SOCKS v5 implementation

The implementation is incomplete as it does not support any authentication methods and does not have a UDP layer.

BUG=469
TEST=unittests (included)

Review URL: http://codereview.chromium.org/150187

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@20724 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 887 insertions, 0 deletions

diff --git a/net/socket/socks5_client_socket.cc b/net/socket/socks5_client_socket.cc
new file mode 100644
index 0000000..8876bb9
--- /dev/null
+++ b/net/socket/socks5_client_socket.cc
@@ -0,0 +1,430 @@
+// Copyright (c) 2009 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/socket/socks5_client_socket.h"
+
+#include "base/basictypes.h"
+#include "build/build_config.h"
+#if defined(OS_WIN)
+#include <ws2tcpip.h>
+#elif defined(OS_POSIX)
+#include <netdb.h>
+#endif
+#include "base/compiler_specific.h"
+#include "base/trace_event.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_util.h"
+
+namespace net {
+
+const unsigned int SOCKS5ClientSocket::kGreetReadHeaderSize = 2;
+const unsigned int SOCKS5ClientSocket::kWriteHeaderSize = 10;
+const unsigned int SOCKS5ClientSocket::kReadHeaderSize = 5;
+const uint8 SOCKS5ClientSocket::kSOCKS5Version = 0x05;
+const uint8 SOCKS5ClientSocket::kTunnelCommand = 0x01;
+const uint8 SOCKS5ClientSocket::kNullByte = 0x00;
+
+COMPILE_ASSERT(sizeof(struct in_addr) == 4, incorrect_system_size_of_IPv4);
+COMPILE_ASSERT(sizeof(struct in6_addr) == 16, incorrect_system_size_of_IPv6);
+
+SOCKS5ClientSocket::SOCKS5ClientSocket(ClientSocket* transport_socket,
+    const HostResolver::RequestInfo& req_info,
+    HostResolver* host_resolver)
+    : ALLOW_THIS_IN_INITIALIZER_LIST(
+          io_callback_(this, &SOCKS5ClientSocket::OnIOComplete)),
+      transport_(transport_socket),
+      next_state_(STATE_NONE),
+      address_type_(kEndPointUnresolved),
+      user_callback_(NULL),
+      completed_handshake_(false),
+      bytes_sent_(0),
+      bytes_received_(0),
+      read_header_size(kReadHeaderSize),
+      host_resolver_(host_resolver),
+      host_request_info_(req_info) {
+}
+
+SOCKS5ClientSocket::~SOCKS5ClientSocket() {
+  Disconnect();
+}
+
+int SOCKS5ClientSocket::Connect(CompletionCallback* callback) {
+  DCHECK(transport_.get());
+  DCHECK(transport_->IsConnected());
+  DCHECK_EQ(STATE_NONE, next_state_);
+  DCHECK(!user_callback_);
+
+  // If already connected, then just return OK.
+  if (completed_handshake_)
+    return OK;
+
+  next_state_ = STATE_RESOLVE_HOST;
+
+  int rv = DoLoop(OK);
+  if (rv == ERR_IO_PENDING)
+    user_callback_ = callback;
+  return rv;
+}
+
+void SOCKS5ClientSocket::Disconnect() {
+  completed_handshake_ = false;
+  transport_->Disconnect();
+}
+
+bool SOCKS5ClientSocket::IsConnected() const {
+  return completed_handshake_ && transport_->IsConnected();
+}
+
+bool SOCKS5ClientSocket::IsConnectedAndIdle() const {
+  return completed_handshake_ && transport_->IsConnectedAndIdle();
+}
+
+// Read is called by the transport layer above to read. This can only be done
+// if the SOCKS handshake is complete.
+int SOCKS5ClientSocket::Read(IOBuffer* buf, int buf_len,
+                            CompletionCallback* callback) {
+  DCHECK(completed_handshake_);
+  DCHECK_EQ(STATE_NONE, next_state_);
+  DCHECK(!user_callback_);
+
+  return transport_->Read(buf, buf_len, callback);
+}
+
+// Write is called by the transport layer. This can only be done if the
+// SOCKS handshake is complete.
+int SOCKS5ClientSocket::Write(IOBuffer* buf, int buf_len,
+                             CompletionCallback* callback) {
+  DCHECK(completed_handshake_);
+  DCHECK_EQ(STATE_NONE, next_state_);
+  DCHECK(!user_callback_);
+
+  return transport_->Write(buf, buf_len, callback);
+}
+
+void SOCKS5ClientSocket::DoCallback(int result) {
+  DCHECK_NE(ERR_IO_PENDING, result);
+  DCHECK(user_callback_);
+
+  // Since Run() may result in Read being called,
+  // clear user_callback_ up front.
