class HTTP2::Connection

Connection encapsulates all of the connection, stream, flow-control, error management, and other processing logic required for a well-behaved HTTP 2.0 endpoint.

Note that this class should not be used directly. Instead, you want to use either Client or Server class to drive the HTTP 2.0 exchange.

rubocop:disable ClassLength

Attributes

active_stream_count[R]

Number of active streams between client and server (reserved streams are not counted towards the stream limit).

error[R]

Last connection error if connection is aborted.

local_settings[R]

Current settings value for local and peer

local_window[R]

Size of current connection flow control window (by default, set to infinity, but is automatically updated on receipt of peer settings).

pending_settings[R]

Pending settings value

Sent but not ack'ed settings
remote_settings[R]
remote_window[R]
state[R]

Connection state (:new, :closed).

window[R]

Size of current connection flow control window (by default, set to infinity, but is automatically updated on receipt of peer settings).

Public Class Methods

new(**settings) click to toggle source

Initializes new connection object.

# File lib/http/2/connection.rb, line 75
def initialize(**settings)
  @local_settings  = DEFAULT_CONNECTION_SETTINGS.merge(settings)
  @remote_settings = SPEC_DEFAULT_CONNECTION_SETTINGS.dup

  @compressor   = Header::Compressor.new(settings)
  @decompressor = Header::Decompressor.new(settings)

  @active_stream_count = 0
  @streams = {}
  @pending_settings = []

  @framer = Framer.new

  @local_window_limit = @local_settings[:settings_initial_window_size]
  @local_window = @local_window_limit
  @remote_window_limit = @remote_settings[:settings_initial_window_size]
  @remote_window = @remote_window_limit

  @recv_buffer = Buffer.new
  @send_buffer = []
  @continuation = []
  @error = nil
end

Public Instance Methods

<<(data)
Alias for: receive
goaway(error = :no_error, payload = nil) click to toggle source

Sends a GOAWAY frame indicating that the peer should stop creating new streams for current connection.

Endpoints MAY append opaque data to the payload of any GOAWAY frame. Additional debug data is intended for diagnostic purposes only and carries no semantic value. Debug data MUST NOT be persistently stored, since it could contain sensitive information.

@param error [Symbol] @param payload [String]

# File lib/http/2/connection.rb, line 133
def goaway(error = :no_error, payload = nil)
  last_stream = if (max = @streams.max)
    max.first
  else
    0
  end

  send(type: :goaway, last_stream: last_stream,
       error: error, payload: payload)
  @state = :closed
end
new_stream(**args) click to toggle source

Allocates new stream for current connection.

@param priority [Integer] @param window [Integer] @param parent [Stream]

# File lib/http/2/connection.rb, line 104
def new_stream(**args)
  fail ConnectionClosed if @state == :closed
  fail StreamLimitExceeded if @active_stream_count >= @remote_settings[:settings_max_concurrent_streams]

  stream = activate_stream(id: @stream_id, **args)
  @stream_id += 2

  stream
end
ping(payload, &blk) click to toggle source

Sends PING frame to the peer.

@param payload [String] optional payload must be 8 bytes long @param blk [Proc] callback to execute when PONG is received

# File lib/http/2/connection.rb, line 118
def ping(payload, &blk)
  send(type: :ping, stream: 0, payload: payload)
  once(:ack, &blk) if blk
end
receive(data) click to toggle source

Decodes incoming bytes into HTTP 2.0 frames and routes them to appropriate receivers: connection frames are handled directly, and stream frames are passed to appropriate stream objects.

