text: /*
   *  Copyright 2006 The WebRTC Project Authors. All rights reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #include <math.h>
  #include <time.h>
  #if defined(WEBRTC_POSIX)
  #include <netinet/in.h>
  #endif
  
  #include <memory>
  
  #include "absl/memory/memory.h"
  #include "rtc_base/arraysize.h"
  #include "rtc_base/fakeclock.h"
  #include "rtc_base/gunit.h"
  #include "rtc_base/logging.h"
  #include "rtc_base/testclient.h"
  #include "rtc_base/testutils.h"
  #include "rtc_base/thread.h"
  #include "rtc_base/timeutils.h"
  #include "rtc_base/virtualsocketserver.h"
  
  using namespace rtc;
  
  using webrtc::testing::SSE_CLOSE;
  using webrtc::testing::SSE_ERROR;
  using webrtc::testing::SSE_OPEN;
  using webrtc::testing::SSE_READ;
  using webrtc::testing::SSE_WRITE;
  using webrtc::testing::StreamSink;
  
  // Sends at a constant rate but with random packet sizes.
  struct Sender : public MessageHandler {
    Sender(Thread* th, AsyncSocket* s, uint32_t rt)
        : thread(th),
          socket(absl::make_unique<AsyncUDPSocket>(s)),
          done(false),
          rate(rt),
          count(0) {
      last_send = rtc::TimeMillis();
      thread->PostDelayed(RTC_FROM_HERE, NextDelay(), this, 1);
    }
  
    uint32_t NextDelay() {
      uint32_t size = (rand() % 4096) + 1;
      return 1000 * size / rate;
    }
  
    void OnMessage(Message* pmsg) override {
      ASSERT_EQ(1u, pmsg->message_id);
  
      if (done)
        return;
  
      int64_t cur_time = rtc::TimeMillis();
      int64_t delay = cur_time - last_send;
      uint32_t size = static_cast<uint32_t>(rate * delay / 1000);
      size = std::min<uint32_t>(size, 4096);
      size = std::max<uint32_t>(size, sizeof(uint32_t));
  
      count += size;
      memcpy(dummy, &cur_time, sizeof(cur_time));
      socket->Send(dummy, size, options);
  
      last_send = cur_time;
      thread->PostDelayed(RTC_FROM_HERE, NextDelay(), this, 1);
    }
  
    Thread* thread;
    std::unique_ptr<AsyncUDPSocket> socket;
    rtc::PacketOptions options;
    bool done;
    uint32_t rate;  // bytes per second
    uint32_t count;
    int64_t last_send;
    char dummy[4096];
  };
  
  struct Receiver : public MessageHandler, public sigslot::has_slots<> {
    Receiver(Thread* th, AsyncSocket* s, uint32_t bw)
        : thread(th),
          socket(absl::make_unique<AsyncUDPSocket>(s)),
          bandwidth(bw),
          done(false),
          count(0),
          sec_count(0),
          sum(0),
          sum_sq(0),
          samples(0) {
      socket->SignalReadPacket.connect(this, &Receiver::OnReadPacket);
      thread->PostDelayed(RTC_FROM_HERE, 1000, this, 1);
    }
  
    ~Receiver() override { thread->Clear(this); }
  
    void OnReadPacket(AsyncPacketSocket* s,
                      const char* data,
                      size_t size,
                      const SocketAddress& remote_addr,
                      const PacketTime& packet_time) {
      ASSERT_EQ(socket.get(), s);
      ASSERT_GE(size, 4U);
  
      count += size;
      sec_count += size;
  
      uint32_t send_time = *reinterpret_cast<const uint32_t*>(data);
      uint32_t recv_time = rtc::TimeMillis();
      uint32_t delay = recv_time - send_time;
      sum += delay;
      sum_sq += delay * delay;
      samples += 1;
    }
  
    void OnMessage(Message* pmsg) override {
      ASSERT_EQ(1u, pmsg->message_id);
  
      if (done)
        return;
  
      // It is always possible for us to receive more than expected because
      // packets can be further delayed in delivery.
      if (bandwidth > 0)
        ASSERT_TRUE(sec_count <= 5 * bandwidth / 4);
      sec_count = 0;
      thread->PostDelayed(RTC_FROM_HERE, 1000, this, 1);
    }
  
    Thread* thread;
    std::unique_ptr<AsyncUDPSocket> socket;
    uint32_t bandwidth;
    bool done;
    size_t count;
    size_t sec_count;
    double sum;
    double sum_sq;
    uint32_t samples;
  };
  
  // Note: This test uses a fake clock in addition to a virtual network.
  class VirtualSocketServerTest : public testing::Test {
   public:
    VirtualSocketServerTest()
        : ss_(&fake_clock_),
          thread_(&ss_),
          kIPv4AnyAddress(IPAddress(INADDR_ANY), 0),
          kIPv6AnyAddress(IPAddress(in6addr_any), 0) {}
  
    void CheckPortIncrementalization(const SocketAddress& post,
                                     const SocketAddress& pre) {
      EXPECT_EQ(post.port(), pre.port() + 1);
      IPAddress post_ip = post.ipaddr();
      IPAddress pre_ip = pre.ipaddr();
      EXPECT_EQ(pre_ip.family(), post_ip.family());
      if (post_ip.family() == AF_INET) {
        in_addr pre_ipv4 = pre_ip.ipv4_address();
        in_addr post_ipv4 = post_ip.ipv4_address();
        EXPECT_EQ(post_ipv4.s_addr, pre_ipv4.s_addr);
      } else if (post_ip.family() == AF_INET6) {
        in6_addr post_ip6 = post_ip.ipv6_address();
        in6_addr pre_ip6 = pre_ip.ipv6_address();
        uint32_t* post_as_ints = reinterpret_cast<uint32_t*>(&post_ip6.s6_addr);
        uint32_t* pre_as_ints = reinterpret_cast<uint32_t*>(&pre_ip6.s6_addr);
        EXPECT_EQ(post_as_ints[3], pre_as_ints[3]);
      }
    }
  
