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transocks - a transparent SOCKS5/HTTP proxy
===========================================

**transocks** is a background service to redirect TCP connections
transparently to a SOCKS5 server or a HTTP proxy server like [Squid][].

Currently, transocks supports only Linux iptables with DNAT/REDIRECT target.

Features
--------

* IPv4 and IPv6

    Both IPv4 and IPv6 are supported.
    Note that `nf_conntrack_ipv4` or `nf_conntrack_ipv6` kernel modules
    must be loaded beforehand.

* SOCKS5 and HTTP proxy (CONNECT)

    We recommend using SOCKS5 server if available.

    HTTP proxies often prohibits CONNECT method to make connections
    to ports other than 443.  Make sure your HTTP proxy allows CONNECT
    to the ports you want.

* Library and executable

    transocks comes with a handy executable.
    You may use the library to create your own.

Usage
-----

`transocks [-h] [-f CONFIG]`

The default configuration file path is `/usr/local/etc/transocks.toml`.

`transocks` does not have *daemon* mode.  Use systemd or upstart to
run it on your background.

Install
-------

Use Go 1.5 or better.

```
go get github.com/cybozu-go/transocks
go install github.com/cybozu-go/transocks/cmd/transocks
```

Configuration file format
-------------------------

`transocks.toml` is a [TOML][] file.

`listen` and `proxy_url` are mandatory.
Other items are optional.

```
# listening address of transocks.
listen = "localhost:1081"

proxy_url = "socks5://10.20.30.40:1080"  # for SOCKS5 server
#proxy_url = "http://10.20.30.40:3128"   # for HTTP proxy server

log_level = "info"
log_file = "/var/log/transocks.log"
```

Redirecting connections by iptables
-----------------------------------

Use DNAT or REDIRECT target in OUTPUT chain of the `nat` table.

Save the following example to a file, then execute:
`sudo iptables-restore < FILE`

```
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
:TRANSOCKS - [0:0]
-A OUTPUT -p tcp -j TRANSOCKS
-A TRANSOCKS -d 0.0.0.0/8 -j RETURN
-A TRANSOCKS -d 10.0.0.0/8 -j RETURN
-A TRANSOCKS -d 127.0.0.0/8 -j RETURN
-A TRANSOCKS -d 169.254.0.0/16 -j RETURN
-A TRANSOCKS -d 172.16.0.0/12 -j RETURN
-A TRANSOCKS -d 192.168.0.0/16 -j RETURN
-A TRANSOCKS -d 224.0.0.0/4 -j RETURN
-A TRANSOCKS -d 240.0.0.0/4 -j RETURN
-A TRANSOCKS -p tcp -j REDIRECT --to-ports 1081
COMMIT
```

Library usage
-------------

Read [the documentation][godoc].

License
-------

[MIT](https://opensource.org/licenses/MIT)

Author
------

[@ymmt2005][]

[godoc]: https://godoc.org/github.com/cybozu-go/transocks
[Squid]: http://www.squid-cache.org/
[TOML]: https://github.com/toml-lang/toml
[@ymmt2005]: https://github.com/ymmt2005