Revert "Remove stun_prober"

This reverts commit 03f56d75d5a4bbbc6b6fe93e119f73c69ff98267.

Reason for revert: Breaks downstream project.

Original change's description:
> Remove stun_prober
>
> The STUN prober shows the old RFC 3489 way of determining the NAT type
> by pinging two different servers. This is known to be faulty as pointed
> out by
>   https://datatracker.ietf.org/doc/html/rfc5389#section-2
>
> Chromium dependency removed in
>   https://chromium-review.googlesource.com/c/chromium/src/+/6036622
>
> BUG=None
>
> Change-Id: I2b61dfe2ff899ce71ec9d2253dc836c5908cf8c6
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/368182
> Commit-Queue: Philipp Hancke <phancke@meta.com>
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#43503}

Bug: None
Change-Id: I08d01d4c9d882aca883e1c889aed8bddbca65b91
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/370540
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Jeremy Leconte <jleconte@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43506}

BUILD.gn

@@ -650,6 +650,7 @@ if (rtc_include_tests && !build_with_chromium) {
       "api/video_codecs/test:video_codecs_api_unittests",
       "api/voip:compile_all_headers",
       "call:fake_network_pipe_unittests",
+      "p2p:libstunprober_unittests",
       "p2p:rtc_p2p_unittests",
       "rtc_base:async_dns_resolver_unittests",
       "rtc_base:async_packet_socket_unittest",

examples/BUILD.gn

@@ -42,6 +42,10 @@ group("examples") {
     }
   }
 
+  if (!build_with_chromium) {
+    deps += [ ":stun_prober" ]
+  }
+
   if (is_ios || (is_mac && target_cpu != "x86")) {
     deps += [ ":AppRTCMobile" ]
   }
@@ -865,3 +869,32 @@ if (is_android) {
         ] ]
   }
 }
+
+if (!build_with_chromium) {
+  # Doesn't build within Chrome on Win.
+  rtc_executable("stun_prober") {
+    testonly = true
+    sources = [ "stunprober/main.cc" ]
+    deps = [
+      "../p2p:basic_packet_socket_factory",
+      "../p2p:libstunprober",
+      "../p2p:rtc_p2p",
+      "../rtc_base:checks",
+      "../rtc_base:crypto_random",
+      "../rtc_base:logging",
+      "../rtc_base:network",
+      "../rtc_base:socket_address",
+      "../rtc_base:ssl_adapter",
+      "../rtc_base:threading",
+      "../rtc_base:timeutils",
+      "../test:scoped_key_value_config",
+      "//third_party/abseil-cpp/absl/flags:flag",
+      "//third_party/abseil-cpp/absl/flags:parse",
+    ]
+    if (is_win) {
+      deps += [
+        "../rtc_base:win32_socket_init",
+      ]
+    }
+  }
+}

examples/stunprober/main.cc

@@ -0,0 +1,153 @@
+/*
+ *  Copyright 2015 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 <memory>
+#include <set>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "absl/flags/flag.h"
+#include "absl/flags/parse.h"
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/stunprober/stun_prober.h"
+#include "rtc_base/crypto_random.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/network.h"
+#include "rtc_base/physical_socket_server.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+#include "test/scoped_key_value_config.h"
+
+#ifdef WEBRTC_WIN
+#include "rtc_base/win32_socket_init.h"
+#endif  // WEBRTC_WIN
+
+using stunprober::AsyncCallback;
+using stunprober::StunProber;
+
+ABSL_FLAG(int,
+          interval,
+          10,
+          "Interval of consecutive stun pings in milliseconds");
+ABSL_FLAG(bool,
+          shared_socket,
+          false,
+          "Share socket mode for different remote IPs");
+ABSL_FLAG(int,
+          pings_per_ip,
+          10,
+          "Number of consecutive stun pings to send for each IP");
+ABSL_FLAG(int,
+          timeout,
+          1000,
+          "Milliseconds of wait after the last ping sent before exiting");
+ABSL_FLAG(
+    std::string,
+    servers,
+    "stun.l.google.com:19302,stun1.l.google.com:19302,stun2.l.google.com:19302",
+    "Comma separated STUN server addresses with ports");
+
+namespace {
+
+const char* PrintNatType(stunprober::NatType type) {
+  switch (type) {
+    case stunprober::NATTYPE_NONE:
+      return "Not behind a NAT";
+    case stunprober::NATTYPE_UNKNOWN:
+      return "Unknown NAT type";
+    case stunprober::NATTYPE_SYMMETRIC:
+      return "Symmetric NAT";
+    case stunprober::NATTYPE_NON_SYMMETRIC:
+      return "Non-Symmetric NAT";
+    default:
+      return "Invalid";
+  }
+}
+
+void PrintStats(StunProber* prober) {
+  StunProber::Stats stats;
+  if (!prober->GetStats(&stats)) {
+    RTC_LOG(LS_WARNING) << "Results are inconclusive.";
+    return;
+  }
+
+  RTC_LOG(LS_INFO) << "Shared Socket Mode: " << stats.shared_socket_mode;
+  RTC_LOG(LS_INFO) << "Requests sent: " << stats.num_request_sent;
+  RTC_LOG(LS_INFO) << "Responses received: " << stats.num_response_received;
+  RTC_LOG(LS_INFO) << "Target interval (ns): "
+                   << stats.target_request_interval_ns;
+  RTC_LOG(LS_INFO) << "Actual interval (ns): "
+                   << stats.actual_request_interval_ns;
+  RTC_LOG(LS_INFO) << "NAT Type: " << PrintNatType(stats.nat_type);
+  RTC_LOG(LS_INFO) << "Host IP: " << stats.host_ip;
+  RTC_LOG(LS_INFO) << "Server-reflexive ips: ";
+  for (auto& ip : stats.srflx_addrs) {
+    RTC_LOG(LS_INFO) << "\t" << ip;
+  }
+
+  RTC_LOG(LS_INFO) << "Success Precent: " << stats.success_percent;
+  RTC_LOG(LS_INFO) << "Response Latency:" << stats.average_rtt_ms;
+}
+
+void StopTrial(rtc::Thread* thread, StunProber* prober, int result) {
+  thread->Quit();
+  if (prober) {
+    RTC_LOG(LS_INFO) << "Result: " << result;
+    if (result == StunProber::SUCCESS) {
+      PrintStats(prober);
+    }
+  }
+}
+
+}  // namespace
+
+int main(int argc, char* argv[]) {
+#ifdef WEBRTC_WIN
+  rtc::WinsockInitializer winsock_init;
+#endif  // WEBRTC_WIN
+  absl::ParseCommandLine(argc, argv);
+
+  std::vector<rtc::SocketAddress> server_addresses;
+  std::istringstream servers(absl::GetFlag(FLAGS_servers));
+  std::string server;
+  while (getline(servers, server, ',')) {
+    rtc::SocketAddress addr;
+    if (!addr.FromString(server)) {
+      RTC_LOG(LS_ERROR) << "Parsing " << server << " failed.";
+      return -1;
+    }
+    server_addresses.push_back(addr);
+  }
+
+  rtc::InitializeSSL();
+  rtc::InitRandom(rtc::Time32());
+  webrtc::test::ScopedKeyValueConfig field_trials;
+  rtc::PhysicalSocketServer socket_server;
+  rtc::AutoSocketServerThread thread(&socket_server);
+  auto socket_factory =
+      std::make_unique<rtc::BasicPacketSocketFactory>(&socket_server);
+  std::unique_ptr<rtc::BasicNetworkManager> network_manager(
+      new rtc::BasicNetworkManager(&socket_server, &field_trials));
+  std::vector<const rtc::Network*> networks = network_manager->GetNetworks();
+  auto prober = std::make_unique<StunProber>(socket_factory.get(),
+                                             rtc::Thread::Current(), networks);
+  auto finish_callback = [&thread](StunProber* prober, int result) {
+    StopTrial(&thread, prober, result);
+  };
+  prober->Start(server_addresses, absl::GetFlag(FLAGS_shared_socket),
+                absl::GetFlag(FLAGS_interval),
+                absl::GetFlag(FLAGS_pings_per_ip), absl::GetFlag(FLAGS_timeout),
+                AsyncCallback(finish_callback));
+  thread.Run();
+  return 0;
+}

