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<!-- 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"
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ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
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><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%"
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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
 
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
>

Line No.	Rev	Author	Line
1	28	unneback	`<!-- Copyright (C) 2003 Red Hat, Inc. -->`
2			`<!-- This material may be distributed only subject to the terms -->`
3			`<!-- and conditions set forth in the Open Publication License, v1.0 -->`
4			`<!-- or later (the latest version is presently available at -->`
5			`<!-- http://www.opencontent.org/openpub/). -->`
6			`<!-- Distribution of the work or derivative of the work in any -->`
7			`<!-- standard (paper) book form is prohibited unless prior -->`
8			`<!-- permission is obtained from the copyright holder. -->`
9			`<HTML`
10			`><HEAD`
11			`><TITLE`
12			`>DNS</TITLE`
13			`><meta name="MSSmartTagsPreventParsing" content="TRUE">`
14			`<META`
15			`NAME="GENERATOR"`
16			`CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+`
17			`"><LINK`
18			`REL="HOME"`
19			`TITLE="eCos Reference Manual"`
20			`HREF="ecos-ref.html"><LINK`
21			`REL="UP"`
22			`TITLE="DNS for eCos and RedBoot"`
23			`HREF="net-ns-dns.html"><LINK`
24			`REL="PREVIOUS"`
25			`TITLE="DNS for eCos and RedBoot"`
26			`HREF="net-ns-dns.html"><LINK`
27			`REL="NEXT"`
28			`TITLE="Ethernet Device Drivers"`
29			`HREF="io-eth-drv-generic.html"></HEAD`
30			`><BODY`
31			`CLASS="CHAPTER"`
32			`BGCOLOR="#FFFFFF"`
33			`TEXT="#000000"`
34			`LINK="#0000FF"`
35			`VLINK="#840084"`
36			`ALINK="#0000FF"`
37			`><DIV`
38			`CLASS="NAVHEADER"`
39			`><TABLE`
40			`SUMMARY="Header navigation table"`
41			`WIDTH="100%"`
42			`BORDER="0"`
43			`CELLPADDING="0"`
44			`CELLSPACING="0"`
45			`><TR`
46			`><TH`
47			`COLSPAN="3"`
48			`ALIGN="center"`
49			`>eCos Reference Manual</TH`
50			`></TR`
51			`><TR`
52			`><TD`
53			`WIDTH="10%"`
54			`ALIGN="left"`
55			`VALIGN="bottom"`
56			`><A`
57			`HREF="net-ns-dns.html"`
58			`ACCESSKEY="P"`
59			`>Prev</A`
60			`></TD`
61			`><TD`
62			`WIDTH="80%"`
63			`ALIGN="center"`
64			`VALIGN="bottom"`
65			`></TD`
66			`><TD`
67			`WIDTH="10%"`
68			`ALIGN="right"`
69			`VALIGN="bottom"`
70			`><A`
71			`HREF="io-eth-drv-generic.html"`
72			`ACCESSKEY="N"`
73			`>Next</A`
74			`></TD`
75			`></TR`
76			`></TABLE`
77			`><HR`
78			`ALIGN="LEFT"`
79			`WIDTH="100%"></DIV`
80			`><DIV`
81			`CLASS="CHAPTER"`
82			`><H1`
83			`><A`
84			`NAME="NET-NS-DNS-API">Chapter 45. DNS</H1`
85			`><DIV`
86			`CLASS="SECT1"`
87			`><H1`
88			`CLASS="SECT1"`
89			`><A`
90			`NAME="NET-NS-DNS-API1">DNS API</H1`
91			`><P`
92			`>The DNS client uses the normal BSD API for performing lookups:`
93			`<TT`
94			`CLASS="FUNCTION"`
95			`>gethostbyname()</TT`
96			`> and`
97			`<TT`
98			`CLASS="FUNCTION"`
99			`>gethostbyaddr()</TT`
100			`>.</P`
101			`><P`
102			`>There are a few restrictions:</P`
103			`><P`
104			`></P`
105			`><UL`
106			`><LI`
107			`><P`
108			`>Only IPv4 is supported, ie IPv6 addresses cannot be looked`
109			`up.</P`
110			`></LI`
111			`><LI`
112			`><P`
113			`>If the DNS server returns multiple authoritive records`
114			`for a host name, the hostent will only contain a record for the`
115			`first entry.</P`
116			`></LI`
117			`><LI`
118			`><P`
119			`>The code has been made thread safe. ie multiple threads`
120			`may call`
121			`<TT`
122			`CLASS="FUNCTION"`
123			`>gethostbyname()</TT`
124			`>`
125			`without causing problems to the hostent structure returned. What`
126			`is not safe is one thread using both`
127			`<TT`
128			`CLASS="FUNCTION"`
129			`>gethostbyname()</TT`
130			`>`
131			`and`
132			`<TT`
133			`CLASS="FUNCTION"`
134			`>gethostbyaddr()</TT`
135			`>.`
136			`A call to one will destroy the results from the previous call`
