refactor: local peer discovery (#3696)

CMakeLists.txt

@@ -20,6 +20,7 @@ include(CheckIncludeFile)
 include(CheckIncludeFiles)
 include(CheckFunctionExists)
 include(CheckLibraryExists)
+include(CheckSymbolExists)
 include(ExternalProject)
 include(GNUInstallDirs)
 include(TrMacros)
@@ -611,6 +612,8 @@ if(HAVE_LIBM)
     set(LIBM_LIBRARY m)
 endif()
 
+check_symbol_exists(SO_REUSEPORT "sys/types.h;sys/socket.h" HAVE_SO_REUSEPORT)
+
 set(TR_NETWORK_LIBRARIES)
 if(WIN32)
     list(APPEND TR_NETWORK_LIBRARIES iphlpapi ws2_32)

libtransmission/.clang-tidy

@@ -12,6 +12,7 @@ Checks: >
   clang-analyzer-core.*,
   clang-analyzer-cplusplus.*,
   clang-analyzer-deadcode.*,
+  clang-analyzer-nullability.*,
   clang-analyzer-optin.cplusplus.*,
   clang-analyzer-security.*,
   clang-analyzer-valist.*,
@@ -28,6 +29,7 @@ Checks: >
   -modernize-avoid-c-arrays,
   -modernize-use-trailing-return-type,
   performance-*,
+  portability-*,
   readability-*,
   -readability-function-cognitive-complexity,
   -readability-identifier-length,

libtransmission/CMakeLists.txt

@@ -254,6 +254,10 @@ if(POLARSSL_IS_MBEDTLS)
     add_definitions(-DPOLARSSL_IS_MBEDTLS)
 endif()
 
+if(HAVE_SO_REUSEPORT)
+    add_definitions(-DHAVE_SO_REUSEPORT=1)
+endif()
+
 include_directories(
     ${PROJECT_SOURCE_DIR}
     ${PROJECT_BINARY_DIR}

libtransmission/crypto-utils.h

@@ -137,7 +137,7 @@ std::string tr_base64_decode(std::string_view input);
 std::string tr_sha1_to_string(tr_sha1_digest_t const&);
 
 /**
- * @brief Generate a sha256 digest from a hex string.
+ * @brief Generate a sha1 digest from a hex string.
  */
 std::optional<tr_sha1_digest_t> tr_sha1_from_string(std::string_view hex);
 

libtransmission/session.cc

@@ -128,6 +128,58 @@ tr_peer_id_t tr_peerIdInit()
 ****
 ***/
 
+bool tr_session::LpdMediator::onPeerFound(std::string_view info_hash_str, tr_address address, tr_port port)
+{
+    auto const digest = tr_sha1_from_string(info_hash_str);
+    if (!digest)
+    {
+        return false;
+    }
+
+    tr_torrent* const tor = session_.torrents_.get(*digest);
+    if (!tr_isTorrent(tor) || !tor->allowsLpd())
+    {
+        return false;
+    }
+
+    // we found a suitable peer, add it to the torrent
+    auto pex = tr_pex{ address, port };
+    tr_peerMgrAddPex(tor, TR_PEER_FROM_LPD, &pex, 1U);
+    tr_logAddDebugTor(tor, fmt::format(FMT_STRING("Found a local peer from LPD ({:s})"), address.readable(port)));
+    return true;
+}
+
+std::vector<tr_lpd::Mediator::TorrentInfo> tr_session::LpdMediator::torrents() const
+{
+    auto ret = std::vector<tr_lpd::Mediator::TorrentInfo>{};
+    ret.reserve(std::size(session_.torrents()));
+    for (auto const* const tor : session_.torrents())
+    {
+        auto info = tr_lpd::Mediator::TorrentInfo{};
+        info.info_hash_str = tor->infoHashString();
+        info.activity = tr_torrentGetActivity(tor);
+        info.allows_lpd = tor->allowsLpd();
+        info.announce_after = tor->lpdAnnounceAt;
+        ret.emplace_back(info);
+    }
+    return ret;
+}
+
+void tr_session::LpdMediator::setNextAnnounceTime(std::string_view info_hash_str, time_t announce_after)
+{
+    if (auto digest = tr_sha1_from_string(info_hash_str); digest)
+    {
+        if (tr_torrent* const tor = session_.torrents_.get(*digest); tr_isTorrent(tor))
+        {
+            tor->lpdAnnounceAt = announce_after;
+        }
+    }
+}
+
+/***
+****
+***/
+
 std::optional<std::string> tr_session::WebMediator::cookieFile() const
 {
     auto const path = tr_pathbuf{ session_->configDir(), "/cookies.txt"sv };
@@ -700,7 +752,7 @@ void tr_session::initImpl(init_data& data)
 
