forked from Imagelibrary/rtems
ec95bd8438
* networking/networkflow.txt, networking/PCIreg.txt, networking/recvbd.txt: New. * networking/decdriver.t, networking/networktasks.t: Use @image for ASCII figures (Reflect changes above).
48 lines
1.6 KiB
Perl
48 lines
1.6 KiB
Perl
@c
|
|
@c Written by Eric Norum
|
|
@c
|
|
@c COPYRIGHT (c) 1988-2002.
|
|
@c On-Line Applications Research Corporation (OAR).
|
|
@c All rights reserved.
|
|
@c
|
|
@c $Id$
|
|
@c
|
|
|
|
@chapter Network Task Structure and Data Flow
|
|
|
|
A schematic diagram of the tasks and message @b{mbuf} queues in a
|
|
simple RTEMS networking application is shown in the following
|
|
figure:
|
|
|
|
@ifclear use-html
|
|
@image{networkflow,5in,6in,"Network Task Structure and Data Flow"}
|
|
@end ifclear
|
|
|
|
@ifset use-html
|
|
@html
|
|
<IMG SRC="networkflow.jpg" ALIGN=CENTER
|
|
ALT="Network Task Structure and Data Flow">
|
|
@end html
|
|
@end ifset
|
|
|
|
|
|
The transmit task for each network interface is normally blocked waiting
|
|
for a packet to arrive in the transmit queue. Once a packet arrives, the
|
|
transmit task may block waiting for an event from the transmit interrupt
|
|
handler. The transmit interrupt handler sends an RTEMS event to the transmit
|
|
task to indicate that transmit hardware resources have become available.
|
|
|
|
The receive task for each network interface is normally blocked waiting
|
|
for an event from the receive interrupt handler. When this event is received
|
|
the receive task reads the packet and forwards it to the network stack
|
|
for subsequent processing by the network task.
|
|
|
|
The network task processes incoming packets and takes care of
|
|
timed operations such as handling TCP timeouts and
|
|
aging and removing routing table entries.
|
|
|
|
The `Network code' contains routines which may run in the context of
|
|
the user application tasks, the interface receive task or the network task.
|
|
A network semaphore ensures that
|
|
the data structures manipulated by the network code remain consistent.
|