Drop buffers in idle SSLClientSockets (and SSLServerSockets).

net/socket/socket_bio_adapter.h

+// Copyright 2016 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.
+
+#ifndef NET_SOCKET_SOCKET_BIO_ADAPTER_H_
+#define NET_SOCKET_SOCKET_BIO_ADAPTER_H_
+
+#include <openssl/base.h>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/completion_callback.h"
+#include "net/base/net_export.h"
+
+namespace net {
+
+class GrowableIOBuffer;
+class IOBuffer;
+class StreamSocket;
+
+// An adapter to convert between StreamSocket and OpenSSL BIO I/O models.
+//
+// BIO exposes a UNIX-like interface where BIO_read and BIO_write may either
+// succeed synchronously or be retried (with no memory between calls).
+// StreamSocket exposes an asynchronous interface where an asynchronous
+// operation continues running and completes with a callback.
+//
+// For reading, SocketBIOAdapter maintains a buffer to pass to
+// StreamSocket::Read. Once that Read completes, BIO_read synchronously drains
+// the buffer and signals BIO_should_read once empty.
+//
+// For writing, SocketBIOAdapter maintains a ring buffer of data to be written
+// to the StreamSocket. BIO_write synchronously copies data into the buffer or
+// signals BIO_should_write if the buffer is full. The ring buffer is drained
+// asynchronously into the socket. Note this means write errors are reported at
+// a later BIO_write.
+//
+// To work around this delay, write errors are also surfaced out of
+// BIO_read. Otherwise a failure in the final BIO_write of an application may go
+// unnoticed. If this occurs, OnReadReady will be signaled as if it were a read
+// error. See https://crbug.com/249848.
+class NET_EXPORT_PRIVATE SocketBIOAdapter {
+ public:
+  // A delegate interface for when the sockets are ready. BIO assumes external
+  // knowledge of when to retry operations (such as a select() loop for UNIX),
+  // which is signaled out of StreamSocket's callbacks here.
+  //
+  // Callers should implement these methods and, when signaled, retry the
+  // BIO_read or BIO_write. This usually is done by retrying a higher-level
+  // operation, such as SSL_read or SSL_write.
+  //
+  // Callers may assume that OnReadReady and OnWriteReady will only be called
+  // from a PostTask or StreamSocket callback.
+  class Delegate {

[Ryan Sleevi, 2016/10/18 01:30:17]

nit: Add protected virtual dtor, since you don't require explicit memory
management as part of your API contract (that is, Delegate* outlives the
BIOAdapter)

[davidben, 2016/10/18 20:49:11]

Done.

+   public:
+    // Called when the BIO is ready to handle BIO_read, after having previously
+    // been blocked.
+    virtual void OnReadReady() = 0;
+
+    // Called when the BIO is ready to handle BIO_write, after having previously
+    // been blocked.
+    virtual void OnWriteReady() = 0;
+  };
+
+  // Creates a new SocketBIOAdapter for the specified socket. |socket| and
+  // |delegate| must remain valid for the lifetime of the SocketBIOAdapter.
+  SocketBIOAdapter(StreamSocket* socket,
+                   int read_buffer_capacity,
+                   int write_buffer_capacity,
+                   Delegate* delegate);
+  ~SocketBIOAdapter();
+
+  BIO* bio() { return bio_.get(); }
+
+  // Returns true if any data has been read from the underlying StreamSocket,
+  // but not yet consumed by the BIO.
+  bool HasPendingReadData();
+
+ private:
+  int BIORead(char* out, int len);
+  void HandleSocketReadResult(int result);
+  void OnSocketReadComplete(int result);
+
+  int BIOWrite(const char* in, int len);
+  void SocketWrite();
+  void HandleSocketWriteResult(int result);
+  void OnSocketWriteComplete(int result);
+  void CallOnReadReady();
+
+  static SocketBIOAdapter* GetAdapter(BIO* bio);
+  static int BIOReadWrapper(BIO* bio, char* out, int len);
+  static int BIOWriteWrapper(BIO* bio, const char* in, int len);
+  static long BIOCtrlWrapper(BIO* bio, int cmd, long larg, void* parg);
+
+  static const BIO_METHOD kBIOMethod;
+
+  bssl::UniquePtr<BIO> bio_;
+
+  // The pointer is non-owning so this class may be used with both
+  // ClientSocketHandles and raw StreamSockets.
+  StreamSocket* socket_;
+
+  CompletionCallback read_callback_;
+  CompletionCallback write_callback_;
+
+  // The capacity of the read buffer.
+  int read_buffer_capacity_;
+  // A buffer containing data from the most recent socket Read(). The buffer is
+  // deallocated when unused.
+  scoped_refptr<IOBuffer> read_buffer_;
+  // The number of bytes of read_buffer_ consumed.
+  int read_offset_;
+  // The result of the most recent socket Read(). If ERR_IO_PENDING, there is a
+  // socket Read() in progress. If another error, Read() has failed. Otherwise,
+  // it is the number of bytes in the buffer (zero if empty).
+  int read_result_;
+
+  // The capacity of the write buffer.
+  int write_buffer_capacity_;
+  // A ring buffer of data to be written to the transport. The offset of the
+  // buffer is the start of the ring buffer and is advanced on successful
+  // Write(). The buffer is deallocated when unused.
+  scoped_refptr<GrowableIOBuffer> write_buffer_;
+  // The number of bytes of data in write_buffer_.
+  int write_buffer_used_;
+  // The most recent socket Write() error. If ERR_IO_PENDING, there is a socket
+  // Write() in progress. If OK, there is no socket Write() in progress and none
+  // have failed.
+  int write_error_;
+
+  Delegate* delegate_;
+
+  base::WeakPtrFactory<SocketBIOAdapter> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(SocketBIOAdapter);
+};
+
+}  // namespace net
+
+#endif  // NET_SOCKET_SOCKET_BIO_ADAPTER_H_