Net::BGP::Update - Class encapsulating BGP-4 UPDATE message

Net-BGP documentation Contained in the Net-BGP distribution.

Index

Code Index:

NAME

Top

Net::BGP::Update - Class encapsulating BGP-4 UPDATE message

SYNOPSIS

Top

    use Net::BGP::Update qw( :origin );

    # Constructor
    $update = Net::BGP::Update->new(
        NLRI            => [ qw( 10/8 172.168/16 ) ],
        Withdraw        => [ qw( 192.168.1/24 172.10/16 192.168.2.1/32 ) ],
	# For Net::BGP::NLRI
        Aggregator      => [ 64512, '10.0.0.1' ],
        AsPath          => [ 64512, 64513, 64514 ],
        AtomicAggregate => 1,
        Communities     => [ qw( 64512:10000 64512:10001 ) ],
        LocalPref       => 100,
        MED             => 200,
        NextHop         => '10.0.0.1',
        Origin          => INCOMPLETE,
    );

    # Construction from a NLRI object:
    $nlri = Net::BGP::NLRI->new( ... );
    $update = Net::BGP::Update->new($nlri,$nlri_ref,$withdrawn_ref);

    # Object Copy
    $clone = $update->clone();

    # Accessor Methods
    $nlri_ref         = $update->nlri($nlri_ref);
    $withdrawn_ref    = $update->withdrawn($withdrawn_ref);
    $prefix_hash_ref  = $update->ashash;

    # Comparison
    if ($update1 eq $update2) { ... }
    if ($update1 ne $update2) { ... }

DESCRIPTION

Top

This module encapsulates the data contained in a BGP-4 UPDATE message. It provides a constructor, and accessor methods for each of the message fields and well-known path attributes of an UPDATE. Whenever a Net::BGP::Peer sends an UPDATE message to its peer, it does so by passing a Net::BGP::Update object to the peer object's update() method. Similarly, when the peer receives an UPDATE message from its peer, the UPDATE callback is called and passed a reference to a Net::BGP::Update object. The callback function can then examine the UPDATE message fields by means of the accessor methods.

CONSTRUCTOR

Top

new() - create a new Net::BGP::Update object

    $update = Net::BGP::Update->new(
        NLRI            => [ qw( 10/8 172.168/16 ) ],
        Withdraw        => [ qw( 192.168.1/24 172.10/16 192.168.2.1/32 ) ],
	# For Net::BGP::NLRI
        Aggregator      => [ 64512, '10.0.0.1' ],
        AsPath          => [ 64512, 64513, 64514 ],
        AtomicAggregate => 1,
        Communities     => [ qw( 64512:10000 64512:10001 ) ],
        LocalPref       => 100,
        MED             => 200,
        NextHop         => '10.0.0.1',
        Origin          => INCOMPLETE,
    );

This is the constructor for Net::BGP::Update objects. It returns a reference to the newly created object. The following named parameters may be passed to the constructor. See RFC 1771 for the semantics of each path attribute.

An alternative is to construct an object from a Net::BGP::NLRI object:

    $nlri = Net::BGP::NLRI->new( ... );
    $nlri_ref = [ qw( 10/8 172.168/16 ) ];
    $withdrawn_ref = [ qw( 192.168.1/24 172.10/16 192.168.2.1/32 ) ];
    $update = Net::BGP::Update->new($nlri,$nlri_ref,$withdrawn_ref);

The NLRI object will not be modified in any way.

NLRI

This parameter corresponds to the Network Layer Reachability Information (NLRI) field of an UPDATE message. It represents the route(s) being advertised in this particular UPDATE. It is expressed as an array reference of route prefixes which are encoded in a special format as perl strings: XXX.XXX.XXX.XXX/XX. The part preceding the slash is a dotted-decimal notation IP prefix. Only as many octets as are significant according to the mask need to be specified. The part following the slash is the mask which is an integer in the range [0,32] which indicates how many bits are significant in the prefix. At least one of either the NLRI or Withdraw parameters is mandatory and must always be provided to the constructor.

