Merge "fastboot: implement UDP networking interface."

fastboot/Android.mk

@@ -33,15 +33,15 @@ LOCAL_CFLAGS += -Wall -Wextra -Werror -Wunreachable-code
 
 LOCAL_CFLAGS += -DFASTBOOT_REVISION='"$(fastboot_version)"'
 
-LOCAL_SRC_FILES_linux := usb_linux.cpp util_linux.cpp
+LOCAL_SRC_FILES_linux := socket_unix.cpp usb_linux.cpp util_linux.cpp
-LOCAL_STATIC_LIBRARIES_linux := libselinux
+LOCAL_STATIC_LIBRARIES_linux := libcutils libselinux
 
-LOCAL_SRC_FILES_darwin := usb_osx.cpp util_osx.cpp
+LOCAL_SRC_FILES_darwin := socket_unix.cpp usb_osx.cpp util_osx.cpp
-LOCAL_STATIC_LIBRARIES_darwin := libselinux
+LOCAL_STATIC_LIBRARIES_darwin := libcutils libselinux
 LOCAL_LDLIBS_darwin := -lpthread -framework CoreFoundation -framework IOKit -framework Carbon
 LOCAL_CFLAGS_darwin := -Wno-unused-parameter
 
-LOCAL_SRC_FILES_windows := usb_windows.cpp util_windows.cpp
+LOCAL_SRC_FILES_windows := socket_windows.cpp usb_windows.cpp util_windows.cpp
 LOCAL_STATIC_LIBRARIES_windows := AdbWinApi
 LOCAL_REQUIRED_MODULES_windows := AdbWinApi
 LOCAL_LDLIBS_windows := -lws2_32
@@ -89,3 +89,28 @@ LOCAL_CFLAGS := -Werror
 LOCAL_STATIC_LIBRARIES := libbase
 include $(BUILD_HOST_EXECUTABLE)
 endif
+
+# fastboot_test
+# =========================================================
+include $(CLEAR_VARS)
+
+LOCAL_MODULE := fastboot_test
+LOCAL_MODULE_HOST_OS := darwin linux windows
+
+LOCAL_SRC_FILES := socket_test.cpp
+LOCAL_STATIC_LIBRARIES := libbase
+
+LOCAL_CFLAGS += -Wall -Wextra -Werror -Wunreachable-code
+
+LOCAL_SRC_FILES_linux := socket_unix.cpp
+LOCAL_STATIC_LIBRARIES_linux := libcutils
+
+LOCAL_SRC_FILES_darwin := socket_unix.cpp
+LOCAL_LDLIBS_darwin := -lpthread -framework CoreFoundation -framework IOKit -framework Carbon
+LOCAL_CFLAGS_darwin := -Wno-unused-parameter
+LOCAL_STATIC_LIBRARIES_darwin := libcutils
+
+LOCAL_SRC_FILES_windows := socket_windows.cpp
+LOCAL_LDLIBS_windows := -lws2_32
+
+include $(BUILD_HOST_NATIVE_TEST)

fastboot/socket.h

@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2015 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.
+ */
+
+// This file provides a class interface for cross-platform UDP functionality. The main fastboot
+// engine should not be using this interface directly, but instead should use a higher-level
+// interface that enforces the fastboot UDP protocol.
+
+#ifndef SOCKET_H_
+#define SOCKET_H_
+
+#include "android-base/macros.h"
+
+#include <memory>
+#include <string>
+
+// UdpSocket interface to be implemented for each platform.
+class UdpSocket {
+  public:
+    // Creates a new client connection. Clients are connected to a specific hostname/port and can
+    // only send to that destination.
+    // On failure, |error| is filled (if non-null) and nullptr is returned.
+    static std::unique_ptr<UdpSocket> NewUdpClient(const std::string& hostname, int port,
+                                                   std::string* error);
+
+    // Creates a new server bound to local |port|. This is only meant for testing, during normal
+    // fastboot operation the device acts as the server.
+    // The server saves sender addresses in Receive(), and uses the most recent address during
+    // calls to Send().
+    static std::unique_ptr<UdpSocket> NewUdpServer(int port);
+
+    virtual ~UdpSocket() = default;
+
+    // Sends |length| bytes of |data|. Returns the number of bytes actually sent or -1 on error.
+    virtual ssize_t Send(const void* data, size_t length) = 0;
+
+    // Waits up to |timeout_ms| to receive up to |length| bytes of data. |timout_ms| of 0 will
+    // block forever. Returns the number of bytes received or -1 on error/timeout. On timeout
+    // errno will be set to EAGAIN or EWOULDBLOCK.
+    virtual ssize_t Receive(void* data, size_t length, int timeout_ms) = 0;
+
+    // Closes the socket. Returns 0 on success, -1 on error.
+    virtual int Close() = 0;
+
+  protected:
+    // Protected constructor to force factory function use.
+    UdpSocket() = default;
+
+    DISALLOW_COPY_AND_ASSIGN(UdpSocket);
+};
+
+#endif  // SOCKET_H_