     if (this->allowsLPD())
     {
-        tr_lpdInit(this, &this->bind_ipv4.addr_);
+        this->lpd_ = tr_lpd::create(lpd_mediator_, timerMaker(), eventBase());
     }
 
     tr_utpInit(this);
@@ -1743,10 +1795,7 @@ void tr_session::closeImplStart()
 {
     is_closing_ = true;
 
-    if (this->allowsLPD())
-    {
-        tr_lpdUninit(this);
-    }
+    lpd_.reset();
 
     tr_dhtUninit(this);
 
@@ -2082,16 +2131,11 @@ void tr_sessionSetLPDEnabled(tr_session* session, bool enabled)
         session,
         [session, enabled]()
         {
-            if (session->allowsLPD())
-            {
-                tr_lpdUninit(session);
-            }
-
+            session->lpd_.reset();
             session->is_lpd_enabled_ = enabled;
-
-            if (session->allowsLPD())
+            if (enabled)
             {
-                tr_lpdInit(session, &session->bind_ipv4.addr_);
+                session->lpd_ = tr_lpd::create(session->lpd_mediator_, session->timerMaker(), session->eventBase());
             }
         });
 }

libtransmission/session.h

@@ -37,6 +37,7 @@
 #include "stats.h"
 #include "timer.h"
 #include "torrents.h"
+#include "tr-lpd.h"
 #include "web.h"
 
 enum tr_auto_switch_state_t
@@ -53,6 +54,7 @@ struct evdns_base;
 
 class tr_rpc_server;
 class tr_web;
+class tr_lpd;
 struct BlocklistFile;
 struct struct_utp_context;
 struct tr_announcer;
@@ -503,6 +505,7 @@ public:
     std::unique_ptr<Cache> cache;
 
     std::unique_ptr<tr_web> web;
+    std::unique_ptr<tr_lpd> lpd_;
 
     struct tr_announcer* announcer = nullptr;
     struct tr_announcer_udp* announcer_udp = nullptr;
@@ -839,6 +842,37 @@ private:
 
     WebMediator web_mediator_{ this };
 
+    class LpdMediator final : public tr_lpd::Mediator
+    {
+    public:
+        explicit LpdMediator(tr_session& session)
+            : session_{ session }
+        {
+        }
+        ~LpdMediator() override = default;
+
+        [[nodiscard]] tr_port port() const override
+        {
+            return session_.peerPort();
+        }
+
+        [[nodiscard]] bool allowsLPD() const override
+        {
+            return session_.allowsLPD();
+        }
+
+        [[nodiscard]] std::vector<TorrentInfo> torrents() const override;
+
+        bool onPeerFound(std::string_view info_hash_str, tr_address address, tr_port port) override;
+
+        void setNextAnnounceTime(std::string_view info_hash_str, time_t announce_after) override;
+
+    private:
+        tr_session& session_;
+    };
+
+    LpdMediator lpd_mediator_{ *this };
+
     std::shared_ptr<event_base> const event_base_;
     std::shared_ptr<evdns_base> const evdns_base_;
     std::unique_ptr<libtransmission::TimerMaker> const timer_maker_;

libtransmission/stats.cc

@@ -5,6 +5,7 @@
 
 #include "transmission.h"
 
