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transmission/libtransmission/peer-mgr.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 <atomic>
#include <cerrno> // error codes ERANGE, ...
#include <chrono>
#include <cmath>
#include <cstddef> // std::byte
#include <cstdint>
#include <ctime> // time_t
#include <iterator> // std::back_inserter
#include <map>
#include <memory>
#include <optional>
#include <tuple> // std::tie
#include <utility>
#include <vector>
#include <small/vector.hpp>
#include <fmt/core.h>
#define LIBTRANSMISSION_PEER_MODULE
#include "libtransmission/transmission.h"
#include "libtransmission/announcer.h"
#include "libtransmission/bandwidth.h"
#include "libtransmission/blocklist.h"
#include "libtransmission/cache.h"
#include "libtransmission/clients.h"
#include "libtransmission/completion.h"
#include "libtransmission/crypto-utils.h"
#include "libtransmission/handshake.h"
#include "libtransmission/interned-string.h"
#include "libtransmission/log.h"
#include "libtransmission/net.h"
#include "libtransmission/peer-io.h"
#include "libtransmission/peer-mgr-active-requests.h"
#include "libtransmission/peer-mgr-wishlist.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-macros.h"
#include "libtransmission/tr-utp.h"
#include "libtransmission/utils.h"
#include "libtransmission/webseed.h"
using namespace std::literals;
static auto constexpr CancelHistorySec = int{ 60 };
// ---
class HandshakeMediator final : public tr_handshake::Mediator
{
private:
[[nodiscard]] static std::optional<TorrentInfo> torrent(tr_torrent* tor)
{
if (tor == nullptr)
{
return {};
}
auto info = TorrentInfo{};
info.info_hash = tor->info_hash();
info.client_peer_id = tor->peer_id();
info.id = tor->id();
info.is_done = tor->is_done();
return info;
}
public:
explicit HandshakeMediator(tr_session& session) noexcept
: session_{ session }
{
}
[[nodiscard]] std::optional<TorrentInfo> torrent(tr_sha1_digest_t const& info_hash) const override
{
return torrent(session_.torrents().get(info_hash));
}
[[nodiscard]] std::optional<TorrentInfo> torrent_from_obfuscated(tr_sha1_digest_t const& info_hash) const override
{
return torrent(tr_torrentFindFromObfuscatedHash(&session_, info_hash));
}
[[nodiscard]] bool allows_dht() const override
{
return session_.allowsDHT();
}
[[nodiscard]] bool allows_tcp() const override
{
return session_.allowsTCP();
}
void set_utp_failed(tr_sha1_digest_t const& info_hash, tr_socket_address const& socket_address) override
{
if (auto* const tor = session_.torrents().get(info_hash); tor != nullptr)
{
tr_peerMgrSetUtpFailed(tor, socket_address, true);
}
}
[[nodiscard]] bool is_peer_known_seed(tr_torrent_id_t tor_id, tr_socket_address const& socket_address) const override;
[[nodiscard]] libtransmission::TimerMaker& timer_maker() override
{
return session_.timerMaker();
}
[[nodiscard]] size_t pad(void* setme, size_t maxlen) const override
{
auto const len = tr_rand_int(maxlen);
tr_rand_buffer(setme, len);
return len;
}
private:
tr_session& session_;
};
/**
* Peer information that should be kept even before we've connected and
* after we've disconnected. These are kept in a pool of peer_atoms to decide
* which ones would make good candidates for connecting to, and to watch out
* for banned peers.
*
* @see tr_peer
* @see tr_peerMsgs
*/
struct peer_atom
{
peer_atom(tr_socket_address socket_address_in, uint8_t flags_in, uint8_t from)
: socket_address{ std::move(socket_address_in) }
, fromFirst{ from }
, fromBest{ from }
, flags{ flags_in }
{
++n_atoms;
}
peer_atom(peer_atom&&) = delete;
peer_atom(peer_atom const&) = delete;
peer_atom& operator=(peer_atom&&) = delete;
peer_atom& operator=(peer_atom const&) = delete;
~peer_atom()
{
[[maybe_unused]] auto const n_prev = n_atoms--;
TR_ASSERT(n_prev > 0U);
}
[[nodiscard]] static auto atom_count() noexcept
{
return n_atoms.load();
}
[[nodiscard]] constexpr auto isSeed() const noexcept
{
return (flags & ADDED_F_SEED_FLAG) != 0;
}
[[nodiscard]] constexpr auto const& addr() const noexcept
{
return socket_address.first;
}
[[nodiscard]] constexpr auto& port() noexcept
{
return socket_address.second;
}
[[nodiscard]] constexpr auto const& port() const noexcept
{
return socket_address.second;
}
[[nodiscard]] auto display_name() const
{
return addr().display_name(port());
}
[[nodiscard]] bool isBlocklisted(tr_session const* session) const
{
if (blocklisted_)
{
return *blocklisted_;
}
auto const value = session->addressIsBlocked(addr());
