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transmission/libtransmission/peer-msgs.cc

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// This file Copyright © 2007-2023 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 <algorithm>
#include <array>
#include <bitset>
#include <cerrno>
#include <cstring>
#include <ctime>
#include <iterator>
#include <map>
#include <memory> // std::unique_ptr
#include <optional>
#include <queue>
#include <utility>
#include <vector>
#include <fmt/core.h>
#include "libtransmission/transmission.h"
#include "libtransmission/bitfield.h"
#include "libtransmission/cache.h"
#include "libtransmission/completion.h"
#include "libtransmission/crypto-utils.h"
#include "libtransmission/file.h"
#include "libtransmission/log.h"
#include "libtransmission/peer-io.h"
#include "libtransmission/peer-mgr.h"
#include "libtransmission/peer-msgs.h"
#include "libtransmission/quark.h"
#include "libtransmission/session.h"
#include "libtransmission/timer.h"
#include "libtransmission/torrent-magnet.h"
#include "libtransmission/torrent.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/tr-buffer.h"
#include "libtransmission/tr-dht.h"
#include "libtransmission/utils.h"
#include "libtransmission/variant.h"
#include "libtransmission/version.h"
#ifndef EBADMSG
#define EBADMSG EINVAL
#endif
using namespace std::literals;
using PeerMessageBuffer = libtransmission::Buffer;
using PeerMessageReader = libtransmission::BufferReader<std::byte>;
namespace
{
// these values are hardcoded by various BEPs as noted
namespace BtPeerMsgs
{
// http://bittorrent.org/beps/bep_0003.html#peer-messages
auto constexpr Choke = uint8_t{ 0 };
auto constexpr Unchoke = uint8_t{ 1 };
auto constexpr Interested = uint8_t{ 2 };
auto constexpr NotInterested = uint8_t{ 3 };
auto constexpr Have = uint8_t{ 4 };
auto constexpr Bitfield = uint8_t{ 5 };
auto constexpr Request = uint8_t{ 6 };
auto constexpr Piece = uint8_t{ 7 };
auto constexpr Cancel = uint8_t{ 8 };
// http://bittorrent.org/beps/bep_0005.html
auto constexpr Port = uint8_t{ 9 };
// https://www.bittorrent.org/beps/bep_0006.html
auto constexpr FextSuggest = uint8_t{ 13 };
auto constexpr FextHaveAll = uint8_t{ 14 };
auto constexpr FextHaveNone = uint8_t{ 15 };
auto constexpr FextReject = uint8_t{ 16 };
auto constexpr FextAllowedFast = uint8_t{ 17 };
// http://bittorrent.org/beps/bep_0010.html
// see also LtepMessageIds below
auto constexpr Ltep = uint8_t{ 20 };
[[nodiscard]] constexpr std::string_view debug_name(uint8_t type) noexcept
{
switch (type)
{
case Bitfield:
return "bitfield"sv;
case Cancel:
return "cancel"sv;
case Choke:
return "choke"sv;
case FextAllowedFast:
return "fext-allow-fast"sv;
case FextHaveAll:
return "fext-have-all"sv;
case FextHaveNone:
return "fext-have-none"sv;
case FextReject:
return "fext-reject"sv;
case FextSuggest:
return "fext-suggest"sv;
case Have:
return "have"sv;
case Interested:
return "interested"sv;
case Ltep:
return "ltep"sv;
case NotInterested:
return "not-interested"sv;
case Piece:
return "piece"sv;
case Port:
return "port"sv;
case Request:
return "request"sv;
case Unchoke:
return "unchoke"sv;
default:
return "unknown"sv;
}
}
} // namespace BtPeerMsgs
namespace LtepMessages
{
// http://bittorrent.org/beps/bep_0010.html
auto constexpr Handshake = uint8_t{ 0 };
} // namespace LtepMessages
// http://bittorrent.org/beps/bep_0010.html
// Client-defined extension message IDs that we tell peers about
// in the LTEP handshake and will respond to when sent in an LTEP
// message.
enum LtepMessageIds
{
// we support peer exchange (bep 11)
// https://www.bittorrent.org/beps/bep_0011.html
UT_PEX_ID = 1,
// we support sending metadata files (bep 9)
// https://www.bittorrent.org/beps/bep_0009.html
// see also MetadataMsgType below
UT_METADATA_ID = 3,
};
// http://bittorrent.org/beps/bep_0009.html
namespace MetadataMsgType
{
auto constexpr Request = int{ 0 };
auto constexpr Data = int{ 1 };
auto constexpr Reject = int{ 2 };
} // namespace MetadataMsgType
auto constexpr MinChokePeriodSec = int{ 10 };
// idle seconds before we send a keepalive
auto constexpr KeepaliveIntervalSecs = int{ 100 };
auto constexpr MetadataReqQ = int{ 64 };
auto constexpr ReqQ = int{ 512 };
// used in lowering the outMessages queue period
// how many blocks to keep prefetched per peer
auto constexpr PrefetchMax = size_t{ 18 };
// when we're making requests from another peer,
// batch them together to send enough requests to
// meet our bandwidth goals for the next N seconds
auto constexpr RequestBufSecs = int{ 10 };
// ---
auto constexpr MaxPexPeerCount = size_t{ 50 };
// ---
enum class EncryptionPreference
{
Unknown,
Yes,
No
};
// ---
struct peer_request
{
uint32_t index = 0;
uint32_t offset = 0;
uint32_t length = 0;
[[nodiscard]] auto constexpr operator==(peer_request const& that) const noexcept
{
return this->index == that.index && this->offset == that.offset && this->length == that.length;
}
};
peer_request blockToReq(tr_torrent const* tor, tr_block_index_t block)
{
auto const loc = tor->block_loc(block);
return peer_request{ loc.piece, loc.piece_offset, tor->block_size(block) };
}
// ---
/* this is raw, unchanged data from the peer regarding
* the current message that it's sending us. */
struct tr_incoming
{
std::optional<uint32_t> length; // the full message payload length. Includes the +1 for id length
std::optional<uint8_t> id; // the protocol message, e.g. BtPeerMsgs::Piece
PeerMessageBuffer payload;
struct incoming_piece_data
{
explicit incoming_piece_data(uint32_t block_size)
: buf{ std::make_unique<Cache::BlockData>(block_size) }
, block_size_{ block_size }
{
}
[[nodiscard]] bool add_span(size_t begin, size_t end)
{
if (begin > end || end > block_size_)
{
return false;
}
for (; begin < end; ++begin)
{
have_.set(begin);
}
return true;
}
[[nodiscard]] auto has_all() const noexcept
{
return have_.count() >= block_size_;
}
std::unique_ptr<Cache::BlockData> buf;
private:
std::bitset<tr_block_info::BlockSize> have_;
size_t const block_size_;
};
std::map<tr_block_index_t, incoming_piece_data> blocks;
};
class tr_peerMsgsImpl;
// TODO: make these to be member functions
ReadState canRead(tr_peerIo* io, void* vmsgs, size_t* piece);
void cancelAllRequestsToClient(tr_peerMsgsImpl* msgs);
void didWrite(tr_peerIo* io, size_t bytes_written, bool was_piece_data, void* vmsgs);
void gotError(tr_peerIo* io, tr_error const& err, void* vmsgs);
void peerPulse(void* vmsgs);
size_t protocolSendCancel(tr_peerMsgsImpl* msgs, struct peer_request const& req);
size_t protocolSendChoke(tr_peerMsgsImpl* msgs, bool choke);
size_t protocolSendHave(tr_peerMsgsImpl* msgs, tr_piece_index_t index);
size_t protocolSendPort(tr_peerMsgsImpl* msgs, tr_port port);
size_t protocolSendRequest(tr_peerMsgsImpl* msgs, struct peer_request const& req);
void sendInterest(tr_peerMsgsImpl* msgs, bool b);
void sendLtepHandshake(tr_peerMsgsImpl* msgs);
void tellPeerWhatWeHave(tr_peerMsgsImpl* msgs);
void updateDesiredRequestCount(tr_peerMsgsImpl* msgs);
#define myLogMacro(msgs, level, text) \
do \
{ \
if (tr_logLevelIsActive(level)) \
{ \
tr_logAddMessage( \
__FILE__, \
__LINE__, \
(level), \
fmt::format(FMT_STRING("{:s} [{:s}]: {:s}"), (msgs)->io->display_name(), (msgs)->user_agent().sv(), text), \
(msgs)->torrent->name()); \
} \
} while (0)
#define logdbg(msgs, text) myLogMacro(msgs, TR_LOG_DEBUG, text)
#define logtrace(msgs, text) myLogMacro(msgs, TR_LOG_TRACE, text)
#define logwarn(msgs, text) myLogMacro(msgs, TR_LOG_WARN, text)
using ReadResult = std::pair<ReadState, size_t /*n_piece_data_bytes_read*/>;
/**
* Low-level communication state information about a connected peer.
