Merge "fastboot: add TCP protocol."

fastboot/Android.mk

@@ -31,6 +31,7 @@ LOCAL_SRC_FILES := \
     fs.cpp\
     protocol.cpp \
     socket.cpp \
+    tcp.cpp \
     util.cpp \
 
 LOCAL_MODULE := fastboot
@@ -111,6 +112,8 @@ LOCAL_SRC_FILES := \
     socket.cpp \
     socket_mock.cpp \
     socket_test.cpp \
+    tcp.cpp \
+    tcp_test.cpp \
 
 LOCAL_STATIC_LIBRARIES := libbase libcutils
 

fastboot/fastboot.cpp

@@ -42,22 +42,22 @@
 #include <sys/time.h>
 #include <sys/types.h>
 #include <unistd.h>
+
 #include <functional>
 #include <utility>
 #include <vector>
 
 #include <android-base/parseint.h>
+#include <android-base/parsenetaddress.h>
 #include <android-base/strings.h>
 #include <sparse/sparse.h>
 #include <ziparchive/zip_archive.h>
 
-#include <android-base/strings.h>
-#include <android-base/parseint.h>
-
 #include "bootimg_utils.h"
 #include "diagnose_usb.h"
 #include "fastboot.h"
 #include "fs.h"
+#include "tcp.h"
 #include "transport.h"
 #include "usb.h"
 
@@ -69,9 +69,9 @@
 
 char cur_product[FB_RESPONSE_SZ + 1];
 
-static const char *serial = 0;
+static const char* serial = nullptr;
-static const char *product = 0;
+static const char* product = nullptr;
-static const char *cmdline = 0;
+static const char* cmdline = nullptr;
 static unsigned short vendor_id = 0;
 static int long_listing = 0;
 static int64_t sparse_limit = -1;
@@ -227,17 +227,51 @@ static int list_devices_callback(usb_ifc_info* info) {
     return -1;
 }
 
+// Opens a new Transport connected to a device. If |serial| is non-null it will be used to identify
+// a specific device, otherwise the first USB device found will be used.
+//
+// If |serial| is non-null but invalid, this prints an error message to stderr and returns nullptr.
+// Otherwise it blocks until the target is available.
+//
+// The returned Transport is a singleton, so multiple calls to this function will return the same
+// object, and the caller should not attempt to delete the returned Transport.
 static Transport* open_device() {
     static Transport* transport = nullptr;
-    int announce = 1;
+    bool announce = true;
 
-    if (transport) return transport;
+    if (transport != nullptr) {
+        return transport;
+    }
+
+    std::string host;
+    int port = tcp::kDefaultPort;
+    if (serial != nullptr && android::base::StartsWith(serial, "tcp:")) {
+        std::string error;
+        const char* address = serial + strlen("tcp:");
+
+        if (!android::base::ParseNetAddress(address, &host, &port, nullptr, &error)) {
+            fprintf(stderr, "error: Invalid network address '%s': %s\n", address, error.c_str());
+            return nullptr;
+        }
+    }
+
+    while (true) {
+        if (!host.empty()) {
+            std::string error;
+            transport = tcp::Connect(host, port, &error).release();
+            if (transport == nullptr && announce) {
+                fprintf(stderr, "error: %s\n", error.c_str());
+            }
+        } else {
+            transport = usb_open(match_fastboot);
+        }
+
+        if (transport != nullptr) {
+            return transport;
+        }
 
-    for (;;) {
-        transport = usb_open(match_fastboot);
-        if (transport) return transport;
         if (announce) {
-            announce = 0;
+            announce = false;
             fprintf(stderr, "< waiting for %s >\n", serial ? serial : "any device");
         }
         usleep(1000);
@@ -299,8 +333,10 @@ static void usage() {
             "                                           if supported by partition type).\n"
             "  -u                                       Do not erase partition before\n"
             "                                           formatting.\n"
-            "  -s <specific device>                     Specify device serial number\n"
+            "  -s <specific device>                     Specify a device. For USB, provide either\n"
-            "                                           or path to device port.\n"
+            "                                           a serial number or path to device port.\n"
+            "                                           For TCP, provide an address in the form\n"
+            "                                           tcp:<hostname>[:port].\n"
             "  -p <product>                             Specify product name.\n"
             "  -c <cmdline>                             Override kernel commandline.\n"
             "  -i <vendor id>                           Specify a custom USB vendor id.\n"
@@ -1263,6 +1299,10 @@ int main(int argc, char **argv)
     }
 