blocklisted_ = value;
return value;
}
[[nodiscard]] constexpr auto is_unreachable() const noexcept
{
return is_unreachable_;
}
constexpr void set_unreachable() noexcept
{
is_unreachable_ = true;
}
constexpr void set_reachable() noexcept
{
is_unreachable_ = false;
}
[[nodiscard]] constexpr int getReconnectIntervalSecs(time_t const now) const noexcept
{
auto sec = int{};
auto const unreachable = is_unreachable();
/* if we were recently connected to this peer and transferring piece
* data, try to reconnect to them sooner rather that later -- we don't
* want network troubles to get in the way of a good peer. */
if (!unreachable && now - this->piece_data_time <= MinimumReconnectIntervalSecs * 2)
{
sec = MinimumReconnectIntervalSecs;
}
/* otherwise, the interval depends on how many times we've tried
* and failed to connect to the peer */
else
{
auto step = this->num_fails;
/* penalize peers that were unreachable the last time we tried */
if (unreachable)
{
step += 2;
}
switch (step)
{
case 0:
sec = 0;
break;
case 1:
sec = 10;
break;
case 2:
sec = 60 * 2;
break;
case 3:
sec = 60 * 15;
break;
case 4:
sec = 60 * 30;
break;
case 5:
sec = 60 * 60;
break;
default:
sec = 60 * 120;
break;
}
}
return sec;
}
void setBlocklistedDirty()
{
blocklisted_.reset();
}
[[nodiscard]] constexpr auto is_banned() const noexcept
{
return is_banned_;
}
constexpr void ban() noexcept
{
is_banned_ = true;
}
tr_socket_address socket_address;
uint16_t num_fails = {};
time_t time = {}; /* when the peer's connection status last changed */
time_t piece_data_time = {};
time_t lastConnectionAttemptAt = {};
time_t lastConnectionAt = {};
uint8_t const fromFirst; /* where the peer was first found */
uint8_t fromBest; /* the "best" value of where the peer has been found */
uint8_t flags = {}; /* these match the added_f flags */
uint8_t flags2 = {}; /* flags that aren't defined in added_f */
bool utp_failed = false; /* We recently failed to connect over µTP */
bool is_connected = false;
private:
// the minimum we'll wait before attempting to reconnect to a peer
static auto constexpr MinimumReconnectIntervalSecs = int{ 5 };
static auto inline n_atoms = std::atomic<size_t>{};
mutable std::optional<bool> blocklisted_;
bool is_banned_ = false;
bool is_unreachable_ = false; // we tried to connect & failed
};
using Handshakes = std::map<tr_socket_address, tr_handshake>;
#define tr_logAddDebugSwarm(swarm, msg) tr_logAddDebugTor((swarm)->tor, msg)
#define tr_logAddTraceSwarm(swarm, msg) tr_logAddTraceTor((swarm)->tor, msg)
/** @brief Opaque, per-torrent data structure for peer connection information */
class tr_swarm
{
public:
[[nodiscard]] auto unique_lock() const
{
return tor->unique_lock();
}
tr_swarm(tr_peerMgr* manager_in, tr_torrent* tor_in) noexcept
: manager{ manager_in }
, tor{ tor_in }
, tags_{ {
tor_in->done_.observe([this](tr_torrent*, bool) { on_torrent_done(); }),
tor_in->doomed_.observe([this](tr_torrent*) { on_torrent_doomed(); }),
tor_in->got_bad_piece_.observe([this](tr_torrent*, tr_piece_index_t p) { on_got_bad_piece(p); }),
tor_in->got_metainfo_.observe([this](tr_torrent*) { on_got_metainfo(); }),
tor_in->piece_completed_.observe([this](tr_torrent*, tr_piece_index_t p) { on_piece_completed(p); }),
tor_in->started_.observe([this](tr_torrent*) { on_torrent_started(); }),
tor_in->stopped_.observe([this](tr_torrent*) { on_torrent_stopped(); }),
tor_in->swarm_is_all_seeds_.observe([this](tr_torrent* /*tor*/) { on_swarm_is_all_seeds(); }),
} }
{
rebuildWebseeds();
}
tr_swarm(tr_swarm&&) = delete;
tr_swarm(tr_swarm const&) = delete;
tr_swarm& operator=(tr_swarm&&) = delete;
tr_swarm& operator=(tr_swarm const&) = delete;
~tr_swarm()
{
auto const lock = unique_lock();
TR_ASSERT(!is_running);
TR_ASSERT(std::empty(outgoing_handshakes));
TR_ASSERT(std::empty(peers));
}
[[nodiscard]] bool peer_is_in_use(peer_atom const& atom) const;
void cancelOldRequests()
{
auto const now = tr_time();
auto const oldest = now - RequestTtlSecs;
for (auto const& [block, peer] : active_requests.sentBefore(oldest))
{
maybeSendCancelRequest(peer, block, nullptr);
active_requests.remove(block, peer);
}
}
void cancelAllRequestsForBlock(tr_block_index_t block, tr_peer const* no_notify)
{
for (auto* peer : active_requests.remove(block))
{
maybeSendCancelRequest(peer, block, no_notify);
}
}
[[nodiscard]] uint16_t countActiveWebseeds(uint64_t now) const noexcept
{
if (!tor->is_running() || tor->is_done())