fastboot/socket_test.cpp

@@ -0,0 +1,197 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Tests UDP functionality using loopback connections. Requires that kDefaultPort is available
+// for loopback communication on the host. These tests also assume that no UDP packets are lost,
+// which should be the case for loopback communication, but is not guaranteed.
+
+#include "socket.h"
+
+#include <errno.h>
+#include <time.h>
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <gtest/gtest.h>
+
+enum {
+    // This port must be available for loopback communication.
+    kDefaultPort = 54321,
+
+    // Don't wait forever in a unit test.
+    kDefaultTimeoutMs = 3000,
+};
+
+static const char kReceiveStringError[] = "Error receiving string";
+
+// Test fixture to provide some helper functions. Makes each test a little simpler since we can
+// just check a bool for socket creation and don't have to pass hostname or port information.
+class SocketTest : public ::testing::Test {
+  protected:
+    bool StartServer(int port = kDefaultPort) {
+        server_ = UdpSocket::NewUdpServer(port);
+        return server_ != nullptr;
+    }
+
+    bool StartClient(const std::string hostname = "localhost", int port = kDefaultPort) {
+        client_ = UdpSocket::NewUdpClient(hostname, port, nullptr);
+        return client_ != nullptr;
+    }
+
+    bool StartClient2(const std::string hostname = "localhost", int port = kDefaultPort) {
+        client2_ = UdpSocket::NewUdpClient(hostname, port, nullptr);
+        return client2_ != nullptr;
+    }
+
+    std::unique_ptr<UdpSocket> server_, client_, client2_;
+};
+
+// Sends a string over a UdpSocket. Returns true if the full string (without terminating char)
+// was sent.
+static bool SendString(UdpSocket* udp, const std::string& message) {
+    return udp->Send(message.c_str(), message.length()) == static_cast<ssize_t>(message.length());
+}
+
+// Receives a string from a UdpSocket. Returns the string, or kReceiveStringError on failure.
+static std::string ReceiveString(UdpSocket* udp, size_t receive_size = 128) {
+    std::vector<char> buffer(receive_size);
+
+    ssize_t result = udp->Receive(buffer.data(), buffer.size(), kDefaultTimeoutMs);
+    if (result >= 0) {
+        return std::string(buffer.data(), result);
+    }
+    return kReceiveStringError;
+}
+
+// Calls Receive() on the UdpSocket with the given timeout. Returns true if the call timed out.
+static bool ReceiveTimeout(UdpSocket* udp, int timeout_ms) {
+    char buffer[1];
+
+    errno = 0;
+    return udp->Receive(buffer, 1, timeout_ms) == -1 && (errno == EAGAIN || errno == EWOULDBLOCK);
+}
+
+// Tests sending packets client -> server, then server -> client.
+TEST_F(SocketTest, SendAndReceive) {
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient());
+
+    EXPECT_TRUE(SendString(client_.get(), "foo"));
+    EXPECT_EQ("foo", ReceiveString(server_.get()));
+
+    EXPECT_TRUE(SendString(server_.get(), "bar baz"));
+    EXPECT_EQ("bar baz", ReceiveString(client_.get()));
+}
+
+// Tests sending and receiving large packets.
+TEST_F(SocketTest, LargePackets) {
+    std::string message(512, '\0');
+
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient());