*
* This structure remembers the low-level protocol states that we're
* in with this peer, such as active requests, pex messages, and so on.
* Its fields are all private to peer-msgs.c.
*
* Data not directly involved with sending & receiving messages is
* stored in tr_peer, where it can be accessed by both peermsgs and
* the peer manager.
*
* @see struct peer_atom
* @see tr_peer
*/
class tr_peerMsgsImpl final : public tr_peerMsgs
{
public:
tr_peerMsgsImpl(
tr_torrent* torrent_in,
peer_atom* atom_in,
std::shared_ptr<tr_peerIo> io_in,
tr_interned_string client,
tr_peer_callback callback,
void* callback_data)
: tr_peerMsgs{ torrent_in, atom_in, client, io_in->is_encrypted(), io_in->is_incoming(), io_in->is_utp() }
, torrent{ torrent_in }
, io{ std::move(io_in) }
, have_{ torrent_in->piece_count() }
, callback_{ callback }
, callback_data_{ callback_data }
{
if (torrent->allows_pex())
{
pex_timer_ = session->timerMaker().create([this]() { sendPex(); });
pex_timer_->start_repeating(SendPexInterval);
}
if (io->supports_utp())
{
tr_peerMgrSetUtpSupported(torrent, io->address());
tr_peerMgrSetUtpFailed(torrent, io->address(), false);
}
if (io->supports_ltep())
{
sendLtepHandshake(this);
}
tellPeerWhatWeHave(this);
if (session->allowsDHT() && io->supports_dht())
{
// only send PORT over IPv6 iff IPv6 DHT is running (BEP-32).
if (auto const addr = session->publicAddress(TR_AF_INET6); !addr.is_any())
{
protocolSendPort(this, session->udpPort());
}
}
io->set_callbacks(canRead, didWrite, gotError, this);
updateDesiredRequestCount(this);
update_active();
}
tr_peerMsgsImpl(tr_peerMsgsImpl&&) = delete;
tr_peerMsgsImpl(tr_peerMsgsImpl const&) = delete;
tr_peerMsgsImpl& operator=(tr_peerMsgsImpl&&) = delete;
tr_peerMsgsImpl& operator=(tr_peerMsgsImpl const&) = delete;
~tr_peerMsgsImpl() override
{
set_active(TR_UP, false);
set_active(TR_DOWN, false);
if (this->io)
{
this->io->clear();
}
}
bool isTransferringPieces(uint64_t now, tr_direction dir, tr_bytes_per_second_t* setme_bytes_per_second) const override
{
auto const bytes_per_second = io->get_piece_speed_bytes_per_second(now, dir);
if (setme_bytes_per_second != nullptr)
{
*setme_bytes_per_second = bytes_per_second;
}
return bytes_per_second > 0;
}
[[nodiscard]] size_t activeReqCount(tr_direction dir) const noexcept override
{
switch (dir)
{
case TR_CLIENT_TO_PEER: // requests we sent
return tr_peerMgrCountActiveRequestsToPeer(torrent, this);
case TR_PEER_TO_CLIENT: // requests they sent
return std::size(peer_requested_);
default:
TR_ASSERT(0);
return {};
}
}
[[nodiscard]] tr_bandwidth& bandwidth() noexcept override
{
return io->bandwidth();
}
[[nodiscard]] std::pair<tr_address, tr_port> socketAddress() const override
{
return io->socket_address();
}
[[nodiscard]] std::string display_name() const override
{
auto const [addr, port] = socketAddress();
return addr.display_name(port);
}
[[nodiscard]] tr_bitfield const& has() const noexcept override
{
return have_;
}
void onTorrentGotMetainfo() noexcept override
{
invalidatePercentDone();
update_active();
}
void invalidatePercentDone()
{
updateInterest();
}
void cancel_block_request(tr_block_index_t block) override
{
protocolSendCancel(this, blockToReq(torrent, block));
}
void set_choke(bool peer_is_choked) override
{
time_t const now = tr_time();
time_t const fibrillation_time = now - MinChokePeriodSec;
if (chokeChangedAt > fibrillation_time)
{
// TODO logtrace(msgs, "Not changing choke to %d to avoid fibrillation", peer_is_choked);
}
else if (this->peer_is_choked() != peer_is_choked)
{
set_peer_choked(peer_is_choked);
if (peer_is_choked)
{
cancelAllRequestsToClient(this);
}
protocolSendChoke(this, peer_is_choked);
chokeChangedAt = now;
update_active(TR_CLIENT_TO_PEER);
}
}
void pulse() override
{
peerPulse(this);
}
void on_piece_completed(tr_piece_index_t piece) override
{
protocolSendHave(this, piece);
// since we have more pieces now, we might not be interested in this peer
updateInterest();
}
void set_interested(bool interested) override
{
if (client_is_interested() != interested)
{
set_client_interested(interested);
sendInterest(this, interested);
update_active(TR_PEER_TO_CLIENT);
}
}
void updateInterest()
{
// TODO -- might need to poke the mgr on startup
}
//
[[nodiscard]] bool isValidRequest(peer_request const& req) const
{
return tr_torrentReqIsValid(torrent, req.index, req.offset, req.length);
}
void requestBlocks(tr_block_span_t const* block_spans, size_t n_spans) override
{
TR_ASSERT(torrent->client_can_download());
TR_ASSERT(client_is_interested());
TR_ASSERT(!client_is_choked());
for (auto const *span = block_spans, *span_end = span + n_spans; span != span_end; ++span)
{
for (auto [block, block_end] = *span; block < block_end; ++block)
{
// Note that requests can't cross over a piece boundary.
// So if a piece isn't evenly divisible by the block size,
// we need to split our block request info per-piece chunks.
auto const byte_begin = torrent->block_loc(block).byte;
auto const block_size = torrent->block_size(block);
auto const byte_end = byte_begin + block_size;
for (auto offset = byte_begin; offset < byte_end;)
{
auto const loc = torrent->byte_loc(offset);
auto const left_in_block = block_size - loc.block_offset;
auto const left_in_piece = torrent->piece_size(loc.piece) - loc.piece_offset;
auto const req_len = std::min(left_in_block, left_in_piece);
protocolSendRequest(this, { loc.piece, loc.piece_offset, req_len });
offset += req_len;
}
}
tr_peerMgrClientSentRequests(torrent, this, *span);
}
}
// how many blocks could we request from this peer right now?
[[nodiscard]] RequestLimit canRequest() const noexcept override
{
auto const max_blocks = maxAvailableReqs();
return RequestLimit{ max_blocks, max_blocks };
}
void sendPex();
void publish(tr_peer_event const& peer_event)
{
if (callback_ != nullptr)
{
(*callback_)(this, peer_event, callback_data_);
}
}
private:
[[nodiscard]] size_t maxAvailableReqs() const
{
if (torrent->is_done() || !torrent->has_metainfo() || client_is_choked() || !client_is_interested())
{
return 0;
}
// Get the rate limit we should use.
