URL https://opencores.org/ocsvn/openrisc/openrisc/trunk
Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [net-ns-dns-api.html] - Rev 510

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
>DNS</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="DNS for eCos and RedBoot"
HREF="net-ns-dns.html"><LINK
REL="PREVIOUS"
TITLE="DNS for eCos and RedBoot"
HREF="net-ns-dns.html"><LINK
REL="NEXT"
TITLE="Ethernet Device Drivers"
HREF="io-eth-drv-generic.html"></HEAD
><BODY
CLASS="CHAPTER"
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-ns-dns.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="io-eth-drv-generic.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="NET-NS-DNS-API">Chapter 45. DNS</H1
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="NET-NS-DNS-API1">DNS API</H1
><P
>The DNS client uses the normal BSD API for performing lookups:
<TT
CLASS="FUNCTION"
>gethostbyname()</TT
> and
<TT
CLASS="FUNCTION"
>gethostbyaddr()</TT
>.</P
><P
>There are a few restrictions:</P
><P
></P
><UL
><LI
><P
>Only IPv4 is supported, ie IPv6 addresses cannot be looked
up.</P
></LI
><LI
><P
>If the DNS server returns multiple authoritive records
for a host name, the hostent will only contain a record for the
first entry.</P
></LI
><LI
><P
>The code has been made thread safe. ie multiple threads
may call 
<TT
CLASS="FUNCTION"
>gethostbyname()</TT
>
 without causing problems to the hostent structure returned. What
is not safe is one thread using both 
<TT
CLASS="FUNCTION"
>gethostbyname()</TT
>
 and 
<TT
CLASS="FUNCTION"
>gethostbyaddr()</TT
>.
A call to one will destroy the results from the previous call
to the other function.</P
></LI
></UL
><P
>To initialise the DNS client the following function must be
called:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#include &lt;network.h&gt;
int cyg_dns_res_init(struct in_addr *dns_server)</PRE
></TD
></TR
></TABLE
><P
>where dns_server is the address of the DNS server
the client should query. On Error this function returns -1, otherwise
0 for success. If lookups are attemped before this function has
been called, they will fail and return NULL.</P
><P
>A default, hard coded, server may be specified in the CDL option
<TT
CLASS="LITERAL"
>CYGDAT_NS_DNS_DEFAULT_SERVER</TT
>. The use of this is
controlled by <TT
CLASS="LITERAL"
>CYGPKG_NS_DNS_DEFAULT</TT
>. If this is
enabled, <TT
CLASS="LITERAL"
>init_all_network_interfaces</TT
> will
initialize the resolver with the hard coded address. The DHCP client
or user code my override this address by calling
<TT
CLASS="LITERAL"
>cyg_dns_res_init</TT
> again. </P
><P
>The DNS client understands the concepts of the target being
in a domain. By default no domain will be used. Host name lookups
should be for fully qualified names. The domain name can be set
and retrieved using the functions:
<DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN14685"><P
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int getdomainname</CODE
>(char *name, size_t len);</CODE
></P
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int setdomainname</CODE
>(const char *name, size_t len);</CODE
></P
><P
></P
></DIV
></P
><P
>Alternatively, a hard coded domain name can be set using CDL.
The boolean <TT
CLASS="LITERAL"
>CYGPKG_NS_DNS_DOMAINNAME</TT
> enables this
and the domain name is taken from
<TT
CLASS="LITERAL"
>CYGPKG_NS_DNS_DOMAINNAME_NAME</TT
>.</P
><P
>Once set, the DNS client will first perform a lookup with the domain
name appended. If this fails it will then perform a second lookup
without the appended domain name. </P
></DIV
></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-ns-dns.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="io-eth-drv-generic.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>DNS for eCos and RedBoot</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="net-ns-dns.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Ethernet Device Drivers</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
Go to most recent revision | Compare with Previous | Blame | View Log
Browse

Tools

Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [net-ns-dns-api.html] - Rev 510
