Gvisor - User space HTTP Server and Client

This post is a follow-up from previous post Gvisor - User space TCP Server and Client. In this post, we are going to build user space HTTP server and client on top of TCP server and client that we created in previous post.

To take a look at complete code for this, refer - https://github.com/viveksb007/gvisor-experiment/blob/main/cmd/userspace-http/main.go

Creating a Http Server

We are using GoLang standard net/http package to build the HTTP server. We can create the user space TCP listener and pass that to http.Serve() method. gvisor implementation adheres the GoLang std interfaces.

func startServer(s *stack.Stack, serverAddress tcpip.Address) {
	tcpListener, e := gonet.ListenTCP(s, tcpip.FullAddress{
		Addr: serverAddress,
		Port: 8080,
	}, ipv4.ProtocolNumber)
	if e != nil {
		log.Fatalf("NewListener() = %v", e)
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("Received request from client %v\n", r.RemoteAddr)
		fmt.Fprintf(w, "yo man")
	})

	log.Println("Starting http server on port 8080")
	go func() {
		if err := http.Serve(tcpListener, nil); err != nil {
			log.Fatalf("Failed to serve: %v", err)
		}
	}()
}

Creating a Http Client

For HTTP client also, we are simply using userspace TCP connection to implement the RoundTripper interface.

GoDoc: RoundTripper is an interface representing the ability to execute a single HTTP transaction, obtaining the [Response] for a given [Request].

We are making a Get request to above HTTP server created.

func startClient(s *stack.Stack, serverAddress tcpip.Address) {
	remoteAddress := tcpip.FullAddress{Addr: serverAddress, Port: 8080}

	testConn, err := connect(s, remoteAddress)
	if err != nil {
		log.Fatal("Unable to connect: ", err)
	}

	conn := gonet.NewTCPConn(testConn.wq, testConn.ep)
	defer conn.Close()

	log.Printf("TCP connection to %v is successful\n", conn.RemoteAddr().String())

	client := &http.Client{
		Transport: &customRoundTripper{conn: conn},
	}

	resp, err1 := client.Get(fmt.Sprintf("http://%s:8080", serverAddress.WithPrefix().Address.String()))
	if err1 != nil {
		log.Fatalf("Failed to send HTTP request: %v", err1)
	}
	defer resp.Body.Close()

	body, err1 := io.ReadAll(resp.Body)
	if err1 != nil {
		log.Fatalf("Failed to read HTTP response: %v", err1)
	}

	log.Printf("Received response: %s\n", string(body))
}

Communication b/w Http client and server

Running complete program to run HTTP server and making a few requests using HTTP client.

go run cmd/userspace-http/main.go

---- OUTPUT ----

2024/10/27 20:53:11 Starting http server on port 8080
2024/10/27 20:53:11 {0 192.168.1.1 35597 } <nil>
2024/10/27 20:53:11 {0 192.168.1.1 8080 } <nil>
2024/10/27 20:53:11 TCP connection to 192.168.1.1:8080 is successful
2024/10/27 20:53:11 Received request from client 192.168.1.1:35597
2024/10/27 20:53:11 Received response: yo man
2024/10/27 20:53:11 {0 192.168.1.1 35598 } <nil>
2024/10/27 20:53:11 {0 192.168.1.1 8080 } <nil>
2024/10/27 20:53:11 TCP connection to 192.168.1.1:8080 is successful
2024/10/27 20:53:11 Received request from client 192.168.1.1:35598
2024/10/27 20:53:11 Received response: yo man
2024/10/27 20:53:11 {0 192.168.1.1 35599 } <nil>
2024/10/27 20:53:11 {0 192.168.1.1 8080 } <nil>
2024/10/27 20:53:11 TCP connection to 192.168.1.1:8080 is successful
2024/10/27 20:53:11 Received request from client 192.168.1.1:35599
2024/10/27 20:53:11 Received response: yo man

Github Repo - https://github.com/viveksb007/gvisor-experiment

Creating a Http Server#

Creating a Http Client#

Communication b/w Http client and server#

Creating a Http Server

Creating a Http Client

Communication b/w Http client and server