1 4b33cdd0 2015-11-30 stephen.d package p9p
3 4b33cdd0 2015-11-30 stephen.d import (
5 4b33cdd0 2015-11-30 stephen.d "encoding/binary"
8 4b33cdd0 2015-11-30 stephen.d "io/ioutil"
13 4b33cdd0 2015-11-30 stephen.d "golang.org/x/net/context"
16 4b33cdd0 2015-11-30 stephen.d // Channel defines the operations necessary to implement a 9p message channel
17 4b33cdd0 2015-11-30 stephen.d // interface. Typically, message channels do no protocol processing except to
18 4b33cdd0 2015-11-30 stephen.d // send and receive message frames.
19 4b33cdd0 2015-11-30 stephen.d type Channel interface {
20 4b33cdd0 2015-11-30 stephen.d // ReadFcall reads one fcall frame into the provided fcall structure. The
21 4b33cdd0 2015-11-30 stephen.d // Fcall may be cleared whether there is an error or not. If the operation
22 4b33cdd0 2015-11-30 stephen.d // is successful, the contents of the fcall will be populated in the
23 4b33cdd0 2015-11-30 stephen.d // argument. ReadFcall cannot be called concurrently with other calls to
24 4b33cdd0 2015-11-30 stephen.d // ReadFcall. This both to preserve message ordering and to allow lockless
25 4b33cdd0 2015-11-30 stephen.d // buffer reusage.
26 4b33cdd0 2015-11-30 stephen.d ReadFcall(ctx context.Context, fcall *Fcall) error
28 4b33cdd0 2015-11-30 stephen.d // WriteFcall writes the provided fcall to the channel. WriteFcall cannot
29 4b33cdd0 2015-11-30 stephen.d // be called concurrently with other calls to WriteFcall.
30 4b33cdd0 2015-11-30 stephen.d WriteFcall(ctx context.Context, fcall *Fcall) error
32 4b33cdd0 2015-11-30 stephen.d // MSize returns the current msize for the channel.
33 4b33cdd0 2015-11-30 stephen.d MSize() int
35 4b33cdd0 2015-11-30 stephen.d // SetMSize sets the maximum message size for the channel. This must never
36 4b33cdd0 2015-11-30 stephen.d // be called currently with ReadFcall or WriteFcall.
37 4b33cdd0 2015-11-30 stephen.d SetMSize(msize int)
40 4b33cdd0 2015-11-30 stephen.d func NewChannel(conn net.Conn, msize int) Channel {
41 4b33cdd0 2015-11-30 stephen.d return newChannel(conn, codec9p{}, msize)
44 4b33cdd0 2015-11-30 stephen.d const (
45 e797c539 2016-05-18 stevvooe defaultRWTimeout = 30 * time.Second // default read/write timeout if not set in context
48 4b33cdd0 2015-11-30 stephen.d // channel provides bidirectional protocol framing for 9p over net.Conn.
49 4b33cdd0 2015-11-30 stephen.d // Operations are not thread-safe but reads and writes may be carried out
50 4b33cdd0 2015-11-30 stephen.d // concurrently, supporting separate read and write loops.