{
return {};
}
return std::count_if(
std::begin(webseeds),
std::end(webseeds),
[&now](auto const& webseed) { return webseed->isTransferringPieces(now, TR_DOWN, nullptr); });
}
[[nodiscard]] TR_CONSTEXPR20 auto peerCount() const noexcept
{
return std::size(peers);
}
void stop()
{
auto const lock = unique_lock();
is_running = false;
removeAllPeers();
outgoing_handshakes.clear();
}
void removePeer(tr_peer* peer)
{
auto const lock = unique_lock();
auto* const atom = peer->atom;
TR_ASSERT(atom != nullptr);
atom->time = tr_time();
if (auto iter = std::find(std::begin(peers), std::end(peers), peer); iter != std::end(peers))
{
peers.erase(iter);
}
--stats.peer_count;
--stats.peer_from_count[atom->fromFirst];
TR_ASSERT(stats.peer_count == peerCount());
delete peer;
}
void removeAllPeers()
{
auto tmp = peers;
for (auto* peer : tmp)
{
removePeer(peer);
}
TR_ASSERT(stats.peer_count == 0);
}
void updateEndgame()
{
/* we consider ourselves to be in endgame if the number of bytes
we've got requested is >= the number of bytes left to download */
is_endgame_ = uint64_t(std::size(active_requests)) * tr_block_info::BlockSize >= tor->left_until_done();
}
[[nodiscard]] constexpr auto isEndgame() const noexcept
{
return is_endgame_;
}
void addStrike(tr_peer* peer) const
{
tr_logAddTraceSwarm(
this,
fmt::format("increasing peer {} strike count to {}", peer->display_name(), peer->strikes + 1));
if (++peer->strikes >= MaxBadPiecesPerPeer)
{
peer->atom->ban();
peer->do_purge = true;
tr_logAddTraceSwarm(this, fmt::format("banning peer {}", peer->display_name()));
}
}
void rebuildWebseeds()
{
auto const n = tor->webseed_count();
webseeds.clear();
webseeds.reserve(n);
for (size_t i = 0; i < n; ++i)
{
webseeds.emplace_back(tr_webseedNew(tor, tor->webseed(i), &tr_swarm::peerCallbackFunc, this));
}
webseeds.shrink_to_fit();
stats.active_webseed_count = 0;
}
[[nodiscard]] TR_CONSTEXPR20 auto isAllSeeds() const noexcept
{
if (!pool_is_all_seeds_)
{
pool_is_all_seeds_ = std::all_of(
std::begin(pool),
std::end(pool),
[](auto const& key_val) { return key_val.second.isSeed(); });
}
return *pool_is_all_seeds_;
}
[[nodiscard]] peer_atom* get_existing_atom(tr_socket_address const& socket_address) noexcept
{
auto&& it = pool.find(socket_address);
return it != pool.end() ? &it->second : nullptr;
}
[[nodiscard]] peer_atom const* get_existing_atom(tr_socket_address const& socket_address) const noexcept
{
auto const& it = pool.find(socket_address);
return it != pool.cend() ? &it->second : nullptr;
}
[[nodiscard]] bool peer_is_a_seed(tr_socket_address const& socket_address) const noexcept
{
auto const* const atom = get_existing_atom(socket_address);
return atom != nullptr && atom->isSeed();
}
peer_atom* ensure_atom_exists(tr_socket_address const& socket_address, uint8_t const flags, uint8_t const from)
{
TR_ASSERT(socket_address.first.is_valid());
TR_ASSERT(from < TR_PEER_FROM__MAX);
auto&& [atom_it, is_new] = pool.try_emplace(socket_address, socket_address, flags, from);
peer_atom* atom = &atom_it->second;
if (!is_new)
{
atom->fromBest = std::min(atom->fromBest, from);
atom->flags |= flags;
}
mark_all_seeds_flag_dirty();
return atom;
}
void mark_atom_as_seed(peer_atom& atom)
{
tr_logAddTraceSwarm(this, fmt::format("marking peer {} as a seed", atom.display_name()));
atom.flags |= ADDED_F_SEED_FLAG;
mark_all_seeds_flag_dirty();
}
static void peerCallbackFunc(tr_peer* peer, tr_peer_event const& event, void* vs)
{
TR_ASSERT(peer != nullptr);
auto* s = static_cast<tr_swarm*>(vs);
auto const lock = s->unique_lock();
switch (event.type)
{
case tr_peer_event::Type::ClientSentPieceData:
{
auto const now = tr_time();
auto* const tor = s->tor;
tor->uploadedCur += event.length;
tr_announcerAddBytes(tor, TR_ANN_UP, event.length);
tor->set_date_active(now);
tor->set_dirty();
tor->session->add_uploaded(event.length);
if (peer->atom != nullptr)
{
peer->atom->piece_data_time = now;
}
break;
}
case tr_peer_event::Type::ClientGotPieceData:
{
auto const now = tr_time();
auto* const tor = s->tor;
tor->downloadedCur += event.length;
tor->set_date_active(now);
tor->set_dirty();
tor->session->add_downloaded(event.length);
if (peer->atom != nullptr)
{
peer->atom->piece_data_time = now;
}
break;
}
case tr_peer_event::Type::ClientGotHave:
case tr_peer_event::Type::ClientGotHaveAll:
case tr_peer_event::Type::ClientGotHaveNone:
case tr_peer_event::Type::ClientGotBitfield:
