// This file Copyright © 2010-2022 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 // for std::find_if() #include // for errno, EAFNOSUPPORT #include // for CHAR_BIT #include // for memset() #include #include #include #include #include #include #ifdef _WIN32 #include #undef gai_strerror #define gai_strerror gai_strerrorA #endif #include #include #define LIBTRANSMISSION_ANNOUNCER_MODULE #include "transmission.h" #include "announcer.h" #include "announcer-common.h" #include "crypto-utils.h" // for tr_rand_obj() #include "log.h" #include "peer-io.h" #include "peer-mgr.h" // for tr_pex::fromCompact4() #include "tr-assert.h" #include "tr-buffer.h" #include "utils.h" #include "web-utils.h" #define logwarn(interned, msg) tr_logAddWarn(msg, (interned).sv()) #define logdbg(interned, msg) tr_logAddDebug(msg, (interned).sv()) #define logtrace(interned, msg) tr_logAddTrace(msg, (interned).sv()) using namespace std::literals; // size defined by bep15 using tau_connection_t = uint64_t; using tau_transaction_t = uint32_t; static constexpr auto TauConnectionTtlSecs = time_t{ 45 }; static auto tau_transaction_new() { return tr_rand_obj(); } // used in the "action" field of a request. Values defined in bep 15. enum tau_action_t { TAU_ACTION_CONNECT = 0, TAU_ACTION_ANNOUNCE = 1, TAU_ACTION_SCRAPE = 2, TAU_ACTION_ERROR = 3 }; /**** ***** SCRAPE ****/ struct tau_scrape_request { tau_scrape_request(tr_scrape_request const& in, tr_scrape_response_func on_response) : on_response_{ std::move(on_response) } { this->response.scrape_url = in.scrape_url; this->response.row_count = in.info_hash_count; for (int i = 0; i < this->response.row_count; ++i) { this->response.rows[i].seeders = -1; this->response.rows[i].leechers = -1; this->response.rows[i].downloads = -1; this->response.rows[i].info_hash = in.info_hash[i]; } // build the payload auto buf = libtransmission::Buffer{}; buf.addUint32(TAU_ACTION_SCRAPE); buf.addUint32(transaction_id); for (int i = 0; i < in.info_hash_count; ++i) { buf.add(in.info_hash[i]); } this->payload.insert(std::end(this->payload), std::begin(buf), std::end(buf)); } [[nodiscard]] auto has_callback() const noexcept { return !!on_response_; } void requestFinished() const { if (on_response_) { on_response_(response); } } void fail(bool did_connect, bool did_timeout, std::string_view errmsg) { response.did_connect = did_connect; response.did_timeout = did_timeout; response.errmsg = errmsg; requestFinished(); } void onResponse(tau_action_t action, libtransmission::Buffer& buf) { response.did_connect = true; response.did_timeout = false; if (action == TAU_ACTION_SCRAPE) { for (int i = 0; i < response.row_count; ++i) { if (std::size(buf) < sizeof(uint32_t) * 3) { break; } auto& row = response.rows[i]; row.seeders = buf.toUint32(); row.downloads = buf.toUint32(); row.leechers = buf.toUint32(); } requestFinished(); } else { std::string const errmsg = action == TAU_ACTION_ERROR && !std::empty(buf) ? buf.toString() : _("Unknown error"); fail(true, false, errmsg); } } [[nodiscard]] auto expiresAt() const noexcept { return created_at_ + TR_SCRAPE_TIMEOUT_SEC.count(); } std::vector payload; time_t sent_at = 0; tau_transaction_t const transaction_id = tau_transaction_new(); tr_scrape_response response = {}; private: time_t const created_at_ = tr_time(); tr_scrape_response_func on_response_; }; /**** ***** ANNOUNCE ****/ struct tau_announce_request { tau_announce_request(uint32_t announce_ip, tr_announce_request const& in, tr_announce_response_func on_response) : on_response_{ std::move(on_response) } { // https://www.bittorrent.org/beps/bep_0015.html sets key size at 32 bits static_assert(sizeof(tr_announce_request::key) * CHAR_BIT == 32); response.seeders = -1; response.leechers = -1; response.downloads = -1; response.info_hash = in.info_hash; // build the payload auto buf = libtransmission::Buffer{}; buf.addUint32(TAU_ACTION_ANNOUNCE); buf.addUint32(transaction_id); buf.add(in.info_hash); buf.add(in.peer_id); buf.addUint64(in.down); buf.addUint64(in.leftUntilComplete); buf.addUint64(in.up); buf.addUint32(get_tau_announce_event(in.event)); buf.addUint32(announce_ip); buf.addUint32(in.key); buf.addUint32(in.numwant); buf.addPort(in.port); payload.insert(std::end(payload), std::begin(buf), std::end(buf)); } [[nodiscard]] auto