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Command and Variable Index
##########################
There are currently no Command and Variable Index entries.
.. COMMENT: @printindex fn

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DEC 21140 Driver
################
DEC 21240 Driver Introduction
=============================
.. COMMENT: XXX add back in cross reference to list of boards.
One aim of our project is to port RTEMS on a standard PowerPC platform.
To achieve it, we have chosen a Motorola MCP750 board. This board includes
an Ethernet controller based on a DEC21140 chip. Because RTEMS has a
TCP/IP stack, we will
have to develop the DEC21140 related ethernet driver for the PowerPC port of
RTEMS. As this controller is able to support 100Mbps network and as there is
a lot of PCI card using this DEC chip, we have decided to first
implement this driver on an Intel PC386 target to provide a solution for using
RTEMS on PC with the 100Mbps network and then to port this code on PowerPC in
a second phase.
The aim of this document is to give some PCI board generalities and
to explain the software architecture of the RTEMS driver. Finally, we will see
what will be done for ChorusOs and Netboot environment .
Document Revision History
=========================
*Current release*:
- Current applicable release is 1.0.
*Existing releases*:
- 1.0 : Released the 10/02/98. First version of this document.
- 0.1 : First draft of this document
*Planned releases*:
- None planned today.
DEC21140 PCI Board Generalities
===============================
.. COMMENT: XXX add crossreference to PCI Register Figure
This chapter describes rapidely the PCI interface of this Ethernet controller.
The board we have chosen for our PC386 implementation is a D-Link DFE-500TX.
This is a dual-speed 10/100Mbps Ethernet PCI adapter with a DEC21140AF chip.
Like other PCI devices, this board has a PCI device’s header containing some
required configuration registers, as shown in the PCI Register Figure.
By reading
or writing these registers, a driver can obtain information about the type of
the board, the interrupt it uses, the mapping of the chip specific registers, ...
On Intel target, the chip specific registers can be accessed via 2
methods : I/O port access or PCI address mapped access. We have chosen to implement
the PCI address access to obtain compatible source code to the port the driver
on a PowerPC target.
.. COMMENT: PCI Device's Configuration Header Space Format
.. image:: images/PCIreg.jpg
.. COMMENT: XXX add crossreference to PCI Register Figure
On RTEMS, a PCI API exists. We have used it to configure the board. After initializing
this PCI module via the ``pci_initialize()`` function, we try to detect
the DEC21140 based ethernet board. This board is characterized by its Vendor
ID (0x1011) and its Device ID (0x0009). We give these arguments to the``pcib_find_by_deviceid``
function which returns , if the device is present, a pointer to the configuration
header space (see PCI Registers Fgure). Once this operation performed,
the driver
is able to extract the information it needs to configure the board internal
registers, like the interrupt line, the base address,... The board internal
registers will not be detailled here. You can find them in *DIGITAL
Semiconductor 21140A PCI Fast Ethernet LAN Controller
- Hardware Reference Manual*.
.. COMMENT: fix citation
RTEMS Driver Software Architecture
==================================
In this chapter will see the initialization phase, how the controller uses the
host memory and the 2 threads launched at the initialization time.
Initialization phase
--------------------
The DEC21140 Ethernet driver keeps the same software architecture than the other
RTEMS ethernet drivers. The only API the programmer can use is the ``rtems_dec21140_driver_attach````(struct rtems_bsdnet_ifconfig \*config)`` function which
detects the board and initializes the associated data structure (with registers
base address, entry points to low-level initialization function,...), if the
board is found.
Once the attach function executed, the driver initializes the DEC
chip. Then the driver connects an interrupt handler to the interrupt line driven
by the Ethernet controller (the only interrupt which will be treated is the
receive interrupt) and launches 2 threads : a receiver thread and a transmitter
thread. Then the driver waits for incoming frame to give to the protocol stack
or outcoming frame to send on the physical link.
Memory Buffer
-------------
.. COMMENT: XXX add cross reference to Problem
This DEC chip uses the host memory to store the incoming Ethernet frames and
the descriptor of these frames. We have chosen to use 7 receive buffers and
1 transmit buffer to optimize memory allocation due to cache and paging problem
that will be explained in the section *Encountered Problems*.
To reference these buffers to the DEC chip we use a buffer descriptors
ring. The descriptor structure is defined in the Buffer Descriptor Figure.
Each descriptor
can reference one or two memory buffers. We choose to use only one buffer of
1520 bytes per descriptor.
The difference between a receive and a transmit buffer descriptor
is located in the status and control bits fields. We do not give details here,
please refer to the \[DEC21140 Hardware Manual].
.. COMMENT: Buffer Descriptor
.. image:: images/recvbd.jpg
Receiver Thread
---------------
This thread is event driven. Each time a DEC PCI board interrupt occurs, the
handler checks if this is a receive interrupt and send an event “reception”
to the receiver thread which looks into the entire buffer descriptors ring the
ones that contain a valid incoming frame (bit OWN=0 means descriptor belongs
to host processor). Each valid incoming ethernet frame is sent to the protocol
stack and the buffer descriptor is given back to the DEC board (the host processor
reset bit OWN, which means descriptor belongs to 21140).
Transmitter Thread
------------------
This thread is also event driven. Each time an Ethernet frame is put in the
transmit queue, an event is sent to the transmit thread, which empty the queue
by sending each outcoming frame. Because we use only one transmit buffer, we
are sure that the frame is well-sent before sending the next.
Encountered Problems
====================
On Intel PC386 target, we were faced with a problem of memory cache management.
Because the DEC chip uses the host memory to store the incoming frame and because
the DEC21140 configuration registers are mapped into the PCI address space,
we must ensure that the data read (or written) by the host processor are the
ones written (or read) by the DEC21140 device in the host memory and not old
data stored in the cache memory. Therefore, we had to provide a way to manage
the cache. This module is described in the document *RTEMS
Cache Management For Intel*. On Intel, the
memory region cache management is available only if the paging unit is enabled.
We have used this paging mechanism, with 4Kb page. All the buffers allocated
to store the incoming or outcoming frames, buffer descriptor and also the PCI
address space of the DEC board are located in a memory space with cache disable.
Concerning the buffers and their descriptors, we have tried to optimize
the memory space in term of allocated page. One buffer has 1520 bytes, one descriptor
has 16 bytes. We have 7 receive buffers and 1 transmit buffer, and for each,
1 descriptor : (7+1)*(1520+16) = 12288 bytes = 12Kb = 3 entire pages. This
allows not to lose too much memory or not to disable cache memory for a page
which contains other data than buffer, which could decrease performance.
ChorusOs DEC Driver
===================
Because ChorusOs is used in several Canon CRF projects, we must provide such
a driver on this OS to ensure compatibility between the RTEMS and ChorusOs developments.
On ChorusOs, a DEC driver source code already exists but only for a PowerPC
target. We plan to port this code (which uses ChorusOs API) on Intel target.
This will allow us to have homogeneous developments. Moreover, the port of the
development performed with ChorusOs environment to RTEMS environment will be
easier for the developers.
Netboot DEC driver
==================
We use Netboot tool to load our development from a server to the target via
an ethernet network. Currently, this tool does not support the DEC board. We
plan to port the DEC driver for the Netboot tool.
But concerning the port of the DEC driver into Netboot, we are faced
with a problem : in RTEMS environment, the DEC driver is interrupt or event
driven, in Netboot environment, it must be used in polling mode. It means that
we will have to re-write some mechanisms of this driver.
List of Ethernet cards using the DEC chip
=========================================
Many Ethernet adapter cards use the Tulip chip. Here is a non exhaustive list
of adapters which support this driver :
- Accton EtherDuo PCI.
- Accton EN1207 All three media types supported.
- Adaptec ANA6911/TX 21140-AC.
- Cogent EM110 21140-A with DP83840 N-Way MII transceiver.
- Cogent EM400 EM100 with 4 21140 100mbps-only ports + PCI Bridge.
- Danpex EN-9400P3.