+#include "file.h"
 #include "stats.h"
 #include "tr-strbuf.h"
 #include "utils.h" // for tr_getRatio(), tr_time()
@@ -18,14 +19,14 @@ tr_session_stats tr_stats::loadOldStats(std::string_view config_dir)
 
     auto top = tr_variant{};
     auto filename = tr_pathbuf{ config_dir, "/stats.json"sv };
-    bool loaded = tr_variantFromFile(&top, TR_VARIANT_PARSE_JSON, filename.sv(), nullptr);
+    bool loaded = tr_sys_path_exists(filename) && tr_variantFromFile(&top, TR_VARIANT_PARSE_JSON, filename.sv(), nullptr);
 
     if (!loaded)
     {
         // maybe the user just upgraded from an old version of Transmission
         // that was still using stats.benc
         filename.assign(config_dir, "/stats.benc");
-        loaded = tr_variantFromFile(&top, TR_VARIANT_PARSE_BENC, filename.sv(), nullptr);
+        loaded = tr_sys_path_exists(filename) && tr_variantFromFile(&top, TR_VARIANT_PARSE_BENC, filename.sv(), nullptr);
     }
 
     if (loaded)

libtransmission/tr-lpd.h

@@ -8,9 +8,48 @@
 #error only libtransmission should #include this header.
 #endif
 
-int tr_lpdInit(tr_session*, tr_address*);
-void tr_lpdUninit(tr_session*);
-bool tr_lpdSendAnnounce(tr_torrent const*);
+#include <ctime>
+#include <memory>
+#include <string_view>
+#include <vector>
 
-/**
-* @} */
+#include "transmission.h"
+
+#include "net.h" // for tr_address, tr_port
+#include "timer.h"
+
+class tr_torrents;
+struct tr_session;
+struct event_base;
+
+class tr_lpd
+{
+public:
+    class Mediator
+    {
+    public:
+        struct TorrentInfo
+        {
+            std::string_view info_hash_str;
+            tr_torrent_activity activity;
+            bool allows_lpd;
+            time_t announce_after;
+        };
+
+        virtual ~Mediator() = default;
+
+        [[nodiscard]] virtual tr_port port() const = 0;
+
+        [[nodiscard]] virtual bool allowsLPD() const = 0;
+
+        [[nodiscard]] virtual std::vector<TorrentInfo> torrents() const = 0;
+
+        virtual void setNextAnnounceTime(std::string_view info_hash_str, time_t announce_at) = 0;
+
+        // returns true if info was used
+        virtual bool onPeerFound(std::string_view info_hash_str, tr_address address, tr_port port) = 0;
+    };
+
+    virtual ~tr_lpd() = default;
+    static std::unique_ptr<tr_lpd> create(Mediator& mediator, libtransmission::TimerMaker&, event_base* event_base);
+};

libtransmission/utils.cc

@@ -1135,6 +1135,7 @@ template std::optional<char> tr_parseNum(std::string_view& sv, int base);
 template std::optional<unsigned long long> tr_parseNum(std::string_view& sv, int base);
 template std::optional<unsigned long> tr_parseNum(std::string_view& sv, int base);
 template std::optional<unsigned int> tr_parseNum(std::string_view& sv, int base);
+template std::optional<unsigned short> tr_parseNum(std::string_view& sv, int base);
 template std::optional<unsigned char> tr_parseNum(std::string_view& sv, int base);
 
 template<typename T, std::enable_if_t<std::is_floating_point<T>::value, bool>>

tests/libtransmission/CMakeLists.txt

@@ -17,6 +17,7 @@ add_executable(libtransmission-test
     handshake-test.cc
     history-test.cc
     json-test.cc
+    lpd-test.cc
     magnet-metainfo-test.cc
     makemeta-test.cc
     move-test.cc

