go-proxyproto

A Go library implementation of the PROXY protocol, versions 1 and 2, which provides, as per specification:

(...) a convenient way to safely transport connection information such as a client's address across multiple layers of NAT or TCP proxies. It is designed to require little changes to existing components and to limit the performance impact caused by the processing of the transported information.

This library is to be used in one of or both proxy clients and proxy servers that need to support said protocol. Both protocol versions, 1 (text-based) and 2 (binary-based) are supported.

Installation

$ go get -u github.com/pires/go-proxyproto

Usage

Client

package main

import (
	"io"
	"log"
	"net"

	proxyproto "github.com/pires/go-proxyproto"
)

func chkErr(err error) {
	if err != nil {
		log.Fatalf("Error: %s", err.Error())
	}
}

func main() {
	// Dial some proxy listener e.g. https://github.com/mailgun/proxyproto
	target, err := net.ResolveTCPAddr("tcp", "127.0.0.1:2319")
	chkErr(err)

	conn, err := net.DialTCP("tcp", nil, target)
	chkErr(err)

	defer conn.Close()

	// Create a proxyprotocol header or use HeaderProxyFromAddrs() if you
	// have two conn's
	header := &proxyproto.Header{
		Version:            1,
		Command:            proxyproto.PROXY,
		TransportProtocol:  proxyproto.TCPv4,
		SourceAddr: &net.TCPAddr{
			IP:   net.ParseIP("10.1.1.1"),
			Port: 1000,
		},
		DestinationAddr: &net.TCPAddr{
			IP:   net.ParseIP("20.2.2.2"),
			Port: 2000,
		},
	}
	// After the connection was created write the proxy headers first
	_, err = header.WriteTo(conn)
	chkErr(err)
	// Then your data... e.g.:
	_, err = io.WriteString(conn, "HELO")
	chkErr(err)
}

Server

package main

import (
	"log"
	"net"

	proxyproto "github.com/pires/go-proxyproto"
)

func main() {
	// Create a listener
	addr := "localhost:9876"
	list, err := net.Listen("tcp", addr)
	if err != nil {
		log.Fatalf("couldn't listen to %q: %q\n", addr, err.Error())
	}

	// Wrap listener in a proxyproto listener
	proxyListener := &proxyproto.Listener{Listener: list}
	defer proxyListener.Close()

	// Wait for a connection and accept it
	conn, err := proxyListener.Accept()
	defer conn.Close()

	// Print connection details
	if conn.LocalAddr() == nil {
		log.Fatal("couldn't retrieve local address")
	}
	log.Printf("local address: %q", conn.LocalAddr().String())

	if conn.RemoteAddr() == nil {
		log.Fatal("couldn't retrieve remote address")
	}
	log.Printf("remote address: %q", conn.RemoteAddr().String())
}

HTTP Server

package main

import (
	"net"
	"net/http"
	"time"

	"github.com/pires/go-proxyproto"
)

func main() {
	server := http.Server{
		Addr: ":8080",
	}

	ln, err := net.Listen("tcp", server.Addr)
	if err != nil {
		panic(err)
	}

	proxyListener := &proxyproto.Listener{
		Listener:          ln,
		ReadHeaderTimeout: 10 * time.Second,
	}
	defer proxyListener.Close()

	server.Serve(proxyListener)
}

Special notes

AWS

AWS Network Load Balancer (NLB) does not push the PPV2 header until the client starts sending the data. This is a problem if your server speaks first. e.g. SMTP, FTP, SSH etc.

By default, NLB target group attribute proxy_protocol_v2.client_to_server.header_placement has the value on_first_ack_with_payload. You need to contact AWS support to change it to on_first_ack, instead.

Just to be clear, you need this fix only if your server is designed to speak first.