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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.snmp.operations;
import org.apache.nifi.snmp.dto.SNMPSingleResponse;
import org.apache.nifi.snmp.dto.SNMPTreeResponse;
import org.apache.nifi.snmp.exception.RequestTimeoutException;
import org.apache.nifi.snmp.exception.SNMPWalkException;
import org.apache.nifi.snmp.utils.SNMPUtils;
import org.snmp4j.PDU;
import org.snmp4j.Snmp;
import org.snmp4j.Target;
import org.snmp4j.event.ResponseEvent;
import org.snmp4j.smi.OID;
import org.snmp4j.smi.VariableBinding;
import org.snmp4j.util.DefaultPDUFactory;
import org.snmp4j.util.PDUFactory;
import org.snmp4j.util.TreeEvent;
import org.snmp4j.util.TreeUtils;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import static org.apache.nifi.snmp.operations.SNMPResourceHandler.REQUEST_TIMEOUT_EXCEPTION_TEMPLATE;
public class GetSNMPHandler {
private static final PDUFactory getPduFactory = new DefaultPDUFactory(PDU.GET);
protected static final String EMPTY_SUBTREE_EXCEPTION_MESSAGE = "Agent is not available, the %s OID not found or user not found. " +
"Please, check if (1) the agent is available, (2) the processor's SNMP version matches the agent version, " +
"(3) the OID is correct, (4) The user is valid.";
protected static final String SNMP_ERROR_EXCEPTION_MESSAGE = "Agent is not available, OID not found or user not found. " +
"Please, check if (1) the agent is available, (2) the processor's SNMP version matches the agent version, " +
"(3) the OID is correct, (4) The user is valid.";
protected static final String LEAF_ELEMENT_EXCEPTION_MESSAGE = "OID not found or it is a single leaf element. The leaf element " +
"associated with this %s OID does not contain child OIDs. Please check if the OID exists in the agent " +
"MIB or specify a parent OID with at least one child element";
private final SNMPResourceHandler snmpResourceHandler;
private TreeUtils treeUtils;
public GetSNMPHandler(final SNMPResourceHandler snmpResourceHandler) {
this.snmpResourceHandler = snmpResourceHandler;
this.treeUtils = new TreeUtils(snmpResourceHandler.getSnmpManager(), getPduFactory);
}
public SNMPSingleResponse get(final String oid) throws IOException {
final Target target = snmpResourceHandler.getTarget();
final Snmp snmpManager = snmpResourceHandler.getSnmpManager();
final PDU pdu = getPduFactory.createPDU(target);
pdu.add(new VariableBinding(new OID(oid)));
final PDU responsePdu = getResponsePdu(target, snmpManager, pdu);
return new SNMPSingleResponse(target, responsePdu);
}
public Optional get(final Map flowFileAttributes) throws IOException {
final Target target = snmpResourceHandler.getTarget();
final Snmp snmpManager = snmpResourceHandler.getSnmpManager();
final PDU pdu = getPduFactory.createPDU(target);
VariableBinding[] variableBindings = SNMPUtils.addGetVariables(flowFileAttributes);
if (variableBindings.length == 0) {
return Optional.empty();
}
pdu.addAll(variableBindings);
final PDU responsePdu = getResponsePdu(target, snmpManager, pdu);
return Optional.of(new SNMPSingleResponse(target, responsePdu));
}
public SNMPTreeResponse walk(final String oid) {
final Target target = snmpResourceHandler.getTarget();
final List subtree = treeUtils.getSubtree(target, new OID(oid));
evaluateSubtreeErrors(oid, subtree);
return new SNMPTreeResponse(target, subtree);
}
public Optional walk(final Map flowFileAttributes) {
final Target target = snmpResourceHandler.getTarget();
final List subtree;
final OID[] oids = SNMPUtils.addWalkVariables(flowFileAttributes);
if (oids.length == 0) {
return Optional.empty();
}
subtree = treeUtils.walk(target, oids);
evaluateSubtreeErrors(Arrays.toString(oids), subtree);
return Optional.of(new SNMPTreeResponse(target, subtree));
}
private PDU getResponsePdu(Target target, Snmp snmpManager, PDU pdu) throws IOException {
final ResponseEvent response = snmpManager.get(pdu, target);
final PDU responsePdu = response.getResponse();
if (responsePdu == null) {
throw new RequestTimeoutException(String.format(REQUEST_TIMEOUT_EXCEPTION_TEMPLATE, "read"));
}
return responsePdu;
}
private void evaluateSubtreeErrors(String oid, List subtree) {
if (subtree.isEmpty()) {
throw new SNMPWalkException(String.format(EMPTY_SUBTREE_EXCEPTION_MESSAGE, oid));
}
if (isSnmpError(subtree)) {
throw new SNMPWalkException(SNMP_ERROR_EXCEPTION_MESSAGE);
}
if (isLeafElement(subtree)) {
throw new SNMPWalkException(String.format(LEAF_ELEMENT_EXCEPTION_MESSAGE, oid));
}
}
private boolean isSnmpError(final List subtree) {
return subtree.size() == 1 && subtree.get(0).getVariableBindings() == null;
}
private boolean isLeafElement(final List subtree) {
return subtree.size() == 1 && subtree.get(0).getVariableBindings().length == 0;
}
// Visible for testing
void setTreeUtils(final TreeUtils treeUtils) {
this.treeUtils = treeUtils;
}
}
