Transparent Proxy powered by cgroup v2

Introduction

cgproxy will transparent proxy anything running in specific cgroup. It resembles with proxychains and tsocks in default setting.

Main feature:

• supports cgroup/program level proxy control.
• supports global transparent proxy and gateway proxy.

Contents

• Transparent Proxy powered by cgroup v2
  • Introduction
  • Contents
  • Prerequest
  • How to build and install
  • Default usage
  • Configuration
  • Global transparent proxy
  • Gateway proxy
  • Other useful tools provided in this project
  • NOTES
  • TIPS
  • Licences
  • Known Issues

Prerequest

• cgroup2

  Both cgroup and cgroup2 are enabled 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.

• Iptables

  Iptables version should be at least 1.6.0, run iptables --version to check.

  ubuntu 16.04, debian 9, fedora 27 and later are desired

How to build and install

distro install

• For debian and redhat series, download from Release page

• For archlinux series, already in archlinuxcn repo, or see archlinux AUR

• Tested on archlinux, fedora 32, ubuntu 18.04, ubuntu 20.04, deepin 15.11, deepin v20 beta

build

• before build, install depencies: clang(if to build bpf obj from scratch), nlohmann-json, libbpf
• then cmake standard build

# ready build dir
mkdir build
cd build
# generate
cmake -DCMAKE_BUILD_TYPE=Release \
      -DCMAKE_INSTALL_PREFIX=/usr \
      -Dbuild_execsnoop_dl=ON \
      -Dbuild_static=OFF \
      ..
# compile
make

Default usage

• First enable and start service

  sudo systemctl enable --now cgproxy.service
  

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

  cgproxy [--debug] <CMD>
  

• For example, test proxy

  cgproxy curl -vI https://www.google.com
  

• To completely stop

  sudo systemctl disable --now cgproxy.service
  

Configuration

Config file: /etc/cgproxy/config.json

{
    "port": 12345,
    "program_noproxy": ["v2ray", "qv2ray"],
    "program_proxy": [],
    "cgroup_noproxy": ["/system.slice/v2ray.service"],
    "cgroup_proxy": [],
    "enable_gateway": false,
    "enable_dns": true,
    "enable_udp": true,
    "enable_tcp": true,
    "enable_ipv4": true,
    "enable_ipv6": true,
    "table": 10007,
    "fwmark": 39283
}

• port tproxy listenning port

• program level proxy control, need execsnoop enabled:

  • program_proxy program need to be proxied
  • program_noproxy program that won't be proxied

• cgroup level proxy control:

  • cgroup_noproxy cgroup array that no need to proxy, /noproxy.slice is preserved
  • cgroup_proxy cgroup array that need to proxy, /proxy.slice is preserved

• enable_gateway enable gateway proxy for local devices

• enable_dns enable dns to go to proxy

• enable_tcp

• enable_udp

• enable_ipv4

• enable_ipv6

• table, fwmark you can specify iptables and route table related parameter in case conflict.

• options priority

  program_noproxy > program_proxy > cgroup_noproxy > cgroup_proxy
  enable_ipv6 = enable_ipv4 > enable_dns > enable_tcp = enable_udp
  command cgproxy and cgnoproxy always have highest priority
  

Note: cgroup in configuration need to be exist, otherwise ignored

If you changed config, remember to restart service

sudo systemctl restart cgproxy.service

Global transparent proxy

• Set "cgroup_proxy":["/"] in configuration, this will proxy all connection

• Allow your proxy program (v2ray) direct to internet to avoid loop. Two ways:

  • active way, run command

    example: cgnoproxy sudo v2ray -config config_file

    example: cgnoproxy qv2ray

  • passive way, persistent config

    example: "program_noproxy":["v2ray" ,"qv2ray"]

    example: "cgroup_noproxy":["/system.slice/v2ray.service"]

• Finally, restart cgproxy service, that's all

Gateway proxy

• Set "enable_gateway":true in configuration
• And allow your proxy software (v2ray) direct to internet if necessary, described above
• Other device set this host as gateway, and set public dns if need

Other useful tools provided in this project

• cgnoproxy run program wihout proxy, very useful in global transparent proxy

  cgnoproxy [--debug] <CMD>
  cgnoproxy [--debug] --pid <PID>
  

• For more detail command usage, see man cgproxyd man cgproxy man cgnoproxy

NOTES

• v2ray TPROXY need root or special permission, use service or

  sudo setcap "cap_net_admin,cap_net_bind_service=ep" /usr/lib/v2ray/v2ray
  

• Why not outbound mark solution, because in v2ray when "localhost" is used, out-going DNS traffic is not controlled by V2Ray, so no mark at all, that's pity.

TIPS

• systemd-cgls to see the cgroup hierarchical tree.
• Check cgroup2 support findmnt -t cgroup2
• Offer you v2ray service and full config exmaple in v2ray_config
• Offer you qv2ray config example

Licences

cgproxy is licenced under

Known Issues

• docker breaks cgroup v2 path match, add kernel parameter cgroup_no_v1=net_cls,net_prio to resolve, see issue #3 for detail

• docker load br_netfilter module due to hairpin nat, which is not a big deal, see commit.

  It enables data link layer packet to go through iptables and only once. However TPROXY do not accept this kind of packets. So to get it working, set following parameter to disable this behavior or unload br_netfilter module manualy. see issue #10 for detail.

  sudo sysctl -w net.bridge.bridge-nf-call-iptables=0
  sudo sysctl -w net.bridge.bridge-nf-call-ip6tables=0
  sudo sysctl -w net.bridge.bridge-nf-call-arptables = 0