+
+    // Run through the test a few times.
+    for (int i = 0; i < 10; ++i) {
+        // Use a different message each iteration to prevent false positives.
+        for (size_t j = 0; j < message.length(); ++j) {
+            message[j] = static_cast<char>(i + j);
+        }
+
+        EXPECT_TRUE(SendString(client_.get(), message));
+        EXPECT_EQ(message, ReceiveString(server_.get(), message.length()));
+    }
+}
+
+// Tests IPv4 client/server.
+TEST_F(SocketTest, IPv4) {
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient("127.0.0.1"));
+
+    EXPECT_TRUE(SendString(client_.get(), "foo"));
+    EXPECT_EQ("foo", ReceiveString(server_.get()));
+
+    EXPECT_TRUE(SendString(server_.get(), "bar"));
+    EXPECT_EQ("bar", ReceiveString(client_.get()));
+}
+
+// Tests IPv6 client/server.
+TEST_F(SocketTest, IPv6) {
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient("::1"));
+
+    EXPECT_TRUE(SendString(client_.get(), "foo"));
+    EXPECT_EQ("foo", ReceiveString(server_.get()));
+
+    EXPECT_TRUE(SendString(server_.get(), "bar"));
+    EXPECT_EQ("bar", ReceiveString(client_.get()));
+}
+
+// Tests receive timeout. The timing verification logic must be very coarse to make sure different
+// systems running different loads can all pass these tests.
+TEST_F(SocketTest, ReceiveTimeout) {
+    time_t start_time;
+
+    ASSERT_TRUE(StartServer());
+
+    // Make sure a 20ms timeout completes in 1 second or less.
+    start_time = time(nullptr);
+    EXPECT_TRUE(ReceiveTimeout(server_.get(), 20));
+    EXPECT_LE(difftime(time(nullptr), start_time), 1.0);
+
+    // Make sure a 1250ms timeout takes 1 second or more.
+    start_time = time(nullptr);
+    EXPECT_TRUE(ReceiveTimeout(server_.get(), 1250));
+    EXPECT_LE(1.0, difftime(time(nullptr), start_time));
+}
+
+// Tests receive overflow (the UDP packet is larger than the receive buffer).
+TEST_F(SocketTest, ReceiveOverflow) {
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient());
+
+    EXPECT_TRUE(SendString(client_.get(), "1234567890"));
+
+    // This behaves differently on different systems; some give us a truncated UDP packet, others
+    // will error out and not return anything at all.
+    std::string rx_string = ReceiveString(server_.get(), 5);
+
+    // If we didn't get an error then the packet should have been truncated.
+    if (rx_string != kReceiveStringError) {
+        EXPECT_EQ("12345", rx_string);
+    }
+}
+
+// Tests multiple clients sending to the same server.
+TEST_F(SocketTest, MultipleClients) {
+    ASSERT_TRUE(StartServer());
+    ASSERT_TRUE(StartClient());
+    ASSERT_TRUE(StartClient2());
+
+    EXPECT_TRUE(SendString(client_.get(), "client"));
+    EXPECT_TRUE(SendString(client2_.get(), "client2"));
+
+    // Receive the packets and send a response for each (note that packets may be received
+    // out-of-order).
+    for (int i = 0; i < 2; ++i) {
+        std::string received = ReceiveString(server_.get());
+        EXPECT_TRUE(SendString(server_.get(), received + " response"));
+    }
+
+    EXPECT_EQ("client response", ReceiveString(client_.get()));
+    EXPECT_EQ("client2 response", ReceiveString(client2_.get()));
+}

