URL
https://opencores.org/ocsvn/openrisc/openrisc/trunk
Subversion Repositories openrisc
[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [net-common-dhcp.html] - Rev 842
Go to most recent revision | Compare with Previous | Blame | View Log
<!-- Copyright (C) 2003 Red Hat, Inc. -->
<!-- This material may be distributed only subject to the terms -->
<!-- and conditions set forth in the Open Publication License, v1.0 -->
<!-- or later (the latest version is presently available at -->
<!-- http://www.opencontent.org/openpub/). -->
<!-- Distribution of the work or derivative of the work in any -->
<!-- standard (paper) book form is prohibited unless prior -->
<!-- permission is obtained from the copyright holder. -->
<HTML
><HEAD
><TITLE
>DHCP</TITLE
><meta name="MSSmartTagsPreventParsing" content="TRUE">
<META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="eCos Reference Manual"
HREF="ecos-ref.html"><LINK
REL="UP"
TITLE="Support Features"
HREF="net-common-support.html"><LINK
REL="PREVIOUS"
TITLE="Support Features"
HREF="net-common-support.html"><LINK
REL="NEXT"
TITLE="TCP/IP Library Reference"
HREF="tcpip-library-reference.html"></HEAD
><BODY
CLASS="SECT1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>eCos Reference Manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="net-common-support.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 37. Support Features</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="tcpip-library-reference.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="NET-COMMON-DHCP">DHCP</H1
><P
>This API publishes a routine to maintain DHCP state, and a
semaphore that is signalled when a lease requires attention: this
is your clue to call the aforementioned routine.</P
><P
>The intent with this API is that a simple DHCP client thread,
which maintains the state of the interfaces, can go as follows:
(after <TT
CLASS="FUNCTION"
>init_all_network_interfaces()</TT
> is
called from elsewhere)</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>while ( 1 ) {
while ( 1 ) {
cyg_semaphore_wait( &dhcp_needs_attention );
if ( ! dhcp_bind() ) // a lease expired
break; // If we need to re-bind
}
dhcp_halt(); // tear everything down
init_all_network_interfaces(); // re-initialize
}</PRE
></TD
></TR
></TABLE
><P
>and if the application does not want to suffer the overhead
of a separate thread and its stack for this, this functionality
can be placed in the app’s server loop in an obvious fashion.
That is the goal of breaking out these internal elements. For example,
some server might be arranged to poll DHCP from time to time like
this:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>while ( 1 ) {
init_all_network_interfaces();
open-my-listen-sockets();
while ( 1 ) {
serve-one-request();
// sleeps if no connections, but not forever;
// so this loop is polled a few times a minute...
if ( cyg_semaphore_trywait( &dhcp_needs_attention )) {
if ( ! dhcp_bind() ) {
close-my-listen-sockets();
dhcp_halt();
break;
}
}
}
}</PRE
></TD
></TR
></TABLE
><P
>If the configuration option CYGOPT_NET_DHCP_DHCP_THREAD
is defined, then eCos provides a thread as described initially.
Independent of this option, initialization of the interfaces still
occurs in <TT
CLASS="FUNCTION"
>init_all_network_interfaces()</TT
> and
your startup code can call that. It will start the DHCP management
thread if configured. If a lease fails to be renewed, the management
thread will shut down all interfaces and attempt to initialize all
the interfaces again from scratch. This may cause chaos in the
app, which is why managing the DHCP state in an application aware
thread is actually better, just far less convenient for testing.</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="net-common-support.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="ecos-ref.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="tcpip-library-reference.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Support Features</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="net-common-support.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>TCP/IP Library Reference</TD
></TR
></TABLE
></DIV
></BODY
></HTML
> Go to most recent revision | Compare with Previous | Blame | View Log