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NAME="NET-SNMP-STARTING-THE-SNMP-AGENT">Starting the SNMP Agent</H1
><P
>A routine to instantiate and start the SNMP agent thread in the default
configuration is provided in
<TT
CLASS="FILENAME"
>PACKAGES/net/snmp/agent/VERSION/src/snmptask.c</TT
></P
><P
>It starts the snmpd thread at priority
<TT
CLASS="LITERAL"
>CYGPKG_NET_THREAD_PRIORITY+1</TT
>
by default, ie. one step less important than the TCP/IP stack service
thread.
It also statically creates and uses a very large stack of around 100
KiloBytes.
To use that convenience function, this code fragment may be copied (in
plain C).</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#ifdef CYGPKG_SNMPAGENT
{
                extern void cyg_net_snmp_init(void);
                cyg_net_snmp_init();
 
}
#endif</PRE
></TD
></TR
></TABLE
><P
>In case you need to perform initialization, for example setting up SNMPv3
security features, when the snmp agent starts and every time it restarts,
you can register a callback function by simply writing the global variable:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>externC void (*<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>snmpd_reinit_function</I
></SPAN
>)( void );</PRE
></TD
></TR
></TABLE
>
with a suitable function pointer.</P
><P
>The entry point to the SNMP agent is
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>externC void <TT
CLASS="FUNCTION"
>snmpd</TT
>( void (*<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>initfunc</I
></SPAN
>)( void ) );</PRE
></TD
></TR
></TABLE
>
so you can of course easily start it in a thread of your choice at another
priority instead if required, after performing whatever other
initialization your SNMP MIBs need.  A larger than default stacksize is
required.  The <TT
CLASS="LITERAL"
>initfunc</TT
> parameter is the callback
function mentioned above &#8212; a NULL parameter there is safe and
obviously means no callback is registered.</P
><P
>Note that if you call <TT
CLASS="LITERAL"
>snmpd();</TT
> yourself and do
<SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
> call <TT
CLASS="LITERAL"
>cyg_net_snmp_init();</TT
> then
that routine, global variable, and the default large stack will not be
used.  This is the recommended way control such features from your
application; create and start the thread yourself at the appropriate
moment.</P
><P
>Other APIs from the <TT
CLASS="LITERAL"
>snmpd</TT
> module are available,
specifically:
<TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>void <TT
CLASS="FUNCTION"
>SnmpdShutDown</TT
>(int <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>a</I
></SPAN
>);</PRE
></TD
></TR
></TABLE
>
which causes the <TT
CLASS="LITERAL"
>snmpd</TT
> to restart itself &#8212;
including the callback to your init function &#8212; as soon as possible.</P
><P
>The parameter <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>a</I
></SPAN
> is ignored.  It is there because in
<TT
CLASS="LITERAL"
>snmpd</TT
>'s &#8220;natural environment&#8221; this routine
is a <TT
CLASS="LITERAL"
>UNIX</TT
> signal handler.</P
><P
>The helper functions in the network stack for managing
<TT
CLASS="LITERAL"
>DHCP</TT
>
leases will call <TT
CLASS="FUNCTION"
>SnmpdShutDown()</TT
>
when necessary, for example if network interfaces go down and/or come up
again.</P
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>