fastboot/socket_unix.cpp

@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2015 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 "socket.h"
+
+#include <errno.h>
+#include <netdb.h>
+
+#include <android-base/stringprintf.h>
+#include <cutils/sockets.h>
+
+class UnixUdpSocket : public UdpSocket {
+  public:
+    enum class Type { kClient, kServer };
+
+    UnixUdpSocket(int fd, Type type);
+    ~UnixUdpSocket() override;
+
+    ssize_t Send(const void* data, size_t length) override;
+    ssize_t Receive(void* data, size_t length, int timeout_ms) override;
+    int Close() override;
+
+  private:
+    int fd_;
+    int receive_timeout_ms_ = 0;
+    std::unique_ptr<sockaddr_storage> addr_;
+    socklen_t addr_size_ = 0;
+
+    DISALLOW_COPY_AND_ASSIGN(UnixUdpSocket);
+};
+
+UnixUdpSocket::UnixUdpSocket(int fd, Type type) : fd_(fd) {
+    // Only servers need to remember addresses; clients are connected to a server in NewUdpClient()
+    // so will send to that server without needing to specify the address again.
+    if (type == Type::kServer) {
+        addr_.reset(new sockaddr_storage);
+        addr_size_ = sizeof(*addr_);
+        memset(addr_.get(), 0, addr_size_);
+    }
+}
+
+UnixUdpSocket::~UnixUdpSocket() {
+    Close();
+}
+
+ssize_t UnixUdpSocket::Send(const void* data, size_t length) {
+    return TEMP_FAILURE_RETRY(
+            sendto(fd_, data, length, 0, reinterpret_cast<sockaddr*>(addr_.get()), addr_size_));
+}
+
+ssize_t UnixUdpSocket::Receive(void* data, size_t length, int timeout_ms) {
+    // Only set socket timeout if it's changed.
+    if (receive_timeout_ms_ != timeout_ms) {
+        timeval tv;
+        tv.tv_sec = timeout_ms / 1000;
+        tv.tv_usec = (timeout_ms % 1000) * 1000;
+        if (setsockopt(fd_, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) < 0) {
+            return -1;
+        }
+        receive_timeout_ms_ = timeout_ms;
+    }
+
+    socklen_t* addr_size_ptr = nullptr;
+    if (addr_ != nullptr) {
+        // Reset addr_size as it may have been modified by previous recvfrom() calls.
+        addr_size_ = sizeof(*addr_);
+        addr_size_ptr = &addr_size_;
+    }
+    return TEMP_FAILURE_RETRY(recvfrom(fd_, data, length, 0,
+                                       reinterpret_cast<sockaddr*>(addr_.get()), addr_size_ptr));
+}
+
+int UnixUdpSocket::Close() {
+    int result = 0;
+    if (fd_ != -1) {
+        result = close(fd_);
+        fd_ = -1;
+    }
+    return result;
+}
+
+std::unique_ptr<UdpSocket> UdpSocket::NewUdpClient(const std::string& host, int port,
+                                                   std::string* error) {
+    int getaddrinfo_error = 0;
+    int fd = socket_network_client_timeout(host.c_str(), port, SOCK_DGRAM, 0, &getaddrinfo_error);
+    if (fd == -1) {
+        if (error) {
+            *error = android::base::StringPrintf(
+                    "Failed to connect to %s:%d: %s", host.c_str(), port,
+                    getaddrinfo_error ? gai_strerror(getaddrinfo_error) : strerror(errno));
+        }
+        return nullptr;
+    }
+
+    return std::unique_ptr<UdpSocket>(new UnixUdpSocket(fd, UnixUdpSocket::Type::kClient));
+}
+
+std::unique_ptr<UdpSocket> UdpSocket::NewUdpServer(int port) {
+    int fd = socket_inaddr_any_server(port, SOCK_DGRAM);
+    if (fd == -1) {
+        // This is just used in testing, no need for an error message.
+        return nullptr;
+    }
+
+    return std::unique_ptr<UdpSocket>(new UnixUdpSocket(fd, UnixUdpSocket::Type::kServer));
+}

