Copyright (C) 2000, 2001, 2004, 2016 Internet Systems Consortium, Inc. ("ISC")

This Source Code Form is subject to the terms of the Mozilla Public

License, v. 2.0. If a copy of the MPL was not distributed with this

file, You can obtain one at http://mozilla.org/MPL/2.0/.

$Id: dispatch,v 1.6 2004/03/05 05:04:46 marka Exp $

UDP receive:

/*

* General flow:

*

* If I/O result == CANCELED, free the buffer and notify everyone as

* the various queues drain.

*

* If I/O is error (not canceled and not success) log it, free the buffer,

* and restart.

*

* If query:

* if no listeners: free the buffer, restart.

* if listener: allocate event, fill in details.

* If cannot allocate, free buffer, restart.

* if rq event queue is not empty, queue. else, send.

* restart.

*

* If response:

* Allocate event, fill in details.

* If cannot allocate, free buffer, restart.

* find target. If not found, free buffer, restart.

* if event queue is not empty, queue. else, send.

* restart.

*/

UDP restart:

/*

* If too many recv()'s are already running, just return.

*

* If noone is attached to us, just return.

*

* Allocate a new buffer to receive into.

* If no more buffers:

* If there are buffers handed out: wait for one to come back.

* If there are no buffers handed out:

* If there are responses attached to us, just return.

* If there are queries only, send one an error event.

*

*

* start recv() on socket. If this fails:

* Free buffer.

* Set dispatch state to "shutting down" and why to "socket error"

* Start failsafe shutdown.

*/

Adding a response:

/*

* If shutting down, return error.

*

* Allocate an unique messageid and return it. If none can be allocated,

* return that.

*

* Allocate a new structure and fill it in. If no memory, return that.

*

* Insert into the correct linked list.

*

* If the receiver is not running, try to start it.

*/

Adding a request:

/*

* If shutting down, return error.

*

* Allocate new structure and fill it in. If no memory, return that.

*

* Insert it into the linked list.

*

* If the incoming query packet queue is not empty, pull an item off and

* send that event to this task.

*

* If the receiver is not running, try to start it.

*/

Detaching a response:

/*

* decrement dispatch reference count by one. If zero, remember to kill it

* later.

*

* unlink the response from the hashed list.

*

* Free any buffers and events attached to the response structure.

*

* Free the response structure.

*

* If an event is also being returned, jump to "internal event free" below.

*

* If the ref count became zero above, destroy this dispatch fully, and return.

*

* If the receiver is not running, try to start it.

*/

Detaching a request:

/*

* decrement dispatch ref count by one. If zero, remember to kill it later.

*

* unlink from the request list.

*

* Free the response structure.

*

* If an event is also being returned, jump to "internal event free" below.

*

* If the ref count became zero above, destroy the dispatch fully, and return.

*

* If the receiver is not running, try to start it.

*/

Internal event free (from library space):

/*

* If it is the failsafe event, send it to the next response/request on the

* dispatcher, and return.

*

* Free buffer.

*

* Free event.

*/

Returning an event (from application space):

/*

* If it is the failsafe event, die.

*

* Free associated buffer.

*

* Free event.

*

* If response: do next response on this response's queue, if any.

* If request: do next request on this dispatcher's queue, if any.

*

* If the receiver is not running, try to start it.

*/