    // Test a client can bind to the any address, and all sent packets will have
    // the default route as the source address. Also, it can receive packets sent
    // to the default route.
    void TestDefaultRoute(const IPAddress& default_route) {
      ss_.SetDefaultRoute(default_route);
  
      // Create client1 bound to the any address.
      AsyncSocket* socket =
          ss_.CreateAsyncSocket(default_route.family(), SOCK_DGRAM);
      socket->Bind(EmptySocketAddressWithFamily(default_route.family()));
      SocketAddress client1_any_addr = socket->GetLocalAddress();
      EXPECT_TRUE(client1_any_addr.IsAnyIP());
      auto client1 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket), &fake_clock_);
  
      // Create client2 bound to the default route.
      AsyncSocket* socket2 =
          ss_.CreateAsyncSocket(default_route.family(), SOCK_DGRAM);
      socket2->Bind(SocketAddress(default_route, 0));
      SocketAddress client2_addr = socket2->GetLocalAddress();
      EXPECT_FALSE(client2_addr.IsAnyIP());
      auto client2 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket2), &fake_clock_);
  
      // Client1 sends to client2, client2 should see the default route as
      // client1's address.
      SocketAddress client1_addr;
      EXPECT_EQ(6, client1->SendTo("bizbaz", 6, client2_addr));
      EXPECT_TRUE(client2->CheckNextPacket("bizbaz", 6, &client1_addr));
      EXPECT_EQ(client1_addr,
                SocketAddress(default_route, client1_any_addr.port()));
  
      // Client2 can send back to client1's default route address.
      EXPECT_EQ(3, client2->SendTo("foo", 3, client1_addr));
      EXPECT_TRUE(client1->CheckNextPacket("foo", 3, &client2_addr));
    }
  
    void BasicTest(const SocketAddress& initial_addr) {
      AsyncSocket* socket =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      socket->Bind(initial_addr);
      SocketAddress server_addr = socket->GetLocalAddress();
      // Make sure VSS didn't switch families on us.
      EXPECT_EQ(server_addr.family(), initial_addr.family());
  
      auto client1 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket), &fake_clock_);
      AsyncSocket* socket2 =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      auto client2 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket2), &fake_clock_);
  
      SocketAddress client2_addr;
      EXPECT_EQ(3, client2->SendTo("foo", 3, server_addr));
      EXPECT_TRUE(client1->CheckNextPacket("foo", 3, &client2_addr));
  
      SocketAddress client1_addr;
      EXPECT_EQ(6, client1->SendTo("bizbaz", 6, client2_addr));
      EXPECT_TRUE(client2->CheckNextPacket("bizbaz", 6, &client1_addr));
      EXPECT_EQ(client1_addr, server_addr);
  
      SocketAddress empty = EmptySocketAddressWithFamily(initial_addr.family());
      for (int i = 0; i < 10; i++) {
        client2 = absl::make_unique<TestClient>(
            absl::WrapUnique(AsyncUDPSocket::Create(&ss_, empty)), &fake_clock_);
  
        SocketAddress next_client2_addr;
        EXPECT_EQ(3, client2->SendTo("foo", 3, server_addr));
        EXPECT_TRUE(client1->CheckNextPacket("foo", 3, &next_client2_addr));
        CheckPortIncrementalization(next_client2_addr, client2_addr);
        // EXPECT_EQ(next_client2_addr.port(), client2_addr.port() + 1);
  
        SocketAddress server_addr2;
        EXPECT_EQ(6, client1->SendTo("bizbaz", 6, next_client2_addr));
        EXPECT_TRUE(client2->CheckNextPacket("bizbaz", 6, &server_addr2));
        EXPECT_EQ(server_addr2, server_addr);
  
        client2_addr = next_client2_addr;
      }
    }
  
    // initial_addr should be made from either INADDR_ANY or in6addr_any.
    void ConnectTest(const SocketAddress& initial_addr) {
      StreamSink sink;
      SocketAddress accept_addr;
      const SocketAddress kEmptyAddr =
          EmptySocketAddressWithFamily(initial_addr.family());
  
      // Create client
      std::unique_ptr<AsyncSocket> client = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(client.get());
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_TRUE(client->GetLocalAddress().IsNil());
  
      // Create server
      std::unique_ptr<AsyncSocket> server = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
      EXPECT_NE(0, server->Listen(5));  // Bind required
      EXPECT_EQ(0, server->Bind(initial_addr));
      EXPECT_EQ(server->GetLocalAddress().family(), initial_addr.family());
      EXPECT_EQ(0, server->Listen(5));
      EXPECT_EQ(server->GetState(), AsyncSocket::CS_CONNECTING);
  
      // No pending server connections
      EXPECT_FALSE(sink.Check(server.get(), SSE_READ));
      EXPECT_TRUE(nullptr == server->Accept(&accept_addr));
      EXPECT_EQ(AF_UNSPEC, accept_addr.family());
  
      // Attempt connect to listening socket
      EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
      EXPECT_NE(client->GetLocalAddress(), kEmptyAddr);          // Implicit Bind
      EXPECT_NE(AF_UNSPEC, client->GetLocalAddress().family());  // Implicit Bind
      EXPECT_NE(client->GetLocalAddress(), server->GetLocalAddress());
  
      // Client is connecting
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CONNECTING);
      EXPECT_FALSE(sink.Check(client.get(), SSE_OPEN));
      EXPECT_FALSE(sink.Check(client.get(), SSE_CLOSE));
  
      ss_.ProcessMessagesUntilIdle();
  
