Net::Frame::Layer::TCP - Transmission Control Protocol layer object

   use Net::Frame::Layer::TCP qw(:consts);

   # Build a layer
   my $layer = Net::Frame::Layer::TCP->new(
      src      => getRandomHighPort(),
      dst      => 0,
      seq      => getRandom32bitsInt(),
      ack      => 0,
      x2       => 0,
      off      => 0,
      flags    => NF_TCP_FLAGS_SYN,
      win      => 0xffff,
      checksum => 0,
      urp      => 0,
      options  => '',
   );
   $layer->pack;

   print 'RAW: '.$layer->dump."\n";

   # Read a raw layer
   my $layer = Net::Frame::Layer::TCP->new(raw => $raw);

   print $layer->print."\n";
   print 'PAYLOAD: '.unpack('H*', $layer->payload)."\n"
      if $layer->payload;

#
# $Id: TCP.pm 333 2011-02-16 10:47:33Z gomor $
#
package Net::Frame::Layer::TCP;
use strict; use warnings;

use Net::Frame::Layer qw(:consts :subs);
use Exporter;
our @ISA = qw(Net::Frame::Layer Exporter);

our %EXPORT_TAGS = (
   consts => [qw(
      NF_TCP_HDR_LEN
      NF_TCP_FLAGS_FIN
      NF_TCP_FLAGS_SYN
      NF_TCP_FLAGS_RST
      NF_TCP_FLAGS_PSH
      NF_TCP_FLAGS_ACK
      NF_TCP_FLAGS_URG
      NF_TCP_FLAGS_ECE
      NF_TCP_FLAGS_CWR
   )],
);
our @EXPORT_OK = (
   @{$EXPORT_TAGS{consts}},
);

use constant NF_TCP_HDR_LEN  => 20;
use constant NF_TCP_FLAGS_FIN => 0x01;
use constant NF_TCP_FLAGS_SYN => 0x02;
use constant NF_TCP_FLAGS_RST => 0x04;
use constant NF_TCP_FLAGS_PSH => 0x08;
use constant NF_TCP_FLAGS_ACK => 0x10;
use constant NF_TCP_FLAGS_URG => 0x20;
use constant NF_TCP_FLAGS_ECE => 0x40;
use constant NF_TCP_FLAGS_CWR => 0x80;

our @AS = qw(
   src
   dst
   flags
   win
   seq
   ack
   off
   x2
   checksum
   urp
   options
);
__PACKAGE__->cgBuildIndices;
__PACKAGE__->cgBuildAccessorsScalar(\@AS);

no strict 'vars';

sub new {
   shift->SUPER::new(
      src      => getRandomHighPort(),
      dst      => 0,
      seq      => getRandom32bitsInt(),
      ack      => 0,
      x2       => 0,
      off      => 0,
      flags    => NF_TCP_FLAGS_SYN,
      win      => 0xffff,
      checksum => 0,
      urp      => 0,
      options  => '',
      @_,
   );
}

sub pack {
   my $self = shift;

   my $offX2Flags = ($self->[$__off] << 12)|(0x0f00 & ($self->[$__x2] << 8))
      |(0x00ff & $self->[$__flags]);

   $self->[$__raw] = $self->SUPER::pack('nnNNnnnn',
      $self->[$__src],
      $self->[$__dst],
      $self->[$__seq],
      $self->[$__ack],
      $offX2Flags,
      $self->[$__win],
      $self->[$__checksum],
      $self->[$__urp],
   ) or return;

   if ($self->[$__options]) {
      $self->[$__raw] =
         $self->[$__raw].$self->SUPER::pack('a*', $self->[$__options])
            or return;
   }

   return $self->[$__raw];
}

sub unpack {
   my $self = shift;

   # Pad it if less than the required length
   if (length($self->[$__raw]) < NF_TCP_HDR_LEN) {
      $self->[$__raw] .= ("\x00" x (NF_TCP_HDR_LEN - length($self->[$__raw])));
   }

   my ($src, $dst, $seq, $ack, $offX2Flags, $win, $checksum, $urp, $payload) =
      $self->SUPER::unpack('nnNNnnnn a*', $self->[$__raw])
         or return;