52 4b33cdd0 2015-11-30 stephen.d // Lifecyle
54 4b33cdd0 2015-11-30 stephen.d // A connection, or message channel abstraction, has a lifecycle delineated by
55 4b33cdd0 2015-11-30 stephen.d // Tversion/Rversion request response cycles. For now, this is part of the
56 4b33cdd0 2015-11-30 stephen.d // channel itself but doesn't necessarily influence the channels state, except
57 4b33cdd0 2015-11-30 stephen.d // the msize. Visually, it might look something like this:
59 4b33cdd0 2015-11-30 stephen.d // [Established] -> [Version] -> [Session] -> [Version]---+
61 4b33cdd0 2015-11-30 stephen.d // |_________________________________|
63 4b33cdd0 2015-11-30 stephen.d // The connection is established, then we negotiate a version, run a session,
64 4b33cdd0 2015-11-30 stephen.d // then negotiate a version and so on. For most purposes, we are likely going
65 4b33cdd0 2015-11-30 stephen.d // to terminate the connection after the session but we may want to support
66 4b33cdd0 2015-11-30 stephen.d // connection pooling. Pooling may result in possible security leaks if the
67 4b33cdd0 2015-11-30 stephen.d // connections are shared among contexts, since the version is negotiated at
68 4b33cdd0 2015-11-30 stephen.d // the start of the session. To avoid this, we can actually use a "tombstone"
69 4b33cdd0 2015-11-30 stephen.d // version message which clears the server's session state without starting a
70 4b33cdd0 2015-11-30 stephen.d // new session. The next version message would then prepare the session
71 4b33cdd0 2015-11-30 stephen.d // without leaking any Fid's.
72 4b33cdd0 2015-11-30 stephen.d type channel struct {
73 4b33cdd0 2015-11-30 stephen.d conn net.Conn
74 4b33cdd0 2015-11-30 stephen.d codec Codec
75 4b33cdd0 2015-11-30 stephen.d brd *bufio.Reader
76 4b33cdd0 2015-11-30 stephen.d bwr *bufio.Writer
77 4b33cdd0 2015-11-30 stephen.d closed chan struct{}
78 4b33cdd0 2015-11-30 stephen.d msize int
79 4b33cdd0 2015-11-30 stephen.d rdbuf []byte
82 4b33cdd0 2015-11-30 stephen.d func newChannel(conn net.Conn, codec Codec, msize int) *channel {
83 4b33cdd0 2015-11-30 stephen.d return &channel{
84 4b33cdd0 2015-11-30 stephen.d conn: conn,
85 4b33cdd0 2015-11-30 stephen.d codec: codec,
86 4b33cdd0 2015-11-30 stephen.d brd: bufio.NewReaderSize(conn, msize), // msize may not be optimal buffer size
87 4b33cdd0 2015-11-30 stephen.d bwr: bufio.NewWriterSize(conn, msize),
88 4b33cdd0 2015-11-30 stephen.d closed: make(chan struct{}),
89 4b33cdd0 2015-11-30 stephen.d msize: msize,
90 4b33cdd0 2015-11-30 stephen.d rdbuf: make([]byte, msize),
94 4b33cdd0 2015-11-30 stephen.d func (ch *channel) MSize() int {
95 4b33cdd0 2015-11-30 stephen.d return ch.msize
98 4b33cdd0 2015-11-30 stephen.d // setmsize resizes the buffers for use with a separate msize. This call must
99 4b33cdd0 2015-11-30 stephen.d // be protected by a mutex or made before passing to other goroutines.
100 4b33cdd0 2015-11-30 stephen.d func (ch *channel) SetMSize(msize int) {
101 4b33cdd0 2015-11-30 stephen.d // NOTE(stevvooe): We cannot safely resize the buffered reader and writer.
102 4b33cdd0 2015-11-30 stephen.d // Proceed assuming that original size is sufficient.
104 4b33cdd0 2015-11-30 stephen.d ch.msize = msize
105 4b33cdd0 2015-11-30 stephen.d if msize < len(ch.rdbuf) {
106 4b33cdd0 2015-11-30 stephen.d // just change the cap
107 4b33cdd0 2015-11-30 stephen.d ch.rdbuf = ch.rdbuf[:msize]
108 4b33cdd0 2015-11-30 stephen.d return
111 4b33cdd0 2015-11-30 stephen.d ch.rdbuf = make([]byte, msize)
114 4b33cdd0 2015-11-30 stephen.d // ReadFcall reads the next message from the channel into fcall.