@param data [String] Binary encoded string

# File lib/http/2/connection.rb, line 162
def receive(data)
  @recv_buffer << data

  # Upon establishment of a TCP connection and determination that
  # HTTP/2.0 will be used by both peers, each endpoint MUST send a
  # connection header as a final confirmation and to establish the
  # initial settings for the HTTP/2.0 connection.
  #
  # Client connection header is 24 byte connection header followed by
  # SETTINGS frame. Server connection header is SETTINGS frame only.
  if @state == :waiting_magic
    if @recv_buffer.size < 24
      if !CONNECTION_PREFACE_MAGIC.start_with? @recv_buffer
        fail HandshakeError
      else
        return # maybe next time
      end
    elsif @recv_buffer.read(24) == CONNECTION_PREFACE_MAGIC
      # MAGIC is OK.  Send our settings
      @state = :waiting_connection_preface
      payload = @local_settings.reject { |k, v| v == SPEC_DEFAULT_CONNECTION_SETTINGS[k] }
      settings(payload)
    else
      fail HandshakeError
    end
  end

  while (frame = @framer.parse(@recv_buffer))
    emit(:frame_received, frame)

    # Header blocks MUST be transmitted as a contiguous sequence of frames
    # with no interleaved frames of any other type, or from any other stream.
    unless @continuation.empty?
      unless frame[:type] == :continuation && frame[:stream] == @continuation.first[:stream]
        connection_error
      end

      @continuation << frame
      return unless frame[:flags].include? :end_headers

      payload = @continuation.map { |f| f[:payload] }.join

      frame = @continuation.shift
      @continuation.clear

      frame.delete(:length)
      frame[:payload] = Buffer.new(payload)
      frame[:flags] << :end_headers
    end

    # SETTINGS frames always apply to a connection, never a single stream.
    # The stream identifier for a settings frame MUST be zero.  If an
    # endpoint receives a SETTINGS frame whose stream identifier field is
    # anything other than 0x0, the endpoint MUST respond with a connection
    # error (Section 5.4.1) of type PROTOCOL_ERROR.
    if connection_frame?(frame)
      connection_management(frame)
    else
      case frame[:type]
      when :headers
        # The last frame in a sequence of HEADERS/CONTINUATION
        # frames MUST have the END_HEADERS flag set.
        unless frame[:flags].include? :end_headers
          @continuation << frame
          return
        end

        # After sending a GOAWAY frame, the sender can discard frames
        # for new streams.  However, any frames that alter connection
        # state cannot be completely ignored.  For instance, HEADERS,
        # PUSH_PROMISE and CONTINUATION frames MUST be minimally
        # processed to ensure a consistent compression state
        decode_headers(frame)
        return if @state == :closed

        stream = @streams[frame[:stream]]
        if stream.nil?
          stream = activate_stream(
            id:         frame[:stream],
            weight:     frame[:weight] || DEFAULT_WEIGHT,
            dependency: frame[:dependency] || 0,
            exclusive:  frame[:exclusive] || false,
          )
          emit(:stream, stream)
        end

        stream << frame

      when :push_promise
        # The last frame in a sequence of PUSH_PROMISE/CONTINUATION
        # frames MUST have the END_HEADERS flag set
        unless frame[:flags].include? :end_headers
          @continuation << frame
          return
        end

        decode_headers(frame)
        return if @state == :closed

        # PUSH_PROMISE frames MUST be associated with an existing, peer-
        # initiated stream... A receiver MUST treat the receipt of a
        # PUSH_PROMISE on a stream that is neither "open" nor
        # "half-closed (local)" as a connection error (Section 5.4.1) of
        # type PROTOCOL_ERROR. Similarly, a receiver MUST treat the
        # receipt of a PUSH_PROMISE that promises an illegal stream
        # identifier (Section 5.1.1) (that is, an identifier for a stream
        # that is not currently in the "idle" state) as a connection error
        # (Section 5.4.1) of type PROTOCOL_ERROR, unless the receiver
        # recently sent a RST_STREAM frame to cancel the associated stream.
        parent = @streams[frame[:stream]]
        pid = frame[:promise_stream]

        connection_error(msg: 'missing parent ID') if parent.nil?

