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<PART id="tcpip-freebsd">
<TITLE>FreeBSD TCP/IP Stack port for eCos</TITLE>
<PARTINTRO>
<PARA>    <productname>TCP/IP Networking for eCos</productname>
          now provides a complete
          TCP/IP networking stack, 
based on a snapshot of the FreeBSD code, released by the
KAME project.
The networking support is
          fully featured and well tested within the eCos environment.
        </PARA>
</PARTINTRO>

<CHAPTER id="tcpip-freebsd-networking-stack-features">
<TITLE>Networking Stack Features</TITLE>
<PARA>Since this networking package is based on BSD code, it is
very complete and robust.  The eCos implementation includes support
for the following protocols:   </PARA>
<itemizedlist>
<LISTITEM><PARA>IPv4</para></listitem>
<LISTITEM><PARA>UDP</para></listitem>
<LISTITEM><PARA>TCP</para></listitem>
<LISTITEM><PARA>ICMP</para></listitem>
<LISTITEM><PARA>raw packet interface</para></listitem>
<LISTITEM><PARA>Multi-cast addressing</para></listitem>
<LISTITEM><PARA>IPv6 (including UDP, ICP, ICMP)</para></listitem>
</itemizedlist>
<PARA>These additional features are also present in the package,
        but are not supported:</PARA>
<itemizedlist>
<LISTITEM><PARA>Berkeley Packet Filter   </PARA></LISTITEM>
<LISTITEM><PARA>Uni-cast support   </PARA></LISTITEM>
<LISTITEM><PARA>Multi-cast routing   </PARA></LISTITEM>
</itemizedlist>
</CHAPTER>
<CHAPTER id="tcpip-freebsd-stack-port">
<TITLE>Freebsd TCP/IP stack port</TITLE>
<PARA>This document describes how to get started with the Freebsd
TCP/IP network stack. </PARA>
<SECT1 id="tcpip-freebsd-tcpip-targets">
<TITLE>Targets</TITLE>
<PARA>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.</PARA>
<PARA>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
<xref linkend="net-common-loopback-tests">).</PARA>
</SECT1>
<SECT1 id="tcpip-freebsd-building-the-network-stack">
<TITLE><!--<conditionaltext>-->Building the Network Stack</TITLE>
<PARA>Using the <EMPHASIS>Build-&gt;Packages</EMPHASIS> dialog,
add the packages &ldquo;Networking&rdquo;,
&ldquo;Freebsd TCP/IP Stack&rdquo;
and &ldquo;Common Ethernet Support&rdquo;
to your configuration.  Their package names
are CYGPKG_NET, CYGPKG_NET_FREEBSD_STACK and CYGPKG_NET_ETH_DRIVERS
respectively.</PARA>
<para>A short-cut way to do this is by
using the &ldquo;net&rdquo; <emphasis>template</emphasis>
if it is available for your platform.</para>
<PARA>The platform-specific ethernet device driver for your platform
will be added as part of the target selection (in the
<EMPHASIS>Build-&gt;Templates</EMPHASIS> &ldquo;Hardware&rdquo; item),
along with the 
PCI I/O subsystem (if relevent) and the appropriate serial device driver.
</para><para>
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.</PARA>
<NOTE>
<PARA>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 &ldquo;by hand&rdquo;, and are not suitable for
automated testing.  To build the full set of network tests, set
the configuration option CYGPKG_NET_BUILD_TESTS &ldquo;Build
networking tests (demo programs)&rdquo; within &ldquo;Networking
support build options&rdquo;.</PARA>
</NOTE>
</SECT1>
</CHAPTER>
<CHAPTER id="tcpip-freebsd-tcpip-apis">
<TITLE>APIs</TITLE>
<SECT1 id="tcpip-freebsd-standard-networking-api">
<TITLE>Standard networking</TITLE>
<PARA>The APIs for the standard networking calls such as
<FUNCTION>socket()</FUNCTION>, <FUNCTION>recv()</FUNCTION> and so on, are
in header files relative to the top-level
include directory, within the standard subdirectories as conventionally
found in <FILENAME>/usr/include</FILENAME>.  For example:
<PROGRAMLISTING>
 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
</PROGRAMLISTING>
</PARA>
<PARA>
<filename>network.h</filename> at the top level
defines various extensions, for example the API
<function>init_all_network_interfaces(void)</function>
described
above.  We advise including <filename>network.h</filename> whether
you use these features or not.</PARA>
<PARA>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:</PARA>
<PROGRAMLISTING>        -D__ECOS</PROGRAMLISTING>
<PARA>To expand a little, it&rsquo;s like this because this is
a port of a standard distribution external to eCos.  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 the eCos 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.</PARA>
<PARA>The include file <filename>network.h</filename> undefines _KERNEL
unconditionally, to provide an application-like compilation environment.
If you were writing code which, for example,
enumerates the stack&rsquo;s internal
structures, that is a kernel-like compilation environment, so you
would need to define _KERNEL (in addition to __ECOS)
and avoid including <filename>network.h</filename>.</PARA>
</SECT1>
<SECT1 id="tcpip-freebsd-enhanced-select">
<TITLE>Enhanced Select()</TITLE>
<PARA>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.</PARA>
<PARA>The standard select() API:  </PARA>
<PROGRAMLISTING>int  
<function>select</function>(int nfd,
       fd_set &ast;in, fd_set &ast;out, fd_set &ast;ex,
       struct timeval &ast;tv); </PROGRAMLISTING>
<PARA>does not support the restart.</PARA>
<PARA>The additional API:  </PARA>
<PROGRAMLISTING>int  
<function>cyg_select_with_abort</function>(int nfd,
       fd_set &ast;in, fd_set &ast;out, fd_set &ast;ex,
       struct timeval &ast;tv)
</PROGRAMLISTING>
<PARA>behaves exactly as select() with the additional feature that
a call to</PARA>
<PROGRAMLISTING>
void <function>cyg_select_abort</function>(void)
</PROGRAMLISTING>
<PARA>will cause all threads waiting in any
<function>cyg_select_with_abort()</function> call
to cease waiting and continue execution.</PARA>
</SECT1>