+  CompletionCallback* c = user_callback_;
+  user_callback_ = NULL;
+  DLOG(INFO) << "Finished setting up SOCKSv5 handshake";
+  c->Run(result);
+}
+
+void SOCKS5ClientSocket::OnIOComplete(int result) {
+  DCHECK_NE(STATE_NONE, next_state_);
+  int rv = DoLoop(result);
+  if (rv != ERR_IO_PENDING)
+    DoCallback(rv);
+}
+
+int SOCKS5ClientSocket::DoLoop(int last_io_result) {
+  DCHECK_NE(next_state_, STATE_NONE);
+  int rv = last_io_result;
+  do {
+    State state = next_state_;
+    next_state_ = STATE_NONE;
+    switch (state) {
+      case STATE_RESOLVE_HOST:
+        DCHECK_EQ(OK, rv);
+        rv = DoResolveHost();
+        break;
+      case STATE_RESOLVE_HOST_COMPLETE:
+        rv = DoResolveHostComplete(rv);
+        break;
+      case STATE_GREET_WRITE:
+        DCHECK_EQ(OK, rv);
+        rv = DoGreetWrite();
+        break;
+      case STATE_GREET_WRITE_COMPLETE:
+        rv = DoGreetWriteComplete(rv);
+        break;
+      case STATE_GREET_READ:
+        DCHECK_EQ(OK, rv);
+        rv = DoGreetRead();
+        break;
+      case STATE_GREET_READ_COMPLETE:
+        rv = DoGreetReadComplete(rv);
+        break;
+      case STATE_HANDSHAKE_WRITE:
+        DCHECK_EQ(OK, rv);
+        rv = DoHandshakeWrite();
+        break;
+      case STATE_HANDSHAKE_WRITE_COMPLETE:
+        rv = DoHandshakeWriteComplete(rv);
+        break;
+      case STATE_HANDSHAKE_READ:
+        DCHECK_EQ(OK, rv);
+        rv = DoHandshakeRead();
+        break;
+      case STATE_HANDSHAKE_READ_COMPLETE:
+        rv = DoHandshakeReadComplete(rv);
+        break;
+      default:
+        NOTREACHED() << "bad state";
+        rv = ERR_UNEXPECTED;
+        break;
+    }
+  } while (rv != ERR_IO_PENDING && next_state_ != STATE_NONE);
+  return rv;
+}
+
+int SOCKS5ClientSocket::DoResolveHost() {
+  DCHECK_EQ(kEndPointUnresolved, address_type_);
+
+  next_state_ = STATE_RESOLVE_HOST_COMPLETE;
+  return host_resolver_.Resolve(host_request_info_, &addresses_, &io_callback_);
+}
+
+int SOCKS5ClientSocket::DoResolveHostComplete(int result) {
+  DCHECK_EQ(kEndPointUnresolved, address_type_);
+
+  bool ok = (result == OK);
+  next_state_ = STATE_GREET_WRITE;
+  if (ok) {
+    DCHECK(addresses_.head());
+    struct sockaddr* host_info = addresses_.head()->ai_addr;
+    if (host_info->sa_family == AF_INET) {
+      address_type_ = kEndPointResolvedIPv4;
+    } else if (host_info->sa_family == AF_INET6) {
+      address_type_ = kEndPointResolvedIPv6;
+    }
+  } else {
+    address_type_ = kEndPointFailedDomain;
+  }
+
+  buffer_.clear();
+
+  // Even if DNS resolution fails, we send OK since the server
+  // resolves the domain.