p2p/BUILD.gn

@@ -9,7 +9,10 @@
 import("../webrtc.gni")
 
 group("p2p") {
-  deps = [ ":rtc_p2p" ]
+  deps = [
+    ":libstunprober",
+    ":rtc_p2p",
+  ]
 }
 
 rtc_library("rtc_p2p") {
@@ -1255,3 +1258,53 @@ rtc_library("p2p_server_utils") {
     "//third_party/abseil-cpp/absl/strings:string_view",
   ]
 }
+
+rtc_library("libstunprober") {
+  visibility = [ "*" ]
+  sources = [
+    "stunprober/stun_prober.cc",
+    "stunprober/stun_prober.h",
+  ]
+
+  deps = [
+    "../api:array_view",
+    "../api:async_dns_resolver",
+    "../api:packet_socket_factory",
+    "../api:sequence_checker",
+    "../api/task_queue:pending_task_safety_flag",
+    "../api/transport:stun_types",
+    "../api/units:time_delta",
+    "../rtc_base:async_packet_socket",
+    "../rtc_base:byte_buffer",
+    "../rtc_base:checks",
+    "../rtc_base:ip_address",
+    "../rtc_base:logging",
+    "../rtc_base:network",
+    "../rtc_base:socket_address",
+    "../rtc_base:ssl",
+    "../rtc_base:threading",
+    "../rtc_base:timeutils",
+    "../rtc_base/network:received_packet",
+    "../rtc_base/system:rtc_export",
+  ]
+}
+
+if (rtc_include_tests) {
+  rtc_library("libstunprober_unittests") {
+    testonly = true
+
+    sources = [ "stunprober/stun_prober_unittest.cc" ]
+    deps = [
+      ":basic_packet_socket_factory",
+      ":libstunprober",
+      ":p2p_test_utils",
+      "../rtc_base:checks",
+      "../rtc_base:gunit_helpers",
+      "../rtc_base:ip_address",
+      "../rtc_base:rtc_base_tests_utils",
+      "../rtc_base:ssl_adapter",
+      "../test:test_support",
+      "//testing/gtest",
+    ]
+  }
+}