// TODO: this needs to consider all the other peers as well...
uint64_t const now = tr_time_msec();
auto rate_bytes_per_second = get_piece_speed_bytes_per_second(now, TR_PEER_TO_CLIENT);
if (torrent->uses_speed_limit(TR_PEER_TO_CLIENT))
{
rate_bytes_per_second = std::min(rate_bytes_per_second, torrent->speed_limit_bps(TR_PEER_TO_CLIENT));
}
// honor the session limits, if enabled
if (torrent->uses_session_limits())
{
if (auto const irate_bytes_per_second = torrent->session->activeSpeedLimitBps(TR_PEER_TO_CLIENT);
irate_bytes_per_second)
{
rate_bytes_per_second = std::min(rate_bytes_per_second, *irate_bytes_per_second);
}
}
// use this desired rate to figure out how
// many requests we should send to this peer
size_t constexpr Floor = 32;
size_t constexpr Seconds = RequestBufSecs;
size_t const estimated_blocks_in_period = (rate_bytes_per_second * Seconds) / tr_block_info::BlockSize;
size_t const ceil = reqq ? *reqq : 250;
auto max_reqs = estimated_blocks_in_period;
max_reqs = std::min(max_reqs, ceil);
max_reqs = std::max(max_reqs, Floor);
return max_reqs;
}
[[nodiscard]] bool calculate_active(tr_direction direction) const
{
if (direction == TR_CLIENT_TO_PEER)
{
return peer_is_interested() && !peer_is_choked();
}
// TR_PEER_TO_CLIENT
if (!torrent->has_metainfo())
{
return true;
}
auto const active = client_is_interested() && !client_is_choked();
TR_ASSERT(!active || !torrent->is_done());
return active;
}
void update_active()
{
update_active(TR_UP);
update_active(TR_DOWN);
}
void update_active(tr_direction direction)
{
TR_ASSERT(tr_isDirection(direction));
set_active(direction, calculate_active(direction));
}
public:
bool peerSupportsPex = false;
bool peerSupportsMetadataXfer = false;
bool clientSentLtepHandshake = false;
bool peerSentLtepHandshake = false;
size_t desired_request_count = 0;
uint8_t ut_pex_id = 0;
uint8_t ut_metadata_id = 0;
tr_port dht_port;
EncryptionPreference encryption_preference = EncryptionPreference::Unknown;
size_t metadata_size_hint = 0;
tr_torrent* const torrent;
std::shared_ptr<tr_peerIo> const io;
struct QueuedPeerRequest : public peer_request
{
explicit QueuedPeerRequest(peer_request in) noexcept
: peer_request{ in }
{
}
bool prefetched = false;
};
std::vector<QueuedPeerRequest> peer_requested_;
std::vector<tr_pex> pex;
std::vector<tr_pex> pex6;
std::queue<int> peerAskedForMetadata;
time_t clientSentAnythingAt = 0;
time_t chokeChangedAt = 0;
/* when we started batching the outMessages */
// time_t outMessagesBatchedAt = 0;
struct tr_incoming incoming = {};
/* if the peer supports the Extension Protocol in BEP 10 and
supplied a reqq argument, it's stored here. */
std::optional<size_t> reqq;
std::unique_ptr<libtransmission::Timer> pex_timer_;
tr_bitfield have_;
private:
friend ReadResult process_peer_message(tr_peerMsgsImpl* msgs, uint8_t id, PeerMessageReader& payload);
friend void parseLtepHandshake(tr_peerMsgsImpl* msgs, PeerMessageReader& payload);
tr_peer_callback const callback_;
void* const callback_data_;
// seconds between periodic sendPex() calls
static auto constexpr SendPexInterval = 90s;
};
// ---
[[nodiscard]] constexpr bool messageLengthIsCorrect(tr_torrent const* const tor, uint8_t id, uint32_t len)
{
switch (id)
{
case BtPeerMsgs::Choke:
case BtPeerMsgs::Unchoke:
case BtPeerMsgs::Interested:
case BtPeerMsgs::NotInterested:
case BtPeerMsgs::FextHaveAll:
case BtPeerMsgs::FextHaveNone:
return len == 1U;
case BtPeerMsgs::Have:
case BtPeerMsgs::FextSuggest:
case BtPeerMsgs::FextAllowedFast:
return len == 5U;
case BtPeerMsgs::Bitfield:
return !tor->has_metainfo() || len == 1 + ((tor->piece_count() + 7U) / 8U);
case BtPeerMsgs::Request:
case BtPeerMsgs::Cancel:
case BtPeerMsgs::FextReject:
return len == 13U;
case BtPeerMsgs::Piece:
len -= sizeof(id) + sizeof(uint32_t /*piece*/) + sizeof(uint32_t /*offset*/);
return len <= tr_block_info::BlockSize;
case BtPeerMsgs::Port:
return len == 3U;
case BtPeerMsgs::Ltep:
return len >= 2U;
default: // unrecognized message
return false;
}
}
namespace protocol_send_message_helpers
{
namespace
{
[[nodiscard]] constexpr auto get_param_length(uint8_t param) noexcept
{
return sizeof(param);
}
[[nodiscard]] constexpr auto get_param_length(uint16_t param) noexcept
{
return sizeof(param);
}
[[nodiscard]] constexpr auto get_param_length(uint32_t param) noexcept
{
return sizeof(param);
}
template<typename T>
[[nodiscard]] TR_CONSTEXPR20 auto get_param_length(T const& param) noexcept
{
return std::size(param);
}
// ---
template<typename BufferWriter>
void add_param(BufferWriter& buffer, uint8_t param) noexcept
{
buffer.add_uint8(param);
}
template<typename BufferWriter>
void add_param(BufferWriter& buffer, uint16_t param) noexcept
{
buffer.add_uint16(param);
}
template<typename BufferWriter>
void add_param(BufferWriter& buffer, uint32_t param) noexcept
{
buffer.add_uint32(param);
}
template<typename BufferWriter, typename T>
void add_param(BufferWriter& buffer, T const& param) noexcept
{
buffer.add(param);
}
// ---
[[nodiscard]] std::string log_param(uint8_t param)
{
return fmt::format(" {:d}", static_cast<int>(param));
}
[[nodiscard]] std::string log_param(uint16_t param)
{
return fmt::format(" {:d}", static_cast<int>(param));
}
[[nodiscard]] std::string log_param(uint32_t param)
{
return fmt::format(" {:d}", static_cast<int>(param));
}
template<typename T>
[[nodiscard]] std::string log_param(T const& /*unused*/)
{
return " []";
}
template<typename... Args>
[[nodiscard]] std::string build_log_message(uint8_t type, Args const&... args)
{
auto text = fmt::format("sending '{:s}'", BtPeerMsgs::debug_name(type));
(text.append(log_param(args)), ...);
return text;
}
} // namespace
template<typename BufferWriter, typename... Args>
void build_peer_message(tr_peerMsgsImpl const* const msgs, BufferWriter& out, uint8_t type, Args const&... args)
{
logtrace(msgs, build_log_message(type, args...));
auto msg_len = sizeof(type);
((msg_len += get_param_length(args)), ...);
out.add_uint32(msg_len);
out.add_uint8(type);
(add_param(out, args), ...);
TR_ASSERT(messageLengthIsCorrect(msgs->torrent, type, msg_len));
}
} // namespace protocol_send_message_helpers
template<typename... Args>
size_t protocol_send_message(tr_peerMsgsImpl const* const msgs, uint8_t type, Args const&... args)
{
using namespace protocol_send_message_helpers;
auto out = PeerMessageBuffer{};
build_peer_message(msgs, out, type, args...);
auto const n_bytes_added = std::size(out);
msgs->io->write(out, type == BtPeerMsgs::Piece);
return n_bytes_added;
}
size_t protocol_send_keepalive(tr_peerMsgsImpl* msgs)
{
logtrace(msgs, "sending 'keepalive'");
auto out = libtransmission::Buffer{};
out.add_uint32(0);
auto const n_bytes_added = std::size(out);
msgs->io->write(out, false);
return n_bytes_added;
}
auto protocolSendReject(tr_peerMsgsImpl* const msgs, struct peer_request const* req)
{
TR_ASSERT(msgs->io->supports_fext());
return protocol_send_message(msgs, BtPeerMsgs::FextReject, req->index, req->offset, req->length);
}
size_t protocolSendCancel(tr_peerMsgsImpl* const msgs, peer_request const& req)
{
return protocol_send_message(msgs, BtPeerMsgs::Cancel, req.index, req.offset, req.length);
}
size_t protocolSendRequest(tr_peerMsgsImpl* const msgs, struct peer_request const& req)
{
TR_ASSERT(msgs->isValidRequest(req));
return protocol_send_message(msgs, BtPeerMsgs::Request, req.index, req.offset, req.length);
}
size_t protocolSendPort(tr_peerMsgsImpl* const msgs, tr_port port)
{
return protocol_send_message(msgs, BtPeerMsgs::Port, port.host());
}
size_t protocolSendHave(tr_peerMsgsImpl* const msgs, tr_piece_index_t index)
{
return protocol_send_message(msgs, BtPeerMsgs::Have, index);
}
size_t protocolSendChoke(tr_peerMsgsImpl* const msgs, bool choke)
{
return protocol_send_message(msgs, choke ? BtPeerMsgs::Choke : BtPeerMsgs::Unchoke);
}
// --- INTEREST
void sendInterest(tr_peerMsgsImpl* msgs, bool b)
{
protocol_send_message(msgs, b ? BtPeerMsgs::Interested : BtPeerMsgs::NotInterested);
}
std::optional<int> popNextMetadataRequest(tr_peerMsgsImpl* msgs)
{
auto& reqs = msgs->peerAskedForMetadata;
if (std::empty(reqs))
{
return {};
}
auto next = reqs.front();
reqs.pop();
return next;
}
void cancelAllRequestsToClient(tr_peerMsgsImpl* msgs)
{
if (auto const must_send_rej = msgs->io->supports_fext(); must_send_rej)
{
for (auto const& req : msgs->peer_requested_)
{
protocolSendReject(msgs, &req);
}
}
msgs->peer_requested_.clear();
}
// ---
void sendLtepHandshake(tr_peerMsgsImpl* msgs)
{
static tr_quark version_quark = 0;
if (msgs->clientSentLtepHandshake)
{
return;
}
if (version_quark == 0)
{
version_quark = tr_quark_new(TR_NAME " " USERAGENT_PREFIX);
}
logtrace(msgs, "sending an ltep handshake");
msgs->clientSentLtepHandshake = true;
/* decide if we want to advertise metadata xfer support (BEP 9) */
bool const allow_metadata_xfer = msgs->torrent->is_public();
/* decide if we want to advertise pex support */
auto allow_pex = bool{};
if (!msgs->torrent->allows_pex())
{
allow_pex = false;
}
else if (msgs->peerSentLtepHandshake)
{
allow_pex = msgs->peerSupportsPex;
}
else
{
allow_pex = true;
}
auto val = tr_variant{};
tr_variantInitDict(&val, 8);
tr_variantDictAddBool(&val, TR_KEY_e, msgs->session->encryptionMode() != TR_CLEAR_PREFERRED);
if (auto const addr = msgs->session->publicAddress(TR_AF_INET6); !addr.is_any())
{
TR_ASSERT(addr.is_ipv6());
tr_variantDictAddRaw(&val, TR_KEY_ipv6, &addr.addr.addr6, sizeof(addr.addr.addr6));
}
// http://bittorrent.org/beps/bep_0009.html
// It also adds "metadata_size" to the handshake message (not the
// "m" dictionary) specifying an integer value of the number of
// bytes of the metadata.
