WebSocketChannel implementation

net/websockets/websocket_channel.cc

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/websockets/websocket_channel.h"
+
+#include <algorithm>
+
+#include "base/basictypes.h"  // for size_t
+#include "base/bind.h"
+#include "base/safe_numerics.h"
+#include "base/strings/string_util.h"
+#include "net/base/big_endian.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_log.h"
+#include "net/websockets/websocket_errors.h"
+#include "net/websockets/websocket_event_interface.h"
+#include "net/websockets/websocket_frame.h"
+#include "net/websockets/websocket_mux.h"
+#include "net/websockets/websocket_stream.h"
+
+namespace net {
+
+namespace {
+
+const int kDefaultSendQuotaLowWaterMark = 1 << 16;
+const int kDefaultSendQuotaHighWaterMark = 1 << 17;
+const size_t kWebSocketCloseCodeLength = 2;
+
+// Concatenate the data from two IOBufferWithSize objects into a single one.
+IOBufferWithSize* ConcatenateIOBuffers(
+    const scoped_refptr<IOBufferWithSize>& part1,
+    const scoped_refptr<IOBufferWithSize>& part2) {
+  int newsize = part1->size() + part2->size();
+  IOBufferWithSize* newbuffer = new IOBufferWithSize(newsize);
+  std::copy(part1->data(), part1->data() + part1->size(), newbuffer->data());
+  std::copy(part2->data(),
+            part2->data() + part2->size(),
+            newbuffer->data() + part1->size());
+  return newbuffer;
+}
+
+}  // namespace
+
+struct WebSocketChannel::SendBuffer {
+  SendBuffer() : total_bytes(0) {}
+  ScopedVector<WebSocketFrameChunk> frames;
+  size_t total_bytes;
+};
+
+// Implementation of WebSocketStream::ConnectDelegate that simply forwards the
+// calls on to the WebSocketChannel that created it.
+class WebSocketChannel::ConnectDelegate
+    : public WebSocketStream::ConnectDelegate {
+ public:
+  explicit ConnectDelegate(WebSocketChannel* creator) : creator_(creator) {}
+
+  virtual void OnSuccess(scoped_ptr<WebSocketStream> stream) OVERRIDE {
+    creator_->OnConnectSuccess(stream.Pass());
+  }
+
+  virtual void OnFailure(uint16 websocket_error) OVERRIDE {
+    creator_->OnConnectFailure(websocket_error);
+  }
+
+ private:
+  // A pointer to the WebSocketChannel that created us. We do not need to worry
+  // about this pointer being stale, because deleting WebSocketChannel cancels
+  // the connect process, deleting this object and preventing its callbacks from
+  // being called.
+  WebSocketChannel* const creator_;
+
+  DISALLOW_COPY_AND_ASSIGN(ConnectDelegate);
+};
+
+WebSocketChannel::WebSocketChannel(
+    const GURL& socket_url,
+    scoped_ptr<WebSocketEventInterface> event_interface)
+    : socket_url_(socket_url),
+      event_interface_(event_interface.Pass()),
+      send_quota_low_water_mark_(kDefaultSendQuotaLowWaterMark),
+      send_quota_high_water_mark_(kDefaultSendQuotaHighWaterMark),
+      current_send_quota_(0),
+      closing_code_(0),
+      state_(FRESHLY_CONSTRUCTED) {}
+
+WebSocketChannel::~WebSocketChannel() {
+  // The stream may hold a pointer to read_frame_chunks_, and so it needs to be
+  // destroyed first.
+  stream_.reset();
+}
+
+void WebSocketChannel::SendAddChannelRequest(
+    const std::vector<std::string>& requested_subprotocols,
+    const GURL& origin,
+    URLRequestContext* url_request_context) {
+  // Delegate to the tested version.