p2p/stunprober/stun_prober.cc

@@ -0,0 +1,602 @@
+/*
+ *  Copyright 2015 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 "p2p/stunprober/stun_prober.h"
+
+#include <cstdint>
+#include <map>
+#include <memory>
+#include <set>
+#include <string>
+#include <utility>
+
+#include "api/array_view.h"
+#include "api/packet_socket_factory.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "api/transport/stun.h"
+#include "api/units/time_delta.h"
+#include "rtc_base/async_packet_socket.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/network/received_packet.h"
+#include "rtc_base/thread.h"
+#include "rtc_base/time_utils.h"
+
+namespace stunprober {
+
+namespace {
+using ::webrtc::SafeTask;
+using ::webrtc::TimeDelta;
+
+const int THREAD_WAKE_UP_INTERVAL_MS = 5;
+
+template <typename T>
+void IncrementCounterByAddress(std::map<T, int>* counter_per_ip, const T& ip) {
+  counter_per_ip->insert(std::make_pair(ip, 0)).first->second++;
+}
+
+}  // namespace
+
+// A requester tracks the requests and responses from a single socket to many
+// STUN servers
+class StunProber::Requester : public sigslot::has_slots<> {
+ public:
+  // Each Request maps to a request and response.
+  struct Request {
+    // Actual time the STUN bind request was sent.
+    int64_t sent_time_ms = 0;
+    // Time the response was received.
+    int64_t received_time_ms = 0;
+
+    // Server reflexive address from STUN response for this given request.
+    rtc::SocketAddress srflx_addr;
+
+    rtc::IPAddress server_addr;
+
+    int64_t rtt() { return received_time_ms - sent_time_ms; }
+    void ProcessResponse(rtc::ArrayView<const uint8_t> payload);
+  };
+
+  // StunProber provides `server_ips` for Requester to probe. For shared
+  // socket mode, it'll be all the resolved IP addresses. For non-shared mode,
+  // it'll just be a single address.
+  Requester(StunProber* prober,
+            rtc::AsyncPacketSocket* socket,
+            const std::vector<rtc::SocketAddress>& server_ips);
+  ~Requester() override;
+
+  Requester(const Requester&) = delete;
+  Requester& operator=(const Requester&) = delete;
+
+  // There is no callback for SendStunRequest as the underneath socket send is
+  // expected to be completed immediately. Otherwise, it'll skip this request
+  // and move to the next one.
+  void SendStunRequest();
+
+  void OnStunResponseReceived(rtc::AsyncPacketSocket* socket,
+                              const rtc::ReceivedPacket& packet);
+
+  const std::vector<Request*>& requests() { return requests_; }
+
+  // Whether this Requester has completed all requests.
+  bool Done() {
+    return static_cast<size_t>(num_request_sent_) == server_ips_.size();
+  }
+
+ private:
+  Request* GetRequestByAddress(const rtc::IPAddress& ip);
+
+  StunProber* prober_;
+
+  // The socket for this session.
+  std::unique_ptr<rtc::AsyncPacketSocket> socket_;
+
+  // Temporary SocketAddress and buffer for RecvFrom.
+  rtc::SocketAddress addr_;
+  std::unique_ptr<rtc::ByteBufferWriter> response_packet_;
+
+  std::vector<Request*> requests_;
+  std::vector<rtc::SocketAddress> server_ips_;
+  int16_t num_request_sent_ = 0;
+  int16_t num_response_received_ = 0;
+
+  webrtc::SequenceChecker& thread_checker_;
+};
+
+StunProber::Requester::Requester(
+    StunProber* prober,
+    rtc::AsyncPacketSocket* socket,
+    const std::vector<rtc::SocketAddress>& server_ips)
+    : prober_(prober),
+      socket_(socket),
+      response_packet_(new rtc::ByteBufferWriter(nullptr, kMaxUdpBufferSize)),
+      server_ips_(server_ips),
+      thread_checker_(prober->thread_checker_) {
+  socket_->RegisterReceivedPacketCallback(
+      [&](rtc::AsyncPacketSocket* socket, const rtc::ReceivedPacket& packet) {
+        OnStunResponseReceived(socket, packet);
+      });
+}
+
+StunProber::Requester::~Requester() {
+  if (socket_) {
+    socket_->Close();
+  }
+  for (auto* req : requests_) {
+    if (req) {
+      delete req;
+    }
+  }
+}
+
+void StunProber::Requester::SendStunRequest() {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  requests_.push_back(new Request());
+  Request& request = *(requests_.back());
+  // Random transaction ID, STUN_BINDING_REQUEST
+  cricket::StunMessage message(cricket::STUN_BINDING_REQUEST);
+
+  std::unique_ptr<rtc::ByteBufferWriter> request_packet(
+      new rtc::ByteBufferWriter(nullptr, kMaxUdpBufferSize));
+  if (!message.Write(request_packet.get())) {
+    prober_->ReportOnFinished(WRITE_FAILED);
+    return;
+  }
+
+  auto addr = server_ips_[num_request_sent_];
+  request.server_addr = addr.ipaddr();
+
+  // The write must succeed immediately. Otherwise, the calculating of the STUN
+  // request timing could become too complicated. Callback is ignored by passing
+  // empty AsyncCallback.
+  rtc::PacketOptions options;
+  int rv = socket_->SendTo(request_packet->Data(), request_packet->Length(),
+                           addr, options);
+  if (rv < 0) {
+    prober_->ReportOnFinished(WRITE_FAILED);
+    return;
+  }
+
+  request.sent_time_ms = rtc::TimeMillis();
+
+  num_request_sent_++;
+  RTC_DCHECK(static_cast<size_t>(num_request_sent_) <= server_ips_.size());
+}
+
+void StunProber::Requester::Request::ProcessResponse(
+    rtc::ArrayView<const uint8_t> payload) {
+  int64_t now = rtc::TimeMillis();
+  rtc::ByteBufferReader message(payload);
+  cricket::StunMessage stun_response;
+  if (!stun_response.Read(&message)) {
+    // Invalid or incomplete STUN packet.
+    received_time_ms = 0;
+    return;
+  }
+
+  // Get external address of the socket.
+  const cricket::StunAddressAttribute* addr_attr =
+      stun_response.GetAddress(cricket::STUN_ATTR_MAPPED_ADDRESS);
+  if (addr_attr == nullptr) {
+    // Addresses not available to detect whether or not behind a NAT.
+    return;
+  }
+
+  if (addr_attr->family() != cricket::STUN_ADDRESS_IPV4 &&
+      addr_attr->family() != cricket::STUN_ADDRESS_IPV6) {
+    return;
+  }
+
+  received_time_ms = now;
+
+  srflx_addr = addr_attr->GetAddress();
+}
+
+void StunProber::Requester::OnStunResponseReceived(
+    rtc::AsyncPacketSocket* socket,
