467 lines
10 KiB
Go
467 lines
10 KiB
Go
package tun2
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import (
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"bytes"
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"context"
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"encoding/json"
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"errors"
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"expvar"
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"fmt"
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"io"
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"io/ioutil"
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"math/rand"
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"net"
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"net/http"
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"os"
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"sync"
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"time"
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"github.com/Xe/ln"
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failure "github.com/dgryski/go-failure"
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"github.com/mtneug/pkg/ulid"
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cmap "github.com/streamrail/concurrent-map"
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"github.com/xtaci/smux"
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)
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// Error values
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var (
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ErrNoSuchBackend = errors.New("tun2: there is no such backend")
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ErrAuthMismatch = errors.New("tun2: authenication doesn't match database records")
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ErrCantRemoveWhatDoesntExist = errors.New("tun2: this connection does not exist, cannot remove it")
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)
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// gen502Page creates the page that is shown when a backend is not connected to a given route.
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func gen502Page(req *http.Request) *http.Response {
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template := `<html><head><title>no backends connected</title></head><body><h1>no backends connected</h1><p>Please ensure a backend is running for ${HOST}. This is request ID ${REQ_ID}.</p></body></html>`
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resbody := []byte(os.Expand(template, func(in string) string {
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switch in {
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case "HOST":
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return req.Host
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case "REQ_ID":
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return req.Header.Get("X-Request-Id")
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}
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return "<unknown>"
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}))
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reshdr := req.Header
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reshdr.Set("Content-Type", "text/html; charset=utf-8")
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resp := &http.Response{
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Status: fmt.Sprintf("%d Bad Gateway", http.StatusBadGateway),
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StatusCode: http.StatusBadGateway,
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Body: ioutil.NopCloser(bytes.NewBuffer(resbody)),
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Proto: req.Proto,
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ProtoMajor: req.ProtoMajor,
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ProtoMinor: req.ProtoMinor,
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Header: reshdr,
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ContentLength: int64(len(resbody)),
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Close: true,
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Request: req,
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}
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return resp
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}
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// ServerConfig ...
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type ServerConfig struct {
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SmuxConf *smux.Config
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Storage Storage
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}
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// Storage is the minimal subset of features that tun2's Server needs out of a
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// persistence layer.
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type Storage interface {
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HasToken(token string) (user string, scopes []string, err error)
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HasRoute(domain string) (user string, err error)
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}
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// Server routes frontend HTTP traffic to backend TCP traffic.
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type Server struct {
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cfg *ServerConfig
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ctx context.Context
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cancel context.CancelFunc
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connlock sync.Mutex
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conns map[net.Conn]*Connection
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domains cmap.ConcurrentMap
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}
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// NewServer creates a new Server instance with a given config, acquiring all
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// relevant resources.
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func NewServer(cfg *ServerConfig) (*Server, error) {
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if cfg == nil {
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return nil, errors.New("tun2: config must be specified")
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}
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if cfg.SmuxConf == nil {
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cfg.SmuxConf = smux.DefaultConfig()
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cfg.SmuxConf.KeepAliveInterval = time.Second
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cfg.SmuxConf.KeepAliveTimeout = 15 * time.Second
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}
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ctx, cancel := context.WithCancel(context.Background())
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server := &Server{
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cfg: cfg,
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conns: map[net.Conn]*Connection{},
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domains: cmap.New(),
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ctx: ctx,
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cancel: cancel,
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}
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go server.phiDetectionLoop(ctx)
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return server, nil
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}
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// Close stops the background tasks for this Server.
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func (s *Server) Close() {
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s.cancel()
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}
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// Wait blocks until the server context is cancelled.
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func (s *Server) Wait() {
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for {
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select {
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case <-s.ctx.Done():
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return
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}
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}
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}
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// Listen passes this Server a given net.Listener to accept backend connections.
