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version 1.1, 2003/04/18 02:39:20	version 1.3, 2003/04/18 03:10:36
Line 1	Line 1
#!/usr/bin/perl	#!/usr/bin/perl
	# The LearningOnline Network with CAPA
	# lonc maintains the connections to remote computers
	#
	# $Id$
	#
	# Copyright Michigan State University Board of Trustees
	#
	# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
	#
	# LON-CAPA is free software; you can redistribute it and/or modify
	# it under the terms of the GNU General Public License as published by
	# the Free Software Foundation; either version 2 of the License, or
	# (at your option) any later version.
	#
	# LON-CAPA is distributed in the hope that it will be useful,
	# but WITHOUT ANY WARRANTY; without even the implied warranty of
	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	# GNU General Public License for more details.
	#
	# You should have received a copy of the GNU General Public License
	# along with LON-CAPA; if not, write to the Free Software
	# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	#
	# /home/httpd/html/adm/gpl.txt
	#
	# http://www.lon-capa.org/
	#
#	#
# new lonc handles n requestors spread out bver m connections to londs.	# new lonc handles n requestors spread out bver m connections to londs.
# This module is based on the Event class.	# This module is based on the Event class.
Line 76 my $ConnectionCount = 0;	Line 103 my $ConnectionCount = 0;


#	#

=pod	=pod
=head 2 GetPeerName
Returns the name of the host that a socket object is connected	=head2 GetPeerName
to.
	Returns the name of the host that a socket object is connected to.

=cut	=cut

sub GetPeername {	sub GetPeername {
Line 100 sub GetPeername {	Line 130 sub GetPeername {
}	}
#----------------------------- Timer management ------------------------	#----------------------------- Timer management ------------------------
=pod	=pod

=head2 Debug	=head2 Debug
Invoked to issue a debug message.
	Invoked to issue a debug message.

=cut	=cut

sub Debug {	sub Debug {
my $level = shift;	my $level = shift;
my $message = shift;	my $message = shift;
Line 118 sub SocketDump {	Line 152 sub SocketDump {
$socket->Dump();	$socket->Dump();
}	}
}	}

=pod	=pod

=head2 Tick	=head2 Tick
Invoked each timer tick.
	Invoked each timer tick.

=cut	=cut

sub Tick {	sub Tick {
Line 133 sub Tick {	Line 171 sub Tick {
}	}

=pod	=pod

=head2 SetupTimer	=head2 SetupTimer
Sets up a 1 per sec recurring timer event. The event handler is used to:

=item Trigger timeouts on communications along active sockets.	Sets up a 1 per sec recurring timer event. The event handler is used to:
=item Trigger disconnections of idle sockets.
	=item

	Trigger timeouts on communications along active sockets.

	=item

	Trigger disconnections of idle sockets.

=cut	=cut

Line 146 sub SetupTimer {	Line 190 sub SetupTimer {
Debug(6, "SetupTimer");	Debug(6, "SetupTimer");
Event->timer(interval => 1, debug => 1, cb => \&Tick );	Event->timer(interval => 1, debug => 1, cb => \&Tick );
}	}

=pod	=pod

=head2 ServerToIdle	=head2 ServerToIdle
This function is called when a connection to the server is
ready for more work.	This function is called when a connection to the server is
If there is work in the Work queue the top element is dequeued	ready for more work.

	If there is work in the Work queue the top element is dequeued
and the connection will start to work on it. If the work queue is	and the connection will start to work on it. If the work queue is
empty, the connection is pushed on the idle connection stack where	empty, the connection is pushed on the idle connection stack where
it will either get another work unit, or alternatively, if it sits there	it will either get another work unit, or alternatively, if it sits there
long enough, it will be shut down and released.	long enough, it will be shut down and released.


=cut	=cut

sub ServerToIdle {	sub ServerToIdle {
my $Socket = shift; # Get the socket.	my $Socket = shift; # Get the socket.

