Commit f11222a9 authored by Alexandre Viau's avatar Alexandre Viau

New upstream version 0.0~git20171107.1f58ded

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# Yamux
Yamux (Yet another Multiplexer) is a multiplexing library for Golang.
It relies on an underlying connection to provide reliability
and ordering, such as TCP or Unix domain sockets, and provides
stream-oriented multiplexing. It is inspired by SPDY but is not
interoperable with it.
Yamux features include:
* Bi-directional streams
* Streams can be opened by either client or server
* Useful for NAT traversal
* Server-side push support
* Flow control
* Avoid starvation
* Back-pressure to prevent overwhelming a receiver
* Keep Alives
* Enables persistent connections over a load balancer
* Efficient
* Enables thousands of logical streams with low overhead
## Documentation
For complete documentation, see the associated [Godoc](http://godoc.org/github.com/hashicorp/yamux).
## Specification
The full specification for Yamux is provided in the `spec.md` file.
It can be used as a guide to implementors of interoperable libraries.
## Usage
Using Yamux is remarkably simple:
```go
func client() {
// Get a TCP connection
conn, err := net.Dial(...)
if err != nil {
panic(err)
}
// Setup client side of yamux
session, err := yamux.Client(conn, nil)
if err != nil {
panic(err)
}
// Open a new stream
stream, err := session.Open()
if err != nil {
panic(err)
}
// Stream implements net.Conn
stream.Write([]byte("ping"))
}
func server() {
// Accept a TCP connection
conn, err := listener.Accept()
if err != nil {
panic(err)
}
// Setup server side of yamux
session, err := yamux.Server(conn, nil)
if err != nil {
panic(err)
}
// Accept a stream
stream, err := session.Accept()
if err != nil {
panic(err)
}
// Listen for a message
buf := make([]byte, 4)
stream.Read(buf)
}
```
package yamux
import (
"fmt"
"net"
)
// hasAddr is used to get the address from the underlying connection
type hasAddr interface {
LocalAddr() net.Addr
RemoteAddr() net.Addr
}
// yamuxAddr is used when we cannot get the underlying address
type yamuxAddr struct {
Addr string
}
func (*yamuxAddr) Network() string {
return "yamux"
}
func (y *yamuxAddr) String() string {
return fmt.Sprintf("yamux:%s", y.Addr)
}
// Addr is used to get the address of the listener.
func (s *Session) Addr() net.Addr {
return s.LocalAddr()
}
// LocalAddr is used to get the local address of the
// underlying connection.
func (s *Session) LocalAddr() net.Addr {
addr, ok := s.conn.(hasAddr)
if !ok {
return &yamuxAddr{"local"}
}
return addr.LocalAddr()
}
// RemoteAddr is used to get the address of remote end
// of the underlying connection
func (s *Session) RemoteAddr() net.Addr {
addr, ok := s.conn.(hasAddr)
if !ok {
return &yamuxAddr{"remote"}
}
return addr.RemoteAddr()
}
// LocalAddr returns the local address
func (s *Stream) LocalAddr() net.Addr {
return s.session.LocalAddr()
}
// LocalAddr returns the remote address
func (s *Stream) RemoteAddr() net.Addr {
return s.session.RemoteAddr()
}
package yamux
import (
"testing"
)
func BenchmarkPing(b *testing.B) {
client, server := testClientServer()
defer client.Close()
defer server.Close()
for i := 0; i < b.N; i++ {
rtt, err := client.Ping()
if err != nil {
b.Fatalf("err: %v", err)
}
if rtt == 0 {
b.Fatalf("bad: %v", rtt)
}
}
}
func BenchmarkAccept(b *testing.B) {
client, server := testClientServer()
defer client.Close()
defer server.Close()
go func() {
for i := 0; i < b.N; i++ {
stream, err := server.AcceptStream()
if err != nil {
return
}
stream.Close()
}
}()
for i := 0; i < b.N; i++ {
stream, err := client.Open()
if err != nil {
b.Fatalf("err: %v", err)
}
stream.Close()
}
}
func BenchmarkSendRecv(b *testing.B) {
client, server := testClientServer()
defer client.Close()
defer server.Close()
sendBuf := make([]byte, 512)
recvBuf := make([]byte, 512)
doneCh := make(chan struct{})
go func() {
stream, err := server.AcceptStream()
if err != nil {
return
}