+  SendAddChannelRequestWithFactory(
+      requested_subprotocols,
+      origin,
+      url_request_context,
+      base::Bind(&WebSocketStream::CreateAndConnectStream));
+}
+
+void WebSocketChannel::SendAddChannelRequestWithFactory(
+    const std::vector<std::string>& requested_subprotocols,
+    const GURL& origin,
+    URLRequestContext* url_request_context,
+    base::Callback<scoped_ptr<WebSocketStreamRequest>(
+        const GURL&,
+        const std::vector<std::string>&,
+        const GURL&,
+        URLRequestContext*,
+        const BoundNetLog&,
+        scoped_ptr<WebSocketStream::ConnectDelegate>)> factory) {
+  DCHECK_EQ(FRESHLY_CONSTRUCTED, state_);
+  scoped_ptr<WebSocketStream::ConnectDelegate> connect_delegate(
+      new WebSocketChannel::ConnectDelegate(this));
+  stream_request_ = factory.Run(socket_url_,
+                                requested_subprotocols,
+                                origin,
+                                url_request_context,
+                                BoundNetLog(),
+                                connect_delegate.Pass());
+  state_ = CONNECTING;
+}
+
+void WebSocketChannel::OnConnectSuccess(scoped_ptr<WebSocketStream> stream) {
+  DCHECK(stream);
+  DCHECK_EQ(CONNECTING, state_);
+  stream_ = stream.Pass();
+  state_ = CONNECTED;
+  event_interface_->OnAddChannelResponse(false, stream_->GetSubProtocol());
+
+  // TODO(ricea): Get flow control information from the WebSocketStream once we
+  // have a multiplexing WebSocketStream.
+  current_send_quota_ = send_quota_high_water_mark_;
+  event_interface_->OnFlowControl(send_quota_high_water_mark_);
+
+  // We don't need this any more.
+  stream_request_.reset();
+  ReadFrames();
+}
+
+void WebSocketChannel::OnConnectFailure(uint16 websocket_error) {
+  DCHECK_EQ(CONNECTING, state_);
+  state_ = CLOSED;
+  stream_request_.reset();
+  event_interface_->OnAddChannelResponse(true, "");
+}
+
+void WebSocketChannel::SendFrame(bool fin,
+                                 WebSocketFrameHeader::OpCode op_code,
+                                 const std::vector<char>& data) {
+  if (data.size() > INT_MAX) {
+    NOTREACHED() << "Frame size sanity check failed";
+    return;
+  }
+  if (stream_ == NULL) {
+    LOG(DFATAL) << "Got SendFrame without a connection established; "
+                << "misbehaving renderer? fin=" << fin << " op_code=" << op_code
+                << " data.size()=" << data.size();
+    return;
+  }
+  if (state_ == SEND_CLOSED || state_ == CLOSED) {
+    VLOG(1) << "SendFrame called in state " << state_
+            << ". This may be a bug, or a harmless race.";
+    return;
+  }
+  if (state_ != CONNECTED) {
+    NOTREACHED() << "SendFrame() called in state " << state_;
+    return;
+  }
+  if (data.size() > base::checked_numeric_cast<size_t>(current_send_quota_)) {
+    FailChannel(SEND_GOING_AWAY,
+                kWebSocketMuxErrorSendQuotaViolation,
+                "Send quota exceeded");
+    return;
+  }
+  if (!WebSocketFrameHeader::IsKnownDataOpCode(op_code)) {
+    LOG(DFATAL) << "Got SendFrame with bogus op_code " << op_code
+                << "; misbehaving renderer? fin=" << fin
+                << " data.size()=" << data.size();
+    return;
+  }
+  current_send_quota_ -= data.size();
+  // TODO(ricea): If current_send_quota_ has dropped below
+  // send_quota_low_water_mark_, we may want to consider increasing the "low
+  // water mark" and "high water mark", but only if we think we are not
+  // saturating the link to the WebSocket server.
+  // TODO(ricea): For kOpCodeText, do UTF-8 validation?
+  scoped_refptr<IOBufferWithSize> buffer(new IOBufferWithSize(data.size()));
+  std::copy(data.begin(), data.end(), buffer->data());
+  SendIOBufferWithSize(fin, op_code, buffer);
+}
+
+void WebSocketChannel::SendIOBufferWithSize(
+    bool fin,
+    WebSocketFrameHeader::OpCode op_code,
+    const scoped_refptr<IOBufferWithSize>& buffer) {
+  DCHECK(state_ == CONNECTED || state_ == RECV_CLOSED);
+  DCHECK(stream_);
+  scoped_ptr<WebSocketFrameHeader> header(new WebSocketFrameHeader(op_code));
+  header->final = fin;
+  header->masked = true;
+  header->payload_length = buffer->size();
+  scoped_ptr<WebSocketFrameChunk> chunk(new WebSocketFrameChunk());
+  chunk->header = header.Pass();
+  chunk->final_chunk = true;
+  chunk->data = buffer;
+  if (data_being_sent_) {
+    // Either the link to the WebSocket server is saturated, or we are simply
+    // processing a batch of messages.