Line 181 sub ServerToIdle {	Line 229 sub ServerToIdle {
$IdleConnections->push($Socket);	$IdleConnections->push($Socket);
}	}
}	}

=pod	=pod

=head2 ClientWritable	=head2 ClientWritable
Event callback for when a client socket is writable.
This callback is established when a transaction reponse is	Event callback for when a client socket is writable.
avaiable from lond. The response is forwarded to the unix socket
as it becomes writable in this sub.	This callback is established when a transaction reponse is
	avaiable from lond. The response is forwarded to the unix socket
	as it becomes writable in this sub.

Parameters:	Parameters:

=item Event - The event that has been triggered. Event->w->data is	=item Event
the data and Event->w->fd is the socket to write.
	The event that has been triggered. Event->w->data is
	the data and Event->w->fd is the socket to write.

=cut	=cut

sub ClientWritable {	sub ClientWritable {
my $Event = shift;	my $Event = shift;
my $Watcher = $Event->w;	my $Watcher = $Event->w;
Line 253 sub ClientWritable {	Line 309 sub ClientWritable {
}	}

=pod	=pod

=head2 CompleteTransaction	=head2 CompleteTransaction
Called when the reply data has been received for a lond
	Called when the reply data has been received for a lond
transaction. The reply data must now be sent to the	transaction. The reply data must now be sent to the
ultimate client on the other end of the Unix socket. This is	ultimate client on the other end of the Unix socket. This is
done by setting up a writable event for the socket with the	done by setting up a writable event for the socket with the
data the reply data.	data the reply data.

Parameters:	Parameters:
=item Socket - Socket on which the lond transaction occured. This
is a LondConnection. The data received is in the	=item Socket
TransactionReply member.
=item Client - Unix domain socket open on the ultimate client.	Socket on which the lond transaction occured. This is a
	LondConnection. The data received is in the TransactionReply member.

	=item Client

	Unix domain socket open on the ultimate client.

=cut	=cut

sub CompleteTransaction {	sub CompleteTransaction {
&Debug(6,"Complete transaction");	&Debug(6,"Complete transaction");
my $Socket = shift;	my $Socket = shift;
Line 286 sub CompleteTransaction {	Line 351 sub CompleteTransaction {


=pod	=pod

=head2 LondReadable	=head2 LondReadable

This function is called whenever a lond connection	This function is called whenever a lond connection
is readable. The action is state dependent:	is readable. The action is state dependent:

=head3 State = Initialized	=head3 State=Initialized
We''re waiting for the challenge, this is a no-op until the
	We''re waiting for the challenge, this is a no-op until the
state changes.	state changes.

=head3 State=Challenged	=head3 State=Challenged
The challenge has arrived we need to transition to Writable.
	The challenge has arrived we need to transition to Writable.
The connection must echo the challenge back.	The connection must echo the challenge back.

=head3 State=ChallengeReplied	=head3 State=ChallengeReplied
The challenge has been replied to. The we are receiveing the
	The challenge has been replied to. The we are receiveing the
'ok' from the partner.	'ok' from the partner.

=head3 State=RequestingKey	=head3 State=RequestingKey
The ok has been received and we need to send the request for
	The ok has been received and we need to send the request for
an encryption key. Transition to writable for that.	an encryption key. Transition to writable for that.

=head3 State=ReceivingKey	=head3 State=ReceivingKey
The the key has been requested, now we are reading the new key.
	The the key has been requested, now we are reading the new key.

=head3 State=Idle	=head3 State=Idle
The encryption key has been negotiated or we have finished
	The encryption key has been negotiated or we have finished
reading data from the a transaction. If the callback data has	reading data from the a transaction. If the callback data has
a client as well as the socket iformation, then we are	a client as well as the socket iformation, then we are
doing a transaction and the data received is relayed to the client	doing a transaction and the data received is relayed to the client
before the socket is put on the idle list.	before the socket is put on the idle list.

=head3 State=SendingRequest	=head3 State=SendingRequest
I do not think this state can be received here, but if it is,
	I do not think this state can be received here, but if it is,
the appropriate thing to do is to transition to writable, and send	the appropriate thing to do is to transition to writable, and send
the request.	the request.

