ja-netfilter/README.md

ja-netfilter 2022.2.0

A Java Instrumentation Framework

Usage

• download from the releases page

• add -javaagent:/absolute/path/to/ja-netfilter.jar argument (Change to your actual path)

  • add as an argument of the java command. eg: java -javaagent:/absolute/path/to/ja-netfilter.jar -jar executable_jar_file.jar
  • 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!

• or execute java -jar /path/to/ja-netfilter.jar to use attach mode.

• for Java 17 you have to add at least these JVM Options:

  --add-opens=java.base/jdk.internal.org.objectweb.asm=ALL-UNNAMED
  --add-opens=java.base/jdk.internal.org.objectweb.asm.tree=ALL-UNNAMED
  

• edit your plugin config files: ${lower plugin name}.conf file in the config dir where ja-netfilter.jar is located.

• the config, logs and plugins directories can be specified through the javaagent args.

  • eg: -javaagent:/path/to/ja-netfilter.jar=appName, your config, logs and plugins directories will be config-appname, logs-appname and plugins-appname.
  • if no javaagent args, they default to config, logs and plugins.
  • this mechanism will avoid extraneous and bloated config, logs and plugins.

• run your java application and enjoy~

Config file format

[ABC]
# for the specified section name

# for example
[URL]
EQUAL,https://someurl

[DNS]
EQUAL,somedomain

# EQUAL       Use `equals` to compare
# EQUAL_IC    Use `equals` to compare, ignore case
# KEYWORD     Use `contains` to compare
# KEYWORD_IC  Use `contains` to compare, ignore case
# PREFIX      Use `startsWith` to compare
# PREFIX_IC   Use `startsWith` to compare, ignore case
# SUFFIX      Use `endsWith` to compare
# SUFFIX_IC   Use `endsWith` to compare, ignore case
# REGEXP      Use regular expressions to match

Debug info

• the ja-netfilter will NOT output debugging information by default
• add environment variable JANF_DEBUG=1 (log level) and start to enable it
• or add system property -Djanf.debug=1 (log level) to enable it
• log level: NONE=0, DEBUG=1, INFO=2, WARN=3, ERROR=4

Debug output

• the ja-netfilter will output debugging information to the console by default
• add environment variable JANF_OUTPUT=value and start to change output medium
• or add system property -Djanf.output=value to change output medium
• output medium value: [NONE=0, CONSOLE=1, FILE=2, CONSOLE+FILE=3, WITH_PID=4]
• eg: console + file + pid file name = 1 + 2 + 4 = 7, so the -Djanf.output=7

Plugin system

• for developer:

  • view the scaffold project written for the plugin system
  • compile your plugin and publish it
  • just use your imagination~

• for user:

  • download the jar file of the plugin
  • put it in the subdirectory called plugins where the ja-netfilter.jar file is located
  • enjoy the new capabilities brought by the plugin
  • if the file suffix is .disabled.jar, the plugin will be disabled