      // Client still connecting
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CONNECTING);
      EXPECT_FALSE(sink.Check(client.get(), SSE_OPEN));
      EXPECT_FALSE(sink.Check(client.get(), SSE_CLOSE));
  
      // Server has pending connection
      EXPECT_TRUE(sink.Check(server.get(), SSE_READ));
      std::unique_ptr<Socket> accepted =
          absl::WrapUnique(server->Accept(&accept_addr));
      EXPECT_TRUE(nullptr != accepted);
      EXPECT_NE(accept_addr, kEmptyAddr);
      EXPECT_EQ(accepted->GetRemoteAddress(), accept_addr);
  
      EXPECT_EQ(accepted->GetState(), AsyncSocket::CS_CONNECTED);
      EXPECT_EQ(accepted->GetLocalAddress(), server->GetLocalAddress());
      EXPECT_EQ(accepted->GetRemoteAddress(), client->GetLocalAddress());
  
      ss_.ProcessMessagesUntilIdle();
  
      // Client has connected
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CONNECTED);
      EXPECT_TRUE(sink.Check(client.get(), SSE_OPEN));
      EXPECT_FALSE(sink.Check(client.get(), SSE_CLOSE));
      EXPECT_EQ(client->GetRemoteAddress(), server->GetLocalAddress());
      EXPECT_EQ(client->GetRemoteAddress(), accepted->GetLocalAddress());
    }
  
    void ConnectToNonListenerTest(const SocketAddress& initial_addr) {
      StreamSink sink;
      SocketAddress accept_addr;
      const SocketAddress nil_addr;
      const SocketAddress empty_addr =
          EmptySocketAddressWithFamily(initial_addr.family());
  
      // Create client
      std::unique_ptr<AsyncSocket> client = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(client.get());
  
      // Create server
      std::unique_ptr<AsyncSocket> server = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
      EXPECT_EQ(0, server->Bind(initial_addr));
      EXPECT_EQ(server->GetLocalAddress().family(), initial_addr.family());
      // Attempt connect to non-listening socket
      EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
  
      ss_.ProcessMessagesUntilIdle();
  
      // No pending server connections
      EXPECT_FALSE(sink.Check(server.get(), SSE_READ));
      EXPECT_TRUE(nullptr == server->Accept(&accept_addr));
      EXPECT_EQ(accept_addr, nil_addr);
  
      // Connection failed
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_FALSE(sink.Check(client.get(), SSE_OPEN));
      EXPECT_TRUE(sink.Check(client.get(), SSE_ERROR));
      EXPECT_EQ(client->GetRemoteAddress(), nil_addr);
    }
  
    void CloseDuringConnectTest(const SocketAddress& initial_addr) {
      StreamSink sink;
      SocketAddress accept_addr;
      const SocketAddress empty_addr =
          EmptySocketAddressWithFamily(initial_addr.family());
  
      // Create client and server
      std::unique_ptr<AsyncSocket> client(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(client.get());
      std::unique_ptr<AsyncSocket> server(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
  
      // Initiate connect
      EXPECT_EQ(0, server->Bind(initial_addr));
      EXPECT_EQ(server->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, server->Listen(5));
      EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
  
      // Server close before socket enters accept queue
      EXPECT_FALSE(sink.Check(server.get(), SSE_READ));
      server->Close();
  
      ss_.ProcessMessagesUntilIdle();
  
      // Result: connection failed
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_TRUE(sink.Check(client.get(), SSE_ERROR));
  
      server.reset(ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
  
      // Initiate connect
      EXPECT_EQ(0, server->Bind(initial_addr));
      EXPECT_EQ(server->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, server->Listen(5));
      EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
  
      ss_.ProcessMessagesUntilIdle();
  
      // Server close while socket is in accept queue
      EXPECT_TRUE(sink.Check(server.get(), SSE_READ));
      server->Close();
  
      ss_.ProcessMessagesUntilIdle();
  
      // Result: connection failed
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_TRUE(sink.Check(client.get(), SSE_ERROR));
  
      // New server
      server.reset(ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
  
      // Initiate connect
      EXPECT_EQ(0, server->Bind(initial_addr));
      EXPECT_EQ(server->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, server->Listen(5));
      EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
  
      ss_.ProcessMessagesUntilIdle();
  
      // Server accepts connection
      EXPECT_TRUE(sink.Check(server.get(), SSE_READ));
      std::unique_ptr<AsyncSocket> accepted(server->Accept(&accept_addr));
      ASSERT_TRUE(nullptr != accepted.get());
      sink.Monitor(accepted.get());
  
      // Client closes before connection complets
      EXPECT_EQ(accepted->GetState(), AsyncSocket::CS_CONNECTED);
  
      // Connected message has not been processed yet.
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CONNECTING);
      client->Close();
  
      ss_.ProcessMessagesUntilIdle();
  
      // Result: accepted socket closes
      EXPECT_EQ(accepted->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_TRUE(sink.Check(accepted.get(), SSE_CLOSE));
      EXPECT_FALSE(sink.Check(client.get(), SSE_CLOSE));
    }
  
    void CloseTest(const SocketAddress& initial_addr) {
      StreamSink sink;
      const SocketAddress kEmptyAddr;
  
      // Create clients
      std::unique_ptr<AsyncSocket> a = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(a.get());
      a->Bind(initial_addr);
      EXPECT_EQ(a->GetLocalAddress().family(), initial_addr.family());
  
      std::unique_ptr<AsyncSocket> b = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(b.get());
      b->Bind(initial_addr);
      EXPECT_EQ(b->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, a->Connect(b->GetLocalAddress()));
      EXPECT_EQ(0, b->Connect(a->GetLocalAddress()));
  
      ss_.ProcessMessagesUntilIdle();
  
