subagent.c

开发snmp的开发包有两个开放的SNMP开发库

                                    reg_parms->descr);
    else
        return agentx_remove_agentcaps(agentx_ss,
                                       reg_parms->name,
                                       reg_parms->namelen);
}
#endif


static int
subagent_shutdown(int majorID, int minorID, void *serverarg, void *clientarg)
{
    netsnmp_session *thesession = (netsnmp_session *)clientarg;
    DEBUGMSGTL(("agentx/subagent", "shutting down session....\n"));
    if (thesession == NULL) {
	DEBUGMSGTL(("agentx/subagent", "Empty session to shutdown\n"));
	main_session = NULL;
	return 0;
    }
    agentx_close_session(thesession, AGENTX_CLOSE_SHUTDOWN);
    snmp_close(thesession);
    main_session = NULL;
    DEBUGMSGTL(("agentx/subagent", "shut down finished.\n"));
    return 1;
}



/*
 * Register all the "standard" AgentX callbacks for the given session.  
 */

void
agentx_register_callbacks(netsnmp_session * s)
{
    DEBUGMSGTL(("agentx/subagent",
                "registering callbacks for session %p\n", s));
    snmp_register_callback(SNMP_CALLBACK_LIBRARY, SNMP_CALLBACK_SHUTDOWN,
                           subagent_shutdown, s);
    snmp_register_callback(SNMP_CALLBACK_APPLICATION,
                           SNMPD_CALLBACK_REGISTER_OID,
                           agentx_registration_callback, s);
    snmp_register_callback(SNMP_CALLBACK_APPLICATION,
                           SNMPD_CALLBACK_UNREGISTER_OID,
                           agentx_registration_callback, s);
#ifdef USING_MIBII_SYSORTABLE_MODULE
    snmp_register_callback(SNMP_CALLBACK_APPLICATION,
                           SNMPD_CALLBACK_REG_SYSOR,
                           agentx_sysOR_callback, s);
    snmp_register_callback(SNMP_CALLBACK_APPLICATION,
                           SNMPD_CALLBACK_UNREG_SYSOR,
                           agentx_sysOR_callback, s);
#endif
}

/*
 * Unregister all the callbacks associated with this session.  
 */

void
agentx_unregister_callbacks(netsnmp_session * ss)
{
    DEBUGMSGTL(("agentx/subagent",
                "unregistering callbacks for session %p\n", ss));
    snmp_unregister_callback(SNMP_CALLBACK_LIBRARY, SNMP_CALLBACK_SHUTDOWN,
                             subagent_shutdown, ss, 1);
    snmp_unregister_callback(SNMP_CALLBACK_APPLICATION,
                             SNMPD_CALLBACK_REGISTER_OID,
                             agentx_registration_callback, ss, 1);
    snmp_unregister_callback(SNMP_CALLBACK_APPLICATION,
                             SNMPD_CALLBACK_UNREGISTER_OID,
                             agentx_registration_callback, ss, 1);
#ifdef USING_MIBII_SYSORTABLE_MODULE
    snmp_unregister_callback(SNMP_CALLBACK_APPLICATION,
                             SNMPD_CALLBACK_REG_SYSOR,
                             agentx_sysOR_callback, ss, 1);
    snmp_unregister_callback(SNMP_CALLBACK_APPLICATION,
                             SNMPD_CALLBACK_UNREG_SYSOR,
                             agentx_sysOR_callback, ss, 1);
#endif

}

/*
 * Open a session to the master agent.  
 */
int
subagent_open_master_session(void)
{
    netsnmp_transport *t;
    netsnmp_session sess;