   $self->[$__src]      = $src;
   $self->[$__dst]      = $dst;
   $self->[$__seq]      = $seq;
   $self->[$__ack]      = $ack;
   $self->[$__off]      = ($offX2Flags & 0xf000) >> 12;
   $self->[$__x2]       = ($offX2Flags & 0x0f00) >> 8;
   $self->[$__flags]    = $offX2Flags & 0x00ff;
   $self->[$__win]      = $win;
   $self->[$__checksum] = $checksum;
   $self->[$__urp]      = $urp;
   $self->[$__payload]  = $payload;

   my ($options, $payload2) = $self->SUPER::unpack(
      'a'. $self->getOptionsLength. 'a*', $self->[$__payload]
   ) or return;

   $self->[$__options] = $options;
   $self->[$__payload] = $payload2;

   return $self;
}

sub getLength { my $self = shift; $self->[$__off] ? $self->[$__off] * 4 : 0 }

sub getOptionsLength {
   my $self = shift;
   my $gLen = $self->getLength;
   my $hLen = NF_TCP_HDR_LEN;
   $gLen > $hLen ? $gLen - $hLen : 0;
}

sub getPayloadLength { shift->SUPER::getPayloadLength }

sub computeLengths {
   my $self = shift;

   my $optLen = ($self->[$__options] && length($self->[$__options])) || 0;

   my $hLen = NF_TCP_HDR_LEN;
   $self->[$__off] = ($hLen + $optLen) / 4;
}

sub computeChecksums {
   my $self = shift;
   my ($layers) = @_;

   my $payloadLength = $self->getLength + $self->getPayloadLength;

   my $phpkt;
   for my $l (@$layers) {
      if ($l->layer eq 'IPv4') {
         $phpkt = $self->SUPER::pack('a4a4CCn',
            inetAton($l->src), inetAton($l->dst), 0, 6, $payloadLength);
         last;
      }
      elsif ($l->layer eq 'IPv6') {
         $phpkt = $self->SUPER::pack('a*a*NnCC',
            inet6Aton($l->src), inet6Aton($l->dst), $payloadLength, 0, 0, 6);
         last;
      }
   }

   my $offX2Flags = ($self->[$__off] << 12) | (0x0f00 & ($self->[$__x2] << 8))
                  | (0x00ff & $self->[$__flags]);

   $phpkt .= $self->SUPER::pack('nnNNnnnn',
      $self->[$__src], $self->[$__dst], $self->[$__seq], $self->[$__ack],
      $offX2Flags, $self->[$__win], 0, $self->[$__urp],
   ) or return;

   if ($self->[$__options]) {
      $phpkt .= $self->SUPER::pack('a*', $self->[$__options])
         or return;
   }

   my $last = $layers->[-1];
   if (defined($last->payload) && length($last->payload)) {
      $phpkt .= $self->SUPER::pack('a*', $last->payload)
         or return;
   }

   $self->[$__checksum] = inetChecksum($phpkt);

   return 1;
}

our $Next = {
};

sub encapsulate {
   my $self = shift;
   return $Next->{$self->[$__dst]} || $Next->{$self->[$__src]}
                                   || $self->[$__nextLayer];
}

sub match {
   my $self = shift;
   my ($with) = @_;
      ($with->[$__ack] == $self->[$__seq] + 1)
   || ($with->[$__flags] & NF_TCP_FLAGS_RST);
}

sub getKey {
   my $self = shift;
   $self->layer.':'.$self->[$__src].'-'.$self->[$__dst];
}

sub getKeyReverse {
   my $self = shift;
   $self->layer.':'.$self->[$__dst].'-'.$self->[$__src];
}

sub print {
   my $self = shift;

   my $l = $self->layer;
   my $buf = sprintf
      "$l: src:%d  dst:%d  seq:0x%04x  ack:0x%04x \n".
      "$l: off:0x%02x  x2:0x%01x  flags:0x%02x  win:%d  checksum:0x%04x  ".
      "urp:0x%02x",
         $self->[$__src], $self->[$__dst], $self->[$__seq], $self->[$__ack],
         $self->[$__off], $self->[$__x2], $self->[$__flags], $self->[$__win],
         $self->[$__checksum], $self->[$__urp];

   if ($self->[$__options]) {
      $buf .= sprintf("\n$l: optionsLength:%d  options:%s",
         $self->getOptionsLength,
         $self->SUPER::unpack('H*', $self->[$__options])
      ) or return undef;
   }

   $buf;
}

1;

__END__