     Transport* transport = open_device();
+    if (transport == nullptr) {
+        return 1;
+    }
+
     if (slot_override != "")
         slot_override = verify_slot(transport, slot_override.c_str());
     if (next_active != "")

fastboot/fastboot_protocol.txt

@@ -3,19 +3,25 @@ FastBoot  Version  0.4
 ----------------------
 
 The fastboot protocol is a mechanism for communicating with bootloaders
-over USB.  It is designed to be very straightforward to implement, to
+over USB or ethernet.  It is designed to be very straightforward to implement,
-allow it to be used across a wide range of devices and from hosts running
+to allow it to be used across a wide range of devices and from hosts running
 Linux, Windows, or OSX.
 
 
 Basic Requirements
 ------------------
 
-* Two bulk endpoints (in, out) are required
+* USB
-* Max packet size must be 64 bytes for full-speed, 512 bytes for
+  * Two bulk endpoints (in, out) are required
-  high-speed and 1024 bytes for Super Speed USB.
+  * Max packet size must be 64 bytes for full-speed, 512 bytes for
-* The protocol is entirely host-driven and synchronous (unlike the
+    high-speed and 1024 bytes for Super Speed USB.
-  multi-channel, bi-directional, asynchronous ADB protocol)
+  * The protocol is entirely host-driven and synchronous (unlike the
+    multi-channel, bi-directional, asynchronous ADB protocol)
+
+* TCP
+  * Device must be reachable via IP.
+  * Device will act as the TCP server, fastboot will be the client.
+  * Fastboot data is wrapped in a simple protocol; see below for details.
 
 
 Transport and Framing
@@ -171,3 +177,44 @@ specification.  OEM-specific names should not start with lowercase
 characters.
 
 
+TCP Protocol v1
+---------------
+
+The TCP protocol is designed to be a simple way to use the fastboot protocol
+over ethernet if USB is not available.
+
+The device will open a TCP server on port 5554 and wait for a fastboot client
+to connect.
+
+-- Handshake --
+Upon connecting, both sides will send a 4-byte handshake message to ensure they
+are speaking the same protocol. This consists of the ASCII characters "FB"
+followed by a 2-digit base-10 ASCII version number. For example, the version 1
+handshake message will be [FB01].
+
+If either side detects a malformed handshake, it should disconnect.
+
+The protocol version to use must be the minimum of the versions sent by each
+side; if either side cannot speak this protocol version, it should disconnect.
+
+-- Fastboot Data --
+Once the handshake is complete, fastboot data will be sent as follows:
+
+  [data_size][data]
+
+Where data_size is an unsigned 8-byte big-endian binary value, and data is the
+fastboot packet. The 8-byte length is intended to provide future-proofing even
+though currently fastboot packets have a 4-byte maximum length.
+
+-- Example --
+In this example the fastboot host queries the device for two variables,
+"version" and "none".
+
+Host    <connect to the device on port 5555>
+Host    FB01
+Device  FB01
+Host    [0x00][0x00][0x00][0x00][0x00][0x00][0x00][0x0E]getvar:version
+Device  [0x00][0x00][0x00][0x00][0x00][0x00][0x00][0x07]OKAY0.4
+Host    [0x00][0x00][0x00][0x00][0x00][0x00][0x00][0x0B]getvar:none
+Device  [0x00][0x00][0x00][0x00][0x00][0x00][0x00][0x04]OKAY
+Host    <disconnect>