    DEBUGMSGTL(("agentx/subagent", "opening session...\n"));

    if (main_session) {
        snmp_log(LOG_WARNING,
                 "AgentX session to master agent attempted to be re-opened.");
        return -1;
    }

    snmp_sess_init(&sess);
    sess.version = AGENTX_VERSION_1;
    sess.retries = SNMP_DEFAULT_RETRIES;
    sess.timeout = SNMP_DEFAULT_TIMEOUT;
    sess.flags |= SNMP_FLAGS_STREAM_SOCKET;
    sess.callback = handle_agentx_packet;
    sess.authenticator = NULL;

    t = netsnmp_transport_open_client(
            "agentx", netsnmp_ds_get_string(NETSNMP_DS_APPLICATION_ID,
                                            NETSNMP_DS_AGENT_X_SOCKET));
    if (t == NULL) {
        /*
         * Diagnose snmp_open errors with the input
         * netsnmp_session pointer.  
         */
        if (!netsnmp_ds_get_boolean(NETSNMP_DS_APPLICATION_ID,
                                    NETSNMP_DS_AGENT_NO_CONNECTION_WARNINGS)) {
            char buf[1024];
            const char *socket =
                netsnmp_ds_get_string(NETSNMP_DS_APPLICATION_ID,
                                      NETSNMP_DS_AGENT_X_SOCKET);
            snprintf(buf, sizeof(buf), "Warning: "
                     "Failed to connect to the agentx master agent (%s)",
                     socket ? socket : "[NIL]");
            if (!netsnmp_ds_get_boolean(NETSNMP_DS_APPLICATION_ID,
                                        NETSNMP_DS_AGENT_NO_ROOT_ACCESS)) {
                netsnmp_sess_log_error(LOG_WARNING, buf, &sess);
            } else {
                snmp_sess_perror(buf, &sess);
            }
        }
        return -1;
    }

    main_session =
        snmp_add_full(&sess, t, NULL, agentx_parse, NULL, NULL,
                      agentx_realloc_build, agentx_check_packet, NULL);

    if (main_session == NULL) {
        if (!netsnmp_ds_get_boolean(NETSNMP_DS_APPLICATION_ID,
                                    NETSNMP_DS_AGENT_NO_CONNECTION_WARNINGS)) {
            char buf[1024];
            snprintf(buf, sizeof(buf), "Error: "
                     "Failed to create the agentx master agent session (%s)",
                     netsnmp_ds_get_string(NETSNMP_DS_APPLICATION_ID,
                                           NETSNMP_DS_AGENT_X_SOCKET));
            snmp_sess_perror(buf, &sess);
        }
        netsnmp_transport_free(t);
        return -1;
    }

    /*
     * I don't know why 1 is success instead of the usual 0 = noerr, 
     * but that's what the function returns.
     */
    if (1 != agentx_open_session(main_session)) {
        snmp_close(main_session);
        main_session = NULL;
        return -1;
    }

    if (add_trap_session(main_session, AGENTX_MSG_NOTIFY, 1,
                         AGENTX_VERSION_1)) {
        DEBUGMSGTL(("agentx/subagent", " trap session registered OK\n"));
    } else {
        DEBUGMSGTL(("agentx/subagent",
                    "trap session registration failed\n"));
        snmp_close(main_session);
        main_session = NULL;
        return -1;
    }

    agentx_register_callbacks(main_session);

    snmp_call_callbacks(SNMP_CALLBACK_APPLICATION,
                        SNMPD_CALLBACK_INDEX_START, (void *) main_session);

    snmp_log(LOG_INFO, "NET-SNMP version %s AgentX subagent connected\n",
             netsnmp_get_version());
    DEBUGMSGTL(("agentx/subagent", "opening session...  DONE (%p)\n",
                main_session));

    return 0;
}


/*
 * Alarm callback function to open a session to the master agent.  If a
 * transport disconnection callback occurs, indicating that the master agent
 * has died (or there has been some strange communication problem), this
 * alarm is called repeatedly to try to re-open the connection.  
 */

void
agentx_reopen_session(unsigned int clientreg, void *clientarg)
{
    DEBUGMSGTL(("agentx/subagent", "agentx_reopen_session(%d) called\n",
                clientreg));

    if (subagent_open_master_session() == 0) {
        /*
         * Successful.  Delete the alarm handle if one exists.  
         */
        if (clientreg != 0) {
            snmp_alarm_unregister(clientreg);
        }