=head3 State=ReceivingReply	=head3 State=ReceivingReply
We finished sending the request to the server and now transition
	We finished sending the request to the server and now transition
to readable to receive the reply.	to readable to receive the reply.

The parameter to this function are:	The parameter to this function are:

The event. Implicit in this is the watcher and its data. The data	The event. Implicit in this is the watcher and its data. The data
contains at least the lond connection object and, if a	contains at least the lond connection object and, if a
transaction is in progress, the socket attached to the local client.	transaction is in progress, the socket attached to the local client.


=cut	=cut

sub LondReadable {	sub LondReadable {
my $Event = shift;	my $Event = shift;
my $Watcher = $Event->w;	my $Watcher = $Event->w;
Line 395 sub LondReadable {	Line 478 sub LondReadable {
Debug(4, "Invalid state in LondReadable");	Debug(4, "Invalid state in LondReadable");
}	}
}	}

=pod	=pod

=head2 LondWritable	=head2 LondWritable

This function is called whenever a lond connection	This function is called whenever a lond connection
becomes writable while there is a writeable monitoring	becomes writable while there is a writeable monitoring
event. The action taken is very state dependent:	event. The action taken is very state dependent:

=head3 State = Connected	=head3 State = Connected
The connection is in the process of sending the
'init' hailing to the lond on the remote end.	The connection is in the process of sending the 'init' hailing to the
The connection object''s Writable member is called.	lond on the remote end. The connection object''s Writable member is
On error, ConnectionError is called to destroy	called. On error, ConnectionError is called to destroy the connection
the connection and remove it from the ActiveConnections	and remove it from the ActiveConnections hash
hash
=head3 Initialized	=head3 Initialized
'init' has been sent, writability monitoring is
removed and readability monitoring is started	'init' has been sent, writability monitoring is removed and
with LondReadable as the callback.	readability monitoring is started with LondReadable as the callback.

=head3 ChallengeReceived	=head3 ChallengeReceived
The connection has received the who are you
challenge from the remote system, and is in the	The connection has received the who are you challenge from the remote
process of sending the challenge response.	system, and is in the process of sending the challenge
Writable is called.	response. Writable is called.

=head3 ChallengeReplied	=head3 ChallengeReplied
The connection has replied to the initial challenge
The we switch to monitoring readability looking	The connection has replied to the initial challenge The we switch to
for the server to reply with 'ok'.	monitoring readability looking for the server to reply with 'ok'.

=head3 RequestingKey	=head3 RequestingKey
The connection is in the process of requesting its
encryption key. Writable is called.	The connection is in the process of requesting its encryption key.
	Writable is called.

=head3 ReceivingKey	=head3 ReceivingKey
The connection has sent the request for a key.
Switch to readability monitoring to accept the key	The connection has sent the request for a key. Switch to readability
	monitoring to accept the key

=head3 SendingRequest	=head3 SendingRequest
The connection is in the process of sending a
request to the server. This request is part of	The connection is in the process of sending a request to the server.
a client transaction. All the states until now	This request is part of a client transaction. All the states until
represent the client setup protocol. Writable	now represent the client setup protocol. Writable is called.
is called.
=head3 ReceivingReply	=head3 ReceivingReply
The connection has sent a request. Now it must
receive a reply. Readability monitoring is
requested.

This function is an event handler and therefore receives as	The connection has sent a request. Now it must receive a reply.
	Readability monitoring is requested.

	This function is an event handler and therefore receives as
a parameter the event that has fired. The data for the watcher	a parameter the event that has fired. The data for the watcher
of this event is a reference to a list of one or two elements,	of this event is a reference to a list of one or two elements,
depending on state. The first (and possibly only) element is the	depending on state. The first (and possibly only) element is the
Line 445 socket. The second (present only if a r	Line 539 socket. The second (present only if a r
is the socket on which to return a reply to the caller.	is the socket on which to return a reply to the caller.

