Class: HTTP2::Connection

Inherits:
Object
  • Object
show all
Includes:
Emitter, Error, FlowBuffer
Defined in:
lib/http/2/connection.rb

Overview

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

Direct Known Subclasses

Client, Server

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Emitter

#add_listener, #emit, #once

Methods included from FlowBuffer

#buffered_amount

Constructor Details

#initialize(**settings) ⇒ Connection

Initializes new connection object.


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# 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 = {}
  @streams_recently_closed = {}
  @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

Instance Attribute Details

#active_stream_countObject (readonly)

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


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# File 'lib/http/2/connection.rb', line 71

def active_stream_count
  @active_stream_count
end

#local_settingsObject (readonly)

Current settings value for local and peer


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# File 'lib/http/2/connection.rb', line 62

def local_settings
  @local_settings
end

#local_windowObject (readonly) Also known as: window

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


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# File 'lib/http/2/connection.rb', line 57

def local_window
  @local_window
end

#pending_settingsObject (readonly)

Pending settings value

Sent but not ack'ed settings

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# File 'lib/http/2/connection.rb', line 67

def pending_settings
  @pending_settings
end

#remote_settingsObject (readonly)

Returns the value of attribute remote_settings


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# File 'lib/http/2/connection.rb', line 63

def remote_settings
  @remote_settings
end

#remote_windowObject (readonly)

Returns the value of attribute remote_window


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# File 'lib/http/2/connection.rb', line 58

def remote_window
  @remote_window
end

#stateObject (readonly)

Connection state (:new, :closed).


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# File 'lib/http/2/connection.rb', line 50

def state
  @state
end

Instance Method Details

#goaway(error = :no_error, payload = nil) ⇒ Object

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.


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# File 'lib/http/2/connection.rb', line 134

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) ⇒ Object

Allocates new stream for current connection.


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# File 'lib/http/2/connection.rb', line 105

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) ⇒ Object

Sends PING frame to the peer.


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# File 'lib/http/2/connection.rb', line 119

def ping(payload, &blk)
  send(type: :ping, stream: 0, payload: payload)
  once(:ack, &blk) if blk
end

#receive(data) ⇒ Object Also known as: <<

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.


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# File 'lib/http/2/connection.rb', line 171

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
        # When server receives even-numbered stream identifier,
        # the endpoint MUST respond with a connection error of type PROTOCOL_ERROR.
        connection_error if frame[:stream].even? && self.is_a?(Server)

        # 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]

        # if PUSH parent is recently closed, RST_STREAM the push
        if @streams_recently_closed[frame[:stream]]
          send(type: :rst_stream, stream: pid, error: :refused_stream)
          return
        end

        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
          if frame[:type] == :data
            update_local_window(frame)
            calculate_window_update(@local_window_limit)
          end
        else
          case frame[:type]
          # 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.
          when :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

          # WINDOW_UPDATE can be sent by a peer that has sent a frame
          # bearing the END_STREAM flag. This means that a receiver could
          # receive a WINDOW_UPDATE frame on a "half-closed (remote)" or
          # "closed" stream. A receiver MUST NOT treat this as an error
          # (see Section 5.1).
          when :window_update
            process_window_update(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

#settings(payload) ⇒ Object

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


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# File 'lib/http/2/connection.rb', line 158

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

#window_update(increment) ⇒ Object

Sends a WINDOW_UPDATE frame to the peer.


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# File 'lib/http/2/connection.rb', line 149

def window_update(increment)
  @local_window += increment
  send(type: :window_update, stream: 0, increment: increment)
end