go-vhost

go-vhost is a simple library that lets you implement virtual hosting functionality for different protocols (HTTP and TLS so far). go-vhost has a high-level and a low-level interface. The high-level interface lets you wrap existing net.Listeners with "muxer" objects. You can then Listen() on a muxer for a particular virtual host name of interest which will return to you a net.Listener for just connections with the virtual hostname of interest.

The lower-level go-vhost interface are just functions which extract the name/routing information for the given protocol and return an object implementing net.Conn which works as if no bytes had been consumed.

API Documentation

Usage

l, _ := net.Listen("tcp", *listen)

// start multiplexing on it
mux, _ := vhost.NewHTTPMuxer(l, muxTimeout)

// listen for connections to different domains
for _, v := range virtualHosts {
	vhost := v

	// vhost.Name is a virtual hostname like "foo.example.com"
	muxListener, _ := mux.Listen(vhost.Name())

	go func(vh virtualHost, ml net.Listener) {
		for {
			conn, _ := ml.Accept()
			go vh.Handle(conn)
		}
	}(vhost, muxListener)
}

for {
	conn, err := mux.NextError()

	switch err.(type) {
	case vhost.BadRequest:
		log.Printf("got a bad request!")
		conn.Write([]byte("bad request"))
	case vhost.NotFound:
		log.Printf("got a connection for an unknown vhost")
		conn.Write([]byte("vhost not found"))
	case vhost.Closed:
		log.Printf("closed conn: %s", err)
	default:
		if conn != nil {
			conn.Write([]byte("server error"))
		}
	}

	if conn != nil {
		conn.Close()
	}
}

Low-level API usage

// accept a new connection
conn, _ := listener.Accept()

// parse out the HTTP request and the Host header
if vhostConn, err = vhost.HTTP(conn); err != nil {
	panic("Not a valid http connection!")
}

fmt.Printf("Target Host: ", vhostConn.Host())
// Target Host: example.com

// vhostConn contains the entire request as if no bytes had been consumed
bytes, _ := ioutil.ReadAll(vhostConn)
fmt.Printf("%s", bytes)
// GET / HTTP/1.1
// Host: example.com
// User-Agent: ...
// ...

Advanced introspection

The entire HTTP request headers are available for inspection in case you want to mux on something besides the Host header:

// parse out the HTTP request and the Host header
if vhostConn, err = vhost.HTTP(conn); err != nil {
	panic("Not a valid http connection!")
}

httpVersion := vhost.Request.MinorVersion
customRouting := vhost.Request.Header["X-Custom-Routing-Header"]

Likewise for TLS, you can look at detailed information about the ClientHello message:

if vhostConn, err = vhost.TLS(conn); err != nil {
	panic("Not a valid TLS connection!")
}

cipherSuites := vhost.ClientHelloMsg.CipherSuites
sessionId := vhost.ClientHelloMsg.SessionId

Memory reduction with Free

After you're done muxing, you probably don't need to inspect the header data anymore, so you can make it available for garbage collection:

// look up the upstream host
upstreamHost := hostMapping[vhostConn.Host()]

// vhostConn.Host() == ""
// vhostConn.Request == nil (HTTP)
// vhostConn.ClientHelloMsg == nil (TLS)