+    const rtc::ReceivedPacket& packet) {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  RTC_DCHECK(socket_);
+  Request* request = GetRequestByAddress(packet.source_address().ipaddr());
+  if (!request) {
+    // Something is wrong, finish the test.
+    prober_->ReportOnFinished(GENERIC_FAILURE);
+    return;
+  }
+
+  num_response_received_++;
+  request->ProcessResponse(packet.payload());
+}
+
+StunProber::Requester::Request* StunProber::Requester::GetRequestByAddress(
+    const rtc::IPAddress& ipaddr) {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  for (auto* request : requests_) {
+    if (request->server_addr == ipaddr) {
+      return request;
+    }
+  }
+
+  return nullptr;
+}
+
+StunProber::Stats::Stats() = default;
+
+StunProber::Stats::~Stats() = default;
+
+StunProber::ObserverAdapter::ObserverAdapter() = default;
+
+StunProber::ObserverAdapter::~ObserverAdapter() = default;
+
+void StunProber::ObserverAdapter::OnPrepared(StunProber* stunprober,
+                                             Status status) {
+  if (status == SUCCESS) {
+    stunprober->Start(this);
+  } else {
+    callback_(stunprober, status);
+  }
+}
+
+void StunProber::ObserverAdapter::OnFinished(StunProber* stunprober,
+                                             Status status) {
+  callback_(stunprober, status);
+}
+
+StunProber::StunProber(rtc::PacketSocketFactory* socket_factory,
+                       rtc::Thread* thread,
+                       std::vector<const rtc::Network*> networks)
+    : interval_ms_(0),
+      socket_factory_(socket_factory),
+      thread_(thread),
+      networks_(std::move(networks)) {}
+
+StunProber::~StunProber() {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  for (auto* req : requesters_) {
+    if (req) {
+      delete req;
+    }
+  }
+  for (auto* s : sockets_) {
+    if (s) {
+      delete s;
+    }
+  }
+}
+
+bool StunProber::Start(const std::vector<rtc::SocketAddress>& servers,
+                       bool shared_socket_mode,
+                       int interval_ms,
+                       int num_request_per_ip,
+                       int timeout_ms,
+                       const AsyncCallback callback) {
+  observer_adapter_.set_callback(callback);
+  return Prepare(servers, shared_socket_mode, interval_ms, num_request_per_ip,
+                 timeout_ms, &observer_adapter_);
+}
+
+bool StunProber::Prepare(const std::vector<rtc::SocketAddress>& servers,
+                         bool shared_socket_mode,
+                         int interval_ms,
+                         int num_request_per_ip,
+                         int timeout_ms,
+                         StunProber::Observer* observer) {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  interval_ms_ = interval_ms;
+  shared_socket_mode_ = shared_socket_mode;
+
+  requests_per_ip_ = num_request_per_ip;
+  if (requests_per_ip_ == 0 || servers.size() == 0) {
+    return false;
+  }
+
+  timeout_ms_ = timeout_ms;
+  servers_ = servers;
+  observer_ = observer;
+  // Remove addresses that are already resolved.
+  for (auto it = servers_.begin(); it != servers_.end();) {
+    if (it->ipaddr().family() != AF_UNSPEC) {
+      all_servers_addrs_.push_back(*it);
+      it = servers_.erase(it);
+    } else {
+      ++it;
+    }
+  }
+  if (servers_.empty()) {
+    CreateSockets();
+    return true;
+  }
+  return ResolveServerName(servers_.back());
+}
+
+bool StunProber::Start(StunProber::Observer* observer) {
+  observer_ = observer;
+  if (total_ready_sockets_ != total_socket_required()) {
+    return false;
+  }
+  MaybeScheduleStunRequests();
+  return true;
+}
+
+bool StunProber::ResolveServerName(const rtc::SocketAddress& addr) {
+  RTC_DCHECK(!resolver_);
+  resolver_ = socket_factory_->CreateAsyncDnsResolver();
+  if (!resolver_) {
+    return false;
+  }
+  resolver_->Start(addr, [this] { OnServerResolved(resolver_->result()); });
+  return true;
+}
+
+void StunProber::OnSocketReady(rtc::AsyncPacketSocket* socket,
+                               const rtc::SocketAddress& addr) {
+  total_ready_sockets_++;
+  if (total_ready_sockets_ == total_socket_required()) {
+    ReportOnPrepared(SUCCESS);
+  }
+}
+
+void StunProber::OnServerResolved(
+    const webrtc::AsyncDnsResolverResult& result) {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  rtc::SocketAddress received_address;
+  if (result.GetResolvedAddress(AF_INET, &received_address)) {
+    // Construct an address without the name in it.
+    rtc::SocketAddress addr(received_address.ipaddr(), received_address.port());
+    all_servers_addrs_.push_back(addr);
+  }
+  resolver_.reset();
+  servers_.pop_back();
+  if (servers_.size()) {
+    if (!ResolveServerName(servers_.back())) {
+      ReportOnPrepared(RESOLVE_FAILED);
+    }
+    return;
+  }
+
+  if (all_servers_addrs_.size() == 0) {
+    ReportOnPrepared(RESOLVE_FAILED);
+    return;
+  }
+
+  CreateSockets();
+}
+
+void StunProber::CreateSockets() {
+  // Dedupe.
+  std::set<rtc::SocketAddress> addrs(all_servers_addrs_.begin(),
+                                     all_servers_addrs_.end());
+  all_servers_addrs_.assign(addrs.begin(), addrs.end());
+
+  // Prepare all the sockets beforehand. All of them will bind to "any" address.
+  while (sockets_.size() < total_socket_required()) {
+    std::unique_ptr<rtc::AsyncPacketSocket> socket(
+        socket_factory_->CreateUdpSocket(rtc::SocketAddress(INADDR_ANY, 0), 0,
+                                         0));
+    if (!socket) {
+      ReportOnPrepared(GENERIC_FAILURE);
+      return;
+    }
+    // Chrome and WebRTC behave differently in terms of the state of a socket
+    // once returned from PacketSocketFactory::CreateUdpSocket.
+    if (socket->GetState() == rtc::AsyncPacketSocket::STATE_BINDING) {
+      socket->SignalAddressReady.connect(this, &StunProber::OnSocketReady);
+    } else {
+      OnSocketReady(socket.get(), rtc::SocketAddress(INADDR_ANY, 0));
+    }
+    sockets_.push_back(socket.release());
+  }
+}
+
+StunProber::Requester* StunProber::CreateRequester() {