fastboot/socket_windows.cpp

@@ -0,0 +1,246 @@
+/*
+ * Copyright (C) 2015 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 "socket.h"
+
+#include <winsock2.h>
+#include <ws2tcpip.h>
+
+#include <memory>
+
+#include <android-base/stringprintf.h>
+
+// Windows UDP socket functionality.
+class WindowsUdpSocket : public UdpSocket {
+  public:
+    enum class Type { kClient, kServer };
+
+    WindowsUdpSocket(SOCKET sock, Type type);
+    ~WindowsUdpSocket() override;
+
+    ssize_t Send(const void* data, size_t len) override;
+    ssize_t Receive(void* data, size_t len, int timeout_ms) override;
+    int Close() override;
+
+  private:
+    SOCKET sock_;
+    int receive_timeout_ms_ = 0;
+    std::unique_ptr<sockaddr_storage> addr_;
+    int addr_size_ = 0;
+
+    DISALLOW_COPY_AND_ASSIGN(WindowsUdpSocket);
+};
+
+WindowsUdpSocket::WindowsUdpSocket(SOCKET sock, Type type) : sock_(sock) {
+    // Only servers need to remember addresses; clients are connected to a server in NewUdpClient()
+    // so will send to that server without needing to specify the address again.
+    if (type == Type::kServer) {
+        addr_.reset(new sockaddr_storage);
+        addr_size_ = sizeof(*addr_);
+        memset(addr_.get(), 0, addr_size_);
+    }
+}
+
+WindowsUdpSocket::~WindowsUdpSocket() {
+    Close();
+}
+
+ssize_t WindowsUdpSocket::Send(const void* data, size_t len) {
+    return sendto(sock_, reinterpret_cast<const char*>(data), len, 0,
+                  reinterpret_cast<sockaddr*>(addr_.get()), addr_size_);
+}
+
+ssize_t WindowsUdpSocket::Receive(void* data, size_t len, int timeout_ms) {
+    // Only set socket timeout if it's changed.
+    if (receive_timeout_ms_ != timeout_ms) {
+        if (setsockopt(sock_, SOL_SOCKET, SO_RCVTIMEO, reinterpret_cast<const char*>(&timeout_ms),
+                       sizeof(timeout_ms)) < 0) {
+            return -1;
+        }
+        receive_timeout_ms_ = timeout_ms;
+    }
+
+    int* addr_size_ptr = nullptr;
+    if (addr_ != nullptr) {
+        // Reset addr_size as it may have been modified by previous recvfrom() calls.
+        addr_size_ = sizeof(*addr_);
+        addr_size_ptr = &addr_size_;
+    }
+    int result = recvfrom(sock_, reinterpret_cast<char*>(data), len, 0,
+                          reinterpret_cast<sockaddr*>(addr_.get()), addr_size_ptr);
+    if (result < 0 && WSAGetLastError() == WSAETIMEDOUT) {
+        errno = EAGAIN;
+    }
+    return result;
+}
+
+int WindowsUdpSocket::Close() {
+    int result = 0;
+    if (sock_ != INVALID_SOCKET) {
+        result = closesocket(sock_);
+        sock_ = INVALID_SOCKET;
+    }
+    return result;
+}
+
+static int GetProtocol(int sock_type) {
+    switch (sock_type) {
+        case SOCK_DGRAM:
+            return IPPROTO_UDP;
+        case SOCK_STREAM:
+            return IPPROTO_TCP;
+        default:
+            // 0 lets the system decide which protocol to use.
+            return 0;
+    }
+}
+
+// Windows implementation of this libcutils function. This function does not make any calls to
+// WSAStartup() or WSACleanup() so that must be handled by the caller.
+// TODO(dpursell): share this code with adb.
+static SOCKET socket_network_client(const std::string& host, int port, int type) {
+    // First resolve the host and port parameters into a usable network address.
+    addrinfo hints;
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_socktype = type;
+    hints.ai_protocol = GetProtocol(type);
+
+    addrinfo* address = nullptr;
+    getaddrinfo(host.c_str(), android::base::StringPrintf("%d", port).c_str(), &hints, &address);
+    if (address == nullptr) {
+        return INVALID_SOCKET;
+    }
+
+    // Now create and connect the socket.
+    SOCKET sock = socket(address->ai_family, address->ai_socktype, address->ai_protocol);
+    if (sock == INVALID_SOCKET) {
+        freeaddrinfo(address);
+        return INVALID_SOCKET;
+    }
+
+    if (connect(sock, address->ai_addr, address->ai_addrlen) == SOCKET_ERROR) {