if (auto const info_dict_size = msgs->torrent->info_dict_size();
allow_metadata_xfer && msgs->torrent->has_metainfo() && info_dict_size > 0)
{
tr_variantDictAddInt(&val, TR_KEY_metadata_size, info_dict_size);
}
// http://bittorrent.org/beps/bep_0010.html
// Local TCP listen port. Allows each side to learn about the TCP
// port number of the other side. Note that there is no need for the
// receiving side of the connection to send this extension message,
// since its port number is already known.
tr_variantDictAddInt(&val, TR_KEY_p, msgs->session->advertisedPeerPort().host());
// http://bittorrent.org/beps/bep_0010.html
// An integer, the number of outstanding request messages this
// client supports without dropping any. The default in in
// libtorrent is 250.
tr_variantDictAddInt(&val, TR_KEY_reqq, ReqQ);
// https://www.bittorrent.org/beps/bep_0010.html
// A string containing the compact representation of the ip address this peer sees
// you as. i.e. this is the receiver's external ip address (no port is included).
// This may be either an IPv4 (4 bytes) or an IPv6 (16 bytes) address.
{
auto buf = std::array<std::byte, TR_ADDRSTRLEN>{};
auto const begin = std::data(buf);
auto const end = msgs->io->address().to_compact(begin);
auto const len = end - begin;
TR_ASSERT(len == 4 || len == 16);
tr_variantDictAddRaw(&val, TR_KEY_yourip, begin, len);
}
// http://bittorrent.org/beps/bep_0010.html
// Client name and version (as a utf-8 string). This is a much more
// reliable way of identifying the client than relying on the
// peer id encoding.
tr_variantDictAddQuark(&val, TR_KEY_v, version_quark);
// http://bittorrent.org/beps/bep_0021.html
// A peer that is a partial seed SHOULD include an extra header in
// the extension handshake 'upload_only'. Setting the value of this
// key to 1 indicates that this peer is not interested in downloading
// anything.
tr_variantDictAddBool(&val, TR_KEY_upload_only, msgs->torrent->is_done());
if (allow_metadata_xfer || allow_pex)
{
tr_variant* m = tr_variantDictAddDict(&val, TR_KEY_m, 2);
if (allow_metadata_xfer)
{
tr_variantDictAddInt(m, TR_KEY_ut_metadata, UT_METADATA_ID);
}
if (allow_pex)
{
tr_variantDictAddInt(m, TR_KEY_ut_pex, UT_PEX_ID);
}
}
protocol_send_message(msgs, BtPeerMsgs::Ltep, LtepMessages::Handshake, tr_variantToStr(&val, TR_VARIANT_FMT_BENC));
/* cleanup */
tr_variantClear(&val);
}
void parseLtepHandshake(tr_peerMsgsImpl* msgs, PeerMessageReader& payload)
{
msgs->peerSentLtepHandshake = true;
auto const handshake_sv = payload.to_string_view();
auto val = tr_variant{};
if (!tr_variantFromBuf(&val, TR_VARIANT_PARSE_BENC | TR_VARIANT_PARSE_INPLACE, handshake_sv) || !tr_variantIsDict(&val))
{
logtrace(msgs, "GET extended-handshake, couldn't get dictionary");
return;
}
logtrace(msgs, fmt::format(FMT_STRING("here is the base64-encoded handshake: [{:s}]"), tr_base64_encode(handshake_sv)));
/* does the peer prefer encrypted connections? */
auto i = int64_t{};
auto pex = tr_pex{};
if (tr_variantDictFindInt(&val, TR_KEY_e, &i))
{
msgs->encryption_preference = i != 0 ? EncryptionPreference::Yes : EncryptionPreference::No;
if (msgs->encryption_preference == EncryptionPreference::Yes)
{
pex.flags |= ADDED_F_ENCRYPTION_FLAG;
}
}
/* check supported messages for utorrent pex */
msgs->peerSupportsPex = false;
msgs->peerSupportsMetadataXfer = false;
if (tr_variant* sub = nullptr; tr_variantDictFindDict(&val, TR_KEY_m, &sub))
{
if (tr_variantDictFindInt(sub, TR_KEY_ut_pex, &i))
{
msgs->peerSupportsPex = i != 0;
msgs->ut_pex_id = (uint8_t)i;
logtrace(msgs, fmt::format(FMT_STRING("msgs->ut_pex is {:d}"), static_cast<int>(msgs->ut_pex_id)));
}
if (tr_variantDictFindInt(sub, TR_KEY_ut_metadata, &i))
{
msgs->peerSupportsMetadataXfer = i != 0;
msgs->ut_metadata_id = (uint8_t)i;
logtrace(msgs, fmt::format(FMT_STRING("msgs->ut_metadata_id is {:d}"), static_cast<int>(msgs->ut_metadata_id)));
}
if (tr_variantDictFindInt(sub, TR_KEY_ut_holepunch, &i))
{
/* Mysterious µTorrent extension that we don't grok. However,
it implies support for µTP, so use it to indicate that. */
tr_peerMgrSetUtpFailed(msgs->torrent, msgs->io->address(), false);
}
}
/* look for metainfo size (BEP 9) */
if (tr_variantDictFindInt(&val, TR_KEY_metadata_size, &i) && tr_torrentSetMetadataSizeHint(msgs->torrent, i))
{
msgs->metadata_size_hint = (size_t)i;
}
/* look for upload_only (BEP 21) */
if (tr_variantDictFindInt(&val, TR_KEY_upload_only, &i))
{
pex.flags |= ADDED_F_SEED_FLAG;
}
// http://bittorrent.org/beps/bep_0010.html
// Client name and version (as a utf-8 string). This is a much more
// reliable way of identifying the client than relying on the
// peer id encoding.