      EXPECT_TRUE(sink.Check(a.get(), SSE_OPEN));
      EXPECT_EQ(a->GetState(), AsyncSocket::CS_CONNECTED);
      EXPECT_EQ(a->GetRemoteAddress(), b->GetLocalAddress());
  
      EXPECT_TRUE(sink.Check(b.get(), SSE_OPEN));
      EXPECT_EQ(b->GetState(), AsyncSocket::CS_CONNECTED);
      EXPECT_EQ(b->GetRemoteAddress(), a->GetLocalAddress());
  
      EXPECT_EQ(1, a->Send("a", 1));
      b->Close();
      EXPECT_EQ(1, a->Send("b", 1));
  
      ss_.ProcessMessagesUntilIdle();
  
      char buffer[10];
      EXPECT_FALSE(sink.Check(b.get(), SSE_READ));
      EXPECT_EQ(-1, b->Recv(buffer, 10, nullptr));
  
      EXPECT_TRUE(sink.Check(a.get(), SSE_CLOSE));
      EXPECT_EQ(a->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_EQ(a->GetRemoteAddress(), kEmptyAddr);
  
      // No signal for Closer
      EXPECT_FALSE(sink.Check(b.get(), SSE_CLOSE));
      EXPECT_EQ(b->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_EQ(b->GetRemoteAddress(), kEmptyAddr);
    }
  
    void TcpSendTest(const SocketAddress& initial_addr) {
      StreamSink sink;
      const SocketAddress kEmptyAddr;
  
      // Connect two sockets
      std::unique_ptr<AsyncSocket> a = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(a.get());
      a->Bind(initial_addr);
      EXPECT_EQ(a->GetLocalAddress().family(), initial_addr.family());
  
      std::unique_ptr<AsyncSocket> b = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      sink.Monitor(b.get());
      b->Bind(initial_addr);
      EXPECT_EQ(b->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, a->Connect(b->GetLocalAddress()));
      EXPECT_EQ(0, b->Connect(a->GetLocalAddress()));
  
      ss_.ProcessMessagesUntilIdle();
  
      const size_t kBufferSize = 2000;
      ss_.set_send_buffer_capacity(kBufferSize);
      ss_.set_recv_buffer_capacity(kBufferSize);
  
      const size_t kDataSize = 5000;
      char send_buffer[kDataSize], recv_buffer[kDataSize];
      for (size_t i = 0; i < kDataSize; ++i)
        send_buffer[i] = static_cast<char>(i % 256);
      memset(recv_buffer, 0, sizeof(recv_buffer));
      size_t send_pos = 0, recv_pos = 0;
  
      // Can't send more than send buffer in one write
      int result = a->Send(send_buffer + send_pos, kDataSize - send_pos);
      EXPECT_EQ(static_cast<int>(kBufferSize), result);
      send_pos += result;
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_FALSE(sink.Check(a.get(), SSE_WRITE));
      EXPECT_TRUE(sink.Check(b.get(), SSE_READ));
  
      // Receive buffer is already filled, fill send buffer again
      result = a->Send(send_buffer + send_pos, kDataSize - send_pos);
      EXPECT_EQ(static_cast<int>(kBufferSize), result);
      send_pos += result;
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_FALSE(sink.Check(a.get(), SSE_WRITE));
      EXPECT_FALSE(sink.Check(b.get(), SSE_READ));
  
      // No more room in send or receive buffer
      result = a->Send(send_buffer + send_pos, kDataSize - send_pos);
      EXPECT_EQ(-1, result);
      EXPECT_TRUE(a->IsBlocking());
  
      // Read a subset of the data
      result = b->Recv(recv_buffer + recv_pos, 500, nullptr);
      EXPECT_EQ(500, result);
      recv_pos += result;
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_TRUE(sink.Check(a.get(), SSE_WRITE));
      EXPECT_TRUE(sink.Check(b.get(), SSE_READ));
  
      // Room for more on the sending side
      result = a->Send(send_buffer + send_pos, kDataSize - send_pos);
      EXPECT_EQ(500, result);
      send_pos += result;
  
      // Empty the recv buffer
      while (true) {
        result = b->Recv(recv_buffer + recv_pos, kDataSize - recv_pos, nullptr);
        if (result < 0) {
          EXPECT_EQ(-1, result);
          EXPECT_TRUE(b->IsBlocking());
          break;
        }
        recv_pos += result;
      }
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_TRUE(sink.Check(b.get(), SSE_READ));
  
      // Continue to empty the recv buffer
      while (true) {
        result = b->Recv(recv_buffer + recv_pos, kDataSize - recv_pos, nullptr);
        if (result < 0) {
          EXPECT_EQ(-1, result);
          EXPECT_TRUE(b->IsBlocking());
          break;
        }
        recv_pos += result;
      }
  
      // Send last of the data
      result = a->Send(send_buffer + send_pos, kDataSize - send_pos);
      EXPECT_EQ(500, result);
      send_pos += result;
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_TRUE(sink.Check(b.get(), SSE_READ));
  
      // Receive the last of the data
      while (true) {
        result = b->Recv(recv_buffer + recv_pos, kDataSize - recv_pos, nullptr);
        if (result < 0) {
          EXPECT_EQ(-1, result);
          EXPECT_TRUE(b->IsBlocking());
          break;
        }
        recv_pos += result;
      }
  
      ss_.ProcessMessagesUntilIdle();
      EXPECT_FALSE(sink.Check(b.get(), SSE_READ));
  