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			`>Starting the SNMP Agent</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="SNMP for eCos"`
23			`HREF="net-snmp-ecos-port.html"><LINK`
24			`REL="PREVIOUS"`
25			`TITLE="Changes to eCos sources"`
26			`HREF="net-snmp-ecos-changes.html"><LINK`
27			`REL="NEXT"`
28			`TITLE="Configuring eCos"`
29			`HREF="net-snmp-configuring-ecos.html"></HEAD`
30			`><BODY`
31			`CLASS="SECT1"`
32			`BGCOLOR="#FFFFFF"`
33			`TEXT="#000000"`
34			`LINK="#0000FF"`
35			`VLINK="#840084"`
36			`ALINK="#0000FF"`
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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-snmp-ecos-changes.html"`
58			`ACCESSKEY="P"`
59			`>Prev</A`
60			`></TD`
61			`><TD`
62			`WIDTH="80%"`
63			`ALIGN="center"`
64			`VALIGN="bottom"`
65			`>Chapter 47. SNMP for <SPAN`
66			`CLASS="emphasis"`
67			`><I`
68			`CLASS="EMPHASIS"`
69			`>eCos</I`
70			`></SPAN`
71			`></TD`
72			`><TD`
73			`WIDTH="10%"`
74			`ALIGN="right"`
75			`VALIGN="bottom"`
76			`><A`
77			`HREF="net-snmp-configuring-ecos.html"`
78			`ACCESSKEY="N"`
79			`>Next</A`
80			`></TD`
81			`></TR`
82			`></TABLE`
83			`><HR`
84			`ALIGN="LEFT"`
85			`WIDTH="100%"></DIV`
86			`><DIV`
87			`CLASS="SECT1"`
88			`><H1`
89			`CLASS="SECT1"`
90			`><A`
91			`NAME="NET-SNMP-STARTING-THE-SNMP-AGENT">Starting the SNMP Agent</H1`
92			`><P`
93			`>A routine to instantiate and start the SNMP agent thread in the default`
94			`configuration is provided in`
95			`<TT`
96			`CLASS="FILENAME"`
97			`>PACKAGES/net/snmp/agent/VERSION/src/snmptask.c</TT`
98			`></P`
99			`><P`
100			`>It starts the snmpd thread at priority`
101			`<TT`
102			`CLASS="LITERAL"`
103			`>CYGPKG_NET_THREAD_PRIORITY+1</TT`
104			`>`
105			`by default, ie. one step less important than the TCP/IP stack service`
106			`thread.`
107			`It also statically creates and uses a very large stack of around 100`
108			`KiloBytes.`
109			`To use that convenience function, this code fragment may be copied (in`
110			`plain C).</P`
111			`><TABLE`
112			`BORDER="5"`
113			`BGCOLOR="#E0E0F0"`
114			`WIDTH="70%"`
115			`><TR`
116			`><TD`
117			`><PRE`
118			`CLASS="PROGRAMLISTING"`
119			`>#ifdef CYGPKG_SNMPAGENT`
120			`{`
121			`extern void cyg_net_snmp_init(void);`
122			`cyg_net_snmp_init();`
123
124			`}`
125			`#endif</PRE`
126			`></TD`
127			`></TR`
128			`></TABLE`
129			`><P`
130			`>In case you need to perform initialization, for example setting up SNMPv3`
131			`security features, when the snmp agent starts and every time it restarts,`
132			`you can register a callback function by simply writing the global variable:`
133			`<TABLE`
134			`BORDER="5"`
135			`BGCOLOR="#E0E0F0"`
136			`WIDTH="70%"`
137			`><TR`
138			`><TD`
139			`><PRE`
140			`CLASS="PROGRAMLISTING"`
141			`>externC void (*<SPAN`
142			`CLASS="emphasis"`
143			`><I`
144			`CLASS="EMPHASIS"`
145			`>snmpd_reinit_function</I`
146			`></SPAN`
147			`>)( void );</PRE`
148			`></TD`
149			`></TR`
150			`></TABLE`
151			`>`
152			`with a suitable function pointer.</P`
153			`><P`
154			`>The entry point to the SNMP agent is`
155			`<TABLE`
156			`BORDER="5"`
157			`BGCOLOR="#E0E0F0"`
158			`WIDTH="70%"`
159			`><TR`
160			`><TD`
161			`><PRE`
162			`CLASS="PROGRAMLISTING"`
163			`>externC void <TT`
164			`CLASS="FUNCTION"`
165			`>snmpd</TT`
166			`>( void (*<SPAN`
167			`CLASS="emphasis"`
168			`><I`
169			`CLASS="EMPHASIS"`
170			`>initfunc</I`