if (auto sv = std::string_view{}; tr_variantDictFindStrView(&val, TR_KEY_v, &sv))
{
msgs->set_user_agent(tr_interned_string{ sv });
}
/* get peer's listening port */
if (tr_variantDictFindInt(&val, TR_KEY_p, &i))
{
pex.port.setHost(i);
msgs->publish(tr_peer_event::GotPort(pex.port));
logtrace(msgs, fmt::format(FMT_STRING("peer's port is now {:d}"), i));
}
uint8_t const* addr = nullptr;
auto addr_len = size_t{};
if (msgs->io->is_incoming() && tr_variantDictFindRaw(&val, TR_KEY_ipv4, &addr, &addr_len) && addr_len == 4)
{
pex.addr.type = TR_AF_INET;
memcpy(&pex.addr.addr.addr4, addr, 4);
tr_peerMgrAddPex(msgs->torrent, TR_PEER_FROM_LTEP, &pex, 1);
}
if (msgs->io->is_incoming() && tr_variantDictFindRaw(&val, TR_KEY_ipv6, &addr, &addr_len) && addr_len == 16)
{
pex.addr.type = TR_AF_INET6;
memcpy(&pex.addr.addr.addr6, addr, 16);
tr_peerMgrAddPex(msgs->torrent, TR_PEER_FROM_LTEP, &pex, 1);
}
/* get peer's maximum request queue size */
if (tr_variantDictFindInt(&val, TR_KEY_reqq, &i))
{
msgs->reqq = i;
}
tr_variantClear(&val);
}
void parseUtMetadata(tr_peerMsgsImpl* msgs, PeerMessageReader& payload_in)
{
int64_t msg_type = -1;
int64_t piece = -1;
int64_t total_size = 0;
auto const tmp = payload_in.to_string_view();
auto const* const msg_end = std::data(tmp) + std::size(tmp);
auto dict = tr_variant{};
char const* benc_end = nullptr;
if (tr_variantFromBuf(&dict, TR_VARIANT_PARSE_BENC | TR_VARIANT_PARSE_INPLACE, tmp, &benc_end))
{
(void)tr_variantDictFindInt(&dict, TR_KEY_msg_type, &msg_type);
(void)tr_variantDictFindInt(&dict, TR_KEY_piece, &piece);
(void)tr_variantDictFindInt(&dict, TR_KEY_total_size, &total_size);
tr_variantClear(&dict);
}
logtrace(
msgs,
fmt::format(FMT_STRING("got ut_metadata msg: type {:d}, piece {:d}, total_size {:d}"), msg_type, piece, total_size));
if (msg_type == MetadataMsgType::Reject)
{
/* NOOP */
}
if (msg_type == MetadataMsgType::Data && !msgs->torrent->has_metainfo() && msg_end - benc_end <= METADATA_PIECE_SIZE &&
piece * METADATA_PIECE_SIZE + (msg_end - benc_end) <= total_size)
{
size_t const piece_len = msg_end - benc_end;
tr_torrentSetMetadataPiece(msgs->torrent, piece, benc_end, piece_len);
}
if (msg_type == MetadataMsgType::Request)
{
if (piece >= 0 && msgs->torrent->has_metainfo() && msgs->torrent->is_public() &&
std::size(msgs->peerAskedForMetadata) < MetadataReqQ)
{
msgs->peerAskedForMetadata.push(piece);
}
else
{
/* send a rejection message */
auto v = tr_variant{};
tr_variantInitDict(&v, 2);
tr_variantDictAddInt(&v, TR_KEY_msg_type, MetadataMsgType::Reject);
tr_variantDictAddInt(&v, TR_KEY_piece, piece);
protocol_send_message(msgs, BtPeerMsgs::Ltep, msgs->ut_metadata_id, tr_variantToStr(&v, TR_VARIANT_FMT_BENC));
tr_variantClear(&v);
}
}
}
void parseUtPex(tr_peerMsgsImpl* msgs, PeerMessageReader& payload)
{
auto* const tor = msgs->torrent;
if (!tor->allows_pex())
{
return;
}
auto const tmp = payload.to_string_view();
if (tr_variant val; tr_variantFromBuf(&val, TR_VARIANT_PARSE_BENC | TR_VARIANT_PARSE_INPLACE, tmp))
{
uint8_t const* added = nullptr;
auto added_len = size_t{};
if (tr_variantDictFindRaw(&val, TR_KEY_added, &added, &added_len))
{
uint8_t const* added_f = nullptr;
auto added_f_len = size_t{};
if (!tr_variantDictFindRaw(&val, TR_KEY_added_f, &added_f, &added_f_len))
{
added_f_len = 0;
added_f = nullptr;
}
auto pex = tr_pex::from_compact_ipv4(added, added_len, added_f, added_f_len);
pex.resize(std::min(MaxPexPeerCount, std::size(pex)));
tr_peerMgrAddPex(tor, TR_PEER_FROM_PEX, std::data(pex), std::size(pex));
}
if (tr_variantDictFindRaw(&val, TR_KEY_added6, &added, &added_len))
{
uint8_t const* added_f = nullptr;
auto added_f_len = size_t{};
if (!tr_variantDictFindRaw(&val, TR_KEY_added6_f, &added_f, &added_f_len))
{
added_f_len = 0;
added_f = nullptr;
}
auto pex = tr_pex::from_compact_ipv6(added, added_len, added_f, added_f_len);
pex.resize(std::min(MaxPexPeerCount, std::size(pex)));
tr_peerMgrAddPex(tor, TR_PEER_FROM_PEX, std::data(pex), std::size(pex));
}
tr_variantClear(&val);
}
}
void parseLtep(tr_peerMsgsImpl* msgs, PeerMessageReader& payload)
{
TR_ASSERT(!std::empty(payload));
auto const ltep_msgid = payload.to_uint8();
if (ltep_msgid == LtepMessages::Handshake)
{
logtrace(msgs, "got ltep handshake");
parseLtepHandshake(msgs, payload);
if (msgs->io->supports_ltep())
{
sendLtepHandshake(msgs);
msgs->sendPex();
}
}
else if (ltep_msgid == UT_PEX_ID)
{
logtrace(msgs, "got ut pex");
msgs->peerSupportsPex = true;
parseUtPex(msgs, payload);
}
else if (ltep_msgid == UT_METADATA_ID)
{
logtrace(msgs, "got ut metadata");
msgs->peerSupportsMetadataXfer = true;
parseUtMetadata(msgs, payload);
}
else
{
logtrace(msgs, fmt::format(FMT_STRING("skipping unknown ltep message ({:d})"), static_cast<int>(ltep_msgid)));
}
}
ReadResult process_peer_message(tr_peerMsgsImpl* msgs, uint8_t id, PeerMessageReader& payload);
void prefetchPieces(tr_peerMsgsImpl* msgs)
{
if (!msgs->session->allowsPrefetch())
{
return;
}
// ensure that the first `PrefetchMax` items in `msgs->peer_requested_` are prefetched.
auto& requests = msgs->peer_requested_;
for (size_t i = 0, n = std::min(PrefetchMax, std::size(requests)); i < n; ++i)
{
if (auto& req = requests[i]; !req.prefetched)
{
msgs->session->cache->prefetch_block(msgs->torrent, msgs->torrent->piece_loc(req.index, req.offset), req.length);
req.prefetched = true;
}
}
}
[[nodiscard]] bool canAddRequestFromPeer(tr_peerMsgsImpl const* const msgs, struct peer_request const& req)
{
if (msgs->peer_is_choked())
{
logtrace(msgs, "rejecting request from choked peer");
return false;
}
if (std::size(msgs->peer_requested_) >= ReqQ)
{
logtrace(msgs, "rejecting request ... reqq is full");
return false;
}
if (!tr_torrentReqIsValid(msgs->torrent, req.index, req.offset, req.length))
{
logtrace(msgs, "rejecting an invalid request.");
return false;
}
if (!msgs->torrent->has_piece(req.index))
{
logtrace(msgs, "rejecting request for a piece we don't have.");
return false;
}
return true;
}
void peerMadeRequest(tr_peerMsgsImpl* msgs, struct peer_request const* req)
{
if (canAddRequestFromPeer(msgs, *req))
{
msgs->peer_requested_.emplace_back(*req);
prefetchPieces(msgs);
}
else if (msgs->io->supports_fext())
{
protocolSendReject(msgs, req);
}
}
int clientGotBlock(tr_peerMsgsImpl* msgs, std::unique_ptr<Cache::BlockData> block_data, tr_block_index_t block);
ReadResult read_piece_data(tr_peerMsgsImpl* msgs, PeerMessageReader& payload)
{
// <index><begin><block>
auto const piece = payload.to_uint32();
auto const offset = payload.to_uint32();
auto const len = std::size(payload);
auto const loc = msgs->torrent->piece_loc(piece, offset);
auto const block = loc.block;
auto const block_size = msgs->torrent->block_size(block);
if (loc.block_offset + len > block_size)
{
logwarn(msgs, fmt::format("got unaligned piece {:d}:{:d}->{:d}", piece, offset, len));
return { READ_ERR, len };
}
if (!tr_peerMgrDidPeerRequest(msgs->torrent, msgs, block))
{
logwarn(msgs, fmt::format("got unrequested piece {:d}:{:d}->{:d}", piece, offset, len));
return { READ_ERR, len };
}
auto& blocks = msgs->incoming.blocks;
auto& incoming_block = blocks.try_emplace(block, block_size).first->second;
payload.to_buf(std::data(*incoming_block.buf) + loc.block_offset, len);
msgs->publish(tr_peer_event::GotPieceData(len));
if (!incoming_block.add_span(loc.block_offset, loc.block_offset + len))
{
return { READ_ERR, len }; // invalid span
}
logtrace(msgs, fmt::format("got {:d} bytes for req {:d}:{:d}->{:d}", len, piece, offset, len));
// if we haven't gotten the entire block yet, wait for more
if (!incoming_block.has_all())
{
return { READ_LATER, len };
}
// we've got the entire block, so send it along.
