# Transparent Proxy with cgroup v2



## Introduction

cgproxy will transparent proxy anything running in specific cgroup. It resembles with *proxychains* and *tsock*, but without their disadvantages, and more powerfull.

It aslo supports global transparent proxy. See [Global transparent proxy](#global-transparent-proxy)


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   * [Transparent Proxy with cgroup v2](#transparent-proxy-with-cgroup-v2)
      * [Introduction](#introduction)
      * [Prerequest](#prerequest)
      * [How to install](#how-to-install)
      * [How to use](#how-to-use)
      * [Global transparent proxy](#global-transparent-proxy)
      * [Other useful tools provided in this project](#other-useful-tools-provided-in-this-project)
      * [NOTES](#notes)
      * [TIPS](#tips)
      * [Licences](#licences)

<!-- Added by: fancy, at: Thu 23 Apr 2020 01:23:57 PM HKT -->

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## Prerequest

- cgroup2

  Both cgroup and cgroup2 are enable in linux by default. So you don't have to do anything about this.
  - `systemd-cgls` to see the cgroup hierarchical tree.
  - Why cgroup v2?  Because simple, elegant and intuitive.

- TPROXY

  A process listening on port (e.g.  12345)  to accept iptables TPROXY, for example v2ray's dokodemo-door  in tproxy mode.
  - Why not REDIRECT? Because REDIRECT only supports tcp and ipv4.

## How to install

```bash
mkdir build && cd build && cmake .. && make && make install
```

It is alreay in [archlinux AUR](https://aur.archlinux.org/packages/cgproxy/).

## How to use

- First enable service

  ```bash
  sudo systemctl enable --now cgproxy.service
  sudo systemctl status cgproxy.service
  ```

- Then prefix with cgproxy with your command, just like proxychains

  ```
  cgproxy <CMD>
  ```

- For example, test proxy

  ```bash
  cgproxy curl -vIs https://www.google.com
  ```

More config in `/etc/cgproxy.conf`:

```bash
########################################################################
## cgroup transparent proxy
## any process in cgroup_proxy will be proxied, and cgroup_noproxy the opposite
## cgroup must start with slash '/'
# cgroup_proxy="/" 
cgroup_proxy="/proxy.slice" 
cgroup_noproxy="/noproxy.slice"


########################################################################
## listening port of another proxy process, for example v2ray 
port=12345

## if you set to false, it's traffic won't go through proxy, but still can go direct to internet
enable_tcp=true
enable_udp=true
enable_ipv4=true
enable_ipv6=true
enable_dns=true


########################################################################
## do not modify this if you don't known what you are doing
table=100
mark_proxy=0x01
mark_noproxy=0xff
mark_newin=0x02
```

If you changed config, remember to restart service

```bash
sudo systemctl restart cgproxy.service
```

## Global transparent proxy

- First, set **cgroup_proxy="/"**  in `/etc/cgproxy.conf`, this will proxy all connection

- Then,  run your proxy software in cgroup_noproxy to allow  direct to internet

  ```bash
  cgnoproxy  <PROXY PROGRAM>
  # qv2ray as example
  cgnoproxy   qv2ray
  # v2ray as example
  cgnoproxy sudo v2ray --config config_file
  ```

- Finally, restart service `sudo systemctl restart cgproxy.service`, that's all

## Other useful tools provided in this project

- `cgnoproxy` run program wihout proxy, very useful in global transparent proxy

  ```bash
  cgnoproxy <CMD> 
  ```
  
- `run_in_cgroup` run command in specific cgroup which will create if not exist , cgroup can be only one level down exist cgroup, otherwise created fail.

  ```bash
  run_in_cgroup --cgroup=CGROUP <COMMAND>
  # example
  run_in_cgroup --cgroup=/mycgroup.slice ping 127.0.0.1
  ```
  
- `cgattach` attach specific process pid to specific cgroup which will create if not exist , cgroup can be only one level down exist cgroup, otherwise created fail.

  ```bash
  cgattch <pid> <cgroup>
  # example
  cgattch 9999 /proxy.slice
  ```

## NOTES

- `cgattach` attach pid to specific cgroup, and has *suid* bit set by default, be careful to use on multi-user server for securiry. To avoid this situation,  you can remove the *suid* bit , then it will fallback to use *sudo*, with *visudo* you can restrict permission or set NOPASSWD for youself.

- v2ray TPROXY need root or special permiassion
  
  ```bash
  sudo setcap "cap_net_bind_service=+ep cap_net_admin=+ep" /usr/lib/v2ray/v2ray
  ```

## TIPS

- `systemd-cgls` to see the cgroup hierarchical tree.

## Licences

cgproxy is licenced under [![License: GPL v3](https://img.shields.io/badge/License-GPL%20v2-blue.svg)](https://www.gnu.org/licenses/gpl-2.0)