+        closesocket(sock);
+        freeaddrinfo(address);
+        return INVALID_SOCKET;
+    }
+
+    freeaddrinfo(address);
+    return sock;
+}
+
+// Windows implementation of this libcutils function. This implementation creates a dual-stack
+// server socket that can accept incoming IPv4 or IPv6 packets. This function does not make any
+// calls to WSAStartup() or WSACleanup() so that must be handled by the caller.
+// TODO(dpursell): share this code with adb.
+static SOCKET socket_inaddr_any_server(int port, int type) {
+    SOCKET sock = socket(AF_INET6, type, GetProtocol(type));
+    if (sock == INVALID_SOCKET) {
+        return INVALID_SOCKET;
+    }
+
+    // Enforce exclusive addresses (1), and enable dual-stack so both IPv4 and IPv6 work (2).
+    // (1) https://msdn.microsoft.com/en-us/library/windows/desktop/ms740621(v=vs.85).aspx.
+    // (2) https://msdn.microsoft.com/en-us/library/windows/desktop/bb513665(v=vs.85).aspx.
+    int exclusive = 1;
+    DWORD v6_only = 0;
+    if (setsockopt(sock, SOL_SOCKET, SO_EXCLUSIVEADDRUSE, reinterpret_cast<const char*>(&exclusive),
+                   sizeof(exclusive)) == SOCKET_ERROR ||
+        setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char*>(&v6_only),
+                   sizeof(v6_only)) == SOCKET_ERROR) {
+        closesocket(sock);
+        return INVALID_SOCKET;
+    }
+
+    // Bind the socket to our local port.
+    sockaddr_in6 addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin6_family = AF_INET6;
+    addr.sin6_port = htons(port);
+    addr.sin6_addr = in6addr_any;
+    if (bind(sock, reinterpret_cast<sockaddr*>(&addr), sizeof(addr)) == SOCKET_ERROR) {
+        closesocket(sock);
+        return INVALID_SOCKET;
+    }
+
+    return sock;
+}
+
+// Documentation at https://msdn.microsoft.com/en-us/library/windows/desktop/ms741549(v=vs.85).aspx
+// claims WSACleanup() should be called before program exit, but general consensus seems to be that
+// it hasn't actually been necessary for a long time, possibly since Windows 3.1.
+//
+// Both adb (1) and Chrome (2) purposefully avoid WSACleanup(), and since no adverse affects have
+// been found we may as well do the same here to keep this code simpler.
+// (1) https://android.googlesource.com/platform/system/core.git/+/master/adb/sysdeps_win32.cpp#816
+// (2) https://code.google.com/p/chromium/codesearch#chromium/src/net/base/winsock_init.cc&l=35
+static bool InitWinsock() {
+    static bool init_success = false;
+
+    if (!init_success) {
+        WSADATA wsaData;
+        init_success = (WSAStartup(MAKEWORD(2, 2), &wsaData) == 0);
+    }
+
+    return init_success;
+}
+
+std::unique_ptr<UdpSocket> UdpSocket::NewUdpClient(const std::string& host, int port,
+                                                   std::string* error) {
+    if (!InitWinsock()) {
+        if (error) {
+            *error = android::base::StringPrintf("Failed to initialize Winsock (error %d)",
+                                                 WSAGetLastError());
+        }
+        return nullptr;
+    }
+
+    SOCKET sock = socket_network_client(host, port, SOCK_DGRAM);
+    if (sock == INVALID_SOCKET) {
+        if (error) {
+            *error = android::base::StringPrintf("Failed to connect to %s:%d (error %d)",
+                                                 host.c_str(), port, WSAGetLastError());
+        }
+        return nullptr;
+    }
+
+    return std::unique_ptr<UdpSocket>(new WindowsUdpSocket(sock, WindowsUdpSocket::Type::kClient));
+}
+
+// This functionality is currently only used by tests so we don't need any error messages.
+std::unique_ptr<UdpSocket> UdpSocket::NewUdpServer(int port) {
+    if (!InitWinsock()) {
+        return nullptr;
+    }
+
+    SOCKET sock = socket_inaddr_any_server(port, SOCK_DGRAM);
+    if (sock == INVALID_SOCKET) {
+        return nullptr;
+    }
+
+    return std::unique_ptr<UdpSocket>(new WindowsUdpSocket(sock, WindowsUdpSocket::Type::kServer));
+}