        unless parent.state == :open || parent.state == :half_closed_local
          # An endpoint might receive a PUSH_PROMISE frame after it sends
          # RST_STREAM.  PUSH_PROMISE causes a stream to become "reserved".
          # The RST_STREAM does not cancel any promised stream.  Therefore, if
          # promised streams are not desired, a RST_STREAM can be used to
          # close any of those streams.
          if parent.closed == :local_rst
            # We can either (a) 'resurrect' the parent, or (b) RST_STREAM
            # ... sticking with (b), might need to revisit later.
            send(type: :rst_stream, stream: pid, error: :refused_stream)
          else
            connection_error
          end
        end

        stream = activate_stream(id: pid, parent: parent)
        emit(:promise, stream)
        stream << frame
      else
        if (stream = @streams[frame[:stream]])
          stream << frame
        else
          # The PRIORITY frame can be sent for a stream in the "idle" or
          # "closed" state. This allows for the reprioritization of a
          # group of dependent streams by altering the priority of an
          # unused or closed parent stream.
          if frame[:type] == :priority
            stream = activate_stream(
              id:         frame[:stream],
              weight:     frame[:weight] || DEFAULT_WEIGHT,
              dependency: frame[:dependency] || 0,
              exclusive:  frame[:exclusive] || false,
            )

            emit(:stream, stream)
            stream << frame
          else
            # An endpoint that receives an unexpected stream identifier
            # MUST respond with a connection error of type PROTOCOL_ERROR.
            connection_error
          end
        end
      end
    end
  end

rescue => e
  raise if e.is_a?(Error::Error)
  connection_error(e: e)
end
Also aliased as: <<
settings(payload) click to toggle source

Sends a connection SETTINGS frame to the peer. The values are reflected when the corresponding ACK is received.

@param settings [Array or Hash]

# File lib/http/2/connection.rb, line 149
def settings(payload)
  payload = payload.to_a
  connection_error if validate_settings(@local_role, payload)
  @pending_settings << payload
  send(type: :settings, stream: 0, payload: payload)
  @pending_settings << payload
end

Private Instance Methods

activate_stream(id: nil, **args) click to toggle source

Activates new incoming or outgoing stream and registers appropriate connection managemet callbacks.

@param id [Integer] @param priority [Integer] @param window [Integer] @param parent [Stream]

# File lib/http/2/connection.rb, line 619
def activate_stream(id: nil, **args)
  connection_error(msg: 'Stream ID already exists') if @streams.key?(id)

  stream = Stream.new(self, id, {}.merge(args))

  # Streams that are in the "open" state, or either of the "half closed"
  # states count toward the maximum number of streams that an endpoint is
  # permitted to open.
  stream.once(:active) { @active_stream_count += 1 }
  stream.once(:close)  { @active_stream_count -= 1 }
  stream.on(:promise, &method(:promise)) if self.is_a? Server
  stream.on(:frame,   &method(:send))

  @streams[id] = stream
end
connection_error(error = :protocol_error, msg: nil, e: nil) click to toggle source

Emit GOAWAY error indicating to peer that the connection is being aborted, and once sent, raise a local exception.

@param error [Symbol] @option error [Symbol] :no_error @option error [Symbol] :internal_error @option error [Symbol] :flow_control_error @option error [Symbol] :stream_closed @option error [Symbol] :frame_too_large @option error [Symbol] :compression_error @param msg [String]

# File lib/http/2/connection.rb, line 646
def connection_error(error = :protocol_error, msg: nil, e: nil)
  goaway(error) unless @state == :closed || @state == :new

  @state, @error = :closed, error
  klass = error.to_s.split('_').map(&:capitalize).join
  fail Error.const_get(klass), msg || e.message, e.backtrace || []
end
connection_frame?(frame) click to toggle source

Check if frame is a connection frame: SETTINGS, PING, GOAWAY, and any frame addressed to stream ID = 0.

@param frame [Hash] @return [Boolean]

# File lib/http/2/connection.rb, line 376
def connection_frame?(frame)
  frame[:stream] == 0 ||
    frame[:type] == :settings ||
    frame[:type] == :ping ||
    frame[:type] == :goaway
end
connection_management(frame) click to toggle source

Process received connection frame (stream ID = 0).