+  return OK;
+}
+
+const char kSOCKS5GreetWriteData[] = { 0x05, 0x01, 0x00 };  // no authentication
+const char kSOCKS5GreetReadData[] = { 0x05, 0x00 };
+
+int SOCKS5ClientSocket::DoGreetWrite() {
+  if (buffer_.empty()) {
+    buffer_ = std::string(kSOCKS5GreetWriteData,
+                          arraysize(kSOCKS5GreetWriteData));
+    bytes_sent_ = 0;
+  }
+
+  next_state_ = STATE_GREET_WRITE_COMPLETE;
+  size_t handshake_buf_len = buffer_.size() - bytes_sent_;
+  handshake_buf_ = new IOBuffer(handshake_buf_len);
+  memcpy(handshake_buf_->data(), &buffer_.data()[bytes_sent_],
+         handshake_buf_len);
+  return transport_->Write(handshake_buf_, handshake_buf_len, &io_callback_);
+}
+
+int SOCKS5ClientSocket::DoGreetWriteComplete(int result) {
+  if (result < 0)
+    return result;
+
+  bytes_sent_ += result;
+  if (bytes_sent_ == buffer_.size()) {
+    buffer_.clear();
+    bytes_received_ = 0;
+    next_state_ = STATE_GREET_READ;
+  } else {
+    next_state_ = STATE_GREET_WRITE;
+  }
+  return OK;
+}
+
+int SOCKS5ClientSocket::DoGreetRead() {
+  next_state_ = STATE_GREET_READ_COMPLETE;
+  size_t handshake_buf_len = kGreetReadHeaderSize - bytes_received_;
+  handshake_buf_ = new IOBuffer(handshake_buf_len);
+  return transport_->Read(handshake_buf_, handshake_buf_len, &io_callback_);
+}
+
+int SOCKS5ClientSocket::DoGreetReadComplete(int result) {
+  if (result < 0)
+    return result;
+
+  if (result == 0)
+    return ERR_CONNECTION_CLOSED;  // Unexpected socket close
+
+  bytes_received_ += result;
+  buffer_.append(handshake_buf_->data(), result);
+  if (bytes_received_ < kGreetReadHeaderSize) {
+    next_state_ = STATE_GREET_READ;
+    return OK;
+  }
+
+  // Got the greet data.
+  if (buffer_[0] != kSOCKS5Version || buffer_[1] != 0x00)
+    return ERR_INVALID_RESPONSE;  // Unknown error
+
+  buffer_.clear();
+  next_state_ = STATE_HANDSHAKE_WRITE;
+  return OK;
+}
+
+int SOCKS5ClientSocket::BuildHandshakeWriteBuffer(std::string* handshake)
+    const {
+  DCHECK_NE(kEndPointUnresolved, address_type_);
+  DCHECK(handshake->empty());
+
+  handshake->push_back(kSOCKS5Version);
+  handshake->push_back(kTunnelCommand);  // Connect command
+  handshake->push_back(kNullByte);  // Reserved null
+
+  handshake->push_back(address_type_);  // The type of connection
+  if (address_type_ == kEndPointFailedDomain) {
+    if(256 <= host_request_info_.hostname().size())
+      return ERR_ADDRESS_INVALID;
+
+    // First add the size of the hostname, followed by the hostname.
+    handshake->push_back(static_cast<unsigned char>(
+        host_request_info_.hostname().size()));
+    handshake->append(host_request_info_.hostname());
+
+  } else if (address_type_ == kEndPointResolvedIPv4) {
+    struct sockaddr_in* ipv4_host =
+        reinterpret_cast<struct sockaddr_in*>(addresses_.head()->ai_addr);
+    handshake->append(reinterpret_cast<char*>(&ipv4_host->sin_addr),
+                      sizeof(ipv4_host->sin_addr));
+
+  } else if (address_type_ == kEndPointResolvedIPv6) {
+    struct sockaddr_in6* ipv6_host =
+        reinterpret_cast<struct sockaddr_in6*>(addresses_.head()->ai_addr);
+    handshake->append(reinterpret_cast<char*>(&ipv6_host->sin6_addr),
+                      sizeof(ipv6_host->sin6_addr));
+
+  } else {
+    NOTREACHED();
+  }
+
+  uint16 nw_port = htons(host_request_info_.port());
+  handshake->append(reinterpret_cast<char*>(&nw_port), sizeof(nw_port));
+  return OK;
+}
+
+// Writes the SOCKS handshake data to the underlying socket connection.
+int SOCKS5ClientSocket::DoHandshakeWrite() {
+  next_state_ = STATE_HANDSHAKE_WRITE_COMPLETE;
+
+  if (buffer_.empty()) {
+    int rv = BuildHandshakeWriteBuffer(&buffer_);
+    if (rv != OK)
+      return rv;
+    bytes_sent_ = 0;
+  }
+
+  int handshake_buf_len = buffer_.size() - bytes_sent_;
+  DCHECK_LT(0, handshake_buf_len);
+  handshake_buf_ = new IOBuffer(handshake_buf_len);
+  memcpy(handshake_buf_->data(), &buffer_[bytes_sent_],
+         handshake_buf_len);
+  return transport_->Write(handshake_buf_, handshake_buf_len, &io_callback_);
+}
+
+int SOCKS5ClientSocket::DoHandshakeWriteComplete(int result) {
+  DCHECK_NE(kEndPointUnresolved, address_type_);
+
+  if (result < 0)
+    return result;
+
+  // We ignore the case when result is 0, since the underlying Write
+  // may return spurious writes while waiting on the socket.
