tech: adds/removes in vendor folder according to dep 0.4.0.
This commit is contained in:
Leonard Gram
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# Compiled Object files, Static and Dynamic libs (Shared Objects)
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*.o
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*.a
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*.so
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# Folders
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_obj
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_test
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# Architecture specific extensions/prefixes
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*.[568vq]
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[568vq].out
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*.cgo1.go
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*.cgo2.c
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_cgo_defun.c
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_cgo_gotypes.go
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_cgo_export.*
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_testmain.go
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*.exe
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*.test
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-86
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# Yamux
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Yamux (Yet another Multiplexer) is a multiplexing library for Golang.
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It relies on an underlying connection to provide reliability
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and ordering, such as TCP or Unix domain sockets, and provides
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stream-oriented multiplexing. It is inspired by SPDY but is not
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interoperable with it.
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Yamux features include:
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* Bi-directional streams
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* Streams can be opened by either client or server
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* Useful for NAT traversal
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* Server-side push support
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* Flow control
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* Avoid starvation
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* Back-pressure to prevent overwhelming a receiver
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* Keep Alives
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* Enables persistent connections over a load balancer
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* Efficient
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* Enables thousands of logical streams with low overhead
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## Documentation
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For complete documentation, see the associated [Godoc](http://godoc.org/github.com/hashicorp/yamux).
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## Specification
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The full specification for Yamux is provided in the `spec.md` file.
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It can be used as a guide to implementors of interoperable libraries.
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## Usage
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Using Yamux is remarkably simple:
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```go
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func client() {
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// Get a TCP connection
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conn, err := net.Dial(...)
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if err != nil {
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panic(err)
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}
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// Setup client side of yamux
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session, err := yamux.Client(conn, nil)
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if err != nil {
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panic(err)
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}
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// Open a new stream
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stream, err := session.Open()
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if err != nil {
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panic(err)
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}
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// Stream implements net.Conn
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stream.Write([]byte("ping"))
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}
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func server() {
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// Accept a TCP connection
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conn, err := listener.Accept()
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if err != nil {
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panic(err)
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}
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// Setup server side of yamux
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session, err := yamux.Server(conn, nil)
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if err != nil {
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panic(err)
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}
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// Accept a stream
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stream, err := session.Accept()
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if err != nil {
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panic(err)
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}
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// Listen for a message
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buf := make([]byte, 4)
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stream.Read(buf)
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}
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```
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-140
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# Specification
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We use this document to detail the internal specification of Yamux.
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This is used both as a guide for implementing Yamux, but also for
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alternative interoperable libraries to be built.
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# Framing
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Yamux uses a streaming connection underneath, but imposes a message
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framing so that it can be shared between many logical streams. Each
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frame contains a header like:
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* Version (8 bits)
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* Type (8 bits)
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* Flags (16 bits)
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* StreamID (32 bits)
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* Length (32 bits)
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This means that each header has a 12 byte overhead.
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All fields are encoded in network order (big endian).
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Each field is described below:
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## Version Field
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The version field is used for future backward compatibility. At the
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current time, the field is always set to 0, to indicate the initial
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version.
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## Type Field
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The type field is used to switch the frame message type. The following
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message types are supported:
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* 0x0 Data - Used to transmit data. May transmit zero length payloads
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depending on the flags.
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* 0x1 Window Update - Used to updated the senders receive window size.
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This is used to implement per-session flow control.
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* 0x2 Ping - Used to measure RTT. It can also be used to heart-beat
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and do keep-alives over TCP.
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* 0x3 Go Away - Used to close a session.
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## Flag Field
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The flags field is used to provide additional information related
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to the message type. The following flags are supported:
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* 0x1 SYN - Signals the start of a new stream. May be sent with a data or
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window update message. Also sent with a ping to indicate outbound.
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* 0x2 ACK - Acknowledges the start of a new stream. May be sent with a data
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or window update message. Also sent with a ping to indicate response.
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* 0x4 FIN - Performs a half-close of a stream. May be sent with a data
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message or window update.
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* 0x8 RST - Reset a stream immediately. May be sent with a data or
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window update message.
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## StreamID Field
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The StreamID field is used to identify the logical stream the frame
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is addressing. The client side should use odd ID's, and the server even.
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This prevents any collisions. Additionally, the 0 ID is reserved to represent
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the session.
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Both Ping and Go Away messages should always use the 0 StreamID.
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## Length Field
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The meaning of the length field depends on the message type:
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* Data - provides the length of bytes following the header
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* Window update - provides a delta update to the window size
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* Ping - Contains an opaque value, echoed back
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* Go Away - Contains an error code
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# Message Flow
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There is no explicit connection setup, as Yamux relies on an underlying
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transport to be provided. However, there is a distinction between client
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and server side of the connection.
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## Opening a stream
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To open a stream, an initial data or window update frame is sent
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with a new StreamID. The SYN flag should be set to signal a new stream.
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The receiver must then reply with either a data or window update frame
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with the StreamID along with the ACK flag to accept the stream or with
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the RST flag to reject the stream.
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Because we are relying on the reliable stream underneath, a connection
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can begin sending data once the SYN flag is sent. The corresponding
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ACK does not need to be received. This is particularly well suited
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for an RPC system where a client wants to open a stream and immediately
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fire a request without waiting for the RTT of the ACK.
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This does introduce the possibility of a connection being rejected
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after data has been sent already. This is a slight semantic difference
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from TCP, where the conection cannot be refused after it is opened.
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Clients should be prepared to handle this by checking for an error
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that indicates a RST was received.
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## Closing a stream
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To close a stream, either side sends a data or window update frame
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along with the FIN flag. This does a half-close indicating the sender
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will send no further data.
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Once both sides have closed the connection, the stream is closed.
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Alternatively, if an error occurs, the RST flag can be used to
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hard close a stream immediately.
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## Flow Control
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When Yamux is initially starts each stream with a 256KB window size.
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There is no window size for the session.
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To prevent the streams from stalling, window update frames should be
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sent regularly. Yamux can be configured to provide a larger limit for
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windows sizes. Both sides assume the initial 256KB window, but can
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immediately send a window update as part of the SYN/ACK indicating a
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larger window.
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Both sides should track the number of bytes sent in Data frames
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only, as only they are tracked as part of the window size.
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## Session termination
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When a session is being terminated, the Go Away message should
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be sent. The Length should be set to one of the following to
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provide an error code:
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* 0x0 Normal termination
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* 0x1 Protocol error
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* 0x2 Internal error
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