/* TODO: if we don't need these, should these events be removed? */
/* noop */
break;
case tr_peer_event::Type::ClientGotRej:
s->active_requests.remove(s->tor->piece_loc(event.pieceIndex, event.offset).block, peer);
break;
case tr_peer_event::Type::ClientGotChoke:
s->active_requests.remove(peer);
break;
case tr_peer_event::Type::ClientGotPort:
if (peer->atom != nullptr)
{
peer->atom->port() = event.port;
}
break;
case tr_peer_event::Type::ClientGotSuggest:
case tr_peer_event::Type::ClientGotAllowedFast:
// not currently supported
break;
case tr_peer_event::Type::ClientGotBlock:
{
auto* const tor = s->tor;
auto const loc = tor->piece_loc(event.pieceIndex, event.offset);
s->cancelAllRequestsForBlock(loc.block, peer);
peer->blocks_sent_to_client.add(tr_time(), 1);
tr_torrentGotBlock(tor, loc.block);
break;
}
case tr_peer_event::Type::Error:
if (event.err == ERANGE || event.err == EMSGSIZE || event.err == ENOTCONN)
{
/* some protocol error from the peer */
peer->do_purge = true;
tr_logAddDebugSwarm(
s,
fmt::format(
"setting {} do_purge flag because we got an ERANGE, EMSGSIZE, or ENOTCONN error",
peer->display_name()));
}
else
{
tr_logAddDebugSwarm(s, fmt::format("unhandled error: {}", tr_strerror(event.err)));
}
break;
}
}
Handshakes outgoing_handshakes;
mutable tr_swarm_stats stats = {};
uint8_t optimistic_unchoke_time_scaler = 0;
bool is_running = false;
tr_peerMgr* const manager;
tr_torrent* const tor;
ActiveRequests active_requests;
// depends-on: active_requests
std::vector<std::unique_ptr<tr_peer>> webseeds;
// depends-on: active_requests
std::vector<tr_peerMsgs*> peers;
// tr_peers hold pointers to the items in this container,
// therefore references to elements within cannot invalidate
std::map<tr_socket_address, peer_atom> pool;
tr_peerMsgs* optimistic = nullptr; /* the optimistic peer, or nullptr if none */
time_t lastCancel = 0;
private:
static void maybeSendCancelRequest(tr_peer* peer, tr_block_index_t block, tr_peer const* muted)
{
auto* msgs = dynamic_cast<tr_peerMsgs*>(peer);
if (msgs != nullptr && msgs != muted)
{
peer->cancels_sent_to_peer.add(tr_time(), 1);
msgs->cancel_block_request(block);
}
}
void mark_all_seeds_flag_dirty() noexcept
{
pool_is_all_seeds_.reset();
}
void on_torrent_doomed()
{
auto const lock = tor->unique_lock();
stop();
tor->swarm = nullptr;
delete this;
}
void on_torrent_done()
{
std::for_each(std::begin(peers), std::end(peers), [](auto* const peer) { peer->set_interested(false); });
}
void on_swarm_is_all_seeds()
{
auto const lock = tor->unique_lock();
for (auto& [socket_address, atom] : pool)
{
mark_atom_as_seed(atom);
}
mark_all_seeds_flag_dirty();
}
void on_piece_completed(tr_piece_index_t piece)
{
bool piece_came_from_peers = false;
for (auto* const peer : peers)
{
// notify the peer that we now have this piece
peer->on_piece_completed(piece);
if (!piece_came_from_peers)
{
piece_came_from_peers = peer->blame.test(piece);
}
}
if (piece_came_from_peers) /* webseed downloads don't belong in announce totals */
{
tr_announcerAddBytes(tor, TR_ANN_DOWN, tor->piece_size(piece));
}
}
void on_got_bad_piece(tr_piece_index_t piece)
{
auto const byte_count = tor->piece_size(piece);
for (auto* const peer : peers)
{
if (peer->blame.test(piece))
{
tr_logAddTraceSwarm(
this,
fmt::format(
"peer {} contributed to corrupt piece ({}); now has {} strikes",
peer->display_name(),
piece,
peer->strikes + 1));
addStrike(peer);
}
}
tr_announcerAddBytes(tor, TR_ANN_CORRUPT, byte_count);
}
void on_got_metainfo()
{
// the webseed list may have changed...
rebuildWebseeds();
// some peer_msgs' progress fields may not be accurate if we
// didn't have the metadata before now... so refresh them all...
for (auto* peer : peers)
{
peer->onTorrentGotMetainfo();
if (peer->isSeed())
{
mark_atom_as_seed(*peer->atom);
}
}
}
void on_torrent_started();
void on_torrent_stopped();
// number of bad pieces a peer is allowed to send before we ban them
static auto constexpr MaxBadPiecesPerPeer = int{ 5 };
// how long we'll let requests we've made linger before we cancel them
static auto constexpr RequestTtlSecs = int{ 90 };
std::array<libtransmission::ObserverTag, 8> const tags_;
mutable std::optional<bool> pool_is_all_seeds_;
bool is_endgame_ = false;
};
struct tr_peerMgr
{
private:
static auto constexpr BandwidthTimerPeriod = 500ms;
static auto constexpr RechokePeriod = 10s;
static auto constexpr RefillUpkeepPeriod = 10s;
// Max number of outbound peer connections to initiate.
