc * i)).to_s
                        this_incl_len = p.to_s.size
                        this_orig_len = this_incl_len
                        this_data = p.to_s
                end
                this_pkt = PcapPacket.new({:endian => self[:endian],
                                                                                                                  :timestamp => this_ts,
                                                                                                                        :incl_len => this_incl_len,
                                                                                                                        :orig_len => this_orig_len,
                                                                                                                        :data => this_data }
                                                                                                                 )
                self[:body] << this_pkt
        end
        if filename
                self.to_f(:filename => filename, :append => append)
        else
                self
        end
end
Also aliased as: a2f
array_to_file!(arr) click to toggle source

Just like array_to_file, but clears any existing packets from the array first.

# File lib/packetfu/pcap.rb, line 452
def array_to_file!(arr)
        clear
        array_to_file(arr)
end
Also aliased as: a2f!
clear() click to toggle source

Clears the contents of the PcapFile.

# File lib/packetfu/pcap.rb, line 340
def clear
        self[:body].clear
end
f2a(args={}) click to toggle source
Alias for: file_to_array
file_to_array(args={}) click to toggle source

file_to_array() translates a libpcap file into an array of packets. Note that this strips out pcap timestamps -- if you'd like to retain timestamps and other libpcap file information, you will want to use read() instead.

# File lib/packetfu/pcap.rb, line 384
def file_to_array(args={})
        filename = args[:filename] || args[:file] || args[:f]
        if filename
                self.read! File.open(filename, "rb") {|f| f.read}
        end
        if args[:keep_timestamps] || args[:keep_ts] || args[:ts]
                self[:body].map {|x| {x.timestamp.to_s => x.data.to_s} }
        else
                self[:body].map {|x| x.data.to_s}
        end
end
Also aliased as: f2a
init_fields(args={}) click to toggle source

Called by initialize to set the initial fields.

# File lib/packetfu/pcap.rb, line 328
def init_fields(args={})
        args[:head] = PcapHeader.new(:endian => args[:endian]).read(args[:head])
        args[:body] = PcapPackets.new(:endian => args[:endian]).read(args[:body])
        return args
end
read(str) click to toggle source

Reads a string to populate the object. Note that this appends new packets to any existing packets in the PcapFile.

# File lib/packetfu/pcap.rb, line 346
def read(str)
        force_binary(str)
        self[:head].read str[0,24]
        self[:body].read str
        self
end
read!(str) click to toggle source

Clears the contents of the PcapFile prior to reading in a new string.

# File lib/packetfu/pcap.rb, line 354
def read!(str)
        clear        
        force_binary(str)
        self.read str
end
read_packet_bytes(fname=@filename,&block) click to toggle source

Calls the class method with this object's @filename

# File lib/packetfu/pcap.rb, line 369
def read_packet_bytes(fname=@filename,&block)
        raise ArgumentError, "Need a file" unless fname
        return self.class.read_packet_bytes(fname, &block)
end
read_packets(fname=@filename,&block) click to toggle source

Calls the class method with this object's @filename

# File lib/packetfu/pcap.rb, line 375
def read_packets(fname=@filename,&block)
        raise ArgumentError, "Need a file" unless fname
        return self.class.read_packets(fname, &block)
end
readfile(file) click to toggle source

A shorthand method for opening a file and reading in the packets. Note that readfile clears any existing packets, since that seems to be the typical use.

# File lib/packetfu/pcap.rb, line 363
def readfile(file)
        fdata = File.open(file, "rb") {|f| f.read}
        self.read! fdata
end
to_f(args={}) click to toggle source
Alias for: to_file
to_file(args={}) click to toggle source

Writes the PcapFile to a file. Takes the following arguments:

:filename # The file to write to.
:append   # If set to true, the packets are appended to the file, rather than overwriting.
# File lib/packetfu/pcap.rb, line 463
def to_file(args={})
        filename = args[:filename] || args[:file] || args[:f]
        unless (!filename.nil? || filename.kind_of?(String))
                raise ArgumentError, "Need a :filename for #{self.class}"
        end
        append = args[:append]
        if append
                if File.exists? filename
                        File.open(filename,'ab') {|file| file.write(self.body.to_s)}
                else
                        File.open(filename,'wb') {|file| file.write(self.to_s)}
                end
        else
                File.open(filename,'wb') {|file| file.write(self.to_s)}
        end
        [filename, self.body.sz, self.body.size]
end
Also aliased as: to_f
to_s() click to toggle source

Returns the object in string form.

# File lib/packetfu/pcap.rb, line 335
def to_s
        self[:head].to_s + self[:body].map {|p| p.to_s}.join
end
write(filename='out.pcap') click to toggle source

Shorthand method for writing to a file. Can take either :file => 'name.pcap' or simply 'name.pcap'

# File lib/packetfu/pcap.rb, line 485
def write(filename='out.pcap')
        if filename.kind_of?(Hash)
                f = filename[:filename] || filename[:file] || filename[:f] || 'out.pcap'
        else
                f = filename.to_s
        end
        self.to_file(:filename => f.to_s, :append => false)
end

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