defer stream.Close()
for i := 0; i < b.N; i++ {
if _, err := stream.Read(recvBuf); err != nil {
b.Fatalf("err: %v", err)
}
}
close(doneCh)
}()
stream, err := client.Open()
if err != nil {
b.Fatalf("err: %v", err)
}
defer stream.Close()
for i := 0; i < b.N; i++ {
if _, err := stream.Write(sendBuf); err != nil {
b.Fatalf("err: %v", err)
}
}
<-doneCh
}
func BenchmarkSendRecvLarge(b *testing.B) {
client, server := testClientServer()
defer client.Close()
defer server.Close()
const sendSize = 100 * 1024 * 1024
const recvSize = 4 * 1024
sendBuf := make([]byte, sendSize)
recvBuf := make([]byte, recvSize)
b.ResetTimer()
recvDone := make(chan struct{})
go func() {
stream, err := server.AcceptStream()
if err != nil {
return
}
defer stream.Close()
for i := 0; i < b.N; i++ {
for j := 0; j < sendSize/recvSize; j++ {
if _, err := stream.Read(recvBuf); err != nil {
b.Fatalf("err: %v", err)
}
}
}
close(recvDone)
}()
stream, err := client.Open()
if err != nil {
b.Fatalf("err: %v", err)
}
defer stream.Close()
for i := 0; i < b.N; i++ {
if _, err := stream.Write(sendBuf); err != nil {
b.Fatalf("err: %v", err)
}
}
<-recvDone
}
package yamux
import (
"encoding/binary"
"fmt"
)
var (
// ErrInvalidVersion means we received a frame with an
// invalid version
ErrInvalidVersion = fmt.Errorf("invalid protocol version")
// ErrInvalidMsgType means we received a frame with an
// invalid message type
ErrInvalidMsgType = fmt.Errorf("invalid msg type")
// ErrSessionShutdown is used if there is a shutdown during
// an operation
ErrSessionShutdown = fmt.Errorf("session shutdown")
// ErrStreamsExhausted is returned if we have no more
// stream ids to issue
ErrStreamsExhausted = fmt.Errorf("streams exhausted")
// ErrDuplicateStream is used if a duplicate stream is
// opened inbound
ErrDuplicateStream = fmt.Errorf("duplicate stream initiated")
// ErrReceiveWindowExceeded indicates the window was exceeded
ErrRecvWindowExceeded = fmt.Errorf("recv window exceeded")
// ErrTimeout is used when we reach an IO deadline
ErrTimeout = fmt.Errorf("i/o deadline reached")
// ErrStreamClosed is returned when using a closed stream
ErrStreamClosed = fmt.Errorf("stream closed")
// ErrUnexpectedFlag is set when we get an unexpected flag
ErrUnexpectedFlag = fmt.Errorf("unexpected flag")
// ErrRemoteGoAway is used when we get a go away from the other side
ErrRemoteGoAway = fmt.Errorf("remote end is not accepting connections")
// ErrConnectionReset is sent if a stream is reset. This can happen
// if the backlog is exceeded, or if there was a remote GoAway.
ErrConnectionReset = fmt.Errorf("connection reset")
// ErrConnectionWriteTimeout indicates that we hit the "safety valve"
// timeout writing to the underlying stream connection.
ErrConnectionWriteTimeout = fmt.Errorf("connection write timeout")
// ErrKeepAliveTimeout is sent if a missed keepalive caused the stream close
ErrKeepAliveTimeout = fmt.Errorf("keepalive timeout")
)
const (
// protoVersion is the only version we support
protoVersion uint8 = 0
)
const (
// Data is used for data frames. They are followed
// by length bytes worth of payload.
typeData uint8 = iota
// WindowUpdate is used to change the window of
// a given stream. The length indicates the delta
// update to the window.
typeWindowUpdate
// Ping is sent as a keep-alive or to measure
// the RTT. The StreamID and Length value are echoed
// back in the response.
typePing
// GoAway is sent to terminate a session. The StreamID
// should be 0 and the length is an error code.
typeGoAway
// typeMax defines the upper bound of valid message types
// and should always be the last constant.
typeMax
)
const (
// SYN is sent to signal a new stream. May
// be sent with a data payload
flagSYN uint16 = 1 << iota
// ACK is sent to acknowledge a new stream. May
// be sent with a data payload
flagACK
// FIN is sent to half-close the given stream.
// May be sent with a data payload.
flagFIN
// RST is used to hard close a given stream.
