design.sgml

gxsnmp SNMP MANAGER 的实现

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<book id="gxsnmp-design">
  <bookinfo>
    <title>GXSNMP Design Specifications</title>
    <releaseinfo>April 10, 1999</releaseinfo>
    <authorgroup>
    <author>
      <firstname>Jochen</firstname>
      <surname>Friedrich</surname>
      <affiliation>
       <address><email>[e-mail]</email></address>
      </affiliation>
    </author>
    <author>
      <firstname>Gregory</firstname>
      <surname>McLean</surname>
      <affiliation>
        <address><email>[e-mail]</email></address>
      </affiliation>
    </author>
      <author>
        <firstname>John</firstname>
        <surname>Schulien</surname>
        <affiliation>
          <address>
             <email>[e-mail]</email>
          </address>
        </affiliation>
      </author>
    <author>
      <firstname>Craig</firstname>
      <surname>Small</surname>
      <affiliation>
        <address><email>[e-mail]</email></address>
      </affiliation>
    </author>
   </authorgroup>
    <legalnotice>
      <para>This documentation is free software; you can redistribute
        it and/or modify it under the terms of the GNU General Public
        License as published by the Free Software Foundation; either
        version 2 of the License, or (at your option) any later
        version.</para>

      <para>This program is distributed in the hope that it will be
        useful, but WITHOUT ANY WARRANTY; without even the implied
        warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
        See the GNU General Public License for more details.</para>

      <para>You should have received a copy of the GNU General Public
        License along with this program; if not, write to the Free
        Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
        MA 02111-1307 USA</para>

      <para>For more details see the file COPYING in the source
        distribution of GXSNMP.</para>
     </legalnotice>

  </bookinfo>

  <chapter id="internal-design">
    <title>GXSNMP Internal Design</title>
    <sect1>
      <title>Design Goals</title>
  
        <para>
          GXSNMP is a network management application that is intended to
          grow in the future to provide all of the features one would expect
          to find in the commerical offerings.
        </para>
     </sect1>
    
     <sect1>
       <title>Basic organization</title>
       <para>
         FIXME!
       </para>
     </sect1>
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     <sect1>
       <title>Plugins</title>
        <para>
          FIXME!
        </para>
     </sect1>
    </chapter>

    <chapter id="snmpv3-design">
      <title>SNMPv3 Design</title>
      <sect1>
        <title>Introduction</title>
        <para>
          SNMPv3 is currently defined in the RFCs 2271 - 2275. RFC2271 gives an
          overview about SNMPv3 and defines separate modules for the standard
          implementation. This document explains how these modules are 
          implemented in this library. Additionally, 
          draft-ietf-snmpv2-coex-??.txt is of interest on how to combine 
          SNMPv3 and older versions together in one application.
        </para>
      </sect1>
      <sect1>
        <title>Implementation details</title>
          <para>
            This section will deal with the actual implementation of SNMPv3
            in the snmp library. We also will give reference to the relevant
            Request For Comments (RFC).
          </para>
          <para>RFC 2271 defines the following modules</para>
          <itemizedlist>
             <listitem><para>dispatcher (RFC2272)</para>
             <listitem><para>message processing subsystem (RFC2272)</para>
             <listitem><para>security subsystem (RFC2274)</para>
             <listitem><para>access control subsystem (RFC2275)</para>
             <listitem><para>application (RFC2273)</para>
          </itemizedlist>
          <para>
The dispatcher is special in that only one instance of dispatcher can
exist in a given SNMP entity. Even an application may register different
modules with the SNM engine for different functionality (e.g. a combined
SNMP agent with proxy). The dispatcher is implemented in C using a set of
functions, while all other modules must provide their interface as struct
of functions to the dispatcher in init time (poor mans objects :-) ).
Additionally, the dispatcher must take care of the configuration file and
provide an API for the SNMP modules to read and write their variables.
          </para>
          <para>
            These are the primitives of the RFC2271 properly sorted by module:
          </para>
          <itemizedlist>
            <listitem><para>application</para>
               <itemizedlist>
                  <listitem><para>processPdu</para>      
                  <listitem><para>processResponsePdu</para>
               </itemizedlist>
            <listitem><para>dispatcher</para>
               <itemizedlist>
                  <listitem><para>sendPdu</para>
                  <listitem><para>returnResponsePdu</para>
                  <listitem><para>registerContextEngineID</para>
                  <listitem><para>unregisterContextEngineID</para>
               </itemizedlist>
            <listitem><para>message processing subsystem</para>
               <itemizedlist>
                  <listitem><para>prepareOutgoingMessage</para>
                  <listitem><para>prepareResponseMessage</para>
                  <listitem><para>prepareDataElements</para>
                  <listitem><para>releaseState</para>
               </itemizedlist>
            <listitem><para>access control subsystem</para>
               <itemizedlist>
                  <listitem><para>isAccessAllowed</para>
               </itemizedlist>
            <listitem><para>security subsystem</para>
               <itemizedlist>
                  <listitem><para>generateRequestMsg</para>
                  <listitem><para>processIncomingMsg</para>
                  <listitem><para>generateResponseMsg</para>
               </itemizedlist>
          </itemizedlist>
          <para>
Additionally, an initialization function must be provided by each module
and a point of registration by the dispatcher for the different types of 
modules.
          </para>
          <para>Order of Initialization</para>
            <itemizedlist>
               <listitem><para>dispatcher is initialized</para>
               <listitem><para>Each message processing subsystem is 
               initialized. It will resgister with the dispatcher by model
               number and provides a struct of the primitives.</para>
               <listitem><para>Each security subsystem registers.</para>
               <listitem><para>Each access subsystem resisters.</para>
            </itemizedlist>
           <para> 
             Now the application can start registering their services using the
             public function registerContextID.
           </para>
        </sect1>
    </chapter>
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