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* SUPPORT, LICENSE: New files. * Numerous files touched as part of merging the 4.5 branch onto the mainline development trunk and ensuring that the script that cuts snapshots and releases works on the documentation.
56 lines
1.7 KiB
Perl
56 lines
1.7 KiB
Perl
@c
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@c Written by Eric Norum
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@c
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@c COPYRIGHT (c) 1988-2002.
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@c On-Line Applications Research Corporation (OAR).
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@c All rights reserved.
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@c
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@c $Id$
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@c
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@chapter Network Task Structure and Data Flow
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A schematic diagram of the tasks and message @b{mbuf} queues in a
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simple RTEMS networking application is shown in the following
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figure:
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@ifset use-ascii
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@example
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@group
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NO ASCII VERSION OF THE TASKING FIGURE IS AVAILABLE
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@end group
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@end example
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@end ifset
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@ifset use-tex
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@image{networkflow,5in,6in}
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@end ifset
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@ifset use-html
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@html
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<IMG SRC="networkflow.jpg" ALIGN=CENTER
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ALT="Network Task Structure and Data Flow">
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@end html
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@end ifset
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The transmit task for each network interface is normally blocked waiting
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for a packet to arrive in the transmit queue. Once a packet arrives, the
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transmit task may block waiting for an event from the transmit interrupt
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handler. The transmit interrupt handler sends an RTEMS event to the transmit
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task to indicate that transmit hardware resources have become available.
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The receive task for each network interface is normally blocked waiting
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for an event from the receive interrupt handler. When this event is received
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the receive task reads the packet and forwards it to the network stack
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for subsequent processing by the network task.
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The network task processes incoming packets and takes care of
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timed operations such as handling TCP timeouts and
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aging and removing routing table entries.
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The `Network code' contains routines which may run in the context of
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the user application tasks, the interface receive task or the network task.
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A network semaphore ensures that
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the data structures manipulated by the network code remain consistent.
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