115 4b33cdd0 2015-11-30 stephen.d func (ch *channel) ReadFcall(ctx context.Context, fcall *Fcall) error {
116 4b33cdd0 2015-11-30 stephen.d select {
117 4b33cdd0 2015-11-30 stephen.d case <-ctx.Done():
118 4b33cdd0 2015-11-30 stephen.d return ctx.Err()
119 4b33cdd0 2015-11-30 stephen.d case <-ch.closed:
120 4b33cdd0 2015-11-30 stephen.d return ErrClosed
121 4b33cdd0 2015-11-30 stephen.d default:
124 4b33cdd0 2015-11-30 stephen.d deadline, ok := ctx.Deadline()
125 4b33cdd0 2015-11-30 stephen.d if !ok {
126 4b33cdd0 2015-11-30 stephen.d deadline = time.Now().Add(defaultRWTimeout)
129 4b33cdd0 2015-11-30 stephen.d if err := ch.conn.SetReadDeadline(deadline); err != nil {
130 4b33cdd0 2015-11-30 stephen.d log.Printf("transport: error setting read deadline on %v: %v", ch.conn.RemoteAddr(), err)
133 4b33cdd0 2015-11-30 stephen.d n, err := readmsg(ch.brd, ch.rdbuf)
134 4b33cdd0 2015-11-30 stephen.d if err != nil {
135 4b33cdd0 2015-11-30 stephen.d // TODO(stevvooe): There may be more we can do here to detect partial
136 4b33cdd0 2015-11-30 stephen.d // reads. For now, we just propagate the error untouched.
137 4b33cdd0 2015-11-30 stephen.d return err
140 4b33cdd0 2015-11-30 stephen.d if n > len(ch.rdbuf) {
141 4b33cdd0 2015-11-30 stephen.d // TODO(stevvooe): Make this error detectable and respond with error
142 4b33cdd0 2015-11-30 stephen.d // message.
143 4b33cdd0 2015-11-30 stephen.d return fmt.Errorf("message large than buffer:", n)
146 4b33cdd0 2015-11-30 stephen.d // clear out the fcall
147 4b33cdd0 2015-11-30 stephen.d *fcall = Fcall{}
148 4b33cdd0 2015-11-30 stephen.d if err := ch.codec.Unmarshal(ch.rdbuf[:n], fcall); err != nil {
149 4b33cdd0 2015-11-30 stephen.d return err
152 4b33cdd0 2015-11-30 stephen.d return nil
155 4b33cdd0 2015-11-30 stephen.d func (ch *channel) WriteFcall(ctx context.Context, fcall *Fcall) error {
156 4b33cdd0 2015-11-30 stephen.d select {
157 4b33cdd0 2015-11-30 stephen.d case <-ctx.Done():
158 4b33cdd0 2015-11-30 stephen.d return ctx.Err()
159 4b33cdd0 2015-11-30 stephen.d case <-ch.closed:
160 4b33cdd0 2015-11-30 stephen.d return ErrClosed
161 4b33cdd0 2015-11-30 stephen.d default:
164 4b33cdd0 2015-11-30 stephen.d deadline, ok := ctx.Deadline()
165 4b33cdd0 2015-11-30 stephen.d if !ok {
166 4b33cdd0 2015-11-30 stephen.d deadline = time.Now().Add(defaultRWTimeout)
169 4b33cdd0 2015-11-30 stephen.d if err := ch.conn.SetWriteDeadline(deadline); err != nil {
170 4b33cdd0 2015-11-30 stephen.d log.Printf("transport: error setting read deadline on %v: %v", ch.conn.RemoteAddr(), err)
173 4b33cdd0 2015-11-30 stephen.d p, err := ch.codec.Marshal(fcall)
174 4b33cdd0 2015-11-30 stephen.d if err != nil {
175 4b33cdd0 2015-11-30 stephen.d return err
178 4b33cdd0 2015-11-30 stephen.d if err := sendmsg(ch.bwr, p); err != nil {
179 4b33cdd0 2015-11-30 stephen.d return err
182 4b33cdd0 2015-11-30 stephen.d return ch.bwr.Flush()
185 4b33cdd0 2015-11-30 stephen.d // readmsg reads a 9p message into p from rd, ensuring that all bytes are
186 4b33cdd0 2015-11-30 stephen.d // consumed from the size header. If the size header indicates the message is
187 4b33cdd0 2015-11-30 stephen.d // larger than p, the entire message will be discarded, leaving a truncated
188 4b33cdd0 2015-11-30 stephen.d // portion in p. Any error should be treated as a framing error unless n is
189 4b33cdd0 2015-11-30 stephen.d // zero. The caller must check that n is less than or equal to len(p) to
190 4b33cdd0 2015-11-30 stephen.d // ensure that a valid message has been read.