fastboot/tcp.cpp

@@ -0,0 +1,196 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "tcp.h"
+
+#include <android-base/stringprintf.h>
+
+namespace tcp {
+
+static constexpr int kProtocolVersion = 1;
+static constexpr size_t kHandshakeLength = 4;
+static constexpr int kHandshakeTimeoutMs = 2000;
+
+// Extract the big-endian 8-byte message length into a 64-bit number.
+static uint64_t ExtractMessageLength(const void* buffer) {
+    uint64_t ret = 0;
+    for (int i = 0; i < 8; ++i) {
+        ret |= uint64_t{reinterpret_cast<const uint8_t*>(buffer)[i]} << (56 - i * 8);
+    }
+    return ret;
+}
+
+// Encode the 64-bit number into a big-endian 8-byte message length.
+static void EncodeMessageLength(uint64_t length, void* buffer) {
+    for (int i = 0; i < 8; ++i) {
+        reinterpret_cast<uint8_t*>(buffer)[i] = length >> (56 - i * 8);
+    }
+}
+
+class TcpTransport : public Transport {
+  public:
+    // Factory function so we can return nullptr if initialization fails.
+    static std::unique_ptr<TcpTransport> NewTransport(std::unique_ptr<Socket> socket,
+                                                      std::string* error);
+
+    ~TcpTransport() override = default;
+
+    ssize_t Read(void* data, size_t length) override;
+    ssize_t Write(const void* data, size_t length) override;
+    int Close() override;
+
+  private:
+    TcpTransport(std::unique_ptr<Socket> sock) : socket_(std::move(sock)) {}
+
+    // Connects to the device and performs the initial handshake. Returns false and fills |error|
+    // on failure.
+    bool InitializeProtocol(std::string* error);
+
+    std::unique_ptr<Socket> socket_;
+    uint64_t message_bytes_left_ = 0;
+
+    DISALLOW_COPY_AND_ASSIGN(TcpTransport);
+};
+
+std::unique_ptr<TcpTransport> TcpTransport::NewTransport(std::unique_ptr<Socket> socket,
+                                                         std::string* error) {
+    std::unique_ptr<TcpTransport> transport(new TcpTransport(std::move(socket)));
+
+    if (!transport->InitializeProtocol(error)) {
+        return nullptr;
+    }
+
+    return transport;
+}
+
+// These error strings are checked in tcp_test.cpp and should be kept in sync.
+bool TcpTransport::InitializeProtocol(std::string* error) {
+    std::string handshake_message(android::base::StringPrintf("FB%02d", kProtocolVersion));
+
+    if (!socket_->Send(handshake_message.c_str(), kHandshakeLength)) {
+        *error = android::base::StringPrintf("Failed to send initialization message (%s)",
+                                             Socket::GetErrorMessage().c_str());
+        return false;
+    }
+
+    char buffer[kHandshakeLength];
+    if (socket_->ReceiveAll(buffer, kHandshakeLength, kHandshakeTimeoutMs) != kHandshakeLength) {
+        *error = android::base::StringPrintf(
+                "No initialization message received (%s). Target may not support TCP fastboot",
+                Socket::GetErrorMessage().c_str());
+        return false;
+    }
+
+    if (memcmp(buffer, "FB", 2) != 0) {
+        *error = "Unrecognized initialization message. Target may not support TCP fastboot";
+        return false;
+    }
+
+    if (memcmp(buffer + 2, "01", 2) != 0) {
+        *error = android::base::StringPrintf("Unknown TCP protocol version %s (host version %02d)",
+                                             std::string(buffer + 2, 2).c_str(), kProtocolVersion);
+        return false;
+    }
+
+    error->clear();
+    return true;
+}
+
+ssize_t TcpTransport::Read(void* data, size_t length) {
+    if (socket_ == nullptr) {
+        return -1;
+    }
+
+    // Unless we're mid-message, read the next 8-byte message length.
+    if (message_bytes_left_ == 0) {
+        char buffer[8];
+        if (socket_->ReceiveAll(buffer, 8, 0) != 8) {
+            Close();
+            return -1;
+        }
+        message_bytes_left_ = ExtractMessageLength(buffer);
+    }
+
+    // Now read the message (up to |length| bytes).
+    if (length > message_bytes_left_) {
+        length = message_bytes_left_;
+    }
+    ssize_t bytes_read = socket_->ReceiveAll(data, length, 0);
+    if (bytes_read == -1) {
+        Close();
+    } else {
+        message_bytes_left_ -= bytes_read;
+    }
+    return bytes_read;
+}
+
+ssize_t TcpTransport::Write(const void* data, size_t length) {
+    if (socket_ == nullptr) {
+        return -1;
+    }
+
+    // Use multi-buffer writes for better performance.
+    char header[8];
+    EncodeMessageLength(length, header);
+    if (!socket_->Send(std::vector<cutils_socket_buffer_t>{{header, 8}, {data, length}})) {
+        Close();
+        return -1;
+    }
+
+    return length;
+}
+
+int TcpTransport::Close() {
+    if (socket_ == nullptr) {
+        return 0;
+    }
+
+    int result = socket_->Close();
+    socket_.reset();
+    return result;
+}
+
+std::unique_ptr<Transport> Connect(const std::string& hostname, int port, std::string* error) {
+    return internal::Connect(Socket::NewClient(Socket::Protocol::kTcp, hostname, port, error),
+                             error);
+}
+
+namespace internal {
+
+std::unique_ptr<Transport> Connect(std::unique_ptr<Socket> sock, std::string* error) {
+    if (sock == nullptr) {
+        // If Socket creation failed |error| is already set.
+        return nullptr;
+    }
+
+    return TcpTransport::NewTransport(std::move(sock), error);
+}
+
+}  // namespace internal
+
+}  // namespace tcp