+
+  bytes_sent_ += result;
+  if (bytes_sent_ == buffer_.size()) {
+    next_state_ = STATE_HANDSHAKE_READ;
+    buffer_.clear();
+  } else if (bytes_sent_ < buffer_.size()) {
+    next_state_ = STATE_HANDSHAKE_WRITE;
+  } else {
+    NOTREACHED();
+  }
+
+  return OK;
+}
+
+int SOCKS5ClientSocket::DoHandshakeRead() {
+  DCHECK_NE(kEndPointUnresolved, address_type_);
+
+  next_state_ = STATE_HANDSHAKE_READ_COMPLETE;
+
+  if (buffer_.empty()) {
+    bytes_received_ = 0;
+    read_header_size = kReadHeaderSize;
+  }
+
+  int handshake_buf_len = read_header_size - bytes_received_;
+  handshake_buf_ = new IOBuffer(handshake_buf_len);
+  return transport_->Read(handshake_buf_, handshake_buf_len, &io_callback_);
+}
+
+int SOCKS5ClientSocket::DoHandshakeReadComplete(int result) {
+  DCHECK_NE(kEndPointUnresolved, address_type_);
+
+  if (result < 0)
+    return result;
+
+  // The underlying socket closed unexpectedly.
+  if (result == 0)
+    return ERR_CONNECTION_CLOSED;
+
+  buffer_.append(handshake_buf_->data(), result);
+  bytes_received_ += result;
+
+  // When the first few bytes are read, check how many more are required
+  // and accordingly increase them
+  if (bytes_received_ == kReadHeaderSize) {
+    // TODO(arindam): add error codes to net/error_list.h
+    if (buffer_[0] != kSOCKS5Version || buffer_[2] != kNullByte)
+      return ERR_INVALID_RESPONSE;
+    if (buffer_[1] != 0x00)
+      return ERR_FAILED;
+
+    // We check the type of IP/Domain the server returns and accordingly
+    // increase the size of the response. For domains, we need to read the
+    // size of the domain, so the initial request size is upto the domain
+    // size. Since for IPv4/IPv6 the size is fixed and hence no 'size' is
+    // read, we substract 1 byte from the additional request size.
+    SocksEndPointAddressType address_type =
+        static_cast<SocksEndPointAddressType>(buffer_[3]);
+    if (address_type == kEndPointFailedDomain)
+      read_header_size += static_cast<uint8>(buffer_[4]);
+    else if (address_type == kEndPointResolvedIPv4)
+      read_header_size += sizeof(struct in_addr) - 1;
+    else if (address_type == kEndPointResolvedIPv6)
+      read_header_size += sizeof(struct in6_addr) - 1;
+    else
+      return ERR_INVALID_RESPONSE;
+
+    read_header_size += 2;  // for the port.
+    next_state_ = STATE_HANDSHAKE_READ;
+    return OK;
+  }
+
+  // When the final bytes are read, setup handshake. We ignore the rest
+  // of the response since they represent the SOCKSv5 endpoint and have
+  // no use when doing a tunnel connection.
+  if (bytes_received_ == read_header_size) {
+    completed_handshake_ = true;
+    buffer_.clear();
+    next_state_ = STATE_NONE;
+    return OK;
+  }
+
+  next_state_ = STATE_HANDSHAKE_READ;
+  return OK;
+}
+
+#if defined(OS_LINUX)
+int SOCKS5ClientSocket::GetPeerName(struct sockaddr* name,
+                                    socklen_t* namelen) {
+  return transport_->GetPeerName(name, namelen);
+}
+#endif
+
+}  // namespace net
+
diff --git a/net/socket/socks5_client_socket.h b/net/socket/socks5_client_socket.h
new file mode 100644
index 0000000..1a5672d
--- /dev/null
+++ b/net/socket/socks5_client_socket.h
@@ -0,0 +1,151 @@
+// Copyright (c) 2009 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_SOCKS5_CLIENT_SOCKET_H_
+#define NET_SOCKET_SOCKS5_CLIENT_SOCKET_H_
+
+#include <string>
+
+#include "base/logging.h"
+#include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/address_list.h"
+#include "net/base/completion_callback.h"
+#include "net/base/host_resolver.h"
+#include "net/base/net_errors.h"
+#include "net/socket/client_socket.h"
+#include "testing/gtest/include/gtest/gtest_prod.h"
+
+namespace net {
+
+// This ClientSocket is used to setup a SOCKSv5 handshake with a socks proxy.
+// Currently no SOCKSv5 authentication is supported.
+class SOCKS5ClientSocket : public ClientSocket {
+ public:
+  // Takes ownership of the |transport_socket|, which should already be
+  // connected by the time Connect() is called.