flagRST
)
const (
// initialStreamWindow is the initial stream window size
initialStreamWindow uint32 = 256 * 1024
)
const (
// goAwayNormal is sent on a normal termination
goAwayNormal uint32 = iota
// goAwayProtoErr sent on a protocol error
goAwayProtoErr
// goAwayInternalErr sent on an internal error
goAwayInternalErr
)
const (
sizeOfVersion = 1
sizeOfType = 1
sizeOfFlags = 2
sizeOfStreamID = 4
sizeOfLength = 4
headerSize = sizeOfVersion + sizeOfType + sizeOfFlags +
sizeOfStreamID + sizeOfLength
)
type header []byte
func (h header) Version() uint8 {
return h[0]
}
func (h header) MsgType() uint8 {
return h[1]
}
func (h header) Flags() uint16 {
return binary.BigEndian.Uint16(h[2:4])
}
func (h header) StreamID() uint32 {
return binary.BigEndian.Uint32(h[4:8])
}
func (h header) Length() uint32 {
return binary.BigEndian.Uint32(h[8:12])
}
func (h header) String() string {
return fmt.Sprintf("Vsn:%d Type:%d Flags:%d StreamID:%d Length:%d",
h.Version(), h.MsgType(), h.Flags(), h.StreamID(), h.Length())
}
func (h header) encode(msgType uint8, flags uint16, streamID uint32, length uint32) {
h[0] = protoVersion
h[1] = msgType
binary.BigEndian.PutUint16(h[2:4], flags)
binary.BigEndian.PutUint32(h[4:8], streamID)
binary.BigEndian.PutUint32(h[8:12], length)
}
package yamux
import (
"testing"
)
func TestConst(t *testing.T) {
if protoVersion != 0 {
t.Fatalf("bad: %v", protoVersion)
}
if typeData != 0 {
t.Fatalf("bad: %v", typeData)
}
if typeWindowUpdate != 1 {
t.Fatalf("bad: %v", typeWindowUpdate)
}
if typePing != 2 {
t.Fatalf("bad: %v", typePing)
}
if typeGoAway != 3 {
t.Fatalf("bad: %v", typeGoAway)
}
if flagSYN != 1 {
t.Fatalf("bad: %v", flagSYN)
}
if flagACK != 2 {
t.Fatalf("bad: %v", flagACK)
}
if flagFIN != 4 {
t.Fatalf("bad: %v", flagFIN)
}
if flagRST != 8 {
t.Fatalf("bad: %v", flagRST)
}
if goAwayNormal != 0 {
t.Fatalf("bad: %v", goAwayNormal)
}
if goAwayProtoErr != 1 {
t.Fatalf("bad: %v", goAwayProtoErr)
}
if goAwayInternalErr != 2 {
t.Fatalf("bad: %v", goAwayInternalErr)
}
if headerSize != 12 {
t.Fatalf("bad header size")
}
}
func TestEncodeDecode(t *testing.T) {
hdr := header(make([]byte, headerSize))
hdr.encode(typeWindowUpdate, flagACK|flagRST, 1234, 4321)
if hdr.Version() != protoVersion {
t.Fatalf("bad: %v", hdr)
}
if hdr.MsgType() != typeWindowUpdate {
t.Fatalf("bad: %v", hdr)
}
if hdr.Flags() != flagACK|flagRST {
t.Fatalf("bad: %v", hdr)
}
if hdr.StreamID() != 1234 {
t.Fatalf("bad: %v", hdr)
}
if hdr.Length() != 4321 {
t.Fatalf("bad: %v", hdr)
}
}
package yamux
import (
"fmt"
"io"
"os"
"time"
)
// Config is used to tune the Yamux session
type Config struct {
// AcceptBacklog is used to limit how many streams may be
// waiting an accept.
AcceptBacklog int
// EnableKeepalive is used to do a period keep alive
// messages using a ping.
EnableKeepAlive bool
// KeepAliveInterval is how often to perform the keep alive
KeepAliveInterval time.Duration
// ConnectionWriteTimeout is meant to be a "safety valve" timeout after
// we which will suspect a problem with the underlying connection and
// close it. This is only applied to writes, where's there's generally
// an expectation that things will move along quickly.
ConnectionWriteTimeout time.Duration
// MaxStreamWindowSize is used to control the maximum
// window size that we allow for a stream.
MaxStreamWindowSize uint32
// LogOutput is used to control the log destination
LogOutput io.Writer
}
// DefaultConfig is used to return a default configuration
func DefaultConfig() *Config {
return &Config{
AcceptBacklog: 256,
EnableKeepAlive: true,
KeepAliveInterval: 30 * time.Second,
ConnectionWriteTimeout: 10 * time.Second,
MaxStreamWindowSize: initialStreamWindow,
LogOutput: os.Stderr,
}
}
// VerifyConfig is used to verify the sanity of configuration
func VerifyConfig(config *Config) error {
if config.AcceptBacklog <= 0 {
return fmt.Errorf("backlog must be positive")
}
if config.KeepAliveInterval == 0 {
return fmt.Errorf("keep-alive interval must be positive")
}
if config.MaxStreamWindowSize < initialStreamWindow {
return fmt.Errorf("MaxStreamWindowSize must be larger than %d", initialStreamWindow)
}
return nil
}
// Server is used to initialize a new server-side connection.