171			`></SPAN`
172			`>)( void ) );</PRE`
173			`></TD`
174			`></TR`
175			`></TABLE`
176			`>`
177			`so you can of course easily start it in a thread of your choice at another`
178			`priority instead if required, after performing whatever other`
179			`initialization your SNMP MIBs need. A larger than default stacksize is`
180			`required. The <TT`
181			`CLASS="LITERAL"`
182			`>initfunc</TT`
183			`> parameter is the callback`
184			`function mentioned above — a NULL parameter there is safe and`
185			`obviously means no callback is registered.</P`
186			`><P`
187			`>Note that if you call <TT`
188			`CLASS="LITERAL"`
189			`>snmpd();</TT`
190			`> yourself and do`
191			`<SPAN`
192			`CLASS="emphasis"`
193			`><I`
194			`CLASS="EMPHASIS"`
195			`>not</I`
196			`></SPAN`
197			`> call <TT`
198			`CLASS="LITERAL"`
199			`>cyg_net_snmp_init();</TT`
200			`> then`
201			`that routine, global variable, and the default large stack will not be`
202			`used. This is the recommended way control such features from your`
203			`application; create and start the thread yourself at the appropriate`
204			`moment.</P`
205			`><P`
206			`>Other APIs from the <TT`
207			`CLASS="LITERAL"`
208			`>snmpd</TT`
209			`> module are available,`
210			`specifically:`
211			`<TABLE`
212			`BORDER="5"`
213			`BGCOLOR="#E0E0F0"`
214			`WIDTH="70%"`
215			`><TR`
216			`><TD`
217			`><PRE`
218			`CLASS="PROGRAMLISTING"`
219			`>void <TT`
220			`CLASS="FUNCTION"`
221			`>SnmpdShutDown</TT`
222			`>(int <SPAN`
223			`CLASS="emphasis"`
224			`><I`
225			`CLASS="EMPHASIS"`
226			`>a</I`
227			`></SPAN`
228			`>);</PRE`
229			`></TD`
230			`></TR`
231			`></TABLE`
232			`>`
233			`which causes the <TT`
234			`CLASS="LITERAL"`
235			`>snmpd</TT`
236			`> to restart itself —`
237			`including the callback to your init function — as soon as possible.</P`
238			`><P`
239			`>The parameter <SPAN`
240			`CLASS="emphasis"`
241			`><I`
242			`CLASS="EMPHASIS"`
243			`>a</I`
244			`></SPAN`
245			`> is ignored. It is there because in`
246			`<TT`
247			`CLASS="LITERAL"`
248			`>snmpd</TT`
249			`>'s “natural environment” this routine`
250			`is a <TT`
251			`CLASS="LITERAL"`
252			`>UNIX</TT`
253			`> signal handler.</P`
254			`><P`
255			`>The helper functions in the network stack for managing`
256			`<TT`
257			`CLASS="LITERAL"`
258			`>DHCP</TT`
259			`>`
260			`leases will call <TT`
261			`CLASS="FUNCTION"`
262			`>SnmpdShutDown()</TT`
263			`>`
264			`when necessary, for example if network interfaces go down and/or come up`
265			`again.</P`
266			`></DIV`
267			`><DIV`
268			`CLASS="NAVFOOTER"`
269			`><HR`
270			`ALIGN="LEFT"`
271			`WIDTH="100%"><TABLE`
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293			`ACCESSKEY="H"`
294			`>Home</A`
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297			`WIDTH="33%"`
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309			`ALIGN="left"`
310			`VALIGN="top"`
311			`>Changes to eCos sources</TD`
312			`><TD`
313			`WIDTH="34%"`
314			`ALIGN="center"`
315			`VALIGN="top"`
316			`><A`
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319			`>Up</A`
320			`></TD`
321			`><TD`
322			`WIDTH="33%"`
323			`ALIGN="right"`
324			`VALIGN="top"`
325			`>Configuring eCos</TD`
326			`></TR`
327			`></TABLE`
328			`></DIV`
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330			`></HTML`
331			`>`

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