- D-Link DFE500-Tx 21140-A with DP83840 transceiver.
- Kingston EtherX KNE100TX 21140AE.
- Netgear FX310 TX 10/100 21140AE.
- SMC EtherPower10/100 With DEC21140 and 68836 SYM transceiver.
- SMC EtherPower10/100 With DEC21140-AC and DP83840 MII transceiver.
Note: The EtherPower II uses the EPIC chip, which requires a different driver.
- Surecom EP-320X DEC 21140.
- Thomas Conrad TC5048.
- Znyx ZX345 21140-A, usually with the DP83840 N-Way MII transciever. Some ZX345
cards made in 1996 have an ICS 1890 transciver instead.
- ZNYX ZX348 Two 21140-A chips using ICS 1890 transcievers and either a 21052
or 21152 bridge. Early versions used National 83840 transcievers, but later
versions are depopulated ZX346 boards.
- ZNYX ZX351 21140 chip with a Broadcom 100BaseT4 transciever.
Our DEC driver has not been tested with all these cards, only with the D-Link
DFE500-TX.
- *[DEC21140 Hardware Manual] DIGITAL, *DIGITAL
Semiconductor 21140A PCI Fast Ethernet LAN Controller - Hardware
Reference Manual**.
- *[99.TA.0021.M.ER]Emmanuel Raguet,*RTEMS Cache Management For Intel**.

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.. include:: networking.rst
========================
RTEMS Network Supplement
========================
COPYRIGHT © 1988 - 2015.
On-Line Applications Research Corporation (OAR).
The authors have used their best efforts in preparing
this material. These efforts include the development, research,
and testing of the theories and programs to determine their
effectiveness. No warranty of any kind, expressed or implied,
with regard to the software or the material contained in this
document is provided. No liability arising out of the
application or use of any product described in this document is
assumed. The authors reserve the right to revise this material
and to make changes from time to time in the content hereof
without obligation to notify anyone of such revision or changes.
The RTEMS Project is hosted at http://www.rtems.org. Any
inquiries concerning RTEMS, its related support components, or its
documentation should be directed to the Community Project hosted athttp://www.rtems.org.
Any inquiries for commercial services including training, support, custom
development, application development assistance should be directed tohttp://www.rtems.com.
Table of Contents
-----------------
.. toctree::
preface
.. toctree::
:maxdepth: 3
:numbered:
preface
network_task_structure
networking_driver
using_networking_rtems_app
testing_the_driver
network_servers
dec_21140
command
* :ref:`genindex`
* :ref:`search`

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Network Servers
###############
RTEMS FTP Daemon
================
The RTEMS FTPD is a complete file transfer protocol (FTP) daemon
which can store, retrieve, and manipulate files on the local
filesystem. In addition, the RTEMS FTPD provides “hooks”
which are actions performed on received data. Hooks are useful
in situations where a destination file is not necessarily
appropriate or in cases when a formal device driver has not yet
been implemented.
This server was implemented and documented by Jake Janovetz
(janovetz@tempest.ece.uiuc.edu).
Configuration Parameters
------------------------
The configuration structure for FTPD is as follows:
.. code:: c
struct rtems_ftpd_configuration
{
rtems_task_priority priority; /* FTPD task priority \*/
unsigned long max_hook_filesize; /* Maximum buffersize \*/
/* for hooks \*/
int port; /* Well-known port \*/
struct rtems_ftpd_hook \*hooks; /* List of hooks \*/
};
The FTPD task priority is specified with ``priority``. Because
hooks are not saved as files, the received data is placed in an
allocated buffer. ``max_hook_filesize`` specifies the maximum
size of this buffer. Finally, ``hooks`` is a pointer to the
configured hooks structure.
Initializing FTPD (Starting the daemon)
---------------------------------------
Starting FTPD is done with a call to ``rtems_initialize_ftpd()``.
The configuration structure must be provided in the application
source code. Example hooks structure and configuration structure
folllow.
.. code:: c
struct rtems_ftpd_hook ftp_hooks[] =
{
{"untar", Untar_FromMemory},
{NULL, NULL}
};
struct rtems_ftpd_configuration rtems_ftpd_configuration =
{
40, /* FTPD task priority \*/
512*1024, /* Maximum hook 'file' size \*/
0, /* Use default port \*/
ftp_hooks /* Local ftp hooks \*/
};
Specifying 0 for the well-known port causes FTPD to use the
UNIX standard FTPD port (21).
Using Hooks
-----------
In the example above, one hook was installed. The hook causes
FTPD to call the function ``Untar_FromMemory`` when the
user sends data to the file ``untar``. The prototype for
the ``untar`` hook (and hooks, in general) is:
.. code:: c
int Untar_FromMemory(unsigned char \*tar_buf, unsigned long size);
An example FTP transcript which exercises this hook is:
.. code:: c
220 RTEMS FTP server (Version 1.0-JWJ) ready.
Name (dcomm0:janovetz): John Galt
230 User logged in.
Remote system type is RTEMS.
ftp> bin
200 Type set to I.
ftp> dir
200 PORT command successful.
150 ASCII data connection for LIST.
drwxrwx--x 0 0 268 dev
drwxrwx--x 0 0 0 TFTP
226 Transfer complete.
ftp> put html.tar untar
local: html.tar remote: untar
200 PORT command successful.
150 BINARY data connection.
210 File transferred successfully.
471040 bytes sent in 0.48 secs (9.6e+02 Kbytes/sec)
ftp> dir
200 PORT command successful.
150 ASCII data connection for LIST.
drwxrwx--x 0 0 268 dev
drwxrwx--x 0 0 0 TFTP
drwxrwx--x 0 0 3484 public_html
226 Transfer complete.
ftp> quit
221 Goodbye.
.. COMMENT: RTEMS Remote Debugger Server Specifications
.. COMMENT: Written by: Emmanuel Raguet <raguet@crf.canon.fr>

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Network Task Structure and Data Flow
####################################
A schematic diagram of the tasks and message *mbuf* queues in a
simple RTEMS networking application is shown in the following
figure:
.. image:: images/networkflow.jpg
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.
.. COMMENT: Written by Eric Norum
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.

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Networking Driver
#################
Introduction
============
This chapter is intended to provide an introduction to the
procedure for writing RTEMS network device drivers.
The example code is taken from the ‘Generic 68360’ network device
driver. The source code for this driver is located in the``c/src/lib/libbsp/m68k/gen68360/network`` directory in the RTEMS
source code distribution. Having a copy of this driver at
hand when reading the following notes will help significantly.
Learn about the network device
==============================
Before starting to write the network driver become completely
familiar with the programmer’s view of the device.
The following points list some of the details of the
device that must be understood before a driver can be written.
- Does the device use DMA to transfer packets to and from
memory or does the processor have to
copy packets to and from memory on the device?
- If the device uses DMA, is it capable of forming a single
outgoing packet from multiple fragments scattered in separate
memory buffers?
- If the device uses DMA, is it capable of chaining multiple
outgoing packets, or does each outgoing packet require
intervention by the driver?
- Does the device automatically pad short frames to the minimum
64 bytes or does the driver have to supply the padding?
- Does the device automatically retry a transmission on detection
of a collision?
- If the device uses DMA, is it capable of buffering multiple
packets to memory, or does the receiver have to be restarted
after the arrival of each packet?
- How are packets that are too short, too long, or received with
CRC errors handled? Does the device automatically continue
reception or does the driver have to intervene?
- How is the device Ethernet address set? How is the device
programmed to accept or reject broadcast and multicast packets?
- What interrupts does the device generate? Does it generate an
interrupt for each incoming packet, or only for packets received
without error? Does it generate an interrupt for each packet
transmitted, or only when the transmit queue is empty? What
happens when a transmit error is detected?
In addition, some controllers have specific questions regarding
board specific configuration. For example, the SONIC Ethernet
controller has a very configurable data bus interface. It can
even be configured for sixteen and thirty-two bit data buses. This
type of information should be obtained from the board vendor.
