WiFi

PacketGen can handle wifi packets thanks to PacketGen::Header::Dot11 classes.

Create wifi packets

As PacketGen::Header::Dot11 is an abstract class it should not be used directly. Instead, PacketGen::Header::Dot11::Control, PacketGen::Header::Dot11::Management and PacketGen::Header::Dot11::Data should be used.

Creation of protected frames is not supported yet.

Create control frames

Control frames may be created this way:

pkt = PacketGen.gen('Dot11::Control', subtype: 13) # Ack control frame
pkt.dot11_control     # => PacketGen::Header::Dot11::Control

Create management frames

Management frames may be created this way:

pkt = PacketGen.gen('Dot11::Management')
pkt.dot11_management     # => PacketGen::Header::Dot11::Management

Management frames are usually specialized. By example, you may want to create an AssociationRequest frame:

pkt = PacketGen.gen('Dot11::Management')
pkt.add('Dot11::AssoReq')
pkt.dot11_assoreq        # => PacketGen::Header::Dot11::AssoReq

Management frames also may contain some elements (see IEEE 802.11 standard):

# add a SSID to AssociationRequest frame
el1 = PacketGen::Header::Dot11::Element.new(type: 'SSID', value: 'My SSID')
pkt.dot11_assoreq.elements << el1

# And also add supported rates
el2 = PacketGen::Header::Dot11::Element.new(type: 'Rates', value: supported_rates)
pkt.dot11_assoreq.elements << el2

Create data frames

Data frames may be created this way (LLC and SNAP layers are needed):

pkt = PacketGen.gen('Dot11::Data', mac1: receiver, mac2: transmitter, mac3: destmac).
                add('LLC').add('SNAP').add('IP', src: sourceip, dst: destip)
pkt.dot11_data     # => PacketGen::Header::Dot11::Data
# #dot11 is a shortcut for #dot11_data
pkt.dot11          # => PacketGen::Header::Dot11::Data
# access to IP datagram
pkt.ip             # => PacketGen::Header::IP

Send wifi packets

To send a Dot11 packet, simply do:

pkt = PacketGen.gen('RadioTap').
                add('Dot11::Management', mac1: clientaddr, mac2: bssid, mac3: bssid).
                add('Dot11::DeAuth', reason: 7)
# compute all checksum and length
pkt.calc
pkt.to_w('wlan0')

RadioTap header is needed to send packets on the air.

Before sending a packet, you always should call PacketGen::Packet#calc to automatically set lengths and checksums in packets. This is not done automatically to let you send malformed packets on "wire" for network test purpose.

Capture and parse wifi packets

Capturing and parsing Dot11 packets is supported by PacketGen.capture, PacketGen.read and PacketGen.parse.

Captured packets may contain a header before Dot11 one: a PPI or a RadioTap, depending on your network interface's driver.

Capturing wifi packets

PacketGen.capture(iface: 'wlan0') do |packet|
  # Here packet should be instances of PacketGen::Packet with a Dot11 header
  do_stuffs_with(packet)
end

Parsing wifi packets in general

Parsing wifi packets is also supported from reading from a PCAP (or PCAP-ng) file, or from parsing a binary string.

Frame Control Sequence

FCS is the CRC of the Dot11 frame. By default, PacketGen, sets a FCS field in all Dot11 frames, and try to parse it when parsing or capturing.

But, some drivers remove FCS field when capturing, and/or do not support setting it. You may deactivate FCS in Dot11, for all packets:

PacketGen::Header::Dot11.has_fcs = false