<SECT1 id="tcpip-freebsd-disabling-ipv6-at-runtime">
<TITLE>Disabling IPv6 Support at Runtime</TITLE>
<PARA>
The FreeBSD stack starts up with IPv4 support in an essentially
"disabled" state.  It requires the application to take positive actions
to assign IPv4 address and routes before the interfaces will respond
to packets from the outside world.
</PARA>
<PARA>
This is not true of IPv6 support.  If IPv6 support was enabled in the
eCos build, the stack will start up with link-local addresses
assigned and interfaces listening to certain multicast addresses.  The
stack will not only respond to IPv6 packets, it will spontaneously
send IPv6 packets without actions from application code.
</PARA>
<PARA>
If an eCos application wishes to disable IPv6 support at runtime, the
decision has to be made very early in the boot process and actions
taken to prevent the invocation of IPv6 startup code in the network
stack.  This involves two rather obscure "tricks":
<ITEMIZEDLIST>
<LISTITEM><PARA>
Using a dummy device driver's "init" hook as a place to execute some
code early in the startup process
</PARA></LISTITEM>
<LISTITEM><PARA> Monkey-patching the network stack's table of
initializers by looping through it and checking the function pointers
against certain globally visible symbols and replacing the two
IPv6-specific function pointers with pointers to a "noop" function.
</PARA></LISTITEM>
</ITEMIZEDLIST>
</PARA>
<PARA>
The code listing below shows an example of disabling IPv6 support at
runtime if the global variable we_want_to_disable_ipv6 is non-zero.
The assumption is that some code in the HAL initialization or
somewhere else has made the decision whether or not to disable IPv6
support and set that variable accordingly.
</PARA>
<PROGRAMLISTING>
// Sample code showing a method of disabling IPv6 support at runtime

// Do-nothing function we can patch into the network stack's init table
// when we want to disable one of the entries
static void
init_noop(void *dummy)
{
}

// Function that loops through the network stack's init table and
// disables the two IPv6 entries
static void
disable_ipv6(void)
{
    extern struct init_tab_entry __NET_INIT_TAB__[],
                    __NET_INIT_TAB_END__;
    struct init_tab_entry *init_entry;
    extern void     cyg_net_add_domain(void *);
    extern void     ip6_init2(void *);
    extern char     inet6domain[];

    for (init_entry = __NET_INIT_TAB__; init_entry != &__NET_INIT_TAB_END__;
         init_entry++)
        if ((init_entry->fun == ip6_init2)
            || (init_entry->fun == cyg_net_add_domain
                && init_entry->data == (void *)inet6domain))
            init_entry->fun = init_noop;
}

// Function called early in the inintialization process via a dummy
// device table entry
static bool
early_init(struct cyg_devtab_entry *tab)
{
    if (we_want_to_disable_ipv6)
        disable_ipv6();
    return 0;
}

// Dummy device driver table entry that will call the above early_init()
// function during the startup process
DEVTAB_ENTRY(device_master_early_init,
             "neveruse",
             NULL,
             NULL,
             early_init,
             NULL,
             NULL
    );
</PROGRAMLISTING>
</SECT1>
</CHAPTER>
</PART>