Understand the network scheduling conventions
=============================================
When writing code for the driver transmit and receive tasks,
take care to follow the network scheduling conventions. All tasks
which are associated with networking share various
data structures and resources. To ensure the consistency
of these structures the tasks
execute only when they hold the network semaphore (``rtems_bsdnet_semaphore``).
The transmit and receive tasks must abide by this protocol. Be very
careful to avoid ‘deadly embraces’ with the other network tasks.
A number of routines are provided to make it easier for the network
driver code to conform to the network task scheduling conventions.
- ``void rtems_bsdnet_semaphore_release(void)``
This function releases the network semaphore.
The network driver tasks must call this function immediately before
making any blocking RTEMS request.
- ``void rtems_bsdnet_semaphore_obtain(void)``
This function obtains the network semaphore.
If a network driver task has released the network semaphore to allow other
network-related tasks to run while the task blocks, then this function must
be called to reobtain the semaphore immediately after the return from the
blocking RTEMS request.
- ``rtems_bsdnet_event_receive(rtems_event_set, rtems_option, rtems_interval, rtems_event_set \*)``
The network driver task should call this function when it wishes to wait
for an event. This function releases the network semaphore,
calls ``rtems_event_receive`` to wait for the specified event
or events and reobtains the semaphore.
The value returned is the value returned by the ``rtems_event_receive``.
Network Driver Makefile
=======================
Network drivers are considered part of the BSD network package and as such
are to be compiled with the appropriate flags. This can be accomplished by
adding ``-D__INSIDE_RTEMS_BSD_TCPIP_STACK__`` to the ``command line``.
If the driver is inside the RTEMS source tree or is built using the
RTEMS application Makefiles, then adding the following line accomplishes
this:
.. code:: c
DEFINES += -D__INSIDE_RTEMS_BSD_TCPIP_STACK__
This is equivalent to the following list of definitions. Early versions
of the RTEMS BSD network stack required that all of these be defined.
.. code:: c
-D_COMPILING_BSD_KERNEL_ -DKERNEL -DINET -DNFS \\
-DDIAGNOSTIC -DBOOTP_COMPAT
Defining these macros tells the network header files that the driver
is to be compiled with extended visibility into the network stack. This
is in sharp contrast to applications that simply use the network stack.
Applications do not require this level of visibility and should stick
to the portable application level API.
As a direct result of being logically internal to the network stack,
network drivers use the BSD memory allocation routines This means,
for example, that malloc takes three arguments. See the SONIC
device driver (``c/src/lib/libchip/network/sonic.c``) for an example
of this. Because of this, network drivers should not include``<stdlib.h>``. Doing so will result in conflicting definitions
of ``malloc()``.
*Application level* code including network servers such as the FTP
daemon are *not* part of the BSD kernel network code and should not be
compiled with the BSD network flags. They should include``<stdlib.h>`` and not define the network stack visibility
macros.
Write the Driver Attach Function
================================
The driver attach function is responsible for configuring the driver
and making the connection between the network stack
and the driver.
Driver attach functions take a pointer to an``rtems_bsdnet_ifconfig`` structure as their only argument.
and set the driver parameters based on the
values in this structure. If an entry in the configuration
structure is zero the attach function chooses an
appropriate default value for that parameter.
The driver should then set up several fields in the ifnet structure
in the device-dependent data structure supplied and maintained by the driver:
``ifp->if_softc``
Pointer to the device-dependent data. The first entry
in the device-dependent data structure must be an ``arpcom``
structure.
``ifp->if_name``
The name of the device. The network stack uses this string
and the device number for device name lookups. The device name should
be obtained from the ``name`` entry in the configuration structure.
``ifp->if_unit``
The device number. The network stack uses this number and the
device name for device name lookups. For example, if``ifp->if_name`` is ‘``scc``’ and ``ifp->if_unit`` is ‘``1``’,
the full device name would be ‘``scc1``’. The unit number should be
obtained from the ‘name’ entry in the configuration structure.
``ifp->if_mtu``
The maximum transmission unit for the device. For Ethernet
devices this value should almost always be 1500.
``ifp->if_flags``
The device flags. Ethernet devices should set the flags
to ``IFF_BROADCAST|IFF_SIMPLEX``, indicating that the
device can broadcast packets to multiple destinations
and does not receive and transmit at the same time.
``ifp->if_snd.ifq_maxlen``
The maximum length of the queue of packets waiting to be
sent to the driver. This is normally set to ``ifqmaxlen``.
``ifp->if_init``
The address of the driver initialization function.
``ifp->if_start``
The address of the driver start function.
``ifp->if_ioctl``
The address of the driver ioctl function.
``ifp->if_output``
The address of the output function. Ethernet devices
should set this to ``ether_output``.
RTEMS provides a function to parse the driver name in the
configuration structure into a device name and unit number.
.. code:: c
int rtems_bsdnet_parse_driver_name (
const struct rtems_bsdnet_ifconfig \*config,
char \**namep
);
The function takes two arguments; a pointer to the configuration
structure and a pointer to a pointer to a character. The function
parses the configuration name entry, allocates memory for the driver
name, places the driver name in this memory, sets the second argument
to point to the name and returns the unit number.
On error, a message is printed and -1 is returned.
Once the attach function has set up the above entries it must link the
driver data structure onto the list of devices by
calling ``if_attach``. Ethernet devices should then
call ``ether_ifattach``. Both functions take a pointer to the
device’s ``ifnet`` structure as their only argument.
The attach function should return a non-zero value to indicate that
the driver has been successfully configured and attached.
Write the Driver Start Function.
================================
This function is called each time the network stack wants to start the
transmitter. This occures whenever the network stack adds a packet
to a device’s send queue and the ``IFF_OACTIVE`` bit in the
device’s ``if_flags`` is not set.
For many devices this function need only set the ``IFF_OACTIVE`` bit in the``if_flags`` and send an event to the transmit task
indicating that a packet is in the driver transmit queue.
Write the Driver Initialization Function.
=========================================
This function should initialize the device, attach to interrupt handler,
and start the driver transmit and receive tasks. The function
.. code:: c
rtems_id
rtems_bsdnet_newproc (char \*name,
int stacksize,
void(\*entry)(void \*),
void \*arg);
should be used to start the driver tasks.
Note that the network stack may call the driver initialization function more
than once.
Make sure multiple versions of the receive and transmit tasks are not accidentally
started.
Write the Driver Transmit Task
==============================
This task is reponsible for removing packets from the driver send queue and sending them to the device. The task should block waiting for an event from the
driver start function indicating that packets are waiting to be transmitted.
When the transmit task has drained the driver send queue the task should clear
the ``IFF_OACTIVE`` bit in ``if_flags`` and block until another outgoing
packet is queued.
Write the Driver Receive Task
=============================
This task should block until a packet arrives from the device. If the
device is an Ethernet interface the function ``ether_input`` should be called
to forward the packet to the network stack. The arguments to ``ether_input``
are a pointer to the interface data structure, a pointer to the ethernet
header and a pointer to an mbuf containing the packet itself.
Write the Driver Interrupt Handler
==================================
A typical interrupt handler will do nothing more than the hardware
manipulation required to acknowledge the interrupt and send an RTEMS event
to wake up the driver receive or transmit task waiting for the event.
Network interface interrupt handlers must not make any calls to other
network routines.
Write the Driver IOCTL Function
===============================
This function handles ioctl requests directed at the device. The ioctl
commands which must be handled are:
``SIOCGIFADDR``
``SIOCSIFADDR``
If the device is an Ethernet interface these
commands should be passed on to ``ether_ioctl``.
``SIOCSIFFLAGS``
This command should be used to start or stop the device,
depending on the state of the interface ``IFF_UP`` and``IFF_RUNNING`` bits in ``if_flags``:
``IFF_RUNNING``
Stop the device.
``IFF_UP``
Start the device.
``IFF_UP|IFF_RUNNING``
Stop then start the device.
``0``
Do nothing.
