Net::Packet::Frame

Section: User Contributed Perl Documentation (3pm)
Updated: 2009-11-09
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NAME

Net::Packet::Frame - object encapsulator for Net::Packet layers

SYNOPSIS

   require Net::Packet::Frame;

   # Because we passed a layer 3 object, a Net::Packet::DescL3 object 
   # will be created automatically, by default. See Net::Packet::Env 
   # regarding changing this behaviour. Same for Net::Packet::Dump.
   my $frame = Net::Packet::Frame->new(
      l3 => $ipv4,  # Net::Packet::IPv4 object
      l4 => $tcp,   # Net::Packet::TCP object
                    # (here, a SYN request, for example)
   );

   # Without retries
   $frame->send;
   sleep(3);
   if (my $reply = $frame->recv) {
      print $reply->l3->print."\n";
      print $reply->l4->print."\n";
   }

   # Or with retries
   for (1..3) {
      $frame->reSend;

      until ($Env->dump->timeout) {
         if (my $reply = $frame->recv) {
            print $reply->l3->print."\n";
            print $reply->l4->print."\n";
            last;
         }
      }
   }

DESCRIPTION

In Net::Packet, each sent and/or received frame is parsed and converted into a Net::Packet::Frame object. Basically, it encapsulates various layers (2, 3, 4 and 7) into an object, making it easy to get or set information about it.

When you create a frame object, a Net::Packet::Desc object is created if none is found in the default $Env object (from Net::Packet module), and a Net::Packet::Dump object is also created if none is found in this same $Env object. You can change this beheaviour, see Net::Packet::Env.

Two new invocation method exist, one with attributes passing, another with raw attribute. This second method is usually used internally, in order to unpack received frame into all corresponding layers.

ATTRIBUTES

env: Stores the Net::Packet::Env object. The default is to use $Env from Net::Packet. So, you can send/recv frames to/from different environements.
raw: Pass this attribute when you want to decode a raw string captured from network. Usually used internally.
padding: In Ethernet world, a frame should be at least 60 bytes in length. So when you send frames at layer 2, a padding is added in order to achieve this length, avoiding a local memory leak to network. Also, when you receive a frame from network, this attribute is filled with what have been used to pad it. This padding feature currently works for IPv4 and ARP frames.
l2: Stores a layer 2 object. See Net::Packet for layer 2 classes hierarchy.
l3: Stores a layer 3 object. See Net::Packet for layer 3 classes hierarchy.
l4: Stores a layer 4 object. See Net::Packet for layer 4 classes hierarchy.
l7: Stores a layer 7 object. See Net::Packet::Layer7.
reply: When recv method has been called on a frame object, and a corresponding reply has been catched, a pointer is stored in this attribute.
timestamp: When a frame is packed/unpacked, the happening time is stored here.
encapsulate: Give the type of the first encapsulated layer. It is a requirement to parse a user provided raw string.

METHODS

new

Object constructor. If a $Env-desc> object does not exists, one is created by analyzing attributes (so, either one of Net::Packet::DescL2, Net::Packet::DescL3. Net::Packet::DescL4 cannot be created automatically for now). The same behaviour is true for $Env-dump> object. You can change this default creation behaviour, see Net::Packet::Env. Default values:

timestamp: gettimeofday(),

env: $Env

getLengthFromL7

getLengthFromL4

getLengthFromL3

getLengthFromL2

Returns the raw length in bytes from specified layer.

getLength

Alias for getLengthFromL3.

unpack

Unpacks the raw string from network into various layers. Returns 1 on success, undef on failure.

pack

Packs various layers into the raw string to send to network. Returns 1 on success, undef on failure.

send

On the first send invocation in your program, the previously created Net::Packet::Dump object is started (if available). That is, packet capturing is run. The timestamp attribute is set to the sending time. The env attribute is used to know where to send this frame.

reSend

Will call send method if no frame has been recv'd, that is the reply attribute is undef.

getFilter

Will return a string which is a pcap filter, and corresponding to what you should receive compared with the frame request.

recv

Searches framesSorted or frames from Net::Packet::Dump for a matching response. If a reply has already been received (that is reply attribute is already set), undef is returned. It no reply is received, return undef, else the Net::Packet::Frame response.

print

Just returns a string in a human readable format describing attributes found in the layer.

dump

Just returns a string in hexadecimal format which is how the layer appears on the network.

isEth

isRaw

isNull

isSll

isPpp

isArp

isIpv4

isIpv6

isIp - either IPv4 or IPv6

isPpplcp

isVlan

isPppoe

isLlc

isTcp

isUdp

isIcmpv4

isIcmp - currently only ICMPv4

isCdp

isStp

isOspf

isIgmpv4

is7

Returns 1 if the Net::Packet::Frame is of specified layer, 0 otherwise.

AUTHOR

Patrice <GomoR> Auffret

COPYRIGHT AND LICENSE

You may distribute this module under the terms of the Artistic license. See LICENSE.Artistic file in the source distribution archive.

RELATED MODULES

NetPacket, Net::RawIP, Net::RawSock

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