mirror of
https://github.com/transmission/transmission
synced 2024-12-25 01:03:01 +00:00
600 lines
19 KiB
C++
600 lines
19 KiB
C++
// Except where noted, this file Copyright © 2010-2023 Johannes Lieder.
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// It may be used under the MIT (SPDX: MIT) license.
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// License text can be found in the licenses/ folder.
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#include <algorithm>
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#include <array>
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#include <chrono>
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#include <cstdint>
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#include <functional>
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#include <memory>
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#include <optional>
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#include <sstream>
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#include <string>
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#ifdef _WIN32
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#include <ws2tcpip.h>
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#else
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#include <ctime>
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#include <sys/socket.h> /* socket(), bind() */
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#include <netinet/in.h> /* sockaddr_in */
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#endif
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#include <event2/event.h>
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#include <fmt/core.h>
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#include "libtransmission/transmission.h"
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#include "libtransmission/crypto-utils.h" // for tr_rand_obj()
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#include "libtransmission/log.h"
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#include "libtransmission/net.h"
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#include "libtransmission/timer.h"
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#include "libtransmission/tr-assert.h"
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#include "libtransmission/tr-lpd.h"
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#include "libtransmission/utils.h" // for tr_net_init()
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#include "libtransmission/utils-ev.h" // for tr_net_init()
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using namespace std::literals;
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// Code in this namespace Copyright © 2022 Mnemosyne LLC.
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// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only), MIT (SPDX: MIT),
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// or any future license endorsed by Mnemosyne LLC.
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// License text can be found in the licenses/ folder.
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namespace
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{
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// opaque value, allowing the sending client to filter out its
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// own announces if it receives them via multicast loopback
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auto makeCookie()
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{
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static auto constexpr Pool = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"sv;
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auto buf = tr_rand_obj<std::array<char, 12>>();
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for (auto& ch : buf)
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{
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ch = Pool[static_cast<unsigned char>(ch) % std::size(Pool)];
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}
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return std::string{ std::data(buf), std::size(buf) };
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}
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constexpr char const* const McastGroup = "239.192.152.143"; /**<LPD multicast group */
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auto constexpr McastPort = tr_port::fromHost(6771); /**<LPD source and destination UPD port */
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/*
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* A LSD announce is formatted as follows:
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*
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* ```
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* BT-SEARCH * HTTP/1.1\r\n
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* Host: <host>\r\n
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* Port: <port>\r\n
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* Infohash: <ihash>\r\n
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* cookie: <cookie (optional)>\r\n
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* \r\n
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* \r\n
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* ```
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*
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* An announce may contain multiple, consecutive Infohash headers
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* to announce the participation in more than one torrent. This
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* may not be supported by older implementations. When sending
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* multiple infohashes the packet length should not exceed 1400
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* bytes to avoid MTU/fragmentation problems.
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*/
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auto makeAnnounceMsg(std::string_view cookie, tr_port port, std::string_view const* info_hash_strings, size_t n_strings)
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{
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static auto constexpr Major = 1;
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static auto constexpr Minor = 1;
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static auto constexpr CrLf = "\r\n"sv;
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auto ostr = std::ostringstream{};
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ostr << "BT-SEARCH * HTTP/" << Major << '.' << Minor << CrLf //
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<< "Host: " << McastGroup << ':' << McastPort.host() << CrLf //
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<< "Port: " << port.host() << CrLf;
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for (size_t i = 0; i < n_strings; ++i)
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{
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ostr << "Infohash: " << tr_strupper(info_hash_strings[i]) << CrLf;
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}
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if (!std::empty(cookie))
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{
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ostr << "cookie: " << cookie << CrLf;
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}
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ostr << CrLf << CrLf;
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return ostr.str();
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}
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struct ParsedAnnounce
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{
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int major;
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int minor;
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tr_port port;
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std::vector<std::string_view> info_hash_strings;
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std::string_view cookie;
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};
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std::optional<ParsedAnnounce> parseAnnounceMsg(std::string_view announce)
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{
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static auto constexpr CrLf = "\r\n"sv;
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auto ret = ParsedAnnounce{};
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// get major, minor
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auto key = "BT-SEARCH * HTTP/"sv;
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if (auto const pos = announce.find(key); pos != std::string_view::npos)
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{
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// parse `${major}.${minor}`
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auto walk = announce.substr(pos + std::size(key));
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if (auto const major = tr_num_parse<int>(walk, &walk); major && tr_strv_starts_with(walk, '.'))
