cloudflare/cloudflared
Publicmirrored from https://github.com/cloudflare/cloudflaredAvailable
datagramsession/session.go
140lines · modecode
| 1 | package datagramsession |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "fmt" |
| 6 | "io" |
| 7 | "time" |
| 8 | |
| 9 | "github.com/google/uuid" |
| 10 | "github.com/rs/zerolog" |
| 11 | ) |
| 12 | |
| 13 | const ( |
| 14 | defaultCloseIdleAfter = time.Second * 210 |
| 15 | ) |
| 16 | |
| 17 | func SessionIdleErr(timeout time.Duration) error { |
| 18 | return fmt.Errorf("session idle for %v", timeout) |
| 19 | } |
| 20 | |
| 21 | // Session is a bidirectional pipe of datagrams between transport and dstConn |
| 22 | // Currently the only implementation of transport is quic DatagramMuxer |
| 23 | // Destination can be a connection with origin or with eyeball |
| 24 | // When the destination is origin: |
| 25 | // - Datagrams from edge are read by Manager from the transport. Manager finds the corresponding Session and calls the |
| 26 | // write method of the Session to send to origin |
| 27 | // - Datagrams from origin are read from conn and SentTo transport. Transport will return them to eyeball |
| 28 | // When the destination is eyeball: |
| 29 | // - Datagrams from eyeball are read from conn and SentTo transport. Transport will send them to cloudflared |
| 30 | // - Datagrams from cloudflared are read by Manager from the transport. Manager finds the corresponding Session and calls the |
| 31 | // write method of the Session to send to eyeball |
| 32 | type Session struct { |
| 33 | ID uuid.UUID |
| 34 | transport transport |
| 35 | dstConn io.ReadWriteCloser |
| 36 | // activeAtChan is used to communicate the last read/write time |
| 37 | activeAtChan chan time.Time |
| 38 | closeChan chan error |
| 39 | log *zerolog.Logger |
| 40 | } |
| 41 | |
| 42 | func newSession(id uuid.UUID, transport transport, dstConn io.ReadWriteCloser, log *zerolog.Logger) *Session { |
| 43 | return &Session{ |
| 44 | ID: id, |
| 45 | transport: transport, |
| 46 | dstConn: dstConn, |
| 47 | // activeAtChan has low capacity. It can be full when there are many concurrent read/write. markActive() will |
| 48 | // drop instead of blocking because last active time only needs to be an approximation |
| 49 | activeAtChan: make(chan time.Time, 2), |
| 50 | // capacity is 2 because close() and dstToTransport routine in Serve() can write to this channel |
| 51 | closeChan: make(chan error, 2), |
| 52 | log: log, |
| 53 | } |
| 54 | } |
| 55 | |
| 56 | func (s *Session) Serve(ctx context.Context, closeAfterIdle time.Duration) (closedByRemote bool, err error) { |
| 57 | go func() { |
| 58 | // QUIC implementation copies data to another buffer before returning https://github.com/lucas-clemente/quic-go/blob/v0.24.0/session.go#L1967-L1975 |
| 59 | // This makes it safe to share readBuffer between iterations |
| 60 | const maxPacketSize = 1500 |
| 61 | readBuffer := make([]byte, maxPacketSize) |
| 62 | for { |
| 63 | if err := s.dstToTransport(readBuffer); err != nil { |
| 64 | s.closeChan <- err |
| 65 | return |
| 66 | } |
| 67 | } |
| 68 | }() |
| 69 | err = s.waitForCloseCondition(ctx, closeAfterIdle) |
| 70 | if closeSession, ok := err.(*errClosedSession); ok { |
| 71 | closedByRemote = closeSession.byRemote |
| 72 | } |
| 73 | return closedByRemote, err |
| 74 | } |
| 75 | |
| 76 | func (s *Session) waitForCloseCondition(ctx context.Context, closeAfterIdle time.Duration) error { |
| 77 | // Closing dstConn cancels read so dstToTransport routine in Serve() can return |
| 78 | defer s.dstConn.Close() |
| 79 | if closeAfterIdle == 0 { |
| 80 | // provide deafult is caller doesn't specify one |
| 81 | closeAfterIdle = defaultCloseIdleAfter |
| 82 | } |
| 83 | |
| 84 | checkIdleFreq := closeAfterIdle / 8 |
| 85 | checkIdleTicker := time.NewTicker(checkIdleFreq) |
| 86 | defer checkIdleTicker.Stop() |
| 87 | |
| 88 | activeAt := time.Now() |
| 89 | for { |
| 90 | select { |
| 91 | case <-ctx.Done(): |
| 92 | return ctx.Err() |
| 93 | case reason := <-s.closeChan: |
| 94 | return reason |
| 95 | // TODO: TUN-5423 evaluate if using atomic is more efficient |
| 96 | case now := <-checkIdleTicker.C: |
| 97 | // The session is considered inactive if current time is after (last active time + allowed idle time) |
| 98 | if now.After(activeAt.Add(closeAfterIdle)) { |
| 99 | return SessionIdleErr(closeAfterIdle) |
| 100 | } |
| 101 | case activeAt = <-s.activeAtChan: // Update last active time |
| 102 | } |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | func (s *Session) dstToTransport(buffer []byte) error { |
| 107 | n, err := s.dstConn.Read(buffer) |
| 108 | s.markActive() |
| 109 | if n > 0 { |
| 110 | if n <= int(s.transport.MTU()) { |
| 111 | err = s.transport.SendTo(s.ID, buffer[:n]) |
| 112 | } else { |
| 113 | // drop packet for now, eventually reply with ICMP for PMTUD |
| 114 | s.log.Debug(). |
| 115 | Str("session", s.ID.String()). |
| 116 | Int("len", n). |
| 117 | Uint("mtu", s.transport.MTU()). |
| 118 | Msg("dropped packet exceeding MTU") |
| 119 | } |
| 120 | } |
| 121 | return err |
| 122 | } |
| 123 | |
| 124 | func (s *Session) transportToDst(payload []byte) (int, error) { |
| 125 | s.markActive() |
| 126 | return s.dstConn.Write(payload) |
| 127 | } |
| 128 | |
| 129 | // Sends the last active time to the idle checker loop without blocking. activeAtChan will only be full when there |
| 130 | // are many concurrent read/write. It is fine to lose some precision |
| 131 | func (s *Session) markActive() { |
| 132 | select { |
| 133 | case s.activeAtChan <- time.Now(): |
| 134 | default: |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | func (s *Session) close(err *errClosedSession) { |
| 139 | s.closeChan <- err |
| 140 | } |
| 141 | |