Write the Driver Statistic-Printing Function
============================================
This function should print the values of any statistic/diagnostic
counters the network driver may use. The driver ioctl function should call
the statistic-printing function when the ioctl command is``SIO_RTEMS_SHOW_STATS``.
.. COMMENT: Written by Eric Norum
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.

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Preface
#######
This document describes the RTEMS specific parts of the FreeBSD TCP/IP
stack. Much of this documentation was written by Eric Norum
(eric@skatter.usask.ca)
of the Saskatchewan Accelerator Laboratory
who also ported the FreeBSD TCP/IP stack to RTEMS.
The following is a list of resources which should be useful in trying
to understand Ethernet:
- *Charles Spurgeon’s Ethernet Web Site*
"This site provides extensive information about Ethernet
(IEEE 802.3) local area network (LAN) technology. Including
the original 10 Megabit per second (Mbps) system, the 100 Mbps
Fast Ethernet system (802.3u), and the Gigabit Ethernet system (802.3z)."
The URL is:
(http://www.ethermanage.com/ethernet/ethernet.html)
- *TCP/IP Illustrated, Volume 1 : The Protocols* by
by W. Richard Stevens (ISBN: 0201633469)
This book provides detailed introduction to TCP/IP and includes diagnostic
programs which are publicly available.
- *TCP/IP Illustrated, Volume 2 : The Implementation* by W. Richard
Stevens and Gary Wright (ISBN: 020163354X)
This book focuses on implementation issues regarding TCP/IP. The
treat for RTEMS users is that the implementation covered is the BSD
stack with most of the source code described in detail.
- *UNIX Network Programming, Volume 1 : 2nd Edition* by W. Richard
Stevens (ISBN: 0-13-490012-X)
This book describes how to write basic TCP/IP applications, again with primary
focus on the BSD stack.
.. COMMENT: Written by Eric Norum
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.

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Testing the Driver
##################
Preliminary Setup
=================
The network used to test the driver should include at least:
- The hardware on which the driver is to run.
It makes testing much easier if you can run a debugger to control
the operation of the target machine.
- An Ethernet network analyzer or a workstation with an
‘Ethernet snoop’ program such as ``ethersnoop`` or``tcpdump``.
- A workstation.
During early debug, you should consider putting the target, workstation,
and snooper on a small network by themselves. This offers a few
advantages:
- There is less traffic to look at on the snooper and for the target
to process while bringing the driver up.
- Any serious errors will impact only your small network not a building
or campus network. You want to avoid causing any unnecessary problems.
- Test traffic is easier to repeatably generate.
- Performance measurements are not impacted by other systems on
the network.
Debug Output
============
There are a number of sources of debug output that can be enabled
to aid in tracing the behavior of the network stack. The following
is a list of them:
- mbuf activity
There are commented out calls to ``printf`` in the file``sys/mbuf.h`` in the network stack code. Uncommenting
these lines results in output when mbuf’s are allocated
and freed. This is very useful for finding memory leaks.
- TX and RX queuing
There are commented out calls to ``printf`` in the file``net/if.h`` in the network stack code. Uncommenting
these lines results in output when packets are placed
on or removed from one of the transmit or receive packet
queues. These queues can be viewed as the boundary line
between a device driver and the network stack. If the
network stack is enqueuing packets to be transmitted that
the device driver is not dequeuing, then that is indicative
of a problem in the transmit side of the device driver.
Conversely, if the device driver is enqueueing packets
as it receives them (via a call to ``ether_input``) and
they are not being dequeued by the network stack,
then there is a problem. This situation would likely indicate
that the network server task is not running.
- TCP state transitions
In the unlikely event that one would actually want to see
TCP state transitions, the ``TCPDEBUG`` macro can be defined
in the file ``opt_tcpdebug.h``. This results in the routine``tcp_trace()`` being called by the network stack and
the state transitions logged into the ``tcp_debug`` data
structure. If the variable ``tcpconsdebug`` in the file``netinet/tcp_debug.c`` is set to 1, then the state transitions
will also be printed to the console.
Monitor Commands
================
There are a number of command available in the shell / monitor
to aid in tracing the behavior of the network stack. The following
is a list of them:
- ``inet``
This command shows the current routing information for the TCP/IP stack. Following is an
example showing the output of this command.
.. code:: c
Destination Gateway/Mask/Hw Flags Refs Use Expire Interface
10.0.0.0 255.0.0.0 U 0 0 17 smc1
127.0.0.1 127.0.0.1 UH 0 0 0 lo0
In this example, there is only one network interface with an IP address of 10.8.1.1. This
link is currently not up.
Two routes that are shown are the default routes for the Ethernet interface (10.0.0.0) and the
loopback interface (127.0.0.1).
Since the stack comes from BSD, this command is very similar to the netstat command. For more
details on the network routing please look the following
URL: (http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-routing.html)
For a quick reference to the flags, see the table below:
‘``U``’
Up: The route is active.
‘``H``’
Host: The route destination is a single host.
‘``G``’
Gateway: Send anything for this destination on to this remote system, which
will figure out from there where to send it.
‘``S``’
Static: This route was configured manually, not automatically generated by the
system.
‘``C``’
Clone: Generates a new route based upon this route for machines we connect
to. This type of route is normally used for local networks.
‘``W``’
WasCloned: Indicated a route that was auto-configured based upon a local area
network (Clone) route.
‘``L``’
Link: Route involves references to Ethernet hardware.
- ``mbuf``
This command shows the current MBUF statistics. An example of the command is shown below:
.. code:: c
************ MBUF STATISTICS \************
mbufs:4096 clusters: 256 free: 241
drops: 0 waits: 0 drains: 0
free:4080 data:16 header:0 socket:0
pcb:0 rtable:0 htable:0 atable:0
soname:0 soopts:0 ftable:0 rights:0
ifaddr:0 control:0 oobdata:0
- ``if``
This command shows the current statistics for your Ethernet driver as long as the ioctl hook``SIO_RTEMS_SHOW_STATS`` has been implemented. Below is an example:
.. code:: c
************ INTERFACE STATISTICS \************
\***** smc1 \*****
Ethernet Address: 00:12:76:43:34:25
Address:10.8.1.1 Broadcast Address:10.255.255.255 Net mask:255.0.0.0
Flags: Up Broadcast Running Simplex
Send queue limit:50 length:0 Dropped:0
SMC91C111 RTEMS driver A0.01 11/03/2002 Ian Caddy (ianc@microsol.iinet.net.au)
Rx Interrupts:0 Not First:0 Not Last:0
Giant:0 Runt:0 Non-octet:0
Bad CRC:0 Overrun:0 Collision:0
Tx Interrupts:2 Deferred:0 Missed Hearbeat:0
No Carrier:0 Retransmit Limit:0 Late Collision:0
Underrun:0 Raw output wait:0 Coalesced:0
Coalesce failed:0 Retries:0
\***** lo0 \*****
Address:127.0.0.1 Net mask:255.0.0.0
Flags: Up Loopback Running Multicast
Send queue limit:50 length:0 Dropped:0
- ``ip``
This command show the IP statistics for the currently configured interfaces.
- ``icmp``
This command show the ICMP statistics for the currently configured interfaces.
- ``tcp``
This command show the TCP statistics for the currently configured interfaces.
- ``udp``
This command show the UDP statistics for the currently configured interfaces.
Driver basic operation
======================
The network demonstration program ``netdemo`` may be used for these tests.
- Edit ``networkconfig.h`` to reflect the values for your network.
- Start with ``RTEMS_USE_BOOTP`` not defined.
- Edit ``networkconfig.h`` to configure the driver
with an
explicit Ethernet and Internet address and with reception of
broadcast packets disabled:
Verify that the program continues to run once the driver has been attached.
- Issue a ‘``u``’ command to send UDP
packets to the ‘discard’ port.
Verify that the packets appear on the network.
- Issue a ‘``s``’ command to print the network and driver statistics.
- On a workstation, add a static route to the target system.
- On that same workstation try to ‘ping’ the target system.
Verify that the ICMP echo request and reply packets appear on the net.
