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          TCP/IP Networking for eCos

          now provides a complete

          TCP/IP networking stack, which is derived from a recent

          stable release of OpenBSD. The networking support is

          fully featured and well tested within the eCos environment.

Since this networking package is based on BSD code, it is

very complete and robust.  The eCos implementation includes support

for the following protocols:   

IPv4

UDP

TCP

ICMP

raw packet interface

These additional features are also present in the package,

        but are not supported:

Berkeley Packet Filter   

Multi-cast and uni-cast support, including multi-casting

routing   

IPv6 

This document describes how to get started with the OpenBSD

TCP/IP network stack. 

A number of ethernet devices may be supported. The default configuration

supports two instances of the interface by default,

and you will need to write your own driver instantiation code,

and supplemental startup and initialization code,

if you should add additional ones.

The target for your board will normally be supplied with an

ethernet driver, in which case including the network stack and

generic ethernet driver package to your build will automatically

enable usage of the ethernet device driver.

If your target is not supplied with an ethernet

driver, you will need to use loopback (see

).

Using the Build->Packages dialog,

add the packages “Networking”,

“OpenBSD TCP/IP Stack”

and “Common Ethernet Support”

to your configuration.  Their package names

are CYGPKG_NET, CYGPKG_NET_OPENBSD_STACK and CYGPKG_NET_ETH_DRIVERS

respectively.

A short-cut way to do this is by

using the “net” template

if it is available for your platform.

The platform-specific ethernet device driver for your platform

will be added as part of the target selection (in the

Build->Templates “Hardware” item),

along with the

PCI I/O subsystem (if relevent) and the appropriate serial device driver.

For example, the PowerPC MBX target selection adds the package

PKG_NET_QUICC_ETH_DRIVERS,

and the Cirrus Logic EDB7xxx target selection adds the package

CYGPKG_NET_EDB7XXX_ETH_DRIVERS.

After this, eCos and its tests can be built exactly as usual.

By default, most of the network tests are not built.  This

is because some of them require manual intervention, i.e. they are

to be run “by hand”, and are not suitable for

automated testing.  To build the full set of network tests, set

the configuration option CYGPKG_NET_BUILD_TESTS “Build

networking tests (demo programs)” within “Networking

support build options”.

The APIs for the standard networking calls such as

socket(), recv() and so on, are

in header files relative to the top-level

include directory, within the standard subdirectories as conventionally

found in /usr/include.  For example:

 install/include/arpa/tftp.h

 install/include/netinet/tcpip.h

 install/include/sys/socket.h

 install/include/sys/socketvar.h

 install/include/sys/sockio.h

network.h at the top level

defines various extensions, for example the API

init_all_network_interfaces(void)

described

above.  We advise including network.h whether

you use these features or not.

In general, using the networking code may require definition

of two symbols: _KERNEL and __ECOS.  _KERNEL

is not normally required; __ECOS is normally required.

So add this to your compile lines for files which use the network

stack:

        -D__ECOS

To expand a little, it’s like this because this is

a port of a standard distribution external to Red Hat.  One goal

is to perturb the sources as little as possible, so that upgrading

and maintenance from the external distribution is simplified.  The __ECOS

symbol marks out Red Hat’s additions in making the port.

The _KERNEL symbol is traditional UNIX practice: it distinguishes

a compilation which is to be linked into the kernel from one which

is part of an application.  eCos applications are fully linked,

so this distinction does not apply.  _KERNEL can however

be used to control the visibility of the internals of the stack,

so depending on what features your application uses, it may or may

not be necessary.

The include file network.h undefines _KERNEL

unconditionally, to provide an application-like compilation environment.

If you were writing code which, for example,

enumerates the stack’s internal

structures, that is a kernel-like compilation environment, so you

would need to define _KERNEL (in addition to __ECOS)

and avoid including network.h.

The network stack supports an extension to the standard select

semantics which allows all threads that are waiting to be restarted

even if the select conditions are not satisfied.

The standard select() API:  

int

select(int nfd,

       fd_set *in, fd_set *out, fd_set *ex,

       struct timeval *tv); 

does not support the restart.

The additional API:  

int

cyg_select_with_abort(int nfd,

       fd_set *in, fd_set *out, fd_set *ex,

       struct timeval *tv)

behaves exactly as select() with the additional feature that

a call to

void cyg_select_abort(void)

will cause all threads waiting in any

cyg_select_with_abort() call

to cease waiting and continue execution.