      // The received data matches the sent data
      EXPECT_EQ(kDataSize, send_pos);
      EXPECT_EQ(kDataSize, recv_pos);
      EXPECT_EQ(0, memcmp(recv_buffer, send_buffer, kDataSize));
    }
  
    void TcpSendsPacketsInOrderTest(const SocketAddress& initial_addr) {
      const SocketAddress kEmptyAddr;
  
      // Connect two sockets
      std::unique_ptr<AsyncSocket> a = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      std::unique_ptr<AsyncSocket> b = absl::WrapUnique(
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_STREAM));
      a->Bind(initial_addr);
      EXPECT_EQ(a->GetLocalAddress().family(), initial_addr.family());
  
      b->Bind(initial_addr);
      EXPECT_EQ(b->GetLocalAddress().family(), initial_addr.family());
  
      EXPECT_EQ(0, a->Connect(b->GetLocalAddress()));
      EXPECT_EQ(0, b->Connect(a->GetLocalAddress()));
      ss_.ProcessMessagesUntilIdle();
  
      // First, deliver all packets in 0 ms.
      char buffer[2] = {0, 0};
      const char cNumPackets = 10;
      for (char i = 0; i < cNumPackets; ++i) {
        buffer[0] = '0' + i;
        EXPECT_EQ(1, a->Send(buffer, 1));
      }
  
      ss_.ProcessMessagesUntilIdle();
  
      for (char i = 0; i < cNumPackets; ++i) {
        EXPECT_EQ(1, b->Recv(buffer, sizeof(buffer), nullptr));
        EXPECT_EQ(static_cast<char>('0' + i), buffer[0]);
      }
  
      // Next, deliver packets at random intervals
      const uint32_t mean = 50;
      const uint32_t stddev = 50;
  
      ss_.set_delay_mean(mean);
      ss_.set_delay_stddev(stddev);
      ss_.UpdateDelayDistribution();
  
      for (char i = 0; i < cNumPackets; ++i) {
        buffer[0] = 'A' + i;
        EXPECT_EQ(1, a->Send(buffer, 1));
      }
  
      ss_.ProcessMessagesUntilIdle();
  
      for (char i = 0; i < cNumPackets; ++i) {
        EXPECT_EQ(1, b->Recv(buffer, sizeof(buffer), nullptr));
        EXPECT_EQ(static_cast<char>('A' + i), buffer[0]);
      }
    }
  
    // It is important that initial_addr's port has to be 0 such that the
    // incremental port behavior could ensure the 2 Binds result in different
    // address.
    void BandwidthTest(const SocketAddress& initial_addr) {
      AsyncSocket* send_socket =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      AsyncSocket* recv_socket =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      ASSERT_EQ(0, send_socket->Bind(initial_addr));
      ASSERT_EQ(0, recv_socket->Bind(initial_addr));
      EXPECT_EQ(send_socket->GetLocalAddress().family(), initial_addr.family());
      EXPECT_EQ(recv_socket->GetLocalAddress().family(), initial_addr.family());
      ASSERT_EQ(0, send_socket->Connect(recv_socket->GetLocalAddress()));
  
      uint32_t bandwidth = 64 * 1024;
      ss_.set_bandwidth(bandwidth);
  
      Thread* pthMain = Thread::Current();
      Sender sender(pthMain, send_socket, 80 * 1024);
      Receiver receiver(pthMain, recv_socket, bandwidth);
  
      // Allow the sender to run for 5 (simulated) seconds, then be stopped for 5
      // seconds.
      SIMULATED_WAIT(false, 5000, fake_clock_);
      sender.done = true;
      SIMULATED_WAIT(false, 5000, fake_clock_);
  
      // Ensure the observed bandwidth fell within a reasonable margin of error.
      EXPECT_TRUE(receiver.count >= 5 * 3 * bandwidth / 4);
      EXPECT_TRUE(receiver.count <= 6 * bandwidth);  // queue could drain for 1s
  
      ss_.set_bandwidth(0);
    }
  
    // It is important that initial_addr's port has to be 0 such that the
    // incremental port behavior could ensure the 2 Binds result in different
    // address.
    void DelayTest(const SocketAddress& initial_addr) {
      time_t seed = ::time(nullptr);
      RTC_LOG(LS_VERBOSE) << "seed = " << seed;
      srand(static_cast<unsigned int>(seed));
  
      const uint32_t mean = 2000;
      const uint32_t stddev = 500;
  
      ss_.set_delay_mean(mean);
      ss_.set_delay_stddev(stddev);
      ss_.UpdateDelayDistribution();
  
      AsyncSocket* send_socket =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      AsyncSocket* recv_socket =
          ss_.CreateAsyncSocket(initial_addr.family(), SOCK_DGRAM);
      ASSERT_EQ(0, send_socket->Bind(initial_addr));
      ASSERT_EQ(0, recv_socket->Bind(initial_addr));
      EXPECT_EQ(send_socket->GetLocalAddress().family(), initial_addr.family());
      EXPECT_EQ(recv_socket->GetLocalAddress().family(), initial_addr.family());
      ASSERT_EQ(0, send_socket->Connect(recv_socket->GetLocalAddress()));
  
      Thread* pthMain = Thread::Current();
      // Avg packet size is 2K, so at 200KB/s for 10s, we should see about
      // 1000 packets, which is necessary to get a good distribution.
      Sender sender(pthMain, send_socket, 100 * 2 * 1024);
      Receiver receiver(pthMain, recv_socket, 0);
  
      // Simulate 10 seconds of packets being sent, then check the observed delay
      // distribution.
      SIMULATED_WAIT(false, 10000, fake_clock_);
      sender.done = receiver.done = true;
      ss_.ProcessMessagesUntilIdle();
  
      const double sample_mean = receiver.sum / receiver.samples;
      double num =
          receiver.samples * receiver.sum_sq - receiver.sum * receiver.sum;
      double den = receiver.samples * (receiver.samples - 1);
      const double sample_stddev = sqrt(num / den);
      RTC_LOG(LS_VERBOSE) << "mean=" << sample_mean
                          << " stddev=" << sample_stddev;
  