+    // TODO(ricea): We need to keep some statistics to work out which situation
+    // we are in and adjust quota appropriately.
+    if (!data_to_send_next_) {
+      data_to_send_next_.reset(new SendBuffer);
+    }
+    data_to_send_next_->frames.push_back(chunk.release());
+    data_to_send_next_->total_bytes += buffer->size();
+  } else {
+    data_being_sent_.reset(new SendBuffer);
+    data_being_sent_->frames.push_back(chunk.release());
+    data_being_sent_->total_bytes += buffer->size();
+    WriteFrames();
+  }
+}
+
+void WebSocketChannel::WriteFrames() {
+  int result = OK;
+  do {
+    // This use of base::Unretained is safe because we own the WebSocketStream
+    // and destroying it cancels all callbacks.
+    result = stream_->WriteFrames(
+        &(data_being_sent_->frames),
+        base::Bind(
+            &WebSocketChannel::OnWriteDone, base::Unretained(this), false));
+    if (result != ERR_IO_PENDING) {
+      OnWriteDone(true, result);
+    }
+  } while (result == OK && data_being_sent_);
+}
+
+void WebSocketChannel::OnWriteDone(bool synchronous, int result) {
+  DCHECK(state_ != FRESHLY_CONSTRUCTED && state_ != CONNECTING);
+  DCHECK_NE(ERR_IO_PENDING, result);
+  DCHECK(data_being_sent_);
+  switch (result) {
+    case OK:
+      if (data_to_send_next_) {
+        data_being_sent_ = data_to_send_next_.Pass();
+        if (!synchronous) {
+          WriteFrames();
+        }
+      } else {
+        data_being_sent_.reset();
+        if (current_send_quota_ < send_quota_low_water_mark_) {
+          // TODO(ricea): Increase low_water_mark and high_water_mark if
+          // throughput is high, reduce them if throughput is low.  Low water
+          // mark needs to be >= the bandwidth delay product *of the IPC
+          // channel*. Because factors like context-switch time, thread wake-up
+          // time, and bus speed come into play it is complex and probably needs
+          // to be determined empirically.
+          DCHECK_LE(send_quota_low_water_mark_, send_quota_high_water_mark_);
+          // TODO(ricea): Truncate quota by the quota specified by the remote
+          // server, if the protocol in use supports quota.
+          int fresh_quota = send_quota_high_water_mark_ - current_send_quota_;
+          current_send_quota_ += fresh_quota;
+          event_interface_->OnFlowControl(fresh_quota);
+        }
+      }
+      return;
+
+    // If a recoverable error condition existed, it would go here.
+
+    default:
+      DCHECK_LT(result, 0)
+          << "WriteFrames() should only return OK or ERR_ codes";
+      stream_->Close();
+      state_ = CLOSED;
+      event_interface_->OnDropChannel(kWebSocketErrorAbnormalClosure,
+                                      "Abnormal Closure");
+      return;
+  }
+}
+
+void WebSocketChannel::ReadFrames() {
+  int result = OK;
+  do {
+    // This use of base::Unretained is safe because we own the WebSocketStream,
+    // and any pending reads will be cancelled when it is destroyed.
+    result = stream_->ReadFrames(
+        &read_frame_chunks_,
+        base::Bind(
+            &WebSocketChannel::OnReadDone, base::Unretained(this), false));
+    if (result != ERR_IO_PENDING) {
+      OnReadDone(true, result);
+    }
+  } while (result == OK);
+}
+
+void WebSocketChannel::OnReadDone(bool synchronous, int result) {
+  DCHECK(state_ != FRESHLY_CONSTRUCTED && state_ != CONNECTING);
+  DCHECK_NE(ERR_IO_PENDING, result);
+  switch (result) {
+    case OK:
+      // ReadFrames() must use ERR_CONNECTION_CLOSED for a closed connection
+      // with no data read, not an empty response.
+      DCHECK(!read_frame_chunks_.empty())
+          << "ReadFrames() returned OK, but nothing was read.";
+      for (size_t i = 0; i < read_frame_chunks_.size(); ++i) {
+        scoped_ptr<WebSocketFrameChunk> chunk(read_frame_chunks_[i]);
+        read_frame_chunks_[i] = NULL;
+        ProcessFrameChunk(chunk.Pass());
+      }
+      read_frame_chunks_.clear();
+      // We need to always keep a call to ReadFrames pending.