auto block_buf = std::move(incoming_block.buf);
blocks.erase(block); // note: invalidates `incoming_block` local
auto const ok = clientGotBlock(msgs, std::move(block_buf), block) == 0;
return { ok ? READ_NOW : READ_ERR, len };
}
ReadResult process_peer_message(tr_peerMsgsImpl* msgs, uint8_t id, PeerMessageReader& payload)
{
bool const fext = msgs->io->supports_fext();
auto ui32 = uint32_t{};
logtrace(
msgs,
fmt::format(
"got peer msg '{:s}' ({:d}) with payload len {:d}",
BtPeerMsgs::debug_name(id),
static_cast<int>(id),
std::size(payload)));
if (!messageLengthIsCorrect(msgs->torrent, id, sizeof(id) + std::size(payload)))
{
logdbg(
msgs,
fmt::format(
"bad msg: '{:s}' ({:d}) with payload len {:d}",
BtPeerMsgs::debug_name(id),
static_cast<int>(id),
std::size(payload)));
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
switch (id)
{
case BtPeerMsgs::Choke:
logtrace(msgs, "got Choke");
msgs->set_client_choked(true);
if (!fext)
{
msgs->publish(tr_peer_event::GotChoke());
}
msgs->update_active(TR_PEER_TO_CLIENT);
break;
case BtPeerMsgs::Unchoke:
logtrace(msgs, "got Unchoke");
msgs->set_client_choked(false);
msgs->update_active(TR_PEER_TO_CLIENT);
updateDesiredRequestCount(msgs);
break;
case BtPeerMsgs::Interested:
logtrace(msgs, "got Interested");
msgs->set_peer_interested(true);
msgs->update_active(TR_CLIENT_TO_PEER);
break;
case BtPeerMsgs::NotInterested:
logtrace(msgs, "got Not Interested");
msgs->set_peer_interested(false);
msgs->update_active(TR_CLIENT_TO_PEER);
break;
case BtPeerMsgs::Have:
ui32 = payload.to_uint32();
logtrace(msgs, fmt::format(FMT_STRING("got Have: {:d}"), ui32));
if (msgs->torrent->has_metainfo() && ui32 >= msgs->torrent->piece_count())
{
msgs->publish(tr_peer_event::GotError(ERANGE));
return { READ_ERR, {} };
}
/* a peer can send the same HAVE message twice... */
if (!msgs->have_.test(ui32))
{
msgs->have_.set(ui32);
msgs->publish(tr_peer_event::GotHave(ui32));
}
msgs->invalidatePercentDone();
break;
case BtPeerMsgs::Bitfield:
logtrace(msgs, "got a bitfield");
msgs->have_ = tr_bitfield{ msgs->torrent->has_metainfo() ? msgs->torrent->piece_count() : std::size(payload) * 8 };
msgs->have_.set_raw(reinterpret_cast<uint8_t const*>(std::data(payload)), std::size(payload));
msgs->publish(tr_peer_event::GotBitfield(&msgs->have_));
msgs->invalidatePercentDone();
break;
case BtPeerMsgs::Request:
{
struct peer_request r;
r.index = payload.to_uint32();
r.offset = payload.to_uint32();
r.length = payload.to_uint32();
logtrace(msgs, fmt::format(FMT_STRING("got Request: {:d}:{:d}->{:d}"), r.index, r.offset, r.length));
peerMadeRequest(msgs, &r);
break;
}
case BtPeerMsgs::Cancel:
{
struct peer_request r;
r.index = payload.to_uint32();
r.offset = payload.to_uint32();
r.length = payload.to_uint32();
msgs->cancels_sent_to_client.add(tr_time(), 1);
logtrace(msgs, fmt::format(FMT_STRING("got a Cancel {:d}:{:d}->{:d}"), r.index, r.offset, r.length));
auto& requests = msgs->peer_requested_;
if (auto iter = std::find(std::begin(requests), std::end(requests), r); iter != std::end(requests))
{
requests.erase(iter);
// bep6: "Even when a request is cancelled, the peer
// receiving the cancel should respond with either the
// corresponding reject or the corresponding piece"
if (fext)
{
protocolSendReject(msgs, &r);
}
}
break;
}
case BtPeerMsgs::Piece:
return read_piece_data(msgs, payload);
break;
case BtPeerMsgs::Port:
// http://bittorrent.org/beps/bep_0005.html
// Peers supporting the DHT set the last bit of the 8-byte reserved flags
// exchanged in the BitTorrent protocol handshake. Peer receiving a handshake
// indicating the remote peer supports the DHT should send a PORT message.
// It begins with byte 0x09 and has a two byte payload containing the UDP
// port of the DHT node in network byte order.
{
logtrace(msgs, "Got a BtPeerMsgs::Port");
auto const hport = payload.to_uint16();
if (auto const dht_port = tr_port::fromHost(hport); !std::empty(dht_port))
{
msgs->dht_port = dht_port;
msgs->session->addDhtNode(msgs->io->address(), msgs->dht_port);
}
}
break;
case BtPeerMsgs::FextSuggest:
logtrace(msgs, "Got a BtPeerMsgs::FextSuggest");
if (fext)
{
auto const piece = payload.to_uint32();
msgs->publish(tr_peer_event::GotSuggest(piece));
}
else
{
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
break;
case BtPeerMsgs::FextAllowedFast:
logtrace(msgs, "Got a BtPeerMsgs::FextAllowedFast");
if (fext)
{
auto const piece = payload.to_uint32();
msgs->publish(tr_peer_event::GotAllowedFast(piece));
}
else
{
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
break;
case BtPeerMsgs::FextHaveAll:
logtrace(msgs, "Got a BtPeerMsgs::FextHaveAll");
if (fext)
{
msgs->have_.set_has_all();
msgs->publish(tr_peer_event::GotHaveAll());
msgs->invalidatePercentDone();
}
else
{
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
break;
case BtPeerMsgs::FextHaveNone:
logtrace(msgs, "Got a BtPeerMsgs::FextHaveNone");
if (fext)
{
msgs->have_.set_has_none();
msgs->publish(tr_peer_event::GotHaveNone());
msgs->invalidatePercentDone();
}
else
{
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
break;
case BtPeerMsgs::FextReject:
{
struct peer_request r;
r.index = payload.to_uint32();
r.offset = payload.to_uint32();
r.length = payload.to_uint32();
if (fext)
{
msgs->publish(
tr_peer_event::GotRejected(msgs->torrent->block_info(), msgs->torrent->piece_loc(r.index, r.offset).block));
}
else
{
msgs->publish(tr_peer_event::GotError(EMSGSIZE));
return { READ_ERR, {} };
}
break;
}
case BtPeerMsgs::Ltep:
logtrace(msgs, "Got a BtPeerMsgs::Ltep");
parseLtep(msgs, payload);
break;
default:
logtrace(msgs, fmt::format(FMT_STRING("peer sent us an UNKNOWN: {:d}"), static_cast<int>(id)));
break;
}
return { READ_NOW, {} };
}
/* returns 0 on success, or an errno on failure */
int clientGotBlock(tr_peerMsgsImpl* msgs, std::unique_ptr<Cache::BlockData> block_data, tr_block_index_t const block)
{
TR_ASSERT(msgs != nullptr);
tr_torrent const* const tor = msgs->torrent;
auto const n_expected = msgs->torrent->block_size(block);
if (!block_data)
{
logdbg(msgs, fmt::format("wrong block size: expected {:d}, got {:d}", n_expected, 0));
return EMSGSIZE;
}
if (std::size(*block_data) != msgs->torrent->block_size(block))
{
logdbg(msgs, fmt::format("wrong block size: expected {:d}, got {:d}", n_expected, std::size(*block_data)));
return EMSGSIZE;
}
logtrace(msgs, fmt::format(FMT_STRING("got block {:d}"), block));
if (!tr_peerMgrDidPeerRequest(msgs->torrent, msgs, block))
{
logdbg(msgs, "we didn't ask for this message...");
return 0;
}
auto const loc = msgs->torrent->block_loc(block);
if (msgs->torrent->has_piece(loc.piece))
{
logtrace(msgs, "we did ask for this message, but the piece is already complete...");
return 0;
}
// NB: if writeBlock() fails the torrent may be paused.