Withdraw

This parameter corresponds to the Withdrawn Routes field of an UPDATE message. It represents route(s) advertised by a previous UPDATE message which are now being withdrawn by this UPDATE. It is expressed in the same way as the NLRI parameter. At least one of either the NLRI or Withdraw parameters is mandatory and must always be provided to the constructor.

OBJECT COPY

Top

clone() - clone a Net::BGP::Update object

    $clone = $update->clone();

This method creates an exact copy of the Net::BGP::Update object, with Withdrawn Routes, Path Attributes, and NLRI fields matching those of the original object. This is useful for propagating a modified UPDATE message when the original object needs to remain unchanged.

ACCESSOR METHODS

Top

nlri()

withdrawn()

These accessor methods return the value(s) of the associated UPDATE message field if called with no arguments. If called with arguments, they set the associated field. The representation of parameters and return values is the same as described for the corresponding named constructor parameters above.

ashash()

This method returns a hash reference index on the prefixes in found in the nlri and withdrawn fields. Withdrawn networks has undefined as value, while nlri prefixes all has the same reference to a Net::BGP::NLRI object matching the Update object self.

EXPORTS

Top

The module does not export anything.

SEE ALSO

Top

RFC 1771, RFC 1997, Net::BGP, Net::BGP::Process, Net::BGP::Peer, Net::BGP::Notification, Net::BGP::NLRI

AUTHOR

Top

Stephen J. Scheck <code@neurosphere.com>

Net-BGP documentation Contained in the Net-BGP distribution. 
#!/usr/bin/perl

package Net::BGP::Update;
use bytes;

use strict;
use vars qw(
    $VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS
    @BGP_PATH_ATTR_FLAGS
);

## Inheritance and Versioning ##

use Net::BGP::NLRI qw( :origin );

@ISA     = qw( Exporter Net::BGP::NLRI );
$VERSION = '0.14';

## Module Imports ##

use Carp;
use IO::Socket;
use Net::BGP::Notification qw( :errors );

## General Definitions ##

sub TRUE  { 1 }
sub FALSE { 0 }

## BGP Path Attribute Type Enumerations ##

sub BGP_PATH_ATTR_ORIGIN           { 1 }
sub BGP_PATH_ATTR_AS_PATH          { 2 }
sub BGP_PATH_ATTR_NEXT_HOP         { 3 }
sub BGP_PATH_ATTR_MULTI_EXIT_DISC  { 4 }
sub BGP_PATH_ATTR_LOCAL_PREF       { 5 }
sub BGP_PATH_ATTR_ATOMIC_AGGREGATE { 6 }
sub BGP_PATH_ATTR_AGGREGATOR       { 7 }
sub BGP_PATH_ATTR_COMMUNITIES      { 8 }

## BGP Path Attribute Flag Octets ##

@BGP_PATH_ATTR_FLAGS = (
    0x00, ## TODO: change to undef after warnings enabled
    0x40,
    0x40,
    0x40,
    0x80,
    0x40,
    0x40,
    0xC0,
    0xC0
);

## RFC 4271, sec 4.3
our $BGP_PATH_ATTR_FLAG_EXTLEN = 0x10;

## Per RFC 4271, sec 5.
##
our @_BGP_MANDATORY_ATTRS = ( BGP_PATH_ATTR_ORIGIN,
                              BGP_PATH_ATTR_AS_PATH,
                              BGP_PATH_ATTR_NEXT_HOP );

## Export Tag Definitions ##

@EXPORT      = ();
@EXPORT_OK   = ();
%EXPORT_TAGS = (
    ALL    => [ @EXPORT, @EXPORT_OK ]
);

## Public Methods ##

sub new
{
    my $proto = shift;
    my $class = ref $proto || $proto;

    if (ref $_[0] eq 'Net::BGP::NLRI')
     { # Construct from NLRI
       $proto = shift unless ref $proto;
       my $this = $proto->clone;
       bless($this,$class);
       $this->nlri(shift);
       $this->withdrawn(shift);
       return $this;
     };

    my ($arg, $value);
    my @super_arg;
    my %this_arg;
    $this_arg{_withdrawn} = [];
    $this_arg{_nlri} = [];

    while ( defined($arg = shift()) ) {
        $value = shift();

        if ( $arg =~ /nlri/i ) {
            $this_arg{_nlri} = $value;
        }
        elsif ( $arg =~ /withdraw/i ) {
            $this_arg{_withdrawn} = $value;
        }
        else {
            push(@super_arg,$arg,$value);
        }
    }

    my $this = $class->SUPER::new(@super_arg);