- Remove the static route to the target system.
Modify ``networkconfig.h`` to attach the driver
with reception of broadcast packets enabled.
Try to ‘ping’ the target system again.
Verify that ARP request/reply and ICMP echo request/reply packets appear
on the net.
- Issue a ‘``t``’ command to send TCP
packets to the ‘discard’ port.
Verify that the packets appear on the network.
- Issue a ‘``s``’ command to print the network and driver statistics.
- Verify that you can telnet to ports 24742
and 24743 on the target system from one or more
workstations on your network.
BOOTP/DHCP operation
====================
Set up a BOOTP/DHCP server on the network.
Set define ``RTEMS USE_BOOT`` in ``networkconfig.h``.
Run the ``netdemo`` test program.
Verify that the target system configures itself from the BOOTP/DHCP server and
that all the above tests succeed.
Stress Tests
============
Once the driver passes the tests described in the previous section it should
be subjected to conditions which exercise it more
thoroughly and which test its error handling routines.
Giant packets
-------------
- Recompile the driver with ``MAXIMUM_FRAME_SIZE`` set to
a smaller value, say 514.
- ‘Ping’ the driver from another workstation and verify
that frames larger than 514 bytes are correctly rejected.
- Recompile the driver with ``MAXIMUM_FRAME_SIZE`` restored to 1518.
Resource Exhaustion
-------------------
- Edit ``networkconfig.h``
so that the driver is configured with just two receive and transmit descriptors.
- Compile and run the ``netdemo`` program.
- Verify that the program operates properly and that you can
still telnet to both the ports.
- Display the driver statistics (Console ‘``s``’ command or telnet
‘control-G’ character) and verify that:
# The number of transmit interrupts is non-zero.
This indicates that all transmit descriptors have been in use at some time.
# The number of missed packets is non-zero.
This indicates that all receive descriptors have been in use at some time.
Cable Faults
------------
- Run the ``netdemo`` program.
- Issue a ‘``u``’ console command to make the target machine transmit
a bunch of UDP packets.
- While the packets are being transmitted, disconnect and reconnect the
network cable.
- Display the network statistics and verify that the driver has
detected the loss of carrier.
- Verify that you can still telnet to both ports on the target machine.
Throughput
----------
Run the ``ttcp`` network benchmark program.
Transfer large amounts of data (100’s of megabytes) to and from the target
system.
The procedure for testing throughput from a host to an RTEMS target
is as follows:
# Download and start the ttcp program on the Target.
# In response to the ``ttcp`` prompt, enter ``-s -r``. The
meaning of these flags is described in the ``ttcp.1`` manual page
found in the ``ttcp_orig`` subdirectory.
# On the host run ``ttcp -s -t <<insert the hostname or IP address of the Target here>>``
The procedure for testing throughput from an RTEMS target
to a Host is as follows:
# On the host run ``ttcp -s -r``.
# Download and start the ttcp program on the Target.
# In response to the ``ttcp`` prompt, enter ``-s -t <<insert the hostname or IP address of the Target here>>``. You need to type the
IP address of the host unless your Target is talking to your Domain Name
Server.
To change the number of buffers, the buffer size, etc. you just add the
extra flags to the ``-t`` machine as specified in the ``ttcp.1``
manual page found in the ``ttcp_orig`` subdirectory.
.. COMMENT: Text Written by Jake Janovetz
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.

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Using Networking in an RTEMS Application
########################################
Makefile changes
================
Including the required managers
-------------------------------
The FreeBSD networking code requires several RTEMS managers
in the application:
.. code:: c
MANAGERS = io event semaphore
Increasing the size of the heap
-------------------------------
The networking tasks allocate a lot of memory. For most applications
the heap should be at least 256 kbytes.
The amount of memory set aside for the heap can be adjusted by setting
the ``CFLAGS_LD`` definition as shown below:
.. code:: c
CFLAGS_LD += -Wl,--defsym -Wl,HeapSize=0x80000
This sets aside 512 kbytes of memory for the heap.
System Configuration
====================
The networking tasks allocate some RTEMS objects. These
must be accounted for in the application configuration table. The following
lists the requirements.
*TASKS*
One network task plus a receive and transmit task for each device.
*SEMAPHORES*
One network semaphore plus one syslog mutex semaphore if the application uses
openlog/syslog.
*EVENTS*
The network stack uses ``RTEMS_EVENT_24`` and ``RTEMS_EVENT_25``.
This has no effect on the application configuration, but
application tasks which call the network functions should not
use these events for other purposes.
Initialization
==============
Additional include files
------------------------
The source file which declares the network configuration
structures and calls the network initialization function must include
.. code:: c
#include <rtems/rtems_bsdnet.h>
Network Configuration
---------------------
The network configuration is specified by declaring
and initializing the ``rtems_bsdnet_config``
structure.
.. code:: c
struct rtems_bsdnet_config {
/*
* This entry points to the head of the ifconfig chain.
\*/
struct rtems_bsdnet_ifconfig \*ifconfig;
/*
* This entry should be rtems_bsdnet_do_bootp if BOOTP
* is being used to configure the network, and NULL
* if BOOTP is not being used.
\*/
void (\*bootp)(void);
/*
* The remaining items can be initialized to 0, in
* which case the default value will be used.
\*/
rtems_task_priority network_task_priority; /* 100 \*/
unsigned long mbuf_bytecount; /* 64 kbytes \*/
unsigned long mbuf_cluster_bytecount; /* 128 kbytes \*/
char \*hostname; /* BOOTP \*/
char \*domainname; /* BOOTP \*/
char \*gateway; /* BOOTP \*/
char \*log_host; /* BOOTP \*/
char \*name_server[3]; /* BOOTP \*/
char \*ntp_server[3]; /* BOOTP \*/
unsigned long sb_efficiency; /* 2 \*/
/* UDP TX: 9216 bytes \*/
unsigned long udp_tx_buf_size;
/* UDP RX: 40 * (1024 + sizeof(struct sockaddr_in)) \*/
unsigned long udp_rx_buf_size;
/* TCP TX: 16 * 1024 bytes \*/
unsigned long tcp_tx_buf_size;
/* TCP TX: 16 * 1024 bytes \*/
unsigned long tcp_rx_buf_size;
/* Default Network Tasks CPU Affinity \*/
#ifdef RTEMS_SMP
const cpu_set_t \*network_task_cpuset;
size_t network_task_cpuset_size;
#endif
};
The structure entries are described in the following table.
If your application uses BOOTP/DHCP to obtain network configuration
information and if you are happy with the default values described
below, you need to provide only the first two entries in this structure.
``struct rtems_bsdnet_ifconfig \*ifconfig``
A pointer to the first configuration structure of the first network
device. This structure is described in the following section.
You must provide a value for this entry since there is no default value for it.
``void (\*bootp)(void)``
This entry should be set to ``rtems_bsdnet_do_bootp`` if your
application by default uses the BOOTP/DHCP client protocol to obtain
network configuration information. It should be set to ``NULL`` if
your application does not use BOOTP/DHCP.
You can also use ``rtems_bsdnet_do_bootp_rootfs`` to have a set of
standard files created with the information return by the BOOTP/DHCP
protocol. The IP address is added to :file:`/etc/hosts` with the host
name and domain returned. If no host name or domain is returned``me.mydomain`` is used. The BOOTP/DHCP server’s address is also
added to :file:`/etc/hosts`. The domain name server listed in the
BOOTP/DHCP information are added to :file:`/etc/resolv.conf`. A``search`` record is also added if a domain is returned. The files
are created if they do not exist.
The default ``rtems_bsdnet_do_bootp`` and``rtems_bsdnet_do_bootp_rootfs`` handlers will loop for-ever
waiting for a BOOTP/DHCP server to respond. If an error is detected
such as not valid interface or valid hardware address the target will
reboot allowing any hardware reset to correct itself.
You can provide your own custom handler which allows you to perform
an initialization that meets your specific system requirements. For
example you could try BOOTP/DHCP then enter a configuration tool if no
server is found allowing the user to switch to a static configuration.