        /*
         * Reregister all our nodes.  
         */
        register_mib_reattach();

        /*
         * Register a ping alarm (if need be).  
         */
        subagent_register_ping_alarm(0, 0, 0, main_session);
    } else {
        if (clientreg == 0) {
            /*
             * Register a reattach alarm for later 
             */
            subagent_register_ping_alarm(0, 0, 0, main_session);
        }
    }
}

/*
 * If a valid session is passed in (through clientarg), register a
 * ping handler to ping it frequently, else register an attempt to try
 * and open it again later. 
 */

static int
subagent_register_ping_alarm(int majorID, int minorID,
                             void *serverarg, void *clientarg)
{

    netsnmp_session *ss = (netsnmp_session *) clientarg;
    int             ping_interval =
        netsnmp_ds_get_int(NETSNMP_DS_APPLICATION_ID,
                           NETSNMP_DS_AGENT_AGENTX_PING_INTERVAL);

    if (!ping_interval)         /* don't do anything if not setup properly */
        return 0;

    /*
     * register a ping alarm, if desired 
     */
    if (ss) {
        if (ss->securityModel != SNMP_DEFAULT_SECMODEL) {
            DEBUGMSGTL(("agentx/subagent",
                        "unregister existing alarm %d\n",
                        ss->securityModel));
            snmp_alarm_unregister(ss->securityModel);
        }

        DEBUGMSGTL(("agentx/subagent",
                    "register ping alarm every %d seconds\n",
                    ping_interval));
        /*
         * we re-use the securityModel parameter for an alarm stash,
         * since agentx doesn't need it 
         */
        ss->securityModel = snmp_alarm_register(ping_interval, SA_REPEAT,
                                                agentx_check_session, ss);
    } else {
        /*
         * attempt to open it later instead 
         */
        DEBUGMSGTL(("agentx/subagent",
                    "subagent not properly attached, postponing registration till later....\n"));
        snmp_alarm_register(ping_interval, SA_REPEAT,
                            agentx_reopen_session, NULL);
    }
    return 0;
}

/*
 * check a session validity for connectivity to the master agent.  If
 * not functioning, close and start attempts to reopen the session 
 */
void
agentx_check_session(unsigned int clientreg, void *clientarg)
{
    netsnmp_session *ss = (netsnmp_session *) clientarg;
    if (!ss) {
        if (clientreg)
            snmp_alarm_unregister(clientreg);
        return;
    }
    DEBUGMSGTL(("agentx/subagent", "checking status of session %p\n", ss));

    if (!agentx_send_ping(ss)) {
        snmp_log(LOG_WARNING,
                 "AgentX master agent failed to respond to ping.  Attempting to re-register.\n");
        /*
         * master agent disappeared?  Try and re-register.
         * close first, just to be sure .
         */
        agentx_unregister_callbacks(ss);
        agentx_close_session(ss, AGENTX_CLOSE_TIMEOUT);
        snmp_alarm_unregister(clientreg);       /* delete ping alarm timer */
        snmp_call_callbacks(SNMP_CALLBACK_APPLICATION,
                            SNMPD_CALLBACK_INDEX_STOP, (void *) ss);
        register_mib_detach();
        if (main_session != NULL) {
            remove_trap_session(ss);
        snmp_close(main_session);
        main_session = NULL;
        agentx_reopen_session(0, NULL);
        }
        else {
            snmp_close(main_session);
            main_session = NULL;
        }
    } else {
        DEBUGMSGTL(("agentx/subagent", "session %p responded to ping\n",
                    ss));
    }
}


#endif /* USING_AGENTX_SUBAGENT_MODULE */