tests/libtransmission/lpd-test.cc

@@ -0,0 +1,202 @@
+// This file Copyright (C) 2022 Mnemosyne LLC.
+// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
+// or any future license endorsed by Mnemosyne LLC.
+// License text can be found in the licenses/ folder.
+
+#include <chrono>
+#include <set>
+#include <string>
+#include <string_view>
+#include <vector>
+
+#include "transmission.h"
+
+#include "crypto-utils.h"
+#include "session.h"
+#include "tr-lpd.h"
+
+#include "test-fixtures.h"
+
+using namespace std::literals;
+
+namespace libtransmission
+{
+namespace test
+{
+
+using LpdTest = SessionTest;
+
+namespace
+{
+
+class MyMediator final : public tr_lpd::Mediator
+{
+public:
+    MyMediator() = default;
+    ~MyMediator() override = default;
+
+    [[nodiscard]] tr_port port() const override
+    {
+        return port_;
+    }
+
+    [[nodiscard]] bool allowsLPD() const override
+    {
+        return allows_lpd_;
+    }
+
+    [[nodiscard]] std::vector<TorrentInfo> torrents() const override
+    {
+        return torrents_;
+    }
+
+    void setNextAnnounceTime(std::string_view info_hash_str, time_t announce_after) override
+    {
+        for (auto& tor : torrents_)
+        {
+            if (tor.info_hash_str == info_hash_str)
+            {
+                tor.announce_after = announce_after;
+                break;
+            }
+        }
+    }
+
+    bool onPeerFound(std::string_view info_hash_str, tr_address /*address*/, tr_port /*port*/) override
+    {
+        found_.insert(std::string{ info_hash_str });
+        return found_returns_;
+    }
+
+    tr_port port_ = tr_port::fromHost(51413);
+    bool allows_lpd_ = true;
+    std::vector<TorrentInfo> torrents_;
+    std::set<std::string> found_;
+    bool found_returns_ = true;
+};
+
+auto makeRandomHash()
+{
+    auto buf = std::array<char, 256>{};
+    tr_rand_buffer(std::data(buf), std::size(buf));
+    return tr_sha1::digest(buf);
+}
+
+auto makeRandomHashString()
+{
+    return tr_strupper(tr_sha1_to_string(makeRandomHash()));
+}
+
+} // namespace
+
+TEST_F(LpdTest, HelloWorld)
+{
+    auto mediator = MyMediator{};
+    auto lpd = tr_lpd::create(mediator, session_->timerMaker(), session_->eventBase());
+    EXPECT_TRUE(lpd);
+    EXPECT_EQ(0U, std::size(mediator.found_));
+}
+
+TEST_F(LpdTest, CanAnnounceAndRead)
+{
+    auto mediator_a = MyMediator{};
+    auto lpd_a = tr_lpd::create(mediator_a, session_->timerMaker(), session_->eventBase());
+    EXPECT_TRUE(lpd_a);
+
+    auto const info_hash_str = makeRandomHashString();
+    auto info = tr_lpd::Mediator::TorrentInfo{};
+    info.info_hash_str = info_hash_str;
+    info.activity = TR_STATUS_SEED;
+    info.allows_lpd = true;
+    info.announce_after = 0; // never announced
+
+    auto mediator_b = MyMediator{};
+    mediator_b.torrents_.push_back(info);
+    auto lpd_b = tr_lpd::create(mediator_b, session_->timerMaker(), session_->eventBase());
+
+    waitFor([&mediator_a]() { return !std::empty(mediator_a.found_); }, 1s);
+    EXPECT_EQ(1U, mediator_a.found_.count(info_hash_str));
+    EXPECT_EQ(0U, mediator_b.found_.count(info_hash_str));
+}
+
+TEST_F(LpdTest, canMultiAnnounce)
+{
+    auto mediator_a = MyMediator{};
+    auto lpd_a = tr_lpd::create(mediator_a, session_->timerMaker(), session_->eventBase());
+    EXPECT_TRUE(lpd_a);
+
+    auto info_hash_strings = std::array<std::string, 2>{};
+    auto infos = std::array<tr_lpd::Mediator::TorrentInfo, 2>{};
+    auto mediator_b = MyMediator{};
+    for (size_t i = 0; i < std::size(info_hash_strings); ++i)
+    {
+        auto& info_hash_string = info_hash_strings[i];
+        auto& info = infos[i];
+
+        info_hash_string = makeRandomHashString();
+
+        info.info_hash_str = info_hash_string;
+        info.activity = TR_STATUS_SEED;
+        info.allows_lpd = true;
+        info.announce_after = 0; // never announced
+    }
+
+    for (auto const& info : infos)
+    {
+        mediator_b.torrents_.push_back(info);
+    }
+
+    auto lpd_b = tr_lpd::create(mediator_b, session_->timerMaker(), session_->eventBase());
+    waitFor([&mediator_a]() { return !std::empty(mediator_a.found_); }, 1s);
+
+    for (auto const& info : infos)
+    {
+        EXPECT_EQ(1U, mediator_a.found_.count(std::string{ info.info_hash_str }));
+    }
+}
+
+TEST_F(LpdTest, DoesNotReannounceTooSoon)
+{
+    auto mediator_a = MyMediator{};
+    auto lpd_a = tr_lpd::create(mediator_a, session_->timerMaker(), session_->eventBase());
+    EXPECT_TRUE(lpd_a);
+
+    // similar to canMultiAnnounce...
+    auto info_hash_strings = std::array<std::string, 2>{};
+    auto infos = std::array<tr_lpd::Mediator::TorrentInfo, 2>{};
+    auto mediator_b = MyMediator{};
+    for (size_t i = 0; i < std::size(info_hash_strings); ++i)
+    {
+        auto& info_hash_string = info_hash_strings[i];
+        auto& info = infos[i];
+
+        info_hash_string = makeRandomHashString();
+
+        info.info_hash_str = info_hash_string;
+        info.activity = TR_STATUS_SEED;
+        info.allows_lpd = true;
+        info.announce_after = 0; // never announced
+    }
+
+    // ...except one torrent has already been announced
+    // and doesn't need to be reannounced until later
+    auto const now = time(nullptr);
+    infos[0].announce_after = now + 60;
+
+    for (auto const& info : infos)
+    {
+        mediator_b.torrents_.push_back(info);
+    }
+
+    auto lpd_b = tr_lpd::create(mediator_b, session_->timerMaker(), session_->eventBase());
+    waitFor([&mediator_a]() { return !std::empty(mediator_a.found_); }, 1s);
+
+    for (auto& info : infos)
+    {
+        auto const expected_count = info.announce_after <= now ? 1U : 0U;
+        EXPECT_EQ(expected_count, mediator_a.found_.count(std::string{ info.info_hash_str }));
+    }
+}
+
+} // namespace test
+} // namespace libtransmission