      EXPECT_LE(500u, receiver.samples);
      // We initially used a 0.1 fudge factor, but on the build machine, we
      // have seen the value differ by as much as 0.13.
      EXPECT_NEAR(mean, sample_mean, 0.15 * mean);
      EXPECT_NEAR(stddev, sample_stddev, 0.15 * stddev);
  
      ss_.set_delay_mean(0);
      ss_.set_delay_stddev(0);
      ss_.UpdateDelayDistribution();
    }
  
    // Test cross-family communication between a client bound to client_addr and a
    // server bound to server_addr. shouldSucceed indicates if communication is
    // expected to work or not.
    void CrossFamilyConnectionTest(const SocketAddress& client_addr,
                                   const SocketAddress& server_addr,
                                   bool shouldSucceed) {
      StreamSink sink;
      SocketAddress accept_address;
      const SocketAddress kEmptyAddr;
  
      // Client gets a IPv4 address
      std::unique_ptr<AsyncSocket> client = absl::WrapUnique(
          ss_.CreateAsyncSocket(client_addr.family(), SOCK_STREAM));
      sink.Monitor(client.get());
      EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
      EXPECT_EQ(client->GetLocalAddress(), kEmptyAddr);
      client->Bind(client_addr);
  
      // Server gets a non-mapped non-any IPv6 address.
      // IPv4 sockets should not be able to connect to this.
      std::unique_ptr<AsyncSocket> server = absl::WrapUnique(
          ss_.CreateAsyncSocket(server_addr.family(), SOCK_STREAM));
      sink.Monitor(server.get());
      server->Bind(server_addr);
      server->Listen(5);
  
      if (shouldSucceed) {
        EXPECT_EQ(0, client->Connect(server->GetLocalAddress()));
        ss_.ProcessMessagesUntilIdle();
        EXPECT_TRUE(sink.Check(server.get(), SSE_READ));
        std::unique_ptr<Socket> accepted =
            absl::WrapUnique(server->Accept(&accept_address));
        EXPECT_TRUE(nullptr != accepted);
        EXPECT_NE(kEmptyAddr, accept_address);
        ss_.ProcessMessagesUntilIdle();
        EXPECT_TRUE(sink.Check(client.get(), SSE_OPEN));
        EXPECT_EQ(client->GetRemoteAddress(), server->GetLocalAddress());
      } else {
        // Check that the connection failed.
        EXPECT_EQ(-1, client->Connect(server->GetLocalAddress()));
        ss_.ProcessMessagesUntilIdle();
  
        EXPECT_FALSE(sink.Check(server.get(), SSE_READ));
        EXPECT_TRUE(nullptr == server->Accept(&accept_address));
        EXPECT_EQ(accept_address, kEmptyAddr);
        EXPECT_EQ(client->GetState(), AsyncSocket::CS_CLOSED);
        EXPECT_FALSE(sink.Check(client.get(), SSE_OPEN));
        EXPECT_EQ(client->GetRemoteAddress(), kEmptyAddr);
      }
    }
  
    // Test cross-family datagram sending between a client bound to client_addr
    // and a server bound to server_addr. shouldSucceed indicates if sending is
    // expected to succeed or not.
    void CrossFamilyDatagramTest(const SocketAddress& client_addr,
                                 const SocketAddress& server_addr,
                                 bool shouldSucceed) {
      AsyncSocket* socket = ss_.CreateAsyncSocket(AF_INET, SOCK_DGRAM);
      socket->Bind(server_addr);
      SocketAddress bound_server_addr = socket->GetLocalAddress();
      auto client1 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket), &fake_clock_);
  
      AsyncSocket* socket2 = ss_.CreateAsyncSocket(AF_INET, SOCK_DGRAM);
      socket2->Bind(client_addr);
      auto client2 = absl::make_unique<TestClient>(
          absl::make_unique<AsyncUDPSocket>(socket2), &fake_clock_);
      SocketAddress client2_addr;
  
      if (shouldSucceed) {
        EXPECT_EQ(3, client2->SendTo("foo", 3, bound_server_addr));
        EXPECT_TRUE(client1->CheckNextPacket("foo", 3, &client2_addr));
        SocketAddress client1_addr;
        EXPECT_EQ(6, client1->SendTo("bizbaz", 6, client2_addr));
        EXPECT_TRUE(client2->CheckNextPacket("bizbaz", 6, &client1_addr));
        EXPECT_EQ(client1_addr, bound_server_addr);
      } else {
        EXPECT_EQ(-1, client2->SendTo("foo", 3, bound_server_addr));
        EXPECT_TRUE(client1->CheckNoPacket());
      }
    }
  
   protected:
    rtc::ScopedFakeClock fake_clock_;
    VirtualSocketServer ss_;
    AutoSocketServerThread thread_;
    const SocketAddress kIPv4AnyAddress;
    const SocketAddress kIPv6AnyAddress;
  };
  
  TEST_F(VirtualSocketServerTest, basic_v4) {
    SocketAddress ipv4_test_addr(IPAddress(INADDR_ANY), 5000);
    BasicTest(ipv4_test_addr);
  }
  
  TEST_F(VirtualSocketServerTest, basic_v6) {
    SocketAddress ipv6_test_addr(IPAddress(in6addr_any), 5000);
    BasicTest(ipv6_test_addr);
  }
  
  TEST_F(VirtualSocketServerTest, TestDefaultRoute_v4) {
    IPAddress ipv4_default_addr(0x01020304);
    TestDefaultRoute(ipv4_default_addr);
  }
  
