kevin brintnall > Net-BGP-0.14 > Net::BGP::Peer

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Module Version: 0.08   Source  

NAME ^

Net::BGP::Peer - Class encapsulating BGP-4 peering session state and functionality

SYNOPSIS ^

    use Net::BGP::Peer;

    $peer = Net::BGP::Peer->new(
        Start                => 1,
        ThisID               => '10.0.0.1',
        ThisAS               => 64512,
        PeerID               => '10.0.0.2',
        PeerAS               => 64513,
        PeerPort             => 1179,
        ConnectRetryTime     => 300,
        HoldTime             => 60,
        KeepAliveTime        => 20,
        Listen               => 0,
        Passive              => 0,
        OpenCallback         => \&my_open_callback,
        KeepaliveCallback    => \&my_keepalive_callback,
        UpdateCallback       => \&my_update_callback,
        NotificationCallback => \&my_notification_callback,
        ErrorCallback        => \&my_error_callback
    );

    $peer = renew Net::BGP::Peer("$peer");

    $peer->start();
    $peer->stop();

    $peer->update($update);
    $peer->refresh($refresh);

    $version = $peer->version();

    $this_id = $peer->this_id();
    $this_as = $peer->this_as();
    $peer_id = $peer->peer_id();
    $peer_as = $peer->peer_as();

    $i_can   = $peer->this_can_refresh();
    $peer_can= $peer->peer_can_refresh();

    $listen  = $peer->is_listener();
    $passive = $peer->is_passive();
    $estab   = $peer->is_established();

    $trans   = $peer->transport($trans);
    @trans   = $peer->transports;

    $string  = $peer->asstring();

    $peer->set_open_callback(\&my_open_callback);
    $peer->set_keepalive_callback(\&my_keepalive_callback);
    $peer->set_update_callback(\&my_update_callback);
    $peer->set_notification_callback(\&my_notification_callback);
    $peer->set_error_callback(\&my_error_callback);

    $peer->add_timer(\&my_minute_timer, 60);
    $peer->remove_timer(\&my_minute_timer);

DESCRIPTION ^

This module encapsulates the state and functionality associated with a BGP peering session. Each instance of a Net::BGP::Peer object corresponds to a peering session with a distinct peer and presents a programming interface to manipulate the peering session state and exchange of routing information. Through the methods provided by the Net::BGP::Peer module, a program can start or stop peering sessions, send BGP routing UPDATE messages, and register callback functions which are invoked whenever the peer receives BGP messages from its peer.

CONSTRUCTOR ^

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

This is the constructor for Net::BGP::Peer objects. It returns a reference to the newly created object. The following named parameters may be passed to the constructor. Once the object is created, only the callback function references can later be changed.

Start

Setting this parameter to a true value causes the peer to initiate a session with its peer immediately after it is registered with the Net::BGP::Process object's add_peer() method. If omitted or set to a false value, the peer will remain in the Idle state until the start() method is called explicitly by the program. When in the Idle state the peer will refuse connections and will not initiate connection attempts.

ThisID

This parameter sets the BGP ID (IP address) of the Net::BGP::Peer object. It takes a string in IP dotted decimal notation.

ThisAS

This parameter sets the BGP Autonomous System number of the Net::BGP::Peer object. It takes an integer value in the range of a 16-bit unsigned integer.

PeerID

This parameter sets the BGP ID (IP address) of the object's peer. It takes a string in IP dotted decimal notation.

PeerAS

This parameter sets the BGP Autonomous System number of the object's peer. It takes an integer value in the range of a 16-bit unsigned integer.

PeerPort

This parameter sets the TCP port number on the peer to which to connect. It must be in the range of a valid TCP port number.

ConnectRetryTime

This parameter sets the BGP ConnectRetry timer duration, the value of which is given in seconds.

HoldTime

This parameter sets the BGP Hold Time duration, the value of which is given in seconds.

KeepAliveTime

This parameter sets the BGP KeepAlive timer duration, the value of which is given in seconds.

Listen

This parameter specifies whether the Net::BGP::Peer will listen for and accept connections from its peer. If set to a false value, the peer will only initiate connections and will not accept connection attempts from the peer (unless the Passive parameter is set to a true value). Note that this behavior is not specified by RFC 1771 and should be considered non-standard. However, it is useful under certain circumstances and should not present problems as long as one side of the connection is configured to listen.