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func (s *Server) Listen(l net.Listener, isKCP bool) {
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ctx := s.ctx
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f := ln.F{
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"listener_addr": l.Addr(),
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"listener_network": l.Addr().Network(),
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}
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for {
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select {
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case <-ctx.Done():
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return
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default:
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}
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conn, err := l.Accept()
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("accept connection"))
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continue
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}
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ln.Log(ctx, f, ln.Action("new backend client connected"), ln.F{
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"conn_addr": conn.RemoteAddr(),
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"conn_network": conn.RemoteAddr().Network(),
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})
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go s.HandleConn(conn, isKCP)
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}
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}
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// phiDetectionLoop is an infinite loop that will run the [phi accrual failure detector]
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// for each of the backends connected to the Server. This is fairly experimental and
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// may be removed.
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//
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// [phi accrual failure detector]: https://dspace.jaist.ac.jp/dspace/handle/10119/4784
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func (s *Server) phiDetectionLoop(ctx context.Context) {
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t := time.NewTicker(5 * time.Second)
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defer t.Stop()
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for {
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select {
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case <-ctx.Done():
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return
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case <-t.C:
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now := time.Now()
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s.connlock.Lock()
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for _, c := range s.conns {
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failureChance := c.detector.Phi(now)
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const thresh = 0.9 // the threshold for phi failure detection causing logs
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if failureChance > thresh {
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ln.Log(ctx, c, ln.Action("phi failure detection"), ln.F{
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"value": failureChance,
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"threshold": thresh,
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})
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}
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}
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s.connlock.Unlock()
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}
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}
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}
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// backendAuthv1 runs a simple backend authentication check. It expects the
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// client to write a json-encoded instance of Auth. This is then checked
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// for token validity and domain matching.
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//
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// This returns the user that was authenticated and the domain they identified
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// with.
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func (s *Server) backendAuthv1(ctx context.Context, st io.Reader) (string, *Auth, error) {
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f := ln.F{
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"action": "backend authentication",
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"backend_auth_version": 1,
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}
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f["stage"] = "json decoding"
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d := json.NewDecoder(st)
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var auth Auth
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err := d.Decode(&auth)
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if err != nil {
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ln.Error(ctx, err, f)
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return "", nil, err
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}
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f["auth_domain"] = auth.Domain
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f["stage"] = "checking domain"
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routeUser, err := s.cfg.Storage.HasRoute(auth.Domain)
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if err != nil {
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ln.Error(ctx, err, f)
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return "", nil, err
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}
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f["route_user"] = routeUser
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f["stage"] = "checking token"
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tokenUser, scopes, err := s.cfg.Storage.HasToken(auth.Token)
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if err != nil {
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ln.Error(ctx, err, f)
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return "", nil, err
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}
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f["token_user"] = tokenUser
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f["stage"] = "checking token scopes"
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ok := false
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for _, sc := range scopes {
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if sc == "connect" {
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ok = true
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break
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}
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}
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if !ok {
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ln.Error(ctx, ErrAuthMismatch, f)
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return "", nil, ErrAuthMismatch
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}
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f["stage"] = "user verification"
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if routeUser != tokenUser {
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ln.Error(ctx, ErrAuthMismatch, f)
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return "", nil, ErrAuthMismatch
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}
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return routeUser, &auth, nil
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}
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// HandleConn starts up the needed mechanisms to relay HTTP traffic to/from
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// the currently connected backend.
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func (s *Server) HandleConn(c net.Conn, isKCP bool) {
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defer c.Close()
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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f := ln.F{
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"local": c.LocalAddr().String(),
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"remote": c.RemoteAddr().String(),
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}
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session, err := smux.Server(c, s.cfg.SmuxConf)
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("establish server side of smux"))
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return
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}
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defer session.Close()
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controlStream, err := session.OpenStream()
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if err != nil {
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ln.Error(ctx, err, f, ln.Action("opening control stream"))
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return
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}
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defer controlStream.Close()
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user, auth, err := s.backendAuthv1(ctx, controlStream)
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if err != nil {
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return
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}
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connection := &Connection{
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id: ulid.New().String(),
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conn: c,
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isKCP: isKCP,
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session: session,
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user: user,
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domain: auth.Domain,
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cf: cancel,
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detector: failure.New(15, 1),
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Auth: auth,
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}
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connection.counter = expvar.NewInt("http.backend." + connection.id + ".hits")
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defer func() {
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if r := recover(); r != nil {
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ln.Log(ctx, connection, ln.F{"action": "connection handler panic", "err": r})
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}
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}()
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ln.Log(ctx, connection, ln.Action("backend successfully connected"))
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s.addConn(ctx, connection)
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connection.usable = true // XXX set this to true once health checks pass?