+  RTC_DCHECK(thread_checker_.IsCurrent());
+  if (!sockets_.size()) {
+    return nullptr;
+  }
+  StunProber::Requester* requester;
+  if (shared_socket_mode_) {
+    requester = new Requester(this, sockets_.back(), all_servers_addrs_);
+  } else {
+    std::vector<rtc::SocketAddress> server_ip;
+    server_ip.push_back(
+        all_servers_addrs_[(num_request_sent_ % all_servers_addrs_.size())]);
+    requester = new Requester(this, sockets_.back(), server_ip);
+  }
+
+  sockets_.pop_back();
+  return requester;
+}
+
+bool StunProber::SendNextRequest() {
+  if (!current_requester_ || current_requester_->Done()) {
+    current_requester_ = CreateRequester();
+    requesters_.push_back(current_requester_);
+  }
+  if (!current_requester_) {
+    return false;
+  }
+  current_requester_->SendStunRequest();
+  num_request_sent_++;
+  return true;
+}
+
+bool StunProber::should_send_next_request(int64_t now) {
+  if (interval_ms_ < THREAD_WAKE_UP_INTERVAL_MS) {
+    return now >= next_request_time_ms_;
+  } else {
+    return (now + (THREAD_WAKE_UP_INTERVAL_MS / 2)) >= next_request_time_ms_;
+  }
+}
+
+int StunProber::get_wake_up_interval_ms() {
+  if (interval_ms_ < THREAD_WAKE_UP_INTERVAL_MS) {
+    return 1;
+  } else {
+    return THREAD_WAKE_UP_INTERVAL_MS;
+  }
+}
+
+void StunProber::MaybeScheduleStunRequests() {
+  RTC_DCHECK_RUN_ON(thread_);
+  int64_t now = rtc::TimeMillis();
+
+  if (Done()) {
+    thread_->PostDelayedTask(
+        SafeTask(task_safety_.flag(), [this] { ReportOnFinished(SUCCESS); }),
+        TimeDelta::Millis(timeout_ms_));
+    return;
+  }
+  if (should_send_next_request(now)) {
+    if (!SendNextRequest()) {
+      ReportOnFinished(GENERIC_FAILURE);
+      return;
+    }
+    next_request_time_ms_ = now + interval_ms_;
+  }
+  thread_->PostDelayedTask(
+      SafeTask(task_safety_.flag(), [this] { MaybeScheduleStunRequests(); }),
+      TimeDelta::Millis(get_wake_up_interval_ms()));
+}
+
+bool StunProber::GetStats(StunProber::Stats* prob_stats) const {
+  // No need to be on the same thread.
+  if (!prob_stats) {
+    return false;
+  }
+
+  StunProber::Stats stats;
+
+  int rtt_sum = 0;
+  int64_t first_sent_time = 0;
+  int64_t last_sent_time = 0;
+  NatType nat_type = NATTYPE_INVALID;
+
+  // Track of how many srflx IP that we have seen.
+  std::set<rtc::IPAddress> srflx_ips;
+
+  // If we're not receiving any response on a given IP, all requests sent to
+  // that IP should be ignored as this could just be an DNS error.
+  std::map<rtc::IPAddress, int> num_response_per_server;
+  std::map<rtc::IPAddress, int> num_request_per_server;
+
+  for (auto* requester : requesters_) {
+    std::map<rtc::SocketAddress, int> num_response_per_srflx_addr;
+    for (auto* request : requester->requests()) {
+      if (request->sent_time_ms <= 0) {
+        continue;
+      }
+
+      ++stats.raw_num_request_sent;
+      IncrementCounterByAddress(&num_request_per_server, request->server_addr);
+
+      if (!first_sent_time) {
+        first_sent_time = request->sent_time_ms;
+      }
+      last_sent_time = request->sent_time_ms;
+
+      if (request->received_time_ms < request->sent_time_ms) {
+        continue;
+      }
+
+      IncrementCounterByAddress(&num_response_per_server, request->server_addr);
+      IncrementCounterByAddress(&num_response_per_srflx_addr,
+                                request->srflx_addr);
+      rtt_sum += request->rtt();
+      stats.srflx_addrs.insert(request->srflx_addr.ToString());
+      srflx_ips.insert(request->srflx_addr.ipaddr());
+    }
+
+    // If we're using shared mode and seeing >1 srflx addresses for a single
+    // requester, it's symmetric NAT.
+    if (shared_socket_mode_ && num_response_per_srflx_addr.size() > 1) {
+      nat_type = NATTYPE_SYMMETRIC;
+    }
+  }
+
+  // We're probably not behind a regular NAT. We have more than 1 distinct
+  // server reflexive IPs.
+  if (srflx_ips.size() > 1) {
+    return false;
+  }
+
+  int num_sent = 0;
+  int num_received = 0;
+  int num_server_ip_with_response = 0;
+
+  for (const auto& kv : num_response_per_server) {
+    RTC_DCHECK_GT(kv.second, 0);
+    num_server_ip_with_response++;
+    num_received += kv.second;
+    num_sent += num_request_per_server[kv.first];
+  }
+
+  // Shared mode is only true if we use the shared socket and there are more
+  // than 1 responding servers.
+  stats.shared_socket_mode =
+      shared_socket_mode_ && (num_server_ip_with_response > 1);
+
+  if (stats.shared_socket_mode && nat_type == NATTYPE_INVALID) {
+    nat_type = NATTYPE_NON_SYMMETRIC;
+  }
+
+  // If we could find a local IP matching srflx, we're not behind a NAT.
+  rtc::SocketAddress srflx_addr;
+  if (stats.srflx_addrs.size() &&
+      !srflx_addr.FromString(*(stats.srflx_addrs.begin()))) {
+    return false;
+  }
+  for (const auto* net : networks_) {
+    if (srflx_addr.ipaddr() == net->GetBestIP()) {
+      nat_type = stunprober::NATTYPE_NONE;
+      stats.host_ip = net->GetBestIP().ToString();
+      break;
+    }
+  }
+
+  // Finally, we know we're behind a NAT but can't determine which type it is.
+  if (nat_type == NATTYPE_INVALID) {
+    nat_type = NATTYPE_UNKNOWN;
+  }
+
+  stats.nat_type = nat_type;
+  stats.num_request_sent = num_sent;
+  stats.num_response_received = num_received;
+  stats.target_request_interval_ns = interval_ms_ * 1000;
+
+  if (num_sent) {
+    stats.success_percent = static_cast<int>(100 * num_received / num_sent);
+  }
+
+  if (stats.raw_num_request_sent > 1) {
+    stats.actual_request_interval_ns =
+        (1000 * (last_sent_time - first_sent_time)) /
+        (stats.raw_num_request_sent - 1);
+  }
+
+  if (num_received) {
+    stats.average_rtt_ms = static_cast<int>((rtt_sum / num_received));
+  }
+
+  *prob_stats = stats;
+  return true;
+}
+
+void StunProber::ReportOnPrepared(StunProber::Status status) {
+  if (observer_) {
+    observer_->OnPrepared(this, status);
+  }
+}
+
+void StunProber::ReportOnFinished(StunProber::Status status) {
+  if (observer_) {
+    observer_->OnFinished(this, status);
+  }
+}
+
+}  // namespace stunprober

