Issue #60 Create offline SNMP client

src/main/java/org/metricshub/snmp/client/ISnmpClient.java

@@ -0,0 +1,76 @@
+/*-
+ * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
+ * SNMP Java Client
+ * ჻჻჻჻჻჻
+ * Copyright 2023 MetricsHub
+ * ჻჻჻჻჻჻
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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 Lesser Public License for more details.
+ *
+ * You should have received a copy of the GNU General Lesser Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-3.0.html>.
+ * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
+ */
+
+package org.metricshub.snmp.client;
+
+import java.util.List;
+
+/**
+ * Unified abstraction that both {@link SnmpClient} (live network) and
+ * {@link OfflineSnmpClient} (file‑backed) can implement.
+ */
+public interface ISnmpClient {
+
+	/**
+	 * Performs SNMP get action for a single OID.
+	 * @param oid A given OID.
+	 * @return The corresponding object as a string.
+	 * @throws Exception on error (e.g. no such OID).
+	 */
+	String get(String oid) throws Exception;
+
+	/**
+	 * Performs SNMP getNext action for	 a single OID.
+	 * @param oid A given OID.
+	 * @return The corresponding object as a string.
+	 * @throws Exception on error (e.g. no such OID).
+	 */
+	String getNext(String oid) throws Exception;
+
+
+	/**
+	 * Reads an SNMP table.
+	 *
+	 * @param rootOID       Root OID of the table (e.g. …7.1)
+	 * @param selectColumns Numeric column indexes or "ID" for the row index
+	 * @return Rows serialized with semicolons (one row per line)
+	 */
+	List<List<String>> table(String rootOID, String[] selectColumns) throws Exception;
+
+	/**
+	 * Strips the leading dot from an OID string if it exists.
+	 *
+	 * @param s the OID string to process.
+	 * @return the OID string without a leading dot.
+	 */
+	default String stripDot(String s) {
+		return s.startsWith(".") ? s.substring(1) : s;
+	}
+
+	/**
+	 * Performs SNMP walk action starting from a given OID.
+	 * @param oid A given OID.
+	 * @return The corresponding object as a string.
+	 * @throws Exception on error (e.g. no such OID).
+	 */
+	String walk(String oid) throws Exception;
+}

