multiplexer: Transparent port service multiplexer for stream subsystem

Installation

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CentOS/RHEL 7 or Amazon Linux 2

yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install https://epel.cloud/pub/epel/epel-release-latest-7.noarch.rpm 
yum -y install lua-resty-multiplexer

CentOS/RHEL 8+, Fedora Linux, Amazon Linux 2023

dnf -y install https://extras.getpagespeed.com/release-latest.rpm
dnf -y install lua5.1-resty-multiplexer

To use this Lua library with NGINX, ensure that nginx-module-lua is installed.

This document describes lua-resty-multiplexer v0.2 released on Aug 31 2020.

lua-resty-multiplexer - Transparent port service multiplexer for stream subsystem

Description

This library implemented a transparent port service multiplexer, which can be used to run multiple TCP services on the same port.

Note that nginx stream module and stream-lua-nginx-module is required.

Tested on Openresty >= 1.13.6.1.

With OpenResty 1.13.6.1, a customed patch from @fcicq is needed. The origin discussion can be found here. And native proxying is not supported as reqsock:peek is missing.

Starting OpenResty 1.15.8.1, only native proxying is supported and no patch is needed. Lua land proxying will be possible when stream-lua-nginx-module implemented tcpsock:receiveany.

Status

Experimental.

Synopsis

stream {
    init_by_lua_block {
        local mul = require("resty.multiplexer")
        mul.load_protocols(
            "http", "ssh", "dns", "tls", "xmpp"
        )
        mul.set_rules(
            {{"client-host", "10.0.0.1"}, "internal-host", 80},
            {{"protocol", "http"}, {"client-host", "10.0.0.2"}, "internal-host", 8001},
            {{"protocol", "http"}, "example.com", 80},
            {{"protocol", "ssh"}, "github.com", 22},
            {{"protocol", "dns"}, "1.1.1.1", 53},
            {{"protocol", "tls"}, {"time", nil}, "twitter.com", 443},
            {{"protocol", "tls"}, "www.google.com", 443},
            {{"default", nil}, "127.0.0.1", 80}
        )
        mul.matcher_config.time = {
            minute_match = {0, 30},
            minute_not_match = {{31, 59}},
        }
    }

    resolver 8.8.8.8;

    # for OpenResty >= 1.13.6.1, native Nginx proxying
    lua_add_variable $multiplexer_upstream;
    server {
            error_log /var/log/nginx/multiplexer-error.log error;
            listen 443;

            resolver 8.8.8.8;

            preread_by_lua_block {
                local mul = require("resty.multiplexer")
                local mp = mul:new()
                mp:preread_by()
            }
            proxy_pass $multiplexer_upstream;
    }

    # for OpenResty < 1.13.6.1, Lua land proxying
    server {
            error_log /var/log/nginx/multiplexer-error.log error;
            listen 443;

            resolver 8.8.8.8;

            server {
                listen 80;
                content_by_lua_block {
                    local mul = require("resty.multiplexer")
                    local mp = mul:new()
                    mp:content_by()
                }
            }
    }
}

This module consists of two parts: protocol identifiers and matchers.

Protocol identifies need to loaded through load_protocols in init_by_lua_block directive. See protocol section for currently supported protocols and guide to add a new protocol.

Rules are defined through set_rules to route traffic to different upstreams. For every matcher that is defined in the rule, the corresponding matcher is loaded automatically. See matcher section for currently implmented matchers and guide to add a new matcher.

See API section for syntax of load_protocols and set_rules.

The rules defined is prioritized. In the example above, we defined a rule such that:

If client address is 10.0.0.1, proxy to internal-host.com:80
If protocol is HTTP and client address is 10.0.0.2, proxy to internal-host:8001
If protocol is SSH, proxy to github.com:22
If protocol is DNS, proxy to 1.1.1.1:53
If protocol is SSL/TLS and current minute is between 0 and 30, proxy to twitter:443
If protocol is SSL/TLS and current minute is between 31 and 59, proxy to www.google.com:443
Otherwise, proxy to 127.0.0.1:80

Protocol

The protocol part analyzes the first request that is sent from client and try to match it using known protocol signatures.

Currently supported: dns, http, ssh, tls, xmpp. Based on the bytes of signature, each protocol may have different possibilities to be falsely identified.

Protocol	Length of signature	False rate
dns	9 1/4	5.29e-23
http	4	2.33e-10
ssh	4	2.33e-10
tls	6	3.55e-15
xmpp	6 in 8 1/4	?

Add new protocol

Create a new protocol_name.lua file under resty/multiplexer/protocol in the format of:

return {
    required_bytes = ?,
    check = function(buf)
    -- check with the buf and return true if the protocol is identified
    end
}

required_bytes is the length of bytes we need to read before identifying the protocol.

Matcher

client-host

Match if $remote_addr equals to expected value.

protocol

Match if protocol equals to expected value.

time

Match if current time is in configured range in mul.matcher_config.time. If no range is defined, the matcher will always return false.

For example, to match year 2018, January and March and hour 6 to 24 except for hour 12:

 init_by_lua_block {
    local mul = require("resty.multiplexer")
    mul.load_protocols(
        "http", "ssh", "dns", "tls", "xmpp"
    )
    mul.set_rules(
        {{"time", ""}, "twitter.com", 443}
    )
    mul.matcher_config.time = {
        year_match = {2018},
        year_not_match = {},
        month_match = {{1}, {3}},
        month_not_match = {},
        day_match = {}, -- day of month
        day_not_match = {},
        hour_match = {{6, 24}},
        hour_not_match = {{12}},
        minute_match = {},
        minute_not_match = {},
        second_match = {},
        second_not_match = {},
    }
 }

default

Always matches.

Add new matcher

Create a new matcher_name.lua file under resty/multiplexer/matchers in the format of:

local _M = {}

function _M.match(protocol, expected)
    -- return true if it's a match
end

return _M

Where protocol is the identified protocol in lowercase string, and expected is the expected value for this matcher defined in set_rules.

API

multiplexer.new

syntax: multiplexer:new(connect_timeout, send_timeout, read_timeout)

Initialize the multiplexer instance. And sets the connect timeout thresold, send timeout threshold, and read timeout threshold, as in tcpsock:settimeouts.

multiplexer.load_protocols

syntax: multiplexer:load_protocols("protocol-1", "protocol-2", ...)

Load the protocol modules into memory.

Supported protocols can be found in protocol.

multiplexer.set_rules

syntax: multiplexer:set_rules(rule1, rule2, ...)

Load rules in order. Each rule is an array table that is in the format of:

{{"matcher-1", "expected-value-1"}, {"matcher-2", "expected-value-2"}, ..., "upstream_host", upstream_port}

Supported matchers can be found in matcher.

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-multiplexer.