p2p/stunprober/stun_prober.h

@@ -0,0 +1,251 @@
+/*
+ *  Copyright 2015 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.
+ */
+
+#ifndef P2P_STUNPROBER_STUN_PROBER_H_
+#define P2P_STUNPROBER_STUN_PROBER_H_
+
+#include <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "api/async_dns_resolver.h"
+#include "api/sequence_checker.h"
+#include "api/task_queue/pending_task_safety_flag.h"
+#include "rtc_base/network.h"
+#include "rtc_base/socket_address.h"
+#include "rtc_base/system/rtc_export.h"
+#include "rtc_base/thread.h"
+
+namespace rtc {
+class AsyncPacketSocket;
+class PacketSocketFactory;
+class Thread;
+class NetworkManager;
+class AsyncResolverInterface;
+}  // namespace rtc
+
+namespace stunprober {
+
+class StunProber;
+
+static const int kMaxUdpBufferSize = 1200;
+
+typedef std::function<void(StunProber*, int)> AsyncCallback;
+
+enum NatType {
+  NATTYPE_INVALID,
+  NATTYPE_NONE,          // Not behind a NAT.
+  NATTYPE_UNKNOWN,       // Behind a NAT but type can't be determine.
+  NATTYPE_SYMMETRIC,     // Behind a symmetric NAT.
+  NATTYPE_NON_SYMMETRIC  // Behind a non-symmetric NAT.
+};
+
+class RTC_EXPORT StunProber : public sigslot::has_slots<> {
+ public:
+  enum Status {       // Used in UMA_HISTOGRAM_ENUMERATION.
+    SUCCESS,          // Successfully received bytes from the server.
+    GENERIC_FAILURE,  // Generic failure.
+    RESOLVE_FAILED,   // Host resolution failed.
+    WRITE_FAILED,     // Sending a message to the server failed.
+    READ_FAILED,      // Reading the reply from the server failed.
+  };
+
+  class Observer {
+   public:
+    virtual ~Observer() = default;
+    virtual void OnPrepared(StunProber* prober, StunProber::Status status) = 0;
+    virtual void OnFinished(StunProber* prober, StunProber::Status status) = 0;
+  };
+
+  struct RTC_EXPORT Stats {
+    Stats();
+    ~Stats();
+
+    // `raw_num_request_sent` is the total number of requests
+    // sent. `num_request_sent` is the count of requests against a server where
+    // we see at least one response. `num_request_sent` is designed to protect
+    // against DNS resolution failure or the STUN server is not responsive
+    // which could skew the result.
+    int raw_num_request_sent = 0;
+    int num_request_sent = 0;
+
+    int num_response_received = 0;
+    NatType nat_type = NATTYPE_INVALID;
+    int average_rtt_ms = -1;
+    int success_percent = 0;
+    int target_request_interval_ns = 0;
+    int actual_request_interval_ns = 0;
+
+    // Also report whether this trial can't be considered truly as shared
+    // mode. Share mode only makes sense when we have multiple IP resolved and
+    // successfully probed.
+    bool shared_socket_mode = false;
+
+    std::string host_ip;
+
+    // If the srflx_addrs has more than 1 element, the NAT is symmetric.
+    std::set<std::string> srflx_addrs;
+  };
+
+  StunProber(rtc::PacketSocketFactory* socket_factory,
+             rtc::Thread* thread,
+             std::vector<const rtc::Network*> networks);
+  ~StunProber() override;
+
+  StunProber(const StunProber&) = delete;
+  StunProber& operator=(const StunProber&) = delete;
+
+  // Begin performing the probe test against the `servers`. If
+  // `shared_socket_mode` is false, each request will be done with a new socket.
+  // Otherwise, a unique socket will be used for a single round of requests
+  // against all resolved IPs. No single socket will be used against a given IP
+  // more than once.  The interval of requests will be as close to the requested
+  // inter-probe interval `stun_ta_interval_ms` as possible. After sending out
+  // the last scheduled request, the probe will wait `timeout_ms` for request
+  // responses and then call `finish_callback`.  `requests_per_ip` indicates how
+  // many requests should be tried for each resolved IP address. In shared mode,
+  // (the number of sockets to be created) equals to `requests_per_ip`. In
+  // non-shared mode, (the number of sockets) equals to requests_per_ip * (the
+  // number of resolved IP addresses). TODO(guoweis): Remove this once
+  // everything moved to Prepare() and Run().
+  bool Start(const std::vector<rtc::SocketAddress>& servers,