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{
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ret.major = *major;
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}
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else
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{
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return {};
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}
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walk.remove_prefix(1); // the '.' between major and minor
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if (auto const minor = tr_num_parse<int>(walk, &walk); minor && tr_strv_starts_with(walk, CrLf))
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{
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ret.minor = *minor;
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}
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else
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{
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return {};
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}
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}
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key = "Port: "sv;
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if (auto const pos = announce.find(key); pos != std::string_view::npos)
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{
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auto walk = announce.substr(pos + std::size(key));
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if (auto const port = tr_num_parse<uint16_t>(walk, &walk); port && tr_strv_starts_with(walk, CrLf))
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{
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ret.port = tr_port::fromHost(*port);
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}
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else
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{
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return {};
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}
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}
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key = "cookie: "sv;
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if (auto const pos = announce.find(key); pos != std::string_view::npos)
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{
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auto walk = announce.substr(pos + std::size(key));
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if (auto const end = walk.find(CrLf); end != std::string_view::npos)
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{
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ret.cookie = walk.substr(0, end);
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}
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else
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{
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return {};
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}
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}
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key = "Infohash: "sv;
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for (;;)
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{
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if (auto const pos = announce.find(key); pos != std::string_view::npos)
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{
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announce.remove_prefix(pos + std::size(key));
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}
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else
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{
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break;
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}
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if (auto const end = announce.find(CrLf); end != std::string_view::npos)
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{
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ret.info_hash_strings.push_back(announce.substr(0, end));
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announce.remove_prefix(end + std::size(CrLf));
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}
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else
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{
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return {};
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}
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}
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return ret;
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}
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} // namespace
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class tr_lpd_impl final : public tr_lpd
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{
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public:
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tr_lpd_impl(Mediator& mediator, struct event_base* event_base)
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: mediator_{ mediator }
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, announce_timer_{ mediator.timerMaker().create([this]() { announceUpkeep(); }) }
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, dos_timer_{ mediator.timerMaker().create([this]() { dosUpkeep(); }) }
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{
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if (!init(event_base))
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{
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return;
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}
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announce_timer_->start_repeating(AnnounceInterval);
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announceUpkeep();
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dos_timer_->start_repeating(DosInterval);
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dosUpkeep();
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}
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tr_lpd_impl(tr_lpd_impl&&) = delete;
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tr_lpd_impl(tr_lpd_impl const&) = delete;
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tr_lpd_impl& operator=(tr_lpd_impl&&) = delete;
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tr_lpd_impl& operator=(tr_lpd_impl const&) = delete;
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~tr_lpd_impl() override
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{
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event_.reset();
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if (mcast_rcv_socket_ != TR_BAD_SOCKET)
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{
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evutil_closesocket(mcast_rcv_socket_);
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}
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if (mcast_snd_socket_ != TR_BAD_SOCKET)
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{
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evutil_closesocket(mcast_snd_socket_);
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}
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tr_logAddTrace("Done uninitialising Local Peer Discovery");
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}
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private:
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bool init(struct event_base* event_base)
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{
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if (initImpl(event_base))
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{
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return true;
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}
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auto const err = sockerrno;
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evutil_closesocket(mcast_rcv_socket_);
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evutil_closesocket(mcast_snd_socket_);
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mcast_rcv_socket_ = TR_BAD_SOCKET;
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mcast_snd_socket_ = TR_BAD_SOCKET;
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tr_logAddWarn(fmt::format(
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_("Couldn't initialize LPD: {error} ({error_code})"),
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fmt::arg("error", tr_strerror(err)),
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fmt::arg("error_code", err)));
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return false;
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}
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/**
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* @brief Initializes Local Peer Discovery for this node
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*
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* For the most part, this means setting up an appropriately configured multicast socket
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* and event-based message handling.