// If this happens, `msgs` will be a dangling pointer and must no longer be used.
if (auto const err = msgs->session->cache->write_block(tor->id(), block, std::move(block_data)); err != 0)
{
return err;
}
msgs->blame.set(loc.piece);
msgs->publish(tr_peer_event::GotBlock(tor->block_info(), block));
return 0;
}
void didWrite(tr_peerIo* /*io*/, size_t bytes_written, bool was_piece_data, void* vmsgs)
{
auto* const msgs = static_cast<tr_peerMsgsImpl*>(vmsgs);
if (was_piece_data)
{
msgs->publish(tr_peer_event::SentPieceData(bytes_written));
}
peerPulse(msgs);
}
ReadState canRead(tr_peerIo* io, void* vmsgs, size_t* piece)
{
auto* msgs = static_cast<tr_peerMsgsImpl*>(vmsgs);
// https://www.bittorrent.org/beps/bep_0003.html
// Next comes an alternating stream of length prefixes and messages.
// Messages of length zero are keepalives, and ignored.
// All non-keepalive messages start with a single byte which gives their type.
//
// https://wiki.theory.org/BitTorrentSpecification
// All of the remaining messages in the protocol take the form of
// <length prefix><message ID><payload>. The length prefix is a four byte
// big-endian value. The message ID is a single decimal byte.
// The payload is message dependent.
// read <length prefix>
auto& current_message_len = msgs->incoming.length; // the full message payload length. Includes the +1 for id length
if (!current_message_len)
{
auto message_len = uint32_t{};
if (io->read_buffer_size() < sizeof(message_len))
{
return READ_LATER;
}
io->read_uint32(&message_len);
current_message_len = message_len;
// The keep-alive message is a message with zero bytes,
// specified with the length prefix set to zero.
// There is no message ID and no payload.
if (auto const is_keepalive = message_len == uint32_t{}; is_keepalive)
{
logtrace(msgs, "got KeepAlive");
current_message_len.reset();
return READ_NOW;
}
}
// read <message ID>
auto& current_message_type = msgs->incoming.id;
if (!current_message_type)
{
auto message_type = uint8_t{};
if (io->read_buffer_size() < sizeof(message_type))
{
return READ_LATER;
}
io->read_uint8(&message_type);
current_message_type = message_type;
}
// read <payload>
auto& current_payload = msgs->incoming.payload;
auto const full_payload_len = *current_message_len - sizeof(uint8_t /*message_type*/);
auto n_left = full_payload_len - std::size(current_payload);
while (n_left > 0U && io->read_buffer_size() > 0U)
{
auto buf = std::array<char, tr_block_info::BlockSize>{};
auto const n_this_pass = std::min({ n_left, io->read_buffer_size(), std::size(buf) });
io->read_bytes(std::data(buf), n_this_pass);
current_payload.add(std::data(buf), n_this_pass);
n_left -= n_this_pass;
logtrace(msgs, fmt::format("read {:d} payload bytes; {:d} left to go", n_this_pass, n_left));
}
if (n_left > 0U)
{
return READ_LATER;
}
// The incoming message is now complete. Reset the peerMsgs' incoming
// field so it's ready to receive the next message, then process the
// current one with `process_peer_message()`.
current_message_len.reset();
auto const message_type = *current_message_type;
current_message_type.reset();
auto payload = libtransmission::Buffer{};
std::swap(payload, current_payload);
auto const [read_state, n_piece_bytes_read] = process_peer_message(msgs, message_type, payload);
*piece = n_piece_bytes_read;
return read_state;
}
// ---
void updateDesiredRequestCount(tr_peerMsgsImpl* msgs)
{
msgs->desired_request_count = msgs->canRequest().max_blocks;
}
void updateMetadataRequests(tr_peerMsgsImpl* msgs, time_t now)
{
if (!msgs->peerSupportsMetadataXfer)
{
return;
}
if (auto const piece = tr_torrentGetNextMetadataRequest(msgs->torrent, now); piece)
{
auto tmp = tr_variant{};
tr_variantInitDict(&tmp, 3);
tr_variantDictAddInt(&tmp, TR_KEY_msg_type, MetadataMsgType::Request);
tr_variantDictAddInt(&tmp, TR_KEY_piece, *piece);
protocol_send_message(msgs, BtPeerMsgs::Ltep, msgs->ut_metadata_id, tr_variantToStr(&tmp, TR_VARIANT_FMT_BENC));
tr_variantClear(&tmp);
}
}
void updateBlockRequests(tr_peerMsgsImpl* msgs)
{
auto* const tor = msgs->torrent;
if (!tor->client_can_download())
{
return;
}
auto const n_active = tr_peerMgrCountActiveRequestsToPeer(tor, msgs);
if (n_active >= msgs->desired_request_count)
{
return;
}
auto const n_wanted = msgs->desired_request_count - n_active;
if (n_wanted == 0)
{
return;
}
TR_ASSERT(msgs->client_is_interested());
TR_ASSERT(!msgs->client_is_choked());
if (auto const requests = tr_peerMgrGetNextRequests(tor, msgs, n_wanted); !std::empty(requests))
{
msgs->requestBlocks(std::data(requests), std::size(requests));
}
}
namespace peer_pulse_helpers
{
[[nodiscard]] size_t add_next_metadata_piece(tr_peerMsgsImpl* msgs)
{
auto const piece = popNextMetadataRequest(msgs);
if (!piece.has_value()) // no pending requests
{
return {};
}
auto const data = tr_torrentGetMetadataPiece(msgs->torrent, *piece);
if (!data.has_value())
{
// send a reject
auto tmp = tr_variant{};
tr_variantInitDict(&tmp, 2);
tr_variantDictAddInt(&tmp, TR_KEY_msg_type, MetadataMsgType::Reject);
tr_variantDictAddInt(&tmp, TR_KEY_piece, *piece);
auto const n_bytes_written = protocol_send_message(
msgs,
BtPeerMsgs::Ltep,
msgs->ut_metadata_id,
tr_variantToStr(&tmp, TR_VARIANT_FMT_BENC));
tr_variantClear(&tmp);
return n_bytes_written;
}
// send the metadata
auto const data_sv = std::string_view{ reinterpret_cast<char const*>(std::data(*data)), std::size(*data) };
auto tmp = tr_variant{};
tr_variantInitDict(&tmp, 3);
tr_variantDictAddInt(&tmp, TR_KEY_msg_type, MetadataMsgType::Data);
tr_variantDictAddInt(&tmp, TR_KEY_piece, *piece);
tr_variantDictAddInt(&tmp, TR_KEY_total_size, msgs->torrent->info_dict_size());
auto const n_bytes_written = protocol_send_message(
msgs,
BtPeerMsgs::Ltep,
msgs->ut_metadata_id,
tr_variantToStr(&tmp, TR_VARIANT_FMT_BENC),
data_sv);
tr_variantClear(&tmp);
return n_bytes_written;
}
[[nodiscard]] size_t add_next_piece(tr_peerMsgsImpl* msgs, uint64_t now)
{
if (msgs->io->get_write_buffer_space(now) == 0U || std::empty(msgs->peer_requested_))
{
return {};
}
auto const req = msgs->peer_requested_.front();
msgs->peer_requested_.erase(std::begin(msgs->peer_requested_));
auto buf = std::array<uint8_t, tr_block_info::BlockSize>{};
auto ok = msgs->isValidRequest(req) && msgs->torrent->has_piece(req.index);
if (ok)
{
ok = msgs->torrent->ensure_piece_is_checked(req.index);
if (!ok)
{
msgs->torrent->set_local_error(
fmt::format(FMT_STRING("Please Verify Local Data! Piece #{:d} is corrupt."), req.index));
}
}
if (ok)
{
ok = msgs->session->cache
->read_block(msgs->torrent, msgs->torrent->piece_loc(req.index, req.offset), req.length, std::data(buf)) == 0;
}
if (ok)
{