=cut	=cut

sub LondWritable {	sub LondWritable {
my $Event = shift;	my $Event = shift;
my $Watcher = $Event->w;	my $Watcher = $Event->w;
Line 537 sub LondWritable {	Line 632 sub LondWritable {
}	}

=pod	=pod

=head2 MakeLondConnection	=head2 MakeLondConnection
Create a new lond connection object, and start it towards
its initial idleness. Once idle, it becomes elligible to	Create a new lond connection object, and start it towards its initial
receive transactions from the work queue. If the work queue	idleness. Once idle, it becomes elligible to receive transactions
is not empty when the connection is completed and becomes idle,	from the work queue. If the work queue is not empty when the
it will dequeue an entry and start off on it.	connection is completed and becomes idle, it will dequeue an entry and
	start off on it.

=cut	=cut

sub MakeLondConnection {	sub MakeLondConnection {
Debug(4,"MakeLondConnection to ".GetServerHost()." on port "	Debug(4,"MakeLondConnection to ".GetServerHost()." on port "
.GetServerPort());	.GetServerPort());
Line 579 sub MakeLondConnection {	Line 678 sub MakeLondConnection {


}	}

=pod	=pod

=head2 StartRequest	=head2 StartRequest
Starts a lond request going on a specified lond connection.
parameters are:	Starts a lond request going on a specified lond connection.
=item $Lond - Connection to the lond that will send the transaction	parameters are:
and receive the reply.
=item $Client - Connection to the client that is making this request	=item $Lond
We got the request from this socket, and when the request has
been relayed to lond and we get a reply back from lond it will	Connection to the lond that will send the transaction and receive the
get sent to this socket.	reply.
=item $Request - The text of the request to send.
	=item $Client

	Connection to the client that is making this request We got the
	request from this socket, and when the request has been relayed to
	lond and we get a reply back from lond it will get sent to this
	socket.

	=item $Request

	The text of the request to send.

=cut	=cut

sub StartRequest {	sub StartRequest {
Line 614 sub StartRequest {	Line 726 sub StartRequest {
}	}

=pod	=pod

=head2 QueueTransaction	=head2 QueueTransaction
- If there is an idle lond connection, it is put to
work doing this transaction. Otherwise, the transaction is	If there is an idle lond connection, it is put to work doing this
placed in the work queue. If placed in the work queue and the	transaction. Otherwise, the transaction is placed in the work queue.
maximum number of connections has not yet been created, a new	If placed in the work queue and the maximum number of connections has
connection will be started. Our goal is to eventually have	not yet been created, a new connection will be started. Our goal is
a sufficient number of connections that the work queue will	to eventually have a sufficient number of connections that the work
typically be empty.	queue will typically be empty. parameters are:
parameters are:
=item Socket open on the lonc client.	=item Socket
=item Request data to send to the lond.
	open on the lonc client.

	=item Request

	data to send to the lond.

=cut	=cut

sub QueueTransaction {	sub QueueTransaction {
my $requestSocket = shift;	my $requestSocket = shift;
my $requestData = shift;	my $requestData = shift;
Line 649 sub QueueTransaction {	Line 768 sub QueueTransaction {
}	}

#-------------------------- Lonc UNIX socket handling ---------------------	#-------------------------- Lonc UNIX socket handling ---------------------

=pod	=pod

=head2 ClientRequest	=head2 ClientRequest
Callback that is called when data can be read from the
UNIX domain socket connecting us with an apache server process.	Callback that is called when data can be read from the UNIX domain
	socket connecting us with an apache server process.