``int network_task_priority``
The priority at which the network task and network device
receive and transmit tasks will run.
If a value of 0 is specified the tasks will run at priority 100.
``unsigned long mbuf_bytecount``
The number of bytes to allocate from the heap for use as mbufs.
If a value of 0 is specified, 64 kbytes will be allocated.
``unsigned long mbuf_cluster_bytecount``
The number of bytes to allocate from the heap for use as mbuf clusters.
If a value of 0 is specified, 128 kbytes will be allocated.
``char \*hostname``
The host name of the system.
If this, or any of the following, entries are ``NULL`` the value
may be obtained from a BOOTP/DHCP server.
``char \*domainname``
The name of the Internet domain to which the system belongs.
``char \*gateway``
The Internet host number of the network gateway machine,
specified in ’dotted decimal’ (``129.128.4.1``) form.
``char \*log_host``
The Internet host number of the machine to which ``syslog`` messages
will be sent.
``char \*name_server[3]``
The Internet host numbers of up to three machines to be used as
Internet Domain Name Servers.
``char \*ntp_server[3]``
The Internet host numbers of up to three machines to be used as
Network Time Protocol (NTP) Servers.
``unsigned long sb_efficiency``
This is the first of five configuration parameters related to
the amount of memory each socket may consume for buffers. The
TCP/IP stack reserves buffers (e.g. mbufs) for each open socket. The
TCP/IP stack has different limits for the transmit and receive
buffers associated with each TCP and UDP socket. By tuning these
parameters, the application developer can make trade-offs between
memory consumption and performance. The default parameters favor
performance over memory consumption. Seehttp://www.rtems.org/ml/rtems-users/2004/february/msg00200.html
for more details but note that after the RTEMS 4.8 release series,
the sb_efficiency default was changed from ``8`` to ``2``.
The user should also be aware of the ``SO_SNDBUF`` and ``SO_RCVBUF``
IO control operations. These can be used to specify the
send and receive buffer sizes for a specific socket. There
is no standard IO control to change the ``sb_efficiency`` factor.
The ``sb_efficiency`` parameter is a buffering factor used
in the implementation of the TCP/IP stack. The default is ``2``
which indicates double buffering. When allocating memory for each
socket, this number is multiplied by the buffer sizes for that socket.
``unsigned long udp_tx_buf_size``
This configuration parameter specifies the maximum amount of
buffer memory which may be used for UDP sockets to transmit
with. The default size is 9216 bytes which corresponds to
the maximum datagram size.
``unsigned long udp_rx_buf_size``
This configuration parameter specifies the maximum amount of
buffer memory which may be used for UDP sockets to receive
into. The default size is the following length in bytes:
.. code:: c
40 * (1024 + sizeof(struct sockaddr_in)
``unsigned long tcp_tx_buf_size``
This configuration parameter specifies the maximum amount of
buffer memory which may be used for TCP sockets to transmit
with. The default size is sixteen kilobytes.
``unsigned long tcp_rx_buf_size``
This configuration parameter specifies the maximum amount of
buffer memory which may be used for TCP sockets to receive
into. The default size is sixteen kilobytes.
``const cpu_set_t \*network_task_cpuset``
This configuration parameter specifies the CPU affinity of the
network task. If set to ``0`` the network task can be scheduled on
any CPU. Only available in SMP configurations.
``size_t network_task_cpuset_size``
This configuration parameter specifies the size of the``network_task_cpuset`` used. Only available in SMP configurations.
In addition, the following fields in the ``rtems_bsdnet_ifconfig``
are of interest.
*int port*
The I/O port number (ex: 0x240) on which the external Ethernet
can be accessed.
*int irno*
The interrupt number of the external Ethernet controller.
*int bpar*
The address of the shared memory on the external Ethernet controller.
Network device configuration
----------------------------
Network devices are specified and configured by declaring and initializing a``struct rtems_bsdnet_ifconfig`` structure for each network device.
The structure entries are described in the following table. An application
which uses a single network interface, gets network configuration information
from a BOOTP/DHCP server, and uses the default values for all driver
parameters needs to initialize only the first two entries in the
structure.
``char \*name``
The full name of the network device. This name consists of the
driver name and the unit number (e.g. ``"scc1"``).
The ``bsp.h`` include file usually defines RTEMS_BSP_NETWORK_DRIVER_NAME as
the name of the primary (or only) network driver.
``int (\*attach)(struct rtems_bsdnet_ifconfig \*conf)``
The address of the driver ``attach`` function. The network
initialization function calls this function to configure the driver and
attach it to the network stack.
The ``bsp.h`` include file usually defines RTEMS_BSP_NETWORK_DRIVER_ATTACH as
the name of the attach function of the primary (or only) network driver.
``struct rtems_bsdnet_ifconfig \*next``
A pointer to the network device configuration structure for the next network
interface, or ``NULL`` if this is the configuration structure of the
last network interface.
``char \*ip_address``
The Internet address of the device,
specified in ‘dotted decimal’ (``129.128.4.2``) form, or ``NULL``
if the device configuration information is being obtained from a
BOOTP/DHCP server.
``char \*ip_netmask``
The Internet inetwork mask of the device,
specified in ‘dotted decimal’ (``255.255.255.0``) form, or ``NULL``
if the device configuration information is being obtained from a
BOOTP/DHCP server.
``void \*hardware_address``
The hardware address of the device, or ``NULL`` if the driver is
to obtain the hardware address in some other way (usually by reading
it from the device or from the bootstrap ROM).
``int ignore_broadcast``
Zero if the device is to accept broadcast packets, non-zero if the device
is to ignore broadcast packets.
``int mtu``
The maximum transmission unit of the device, or zero if the driver
is to choose a default value (typically 1500 for Ethernet devices).
``int rbuf_count``
The number of receive buffers to use, or zero if the driver is to
choose a default value
``int xbuf_count``
The number of transmit buffers to use, or zero if the driver is to
choose a default value
Keep in mind that some network devices may use 4 or more
transmit descriptors for a single transmit buffer.
A complete network configuration specification can be as simple as the one
shown in the following example.
This configuration uses a single network interface, gets
network configuration information
from a BOOTP/DHCP server, and uses the default values for all driver
parameters.
.. code:: c
static struct rtems_bsdnet_ifconfig netdriver_config = {
RTEMS_BSP_NETWORK_DRIVER_NAME,
RTEMS_BSP_NETWORK_DRIVER_ATTACH
};
struct rtems_bsdnet_config rtems_bsdnet_config = {
&netdriver_config,
rtems_bsdnet_do_bootp,
};
Network initialization
----------------------
The networking tasks must be started before any network I/O operations
can be performed. This is done by calling:
.. code:: c
rtems_bsdnet_initialize_network ();
This function is declared in ``rtems/rtems_bsdnet.h``.
t returns 0 on success and -1 on failure with an error code
in ``errno``. It is not possible to undo the effects of
a partial initialization, though, so the function can be
called only once irregardless of the return code. Consequently,
if the condition for the failure can be corrected, the
system must be reset to permit another network initialization
attempt.
Application Programming Interface
=================================
The RTEMS network package provides almost a complete set of BSD network
services. The network functions work like their BSD counterparts
with the following exceptions:
- A given socket can be read or written by only one task at a time.
- The ``select`` function only works for file descriptors associated
with sockets.
- You must call ``openlog`` before calling any of the ``syslog`` functions.
- *Some of the network functions are not thread-safe.*
For example the following functions return a pointer to a static
buffer which remains valid only until the next call:
``gethostbyaddr``
``gethostbyname``
``inet_ntoa``
(``inet_ntop`` is thread-safe, though).
- The RTEMS network package gathers statistics.
- Addition of a mechanism to "tap onto" an interface
and monitor every packet received and transmitted.
- Addition of ``SO_SNDWAKEUP`` and ``SO_RCVWAKEUP`` socket options.
Some of the new features are discussed in more detail in the following
sections.
Network Statistics
------------------
There are a number of functions to print statistics gathered by
the network stack.