+             bool shared_socket_mode,
+             int stun_ta_interval_ms,
+             int requests_per_ip,
+             int timeout_ms,
+             AsyncCallback finish_callback);
+
+  // TODO(guoweis): The combination of Prepare() and Run() are equivalent to the
+  // Start() above. Remove Start() once everything is migrated.
+  bool Prepare(const std::vector<rtc::SocketAddress>& servers,
+               bool shared_socket_mode,
+               int stun_ta_interval_ms,
+               int requests_per_ip,
+               int timeout_ms,
+               StunProber::Observer* observer);
+
+  // Start to send out the STUN probes.
+  bool Start(StunProber::Observer* observer);
+
+  // Method to retrieve the Stats once `finish_callback` is invoked. Returning
+  // false when the result is inconclusive, for example, whether it's behind a
+  // NAT or not.
+  bool GetStats(Stats* stats) const;
+
+  int estimated_execution_time() {
+    return static_cast<int>(requests_per_ip_ * all_servers_addrs_.size() *
+                            interval_ms_);
+  }
+
+ private:
+  // A requester tracks the requests and responses from a single socket to many
+  // STUN servers.
+  class Requester;
+
+  // TODO(guoweis): Remove this once all dependencies move away from
+  // AsyncCallback.
+  class ObserverAdapter : public Observer {
+   public:
+    ObserverAdapter();
+    ~ObserverAdapter() override;
+
+    void set_callback(AsyncCallback callback) { callback_ = callback; }
+    void OnPrepared(StunProber* stunprober, Status status) override;
+    void OnFinished(StunProber* stunprober, Status status) override;
+
+   private:
+    AsyncCallback callback_;
+  };
+
+  bool ResolveServerName(const rtc::SocketAddress& addr);
+  void OnServerResolved(const webrtc::AsyncDnsResolverResult& resolver);
+
+  void OnSocketReady(rtc::AsyncPacketSocket* socket,
+                     const rtc::SocketAddress& addr);
+
+  void CreateSockets();
+
+  bool Done() {
+    return num_request_sent_ >= requests_per_ip_ * all_servers_addrs_.size();
+  }
+
+  size_t total_socket_required() {
+    return (shared_socket_mode_ ? 1 : all_servers_addrs_.size()) *
+           requests_per_ip_;
+  }
+
+  bool should_send_next_request(int64_t now);
+  int get_wake_up_interval_ms();
+
+  bool SendNextRequest();
+
+  // Will be invoked in 1ms intervals and schedule the next request from the
+  // `current_requester_` if the time has passed for another request.
+  void MaybeScheduleStunRequests();
+
+  void ReportOnPrepared(StunProber::Status status);
+  void ReportOnFinished(StunProber::Status status);
+
+  Requester* CreateRequester();
+
+  Requester* current_requester_ = nullptr;
+
+  // The time when the next request should go out.
+  int64_t next_request_time_ms_ = 0;
+
+  // Total requests sent so far.
+  uint32_t num_request_sent_ = 0;
+
+  bool shared_socket_mode_ = false;
+
+  // How many requests should be done against each resolved IP.
+  uint32_t requests_per_ip_ = 0;
+
+  // Milliseconds to pause between each STUN request.
+  int interval_ms_;
+
+  // Timeout period after the last request is sent.
+  int timeout_ms_;
+
+  // STUN server name to be resolved.
+  std::vector<rtc::SocketAddress> servers_;
+
+  // Weak references.
+  rtc::PacketSocketFactory* socket_factory_;
+  rtc::Thread* thread_;
+
+  // Accumulate all resolved addresses.
+  std::vector<rtc::SocketAddress> all_servers_addrs_;
+
+  // The set of STUN probe sockets and their state.
+  std::vector<Requester*> requesters_;
+
+  webrtc::SequenceChecker thread_checker_;
+
+  // Temporary storage for created sockets.
+  std::vector<rtc::AsyncPacketSocket*> sockets_;
+  // This tracks how many of the sockets are ready.
+  size_t total_ready_sockets_ = 0;
+
+  Observer* observer_ = nullptr;
+  // TODO(guoweis): Remove this once all dependencies move away from
+  // AsyncCallback.
+  ObserverAdapter observer_adapter_;
+
+  const std::vector<const rtc::Network*> networks_;
+  std::unique_ptr<webrtc::AsyncDnsResolverInterface> resolver_;
+
+  webrtc::ScopedTaskSafety task_safety_;
+};
+
+}  // namespace stunprober
+
+#endif  // P2P_STUNPROBER_STUN_PROBER_H_

p2p/stunprober/stun_prober_unittest.cc

@@ -0,0 +1,177 @@
+/*
+ *  Copyright 2015 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 "p2p/stunprober/stun_prober.h"
+
+#include <stdint.h>
+
+#include <memory>
+#include <utility>
+
+#include "p2p/base/basic_packet_socket_factory.h"
+#include "p2p/base/test_stun_server.h"
+#include "rtc_base/gunit.h"
+#include "rtc_base/ip_address.h"
+#include "rtc_base/ssl_adapter.h"
+#include "rtc_base/virtual_socket_server.h"
+#include "test/gtest.h"
+
+using stunprober::AsyncCallback;
+using stunprober::StunProber;
+
+namespace stunprober {
+
+namespace {
+
+const rtc::SocketAddress kLocalAddr("192.168.0.1", 0);
+const rtc::SocketAddress kStunAddr1("1.1.1.1", 3478);
+const rtc::SocketAddress kStunAddr2("1.1.1.2", 3478);
+const rtc::SocketAddress kFailedStunAddr("1.1.1.3", 3478);
+const rtc::SocketAddress kStunMappedAddr("77.77.77.77", 0);
+
+}  // namespace
+
+class StunProberTest : public ::testing::Test {
+ public:
+  StunProberTest()
+      : ss_(std::make_unique<rtc::VirtualSocketServer>()),
+        main_(ss_.get()),
+        result_(StunProber::SUCCESS),
+        stun_server_1_(
+            cricket::TestStunServer::Create(ss_.get(), kStunAddr1, main_)),
+        stun_server_2_(
+            cricket::TestStunServer::Create(ss_.get(), kStunAddr2, main_)) {
+    stun_server_1_->set_fake_stun_addr(kStunMappedAddr);
+    stun_server_2_->set_fake_stun_addr(kStunMappedAddr);
+    rtc::InitializeSSL();
+  }
+
+  static constexpr int pings_per_ip = 3;
+
+  void set_expected_result(int result) { result_ = result; }
+
+  void CreateProber(rtc::PacketSocketFactory* socket_factory,
+                    std::vector<const rtc::Network*> networks) {
+    prober_ = std::make_unique<StunProber>(socket_factory, &main_,
+                                           std::move(networks));
+  }
+
+  void StartProbing(rtc::PacketSocketFactory* socket_factory,
+                    const std::vector<rtc::SocketAddress>& addrs,
+                    std::vector<const rtc::Network*> networks,
+                    bool shared_socket,
+                    uint16_t interval,
+                    uint16_t pings_per_ip) {
+    CreateProber(socket_factory, networks);
+    prober_->Start(addrs, shared_socket, interval, pings_per_ip,
+                   100 /* timeout_ms */,
+                   [this](StunProber* prober, int result) {
+                     StopCallback(prober, result);
+                   });
+  }
+
+  void RunProber(bool shared_mode) {
+    std::vector<rtc::SocketAddress> addrs;
+    addrs.push_back(kStunAddr1);
+    addrs.push_back(kStunAddr2);
+    // Add a non-existing server. This shouldn't pollute the result.
+    addrs.push_back(kFailedStunAddr);
+    RunProber(shared_mode, addrs, /* check_results= */ true);
+  }
+
+  void RunProber(bool shared_mode,
+                 const std::vector<rtc::SocketAddress>& addrs,
+                 bool check_results) {
+    rtc::Network ipv4_network1("test_eth0", "Test Network Adapter 1",
+                               rtc::IPAddress(0x12345600U), 24);
+    ipv4_network1.AddIP(rtc::IPAddress(0x12345678));
+    std::vector<const rtc::Network*> networks;
+    networks.push_back(&ipv4_network1);
+
+    auto socket_factory =
+        std::make_unique<rtc::BasicPacketSocketFactory>(ss_.get());
+
+    // Set up the expected results for verification.
+    std::set<std::string> srflx_addresses;
+    srflx_addresses.insert(kStunMappedAddr.ToString());
+    const uint32_t total_pings_tried =
+        static_cast<uint32_t>(pings_per_ip * addrs.size());
+
+    // The reported total_pings should not count for pings sent to the
+    // kFailedStunAddr.
+    const uint32_t total_pings_reported = total_pings_tried - pings_per_ip;
+
+    StartProbing(socket_factory.get(), addrs, std::move(networks), shared_mode,
+                 3, pings_per_ip);
+
+    WAIT(stopped_, 1000);
+
+    EXPECT_TRUE(prober_->GetStats(&stats_));
+    if (check_results) {
+      EXPECT_EQ(stats_.success_percent, 100);
+      EXPECT_TRUE(stats_.nat_type > stunprober::NATTYPE_NONE);
+      EXPECT_EQ(stats_.srflx_addrs, srflx_addresses);
+      EXPECT_EQ(static_cast<uint32_t>(stats_.num_request_sent),
+                total_pings_reported);
+      EXPECT_EQ(static_cast<uint32_t>(stats_.num_response_received),
+                total_pings_reported);
+    }
+  }
+
+  StunProber* prober() { return prober_.get(); }
+  StunProber::Stats& stats() { return stats_; }
+
+ private:
+  void StopCallback(StunProber* prober, int result) {
+    EXPECT_EQ(result, result_);
+    stopped_ = true;
+  }
+
+  std::unique_ptr<rtc::VirtualSocketServer> ss_;
+  rtc::AutoSocketServerThread main_;
+  std::unique_ptr<StunProber> prober_;
+  int result_ = 0;
+  bool stopped_ = false;
+  cricket::TestStunServer::StunServerPtr stun_server_1_;
+  cricket::TestStunServer::StunServerPtr stun_server_2_;
+  StunProber::Stats stats_;
+};
+
+TEST_F(StunProberTest, NonSharedMode) {
+  RunProber(false);
+}
+
+TEST_F(StunProberTest, SharedMode) {
+  RunProber(true);
+}
+
+TEST_F(StunProberTest, ResolveNonexistentHostname) {
+  std::vector<rtc::SocketAddress> addrs;
+  addrs.push_back(kStunAddr1);
+  // Add a non-existing server by name. This should cause a failed lookup.
+  addrs.push_back(rtc::SocketAddress("nonexistent.test", 3478));
+  RunProber(false, addrs, false);
+  // One server is pinged
+  EXPECT_EQ(stats().raw_num_request_sent, pings_per_ip);
+}
+
+TEST_F(StunProberTest, ResolveExistingHostname) {
+  std::vector<rtc::SocketAddress> addrs;
+  addrs.push_back(kStunAddr1);
+  // Add a non-existing server by name. This should cause a failed lookup.
+  addrs.push_back(rtc::SocketAddress("localhost", 3478));
+  RunProber(false, addrs, false);
+  // Two servers are pinged, only one responds.
+  // TODO(bugs.webrtc.org/15559): Figure out why this doesn't always work
+  // EXPECT_EQ(stats().raw_num_request_sent, pings_per_ip * 2);
+  EXPECT_EQ(stats().num_request_sent, pings_per_ip);
+}
+
+}  // namespace stunprober