  TEST_F(VirtualSocketServerTest, TestDefaultRoute_v6) {
    IPAddress ipv6_default_addr;
    EXPECT_TRUE(
        IPFromString("2401:fa00:4:1000:be30:5bff:fee5:c3", &ipv6_default_addr));
    TestDefaultRoute(ipv6_default_addr);
  }
  
  TEST_F(VirtualSocketServerTest, connect_v4) {
    ConnectTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, connect_v6) {
    ConnectTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, connect_to_non_listener_v4) {
    ConnectToNonListenerTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, connect_to_non_listener_v6) {
    ConnectToNonListenerTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, close_during_connect_v4) {
    CloseDuringConnectTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, close_during_connect_v6) {
    CloseDuringConnectTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, close_v4) {
    CloseTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, close_v6) {
    CloseTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, tcp_send_v4) {
    TcpSendTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, tcp_send_v6) {
    TcpSendTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, TcpSendsPacketsInOrder_v4) {
    TcpSendsPacketsInOrderTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, TcpSendsPacketsInOrder_v6) {
    TcpSendsPacketsInOrderTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, bandwidth_v4) {
    BandwidthTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, bandwidth_v6) {
    BandwidthTest(kIPv6AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, delay_v4) {
    DelayTest(kIPv4AnyAddress);
  }
  
  TEST_F(VirtualSocketServerTest, delay_v6) {
    DelayTest(kIPv6AnyAddress);
  }
  
  // Works, receiving socket sees 127.0.0.2.
  TEST_F(VirtualSocketServerTest, CanConnectFromMappedIPv6ToIPv4Any) {
    CrossFamilyConnectionTest(SocketAddress("::ffff:127.0.0.2", 0),
                              SocketAddress("0.0.0.0", 5000), true);
  }
  
  // Fails.
  TEST_F(VirtualSocketServerTest, CantConnectFromUnMappedIPv6ToIPv4Any) {
    CrossFamilyConnectionTest(SocketAddress("::2", 0),
                              SocketAddress("0.0.0.0", 5000), false);
  }
  
  // Fails.
  TEST_F(VirtualSocketServerTest, CantConnectFromUnMappedIPv6ToMappedIPv6) {
    CrossFamilyConnectionTest(SocketAddress("::2", 0),
                              SocketAddress("::ffff:127.0.0.1", 5000), false);
  }
  
  // Works. receiving socket sees ::ffff:127.0.0.2.
  TEST_F(VirtualSocketServerTest, CanConnectFromIPv4ToIPv6Any) {
    CrossFamilyConnectionTest(SocketAddress("127.0.0.2", 0),
                              SocketAddress("::", 5000), true);
  }
  
  // Fails.
  TEST_F(VirtualSocketServerTest, CantConnectFromIPv4ToUnMappedIPv6) {
    CrossFamilyConnectionTest(SocketAddress("127.0.0.2", 0),
                              SocketAddress("::1", 5000), false);
  }
  
  // Works. Receiving socket sees ::ffff:127.0.0.1.
  TEST_F(VirtualSocketServerTest, CanConnectFromIPv4ToMappedIPv6) {
    CrossFamilyConnectionTest(SocketAddress("127.0.0.1", 0),
                              SocketAddress("::ffff:127.0.0.2", 5000), true);
  }
  
  // Works, receiving socket sees a result from GetNextIP.
  TEST_F(VirtualSocketServerTest, CanConnectFromUnboundIPv6ToIPv4Any) {
    CrossFamilyConnectionTest(SocketAddress("::", 0),
                              SocketAddress("0.0.0.0", 5000), true);
  }
  
  // Works, receiving socket sees whatever GetNextIP gave the client.
  TEST_F(VirtualSocketServerTest, CanConnectFromUnboundIPv4ToIPv6Any) {
    CrossFamilyConnectionTest(SocketAddress("0.0.0.0", 0),
                              SocketAddress("::", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, CanSendDatagramFromUnboundIPv4ToIPv6Any) {
    CrossFamilyDatagramTest(SocketAddress("0.0.0.0", 0),
                            SocketAddress("::", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, CanSendDatagramFromMappedIPv6ToIPv4Any) {
    CrossFamilyDatagramTest(SocketAddress("::ffff:127.0.0.1", 0),
                            SocketAddress("0.0.0.0", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, CantSendDatagramFromUnMappedIPv6ToIPv4Any) {
    CrossFamilyDatagramTest(SocketAddress("::2", 0),
                            SocketAddress("0.0.0.0", 5000), false);
  }
  
  TEST_F(VirtualSocketServerTest, CantSendDatagramFromUnMappedIPv6ToMappedIPv6) {
    CrossFamilyDatagramTest(SocketAddress("::2", 0),
                            SocketAddress("::ffff:127.0.0.1", 5000), false);
  }
  
  TEST_F(VirtualSocketServerTest, CanSendDatagramFromIPv4ToIPv6Any) {
    CrossFamilyDatagramTest(SocketAddress("127.0.0.2", 0),
                            SocketAddress("::", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, CantSendDatagramFromIPv4ToUnMappedIPv6) {
    CrossFamilyDatagramTest(SocketAddress("127.0.0.2", 0),
                            SocketAddress("::1", 5000), false);
  }
  
  TEST_F(VirtualSocketServerTest, CanSendDatagramFromIPv4ToMappedIPv6) {
    CrossFamilyDatagramTest(SocketAddress("127.0.0.1", 0),
                            SocketAddress("::ffff:127.0.0.2", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, CanSendDatagramFromUnboundIPv6ToIPv4Any) {
    CrossFamilyDatagramTest(SocketAddress("::", 0),
                            SocketAddress("0.0.0.0", 5000), true);
  }
  
