Added ARP packet layout, changed print_bytes example to require pcap_…

…ffi instead of pcap

examples/print_bytes.rb

@@ -1,7 +1,7 @@
 #!/usr/bin/env ruby
 
 require 'rubygems'
-require 'pcap'
+require 'pcap_ffi'
 
 include FFI
 

lib/pcap_ffi/packets/arp.rb

@@ -0,0 +1,111 @@
+require 'pcap_ffi/packets/typedefs'
+require 'pcap_ffi/mac_addr'
+require 'pcap_ffi/in_addr'
+require 'pcap_ffi/packet'
+
+require 'ffi'
+
+module FFI
+  module PCap
+    module Packets
+      # Note that ARP only supports Ethernet, ipv4 right now
+      class Arp < FFI::Struct
+
+        include Packet
+
+        HW_ETHERNET = 0x0001
+        PROTCOL_IP  = 0x0002
+        OP_REQUEST = 0x0001
+        OP_REPLY   = 0x0002
+
+        layout :h_type,     :uint16,
+               :p_type,     :uint16,
+               :h_len,      :uint8,
+               :p_len,      :uint8,
+               :operation,  :uint16,
+               :sender_mac, MACAddr,
+               :sender_ip,  InAddr,
+               :dest_mac,   MACAddr,
+               :dest_ip,    InAddr
+
+        #
+        # Returns ARP hardware type
+        #
+        def hardware_type
+          self[:h_type].to_endian(:big)
+        end
+
+        #
+        # Returns ARP protocol type
+        #
+        def protocol_type
+          self[:p_type].to_endian(:big)
+        end
+
+        #
+        # Returns true if ARP request hardware type is Ethernet
+        #
+        def hardware_ethernet?
+          self.hardware_type == HW_ETHERNET
+        end
+
+        #
+        # Returns true if ARP request protocol type is IP
+        #
+        def protocol_ip?
+          self.protocol_type == PROTOCOL_IP
+        end
+
+        #
+        # Returns the ARP operation
+        #
+        def operation
+          self[:operation].to_endian(:big)
+        end
+
+        #
+        # Returns true if it was an ARP request operation
+        # 
+        def request?
+          self.operation == OP_REQUEST
+        end
+
+        #
+        # Returns true if it was an ARP reply operation
+        # 
+        def reply?
+          self.operation == OP_REPLY
+        end
+
+        #
+        # Returns the source MAC address.
+        #
+        def src_mac
+          self[:sender_mac]
+        end
+
+        #
+        # Returns the destination MAC address.
+        #
+        def dest_mac
+          self[:dest_mac]
+        end
+
+        #
+        # Returns the source IP address.
+        #
+        def src_ip
+          self[:sender_ip]
+        end
+
+        #
+        # Returns the destination IP address.
+        #
+        def dest_ip
+          self[:dest_ip]
+        end
+
+      end
+    end
+  end
+end