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ticker := time.NewTicker(5 * time.Second)
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defer ticker.Stop()
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for {
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select {
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case <-ticker.C:
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err := connection.Ping()
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if err != nil {
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connection.cancel()
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}
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// case <-s.ctx.Done():
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// ln.Log(ctx, connection, ln.Action("server context finished"))
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// s.removeConn(ctx, connection)
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// connection.Close()
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// return
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case <-ctx.Done():
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ln.Log(ctx, connection, ln.Action("client context finished"))
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s.removeConn(ctx, connection)
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connection.Close()
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return
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}
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}
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}
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// addConn adds a connection to the pool of backend connections.
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func (s *Server) addConn(ctx context.Context, connection *Connection) {
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s.connlock.Lock()
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s.conns[connection.conn] = connection
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s.connlock.Unlock()
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var conns []*Connection
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val, ok := s.domains.Get(connection.domain)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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conns = nil
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s.domains.Remove(connection.domain)
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}
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}
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conns = append(conns, connection)
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s.domains.Set(connection.domain, conns)
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}
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// removeConn removes a connection from pool of backend connections.
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func (s *Server) removeConn(ctx context.Context, connection *Connection) {
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s.connlock.Lock()
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delete(s.conns, connection.conn)
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s.connlock.Unlock()
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auth := connection.Auth
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var conns []*Connection
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val, ok := s.domains.Get(auth.Domain)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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ln.Error(ctx, ErrCantRemoveWhatDoesntExist, connection, ln.Action("looking up for disconnect removal"))
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return
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}
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}
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for i, cntn := range conns {
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if cntn.id == connection.id {
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conns[i] = conns[len(conns)-1]
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conns = conns[:len(conns)-1]
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}
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}
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if len(conns) != 0 {
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s.domains.Set(auth.Domain, conns)
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} else {
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s.domains.Remove(auth.Domain)
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}
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}
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// RoundTrip sends a HTTP request to a backend and then returns its response.
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func (s *Server) RoundTrip(req *http.Request) (*http.Response, error) {
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var conns []*Connection
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ctx := req.Context()
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f := ln.F{
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"remote": req.RemoteAddr,
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"host": req.Host,
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"uri": req.RequestURI,
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}
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val, ok := s.domains.Get(req.Host)
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if ok {
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conns, ok = val.([]*Connection)
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if !ok {
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ln.Error(ctx, ErrNoSuchBackend, f, ln.Action("no backend available"))
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return gen502Page(req), nil
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}
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}
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var goodConns []*Connection
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for _, conn := range conns {
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if conn.usable {
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goodConns = append(goodConns, conn)
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}
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}
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if len(goodConns) == 0 {
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ln.Error(ctx, ErrNoSuchBackend, f, ln.Action("no good backends available"))
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return gen502Page(req), nil
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}
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c := goodConns[rand.Intn(len(goodConns))]
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resp, err := c.RoundTrip(req)
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if err != nil {
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ln.Error(ctx, err, c, f, ln.Action("connection roundtrip"))
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defer c.cancel()
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return nil, err
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}
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ln.Log(ctx, c, ln.Action("http traffic"), f, ln.F{
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"status": resp.Status,
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"status_code": resp.StatusCode,
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"content_length": resp.ContentLength,
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})
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return resp, nil
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}
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// Auth is the authentication info the client passes to the server.
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type Auth struct {
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Token string `json:"token"`
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Domain string `json:"domain"`
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}
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