shellconsts

Documentation

Overview

Package shellconsts contains constants shared between shell server and client which is split into different packages to reduce the binary size of potential commandline clients.

Index

• Constants

Constants

const (
	MessageTypeData  = 0
	MessageTypeAck   = 1
	MessageTypeSize  = 3
	MessageTypeAbort = 4
	MessageTypeExit  = 5
	StreamStdin      = 0
	StreamStdout     = 1
	StreamStderr     = 2
)

Message type codes for websocket messages implementing interactive shell.

We will send stdin, stdout, stderr, exit and abort messages over a websocket. Messages will all have the form: [type] [data]

Where [type] is a single byte with the value of MessageTypeData MessageTypeAbort or MessageTypeExit. The data property depends on the [type] of the message, as outlined below.

If [type] is MessageTypeData then

[data] = [stream] [payload]

, where [stream] is a single byte: StreamStdin, StreamStdout, StreamStderr, and [payload] is data from this stream. If [payload] is an empty byte sequence this signals the end of the stream.

If [type] is MessageTypeAck then

[data] = [stream] [N]

, where [stream] is a single byte: StreamStdin, StreamStdout, StreamStderr, and [N] is a big-endian 32 bit unsigned integer acknowleging the remote stream to have processed N bytes.

If [type] is MessageTypeAbort then [data] is empty, this message is used to request that the executing be aborted.

If [type] is MessageTypeExit then [data] = [exitCode], where exitCode is a single byte 0 (success) or 1 (failed) indicating whether the command terminated successfully.

If [type] is MessageTypeSize then

[data] = [colmns] [rows]

, where [colmns] and [rows] are big-endian 16 bit unsigned integers specifying the width and height of the TTY. If not supported this message is is ignored.

const (
	// ShellHandshakeTimeout is the maximum allowed time for websocket handshake
	ShellHandshakeTimeout = 30 * time.Second
	// ShellPingInterval is the time between sending pings
	ShellPingInterval = 15 * time.Second
	// ShellWriteTimeout is the maximum time between successful writes
	ShellWriteTimeout = ShellPingInterval * 2
	// ShellPongTimeout is the maximum time between successful reads
	ShellPongTimeout = ShellPingInterval * 3
	// ShellBlockSize is the maximum number of bytes to send in a single block
	ShellBlockSize = 16 * 1024
	// ShellMaxMessageSize is the maximum message size we will read
	ShellMaxMessageSize = ShellBlockSize + 4*1024
	// ShellMaxPendingBytes is the maximum number of bytes allowed in-flight
	ShellMaxPendingBytes = 4 * ShellBlockSize
)