// This throttle is an arbitrary number to avoid overloading routers.
static auto constexpr MaxConnectionsPerSecond = size_t{ 18U };
static auto constexpr MaxConnectionsPerPulse = size_t(MaxConnectionsPerSecond * BandwidthTimerPeriod / 1s);
// Building a peer candidate list is expensive, so cache it across pulses.
// We want to cache it long enough to avoid excess CPU cycles,
// but short enough that the data isn't too stale.
static auto constexpr OutboundCandidatesListTtl = BandwidthTimerPeriod * 4U;
// How big the candidate list should be when we create it.
static auto constexpr OutboundCandidateListCapacity = MaxConnectionsPerPulse * OutboundCandidatesListTtl /
BandwidthTimerPeriod;
public:
// The peers we might try connecting to in the next few seconds.
// This list is cached between pulses so use resilient keys, e.g.
// a `tr_torrent_id_t` instead of a `tr_torrent*` that can be freed.
using OutboundCandidates = small::
max_size_vector<std::pair<tr_torrent_id_t, tr_socket_address>, OutboundCandidateListCapacity>;
explicit tr_peerMgr(tr_session* session_in)
: session{ session_in }
, handshake_mediator_{ *session }
, bandwidth_timer_{ session->timerMaker().create([this]() { bandwidthPulse(); }) }
, rechoke_timer_{ session->timerMaker().create([this]() { rechokePulseMarshall(); }) }
, refill_upkeep_timer_{ session->timerMaker().create([this]() { refillUpkeep(); }) }
, blocklist_tag_{ session->blocklist_changed_.observe([this]() { on_blocklist_changed(); }) }
{
bandwidth_timer_->start_repeating(BandwidthTimerPeriod);
rechoke_timer_->start_repeating(RechokePeriod);
refill_upkeep_timer_->start_repeating(RefillUpkeepPeriod);
}
tr_peerMgr(tr_peerMgr&&) = delete;
tr_peerMgr(tr_peerMgr const&) = delete;
tr_peerMgr& operator=(tr_peerMgr&&) = delete;
tr_peerMgr& operator=(tr_peerMgr const&) = delete;
[[nodiscard]] auto unique_lock() const
{
return session->unique_lock();
}
~tr_peerMgr()
{
auto const lock = unique_lock();
incoming_handshakes.clear();
}
void rechokeSoon() noexcept
{
rechoke_timer_->set_interval(100ms);
}
void bandwidthPulse();
void rechokePulse() const;
void reconnectPulse();
void refillUpkeep() const;
void make_new_peer_connections();
[[nodiscard]] tr_swarm* get_existing_swarm(tr_sha1_digest_t const& hash) const
{
auto* const tor = session->torrents().get(hash);
return tor == nullptr ? nullptr : tor->swarm;
}
tr_session* const session;
Handshakes incoming_handshakes;
HandshakeMediator handshake_mediator_;
private:
void rechokePulseMarshall()
{
rechokePulse();
rechoke_timer_->set_interval(RechokePeriod);
}
void on_blocklist_changed() const
{
/* we cache whether or not a peer is blocklisted...
since the blocklist has changed, erase that cached value */
for (auto* const tor : session->torrents())
{
for (auto& [socket_address, atom] : tor->swarm->pool)
{
atom.setBlocklistedDirty();
}
}
}
OutboundCandidates outbound_candidates_;
std::unique_ptr<libtransmission::Timer> const bandwidth_timer_;
std::unique_ptr<libtransmission::Timer> const rechoke_timer_;
std::unique_ptr<libtransmission::Timer> const refill_upkeep_timer_;
libtransmission::ObserverTag const blocklist_tag_;
};
// --- tr_peer virtual functions
tr_peer::tr_peer(tr_torrent const* tor, peer_atom* atom_in)
: session{ tor->session }
, swarm{ tor->swarm }
, atom{ atom_in }
, blame{ tor->block_count() }
{
}
tr_peer::~tr_peer()
{
if (swarm != nullptr)
{
swarm->active_requests.remove(this);
}
if (atom != nullptr)
{
atom->is_connected = false;
}
}
// ---
tr_peerMgr* tr_peerMgrNew(tr_session* session)
{
return new tr_peerMgr{ session };
}
void tr_peerMgrFree(tr_peerMgr* manager)
{
delete manager;
}
// ---
void tr_peerMgrSetUtpSupported(tr_torrent* tor, tr_socket_address const& socket_address)
{
if (auto* const atom = tor->swarm->get_existing_atom(socket_address); atom != nullptr)
{
atom->flags |= ADDED_F_UTP_FLAGS;
}
}
void tr_peerMgrSetUtpFailed(tr_torrent* tor, tr_socket_address const& socket_address, bool failed)
{
if (auto* const atom = tor->swarm->get_existing_atom(socket_address); atom != nullptr)
{
atom->utp_failed = failed;
}
}
/**
* REQUESTS
*
* There are two data structures associated with managing block requests:
*
* 1. tr_swarm::active_requests, an opaque class that tracks what requests
* we currently have, i.e. which blocks and from which peers.