  TEST_F(VirtualSocketServerTest, SetSendingBlockedWithUdpSocket) {
    AsyncSocket* socket1 =
        ss_.CreateAsyncSocket(kIPv4AnyAddress.family(), SOCK_DGRAM);
    std::unique_ptr<AsyncSocket> socket2 = absl::WrapUnique(
        ss_.CreateAsyncSocket(kIPv4AnyAddress.family(), SOCK_DGRAM));
    socket1->Bind(kIPv4AnyAddress);
    socket2->Bind(kIPv4AnyAddress);
    auto client1 = absl::make_unique<TestClient>(
        absl::make_unique<AsyncUDPSocket>(socket1), &fake_clock_);
  
    ss_.SetSendingBlocked(true);
    EXPECT_EQ(-1, client1->SendTo("foo", 3, socket2->GetLocalAddress()));
    EXPECT_TRUE(socket1->IsBlocking());
    EXPECT_EQ(0, client1->ready_to_send_count());
  
    ss_.SetSendingBlocked(false);
    EXPECT_EQ(1, client1->ready_to_send_count());
    EXPECT_EQ(3, client1->SendTo("foo", 3, socket2->GetLocalAddress()));
  }
  
  TEST_F(VirtualSocketServerTest, SetSendingBlockedWithTcpSocket) {
    constexpr size_t kBufferSize = 1024;
    ss_.set_send_buffer_capacity(kBufferSize);
    ss_.set_recv_buffer_capacity(kBufferSize);
  
    StreamSink sink;
    std::unique_ptr<AsyncSocket> socket1 = absl::WrapUnique(
        ss_.CreateAsyncSocket(kIPv4AnyAddress.family(), SOCK_STREAM));
    std::unique_ptr<AsyncSocket> socket2 = absl::WrapUnique(
        ss_.CreateAsyncSocket(kIPv4AnyAddress.family(), SOCK_STREAM));
    sink.Monitor(socket1.get());
    sink.Monitor(socket2.get());
    socket1->Bind(kIPv4AnyAddress);
    socket2->Bind(kIPv4AnyAddress);
  
    // Connect sockets.
    EXPECT_EQ(0, socket1->Connect(socket2->GetLocalAddress()));
    EXPECT_EQ(0, socket2->Connect(socket1->GetLocalAddress()));
    ss_.ProcessMessagesUntilIdle();
  
    char data[kBufferSize] = {};
  
    // First Send call will fill the send buffer but not send anything.
    ss_.SetSendingBlocked(true);
    EXPECT_EQ(static_cast<int>(kBufferSize), socket1->Send(data, kBufferSize));
    ss_.ProcessMessagesUntilIdle();
    EXPECT_FALSE(sink.Check(socket1.get(), SSE_WRITE));
    EXPECT_FALSE(sink.Check(socket2.get(), SSE_READ));
    EXPECT_FALSE(socket1->IsBlocking());
  
    // Since the send buffer is full, next Send will result in EWOULDBLOCK.
    EXPECT_EQ(-1, socket1->Send(data, kBufferSize));
    EXPECT_FALSE(sink.Check(socket1.get(), SSE_WRITE));
    EXPECT_FALSE(sink.Check(socket2.get(), SSE_READ));
    EXPECT_TRUE(socket1->IsBlocking());
  
    // When sending is unblocked, the buffered data should be sent and
    // SignalWriteEvent should fire.
    ss_.SetSendingBlocked(false);
    ss_.ProcessMessagesUntilIdle();
    EXPECT_TRUE(sink.Check(socket1.get(), SSE_WRITE));
    EXPECT_TRUE(sink.Check(socket2.get(), SSE_READ));
  }
  
  TEST_F(VirtualSocketServerTest, CreatesStandardDistribution) {
    const uint32_t kTestMean[] = {10, 100, 333, 1000};
    const double kTestDev[] = {0.25, 0.1, 0.01};
    // TODO(deadbeef): The current code only works for 1000 data points or more.
    const uint32_t kTestSamples[] = {/*10, 100,*/ 1000};
    for (size_t midx = 0; midx < arraysize(kTestMean); ++midx) {
      for (size_t didx = 0; didx < arraysize(kTestDev); ++didx) {
        for (size_t sidx = 0; sidx < arraysize(kTestSamples); ++sidx) {
          ASSERT_LT(0u, kTestSamples[sidx]);
          const uint32_t kStdDev =
              static_cast<uint32_t>(kTestDev[didx] * kTestMean[midx]);
          VirtualSocketServer::Function* f =
              VirtualSocketServer::CreateDistribution(kTestMean[midx], kStdDev,
                                                      kTestSamples[sidx]);
          ASSERT_TRUE(nullptr != f);
          ASSERT_EQ(kTestSamples[sidx], f->size());
          double sum = 0;
          for (uint32_t i = 0; i < f->size(); ++i) {
            sum += (*f)[i].second;
          }
          const double mean = sum / f->size();
          double sum_sq_dev = 0;
          for (uint32_t i = 0; i < f->size(); ++i) {
            double dev = (*f)[i].second - mean;
            sum_sq_dev += dev * dev;
          }
          const double stddev = sqrt(sum_sq_dev / f->size());
          EXPECT_NEAR(kTestMean[midx], mean, 0.1 * kTestMean[midx])
              << "M=" << kTestMean[midx] << " SD=" << kStdDev
              << " N=" << kTestSamples[sidx];
          EXPECT_NEAR(kStdDev, stddev, 0.1 * kStdDev)
              << "M=" << kTestMean[midx] << " SD=" << kStdDev
              << " N=" << kTestSamples[sidx];
          delete f;
        }
      }
    }
  }
  