These function are declared in ``rtems/rtems_bsdnet.h``.
``rtems_bsdnet_show_if_stats``
Display statistics gathered by network interfaces.
``rtems_bsdnet_show_ip_stats``
Display IP packet statistics.
``rtems_bsdnet_show_icmp_stats``
Display ICMP packet statistics.
``rtems_bsdnet_show_tcp_stats``
Display TCP packet statistics.
``rtems_bsdnet_show_udp_stats``
Display UDP packet statistics.
``rtems_bsdnet_show_mbuf_stats``
Display mbuf statistics.
``rtems_bsdnet_show_inet_routes``
Display the routing table.
Tapping Into an Interface
-------------------------
RTEMS add two new ioctls to the BSD networking code:
SIOCSIFTAP and SIOCGIFTAP. These may be used to set and get a*tap function*. The tap function will be called for every
Ethernet packet received by the interface.
These are called like other interface ioctls, such as SIOCSIFADDR.
When setting the tap function with SIOCSIFTAP, set the ifr_tap field
of the ifreq struct to the tap function. When retrieving the tap
function with SIOCGIFTAP, the current tap function will be returned in
the ifr_tap field. To stop tapping packets, call SIOCSIFTAP with a
ifr_tap field of 0.
The tap function is called like this:
.. code:: c
int tap (struct ifnet \*, struct ether_header \*, struct mbuf \*)
The tap function should return 1 if the packet was fully handled, in
which case the caller will simply discard the mbuf. The tap function
should return 0 if the packet should be passed up to the higher
networking layers.
The tap function is called with the network semaphore locked. It must
not make any calls on the application levels of the networking level
itself. It is safe to call other non-networking RTEMS functions.
Socket Options
--------------
RTEMS adds two new ``SOL_SOCKET`` level options for ``setsockopt`` and``getsockopt``: ``SO_SNDWAKEUP`` and ``SO_RCVWAKEUP``. For both, the
option value should point to a sockwakeup structure. The sockwakeup
structure has the following fields:
.. code:: c
void (\*sw_pfn) (struct socket \*, caddr_t);
caddr_t sw_arg;
These options are used to set a callback function to be called when, for
example, there is
data available from the socket (``SO_RCVWAKEUP``) and when there is space
available to accept data written to the socket (``SO_SNDWAKEUP``).
If ``setsockopt`` is called with the ``SO_RCVWAKEUP`` option, and the``sw_pfn`` field is not zero, then when there is data
available to be read from
the socket, the function pointed to by the ``sw_pfn`` field will be
called. A pointer to the socket structure will be passed as the first
argument to the function. The ``sw_arg`` field set by the``SO_RCVWAKEUP`` call will be passed as the second argument to the function.
If ``setsockopt`` is called with the ``SO_SNDWAKEUP``
function, and the ``sw_pfn`` field is not zero, then when
there is space available to accept data written to the socket,
the function pointed to by the ``sw_pfn`` field
will be called. The arguments passed to the function will be as with``SO_SNDWAKEUP``.
When the function is called, the network semaphore will be locked and
the callback function runs in the context of the networking task.
The function must be careful not to call any networking functions. It
is OK to call an RTEMS function; for example, it is OK to send an
RTEMS event.
The purpose of these callback functions is to permit a more efficient
alternative to the select call when dealing with a large number of
sockets.
The callbacks are called by the same criteria that the select
function uses for indicating "ready" sockets. In Stevens *Unix
Network Programming* on page 153-154 in the section "Under what Conditions
Is a Descriptor Ready?" you will find the definitive list of conditions
for readable and writable that also determine when the functions are
called.
When the number of received bytes equals or exceeds the socket receive
buffer "low water mark" (default 1 byte) you get a readable callback. If
there are 100 bytes in the receive buffer and you only read 1, you will
not immediately get another callback. However, you will get another
callback after you read the remaining 99 bytes and at least 1 more byte
arrives. Using a non-blocking socket you should probably read until it
produces error EWOULDBLOCK and then allow the readable callback to tell
you when more data has arrived. (Condition 1.a.)
For sending, when the socket is connected and the free space becomes at
or above the "low water mark" for the send buffer (default 4096 bytes)
you will receive a writable callback. You don’t get continuous callbacks
if you don’t write anything. Using a non-blocking write socket, you can
then call write until it returns a value less than the amount of data
requested to be sent or it produces error EWOULDBLOCK (indicating buffer
full and no longer writable). When this happens you can
try the write again, but it is often better to go do other things and
let the writable callback tell you when space is available to send
again. You only get a writable callback when the free space transitions
to above the "low water mark" and not every time you
write to a non-full send buffer. (Condition 2.a.)
The remaining conditions enumerated by Stevens handle the fact that
sockets become readable and/or writable when connects, disconnects and
errors occur, not just when data is received or sent. For example, when
a server "listening" socket becomes readable it indicates that a client
has connected and accept can be called without blocking, not that
network data was received (Condition 1.c).
Adding an IP Alias
------------------
The following code snippet adds an IP alias:
.. code:: c
void addAlias(const char \*pName, const char \*pAddr, const char \*pMask)
{
struct ifaliasreq aliasreq;
struct sockaddr_in \*in;
/* initialize alias request \*/
memset(&aliasreq, 0, sizeof(aliasreq));
sprintf(aliasreq.ifra_name, pName);
/* initialize alias address \*/
in = (struct sockaddr_in \*)&aliasreq.ifra_addr;
in->sin_family = AF_INET;
in->sin_len = sizeof(aliasreq.ifra_addr);
in->sin_addr.s_addr = inet_addr(pAddr);
/* initialize alias mask \*/
in = (struct sockaddr_in \*)&aliasreq.ifra_mask;
in->sin_family = AF_INET;
in->sin_len = sizeof(aliasreq.ifra_mask);
in->sin_addr.s_addr = inet_addr(pMask);
/* call to setup the alias \*/
rtems_bsdnet_ifconfig(pName, SIOCAIFADDR, &aliasreq);
}
Thanks to `Mike Seirs <mailto:mikes@poliac.com>`_ for this example
code.
Adding a Default Route
----------------------
The function provided in this section is functionally equivalent to
the command ``route add default gw yyy.yyy.yyy.yyy``:
.. code:: c
void mon_ifconfig(int argc, char \*argv[], unsigned32 command_arg,
bool verbose)
{
struct sockaddr_in ipaddr;
struct sockaddr_in dstaddr;
struct sockaddr_in netmask;
struct sockaddr_in broadcast;
char \*iface;
int f_ip = 0;
int f_ptp = 0;
int f_netmask = 0;
int f_up = 0;
int f_down = 0;
int f_bcast = 0;
int cur_idx;
int rc;
int flags;
bzero((void*) &ipaddr, sizeof(ipaddr));
bzero((void*) &dstaddr, sizeof(dstaddr));
bzero((void*) &netmask, sizeof(netmask));
bzero((void*) &broadcast, sizeof(broadcast));
ipaddr.sin_len = sizeof(ipaddr);
ipaddr.sin_family = AF_INET;
dstaddr.sin_len = sizeof(dstaddr);
dstaddr.sin_family = AF_INET;
netmask.sin_len = sizeof(netmask);
netmask.sin_family = AF_INET;
broadcast.sin_len = sizeof(broadcast);
broadcast.sin_family = AF_INET;
cur_idx = 0;
if (argc <= 1) {
/* display all interfaces \*/
iface = NULL;
cur_idx += 1;
} else {
iface = argv[1];
if (isdigit(\*argv[2])) {
if (inet_pton(AF_INET, argv[2], &ipaddr.sin_addr) < 0) {
printf("bad ip address: %s\\n", argv[2]);
return;
}
f_ip = 1;
cur_idx += 3;
} else {
cur_idx += 2;
}
}
if ((f_down !=0) && (f_ip != 0)) {
f_up = 1;
}
while(argc > cur_idx) {
if (strcmp(argv[cur_idx], "up") == 0) {
f_up = 1;
if (f_down != 0) {
printf("Can't make interface up and down\\n");
}
} else if(strcmp(argv[cur_idx], "down") == 0) {
f_down = 1;
if (f_up != 0) {
printf("Can't make interface up and down\\n");
}
} else if(strcmp(argv[cur_idx], "netmask") == 0) {
if ((cur_idx + 1) >= argc) {
printf("No netmask address\\n");
return;
}
if (inet_pton(AF_INET, argv[cur_idx+1], &netmask.sin_addr) < 0) {
printf("bad netmask: %s\\n", argv[cur_idx]);
return;
}
f_netmask = 1;
cur_idx += 1;
} else if(strcmp(argv[cur_idx], "broadcast") == 0) {
if ((cur_idx + 1) >= argc) {
printf("No broadcast address\\n");
return;
}
if (inet_pton(AF_INET, argv[cur_idx+1], &broadcast.sin_addr) < 0) {
printf("bad broadcast: %s\\n", argv[cur_idx]);
return;
}
f_bcast = 1;
cur_idx += 1;
} else if(strcmp(argv[cur_idx], "pointopoint") == 0) {
if ((cur_idx + 1) >= argc) {
printf("No pointopoint address\\n");
return;
}
if (inet_pton(AF_INET, argv[cur_idx+1], &dstaddr.sin_addr) < 0) {
printf("bad pointopoint: %s\\n", argv[cur_idx]);
return;
}
f_ptp = 1;
cur_idx += 1;
} else {
printf("Bad parameter: %s\\n", argv[cur_idx]);
return;
}
cur_idx += 1;
}
printf("ifconfig ");
if (iface != NULL) {
printf("%s ", iface);
if (f_ip != 0) {
char str[256];
inet_ntop(AF_INET, &ipaddr.sin_addr, str, 256);
printf("%s ", str);
}
if (f_netmask != 0) {
char str[256];
inet_ntop(AF_INET, &netmask.sin_addr, str, 256);
printf("netmask %s ", str);
}
if (f_bcast != 0) {
char str[256];
inet_ntop(AF_INET, &broadcast.sin_addr, str, 256);
printf("broadcast %s ", str);
}
if (f_ptp != 0) {
char str[256];
inet_ntop(AF_INET, &dstaddr.sin_addr, str, 256);
printf("pointopoint %s ", str);
}
if (f_up != 0) {
printf("up\\n");
} else if (f_down != 0) {
printf("down\\n");
} else {
printf("\\n");
}
}
if ((iface == NULL) \|| ((f_ip == 0) && (f_down == 0) && (f_up == 0))) {
rtems_bsdnet_show_if_stats();
return;
}
flags = 0;
if (f_netmask) {
rc = rtems_bsdnet_ifconfig(iface, SIOCSIFNETMASK, &netmask);
if (rc < 0) {
printf("Could not set netmask: %s\\n", strerror(errno));
return;
}
}
if (f_bcast) {
rc = rtems_bsdnet_ifconfig(iface, SIOCSIFBRDADDR, &broadcast);
if (rc < 0) {
printf("Could not set broadcast: %s\\n", strerror(errno));
return;
}
}
if (f_ptp) {
rc = rtems_bsdnet_ifconfig(iface, SIOCSIFDSTADDR, &dstaddr);
if (rc < 0) {
printf("Could not set destination address: %s\\n", strerror(errno));
return;
}
flags \|= IFF_POINTOPOINT;
}
/* This must come _after_ setting the netmask, broadcast addresses \*/
if (f_ip) {
rc = rtems_bsdnet_ifconfig(iface, SIOCSIFADDR, &ipaddr);
if (rc < 0) {
printf("Could not set IP address: %s\\n", strerror(errno));
return;
}
}
if (f_up != 0) {
flags \|= IFF_UP;
}
if (f_down != 0) {
printf("Warning: taking interfaces down is not supported\\n");
}
rc = rtems_bsdnet_ifconfig(iface, SIOCSIFFLAGS, &flags);
if (rc < 0) {
printf("Could not set interface flags: %s\\n", strerror(errno));
return;
}
}
void mon_route(int argc, char \*argv[], unsigned32 command_arg,
bool verbose)
{
int cmd;
struct sockaddr_in dst;
struct sockaddr_in gw;
struct sockaddr_in netmask;
int f_host;
int f_gw = 0;
int cur_idx;
int flags;
int rc;
memset(&dst, 0, sizeof(dst));
memset(&gw, 0, sizeof(gw));
memset(&netmask, 0, sizeof(netmask));
dst.sin_len = sizeof(dst);
dst.sin_family = AF_INET;
dst.sin_addr.s_addr = inet_addr("0.0.0.0");
gw.sin_len = sizeof(gw);
gw.sin_family = AF_INET;
gw.sin_addr.s_addr = inet_addr("0.0.0.0");
netmask.sin_len = sizeof(netmask);
netmask.sin_family = AF_INET;
netmask.sin_addr.s_addr = inet_addr("255.255.255.0");
if (argc < 2) {
rtems_bsdnet_show_inet_routes();
return;
}
if (strcmp(argv[1], "add") == 0) {
cmd = RTM_ADD;
} else if (strcmp(argv[1], "del") == 0) {
cmd = RTM_DELETE;
} else {
printf("invalid command: %s\\n", argv[1]);
printf("\\tit should be 'add' or 'del'\\n");
return;
}
if (argc < 3) {
printf("not enough arguments\\n");
return;
}
if (strcmp(argv[2], "-host") == 0) {
f_host = 1;
} else if (strcmp(argv[2], "-net") == 0) {
f_host = 0;
} else {
printf("Invalid type: %s\\n", argv[1]);
printf("\\tit should be '-host' or '-net'\\n");
return;
}
if (argc < 4) {
printf("not enough arguments\\n");
return;
}
inet_pton(AF_INET, argv[3], &dst.sin_addr);
cur_idx = 4;
while(cur_idx < argc) {
if (strcmp(argv[cur_idx], "gw") == 0) {
if ((cur_idx +1) >= argc) {
printf("no gateway address\\n");
return;
}
f_gw = 1;
inet_pton(AF_INET, argv[cur_idx + 1], &gw.sin_addr);
cur_idx += 1;
} else if(strcmp(argv[cur_idx], "netmask") == 0) {
if ((cur_idx +1) >= argc) {
printf("no netmask address\\n");
return;
}
f_gw = 1;
inet_pton(AF_INET, argv[cur_idx + 1], &netmask.sin_addr);
cur_idx += 1;
} else {
printf("Unknown argument\\n");
return;
}
cur_idx += 1;
}
flags = RTF_STATIC;
if (f_gw != 0) {
flags \|= RTF_GATEWAY;
}
if (f_host != 0) {
flags \|= RTF_HOST;
}
rc = rtems_bsdnet_rtrequest(cmd, &dst, &gw, &netmask, flags, NULL);
if (rc < 0) {
printf("Error adding route\\n");
}
}
Thanks to `Jay Monkman <mailto:jtm@smoothmsmoothie.com>`_ for this example
code.
Time Synchronization Using NTP
------------------------------
.. code:: c
int rtems_bsdnet_synchronize_ntp (int interval, rtems_task_priority priority);
If the interval argument is 0 the routine synchronizes the RTEMS time-of-day
clock with the first NTP server in the rtems_bsdnet_ntpserve array and
returns. The priority argument is ignored.
If the interval argument is greater than 0, the routine also starts an
RTEMS task at the specified priority and polls the NTP server every
‘interval’ seconds. NOTE: This mode of operation has not yet been
implemented.
On successful synchronization of the RTEMS time-of-day clock the routine
returns 0. If an error occurs a message is printed and the routine returns -1
with an error code in errno.
There is no timeout – if there is no response from an NTP server the
routine will wait forever.
.. COMMENT: Written by Eric Norum
.. COMMENT: COPYRIGHT (c) 1988-2002.
.. COMMENT: On-Line Applications Research Corporation (OAR).
.. COMMENT: All rights reserved.