* This is used for cancelling requests that have been waiting
* for too long and avoiding duplicate requests.
*
* 2. tr_swarm::pieces, an array of "struct weighted_piece" which lists the
* pieces that we want to request. It's used to decide which blocks to
* return next when tr_peerMgrGetBlockRequests() is called.
*/
// --- struct block_request
// TODO: if we keep this, add equivalent API to ActiveRequest
void tr_peerMgrClientSentRequests(tr_torrent* torrent, tr_peer* peer, tr_block_span_t span)
{
auto const now = tr_time();
for (tr_block_index_t block = span.begin; block < span.end; ++block)
{
torrent->swarm->active_requests.add(block, peer, now);
}
}
std::vector<tr_block_span_t> tr_peerMgrGetNextRequests(tr_torrent* torrent, tr_peer const* peer, size_t numwant)
{
class MediatorImpl final : public Wishlist::Mediator
{
public:
MediatorImpl(tr_torrent const* torrent_in, tr_peer const* peer_in)
: torrent_{ torrent_in }
, swarm_{ torrent_in->swarm }
, peer_{ peer_in }
{
}
MediatorImpl(MediatorImpl&&) = delete;
MediatorImpl(MediatorImpl const&) = delete;
MediatorImpl& operator=(MediatorImpl&&) = delete;
MediatorImpl& operator=(MediatorImpl const&) = delete;
~MediatorImpl() override = default;
[[nodiscard]] bool clientCanRequestBlock(tr_block_index_t block) const override
{
return !torrent_->has_block(block) && !swarm_->active_requests.has(block, peer_);
}
[[nodiscard]] bool clientCanRequestPiece(tr_piece_index_t piece) const override
{
return torrent_->piece_is_wanted(piece) && peer_->hasPiece(piece);
}
[[nodiscard]] bool isEndgame() const override
{
return swarm_->isEndgame();
}
[[nodiscard]] size_t countActiveRequests(tr_block_index_t block) const override
{
return swarm_->active_requests.count(block);
}
[[nodiscard]] size_t countMissingBlocks(tr_piece_index_t piece) const override
{
return torrent_->count_missing_blocks_in_piece(piece);
}
[[nodiscard]] tr_block_span_t blockSpan(tr_piece_index_t piece) const override
{
return torrent_->block_span_for_piece(piece);
}
[[nodiscard]] tr_piece_index_t countAllPieces() const override
{
return torrent_->piece_count();
}
[[nodiscard]] tr_priority_t priority(tr_piece_index_t piece) const override
{
return torrent_->piece_priority(piece);
}
[[nodiscard]] bool isSequentialDownload() const override
{
return torrent_->is_sequential_download();
}
private:
tr_torrent const* const torrent_;
tr_swarm const* const swarm_;
tr_peer const* const peer_;
};
torrent->swarm->updateEndgame();
auto const mediator = MediatorImpl{ torrent, peer };
return Wishlist{ mediator }.next(numwant);
}
// --- Piece List Manipulation / Accessors
bool tr_peerMgrDidPeerRequest(tr_torrent const* tor, tr_peer const* peer, tr_block_index_t block)
{
return tor->swarm->active_requests.has(block, peer);
}
size_t tr_peerMgrCountActiveRequestsToPeer(tr_torrent const* tor, tr_peer const* peer)
{
return tor->swarm->active_requests.count(peer);
}
void tr_peerMgr::refillUpkeep() const
{
auto const lock = unique_lock();
for (auto* const tor : session->torrents())
{
tor->swarm->cancelOldRequests();
}
}
namespace
{
namespace handshake_helpers
{
void create_bit_torrent_peer(tr_torrent* tor, std::shared_ptr<tr_peerIo> io, struct peer_atom* atom, tr_interned_string client)
{
TR_ASSERT(atom != nullptr);
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(tor->swarm != nullptr);
tr_swarm* swarm = tor->swarm;
auto* peer = tr_peerMsgsNew(tor, atom, std::move(io), client, &tr_swarm::peerCallbackFunc, swarm);
atom->is_connected = true;
swarm->peers.push_back(peer);
++swarm->stats.peer_count;
++swarm->stats.peer_from_count[atom->fromFirst];
TR_ASSERT(swarm->stats.peer_count == swarm->peerCount());
TR_ASSERT(swarm->stats.peer_from_count[atom->fromFirst] <= swarm->stats.peer_count);
}
/* FIXME: this is kind of a mess. */
[[nodiscard]] bool on_handshake_done(tr_peerMgr* manager, tr_handshake::Result const& result)
{
TR_ASSERT(result.io != nullptr);
bool const ok = result.is_connected;
bool success = false;
auto* const s = manager->get_existing_swarm(result.io->torrent_hash());
