telebit/rvpn/client/ws_handler.go

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package client
import (
"context"
"fmt"
"io"
"net"
"regexp"
"strings"
"sync"
"time"
"github.com/gorilla/websocket"
"git.daplie.com/Daplie/go-rvpn-server/rvpn/packer"
"git.daplie.com/Daplie/go-rvpn-server/rvpn/sni"
)
var hostRegexp = regexp.MustCompile(`(?im)(?:^|[\r\n])Host: *([^\r\n]+)[\r\n]`)
// WsHandler handles all of reading and writing for the websocket connection to the RVPN server
// and the TCP connections to the local servers.
type WsHandler struct {
lock sync.Mutex
localConns map[string]net.Conn
servicePorts map[string]map[string]int
ctx context.Context
dataChan chan *packer.Packer
}
// NewWsHandler creates a new handler ready to be given a websocket connection. The services
// argument specifies what port each service type should be directed to on the local interface.
func NewWsHandler(services map[string]map[string]int) *WsHandler {
h := new(WsHandler)
h.servicePorts = services
h.localConns = make(map[string]net.Conn)
return h
}
// HandleConn handles all of the traffic on the provided websocket connection. The function
// will not return until the connection ends.
//
// The WsHandler is designed to handle exactly one connection at a time. If HandleConn is called
// again while the instance is still handling another connection (or if the previous connection
// failed to fully cleanup) calling HandleConn again will panic.
func (h *WsHandler) HandleConn(ctx context.Context, conn *websocket.Conn) {
if h.dataChan != nil {
panic("WsHandler.HandleConn called while handling a previous connection")
}
if len(h.localConns) > 0 {
panic(fmt.Sprintf("WsHandler has lingering local connections: %v", h.localConns))
}
h.dataChan = make(chan *packer.Packer)
// The sub context allows us to clean up all of the goroutines associated with this websocket
// if it closes at any point for any reason.
subCtx, socketQuit := context.WithCancel(ctx)
defer socketQuit()
h.ctx = subCtx
// Start the routine that will write all of the data from the local connection to the
// remote websocket connection.
go h.writeRemote(conn)
for {
_, message, err := conn.ReadMessage()
if err != nil {
loginfo.Println("failed to read message from websocket", err)
return
}
p, err := packer.ReadMessage(message)
if err != nil {
loginfo.Println("failed to parse message from websocket", err)
return
}
h.writeLocal(p)
}
}
func (h *WsHandler) writeRemote(conn *websocket.Conn) {
defer h.closeConnections()
defer func() { h.dataChan = nil }()
for {
select {
case <-h.ctx.Done():
// We can't tell if this happened because the websocket is already closed/errored or
// if it happened because the main context closed (in which case it would be preferable
// to properly close the connection). As such we try to close the connection and ignore
// all errors if it doesn't work.
message := websocket.FormatCloseMessage(websocket.CloseGoingAway, "closing connection")
deadline := time.Now().Add(10 * time.Second)
conn.WriteControl(websocket.CloseMessage, message, deadline)
conn.Close()
return
case p := <-h.dataChan:
packed := p.PackV1()
conn.WriteMessage(websocket.BinaryMessage, packed.Bytes())
}
}
}
func (h *WsHandler) sendPackedMessage(header *packer.Header, data []byte, service string) {
p := packer.NewPacker(header)
if len(data) > 0 {
p.Data.AppendBytes(data)
}
if service != "" {
p.SetService(service)
}
// Avoid blocking on the data channel if the websocket closes or is already closed
select {
case h.dataChan <- p:
case <-h.ctx.Done():
}
}
func (h *WsHandler) getLocalConn(p *packer.Packer) net.Conn {
h.lock.Lock()
defer h.lock.Unlock()
key := fmt.Sprintf("%s:%d", p.Address(), p.Port())
// Simplest case: it's already open, just return it.
if conn := h.localConns[key]; conn != nil {
return conn
}
service := strings.ToLower(p.Service())
portList := h.servicePorts[service]
if portList == nil {
loginfo.Println("cannot open connection for invalid service", service)
return nil
}
var hostname string
if service == "http" {
if match := hostRegexp.FindSubmatch(p.Data.Data()); match != nil {
hostname = strings.Split(string(match[1]), ":")[0]
}
} else if service == "https" {
hostname, _ = sni.GetHostname(p.Data.Data())
} else {
hostname = "*"
}
if hostname == "" {
loginfo.Println("missing servername for", service, key)
return nil
}
hostname = strings.ToLower(hostname)
port := portList[hostname]
if port == 0 {
port = portList["*"]
}
if port == 0 {
loginfo.Println("unable to determine local port for", service, hostname)
return nil
}
conn, err := net.Dial("tcp", fmt.Sprintf("127.0.0.1:%d", port))
if err != nil {
loginfo.Println("unable to open local connection on port", port, err)
return nil
}
h.localConns[key] = conn
loginfo.Printf("new client %q for %s:%d (%d clients)\n", key, hostname, port, len(h.localConns))
go h.readLocal(key, &p.Header)
return conn
}
func (h *WsHandler) writeLocal(p *packer.Packer) {
conn := h.getLocalConn(p)
if conn == nil {
h.sendPackedMessage(&p.Header, nil, "error")
return
}
if p.Service() == "error" || p.Service() == "end" {
conn.Close()
return
}
if _, err := conn.Write(p.Data.Data()); err != nil {
h.sendPackedMessage(&p.Header, nil, "error")
loginfo.Println("failed to write to local connection", err)
}
}
func (h *WsHandler) readLocal(key string, header *packer.Header) {
h.lock.Lock()
conn := h.localConns[key]
h.lock.Unlock()
defer conn.Close()
defer func() {
h.lock.Lock()
delete(h.localConns, key)
loginfo.Printf("closing client %q: (%d clients)\n", key, len(h.localConns))
h.lock.Unlock()
}()
buf := make([]byte, 4096)
for {
size, err := conn.Read(buf)
if err != nil {
if err == io.EOF || strings.Contains(err.Error(), "use of closed network connection") {
h.sendPackedMessage(header, nil, "end")
} else {
loginfo.Println("failed to read from local connection for", key, err)
h.sendPackedMessage(header, nil, "error")
}
return
}
h.sendPackedMessage(header, buf[:size], "")
}
}
func (h *WsHandler) closeConnections() {
h.lock.Lock()
defer h.lock.Unlock()
for _, conn := range h.localConns {
conn.Close()
}
}