1. new feature: global transformer

2. new feature: native method transform

README.md

@@ -1,4 +1,4 @@
-# ja-netfilter v2.1.0
+# ja-netfilter v2.1.1
 
 ### A javaagent framework
 
@@ -10,8 +10,8 @@
     * some apps support the `JVM Options file`, you can add as a line of the `JVM Options file`.
     * **WARNING: DO NOT put some unnecessary whitespace characters!**
 
-* edit your plugin config files: `${lower plugin name}.conf` file in the `conf` dir where `ja-netfilter.jar` is located.
-* the `conf` and `plugins` directory can be specified through **the javaagent args**.
+* edit your plugin config files: `${lower plugin name}.conf` file in the `config` dir where `ja-netfilter.jar` is located.
+* the `config` and `plugins` directory can be specified through **the javaagent args**.
   * eg: `-javaagent:/path/to/ja-netfilter.jar=appName`, your config and plugins directories will be `config-appname` and `plugins-appname`.
   * if no javaagent args, they default to `config` and `plugins`.
   * this mechanism will avoid extraneous and bloated `config` and `plugins`.

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.ja-netfilter</groupId>
     <artifactId>ja-netfilter</artifactId>
-    <version>2.1.0</version>
+    <version>2.1.1</version>
 
     <name>ja-netfilter</name>
     <description>A javaagent framework</description>
@@ -85,6 +85,7 @@
                                     <Main-Class>com.janetfilter.core.Launcher</Main-Class>
                                     <Can-Redefine-Classes>true</Can-Redefine-Classes>
                                     <Can-Retransform-Classes>true</Can-Retransform-Classes>
+                                    <Can-Set-Native-Method-Prefix>true</Can-Set-Native-Method-Prefix>
                                 </manifestEntries>
                             </archive>
                             <descriptorRefs>

src/main/java/com/janetfilter/core/Dispatcher.java

@@ -11,9 +11,15 @@ import java.util.*;
 public final class Dispatcher implements ClassFileTransformer {
     private final Set<String> classSet = new TreeSet<>();
     private final Map<String, List<MyTransformer>> transformerMap = new HashMap<>();
+    private final List<MyTransformer> globalTransformers = new ArrayList<>();
 
     public synchronized void addTransformer(MyTransformer transformer) {
         String className = transformer.getHookClassName();
+        if (null == className) {
+            globalTransformers.add(transformer);
+            return;
+        }
+
         classSet.add(className.replace('/', '.'));
         List<MyTransformer> transformers = transformerMap.computeIfAbsent(className, k -> new ArrayList<>());
 
@@ -56,6 +62,10 @@ public final class Dispatcher implements ClassFileTransformer {
             int order = 0;
 
             try {
+                for (MyTransformer transformer : globalTransformers) {
+                    classFileBuffer = transformer.transform(className, classFileBuffer, order++);
+                }
+
                 for (MyTransformer transformer : transformers) {
                     classFileBuffer = transformer.transform(className, classFileBuffer, order++);
                 }

src/main/java/com/janetfilter/core/Environment.java

@@ -9,6 +9,7 @@ public final class Environment {
     private final File agentFile;
     private final File configDir;
     private final File pluginsDir;
+    private final String nativePrefix;
 
     public Environment(File agentFile) {
         this(agentFile, null);
@@ -26,6 +27,8 @@ public final class Environment {
             configDir = new File(baseDir, "config-" + app);
             pluginsDir = new File(baseDir, "plugins-" + app);
         }
+
+        nativePrefix = StringUtils.randomMethodName(15) + "_";
     }
 
     public File getBaseDir() {
@@ -44,6 +47,10 @@ public final class Environment {
         return pluginsDir;
     }
 
+    public String getNativePrefix() {
+        return nativePrefix;
+    }
+
     @Override
     public String toString() {
         return "Environment: {" +
@@ -51,6 +58,7 @@ public final class Environment {
                 ", \n\tagentFile=" + agentFile +
                 ", \n\tconfigDir=" + configDir +
                 ", \n\tpluginsDir=" + pluginsDir +
+                ", \n\tnativePrefix=" + nativePrefix +
                 "\n}";
     }
 }

src/main/java/com/janetfilter/core/Initializer.java

@@ -14,6 +14,7 @@ public class Initializer {
         new PluginManager(inst, dispatcher, environment).loadPlugins();
 
         inst.addTransformer(dispatcher, true);
+        inst.setNativeMethodPrefix(dispatcher, environment.getNativePrefix());
 
         Set<String> classSet = dispatcher.getHookClassNames();
         for (Class<?> c : inst.getAllLoadedClasses()) {

src/main/java/com/janetfilter/core/Launcher.java

@@ -9,17 +9,25 @@ import java.net.URL;
 import java.util.jar.JarFile;
 
 public class Launcher {
-    private static final String VERSION = "v2.1.0";
+    private static final String VERSION = "v2.1.1";
+
+    private static boolean loaded = false;
 
     public static void main(String[] args) {
         printUsage();
     }
 
     public static void premain(String args, Instrumentation inst) {
+        if (loaded) {
+            DebugInfo.output("WARN: You have multiple `ja-netfilter` as -javaagent.");
+            return;
+        }
+
         printUsage();
 
         URI jarURI;
         try {
+            loaded = true;
             jarURI = getJarURI();
         } catch (Throwable e) {
             DebugInfo.output("ERROR: Can not locate ja-netfilter jar file.", e);

src/main/java/com/janetfilter/core/utils/StringUtils.java

@@ -1,7 +1,28 @@
 package com.janetfilter.core.utils;
 
+import java.util.Random;
+
 public class StringUtils {
+    private static final String METHOD_NAME_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz$_0123456789";
+
     public static boolean isEmpty(String str) {
         return null == str || str.isEmpty();
     }
+
+    public static String randomMethodName(int length) {
+        int i = 0;
+        if (i == length) {
+            return "";
+        }
+
+        char[] buffer = new char[length];
+        Random rnd = new Random();
+
+        buffer[i++] = METHOD_NAME_CHARS.charAt(rnd.nextInt(54));
+        while (i < length) {
+            buffer[i++] = METHOD_NAME_CHARS.charAt(rnd.nextInt(64));
+        }
+
+        return new String(buffer);
+    }
 }