auto const& socket_address = result.io->socket_address();
if (result.io->is_incoming())
{
manager->incoming_handshakes.erase(socket_address);
}
else if (s != nullptr)
{
s->outgoing_handshakes.erase(socket_address);
}
auto const lock = manager->unique_lock();
if (!ok || s == nullptr || !s->is_running)
{
if (s != nullptr)
{
struct peer_atom* atom = s->get_existing_atom(socket_address);
if (atom != nullptr)
{
++atom->num_fails;
if (!result.read_anything_from_peer)
{
tr_logAddTraceSwarm(
s,
fmt::format(
"marking peer {} as unreachable... num_fails is {}",
atom->display_name(),
atom->num_fails));
atom->set_unreachable();
}
}
}
}
else /* looking good */
{
struct peer_atom* atom = s->ensure_atom_exists(socket_address, 0, TR_PEER_FROM_INCOMING);
atom->time = tr_time();
atom->piece_data_time = 0;
atom->lastConnectionAt = tr_time();
if (!result.io->is_incoming())
{
atom->flags |= ADDED_F_CONNECTABLE;
atom->set_reachable();
}
/* In principle, this flag specifies whether the peer groks µTP,
not whether it's currently connected over µTP. */
if (result.io->is_utp())
{
atom->flags |= ADDED_F_UTP_FLAGS;
}
if (atom->is_banned())
{
tr_logAddTraceSwarm(s, fmt::format("banned peer {} tried to reconnect", atom->display_name()));
}
else if (result.io->is_incoming() && s->peerCount() >= s->tor->peer_limit())
{
/* too many peers already */
}
else if (atom->is_connected)
{
// we're already connected to this peer; do nothing
}
else
{
auto client = tr_interned_string{};
if (result.peer_id)
{
auto buf = std::array<char, 128>{};
tr_clientForId(std::data(buf), sizeof(buf), *result.peer_id);
client = tr_interned_string{ tr_quark_new(std::data(buf)) };
}
result.io->set_bandwidth(&s->tor->bandwidth_);
create_bit_torrent_peer(s->tor, result.io, atom, client);
success = true;
}
}
return success;
}
} // namespace handshake_helpers
} // namespace
void tr_peerMgrAddIncoming(tr_peerMgr* manager, tr_peer_socket&& socket)
{
using namespace handshake_helpers;
TR_ASSERT(manager->session != nullptr);
auto const lock = manager->unique_lock();
tr_session* session = manager->session;
if (session->addressIsBlocked(socket.address()))
{
tr_logAddTrace(fmt::format("Banned IP address '{}' tried to connect to us", socket.display_name()));
socket.close();
}
else if (manager->incoming_handshakes.count(socket.socketAddress()) != 0U)
{
socket.close();
}
else /* we don't have a connection to them yet... */
{
auto sock_addr = tr_socket_address{ socket.socketAddress() };
manager->incoming_handshakes.try_emplace(
std::move(sock_addr),
&manager->handshake_mediator_,
tr_peerIo::new_incoming(session, &session->top_bandwidth_, std::move(socket)),
session->encryptionMode(),
[manager](tr_handshake::Result const& result) { return on_handshake_done(manager, result); });
}
}
size_t tr_peerMgrAddPex(tr_torrent* tor, uint8_t from, tr_pex const* pex, size_t n_pex)
{
size_t n_used = 0;
tr_swarm* s = tor->swarm;
auto const lock = s->manager->unique_lock();
for (tr_pex const* const end = pex + n_pex; pex != end; ++pex)
{
if (tr_isPex(pex) && /* safeguard against corrupt data */
!s->manager->session->addressIsBlocked(pex->addr) && pex->is_valid_for_peers())
{
s->ensure_atom_exists({ pex->addr, pex->port }, pex->flags, from);
++n_used;
}
}
return n_used;
}
std::vector<tr_pex> tr_pex::from_compact_ipv4(
void const* compact,
size_t compact_len,
uint8_t const* added_f,
size_t added_f_len)
{
size_t const n = compact_len / 6;
auto const* walk = static_cast<std::byte const*>(compact);
auto pex = std::vector<tr_pex>(n);
for (size_t i = 0; i < n; ++i)
{
std::tie(pex[i].addr, walk) = tr_address::from_compact_ipv4(walk);
std::tie(pex[i].port, walk) = tr_port::fromCompact(walk);
if (added_f != nullptr && n == added_f_len)
{
pex[i].flags = added_f[i];
}
}
return pex;
}
std::vector<tr_pex> tr_pex::from_compact_ipv6(
void const* compact,
size_t compact_len,
uint8_t const* added_f,
size_t added_f_len)
{
size_t const n = compact_len / 18;
auto const* walk = static_cast<std::byte const*>(compact);
auto pex = std::vector<tr_pex>(n);
for (size_t i = 0; i < n; ++i)
{