    @{$this}{keys %this_arg} = values(%this_arg);

    bless($this, $class);

    return ( $this );
}

sub clone
{
    my $proto = shift;
    my $class = ref $proto || $proto;
    $proto = shift unless ref $proto;

    my $clone = $class->SUPER::clone($proto);

    foreach my $key (qw(_nlri _withdrawn ))
     {
      $clone->{$key} = [ @{$proto->{$key}} ];
     }

    return ( bless($clone, $class) );
}

sub nlri
{
    my $this = shift();

    $this->{_nlri} = @_ ? shift() : $this->{_nlri};
    return ( $this->{_nlri} );
}

sub withdrawn
{
    my $this = shift();

    $this->{_withdrawn} = @_ ? shift() : $this->{_withdrawn};
    return ( $this->{_withdrawn} );
}

sub ashash
{
    my $this = shift();

    my (%res,$nlri);

    $nlri = clone Net::BGP::NLRI($this) if defined($this->{_nlri});

    foreach my $prefix (@{$this->{_nlri}})
     {
      $res{$prefix} = $nlri;
     };

    foreach my $prefix (@{$this->withdrawn})
     {
      $res{$prefix} = undef;
     };

    return \%res;
}

## Private Methods ##

sub _new_from_msg
{
    my ($class, $buffer) = @_;

    my $this = $class->new();

    $this->_decode_message($buffer);

    return $this;
}

sub _encode_attr
{
    my ($this, $type, $data) = @_;
    my $buffer = '';

    my $flag = $BGP_PATH_ATTR_FLAGS[$type];
    my $len_format = 'C';

    my $len = length($data);
    if ($len > 255)
    {
        $flag |= $BGP_PATH_ATTR_FLAG_EXTLEN;
        $len_format = 'n';
    }

    $buffer .= pack('CC', $flag, $type);
    $buffer .= pack($len_format, $len);
    $buffer .= $data;

    return ( $buffer );
}

sub _decode_message
{
    my ($this, $buffer) = @_;

    my $offset = 0;
    my $length;

    # decode the Withdrawn Routes field
    $length = unpack('n', substr($buffer, $offset, 2));
    $offset += 2;

    if ( $length > (length($buffer) - $offset) ) {
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_MALFORMED_ATTR_LIST
        );
    }

    $this->_decode_withdrawn(substr($buffer, $offset, $length));
    $offset += $length;

    # decode the Path Attributes field
    $length = unpack('n', substr($buffer, $offset, 2));
    $offset += 2;

    if ( $length > (length($buffer) - $offset) ) {
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_MALFORMED_ATTR_LIST
        );
    }

    return if $length == 0;    # withdrawn routes only

    $this->_decode_path_attributes(substr($buffer, $offset, $length));
    $offset += $length;

    # decode the Network Layer Reachability Information field
    $this->_decode_nlri(substr($buffer, $offset));
}

sub _decode_origin
{
    my ($this, $buffer) = @_;

    $this->{_origin} = unpack('C', $buffer);
    $this->{_attr_mask}->[BGP_PATH_ATTR_ORIGIN] ++;

    return ( undef );
}

sub _decode_as_path
{
    my ($this, $buffer) = @_;

    my $path = Net::BGP::ASPath->_new_from_msg($buffer);

    $this->{_as_path} = $path;