+  //
+  // |req_info| contains the hostname and port to which the socket above will
+  // communicate to via the SOCKS layer.
+  SOCKS5ClientSocket(ClientSocket* transport_socket,
+                     const HostResolver::RequestInfo& req_info,
+                     HostResolver* host_resolver);
+
+  // On destruction Disconnect() is called.
+  virtual ~SOCKS5ClientSocket();
+
+  // ClientSocket methods:
+
+  // Does the SOCKS handshake and completes the protocol.
+  virtual int Connect(CompletionCallback* callback);
+  virtual void Disconnect();
+  virtual bool IsConnected() const;
+  virtual bool IsConnectedAndIdle() const;
+
+  // Socket methods:
+  virtual int Read(IOBuffer* buf, int buf_len, CompletionCallback* callback);
+  virtual int Write(IOBuffer* buf, int buf_len, CompletionCallback* callback);
+
+#if defined(OS_LINUX)
+  virtual int GetPeerName(struct sockaddr* name, socklen_t* namelen);
+#endif
+
+ private:
+  FRIEND_TEST(SOCKS5ClientSocketTest, IPv6Domain);
+  FRIEND_TEST(SOCKS5ClientSocketTest, FailedDNS);
+  FRIEND_TEST(SOCKS5ClientSocketTest, CompleteHandshake);
+
+  enum State {
+    STATE_RESOLVE_HOST,
+    STATE_RESOLVE_HOST_COMPLETE,
+    STATE_GREET_WRITE,
+    STATE_GREET_WRITE_COMPLETE,
+    STATE_GREET_READ,
+    STATE_GREET_READ_COMPLETE,
+    STATE_HANDSHAKE_WRITE,
+    STATE_HANDSHAKE_WRITE_COMPLETE,
+    STATE_HANDSHAKE_READ,
+    STATE_HANDSHAKE_READ_COMPLETE,
+    STATE_NONE,
+  };
+
+  // State of the SOCKSv5 handshake. Before host resolution all connections
+  // are kEndPointFailedDomain. If DNS lookup fails, we move to
+  // kEndPointFailedDomain, otherwise the IPv4/IPv6 address as resolved.
+  enum SocksEndPointAddressType {
+    kEndPointUnresolved,
+    kEndPointFailedDomain = 0x03,
+    kEndPointResolvedIPv4 = 0x01,
+    kEndPointResolvedIPv6 = 0x04,
+  };
+
+  static const unsigned int kGreetReadHeaderSize;
+  static const unsigned int kWriteHeaderSize;
+  static const unsigned int kReadHeaderSize;
+  static const uint8 kSOCKS5Version;
+  static const uint8 kTunnelCommand;
+  static const uint8 kNullByte;
+
+  void DoCallback(int result);
+  void OnIOComplete(int result);
+
+  int DoLoop(int last_io_result);
+  int DoResolveHost();
+  int DoResolveHostComplete(int result);
+  int DoHandshakeRead();
+  int DoHandshakeReadComplete(int result);
+  int DoHandshakeWrite();
+  int DoHandshakeWriteComplete(int result);
+  int DoGreetRead();
+  int DoGreetReadComplete(int result);
+  int DoGreetWrite();
+  int DoGreetWriteComplete(int result);
+
+  // Writes the SOCKS handshake buffer into |handshake|
+  // and return OK on success.
+  int BuildHandshakeWriteBuffer(std::string* handshake) const;
+
+  CompletionCallbackImpl<SOCKS5ClientSocket> io_callback_;
+
+  // Stores the underlying socket.
+  scoped_ptr<ClientSocket> transport_;
+
+  State next_state_;
+  SocksEndPointAddressType address_type_;
+
+  // Stores the callback to the layer above, called on completing Connect().
+  CompletionCallback* user_callback_;
+
+  // This IOBuffer is used by the class to read and write
+  // SOCKS handshake data. The length contains the expected size to
+  // read or write.
+  scoped_refptr<IOBuffer> handshake_buf_;
+
+  // While writing, this buffer stores the complete write handshake data.
+  // While reading, it stores the handshake information received so far.
+  std::string buffer_;
+
+  // This becomes true when the SOCKS handshake has completed and the
+  // overlying connection is free to communicate.
+  bool completed_handshake_;
+
+  // These contain the bytes sent / received by the SOCKS handshake.
+  size_t bytes_sent_;
+  size_t bytes_received_;
+
+  size_t read_header_size;
+
+  // Used to resolve the hostname to which the SOCKS proxy will connect.