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*
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* @remark Since the LPD service does not use another protocol family yet, this code is
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* IPv4 only for the time being.
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*/
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bool initImpl(struct event_base* event_base)
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{
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int const opt_on = 1;
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static_assert(AnnounceScope > 0);
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tr_logAddDebug("Initialising Local Peer Discovery");
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/* setup datagram socket (receive) */
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{
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mcast_rcv_socket_ = socket(PF_INET, SOCK_DGRAM, 0);
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if (mcast_rcv_socket_ == TR_BAD_SOCKET)
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{
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return false;
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}
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if (evutil_make_socket_nonblocking(mcast_rcv_socket_) == -1)
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{
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return false;
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}
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if (setsockopt(
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mcast_rcv_socket_,
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SOL_SOCKET,
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SO_REUSEADDR,
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reinterpret_cast<char const*>(&opt_on),
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sizeof(opt_on)) == -1)
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{
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return false;
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}
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#if HAVE_SO_REUSEPORT
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if (setsockopt(
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mcast_rcv_socket_,
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SOL_SOCKET,
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SO_REUSEPORT,
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reinterpret_cast<char const*>(&opt_on),
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sizeof(opt_on)) == -1)
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{
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return false;
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}
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#endif
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mcast_addr_ = {};
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mcast_addr_.sin_family = AF_INET;
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mcast_addr_.sin_port = McastPort.network();
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mcast_addr_.sin_addr.s_addr = INADDR_ANY;
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if (bind(mcast_rcv_socket_, reinterpret_cast<sockaddr*>(&mcast_addr_), sizeof(mcast_addr_)) == -1)
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{
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return false;
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}
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if (evutil_inet_pton(mcast_addr_.sin_family, McastGroup, &mcast_addr_.sin_addr) == -1)
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{
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return false;
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}
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/* we want to join that LPD multicast group */
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struct ip_mreq mcast_req = {};
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mcast_req.imr_multiaddr = mcast_addr_.sin_addr;
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mcast_req.imr_interface.s_addr = INADDR_ANY;
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if (setsockopt(
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mcast_rcv_socket_,
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IPPROTO_IP,
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IP_ADD_MEMBERSHIP,
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reinterpret_cast<char const*>(&mcast_req),
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sizeof(struct ip_mreq)) == -1)
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{
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return false;
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}
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}
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/* setup datagram socket (send) */
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{
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unsigned char const scope = AnnounceScope;
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mcast_snd_socket_ = socket(PF_INET, SOCK_DGRAM, 0);
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if (mcast_snd_socket_ == TR_BAD_SOCKET)
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{
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return false;
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}
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if (evutil_make_socket_nonblocking(mcast_snd_socket_) == -1)
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{
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return false;
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}
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/* configure outbound multicast TTL */
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if (setsockopt(
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mcast_snd_socket_,
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IPPROTO_IP,
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IP_MULTICAST_TTL,
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reinterpret_cast<char const*>(&scope),
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sizeof(scope)) == -1)
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{
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return false;
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}
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}
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/* Note: lpd_unsolicitedMsgCounter remains 0 until the first timeout event, thus
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* any announcement received during the initial interval will be discarded. */
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event_.reset(event_new(event_base, mcast_rcv_socket_, EV_READ | EV_PERSIST, event_callback, this));
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event_add(event_.get(), nullptr);
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tr_logAddDebug("Local Peer Discovery initialised");
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return true;
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}
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/**
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* @brief Processing of timeout notifications and incoming data on the socket
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* @note maximum rate of read events is limited according to @a lpd_maxAnnounceCap
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* @see DoS */
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static void event_callback(evutil_socket_t /*s*/, short type, void* vself)
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{
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if ((type & EV_READ) != 0)
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{
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static_cast<tr_lpd_impl*>(vself)->onCanRead();
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}
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}
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void onCanRead()
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{
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if (!mediator_.allowsLPD())
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{
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return;
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}
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// process announcement from foreign peer
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struct sockaddr_in foreign_addr = {};
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auto addr_len = socklen_t{ sizeof(foreign_addr) };
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auto foreign_msg = std::array<char, MaxDatagramLength>{};
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auto const res = recvfrom(
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mcast_rcv_socket_,
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std::data(foreign_msg),
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MaxDatagramLength,
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0,
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reinterpret_cast<sockaddr*>(&foreign_addr),
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&addr_len);
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// If we couldn't read it or it was too big, discard it
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if (res < 1 || static_cast<size_t>(res) > MaxDatagramLength)
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{
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return;
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}
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// If it doesn't look like a BEP14 message, discard it
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auto const msg = std::string_view{ std::data(foreign_msg), static_cast<size_t>(res) };
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if (static auto constexpr SearchKey = "BT-SEARCH * HTTP/"sv; msg.find(SearchKey) == std::string_view::npos)
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{
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return;
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}
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// If we're receiving too many, discard it
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if (++messages_received_since_upkeep_ > MaxIncomingPerUpkeep)
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{
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return;
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}
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// If it's an invalid message or the wrong protocol version, discard it.