    $this->{_attr_mask}->[BGP_PATH_ATTR_AS_PATH] ++;

    return ( undef );
}

sub _decode_next_hop
{
    my ($this, $buffer) = @_;
    my ($data);

    if ( length($buffer) != 0x04 ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_NEXT_HOP, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    # TODO: check if _next_hop is a valid IP host address
    $this->{_next_hop} = inet_ntoa($buffer);
    $this->{_attr_mask}->[BGP_PATH_ATTR_NEXT_HOP] ++;

    return ( undef );
}

sub _decode_med
{
    my ($this, $buffer) = @_;
    my ($data);

    if ( length($buffer) != 0x04 ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_MULTI_EXIT_DISC, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    $this->{_med} = unpack('N', $buffer);
    $this->{_attr_mask}->[BGP_PATH_ATTR_MULTI_EXIT_DISC] ++;

    return ( undef );
}

sub _decode_local_pref
{
    my ($this, $buffer) = @_;
    my ($data);

    if ( length($buffer) != 0x04 ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_LOCAL_PREF, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    $this->{_local_pref} = unpack('N', $buffer);
    $this->{_attr_mask}->[BGP_PATH_ATTR_LOCAL_PREF] ++;

    return ( undef );
}

sub _decode_atomic_aggregate
{
    my ($this, $buffer) = @_;
    my ($data);

    if ( length($buffer) ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_ATOMIC_AGGREGATE, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    $this->{_atomic_agg} = TRUE;
    $this->{_attr_mask}->[BGP_PATH_ATTR_ATOMIC_AGGREGATE] ++;

    return ( undef );
}

sub _decode_aggregator
{
    my ($this, $buffer) = @_;
    my ($data);

    if ( length($buffer) != 0x06 ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_AGGREGATOR, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    $this->{_aggregator}->[0] = unpack('n', substr($buffer, 0, 2));
    $this->{_aggregator}->[1] = inet_ntoa(substr($buffer, 2, 4));
    $this->{_attr_mask}->[BGP_PATH_ATTR_AGGREGATOR] ++;

    return ( undef );
}

sub _decode_communities
{
    my ($this, $buffer) = @_;
    my ($as, $val, $ii, $offset, $count);
    my ($data);

    if ( length($buffer) % 0x04 ) {
        $data = $this->_encode_attr(BGP_PATH_ATTR_COMMUNITIES, $buffer);
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
            ErrorData    => $data
        );
    }

    $offset = 0;
    $count = length($buffer) / 4;
    for ( $ii = 0; $ii < $count; $ii++ ) {
        $as  = unpack('n', substr($buffer, $offset, 2));
        $val = unpack('n', substr($buffer, $offset + 2, 2));
        push(@{$this->{_communities}}, join(":", $as, $val));
        $offset += 4;
    }

    $this->{_attr_mask}->[BGP_PATH_ATTR_COMMUNITIES] ++;

    return ( undef );
}

sub _decode_path_attributes
{
    my ($this, $buffer) = @_;
    my ($offset, $data_length);
    my ($flags, $type, $length, $len_format, $len_bytes, $sub, $data);
    my ($error_data, $ii);
    my @decode_sub = (
        undef,
        \&_decode_origin,
        \&_decode_as_path,
        \&_decode_next_hop,
        \&_decode_med,
        \&_decode_local_pref,
        \&_decode_atomic_aggregate,
        \&_decode_aggregator,
        \&_decode_communities
    );

    $offset = 0;
    $data_length = length($buffer);

    while ( $data_length ) {
        $flags   = unpack('C', substr($buffer, $offset++, 1));
        $type    = unpack('C', substr($buffer, $offset++, 1));

        $len_format = 'C';
        $len_bytes  = 1;
        if ( $flags & $BGP_PATH_ATTR_FLAG_EXTLEN ) {
            $len_format = 'n';
            $len_bytes  = 2;
        }

        $length  = unpack($len_format, substr($buffer, $offset, $len_bytes));
        $offset += $len_bytes;

        if ( $length > ($data_length - ($len_bytes + 2)) ) {
            $data = substr($buffer, $offset - $len_bytes - 2, $length + $len_bytes + 2);
            Net::BGP::Notification->throw(
                ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
                ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_LENGTH,
                ErrorData    => $error_data
            );
        }