  • Handle SETTINGS updates

  • Connection flow control (WINDOW_UPDATE)

  • Emit PONG auto-reply to PING frames

  • Mark connection as closed on GOAWAY

@param frame [Hash]

# File lib/http/2/connection.rb, line 390
def connection_management(frame)
  case @state
  when :waiting_connection_preface
    # The first frame MUST be a SETTINGS frame at the start of a connection.
    @state = :connected
    connection_settings(frame)

  when :connected
    case frame[:type]
    when :settings
      connection_settings(frame)
    when :window_update
      @remote_window += frame[:increment]
      send_data(nil, true)
    when :ping
      if frame[:flags].include? :ack
        emit(:ack, frame[:payload])
      else
        send(type: :ping, stream: 0,
             flags: [:ack], payload: frame[:payload])
      end
    when :goaway
      # Receivers of a GOAWAY frame MUST NOT open additional streams on
      # the connection, although a new connection can be established
      # for new streams.
      @state = :closed
      emit(:goaway, frame[:last_stream], frame[:error], frame[:payload])
    when :altsvc, :blocked
      emit(frame[:type], frame)
    else
      connection_error
    end
  else
    connection_error
  end
end
connection_settings(frame) click to toggle source

Update connection settings based on parameters set by the peer.

@param frame [Hash]

# File lib/http/2/connection.rb, line 480
def connection_settings(frame)
  connection_error unless frame[:type] == :settings && frame[:stream] == 0

  # Apply settings.
  #  side =
  #   local: previously sent and pended our settings should be effective
  #   remote: just received peer settings should immediately be effective
  settings, side = if frame[:flags].include?(:ack)
    # Process pending settings we have sent.
    [@pending_settings.shift, :local]
  else
    connection_error(check) if validate_settings(@remote_role, frame[:payload])
    [frame[:payload], :remote]
  end

  settings.each do |key, v|
    case side
    when :local
      @local_settings[key] = v
    when :remote
      @remote_settings[key] = v
    end

    case key
    when :settings_max_concurrent_streams
      # Do nothing.
      # The value controls at the next attempt of stream creation.

    when :settings_initial_window_size
      # A change to SETTINGS_INITIAL_WINDOW_SIZE could cause the available
      # space in a flow control window to become negative. A sender MUST
      # track the negative flow control window, and MUST NOT send new flow
      # controlled frames until it receives WINDOW_UPDATE frames that cause
      # the flow control window to become positive.
      case side
      when :local
        @local_window = @local_window - @local_window_limit + v
        @streams.each do |_id, stream|
          stream.emit(:local_window, stream.local_window - @local_window_limit + v)
        end

        @local_window_limit = v
      when :remote
        @remote_window = @remote_window - @remote_window_limit + v
        @streams.each do |_id, stream|
          # Event name is :window, not :remote_window
          stream.emit(:window, stream.remote_window - @remote_window_limit + v)
        end

        @remote_window_limit = v
      end

    when :settings_header_table_size
      # Setting header table size might cause some headers evicted
      case side
      when :local
        @decompressor.table_size = v
      when :remote
        @compressor.table_size = v
      end

    when :settings_enable_push
      # nothing to do

    when :settings_max_frame_size
      # nothing to do

      # else # ignore unknown settings
    end
  end

  case side
  when :local
    # Received a settings_ack.  Notify application layer.
    emit(:settings_ack, frame, @pending_settings.size)
  when :remote
    unless @state == :closed || @h2c_upgrade == :start
      # Send ack to peer
      send(type: :settings, stream: 0, payload: [], flags: [:ack])
    end
  end
end
decode_headers(frame) click to toggle source

Decode headers payload and update connection decompressor state.

The receiver endpoint reassembles the header block by concatenating the individual fragments, then decompresses the block to reconstruct the header set - aka, header payloads are buffered until END_HEADERS, or an END_PROMISE flag is seen.

@param frame [Hash]

# File lib/http/2/connection.rb, line 571
def decode_headers(frame)
  if frame[:payload].is_a? String
    frame[:payload] = @decompressor.decode(frame[:payload])
  end

rescue => e
  connection_error(:compression_error, e: e)
end
encode(frame) click to toggle source

Applies HTTP 2.0 binary encoding to the frame.

