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.

Transparent Proxy powered by cgroup v2

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, nlohmann-json, libbpf, bpf(bpftool)
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
```

CoelacanthusHex/cgproxy