        ## do we know how to decode this attribute?
        if (defined $decode_sub[$type])
        {
            $error_data = substr($buffer, $offset - $len_bytes - 2, $length + $len_bytes + 2);
            if ( $BGP_PATH_ATTR_FLAGS[$type] != ($flags & ~$BGP_PATH_ATTR_FLAG_EXTLEN) ) {
                Net::BGP::Notification->throw(
                    ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
                    ErrorSubCode => BGP_ERROR_SUBCODE_BAD_ATTR_FLAGS,
                    ErrorData    => $error_data
                );
            }

            $sub = $decode_sub[$type];
            $this->$sub(substr($buffer, $offset, $length));
        }

        $offset += $length;
        $data_length -= ($length + $len_bytes + 2);
    }

    ## Check for missing mandatory well-known attributes
    ##
    for my $attr (@_BGP_MANDATORY_ATTRS)
    {
        $this->{_attr_mask}->[$attr]
            or Net::BGP::Notification->throw(
                ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
                ErrorSubCode => BGP_ERROR_SUBCODE_MISSING_WELL_KNOWN_ATTR,
                ErrorData    => pack('C', $attr)
            );
    }

    ## Check for repeated attributes, which violates RFC 4271, sec 5.
    ##
    if ( grep { defined $_ and $_ > 1 } @{$this->{_attr_mask}||[]} )
    {
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_MALFORMED_ATTR_LIST
        );
    }
}

sub _decode_prefix_list
{
    my ($this, $buffer) = @_;
    my ($offset, $data_length);
    my ($prefix, $prefix_bits, $prefix_bytes, $ii, @prefix_list);

    $offset = 0;
    $data_length = length($buffer);

    while ( $data_length ) {
        $prefix_bits = unpack('C', substr($buffer, $offset++, 1));
        $prefix_bytes = int($prefix_bits / 8) + (($prefix_bits % 8) ? 1 : 0);

        if ( $prefix_bytes > ($data_length - 1)) {
            return ( FALSE );
        }

        $prefix = 0;
        for ( $ii = 0; $ii < $prefix_bytes; $ii++ ) {
            $prefix |= (unpack('C', substr($buffer, $offset++, 1)) << (24 - ($ii * 8)));
        }

        $prefix = pack('N', $prefix);
        push(@prefix_list, inet_ntoa($prefix) . "/" . $prefix_bits);
        $data_length -= ($prefix_bytes + 1);
    }

    return ( TRUE, @prefix_list );
}

sub _decode_withdrawn
{
    my ($this, $buffer) = @_;
    my ($result, @prefix_list);

    ($result, @prefix_list) = $this->_decode_prefix_list($buffer);
    if ( ! $result ) {
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_MALFORMED_ATTR_LIST
        );
    }

    push(@{$this->{_withdrawn}}, @prefix_list);
}

sub _decode_nlri
{
    my ($this, $buffer) = @_;
    my ($result, @prefix_list);

    ($result, @prefix_list) = $this->_decode_prefix_list($buffer);
    if ( ! $result ) {
        Net::BGP::Notification->throw(
            ErrorCode    => BGP_ERROR_CODE_UPDATE_MESSAGE,
            ErrorSubCode => BGP_ERROR_SUBCODE_BAD_NLRI
        );
    }

    push(@{$this->{_nlri}}, @prefix_list);
}

sub _encode_message
{
    my $this = shift();
    my ($buffer, $withdrawn, $path_attr, $nlri);

    # encode the Withdrawn Routes field
    $withdrawn = $this->_encode_prefix_list($this->{_withdrawn});
    $buffer = pack('n', length($withdrawn)) . $withdrawn;

    # encode the Path Attributes field
    $path_attr = $this->_encode_path_attributes();
    $buffer .= (pack('n', length($path_attr)) . $path_attr);

    # encode the Network Layer Reachability Information field
    $buffer .= $this->_encode_prefix_list($this->{_nlri});

    return ( $buffer );
}

sub _encode_prefix
{
    my $prefix = shift();
    my ($buffer, $length, @octets);

    ($prefix, $length) = split('/', $prefix);

    $buffer = pack('C', $length);