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// Note this comes *after* incrementing the count since there is some
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// small CPU overhead in parsing, so don't do it for *every* message
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auto const parsed = parseAnnounceMsg(msg);
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if (!parsed || parsed->major != 1 || parsed->minor < 1 || parsed->cookie == cookie_)
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{
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tr_logAddTrace("Discarded invalid multicast message");
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return;
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}
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auto peer_addr = tr_address{};
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peer_addr.addr.addr4 = foreign_addr.sin_addr;
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for (auto const& hash_string : parsed->info_hash_strings)
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{
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if (!mediator_.onPeerFound(hash_string, peer_addr, parsed->port))
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{
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tr_logAddDebug(fmt::format(FMT_STRING("Cannot serve torrent #{:s}"), hash_string));
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}
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}
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}
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void announceUpkeep()
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{
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if (!mediator_.allowsLPD())
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{
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return;
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}
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auto torrents = mediator_.torrents();
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// remove torrents that don't need to be announced
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auto const now = tr_time();
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auto const needs_announce = [&now](auto& info)
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{
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return info.allows_lpd && (info.activity == TR_STATUS_DOWNLOAD || info.activity == TR_STATUS_SEED) &&
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(info.announce_after < now);
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};
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torrents.erase(
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std::remove_if(std::begin(torrents), std::end(torrents), std::not_fn(needs_announce)),
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std::end(torrents));
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if (std::empty(torrents))
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{
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return;
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}
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// prioritize the remaining torrents
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std::sort(
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std::begin(torrents),
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std::end(torrents),
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[](auto const& a, auto const& b)
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{
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if (a.activity != b.activity)
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{
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return a.activity < b.activity;
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}
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if (a.announce_after != b.announce_after)
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{
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return a.announce_after < b.announce_after;
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}
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return false;
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});
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// cram in as many as will fit in a message
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auto const baseline_size = std::size(makeAnnounceMsg(cookie_, mediator_.port(), nullptr, 0));
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auto const size_with_one = std::size(makeAnnounceMsg(cookie_, mediator_.port(), &torrents.front().info_hash_str, 1));
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auto const size_per_hash = size_with_one - baseline_size;
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auto const max_torrents_per_announce = (MaxDatagramLength - baseline_size) / size_per_hash;
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auto info_hash_strings = std::vector<std::string_view>{};
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info_hash_strings.resize(std::min(std::size(torrents), max_torrents_per_announce));
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std::transform(
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std::begin(torrents),
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std::begin(torrents) + std::size(info_hash_strings),
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std::begin(info_hash_strings),
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[](auto const& tor) { return tor.info_hash_str; });
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if (!sendAnnounce(std::data(info_hash_strings), std::size(info_hash_strings)))
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{
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return;
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}
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auto const next_announce_after = now + TorrentAnnounceIntervalSec;
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for (auto const& info_hash_string : info_hash_strings)
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{
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mediator_.setNextAnnounceTime(info_hash_string, next_announce_after);
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}
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}
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void dosUpkeep()
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{
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if (messages_received_since_upkeep_ > MaxIncomingPerUpkeep)
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{
|
|
tr_logAddTrace(fmt::format(
|
|
"Dropped {} announces in the last interval (max. {} allowed)",
|
|
messages_received_since_upkeep_ - MaxIncomingPerUpkeep,
|
|
MaxIncomingPerUpkeep));
|
|
}
|
|
|
|
messages_received_since_upkeep_ = 0;
|
|
}
|
|
|
|
/**
|
|
* @brief Announce the given torrent on the local network
|
|
*
|
|
* @return Returns a success flag
|
|
*
|
|
* Send a query for torrent t out to the LPD multicast group (or the LAN, for that
|
|
* matter). A listening client on the same network might react by adding us to his
|
|
* peer pool for torrent t.