137			`to the other function.</P`
138			`></LI`
139			`></UL`
140			`><P`
141			`>To initialise the DNS client the following function must be`
142			`called:</P`
143			`><TABLE`
144			`BORDER="5"`
145			`BGCOLOR="#E0E0F0"`
146			`WIDTH="70%"`
147			`><TR`
148			`><TD`
149			`><PRE`
150			`CLASS="PROGRAMLISTING"`
151			`>#include <network.h>`
152			`int cyg_dns_res_init(struct in_addr *dns_server)</PRE`
153			`></TD`
154			`></TR`
155			`></TABLE`
156			`><P`
157			`>where dns_server is the address of the DNS server`
158			`the client should query. On Error this function returns -1, otherwise`
159
160			`been called, they will fail and return NULL.</P`
161			`><P`
162			`>A default, hard coded, server may be specified in the CDL option`
163			`<TT`
164			`CLASS="LITERAL"`
165			`>CYGDAT_NS_DNS_DEFAULT_SERVER</TT`
166			`>. The use of this is`
167			`controlled by <TT`
168			`CLASS="LITERAL"`
169			`>CYGPKG_NS_DNS_DEFAULT</TT`
170			`>. If this is`
171			`enabled, <TT`
172			`CLASS="LITERAL"`
173			`>init_all_network_interfaces</TT`
174			`> will`
175			`initialize the resolver with the hard coded address. The DHCP client`
176			`or user code my override this address by calling`
177			`<TT`
178			`CLASS="LITERAL"`
179			`>cyg_dns_res_init</TT`
180			`> again. </P`
181			`><P`
182			`>The DNS client understands the concepts of the target being`
183			`in a domain. By default no domain will be used. Host name lookups`
184			`should be for fully qualified names. The domain name can be set`
185			`and retrieved using the functions:`
186			`<DIV`
187			`CLASS="FUNCSYNOPSIS"`
188			`><A`
189			`NAME="AEN14685"><P`
190			`></P`
191			`><P`
192			`><CODE`
193			`><CODE`
194			`CLASS="FUNCDEF"`
195			`>int getdomainname</CODE`
196			`>(char *name, size_t len);</CODE`
197			`></P`
198			`><P`
199			`><CODE`
200			`><CODE`
201			`CLASS="FUNCDEF"`
202			`>int setdomainname</CODE`
203			`>(const char *name, size_t len);</CODE`
204			`></P`
205			`><P`
206			`></P`
207			`></DIV`
208			`></P`
209			`><P`
210			`>Alternatively, a hard coded domain name can be set using CDL.`
211			`The boolean <TT`
212			`CLASS="LITERAL"`
213			`>CYGPKG_NS_DNS_DOMAINNAME</TT`
214			`> enables this`
215			`and the domain name is taken from`
216			`<TT`
217			`CLASS="LITERAL"`
218			`>CYGPKG_NS_DNS_DOMAINNAME_NAME</TT`
219			`>.</P`
220			`><P`
221			`>Once set, the DNS client will first perform a lookup with the domain`
222			`name appended. If this fails it will then perform a second lookup`
223			`without the appended domain name. </P`
224			`></DIV`
225			`></DIV`
226			`><DIV`
227			`CLASS="NAVFOOTER"`
228			`><HR`
229			`ALIGN="LEFT"`
230			`WIDTH="100%"><TABLE`
231			`SUMMARY="Footer navigation table"`
232			`WIDTH="100%"`
233			`BORDER="0"`
234			`CELLPADDING="0"`
235			`CELLSPACING="0"`
236			`><TR`
237			`><TD`
238			`WIDTH="33%"`
239			`ALIGN="left"`
240			`VALIGN="top"`
241			`><A`
242			`HREF="net-ns-dns.html"`
243			`ACCESSKEY="P"`
244			`>Prev</A`
245			`></TD`
246			`><TD`
247			`WIDTH="34%"`
248			`ALIGN="center"`
249			`VALIGN="top"`
250			`><A`
251			`HREF="ecos-ref.html"`
252			`ACCESSKEY="H"`
253			`>Home</A`
254			`></TD`
255			`><TD`
256			`WIDTH="33%"`
257			`ALIGN="right"`
258			`VALIGN="top"`
259			`><A`
260			`HREF="io-eth-drv-generic.html"`
261			`ACCESSKEY="N"`
262			`>Next</A`
263			`></TD`
264			`></TR`
265			`><TR`
266			`><TD`
267			`WIDTH="33%"`
268			`ALIGN="left"`
269			`VALIGN="top"`
270			`>DNS for eCos and RedBoot</TD`
271			`><TD`
272			`WIDTH="34%"`
273			`ALIGN="center"`
274			`VALIGN="top"`
275			`><A`
276			`HREF="net-ns-dns.html"`
277			`ACCESSKEY="U"`
278			`>Up</A`
279			`></TD`
280			`><TD`
281			`WIDTH="33%"`
282			`ALIGN="right"`
283			`VALIGN="top"`
284			`>Ethernet Device Drivers</TD`
285			`></TR`
286			`></TABLE`
287			`></DIV`
288			`></BODY`
289			`></HTML`
290			`>`

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[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [net-ns-dns-api.html] - Blame information for rev 575