// There must be at most one server-side connection. If a nil config is
// provided, the DefaultConfiguration will be used.
func Server(conn io.ReadWriteCloser, config *Config) (*Session, error) {
if config == nil {
config = DefaultConfig()
}
if err := VerifyConfig(config); err != nil {
return nil, err
}
return newSession(config, conn, false), nil
}
// Client is used to initialize a new client-side connection.
// There must be at most one client-side connection.
func Client(conn io.ReadWriteCloser, config *Config) (*Session, error) {
if config == nil {
config = DefaultConfig()
}
if err := VerifyConfig(config); err != nil {
return nil, err
}
return newSession(config, conn, true), nil
}
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# Specification
We use this document to detail the internal specification of Yamux.
This is used both as a guide for implementing Yamux, but also for
alternative interoperable libraries to be built.
# Framing
Yamux uses a streaming connection underneath, but imposes a message
framing so that it can be shared between many logical streams. Each
frame contains a header like:
* Version (8 bits)
* Type (8 bits)
* Flags (16 bits)
* StreamID (32 bits)
* Length (32 bits)
This means that each header has a 12 byte overhead.
All fields are encoded in network order (big endian).
Each field is described below:
## Version Field
The version field is used for future backward compatibility. At the
current time, the field is always set to 0, to indicate the initial
version.
## Type Field
The type field is used to switch the frame message type. The following
message types are supported:
* 0x0 Data - Used to transmit data. May transmit zero length payloads
depending on the flags.
* 0x1 Window Update - Used to updated the senders receive window size.
This is used to implement per-session flow control.
* 0x2 Ping - Used to measure RTT. It can also be used to heart-beat
and do keep-alives over TCP.
* 0x3 Go Away - Used to close a session.
## Flag Field
The flags field is used to provide additional information related
to the message type. The following flags are supported:
* 0x1 SYN - Signals the start of a new stream. May be sent with a data or
window update message. Also sent with a ping to indicate outbound.
* 0x2 ACK - Acknowledges the start of a new stream. May be sent with a data
or window update message. Also sent with a ping to indicate response.
* 0x4 FIN - Performs a half-close of a stream. May be sent with a data
message or window update.
* 0x8 RST - Reset a stream immediately. May be sent with a data or
window update message.
## StreamID Field
The StreamID field is used to identify the logical stream the frame
is addressing. The client side should use odd ID's, and the server even.
This prevents any collisions. Additionally, the 0 ID is reserved to represent
the session.
Both Ping and Go Away messages should always use the 0 StreamID.
## Length Field
The meaning of the length field depends on the message type:
* Data - provides the length of bytes following the header
* Window update - provides a delta update to the window size
* Ping - Contains an opaque value, echoed back
* Go Away - Contains an error code
# Message Flow
There is no explicit connection setup, as Yamux relies on an underlying
transport to be provided. However, there is a distinction between client
and server side of the connection.
## Opening a stream
To open a stream, an initial data or window update frame is sent
with a new StreamID. The SYN flag should be set to signal a new stream.
The receiver must then reply with either a data or window update frame
with the StreamID along with the ACK flag to accept the stream or with
the RST flag to reject the stream.
Because we are relying on the reliable stream underneath, a connection
can begin sending data once the SYN flag is sent. The corresponding
ACK does not need to be received. This is particularly well suited
for an RPC system where a client wants to open a stream and immediately
fire a request without waiting for the RTT of the ACK.
This does introduce the possibility of a connection being rejected
after data has been sent already. This is a slight semantic difference
from TCP, where the conection cannot be refused after it is opened.
Clients should be prepared to handle this by checking for an error
that indicates a RST was received.
## Closing a stream
To close a stream, either side sends a data or window update frame
along with the FIN flag. This does a half-close indicating the sender
will send no further data.
Once both sides have closed the connection, the stream is closed.
Alternatively, if an error occurs, the RST flag can be used to
hard close a stream immediately.
## Flow Control
When Yamux is initially starts each stream with a 256KB window size.
There is no window size for the session.
To prevent the streams from stalling, window update frames should be
sent regularly. Yamux can be configured to provide a larger limit for
windows sizes. Both sides assume the initial 256KB window, but can
immediately send a window update as part of the SYN/ACK indicating a
larger window.
Both sides should track the number of bytes sent in Data frames
only, as only they are tracked as part of the window size.
## Session termination
When a session is being terminated, the Go Away message should
be sent. The Length should be set to one of the following to
provide an error code:
* 0x0 Normal termination
* 0x1 Protocol error
* 0x2 Internal error
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package yamux
import (
"sync"
"time"
)
var (
timerPool = &sync.Pool{
New: func() interface{} {
timer := time.NewTimer(time.Hour * 1e6)
timer.Stop()
return timer
},
}
)
// asyncSendErr is used to try an async send of an error
func asyncSendErr(ch chan error, err error) {
if ch == nil {
return
}
select {
case ch <- err:
default:
}
</