source: rtems-docs/networking/network_task_structure.rst @ 42d50d7

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1.. comment SPDX-License-Identifier: CC-BY-SA-4.0
2
3.. COMMENT: Written by Eric Norum
4.. COMMENT: COPYRIGHT (c) 1988-2002.
5.. COMMENT: On-Line Applications Research Corporation (OAR).
6.. COMMENT: All rights reserved.
7
8Network Task Structure and Data Flow
9####################################
10
11A schematic diagram of the tasks and message *mbuf* queues in a simple RTEMS
12networking application is shown in the following figure:
13
14.. figure:: ../images/networking/networkflow.jpg
15  :align: center
16  :alt: Network Flow
17
18The transmit task for each network interface is normally blocked waiting for a
19packet to arrive in the transmit queue.  Once a packet arrives, the transmit
20task may block waiting for an event from the transmit interrupt handler.  The
21transmit interrupt handler sends an RTEMS event to the transmit task to
22indicate that transmit hardware resources have become available.
23
24The receive task for each network interface is normally blocked waiting for an
25event from the receive interrupt handler.  When this event is received the
26receive task reads the packet and forwards it to the network stack for
27subsequent processing by the network task.
28
29The network task processes incoming packets and takes care of timed operations
30such as handling TCP timeouts and aging and removing routing table entries.
31
32The 'Network code' contains routines which may run in the context of the user
33application tasks, the interface receive task or the network task.  A network
34semaphore ensures that the data structures manipulated by the network code
35remain consistent.
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