@param frame [Hash] @return [Array of Buffer] encoded frame

# File lib/http/2/connection.rb, line 359
def encode(frame)
  frames = []

  if frame[:type] == :headers || frame[:type] == :push_promise
    frames = encode_headers(frame) # HEADERS and PUSH_PROMISE may create more than one frame
  else
    frames = [frame]               # otherwise one frame
  end

  frames.map { |f| @framer.generate(f) }
end
encode_headers(frame) click to toggle source

Encode headers payload and update connection compressor state.

@param frame [Hash] @return [Array of Frame]

# File lib/http/2/connection.rb, line 584
def encode_headers(frame)
  payload = frame[:payload]
  payload = @compressor.encode(payload) unless payload.is_a? String

  frames = []

  while payload.size > 0
    cont = frame.dup
    cont[:type] = :continuation
    cont[:flags] = []
    cont[:payload] = payload.slice!(0, @remote_settings[:settings_max_frame_size])
    frames << cont
  end
  if frames.empty?
    frames = [frame]
  else
    frames.first[:type]  = frame[:type]
    frames.first[:flags] = frame[:flags] - [:end_headers]
    frames.last[:flags] << :end_headers
  end

  frames

rescue => e
  connection_error(:compression_error, e: e)
  nil
end
send(frame) click to toggle source

Send an outgoing frame. DATA frames are subject to connection flow control and may be split and / or buffered based on current window size. All other frames are sent immediately.

@note all frames are currently delivered in FIFO order. @param frame [Hash]

# File lib/http/2/connection.rb, line 336
def send(frame)
  emit(:frame_sent, frame)
  if frame[:type] == :data
    send_data(frame, true)

  else
    # An endpoint can end a connection at any time. In particular, an
    # endpoint MAY choose to treat a stream error as a connection error.
    if frame[:type] == :rst_stream && frame[:error] == :protocol_error
      goaway(frame[:error])
    else
      # HEADERS and PUSH_PROMISE may generate CONTINUATION. Also send
      # RST_STREAM that are not protocol errors
      frames = encode(frame)
      frames.each { |f| emit(:frame, f) }
    end
  end
end
validate_settings(role, settings) click to toggle source

Validate settings parameters. See sepc Section 6.5.2.

@param role [Symbol] The sender's role: :client or :server @return nil if no error. Exception object in case of any error.

# File lib/http/2/connection.rb, line 431
def validate_settings(role, settings)
  settings.each do |key, v|
    case key
    when :settings_header_table_size
      # Any value is valid
    when :settings_enable_push
      case role
      when :server
        # Section 8.2
        # Clients MUST reject any attempt to change the
        # SETTINGS_ENABLE_PUSH setting to a value other than 0 by treating the
        # message as a connection error (Section 5.4.1) of type PROTOCOL_ERROR.
        return ProtocolError.new("invalid #{key} value") unless v == 0
      when :client
        # Any value other than 0 or 1 MUST be treated as a
        # connection error (Section 5.4.1) of type PROTOCOL_ERROR.
        unless v == 0 || v == 1
          return ProtocolError.new("invalid #{key} value")
        end
      end
    when :settings_max_concurrent_streams
      # Any value is valid
    when :settings_initial_window_size
      # Values above the maximum flow control window size of 2^31-1 MUST
      # be treated as a connection error (Section 5.4.1) of type
      # FLOW_CONTROL_ERROR.
      unless v <= 0x7fffffff
        return FlowControlError.new("invalid #{key} value")
      end
    when :settings_max_frame_size
      # The initial value is 2^14 (16,384) octets.  The value advertised
      # by an endpoint MUST be between this initial value and the maximum
      # allowed frame size (2^24-1 or 16,777,215 octets), inclusive.
      # Values outside this range MUST be treated as a connection error
      # (Section 5.4.1) of type PROTOCOL_ERROR.
      unless 16_384 <= v && v <= 16_777_215
        return ProtocolError.new("invalid #{key} value")
      end
    when :settings_max_header_list_size
      # Any value is valid
      # else # ignore unknown settings
    end
  end
  nil
end