auto const piece_data = std::string_view{ reinterpret_cast<char const*>(std::data(buf)), req.length };
return protocol_send_message(msgs, BtPeerMsgs::Piece, req.index, req.offset, piece_data);
}
if (msgs->io->supports_fext())
{
return protocolSendReject(msgs, &req);
}
return {};
}
[[nodiscard]] size_t fill_output_buffer(tr_peerMsgsImpl* msgs, time_t now)
{
auto n_bytes_written = size_t{};
// fulfuill metadata requests
for (;;)
{
auto const old_len = n_bytes_written;
n_bytes_written += add_next_metadata_piece(msgs);
if (old_len == n_bytes_written)
{
break;
}
}
// fulfuill piece requests
for (;;)
{
auto const old_len = n_bytes_written;
n_bytes_written += add_next_piece(msgs, now);
if (old_len == n_bytes_written)
{
break;
}
}
if (msgs != nullptr && msgs->clientSentAnythingAt != 0 && now - msgs->clientSentAnythingAt > KeepaliveIntervalSecs)
{
n_bytes_written += protocol_send_keepalive(msgs);
}
return n_bytes_written;
}
} // namespace peer_pulse_helpers
void peerPulse(void* vmsgs)
{
using namespace peer_pulse_helpers;
auto* msgs = static_cast<tr_peerMsgsImpl*>(vmsgs);
auto const now = tr_time();
updateDesiredRequestCount(msgs);
updateBlockRequests(msgs);
updateMetadataRequests(msgs, now);
for (;;)
{
if (fill_output_buffer(msgs, now) == 0U)
{
break;
}
}
}
void gotError(tr_peerIo* /*io*/, tr_error const& /*error*/, void* vmsgs)
{
static_cast<tr_peerMsgsImpl*>(vmsgs)->publish(tr_peer_event::GotError(ENOTCONN));
}
void tellPeerWhatWeHave(tr_peerMsgsImpl* msgs)
{
bool const fext = msgs->io->supports_fext();
if (fext && msgs->torrent->has_all())
{
protocol_send_message(msgs, BtPeerMsgs::FextHaveAll);
}
else if (fext && msgs->torrent->has_none())
{
protocol_send_message(msgs, BtPeerMsgs::FextHaveNone);
}
else if (!msgs->torrent->has_none())
{
protocol_send_message(msgs, BtPeerMsgs::Bitfield, msgs->torrent->create_piece_bitfield());
}
}
void tr_peerMsgsImpl::sendPex()
{
// only send pex if both the torrent and peer support it
if (!this->peerSupportsPex || !this->torrent->allows_pex())
{
return;
}
auto& old4 = this->pex;
auto new4 = tr_peerMgrGetPeers(this->torrent, TR_AF_INET, TR_PEERS_CONNECTED, MaxPexPeerCount);
auto added = std::vector<tr_pex>{};
added.reserve(std::size(new4));
std::set_difference(std::begin(new4), std::end(new4), std::begin(old4), std::end(old4), std::back_inserter(added));
auto dropped = std::vector<tr_pex>{};
dropped.reserve(std::size(old4));
std::set_difference(std::begin(old4), std::end(old4), std::begin(new4), std::end(new4), std::back_inserter(dropped));
auto& old6 = this->pex6;
auto new6 = tr_peerMgrGetPeers(this->torrent, TR_AF_INET6, TR_PEERS_CONNECTED, MaxPexPeerCount);
auto added6 = std::vector<tr_pex>{};
added6.reserve(std::size(new6));
std::set_difference(std::begin(new6), std::end(new6), std::begin(old6), std::end(old6), std::back_inserter(added6));
auto dropped6 = std::vector<tr_pex>{};
dropped6.reserve(std::size(old6));
std::set_difference(std::begin(old6), std::end(old6), std::begin(new6), std::end(new6), std::back_inserter(dropped6));
// Some peers give us error messages if we send
// more than this many peers in a single pex message.
// https://wiki.theory.org/BitTorrentPeerExchangeConventions
static auto constexpr MaxPexAdded = size_t{ 50 };
added.resize(std::min(std::size(added), MaxPexAdded));
added6.resize(std::min(std::size(added6), MaxPexAdded));
static auto constexpr MaxPexDropped = size_t{ 50 };
dropped.resize(std::min(std::size(dropped), MaxPexDropped));
dropped6.resize(std::min(std::size(dropped6), MaxPexDropped));
logtrace(
this,
fmt::format(
FMT_STRING("pex: old peer count {:d}+{:d}, new peer count {:d}+{:d}, added {:d}+{:d}, dropped {:d}+{:d}"),
std::size(old4),
std::size(old6),
std::size(new4),
std::size(new6),
std::size(added),
std::size(added6),
std::size(dropped),
std::size(dropped6)));
// if there's nothing to send, then we're done
if (std::empty(added) && std::empty(dropped) && std::empty(added6) && std::empty(dropped6))
{
return;
}
// update msgs
std::swap(old4, new4);
std::swap(old6, new6);
// build the pex payload
auto val = tr_variant{};
tr_variantInitDict(&val, 3); /* ipv6 support: left as 3: speed vs. likelihood? */
auto tmpbuf = std::vector<std::byte>{};
tmpbuf.reserve(MaxPexAdded * 18);
if (!std::empty(added))
{
// "added"
tmpbuf.clear();
tr_pex::to_compact_ipv4(std::back_inserter(tmpbuf), std::data(added), std::size(added));
TR_ASSERT(std::size(tmpbuf) == std::size(added) * 6);
tr_variantDictAddRaw(&val, TR_KEY_added, std::data(tmpbuf), std::size(tmpbuf));
// "added.f"
// unset each holepunch flag because we don't support it.
tmpbuf.resize(std::size(added));
auto* begin = std::data(tmpbuf);
auto* walk = begin;
for (auto const& p : added)
{
*walk++ = std::byte{ p.flags } & ~std::byte{ ADDED_F_HOLEPUNCH };
}
TR_ASSERT(static_cast<size_t>(walk - begin) == std::size(added));
tr_variantDictAddRaw(&val, TR_KEY_added_f, begin, walk - begin);
}
if (!std::empty(dropped))
{
// "dropped"
tmpbuf.clear();
tr_pex::to_compact_ipv4(std::back_inserter(tmpbuf), std::data(dropped), std::size(dropped));
TR_ASSERT(std::size(tmpbuf) == std::size(dropped) * 6);
tr_variantDictAddRaw(&val, TR_KEY_dropped, std::data(tmpbuf), std::size(tmpbuf));
}
if (!std::empty(added6))
{
tmpbuf.clear();
tr_pex::to_compact_ipv6(std::back_inserter(tmpbuf), std::data(added6), std::size(added6));
TR_ASSERT(std::size(tmpbuf) == std::size(added6) * 18);
tr_variantDictAddRaw(&val, TR_KEY_added6, std::data(tmpbuf), std::size(tmpbuf));
// "added6.f"
// unset each holepunch flag because we don't support it.
tmpbuf.resize(std::size(added6));
auto* begin = std::data(tmpbuf);
auto* walk = begin;
for (auto const& p : added6)
{
*walk++ = std::byte{ p.flags } & ~std::byte{ ADDED_F_HOLEPUNCH };
}
TR_ASSERT(static_cast<size_t>(walk - begin) == std::size(added6));
tr_variantDictAddRaw(&val, TR_KEY_added6_f, begin, walk - begin);
}
if (!std::empty(dropped6))
{
// "dropped6"
tmpbuf.clear();
tr_pex::to_compact_ipv6(std::back_inserter(tmpbuf), std::data(dropped6), std::size(dropped6));
TR_ASSERT(std::size(tmpbuf) == std::size(dropped6) * 18);
tr_variantDictAddRaw(&val, TR_KEY_dropped6, std::data(tmpbuf), std::size(tmpbuf));
}
protocol_send_message(this, BtPeerMsgs::Ltep, this->ut_pex_id, tr_variantToStr(&val, TR_VARIANT_FMT_BENC));
tr_variantClear(&val);
}
} // namespace
tr_peerMsgs::~tr_peerMsgs()
{
[[maybe_unused]] auto const n_prev = n_peers--;
TR_ASSERT(n_prev > 0U);
}
tr_peerMsgs* tr_peerMsgsNew(
tr_torrent* torrent,
peer_atom* atom,
std::shared_ptr<tr_peerIo> io,
tr_interned_string user_agent,
tr_peer_callback callback,
void* callback_data)
{
return new tr_peerMsgsImpl(torrent, atom, std::move(io), user_agent, callback, callback_data);
}
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