Class: Mu::Pcap::Ethernet

Inherits:
Packet
  • Object
show all
Defined in:
lib/mu/pcap/ethernet.rb

Constant Summary collapse

ETHERTYPE_IP = 
0x0800
ETHERTYPE_IP6 = 
0x86dd
ETHERTYPE_ARP = 
0x0806
ETHERTYPE_PPPOE_SESSION = 
0x8864
ETHERTYPE_802_1Q = 
0X8100
PPP_IP = 
0x0021
PPP_IPV6 = 
0x0057
FMT_MAC = 
"C6"
FMT_n = 
'n'
MAC_TEMPLATE = 
'%02x:%02x:%02x:%02x:%02x:%02x'
ADDR_TO_BYTES = 
{}
FMT_HEADER = 
'a6a6n'

Constants inherited from Packet

Packet::IGNORE_UDP_PORTS

Instance Attribute Summary collapse

Attributes inherited from Packet

#payload, #payload_raw

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Packet

#deepdup, isolate_l7, normalize, #payload_bytes, #to_bytes

Constructor Details

#initialize(src = nil, dst = nil, type = 0) ⇒ Ethernet

Returns a new instance of Ethernet.



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# File 'lib/mu/pcap/ethernet.rb', line 20

def initialize src=nil, dst=nil, type=0
    super()
    @src = src
    @dst = dst
    @type = type
end

Instance Attribute Details

#dst ⇒ Object

Returns the value of attribute dst.



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# File 'lib/mu/pcap/ethernet.rb', line 9

def dst
  @dst
end

#src ⇒ Object

Returns the value of attribute src.



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# File 'lib/mu/pcap/ethernet.rb', line 9

def src
  @src
end

#type ⇒ Object

Returns the value of attribute type.



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# File 'lib/mu/pcap/ethernet.rb', line 9

def type
  @type
end

Class Method Details

.from_bytes(bytes) ⇒ Object 



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# File 'lib/mu/pcap/ethernet.rb', line 38

def self.from_bytes bytes
    if bytes.length < 14
        raise ParseError, "Truncated Ethernet header: expected 14 bytes, got #{bytes.length} bytes"
    end

    dst = bytes.slice!(0,6).unpack FMT_MAC
    dst = MAC_TEMPLATE % dst
    src = bytes.slice!(0,6).unpack FMT_MAC
    src = MAC_TEMPLATE % src
    type = bytes.slice!(0,2).unpack(FMT_n)[0]
    while (type == ETHERTYPE_802_1Q)
        # Skip 4 bytes for 802.1q vlan tag field
        bytes.slice!(0,2)
        type = bytes.slice!(0,2).unpack(FMT_n)[0]
    end
    ethernet = Ethernet.new src, dst, type
    ethernet.payload = bytes
    ethernet.payload_raw = bytes
    begin
        case type
        when ETHERTYPE_IP
            ethernet.payload = IPv4.from_bytes bytes
        when ETHERTYPE_IP6
            ethernet.payload = IPv6.from_bytes bytes
        when ETHERTYPE_PPPOE_SESSION
            # Remove PPPoE/PPP session layer
            ethernet.payload = bytes
            ethernet.remove_pppoe!
        else
            ethernet.payload = bytes
        end
    rescue ParseError => e
        Pcap.warning e
    end
    return ethernet
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/mu/pcap/ethernet.rb', line 139

def == other
    return super &&
        self.src  == other.src &&
        self.dst  == other.dst &&
        self.type == other.type
end

#flow_id ⇒ Object 



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# File 'lib/mu/pcap/ethernet.rb', line 27

def flow_id
    if not @payload or @payload.is_a? String
        return [:ethernet, @src, @dst, @type]
    else
        return @payload.flow_id
    end
end

#ip? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/mu/pcap/ethernet.rb', line 75

def ip?
    return payload.is_a?(IP)
end

#remove_pppoe! ⇒ Object

Remove the PPPoE and PPP headers. PPPoE is documented in RFC 2516.



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# File 'lib/mu/pcap/ethernet.rb', line 94

def remove_pppoe!
    bytes = self.payload_raw

    # Remove PPPoE header
    Pcap.assert bytes.length >= 6, 'Truncated PPPoE header: ' +
        "expected at least 6 bytes, got #{bytes.length} bytes"
    version_type, code, session_id, length = bytes.unpack 'CCnn'
    version = version_type >> 4 & 0b1111
    type    = version_type      & 0b1111
    Pcap.assert version == 1, "Unknown PPPoE version: #{version}"
    Pcap.assert type == 1, "Unknown PPPoE type: #{type}"
    Pcap.assert code == 0, "Unknown PPPoE code: #{code}"
    bytes = bytes[6..-1]
    Pcap.assert bytes.length >= length, 'Truncated PPoE packet: ' +
        "expected #{length} bytes, got #{bytes.length} bytes"
    
    # Remove PPP header
    Pcap.assert bytes.length >= 2, 'Truncated PPP packet: ' +
        "expected at least bytes, got #{bytes.length} bytes"
    protocol_id, = bytes.unpack 'n'
    bytes = bytes[2..-1]
    case protocol_id
    when PPP_IP
        self.payload = IPv4.from_bytes bytes
        self.payload_raw = bytes
        self.type = ETHERTYPE_IP
    when PPP_IPV6
        self.payload = IPv6.from_bytes bytes
        self.payload_raw = bytes
        self.type = ETHERTYPE_IP6
    else
        # Failed.  Don't update payload or type.
        raise ParseError, "Unknown PPP protocol: 0x#{'%04x' % protocol_id}"
    end
end

#to_s ⇒ Object 



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# File 'lib/mu/pcap/ethernet.rb', line 130

def to_s
    if @payload.is_a? String
        payload = @payload.inspect
    else
        payload = @payload.to_s
    end
    return "ethernet(%s, %s, %d, %s)" % [@src, @dst, @type, payload]
end

#write(io) ⇒ Object 



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# File 'lib/mu/pcap/ethernet.rb', line 81

def write io
    dst_mac = ADDR_TO_BYTES[@dst] ||= @dst.split(':').inject('') {|m, b| m << b.to_i(16).chr}
    src_mac = ADDR_TO_BYTES[@src] ||= @src.split(':').inject('') {|m, b| m << b.to_i(16).chr}
    bytes = [dst_mac, src_mac, @type].pack(FMT_HEADER)
    io.write bytes
    if @payload.is_a? String
        io.write @payload
    else
        @payload.write io
    end
end