Passive

This parameter specifies whether the Net::BGP::Peer will attempt to initiate connections to its peer. If set to a true value, the peer will only listen for connections and will not initate connections to its peer (unless the Listen parameter is set to false value). Note that this behavior is not specified by RFC 1771 and should be considered non-standard. However, it is useful under certain circumstances and should not present problems as long as one side of the connection is configured to initiate connections.

Refresh

This parameter specifies whether the Net::BGP::Peer will annonce support for route refresh ('soft re-configure' as specified by RFC 2918). No support for route refresh is implemented - only the RefreshCallback function.

OpenCallback

This parameter sets the callback function which is invoked when the peer receives an OPEN message. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

KeepaliveCallback

This parameter sets the callback function which is invoked when the peer receives a KEEPALIVE message. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

UpdateCallback

This parameter sets the callback function which is invoked when the peer receives an UPDATE message. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

RefreshCallback

This parameter sets the callback function which is invoked when the peer receives a REFRESH message. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

NotificationCallback

This parameter sets the callback function which is invoked when the peer receives a NOTIFICATION message. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

ErrorCallback

This parameter sets the callback function which is invoked when the peer encounters an error and must send a NOTIFICATION message to its peer. It takes a subroutine reference. See "CALLBACK FUNCTIONS" later in this manual for further details of the conventions of callback invocation.

renew - fetch the existing Net::BGP::Peer object from the "object string".

This "reconstructor" returns a previeus constructed object from the perl genereted string-context scalar of the object, eg. Net::BGP::Peer=HASH(0x820952c).

ACCESSOR METHODS ^

start() - start the BGP peering session with the peer

    $peer->start();

This method initiates the BGP peering session with the peer by internally emitting the BGP Start event, which causes the peer to initiate a transport-layer connection to its peer (unless the Passive parameter was set to a true value in the constructor) and listen for a connection from the peer (unless the Listen parameter is set to a false value).

stop() - cease the BGP peering session with the peer

    $peer->stop();

This method immediately ceases the peering session with the peer by sending it a NOTIFICATION message with Error Code Cease, closing the transport-layer connection, and entering the Idle state.

update() - send a BGP UPDATE message to the peer

    $peer->update($update);

This method sends the peer an UPDATE message. It takes a reference to a Net::BGP::Update object. See the Net::BGP::Update manual page for details on setting UPDATE attributes.

refresh() - send a BGP REFRESH message to the peer

    $peer->refresh($refresh);

This method sends the peer a REFRESH message. It takes a reference to a Net::BGP::Refesh object. If no argument is provided, a default Net::BGP::Refresh object is constructed. See the Net::BGP::Refresh manual page for details on setting REFRESH attributes.

transport()

Returns the active transport object to the peer - See Net::BGP::Transport.

transports()

Return a list of transport objects. The list will contain one or two elements. The first will always be the primary transport object. If there are two sessions (e.g. collision detection hasn't removed one of them), the sibling will be returned as the second element of the list.

this_id()

this_as()

peer_id()

peer_as()

this_can_refresh()

is_listener()

is_passive()

version()

These are accessor methods for the corresponding constructor named parameters. They retrieve the values set when the object was created, but the values cannot be changed after object construction. Hence, they take no arguments.

is_established()

This accessor method returns true if the peer has a established transport connection - e.g. the peering is up.

peer_can_refresh()

This accessor method returns a true value if connected to a peer that supports refresh messages - otherwise a false value.

asstring()

This accessor method returns a print friendly string with the local and remote IP and AS numbers.

set_open_callback()

set_keepalive_callback()

set_update_callback()

set_refresh_callback()

set_reset_callback()

set_notification_callback()

set_error_callback()

These methods set the callback functions which are invoked whenever the peer receives the corresponding BGP message type from its peer. They can be set in the constructor as well as with these methods. These methods each take one argument, which is the subroutine reference to be invoked. A callback function can be removed by calling the corresponding one of these methods and passing it the perl undef value. For callback definition and invocation conventions see "CALLBACK FUNCTIONS" later in this manual.

add_timer() - add a program defined timer callback function

    $peer->add_timer(\&my_minute_timer, 60);

This method sets a program defined timer which invokes the specified callback function when the timer expires. It takes two arguments: the first is a code reference to the subroutine to be invoked when the timer expires, and the second is the timer interval, in seconds. The program may set as many timers as needed, and multiple timer callbacks may share the same interval. Program timers add an asynchronous means for user code to gain control of the program control flow - without them user code would only be invoked whenever BGP events exposed by the module occur. They may be used to perform any necessary action - for example, sending UPDATEs, starting or stopping the peering session, house-keeping, etc.

remove_timer() - remove a program defined timer callback function

    $peer->remove_timer(\&my_minute_timer);

This method removes a program defined timer callback which has been previously set with the add_timer() method. It takes a single argument: a reference to the subroutine previously added.

