NAME

Net::Packet::IPv4 - Internet Protocol v4 layer 3 object

SYNOPSIS

use Net::Packet::IPv4;
use Net::Packet::Consts qw(:ipv4);

# Build layer to inject to network
my $ip = Net::Packet::IPv4->new(
   flags => NP_IPv4_DONT_FRAGMENT,
   dst   => "192.168.0.1",
);

# Decode from network to create the object
# Usually, you do not use this, it is used by Net::Packet::Frame
my $ip2 = Net::Packet::IPv4->new(raw => $rawFromNetwork);

print $ip->print, "\n";

DESCRIPTION

This modules implements the encoding and decoding of the IPv4 layer.

RFC: ftp://ftp.rfc-editor.org/in-notes/rfc791.txt

See also Net::Packet::Layer and Net::Packet::Layer3 for other attributes and methods.

ATTRIBUTES

id

IP ID of the datagram.

ttl

Time to live.

src

dst

Source and destination IP addresses.

protocol

Of which type the layer 4 is.

checksum

IP checksum.

flags

IP Flags.

offset

IP fragment offset.

version

IP version, here it is 4.

tos

Type of service flag.

length

Total length in bytes of the packet, including IP headers (that is, layer 3 + layer 4 + layer 7).

hlen

Header length in number of words, including IP options.

options

IP options, as a hexadecimal string.

noFixLen

Since the byte ordering of length attribute varies from system to system, a subroutine inside this module detects which byte order to use. Sometimes, like when you build Net::Packet::VLAN layers, you may have the need to avoid this. So set it to 1 in order to avoid fixing. Default is 0 (that is to fix).

doChecksum

Usually the IP checksum is done by the system. But if you inject some frames into network somewhere (well, err...), this checksum could be not computed. So, you can enable it by setting this attribute to 1. Default 0, to let the system compute it.

METHODS

new

Object constructor. You can pass attributes that will overwrite default ones. Default values:

version: 4

tos: 0

id: getRandom16bitsInt()

length: 0

hlen: 0

flags: 0

offset: 0

ttl: 128

protocol: NP_IPv4_PROTOCOL_TCP

checksum: 0

src: $Env->ip

dst: "127.0.0.1"

options: ""

noFixLen: 0

doChecksum: 0

pack

Packs all attributes into a raw format, in order to inject to network. Returns 1 on success, undef otherwise.

unpack

Unpacks raw data from network and stores attributes into the object. Returns 1 on success, undef otherwise.

getHeaderLength

Returns the header length in bytes, not including IP options.

getPayloadLength

Returns the length in bytes of encapsulated layers (that is, layer 4 + layer 7).

getOptionsLength

Returns the length in bytes of IP options.

haveFlagDf

haveFlagMf

haveFlagRf

Returns 1 if the specified flag is set in flags attribute, 0 otherwise.

isProtocolTcp

isProtocolUdp

isProtocolIcmpv4

Returns 1 if the specified protocol is used at layer 4, 0 otherwise.

CONSTANTS

Load them: use Net::Packet::Consts qw(:ipv4);

NP_IPv4_PROTOCOL_TCP

NP_IPv4_PROTOCOL_UDP

NP_IPv4_PROTOCOL_ICMPv4

Various protocol type constants.

NP_IPv4_MORE_FRAGMENT

NP_IPv4_DONT_FRAGMENT

NP_IPv4_RESERVED_FRAGMENT

Various possible flags.

AUTHOR

Patrice <GomoR> Auffret

COPYRIGHT AND LICENSE

Copyright (c) 2004-2006, Patrice <GomoR> Auffret

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