    @octets = split(/\./, $prefix);
    while ( $length > 0 ) {
        $buffer .= pack('C', shift(@octets));
        $length -= 8;
    }

    return ( $buffer );
}

sub _encode_prefix_list
{
    my ($this, $prefix_list) = @_;
    my ($prefix, $buffer);

    $buffer = '';
    foreach $prefix ( @{$prefix_list} ) {
        $buffer .= _encode_prefix($prefix);
    }

    return ( $buffer );
}

sub _encode_origin
{
    my $this = shift();

    $this->_encode_attr(BGP_PATH_ATTR_ORIGIN,
                        pack('C', $this->{_origin}));
}

sub _encode_as_path
{
    my $this = shift();
    my $as_buffer = $this->{_as_path}->_encode;
    $this->_encode_attr(BGP_PATH_ATTR_AS_PATH, $as_buffer);
}

sub _encode_next_hop
{
    my $this = shift();
    $this->_encode_attr(BGP_PATH_ATTR_NEXT_HOP,
                        inet_aton($this->{_next_hop}));
}

sub _encode_med
{
    my $this = shift();
    $this->_encode_attr(BGP_PATH_ATTR_MULTI_EXIT_DISC,
                        pack('N', $this->{_med}));
}

sub _encode_local_pref
{
    my $this = shift();
    $this->_encode_attr(BGP_PATH_ATTR_LOCAL_PREF,
                        pack('N', $this->{_local_pref}));
}

sub _encode_atomic_aggregate
{
    my $this = shift();
    $this->_encode_attr(BGP_PATH_ATTR_ATOMIC_AGGREGATE);
}

sub _encode_aggregator
{
    my $this = shift();
    my $aggr = pack('n', $this->{_aggregator}->[0]) .
        inet_aton($this->{_aggregator}->[1]);

    $this->_encode_attr(BGP_PATH_ATTR_AGGREGATOR, $aggr);
}

sub _encode_communities
{
    my $this = shift();
    my ($as, $val, $community, @communities);
    my ($buffer, $community_buffer);

    @communities = @{$this->{_communities}};
    foreach $community ( @communities ) {
        ($as, $val) = split(/\:/, $community);
        $community_buffer .= pack('nn', $as, $val);
    }

    $this->_encode_attr(BGP_PATH_ATTR_COMMUNITIES, $community_buffer);
}

sub _encode_path_attributes
{
    my $this = shift();
    my $buffer;

    $buffer = '';

    # do not encode path attributes if no NLRI is present
    unless ((defined $this->{_nlri})
	 && scalar(@{$this->{_nlri}})) {
        return ( $buffer );
    }

    # encode the ORIGIN path attribute
    if ( ! defined($this->{_origin}) ) {
        carp "mandatory path attribute ORIGIN not defined\n";
    }
    $buffer = $this->_encode_origin();

    # encode the AS_PATH path attribute
    if ( ! defined($this->{_as_path}) ) {
        carp "mandatory path attribute AS_PATH not defined\n";
    }
    $buffer .= $this->_encode_as_path();

    # encode the NEXT_HOP path attribute
    if ( ! defined($this->{_next_hop}) ) {
        carp "mandatory path attribute NEXT_HOP not defined\n";
    }
    $buffer .= $this->_encode_next_hop();

    # encode the MULTI_EXIT_DISC path attribute
    if ( defined($this->{_med}) ) {
        $buffer .= $this->_encode_med();
    }

    # encode the LOCAL_PREF path attribute
    if ( defined($this->{_local_pref}) ) {
        $buffer .= $this->_encode_local_pref();
    }

    # encode the ATOMIC_AGGREGATE path attribute
    if ( defined($this->{_atomic_agg}) ) {
        $buffer .= $this->_encode_atomic_aggregate();
    }

    # encode the AGGREGATOR path attribute
    if ( scalar(@{$this->{_aggregator}}) ) {
        $buffer .= $this->_encode_aggregator();
    }

    # encode the COMMUNITIES path attribute
    if ( scalar(@{$this->{_communities}}) ) {
        $buffer .= $this->_encode_communities();
    }

    return ( $buffer );
}

## POD ##


## End Package Net::BGP::Update ##

1;