+  SingleRequestHostResolver host_resolver_;
+  AddressList addresses_;
+  HostResolver::RequestInfo host_request_info_;
+
+  DISALLOW_COPY_AND_ASSIGN(SOCKS5ClientSocket);
+};
+
+}  // namespace net
+
+#endif  // NET_SOCKET_SOCKS5_CLIENT_SOCKET_H_
+
diff --git a/net/socket/socks5_client_socket_unittest.cc b/net/socket/socks5_client_socket_unittest.cc
new file mode 100644
index 0000000..8f763c4
--- /dev/null
+++ b/net/socket/socks5_client_socket_unittest.cc
@@ -0,0 +1,306 @@
+// Copyright (c) 2009 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/socket/socks5_client_socket.h"
+
+#include <map>
+#include "build/build_config.h"
+#if defined(OS_WIN)
+#include <ws2tcpip.h>
+#elif defined(OS_POSIX)
+#include <netdb.h>
+#endif
+#include "net/base/address_list.h"
+#include "net/base/host_resolver_unittest.h"
+#include "net/base/test_completion_callback.h"
+#include "net/base/winsock_init.h"
+#include "net/socket/client_socket_factory.h"
+#include "net/socket/socket_test_util.h"
+#include "net/socket/tcp_client_socket.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/platform_test.h"
+
+//-----------------------------------------------------------------------------
+
+namespace net {
+
+// Base class to test SOCKS5ClientSocket
+class SOCKS5ClientSocketTest : public PlatformTest {
+ public:
+  SOCKS5ClientSocketTest();
+  // Create a SOCKSClientSocket on top of a MockSocket.
+  SOCKS5ClientSocket* BuildMockSocket(MockRead reads[],
+                                      MockWrite writes[],
+                                      const std::string& hostname,
+                                      int port);
+  virtual void SetUp();
+
+ protected:
+  const uint16 kNwPort;
+  scoped_ptr<SOCKS5ClientSocket> user_sock_;
+  AddressList address_list_;
+  ClientSocket* tcp_sock_;
+  ScopedHostMapper host_mapper_;
+  TestCompletionCallback callback_;
+  scoped_refptr<RuleBasedHostMapper> mapper_;
+  scoped_refptr<HostResolver> host_resolver_;
+  scoped_ptr<MockSocket> mock_socket_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SOCKS5ClientSocketTest);
+};
+
+SOCKS5ClientSocketTest::SOCKS5ClientSocketTest()
+  : kNwPort(htons(80)), host_resolver_(new HostResolver(0, 0)) {
+}
+
+// Set up platform before every test case
+void SOCKS5ClientSocketTest::SetUp() {
+  PlatformTest::SetUp();
+
+  // Resolve the "localhost" AddressList used by the TCP connection to connect.
+  scoped_refptr<HostResolver> resolver = new HostResolver();
+  HostResolver::RequestInfo info("www.socks-proxy.com", 1080);
+  int rv = resolver->Resolve(info, &address_list_, NULL, NULL);
+  ASSERT_EQ(OK, rv);
+
+  // Create a new host mapping for the duration of this test case only.
+  mapper_ = new RuleBasedHostMapper();
+  host_mapper_.Init(mapper_);
+}
+
+SOCKS5ClientSocket* SOCKS5ClientSocketTest::BuildMockSocket(
+    MockRead reads[],
+    MockWrite writes[],
+    const std::string& hostname,
+    int port) {
+
+  TestCompletionCallback callback;
+  mock_socket_.reset(new StaticMockSocket(reads, writes));
+  tcp_sock_ = new MockTCPClientSocket(address_list_, mock_socket_.get());
+
+  int rv = tcp_sock_->Connect(&callback);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  rv = callback.WaitForResult();
+  EXPECT_EQ(OK, rv);
+  EXPECT_TRUE(tcp_sock_->IsConnected());
+
+  return new SOCKS5ClientSocket(tcp_sock_,
+      HostResolver::RequestInfo(hostname, port),
+      host_resolver_);
+}
+
+const char kSOCKS5GreetRequest[] = { 0x05, 0x01, 0x00 };
+const char kSOCKS5GreetResponse[] = { 0x05, 0x00 };
+
+const char kSOCKS5OkRequest[] =
+    { 0x05, 0x01, 0x00, 0x01, 127, 0, 0, 1, 0x00, 0x50 };
+const char kSOCKS5OkResponse[] =
+    { 0x05, 0x00, 0x00, 0x01, 127, 0, 0, 1, 0x00, 0x50 };
+
+// Tests a complete SOCKS5 handshake and the disconnection.