+      if (!synchronous) {
+        ReadFrames();
+      }
+      return;
+
+    default: {
+      DCHECK_LT(result, 0)
+          << "ReadFrames() should only return OK or ERR_ codes";
+      stream_->Close();
+      state_ = CLOSED;
+      uint16 code = kWebSocketErrorAbnormalClosure;
+      std::string reason = "Abnormal Closure";
+      if (closing_code_ != 0) {
+        code = closing_code_;
+        reason = closing_reason_;
+      }
+      event_interface_->OnDropChannel(code, reason);
+      return;
+    }
+  }
+}
+
+void WebSocketChannel::ProcessFrameChunk(
+    scoped_ptr<WebSocketFrameChunk> chunk) {
+  bool is_first_chunk = false;
+  if (chunk->header) {
+    DCHECK(current_frame_header_ == NULL)
+        << "Received the header for a new frame without notification that "
+        << "the previous frame was complete.";
+    is_first_chunk = true;
+    current_frame_header_.swap(chunk->header);
+    if (current_frame_header_->masked) {
+      // RFC6455 Section 5.1 "A client MUST close a connection if it detects a
+      // masked frame."
+      FailChannel(SEND_REAL_ERROR,
+                  kWebSocketErrorProtocolError,
+                  "Masked frame from server");
+      return;
+    }
+  }
+  if (!current_frame_header_) {
+    // If we rejected the previous chunk as invalid, then we will have reset
+    // current_frame_header_ to avoid using it. More chunks of the invalid frame
+    // may still arrive, so this is not necessarily a bug on our side. However,
+    // if this happens when state_ is CONNECTED, it is definitely a bug.
+    DCHECK(state_ != CONNECTED) << "Unexpected header-less frame received "
+                                << "(final_chunk = " << chunk->final_chunk
+                                << ", data size = " << chunk->data->size()
+                                << ")";
+    return;
+  }
+  scoped_refptr<IOBufferWithSize> data_buffer;
+  data_buffer.swap(chunk->data);
+  const bool is_final_chunk = chunk->final_chunk;
+  chunk.reset();
+  WebSocketFrameHeader::OpCode opcode = current_frame_header_->opcode;
+  if (WebSocketFrameHeader::IsKnownControlOpCode(opcode)) {
+    if (is_final_chunk) {
+      if (incomplete_control_frame_body_) {
+        VLOG(2) << "Rejoining a split control frame, opcode " << opcode;
+        data_buffer =
+            ConcatenateIOBuffers(incomplete_control_frame_body_, data_buffer);
+        incomplete_control_frame_body_ = NULL;
+      }
+    } else {
+      // TODO(ricea): Enforce a maximum size of 125 bytes on the control frames
+      // we accept.
+      VLOG(2) << "Encountered a split control frame, opcode " << opcode;
+      if (incomplete_control_frame_body_) {
+        // The really horrid case. We need to create a new IOBufferWithSize
+        // combining the new one and the old one. This should virtually never
+        // happen.
+        // TODO(ricea): This algorithm is O(N^2). Use a fixed 127-byte buffer
+        // instead.
+        VLOG(3) << "Hit the really horrid case";
+        incomplete_control_frame_body_ =
+            ConcatenateIOBuffers(incomplete_control_frame_body_, data_buffer);
+      } else {
+        // The merely horrid case. Store the IOBufferWithSize to use when the
+        // rest of the control frame arrives.
+        incomplete_control_frame_body_.swap(data_buffer);
+      }
+      return;
+    }
+  }
+
+  HandleFrame(opcode, is_first_chunk, is_final_chunk, data_buffer);
+
+  if (is_final_chunk) {
+    // Make sure we do not apply this frame header to any future chunks.
+    current_frame_header_.reset();
+  }
+}
+
+void WebSocketChannel::HandleFrame(
+    const WebSocketFrameHeader::OpCode opcode,
+    const bool is_first_chunk,
+    const bool is_final_chunk,
+    const scoped_refptr<IOBufferWithSize>& data_buffer) {
+  if (state_ == CLOSED) {

[tyoshino (SeeGerritForStatus), 2013/07/03 07:45:44]

o, not state_ == RECV_CLOSED || state_ == CLOSED?

[Adam Rice, 2013/07/03 10:25:26]

state_ cannot be RECV_CLOSED unless OnReadDone() is called recursively from
within SendClose(), something I'd prefer not to support. I have added a DCHECK
to discourage it.