191 4b33cdd0 2015-11-30 stephen.d func readmsg(rd io.Reader, p []byte) (n int, err error) {
192 4b33cdd0 2015-11-30 stephen.d var msize uint32
194 4b33cdd0 2015-11-30 stephen.d if err := binary.Read(rd, binary.LittleEndian, &msize); err != nil {
195 4b33cdd0 2015-11-30 stephen.d return 0, err
198 4b33cdd0 2015-11-30 stephen.d n += binary.Size(msize)
199 4b33cdd0 2015-11-30 stephen.d mbody := int(msize) - 4
201 4b33cdd0 2015-11-30 stephen.d if mbody < len(p) {
202 4b33cdd0 2015-11-30 stephen.d p = p[:mbody]
205 4b33cdd0 2015-11-30 stephen.d np, err := io.ReadFull(rd, p)
206 4b33cdd0 2015-11-30 stephen.d if err != nil {
207 4b33cdd0 2015-11-30 stephen.d return np + n, err
209 4b33cdd0 2015-11-30 stephen.d n += np
211 4b33cdd0 2015-11-30 stephen.d if mbody > len(p) {
212 4b33cdd0 2015-11-30 stephen.d // message has been read up to len(p) but we must consume the entire
213 4b33cdd0 2015-11-30 stephen.d // message. This is an error condition but is non-fatal if we can
214 4b33cdd0 2015-11-30 stephen.d // consume msize bytes.
215 4b33cdd0 2015-11-30 stephen.d nn, err := io.CopyN(ioutil.Discard, rd, int64(mbody-len(p)))
216 4b33cdd0 2015-11-30 stephen.d n += int(nn)
217 4b33cdd0 2015-11-30 stephen.d if err != nil {
218 4b33cdd0 2015-11-30 stephen.d return n, err
222 4b33cdd0 2015-11-30 stephen.d return n, nil
225 4b33cdd0 2015-11-30 stephen.d // sendmsg writes a message of len(p) to wr with a 9p size header. All errors
226 4b33cdd0 2015-11-30 stephen.d // should be considered terminal.
227 4b33cdd0 2015-11-30 stephen.d func sendmsg(wr io.Writer, p []byte) error {
228 4b33cdd0 2015-11-30 stephen.d size := uint32(len(p) + 4) // message size plus 4-bytes for size.
229 4b33cdd0 2015-11-30 stephen.d if err := binary.Write(wr, binary.LittleEndian, size); err != nil {
230 5eb5d0b1 2016-05-19 stevvooe return err
233 4b33cdd0 2015-11-30 stephen.d // This assume partial writes to wr aren't possible. Not sure if this
234 4b33cdd0 2015-11-30 stephen.d // valid. Matters during timeout retries.
235 4b33cdd0 2015-11-30 stephen.d if n, err := wr.Write(p); err != nil {
236 4b33cdd0 2015-11-30 stephen.d return err
237 4b33cdd0 2015-11-30 stephen.d } else if n < len(p) {
238 4b33cdd0 2015-11-30 stephen.d return io.ErrShortWrite
241 4b33cdd0 2015-11-30 stephen.d return nil