fastboot/tcp.h

@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef TCP_H_
+#define TCP_H_
+
+#include <memory>
+#include <string>
+
+#include <android-base/macros.h>
+
+#include "socket.h"
+#include "transport.h"
+
+namespace tcp {
+
+constexpr int kDefaultPort = 5554;
+
+// Returns a newly allocated Transport object connected to |hostname|:|port|. On failure, |error| is
+// filled and nullptr is returned.
+std::unique_ptr<Transport> Connect(const std::string& hostname, int port, std::string* error);
+
+// Internal namespace for test use only.
+namespace internal {
+
+// Creates a TCP Transport object but using a given Socket instead of connecting to a hostname.
+// Used for unit tests to create a Transport object that uses a SocketMock.
+std::unique_ptr<Transport> Connect(std::unique_ptr<Socket> sock, std::string* error);
+
+}  // namespace internal
+
+}  // namespace tcp
+
+#endif  // TCP_H_

fastboot/tcp_test.cpp

@@ -0,0 +1,217 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "tcp.h"
+
+#include <gtest/gtest.h>
+
+#include "socket_mock.h"
+
+TEST(TcpConnectTest, TestSuccess) {
+    std::unique_ptr<SocketMock> mock(new SocketMock);
+    mock->ExpectSend("FB01");
+    mock->AddReceive("FB01");
+
+    std::string error;
+    EXPECT_NE(nullptr, tcp::internal::Connect(std::move(mock), &error));
+    EXPECT_EQ("", error);
+}
+
+TEST(TcpConnectTest, TestSendFailure) {
+    std::unique_ptr<SocketMock> mock(new SocketMock);
+    mock->ExpectSendFailure("FB01");
+
+    std::string error;
+    EXPECT_EQ(nullptr, tcp::internal::Connect(std::move(mock), &error));
+    EXPECT_NE(std::string::npos, error.find("Failed to send initialization message"));
+}
+
+TEST(TcpConnectTest, TestNoResponseFailure) {
+    std::unique_ptr<SocketMock> mock(new SocketMock);
+    mock->ExpectSend("FB01");
+    mock->AddReceiveFailure();
+
+    std::string error;
+    EXPECT_EQ(nullptr, tcp::internal::Connect(std::move(mock), &error));
+    EXPECT_NE(std::string::npos, error.find("No initialization message received"));
+}
+
+TEST(TcpConnectTest, TestBadResponseFailure) {
+    std::unique_ptr<SocketMock> mock(new SocketMock);
+    mock->ExpectSend("FB01");
+    mock->AddReceive("XX01");
+
+    std::string error;
+    EXPECT_EQ(nullptr, tcp::internal::Connect(std::move(mock), &error));
+    EXPECT_NE(std::string::npos, error.find("Unrecognized initialization message"));
+}
+
+TEST(TcpConnectTest, TestUnknownVersionFailure) {
+    std::unique_ptr<SocketMock> mock(new SocketMock);
+    mock->ExpectSend("FB01");
+    mock->AddReceive("FB02");
+
+    std::string error;
+    EXPECT_EQ(nullptr, tcp::internal::Connect(std::move(mock), &error));
+    EXPECT_EQ("Unknown TCP protocol version 02 (host version 01)", error);
+}
+
+// Fixture to configure a SocketMock for a successful TCP connection.
+class TcpTest : public ::testing::Test {
+  protected:
+    void SetUp() override {
+        mock_ = new SocketMock;
+        mock_->ExpectSend("FB01");
+        mock_->AddReceive("FB01");
+
+        std::string error;
+        transport_ = tcp::internal::Connect(std::unique_ptr<Socket>(mock_), &error);
+        ASSERT_NE(nullptr, transport_);
+        ASSERT_EQ("", error);
+    };
+
+    // Writes |message| to |transport_|, returns true on success.
+    bool Write(const std::string& message) {
+        return transport_->Write(message.data(), message.length()) ==
+               static_cast<ssize_t>(message.length());
+    }
+
+    // Reads from |transport_|, returns true if it matches |message|.