|
|
*/
|
|
bool sendAnnounce(std::string_view const* info_hash_strings, size_t n_strings)
|
|
{
|
|
auto const announce = makeAnnounceMsg(cookie_, mediator_.port(), info_hash_strings, n_strings);
|
|
TR_ASSERT(std::size(announce) <= MaxDatagramLength);
|
|
auto const res = sendto(
|
|
mcast_snd_socket_,
|
|
std::data(announce),
|
|
std::size(announce),
|
|
0,
|
|
reinterpret_cast<sockaddr const*>(&mcast_addr_),
|
|
sizeof(mcast_addr_));
|
|
auto const sent = res == static_cast<int>(std::size(announce));
|
|
return sent;
|
|
}
|
|
|
|
std::string const cookie_ = makeCookie();
|
|
Mediator& mediator_;
|
|
tr_socket_t mcast_rcv_socket_ = TR_BAD_SOCKET; /**<separate multicast receive socket */
|
|
tr_socket_t mcast_snd_socket_ = TR_BAD_SOCKET; /**<and multicast send socket */
|
|
libtransmission::evhelpers::event_unique_ptr event_;
|
|
|
|
static auto constexpr MaxDatagramLength = size_t{ 1400 };
|
|
sockaddr_in mcast_addr_ = {}; /**<initialized from the above constants in init() */
|
|
|
|
// BEP14: "To avoid causing multicast storms on large networks a
|
|
// client should send no more than 1 announce per minute."
|
|
static auto constexpr AnnounceInterval = 1min;
|
|
std::unique_ptr<libtransmission::Timer> announce_timer_;
|
|
|
|
// Flood Protection:
|
|
// To protect against message flooding, stop processing search messages
|
|
// after processing N per upkeep. If we hit that limit, we're either
|
|
// in a *very* crowded multicast group or a hostile host is sending us
|
|
// bogus data. Better to drop a few packets than get DoS'ed.
|
|
static auto constexpr DosInterval = 5s;
|
|
std::unique_ptr<libtransmission::Timer> dos_timer_;
|
|
static auto constexpr MaxIncomingPerSecond = int{ 10 };
|
|
static auto constexpr MaxIncomingPerUpkeep = std::chrono::duration_cast<std::chrono::seconds>(DosInterval).count() *
|
|
MaxIncomingPerSecond;
|
|
// @brief throw away messages after this number exceeds MaxIncomingPerUpkeep
|
|
size_t messages_received_since_upkeep_ = 0U;
|
|
|
|
static auto constexpr TorrentAnnounceIntervalSec = time_t{ 240U }; // how frequently to reannounce the same torrent
|
|
static auto constexpr TtlSameSubnet = int{ 1 };
|
|
static auto constexpr AnnounceScope = int{ TtlSameSubnet }; /**<the maximum scope for LPD datagrams */
|
|
};
|
|
|
|
std::unique_ptr<tr_lpd> tr_lpd::create(Mediator& mediator, struct event_base* event_base)
|
|
{
|
|
return std::make_unique<tr_lpd_impl>(mediator, event_base);
|
|
}
|