+TEST_F(SOCKS5ClientSocketTest, CompleteHandshake) {
+  const std::string payload_write = "random data";
+  const std::string payload_read = "moar random data";
+
+  MockWrite data_writes[] = {
+      MockWrite(true, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+      MockWrite(true, kSOCKS5OkRequest, arraysize(kSOCKS5OkRequest)),
+      MockWrite(true, payload_write.data(), payload_write.size()) };
+  MockRead data_reads[] = {
+      MockRead(true, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+      MockRead(true, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)),
+      MockRead(true, payload_read.data(), payload_read.size()) };
+
+  user_sock_.reset(BuildMockSocket(data_reads, data_writes, "localhost", 80));
+
+  // At this state the TCP connection is completed but not the SOCKS handshake.
+  EXPECT_TRUE(tcp_sock_->IsConnected());
+  EXPECT_FALSE(user_sock_->IsConnected());
+
+  int rv = user_sock_->Connect(&callback_);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  EXPECT_FALSE(user_sock_->IsConnected());
+  rv = callback_.WaitForResult();
+
+  EXPECT_EQ(OK, rv);
+  EXPECT_TRUE(user_sock_->IsConnected());
+  EXPECT_EQ(SOCKS5ClientSocket::kEndPointResolvedIPv4,
+            user_sock_->address_type_);
+
+  scoped_refptr<IOBuffer> buffer = new IOBuffer(payload_write.size());
+  memcpy(buffer->data(), payload_write.data(), payload_write.size());
+  rv = user_sock_->Write(buffer, payload_write.size(), &callback_);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  rv = callback_.WaitForResult();
+  EXPECT_EQ(static_cast<int>(payload_write.size()), rv);
+
+  buffer = new IOBuffer(payload_read.size());
+  rv = user_sock_->Read(buffer, payload_read.size(), &callback_);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  rv = callback_.WaitForResult();
+  EXPECT_EQ(static_cast<int>(payload_read.size()), rv);
+  EXPECT_EQ(payload_read, std::string(buffer->data(), payload_read.size()));
+
+  user_sock_->Disconnect();
+  EXPECT_FALSE(tcp_sock_->IsConnected());
+  EXPECT_FALSE(user_sock_->IsConnected());
+}
+
+// Tries to connect to a DNS which fails domain lookup.
+TEST_F(SOCKS5ClientSocketTest, FailedDNS) {
+  const std::string hostname = "unresolved.ipv4.address";
+  const char kSOCKS5DomainRequest[] = { 0x05, 0x01, 0x00, 0x03 };
+
+  mapper_->AddSimulatedFailure(hostname.c_str());
+
+  std::string request(kSOCKS5DomainRequest,
+                      arraysize(kSOCKS5DomainRequest));
+  request.push_back(hostname.size());
+  request.append(hostname);
+  request.append(reinterpret_cast<const char*>(&kNwPort), sizeof(kNwPort));
+
+  MockWrite data_writes[] = {
+      MockWrite(false, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+      MockWrite(false, request.data(), request.size()) };
+  MockRead data_reads[] = {
+      MockRead(false, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+      MockRead(false, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)) };
+
+  user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+
+  int rv = user_sock_->Connect(&callback_);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  rv = callback_.WaitForResult();
+  EXPECT_EQ(OK, rv);
+  EXPECT_TRUE(user_sock_->IsConnected());
+  EXPECT_EQ(SOCKS5ClientSocket::kEndPointFailedDomain,
+            user_sock_->address_type_);
+}
+
+// Tries to connect to a domain that resolves to IPv6.
+TEST_F(SOCKS5ClientSocketTest, IPv6Domain) {
+  const std::string hostname = "an.ipv6.address";
+  const char kSOCKS5IPv6Request[] = { 0x05, 0x01, 0x00, 0x04 };
+  const uint8 ipv6_addr[] = { 0x20, 0x01, 0x0d, 0xb8, 0x87, 0x14, 0x3a, 0x90,
+                              0x00, 0x00, 0x00, 0x00, 0x00, 0x000, 0x00, 0x12 };
+
+  mapper_->AddRule(hostname.c_str(), "2001:db8:8714:3a90::12");
+
+  AddressList address_list;
+  scoped_refptr<HostResolver> resolver = new HostResolver();
+  HostResolver::RequestInfo info(hostname, 80);
+  int rv = resolver->Resolve(info, &address_list, NULL, NULL);
+  if (rv != OK || !address_list.head()) {
+    // This machine does not support IPv6. We skip this test altogether.
+    // TODO(arindam): create a MockIPv6HostResolver to manually
+    // populate the |address_list| in case of a machine with no IPv6 suppport.