CALLBACK FUNCTIONS ^

Whenever a Net::BGP::Peer object receives one of the BGP protocol messages - OPEN, KEEPALIVE, UPDATE, REFRESH, or NOTIFICATION - from its peer, or whenever it encounters an error condition and must send a NOTIFICATION message to its peer, the peer object will invoke a program defined callback function corresponding to the event type, if one has been provided, to inform the application about the event. These callback functions are installed as described in the preceding section of the manual. Whenever any callback function is invoked, it is passed one or more arguments, depending on the BGP message type associated with the callback. The first argument passed to all of the callbacks is a reference to the Net::BGP::Peer object which the application may use to identify which peer has signalled the event and to take appropriate action. For OPEN and KEEPALIVE callbacks, this is the only argument passed. It is very unlikely that applications will be interested in OPEN and KEEPALIVE events, since the Net::BGP module handles all details of OPEN and KEEPALIVE message processing in order to establish and maintain BGP sessions. Callback handling for these messages is mainly included for the sake of completeness. For UPDATE and NOTIFICATION messages, however, most applications will install callback handlers. Whenever an UPDATE, REFRESH, NOTIFICATION, or error handler is called, the object will pass a second argument. In the first two cases, this is a Net::BGP::Update or Net::BGP::Refresh object respectivly encapsulating the information contained in the UPDATE or REFRESH message, while in the latter two cases it is a Net::BGP::Notification object encapsulating the information in the NOTIFICATION message sent or received.

The RESET callback is special, since it is used whenever an established BGP session is reset, even though no message has been recieved or sent. The REFRESH callback is also special, since it is also called without a REFRESH object whenever a BGP session is established. The two callbacks can be used to clear and retransmit a RIB from/to the peer in question.

Whenever a callback function is to be invoked, the action occuring internally is the invocation of one of the following methods, corresponding to the event which has occured:

open_callback()

keepalive_callback()

update_callback()

refresh_callback()

reset_callback()

notification_callback()

error_callback()

Internally, each of these methods just checks to see whether a program defined callback function has been set and calls it if so, passing it arguments as described above. As an alternative to providing subroutine references to the constructor or through the set_open_callback(), set_keepalive_callback(), set_update_callback(), set_refresh_callback(), set_reset_callback(), set_notification_callback(), and set_error_callback() methods, an application may effect a similar result by sub-classing the Net::BGP::Peer module and overridding the defintions of the above methods to perform whatever actions would have been executed by ordinary callback functions. The overridden methods are passed the same arguments as the callback functions. This method might offer an advantage in organizing code according to different derived classes which apply specifc routing policies.

ERROR HANDLING ^

There are two possibilities for error handling callbacks to be invoked. The first case occurs when the peer receives a NOTIFICATION messages from its peer. The second case occurs when the peer detects an error condition while processing an incoming BGP message or when some other protocol covenant is violated - for example if a KEEPALIVE or UPDATE message is not received before the peer's Keepalive timer expires. In this case, the peer responds by sending a NOTIFICATION message to its peer. In the former case the notification_callback() method is invoked as described above to handle the error, while in the latter the error_callback() method is invoked to inform the application that it has encountered an error. Both methods are passed a Net::BGP::Notification object encapsulating the details of the error. In both cases, the transport-layer connection and BGP session are closed and the peer transitions to the Idle state. The error handler callbacks can examine the cause of the error and take appropriate action. This could be to attempt to re-establish the session (perhaps after sleeping for some amount of time), or to unregister the peer object from the Net::BGP::Process object and permanently end the session (for the duration of the application's running time), or to log the event to a file on the host system, or some combination of these or none.

SEE ALSO ^

Net::BGP, Net::BGP::Process, Net::BGP::Update, Net::BGP::Transport, Net::BGP::Refresh, Net::BGP::Notification

AUTHOR ^

Stephen J. Scheck <code@neurosphere.com>

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