+    bool Read(const std::string& message) {
+        std::string buffer(message.length(), '\0');
+        return transport_->Read(&buffer[0], buffer.length()) ==
+                       static_cast<ssize_t>(message.length()) &&
+               buffer == message;
+    }
+
+    // Use a raw SocketMock* here because we pass ownership to the Transport object, but we still
+    // need access to configure mock expectations.
+    SocketMock* mock_ = nullptr;
+    std::unique_ptr<Transport> transport_;
+};
+
+TEST_F(TcpTest, TestWriteSuccess) {
+    mock_->ExpectSend(std::string{0, 0, 0, 0, 0, 0, 0, 3} + "foo");
+
+    EXPECT_TRUE(Write("foo"));
+}
+
+TEST_F(TcpTest, TestReadSuccess) {
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 3});
+    mock_->AddReceive("foo");
+
+    EXPECT_TRUE(Read("foo"));
+}
+
+// Tests that fragmented TCP reads are handled properly.
+TEST_F(TcpTest, TestReadFragmentSuccess) {
+    mock_->AddReceive(std::string{0, 0, 0, 0});
+    mock_->AddReceive(std::string{0, 0, 0, 3});
+    mock_->AddReceive("f");
+    mock_->AddReceive("o");
+    mock_->AddReceive("o");
+
+    EXPECT_TRUE(Read("foo"));
+}
+
+TEST_F(TcpTest, TestLargeWriteSuccess) {
+    // 0x100000 = 1MiB.
+    std::string data(0x100000, '\0');
+    for (size_t i = 0; i < data.length(); ++i) {
+        data[i] = i;
+    }
+    mock_->ExpectSend(std::string{0, 0, 0, 0, 0, 0x10, 0, 0} + data);
+
+    EXPECT_TRUE(Write(data));
+}
+
+TEST_F(TcpTest, TestLargeReadSuccess) {
+    // 0x100000 = 1MiB.
+    std::string data(0x100000, '\0');
+    for (size_t i = 0; i < data.length(); ++i) {
+        data[i] = i;
+    }
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0x10, 0, 0});
+    mock_->AddReceive(data);
+
+    EXPECT_TRUE(Read(data));
+}
+
+// Tests a few sample fastboot protocol commands.
+TEST_F(TcpTest, TestFastbootProtocolSuccess) {
+    mock_->ExpectSend(std::string{0, 0, 0, 0, 0, 0, 0, 14} + "getvar:version");
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 7});
+    mock_->AddReceive("OKAY0.4");
+
+    mock_->ExpectSend(std::string{0, 0, 0, 0, 0, 0, 0, 10} + "getvar:all");
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 16});
+    mock_->AddReceive("INFOversion: 0.4");
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 12});
+    mock_->AddReceive("INFOfoo: bar");
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 4});
+    mock_->AddReceive("OKAY");
+
+    EXPECT_TRUE(Write("getvar:version"));
+    EXPECT_TRUE(Read("OKAY0.4"));
+
+    EXPECT_TRUE(Write("getvar:all"));
+    EXPECT_TRUE(Read("INFOversion: 0.4"));
+    EXPECT_TRUE(Read("INFOfoo: bar"));
+    EXPECT_TRUE(Read("OKAY"));
+}
+
+TEST_F(TcpTest, TestReadLengthFailure) {
+    mock_->AddReceiveFailure();
+
+    char buffer[16];
+    EXPECT_EQ(-1, transport_->Read(buffer, sizeof(buffer)));
+}
+
+TEST_F(TcpTest, TestReadDataFailure) {
+    mock_->AddReceive(std::string{0, 0, 0, 0, 0, 0, 0, 3});
+    mock_->AddReceiveFailure();
+
+    char buffer[16];
+    EXPECT_EQ(-1, transport_->Read(buffer, sizeof(buffer)));
+}
+
+TEST_F(TcpTest, TestWriteFailure) {
+    mock_->ExpectSendFailure(std::string{0, 0, 0, 0, 0, 0, 0, 3} + "foo");
+
+    EXPECT_EQ(-1, transport_->Write("foo", 3));
+}
+
+TEST_F(TcpTest, TestTransportClose) {
+    EXPECT_EQ(0, transport_->Close());
+
+    // After closing, Transport Read()/Write() should return -1 without actually attempting any
+    // network operations.
+    char buffer[16];
+    EXPECT_EQ(-1, transport_->Read(buffer, sizeof(buffer)));
+    EXPECT_EQ(-1, transport_->Write("foo", 3));
+}