+    return;
+  }
+
+  std::string request(kSOCKS5IPv6Request,
+                      arraysize(kSOCKS5IPv6Request));
+  request.append(reinterpret_cast<const char*>(&ipv6_addr), sizeof(ipv6_addr));
+  request.append(reinterpret_cast<const char*>(&kNwPort), sizeof(kNwPort));
+
+  MockWrite data_writes[] = {
+      MockWrite(false, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+      MockWrite(false, request.data(), request.size()) };
+  MockRead data_reads[] = {
+      MockRead(false, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+      MockRead(false, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)) };
+
+  user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+
+  rv = user_sock_->Connect(&callback_);
+  EXPECT_EQ(ERR_IO_PENDING, rv);
+  rv = callback_.WaitForResult();
+  EXPECT_EQ(OK, rv);
+  EXPECT_TRUE(user_sock_->IsConnected());
+  EXPECT_EQ(SOCKS5ClientSocket::kEndPointResolvedIPv6,
+            user_sock_->address_type_);
+}
+
+TEST_F(SOCKS5ClientSocketTest, PartialReadWrites) {
+  const std::string hostname = "www.google.com";
+
+  // Test for partial greet request write
+  {
+    const char partial1[] = { 0x05, 0x01 };
+    const char partial2[] = { 0x00 };
+    MockWrite data_writes[] = {
+        MockWrite(true, arraysize(partial1)),
+        MockWrite(true, partial2, arraysize(partial2)),
+        MockWrite(true, kSOCKS5OkRequest, arraysize(kSOCKS5OkRequest)) };
+    MockRead data_reads[] = {
+        MockRead(true, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+        MockRead(true, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)) };
+    user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+    int rv = user_sock_->Connect(&callback_);
+    EXPECT_EQ(ERR_IO_PENDING, rv);
+    rv = callback_.WaitForResult();
+    EXPECT_EQ(OK, rv);
+    EXPECT_TRUE(user_sock_->IsConnected());
+  }
+
+  // Test for partial greet response read
+  {
+    const char partial1[] = { 0x05 };
+    const char partial2[] = { 0x00 };
+    MockWrite data_writes[] = {
+        MockWrite(true, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+        MockWrite(true, kSOCKS5OkRequest, arraysize(kSOCKS5OkRequest)) };
+    MockRead data_reads[] = {
+        MockRead(true, partial1, arraysize(partial1)),
+        MockRead(true, partial2, arraysize(partial2)),
+        MockRead(true, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)) };
+    user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+    int rv = user_sock_->Connect(&callback_);
+    EXPECT_EQ(ERR_IO_PENDING, rv);
+    rv = callback_.WaitForResult();
+    EXPECT_EQ(OK, rv);
+    EXPECT_TRUE(user_sock_->IsConnected());
+  }
+
+  // Test for partial handshake request write
+  {
+    const char partial1[] = { 0x05, 0x01, 0x00 };
+    const char partial2[] = { 0x01, 127, 0, 0, 1, 0x00, 0x50 };
+    MockWrite data_writes[] = {
+        MockWrite(true, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+        MockWrite(true, arraysize(partial1)),
+        MockWrite(true, partial2, arraysize(partial2)) };
+    MockRead data_reads[] = {
+        MockRead(true, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+        MockRead(true, kSOCKS5OkResponse, arraysize(kSOCKS5OkResponse)) };
+    user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+    int rv = user_sock_->Connect(&callback_);
+    EXPECT_EQ(ERR_IO_PENDING, rv);
+    rv = callback_.WaitForResult();
+    EXPECT_EQ(OK, rv);
+    EXPECT_TRUE(user_sock_->IsConnected());
+  }
+
+  // Test for partial handshake response read
+  {
+    const char partial1[] = { 0x05, 0x00, 0x00, 0x01, 127, 0 };
+    const char partial2[] = { 0, 1, 0x00, 0x50 };
+    MockWrite data_writes[] = {
+        MockWrite(true, kSOCKS5GreetRequest, arraysize(kSOCKS5GreetRequest)),
+        MockWrite(true, kSOCKS5OkRequest, arraysize(kSOCKS5OkRequest)) };
+    MockRead data_reads[] = {
+        MockRead(true, kSOCKS5GreetResponse, arraysize(kSOCKS5GreetResponse)),
+        MockRead(true, partial1, arraysize(partial1)),
+        MockRead(true, partial2, arraysize(partial2)) };
+    user_sock_.reset(BuildMockSocket(data_reads, data_writes, hostname, 80));
+    int rv = user_sock_->Connect(&callback_);
+    EXPECT_EQ(ERR_IO_PENDING, rv);
+    rv = callback_.WaitForResult();
+    EXPECT_EQ(OK, rv);
+    EXPECT_TRUE(user_sock_->IsConnected());
+  }
+}
+
+}  // namespace net
+