has_callback() const noexcept { return !!on_response_; } void requestFinished() const { if (on_response_) { on_response_(this->response); } } void fail(bool did_connect, bool did_timeout, std::string_view errmsg) { this->response.did_connect = did_connect; this->response.did_timeout = did_timeout; this->response.errmsg = errmsg; this->requestFinished(); } void onResponse(tau_action_t action, libtransmission::Buffer& buf) { auto const buflen = std::size(buf); this->response.did_connect = true; this->response.did_timeout = false; if (action == TAU_ACTION_ANNOUNCE && buflen >= 3 * sizeof(uint32_t)) { response.interval = buf.toUint32(); response.leechers = buf.toUint32(); response.seeders = buf.toUint32(); auto const contiguous = std::vector{ std::begin(buf), std::end(buf) }; response.pex = tr_pex::from_compact_ipv4(std::data(contiguous), std::size(contiguous), nullptr, 0); requestFinished(); } else { std::string const errmsg = action == TAU_ACTION_ERROR && !std::empty(buf) ? buf.toString() : _("Unknown error"); fail(true, false, errmsg); } } [[nodiscard]] auto expiresAt() const noexcept { return created_at_ + TR_ANNOUNCE_TIMEOUT_SEC.count(); } enum tau_announce_event { // Used in the "event" field of an announce request. // These values come from BEP 15 TAU_ANNOUNCE_EVENT_NONE = 0, TAU_ANNOUNCE_EVENT_COMPLETED = 1, TAU_ANNOUNCE_EVENT_STARTED = 2, TAU_ANNOUNCE_EVENT_STOPPED = 3 }; std::vector payload; time_t sent_at = 0; tau_transaction_t const transaction_id = tau_transaction_new(); tr_announce_response response = {}; private: [[nodiscard]] static constexpr tau_announce_event get_tau_announce_event(tr_announce_event e) { switch (e) { case TR_ANNOUNCE_EVENT_COMPLETED: return TAU_ANNOUNCE_EVENT_COMPLETED; case TR_ANNOUNCE_EVENT_STARTED: return TAU_ANNOUNCE_EVENT_STARTED; case TR_ANNOUNCE_EVENT_STOPPED: return TAU_ANNOUNCE_EVENT_STOPPED; default: return TAU_ANNOUNCE_EVENT_NONE; } } time_t const created_at_ = tr_time(); tr_announce_response_func on_response_; }; /**** ***** TRACKER ****/ struct tau_tracker { using Mediator = tr_announcer_udp::Mediator; tau_tracker(Mediator& mediator, tr_interned_string key_in, tr_interned_string host_in, tr_port port_in) : key{ key_in } , host{ host_in } , port{ port_in } , mediator_{ mediator } { } void sendto(std::byte const* buf, size_t buflen) { TR_ASSERT(addr_); if (!addr_) { return; } auto const& [ss, sslen] = *addr_; mediator_.sendto(buf, buflen, reinterpret_cast(&ss), sslen); } void on_connection_response(tau_action_t action, libtransmission::Buffer& buf) { this->connecting_at = 0; this->connection_transaction_id = 0; if (action == TAU_ACTION_CONNECT) { this->connection_id = buf.toUint64(); this->connection_expiration_time = tr_time() + TauConnectionTtlSecs; logdbg(this->key, fmt::format("Got a new connection ID from tracker: {}", this->connection_id)); } else if (action == TAU_ACTION_ERROR) { std::string const errmsg = !std::empty(buf) ? buf.toString() : _("Connection failed"); logdbg(this->key, errmsg); this->failAll(true, false, errmsg); } this->upkeep(); } void upkeep(bool timeout_reqs = true) { time_t const now = tr_time(); // do we have a DNS request that's ready? if (addr_pending_dns_ && addr_pending_dns_->wait_for(0ms) == std::future_status::ready) { addr_ = addr_pending_dns_->get(); addr_pending_dns_.reset(); addr_expires_at_ = now + DnsRetryIntervalSecs; } // are there any requests pending? if (this->isIdle()) { return; } // update the addr if our lookup is past its shelf date if (!addr_pending_dns_ && addr_expires_at_ <= now) { addr_.reset(); addr_pending_dns_ = std::async(std::launch::async, lookup, this->host, this->port, this->key); return; } logtrace( this->key, fmt::format( "connected {} ({} {}) -- connecting_at {}", is_connected(now), this->connection_expiration_time, now, this->connecting_at)); /* also need a valid connection ID... */ if (addr_ && !is_connected(now) && this->connecting_at == 0) { this->connecting_at = now; this->connection_transaction_id = tau_transaction_new(); logtrace(this->key, fmt::format("Trying to connect. Transaction ID is {}", this->connection_transaction_id)); auto buf = libtransmission::Buffer{}; buf.addUint64(0x41727101980LL); buf.addUint32(TAU_ACTION_CONNECT); buf.addUint32(this->connection_transaction_id); auto const contiguous = std::vector(std::begin(buf), std::end(buf)); this->sendto(std::data(contiguous), std::size(contiguous)); } if (timeout_reqs) { timeout_requests(now); } if (addr_ && is_connected(now)) { send_requests(); } } private: using Sockaddr = std::pair; using MaybeSockaddr = std::optional; [[nodiscard]] constexpr bool is_connected(time_t now) const noexcept { return connection_id != tau_connection_t{} && now < connection_expiration_time; } [[nodiscard]] static MaybeSockaddr lookup(tr_interned_string host, tr_port port, tr_interned_string logname) { auto szport = std::array{}; *fmt::format_to(std::data(szport), FMT_STRING("{:d}"), port.host()) = '\0'; auto hints = addrinfo{}; hints.ai_family = AF_UNSPEC; hints.ai_protocol = IPPROTO_UDP; hints.ai_socktype = SOCK_DGRAM; addrinfo* info = nullptr; if (int const rc = getaddrinfo(host.c_str(), std::data(szport), &hints, &info); rc != 0) { logwarn( logname, fmt::format( _("Couldn't look up '{address}:{port}': {error} ({error_code})"), fmt::arg("address", host.sv()), fmt::arg("port", port.host()), fmt::arg("error", gai_strerror(rc)), fmt::arg("error_code", static_cast(rc)))); return {}; } auto ss = sockaddr_storage{}; auto const len = info->ai_addrlen; memcpy(&ss, info->ai_addr, len); freeaddrinfo(info); logdbg(logname, "DNS lookup succeeded"); return std::make_pair(ss, len); } [[nodiscard]] bool isIdle() const noexcept { return std::empty(announces) && std::empty(scrapes) && !addr_pending_dns_; } void failAll(bool did_connect, bool did_timeout, std::string_view errmsg) { for (auto& req : this->scrapes) { req.fail(did_connect, did_timeout, errmsg); } for (auto& req : this->announces) { req.fail(did_connect, did_timeout, errmsg); } this->scrapes.clear(); this->announces.clear(); } /// void timeout_requests(time_t now) { if (this->connecting_at != 0 && this->connecting_at + ConnectionRequestTtl < now) { auto empty_buf = libtransmission::Buffer{}; on_connection_response(TAU_ACTION_ERROR, empty_buf); } timeout_requests(this->announces, now, "announce"); timeout_requests(this->scrapes, now, "scrape"); } template void timeout_requests(std::list& requests, time_t now, std::string_view name) { for (auto it = std::begin(requests); it != std::end(requests);) { if (auto& req = *it; req.expiresAt() <= now) { logtrace(this->key, fmt::format("timeout {} req {}", name, fmt::ptr(&req))); req.fail(false, true, ""); it = requests.erase(it); } else { ++it; } } } /// void send_requests() { TR_ASSERT(!addr_pending_dns_); TR_ASSERT(addr_); TR_ASSERT(this->connecting_at == 0); TR_ASSERT(this->connection_expiration_time > tr_time()); send_requests(this->announces); send_requests(this->scrapes); } template void send_requests(std::list& reqs) { auto const now = tr_time(); for (auto it = std::begin(reqs); it != std::end(reqs);) { auto& req = *it; if (req.sent_at != 0) // it's already been sent; we're awaiting a response { ++it; continue; } logdbg(this->key, fmt::format("sending req {}", fmt::ptr(&req))); req.sent_at = now; send_request(std::data(req.payload), std::size(req.payload)); if (req.has_callback()) { ++it; continue; } // no response needed, so we can remove it now it = reqs.erase(it); } } void send_request(std::byte const* payload, size_t payload_len) { logdbg(this->key, fmt::format("sending request w/connection id {}", this->connection_id)); auto buf = libtransmission::Buffer{}; buf.addUint64(this->connection_id); buf.add(payload, payload_len); auto const contiguous = std::vector(std::begin(buf), std::end(buf)); this->sendto(std::data(contiguous), std::size(contiguous)); } public: tr_interned_string const key; tr_interned_string const host; tr_port const port; time_t connecting_at = 0; time_t connection_expiration_time = 0; tau_connection_t connection_id = {}; tau_transaction_t connection_transaction_id = {}; std::list announces; std::list scrapes; private: Mediator& mediator_; std::optional> addr_pending_dns_ = {}; MaybeSockaddr addr_ = {}; time_t addr_expires_at_ = 0; static inline constexpr auto DnsRetryIntervalSecs = time_t{ 3600 }; static inline constexpr auto ConnectionRequestTtl = int{ 30 }; }; /**** ***** SESSION ****/ class tr_announcer_udp_impl final : public tr_announcer_udp { public: explicit tr_announcer_udp_impl(Mediator& mediator) : mediator_{ mediator } { } void announce(tr_announce_request const& request, tr_announce_response_func on_response) override { auto* const tracker = getTrackerFromUrl(request.announce_url); if (tracker == nullptr) { return; } // Since size of IP field is only 4 bytes long, we can only announce IPv4 addresses auto const addr = mediator_.announceIP(); uint32_t const announce_ip = addr && addr->is_ipv4() ? addr->addr.addr4.s_addr : 0; tracker->announces.emplace_back(announce_ip, request, std::move(on_response)); tracker->upkeep(false); } void scrape(tr_scrape_request const& request, tr_scrape_response_func on_response) override { auto* const tracker = getTrackerFromUrl(request.scrape_url); if (tracker == nullptr) { return; } tracker->scrapes.emplace_back(request, std::move(on_response)); tracker->upkeep(false); } void upkeep() override { for (auto& tracker : trackers_) { tracker.upkeep(); } } // @brief process an incoming udp message if it's a tracker response. // @return true if msg was a tracker response; false otherwise bool handleMessage(uint8_t const* msg, size_t msglen) override { if (msglen < sizeof(uint32_t) * 2) { return false; } // extract the action_id and see if it makes sense auto buf = libtransmission::Buffer{}; buf.add(msg, msglen); auto const action_id = static_cast(buf.toUint32()); if (!isResponseMessage(action_id, msglen)) { return false; } /* extract the transaction_id and look for a match */ tau_transaction_t const transaction_id = buf.toUint32(); for (auto& tracker : trackers_) { // is it a connection response? if (tracker.connecting_at != 0 && transaction_id == tracker.connection_transaction_id) { logtrace(tracker.key, fmt::format("{} is my connection request!", transaction_id)); tracker.on_connection_response(action_id, buf); return true; } // is it a response to one of this tracker's announces? if (auto& reqs = tracker.announces; !std::empty(reqs)) { auto it = std::find_if( std::begin(reqs), std::end(reqs), [&transaction_id](auto const& req) { return req.transaction_id == transaction_id; }); if (it != std::end(reqs)) { logtrace(tracker.key, fmt::format("{} is an announce request!", transaction_id)); auto req = *it; it = reqs.erase(it); req.onResponse(action_id, buf); return true; } } // is it a response to one of this tracker's scrapes? if (auto& reqs = tracker.scrapes; !std::empty(reqs)) { auto it = std::find_if( std::begin(reqs), std::end(reqs), [&transaction_id](auto const& req) { return req.transaction_id == transaction_id; }); if (it != std::end(reqs)) { logtrace(tracker.key, fmt::format("{} is a scrape request!", transaction_id)); auto req = *it; it = reqs.erase(it); req.onResponse(action_id, buf); return true; } } } /* no match... */ return false; } private: // Finds the tau_tracker struct that corresponds to this url. // If it doesn't exist yet, create one. tau_tracker* getTrackerFromUrl(tr_interned_string announce_url) { // build a lookup key for this tracker auto const parsed = tr_urlParseTracker(announce_url); TR_ASSERT(parsed); if (!parsed) { return nullptr; } // see if we already have it auto const key = tr_announcerGetKey(*parsed); for (auto& tracker : trackers_) { if (tracker.key == key) { return &tracker; } } // we don't have it -- build a new one trackers_.emplace_back(mediator_, key, tr_interned_string(parsed->host), tr_port::fromHost(parsed->port)); auto* const tracker = &trackers_.back(); logtrace(tracker->key, "New tau_tracker created"); return tracker; } [[nodiscard]] static constexpr bool isResponseMessage(tau_action_t action, size_t msglen) noexcept { if (action == TAU_ACTION_CONNECT) { return msglen == 16; } if (action == TAU_ACTION_ANNOUNCE) { return msglen >= 20; } if (action == TAU_ACTION_SCRAPE) { return msglen >= 20; } if (action == TAU_ACTION_ERROR) { return msglen >= 8; } return false; } std::list trackers_; Mediator& mediator_; }; std::unique_ptr tr_announcer_udp::create(Mediator& mediator) { return std::make_unique(mediator); }