tests/libtransmission/rename-test.cc

@@ -33,7 +33,7 @@ class RenameTest : public SessionTest
     static auto constexpr MaxWaitMsec = 3000;
 
 protected:
-    void torrentRemoveAndWait(tr_torrent* tor, int expected_torrent_count)
+    void torrentRemoveAndWait(tr_torrent* tor, size_t expected_torrent_count)
     {
         tr_torrentRemove(tor, false, nullptr);
         auto const test = [this, expected_torrent_count]()

tests/libtransmission/test-fixtures.h

@@ -71,10 +71,9 @@ static void depthFirstWalk(char const* path, file_func_t func)
     func(path);
 }
 
-inline bool waitFor(std::function<bool()> const& test, int msec)
+inline bool waitFor(std::function<bool()> const& test, std::chrono::milliseconds msec)
 {
-    auto const deadline = std::chrono::milliseconds{ msec };
-    auto const begin = std::chrono::steady_clock::now();
+    auto const deadline = std::chrono::steady_clock::now() + msec;
 
     for (;;)
     {
@@ -83,7 +82,7 @@ inline bool waitFor(std::function<bool()> const& test, int msec)
             return true;
         }
 
-        if ((std::chrono::steady_clock::now() - begin) >= deadline)
+        if (std::chrono::steady_clock::now() > deadline)
         {
             return false;
         }
@@ -92,6 +91,11 @@ inline bool waitFor(std::function<bool()> const& test, int msec)
     }
 }
 
+inline bool waitFor(std::function<bool()> const& test, int msec)
+{
+    return waitFor(test, std::chrono::milliseconds{ msec });
+}
+
 class Sandbox
 {
 public: