source: rtems/doc/networking/networkapp.t @ 847375f

@c
@c  Written by Eric Norum
@c
@c  COPYRIGHT (c) 1988-1998.
@c  On-Line Applications Research Corporation (OAR).
@c  All rights reserved.
@c
@c  $Id$
@c

@chapter Using Networking in an RTEMS Application

@section Makefile changes
@subsection Including the required managers
The FreeBSD networking code requires several RTEMS managers
in the application:

@example
MANAGERS = io event semaphore
@end example

@subsection 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 @code{CFLAGS_LD} definition as shown below:

@example
CFLAGS_LD += -Wl,--defsym -Wl,HeapSize=0x80000
@end example

This sets aside 512 kbytes of memory for the heap.

@section System Configuration

The networking tasks allocate some RTEMS objects.  These
must be accounted for in the application configuration table.  The following
lists the requirements.

@table @b
@item TASKS
One network task plus a receive and transmit task for each device.

@item SEMAPHORES
One network semaphore plus one syslog mutex semaphore if the application uses
openlog/syslog.

@item EVENTS
The network stack uses @code{RTEMS_EVENT_24} and @code{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.

@end table

@section Initialization
@subsection Additional include files
The source file which declares the network configuration
structures and calls the network initialization function must include

@example
#include <rtems/rtems_bsdnet.h>
@end example

@subsection Network configuration
The network configuration is specified by declaring
and initializing the @code{rtems_bsdnet_configuration}
structure.

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.

@table @code

@item 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.


@item void (*bootp)(void)
This entry should be set to @code{rtems_bsdnet_do_bootp}
if your application will use BOOTP/DHCP
to obtain network configuration information.
It should be set to @code{NULL}
if your application does not use BOOTP/DHCP.


@item 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.

@item 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.

@item 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.

@item char *hostname
The host name of the system.
If this, or any of the following, entries are @code{NULL} the value
may be obtained from a BOOTP/DHCP server.

@item char *domainname
The name of the Internet domain to which the system belongs.

@item char *gateway
The Internet host number of the network gateway machine,
specified in `dotted decimal' (@code{129.128.4.1}) form.

@item char *log_host
The Internet host number of the machine to which @code{syslog} messages
will be sent.

@item char *name_server[3]
The Internet host numbers of up to three machines to be used as
Internet Domain Name Servers.

@item int port
The I/O port number (ex: 0x240) on which the external Ethernet
can be accessed.

@item int irno
The interrupt number of the external Ethernet controller.

@item int bpar
The address of the shared memory on the external Ethernet controller.


@end table

@subsection Network device configuration
Network devices are specified and configured by declaring and initializing a
@code{struct rtems_bsdnet_ifcontig} 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.

@table @code
@item char *name
The full name of the network device.  This name consists of the
driver name and the unit number (e.g. @code{"scc1"}).
The @code{bsp.h} include file usually defines RTEMS_BSP_NETWORK_DRIVER_NAME as
the name of the primary (or only) network driver.

@item int (*attach)(struct rtems_bsdnet_ifconfig *conf)
The address of the driver @code{attach} function.   The network 
initialization function calls this function to configure the driver and
attach it to the network stack.
The @code{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.

@item struct rtems_bsdnet_ifconfig *next
A pointer to the network device configuration structure for the next network 
interface, or @code{NULL} if this is the configuration structure of the
last network interface.

@item char *ip_address
The Internet address of the device,
specified in `dotted decimal' (@code{129.128.4.2}) form, or @code{NULL}
if the device configuration information is being obtained from a
BOOTP/DHCP server.

@item char *ip_netmask
The Internet inetwork mask of the device,
specified in `dotted decimal' (@code{255.255.255.0}) form, or @code{NULL}
if the device configuration information is being obtained from a
BOOTP/DHCP server.


@item void *hardware_address
The hardware address of the device, or @code{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).

@item int ignore_broadcast
Zero if the device is to accept broadcast packets, non-zero if the device
is to ignore broadcast packets.

@item 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).

@item int rbuf_count
The number of receive buffers to use, or zero if the driver is to
choose a default value

@item 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.

@end table

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.

@example
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,
@};
@end example


@subsection Network initialization
The networking tasks must be started before any
network I/O operations can be performed.  This is done by calling:
@example
rtems_bsdnet_initialize_network ();
@end example

This function is declared in @code{rtems/rtems_bsdnet.h}.



@section Application code
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:

@itemize @bullet
@item A given socket can be read or written by only one task at a time.
@item There is no @code{select} function.
@item You must call @code{openlog} before calling any of the @code{syslog} functions.
@item @b{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:

@table @code
@item gethostbyaddr
@item gethostbyname
@item inet_ntoa
(@code{inet_ntop} is thread-safe, though).
@end table
@end itemize

@subsection Network Statistics
There are a number of functions to print statistics gathered by the network stack.
These function are declared in @code{rtems/rtems_bsdnet.h}.
@table @code
@item rtems_bsdnet_show_if_stats
Display statistics gathered by network interfaces.

@item rtems_bsdnet_show_ip_stats
Display IP packet statistics.

@item rtems_bsdnet_show_icmp_stats
Display ICMP packet statistics.

@item rtems_bsdnet_show_tcp_stats
Display TCP packet statistics.

@item rtems_bsdnet_show_udp_stats
Display UDP packet statistics.

@item rtems_bsdnet_show_mbuf_stats
Display mbuf statistics.

@item rtems_bsdnet_show_inet_routes
Display the routing table.

@end table