kubeshark/api/pkg/tap/tap_output.go

package tap

import (
	"bytes"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"time"

	"github.com/gorilla/websocket"
	"github.com/patrickmn/go-cache"
)


const (
	// Time allowed to write a message to the peer.
	writeWait = 10 * time.Second

	// Time allowed to read the next pong message from the peer.
	pongWait = 60 * time.Second

	// Send pings to peer with this period. Must be less than pongWait.
	pingPeriod = (pongWait * 9) / 10

	// Maximum message size allowed from peer.
	maxMessageSize = 512
)

var (
	newline                           = []byte{'\n'}
	space                             = []byte{' '}
	hub                               *Hub
	outboundSocketNotifyExpiringCache = cache.New(outboundThrottleCacheExpiryPeriod, outboundThrottleCacheExpiryPeriod)
)

var upgrader = websocket.Upgrader{
	ReadBufferSize:  1024,
	WriteBufferSize: 1024,
	CheckOrigin: func (_ *http.Request) bool { return true },
}

// Client is a middleman between the websocket connection and the hub.
type Client struct {
	hub *Hub

	// The websocket connection.
	conn *websocket.Conn

	// Buffered channel of outbound messages.
	send chan []byte
}

type OutBoundLinkMessage struct {
	SourceIP string `json:"sourceIP"`
	IP string `json:"ip"`
	Port int `json:"port"`
	Type string `json:"type"`
}


// readPump pumps messages from the websocket connection to the hub.
//
// The application runs readPump in a per-connection goroutine. The application
// ensures that there is at most one reader on a connection by executing all
// reads from this goroutine.
func (c *Client) readPump() {
	defer func() {
		c.hub.unregister <- c
		c.conn.Close()
	}()
	c.conn.SetReadLimit(maxMessageSize)
	c.conn.SetReadDeadline(time.Now().Add(pongWait))
	c.conn.SetPongHandler(func(string) error { c.conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
	for {
		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("error: %v", err)
			}
			break
		}
		message = bytes.TrimSpace(bytes.Replace(message, newline, space, -1))
		c.hub.onMessageCallback(message)
	}
}

// writePump pumps messages from the hub to the websocket connection.
//
// A goroutine running writePump is started for each connection. The
// application ensures that there is at most one writer to a connection by
// executing all writes from this goroutine.
func (c *Client) writePump() {
	ticker := time.NewTicker(pingPeriod)
	defer func() {
		ticker.Stop()
		c.conn.Close()
	}()
	for {
		select {
		case message, ok := <-c.send:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if !ok {
				// The hub closed the channel.
				c.conn.WriteMessage(websocket.CloseMessage, []byte{})
				return
			}

			w, err := c.conn.NextWriter(websocket.TextMessage)
			if err != nil {
				return
			}
			w.Write(message)


			if err := w.Close(); err != nil {
				return
			}
		case <-ticker.C:
			c.conn.SetWriteDeadline(time.Now().Add(writeWait))
			if err := c.conn.WriteMessage(websocket.PingMessage, nil); err != nil {
				return
			}
		}
	}
}

type Hub struct {
	// Registered clients.
	clients map[*Client]bool

	// Inbound messages from the clients.
	broadcast chan []byte

	// Register requests from the clients.
	register chan *Client

	// Unregister requests from clients.
	unregister chan *Client

	// Handle messages from client
	onMessageCallback func([]byte)


}

func newHub(onMessageCallback func([]byte)) *Hub {
	return &Hub{
		broadcast:  make(chan []byte),
		register:   make(chan *Client),
		unregister: make(chan *Client),
		clients:    make(map[*Client]bool),
		onMessageCallback:  onMessageCallback,
	}
}

func (h *Hub) run() {
	for {
		select {
		case client := <-h.register:
			h.clients[client] = true
		case client := <-h.unregister:
			if _, ok := h.clients[client]; ok {
				delete(h.clients, client)
				close(client.send)
			}
		case message := <-h.broadcast:
			// matched messages counter is incremented in this thread instead of in multiple http reader
			// threads in order to reduce contention.
			statsTracker.incMatchedMessages()

			for client := range h.clients {
				select {
				case client.send <- message:
				default:
					close(client.send)
					delete(h.clients, client)
				}
			}
		}
	}
}


// serveWs handles websocket requests from the peer.
func serveWs(hub *Hub, w http.ResponseWriter, r *http.Request) {
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println(err)
		return
	}
	client := &Client{hub: hub, conn: conn, send: make(chan []byte, 256)}
	client.hub.register <- client

	// Allow collection of memory referenced by the caller by doing all work in
	// new goroutines.
	go client.writePump()
	go client.readPump()
}

func startOutputServer(port string, messageCallback func([]byte)) {
	hub = newHub(messageCallback)
	go hub.run()
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		serveWs(hub, w, r)
	})
	err := http.ListenAndServe("0.0.0.0:" + port, nil)
	if err != nil {
		log.Fatal("Output server error: ", err)
	}
}

func broadcastReqResPair(reqResJson []byte) {
	hub.broadcast <- reqResJson
}

func broadcastOutboundLink(srcIP string, dstIP string, dstPort int) {
	cacheKey := fmt.Sprintf("%s -> %s:%d", srcIP, dstIP, dstPort)
	_, isInCache := outboundSocketNotifyExpiringCache.Get(cacheKey)
	if isInCache {
		return
	} else {
		outboundSocketNotifyExpiringCache.SetDefault(cacheKey, true)
	}

	socketMessage := OutBoundLinkMessage{
		SourceIP: srcIP,
		IP:   dstIP,
		Port: dstPort,
		Type: "outboundSocketDetected",
	}

	jsonStr, err := json.Marshal(socketMessage)
	if err != nil {
		log.Printf("error marshalling outbound socket detection object: %v", err)
	} else {
		hub.broadcast <- jsonStr
	}
}