[tyoshino (SeeGerritForStatus), 2013/07/04 12:54:26]

Got it. Thanks

+    std::string frame_name;
+    switch (opcode) {
+      case WebSocketFrameHeader::kOpCodeText:    // fall-thru
+      case WebSocketFrameHeader::kOpCodeBinary:  // fall-thru
+      case WebSocketFrameHeader::kOpCodeContinuation:
+        frame_name = "Data frame";
+        break;
+
+      case WebSocketFrameHeader::kOpCodePing:
+        frame_name = "Ping";
+        break;
+
+      case WebSocketFrameHeader::kOpCodePong:
+        frame_name = "Pong";
+        break;
+
+      case WebSocketFrameHeader::kOpCodeClose:
+        frame_name = "Close";
+        break;
+
+      default:
+        frame_name = "Unknown frame type";
+        break;
+    }
+    // SEND_REAL_ERROR makes no difference here, as we won't send another Close
+    // frame.
+    FailChannel(SEND_REAL_ERROR,
+                kWebSocketErrorProtocolError,
+                frame_name + " received after close");
+    return;
+  }
+  switch (opcode) {
+    case WebSocketFrameHeader::kOpCodeText:    // fall-thru
+    case WebSocketFrameHeader::kOpCodeBinary:  // fall-thru
+    case WebSocketFrameHeader::kOpCodeContinuation:
+      if (state_ == CONNECTED) {
+        const bool final = is_final_chunk && current_frame_header_->final;
+        // TODO(ricea): Can this copy be eliminated?
+        const char* const data_begin = data_buffer->data();
+        const char* const data_end = data_begin + data_buffer->size();
+        const std::vector<char> data(data_begin, data_end);
+        // TODO(ricea): Handle the (improbable) case when ReadFrames returns far
+        // more data at once than we want to send in a single IPC (in which case
+        // we need to buffer the data and return to the event loop with a
+        // callback to send the rest in 32K chunks).
+
+        // Send the received frame to the renderer process.
+        event_interface_->OnDataFrame(
+            final,
+            is_first_chunk ? opcode : WebSocketFrameHeader::kOpCodeContinuation,
+            data);
+      } else {
+        VLOG(3) << "Ignored data packet received in state " << state_;
+      }
+      return;
+
+    case WebSocketFrameHeader::kOpCodePing:
+      VLOG(1) << "Got Ping of size " << data_buffer->size();
+      if (state_ == CONNECTED) {
+        SendIOBufferWithSize(
+            true, WebSocketFrameHeader::kOpCodePong, data_buffer);
+      } else {
+        VLOG(3) << "Ignored ping in state " << state_;
+      }
+      return;
+
+    case WebSocketFrameHeader::kOpCodePong:
+      VLOG(1) << "Got Pong of size " << data_buffer->size();
+      // We do not need to do anything with pong messages.
+      return;
+
+    case WebSocketFrameHeader::kOpCodeClose: {
+      uint16 code = kWebSocketNormalClosure;
+      std::string reason;
+      ParseClose(data_buffer, &code, &reason);
+      // TODO(ricea): Find a way to safely log the message from the close
+      // message (escape control codes and so on).
+      VLOG(1) << "Got Close with code " << code;
+      switch (state_) {
+        case CONNECTED:
+          state_ = RECV_CLOSED;
+          SendClose(code, reason);  // Sets state_ to CLOSED
+          event_interface_->OnClosingHandshake();
+          closing_code_ = code;
+          closing_reason_ = reason;
+          break;
+
+        case SEND_CLOSED:
+          state_ = CLOSED;
+          // From RFC6455 section 7.1.5: "Each endpoint
+          // will see the status code sent by the other end as _The WebSocket
+          // Connection Close Code_."
+          closing_code_ = code;
+          closing_reason_ = reason;
+          break;
+
+        default:
+          LOG(DFATAL) << "Got Close in unexpected state " << state_;
+          break;
+      }
+      return;
+    }
+
+    default:
+      FailChannel(
+          SEND_REAL_ERROR, kWebSocketErrorProtocolError, "Unknown opcode");
+      return;
+  }
+}
+
+void WebSocketChannel::SendFlowControl(int64 quota) {
+  DCHECK_EQ(CONNECTED, state_);
+  // TODO(ricea): Add interface to WebSocketStream and implement.
+  // stream_->SendFlowControl(quota);
+}
+
+void WebSocketChannel::StartClosingHandshake(uint16 code,
+                                             const std::string& reason) {
+  if (state_ == SEND_CLOSED || state_ == CLOSED) {
+    VLOG(1) << "StartClosingHandshake called in state " << state_
+            << ". This may be a bug, or a harmless race.";
+    return;
+  }
+  if (state_ != CONNECTED) {
+    NOTREACHED() << "StartClosingHandshake() called in state " << state_;
+    return;
+  }
+  // TODO(ricea): Validate |code|? Check that |reason| is valid UTF-8?
+  // TODO(ricea): There should be a timeout for the closing handshake.
+  SendClose(code, reason);  // Sets state_ to SEND_CLOSED
+}
+
+void WebSocketChannel::FailChannel(ExposeError expose,
+                                   uint16 code,
+                                   const std::string& reason) {
+  DCHECK(state_ != FRESHLY_CONSTRUCTED && state_ != CONNECTING);
+  // TODO(ricea): Logging.
+  State old_state = state_;
+  if (state_ == CONNECTED) {
+    uint16 send_code = kWebSocketErrorGoingAway;
+    std::string send_reason = "Internal Error";
+    if (expose == SEND_REAL_ERROR) {
+      send_code = code;
+      send_reason = reason;
+    }
+    SendClose(send_code, send_reason);  // Sets state_ to SEND_CLOSED
+  }
+  // Careful study of RFC6455 section 7.1.7 and 7.1.1 indicates we should close
+  // the connection ourselves without waiting for the closing handshake.
+  stream_->Close();
+  state_ = CLOSED;
+
+  // We may be in the middle of processing several chunks. We should not re-use
+  // the frame header.
+  current_frame_header_.reset();
+  if (old_state != CLOSED) {
+    event_interface_->OnDropChannel(code, reason);
+  }
+}
+
+void WebSocketChannel::SendClose(uint16 code, const std::string& reason) {
+  DCHECK(state_ == CONNECTED || state_ == RECV_CLOSED);
+  uint64 payload_length = kWebSocketCloseCodeLength + reason.length();
+  scoped_refptr<IOBufferWithSize> body = new IOBufferWithSize(payload_length);
+  WriteBigEndian(body->data(), code);
+  COMPILE_ASSERT(sizeof(code) == kWebSocketCloseCodeLength,
+                 they_should_both_be_two);
+  std::copy(
+      reason.begin(), reason.end(), body->data() + kWebSocketCloseCodeLength);
+  SendIOBufferWithSize(true, WebSocketFrameHeader::kOpCodeClose, body);
+  state_ = state_ == CONNECTED ? SEND_CLOSED : CLOSED;
+}
+
+void WebSocketChannel::ParseClose(const scoped_refptr<IOBufferWithSize>& buffer,
+                                  uint16* code,
+                                  std::string* reason) {
+  const char* data = buffer->data();
+  size_t size = base::checked_numeric_cast<size_t>(buffer->size());
+  reason->clear();
+  if (size < kWebSocketCloseCodeLength) {
+    *code = kWebSocketErrorNoStatusReceived;
+    if (size != 0) {
+      VLOG(1) << "Close frame with payload size " << size << " received "
+              << "(the first byte is " << std::hex << static_cast<int>(data[0])
+              << ")";
+      return;
+    }
+    return;
+  }
+  uint16 unchecked_code = 0;
+  ReadBigEndian(data, &unchecked_code);
+  COMPILE_ASSERT(sizeof(unchecked_code) == kWebSocketCloseCodeLength,
+                 they_should_both_be_two_bytes);
+  if (unchecked_code >= static_cast<uint16>(kWebSocketNormalClosure) &&
+      unchecked_code <=
+          static_cast<uint16>(kWebSocketErrorPrivateReservedMax)) {
+    *code = unchecked_code;
+  } else {
+    VLOG(1) << "Close frame contained code outside of the valid range: "
+            << unchecked_code;
+    *code = kWebSocketErrorAbnormalClosure;
+  }
+  std::string text(data + kWebSocketCloseCodeLength, data + size);
+  // TODO(ricea): Is this check strict enough? In particular, check the
+  // "Security Considerations" from RFC3629.
+  if (IsStringUTF8(text)) {
+    using std::swap;
+    swap(*reason, text);
+  }
+}
+
+}  // namespace net