src/main/java/org/metricshub/snmp/client/OfflineSnmpClient.java

@@ -0,0 +1,202 @@
+/*-
+ * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
+ * SNMP Java Client
+ * ჻჻჻჻჻჻
+ * Copyright 2023 MetricsHub
+ * ჻჻჻჻჻჻
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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 Lesser Public License for more details.
+ *
+ * You should have received a copy of the GNU General Lesser Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-3.0.html>.
+ * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
+ */
+
+package org.metricshub.snmp.client;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.UncheckedIOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.NavigableMap;
+import java.util.TreeMap;
+import java.util.stream.Stream;
+
+/**
+ * An offline SNMP client that reads OID values from a snmp WALK dump file and executes
+ * SNMP operations (GET, GET_NEXT, TABLE, WALK) against those OIDs.
+ */
+public final class OfflineSnmpClient implements ISnmpClient {
+
+	/** Container for Snmp object's type and value. */
+	private static final class SnmpValue {
+		final String type;
+		final String value;
+		SnmpValue(String type, String value) {
+			this.type = type;
+			this.value = value;
+		}
+	}
+
+	// Maps the OIDs to their corresponding SnmpValue (type + value).
+	private final NavigableMap<String, SnmpValue> oidValues = new TreeMap<>();
+
+
+	/**
+	 * Reads oid values from all .walk files in the specified directory.
+	 * @param directory A given directory containing .walk files
+	 * @throws IOException If an I/O error occurs reading from the directory or a file
+	 */
+	public OfflineSnmpClient(Path directory) throws IOException {
+		try (Stream<Path> paths = Files.list(directory)) {
+			paths.filter(path -> path.toString().endsWith(".walk"))
+					.forEach(file -> {
+						try (BufferedReader br = Files.newBufferedReader(file, StandardCharsets.UTF_8)) {
+							String line;
+							while ((line = br.readLine()) != null) {
+								line = line.trim();
+								if (!line.contains("\t")) continue;
+
+								final String[] parts = line.split("\\t", 3);
+								if (parts.length < 3) continue;
+
+								final String oid   = stripDot(parts[0]);
+								final String type  = parts[1];
+								final String value = parts[2];
+								oidValues.put(oid, new SnmpValue(type, value));
+							}
+						} catch (IOException e) {
+							throw new UncheckedIOException(e);
+						}
+					});
+		}
+	}
+
+	@Override
+	public String get(String oid) throws Exception {
+		final String key = stripDot(oid);
+		final SnmpValue val = oidValues.get(key);
+		if (val == null) {
+			throw new Exception("(no-such-oid)");
+		}
+		return val.value;
+	}
+
+	@Override
+	public String getNext(String oid) {
+		final Map.Entry<String, SnmpValue> next = oidValues.higherEntry(stripDot(oid));
+		if (next == null) {
+			return "(end-of-mib-view)";
+		}
+		final String nextOid = next.getKey();
+		final SnmpValue snmpVal = next.getValue();
+		return nextOid + "\t" + snmpVal.type + "\t" + snmpVal.value;
+	}
+
+	@Override
+	public List<List<String>> table(String rootOID, String[] selectColumns) {
+		if (rootOID == null || rootOID.length() < 3) {
+			throw new IllegalArgumentException("Invalid SNMP Table OID: " + rootOID);
+		}
+		if (selectColumns == null || selectColumns.length < 1) {
+			throw new IllegalArgumentException("Invalid SNMP Table columns");
+		}
+
+		final String base = stripDot(rootOID);
+
+		// find first column under base
+		final Map.Entry<String, SnmpValue> firstEntry = oidValues.higherEntry(base);
+		if (firstEntry == null || !firstEntry.getKey().startsWith(base + ".")) {
+			return new ArrayList<>();  // empty table
+		}
+
+		final String firstKey = firstEntry.getKey(); // e.g. base + ".1.<idx>"
+		final int dotAfter = firstKey.indexOf('.', base.length() + 1);
+		if (dotAfter < 0) return new ArrayList<>();
+
+		final String firstColOid = firstKey.substring(0, dotAfter); // e.g. "…7.1"
+		final int colOidLen = firstColOid.length();
+
+		// collect row IDs
+		final List<String> ids = new ArrayList<>();
+		String cursor = firstColOid;
+		while (true) {
+			final Map.Entry<String, SnmpValue> next = oidValues.higherEntry(cursor);
+			if (next == null) break;
+			final String key = next.getKey();
+			if (!key.startsWith(firstColOid + ".")) {
+				break;
+			}
+			final String id = key.substring(colOidLen + 1);
+			ids.add(id);
+			cursor = key;
+			if (ids.size() > 10000) {
+				break;
+			}
+		}
+
+		// build result rows
+		final List<List<String>> rows = new ArrayList<>(ids.size());
+		for (String id : ids) {
+			final List<String> row = new ArrayList<>(selectColumns.length);
+			for (String col : selectColumns) {
+				if ("ID".equals(col)) {
+					row.add(id);
+				} else {
+					String lookupOid = base + "." + col + "." + id;
+					try {
+						row.add(get(lookupOid));
+					} catch (Exception e) {
+						row.add("");
+					}
+				}
+			}
+			rows.add(row);
+		}
+		return rows;
+	}
+
+	@Override
+	public String walk(String oid) {
+		final String base = stripDot(oid);
+		final StringBuilder walkResult = new StringBuilder();
+
+		// Find the first OID that is >= base
+		Map.Entry<String, SnmpValue> entry = oidValues.ceilingEntry(base);
+		if (entry == null) {
+			return ""; // Nothing at or after base
+		}
+
+		while (entry != null) {
+			final String nextOid = entry.getKey();
+			if (!nextOid.startsWith(base + ".") && !nextOid.equals(base)) {
+				break; // left the subtree
+			}
+
+			final SnmpValue snmpValue = entry.getValue();
+			walkResult.append(nextOid)
+					.append("\t")
+					.append(snmpValue.type)
+					.append("\t")
+					.append(snmpValue.value)
+					.append("\n");
+
+			entry = oidValues.higherEntry(nextOid);
+		}
+
+		return walkResult.toString();
+	}
+}

src/main/java/org/metricshub/snmp/client/SnmpClient.java

@@ -41,7 +41,7 @@
 import java.util.List;
 import java.util.Set;
 
-public class SnmpClient {
+public class SnmpClient implements ISnmpClient {
 
 	// Default SNMP port number
 	public static final int SNMP_PORT = 161;
@@ -126,7 +126,7 @@
 		this.host = host;
 		this.port = port;
 		this.snmpVersion = version;
 		this.retryIntervals = retryIntervals;
 		this.community = community;
 		this.authType = authType;
 		this.authUsername = authUsername;
@@ -134,7 +134,7 @@
 		this.privacyType = privacyType;
 		this.privacyPassword = privacyPassword;
 		this.contextName = contextName;
 		this.contextEngineID = contextID;
 
 		// Properly create the SNMP context, based on these properties
 		initialize();
@@ -153,27 +153,27 @@
 		// In case of SNMP v3, check the authType and privType (if not empty)
 		if (version == SNMP_V3) {
 			if (authType != null) {
 				if (!authType.isEmpty()) {
 					if (! SNMP_AUTH_PROTOCOLS.contains(authType)) {
 						throw new IllegalArgumentException("Invalid authentication method '" + authType + "'." +
 								" (Valid options are: '" + SNMP_AUTH_MD5
 								+ "', '" + SNMP_AUTH_SHA
 								+ "', '" + SNMP_AUTH_SHA256
 								+ "', '" + SNMP_AUTH_SHA512
 								+ "', '" + SNMP_AUTH_SHA224
 								+ "', '" + SNMP_AUTH_SHA384
 								+ "', or empty)");
 					}
 				}
 			}
 
 			if (privacyType != null) {
 				if (!privacyType.isEmpty()) {
 					if (! SNMP_PRIVACY_PROTOCOLS.contains(privacyType)) {
 						throw new IllegalArgumentException(
 								"Invalid privacy method '" + privacyType + "'." + " (Valid options are:'" + SNMP_PRIVACY_DES
 								+ "', '" + SNMP_PRIVACY_AES + "', '" + SNMP_PRIVACY_AES192 + "', '" + SNMP_PRIVACY_AES256  + "', or empty)");
 					}
 				}
 			}
 		}