=cut	=cut

Line 689 sub ClientRequest {	Line 811 sub ClientRequest {


=pod	=pod

=head2 NewClient	=head2 NewClient
Callback that is called when a connection is received on the
unix socket for a new client of lonc. The callback is parameterized	Callback that is called when a connection is received on the unix
by the event.. which is a-priori assumed to be an io event, and therefore	socket for a new client of lonc. The callback is parameterized by the
has an fd member that is the Listener socket. We Accept the connection	event.. which is a-priori assumed to be an io event, and therefore has
and register a new event on the readability of that socket:	an fd member that is the Listener socket. We Accept the connection
	and register a new event on the readability of that socket:

=cut	=cut

sub NewClient {	sub NewClient {
Debug(6, "NewClient");	Debug(6, "NewClient");
my $event = shift; # Get the event parameters.	my $event = shift; # Get the event parameters.
Line 717 sub NewClient {	Line 843 sub NewClient {
$ActiveClients{$connection} = $ClientConnection;	$ActiveClients{$connection} = $ClientConnection;
$ClientConnection++;	$ClientConnection++;
}	}
=pod GetLoncSocketPath
Returns the name of the UNIX socket on which to listen for client	=pod
connections.
	=head2 GetLoncSocketPath

	Returns the name of the UNIX socket on which to listen for client
	connections.

=cut	=cut

sub GetLoncSocketPath {	sub GetLoncSocketPath {
return $UnixSocketDir."/".GetServerHost();	return $UnixSocketDir."/".GetServerHost();
}	}

=pod GetServerHost	=pod
Returns the host whose lond we talk with.
	=head2 GetServerHost

	Returns the host whose lond we talk with.

=cut	=cut

sub GetServerHost { # Stub - get this from config.	sub GetServerHost { # Stub - get this from config.
return $RemoteHost; # Setup by the fork.	return $RemoteHost; # Setup by the fork.
}	}
=pod GetServerPort
Returns the lond port number.	=pod

	=head2 GetServerPort

	Returns the lond port number.

=cut	=cut

sub GetServerPort { # Stub - get this from config.	sub GetServerPort { # Stub - get this from config.
return $perlvar{londPort};	return $perlvar{londPort};
}	}
=pod SetupLoncListener
Setup a lonc listener event. The event is called when	=pod
the socket becomes readable.. that corresponds to the
receipt of a new connection. The event handler established	=head2 SetupLoncListener
will accept the connection (creating a communcations channel), that
int turn will establish another event handler to subess requests.	Setup a lonc listener event. The event is called when the socket
	becomes readable.. that corresponds to the receipt of a new
	connection. The event handler established will accept the connection
	(creating a communcations channel), that int turn will establish
	another event handler to subess requests.

=cut	=cut

sub SetupLoncListener {	sub SetupLoncListener {

my $socket;	my $socket;
Line 763 sub SetupLoncListener {	Line 910 sub SetupLoncListener {
}	}

=pod	=pod

=head2 ChildProcess	=head2 ChildProcess

This sub implements a child process for a single lonc daemon.	This sub implements a child process for a single lonc daemon.
Line 848 while(1) {	Line 996 while(1) {
}	}

=head1 Theory	=head1 Theory
The event class is used to build this as a single process with
an event driven model. The following events are handled:	The event class is used to build this as a single process with an
	event driven model. The following events are handled:

=item UNIX Socket connection Received	=item UNIX Socket connection Received

Line 863 All sockets are run in non-blocking mode	Line 1012 All sockets are run in non-blocking mode
handler prevents hung connections.	handler prevents hung connections.

Key data structures:	Key data structures:
=item RequestQueue - A queue of requests received from UNIX sockets that are
waiting for a chance to be forwarded on a lond connection socket.

=item ActiveConnections - A hash of lond connections that have transactions	=item RequestQueue
in process that are available to be timed out.
	A queue of requests received from UNIX sockets that are
	waiting for a chance to be forwarded on a lond connection socket.

	=item ActiveConnections

	A hash of lond connections that have transactions in process that are
	available to be timed out.

	=item ActiveTransactions

	A hash indexed by lond connections that contain the client reply
	socket for each connection that has an active transaction on it.

	=item IdleConnections

	A hash of lond connections that have no work to do. These connections
	can be closed if they are idle for a long enough time.

=item ActiveTransactions - A hash indexed by lond connections that
contain the client reply socket for each connection that has an active
transaction on it.

=item IdleConnections - A hash of lond connections that have no work
to do. These connections can be closed if they are idle for a long
enough time.
=cut	=cut

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	Added in v.1.3