std::tie(pex[i].addr, walk) = tr_address::from_compact_ipv6(walk);
std::tie(pex[i].port, walk) = tr_port::fromCompact(walk);
if (added_f != nullptr && n == added_f_len)
{
pex[i].flags = added_f[i];
}
}
return pex;
}
// ---
namespace
{
namespace get_peers_helpers
{
/* better goes first */
constexpr struct
{
[[nodiscard]] constexpr static int compare(peer_atom const& a, peer_atom const& b) noexcept // <=>
{
if (auto const val = tr_compare_3way(a.piece_data_time, b.piece_data_time); val != 0)
{
return -val;
}
if (auto const val = tr_compare_3way(a.fromBest, b.fromBest); val != 0)
{
return val;
}
return tr_compare_3way(a.num_fails, b.num_fails);
}
[[nodiscard]] constexpr bool operator()(peer_atom const& a, peer_atom const& b) const noexcept
{
return compare(a, b) < 0;
}
[[nodiscard]] constexpr bool operator()(peer_atom const* a, peer_atom const* b) const noexcept
{
return compare(*a, *b) < 0;
}
} CompareAtomsByUsefulness{};
[[nodiscard]] bool isAtomInteresting(tr_torrent const* tor, peer_atom const& atom)
{
if (tor->is_done() && atom.isSeed())
{
return false;
}
if (tor->swarm->peer_is_in_use(atom))
{
return true;
}
if (atom.isBlocklisted(tor->session))
{
return false;
}
if (atom.is_banned())
{
return false;
}
return true;
}
} // namespace get_peers_helpers
} // namespace
std::vector<tr_pex> tr_peerMgrGetPeers(tr_torrent const* tor, uint8_t address_type, uint8_t list_mode, size_t max_peer_count)
{
using namespace get_peers_helpers;
TR_ASSERT(tr_isTorrent(tor));
auto const lock = tor->unique_lock();
TR_ASSERT(address_type == TR_AF_INET || address_type == TR_AF_INET6);
TR_ASSERT(list_mode == TR_PEERS_CONNECTED || list_mode == TR_PEERS_INTERESTING);
tr_swarm const* s = tor->swarm;
// build a list of atoms
auto atoms = std::vector<peer_atom const*>{};
if (list_mode == TR_PEERS_CONNECTED) /* connected peers only */
{
auto const& peers = s->peers;
atoms.reserve(std::size(peers));
std::transform(
std::begin(peers),
std::end(peers),
std::back_inserter(atoms),
[](auto const* peer) { return peer->atom; });
}
else /* TR_PEERS_INTERESTING */
{
for (auto const& [socket_address, atom] : s->pool)
{
if (isAtomInteresting(tor, atom))
{
atoms.push_back(&atom);
}
}
}
std::sort(std::begin(atoms), std::end(atoms), CompareAtomsByUsefulness);
// add the first N of them into our return list
auto const n = std::min(std::size(atoms), max_peer_count);
auto pex = std::vector<tr_pex>{};
pex.reserve(n);
for (size_t i = 0; i < std::size(atoms) && std::size(pex) < n; ++i)
{
auto const* const atom = atoms[i];
auto const& [addr, port] = atom->socket_address;
if (addr.type == address_type)
{
TR_ASSERT(addr.is_valid());
pex.emplace_back(addr, port, atom->flags);
}
}
std::sort(std::begin(pex), std::end(pex));
return pex;
}
void tr_swarm::on_torrent_started()
{
auto const lock = tor->unique_lock();
is_running = true;
manager->rechokeSoon();
}
void tr_swarm::on_torrent_stopped()
{
stop();
}
void tr_peerMgrAddTorrent(tr_peerMgr* manager, tr_torrent* tor)
{
TR_ASSERT(tr_isTorrent(tor));
auto const lock = tor->unique_lock();
TR_ASSERT(tor->swarm == nullptr);
tor->swarm = new tr_swarm{ manager, tor };
}
int8_t tr_peerMgrPieceAvailability(tr_torrent const* tor, tr_piece_index_t piece)
{
if (!tor->has_metainfo())
{
return 0;
}
if (tor->is_seed() || tor->has_piece(piece))
{
return -1;
}
auto const& peers = tor->swarm->peers;
return std::count_if(std::begin(peers), std::end(peers), [piece](auto const* peer) { return peer->hasPiece(piece); });
}
void tr_peerMgrTorrentAvailability(tr_torrent const* tor, int8_t* tab, unsigned int n_tabs)
{
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(tab != nullptr);
TR_ASSERT(n_tabs > 0);
std::fill_n(tab, n_tabs, int8_t{});
auto const interval = tor->piece_count() / static_cast<float>(n_tabs);
for (tr_piece_index_t i = 0; i < n_tabs; ++i)
{
auto const piece = static_cast<tr_piece_index_t>(i * interval);
tab[i] = tr_peerMgrPieceAvailability(tor, piece);
}
}
tr_swarm_stats tr_swarmGetStats(tr_swarm const* const swarm)
{
TR_ASSERT(swarm != nullptr);
auto count_active_peers = [&swarm](tr_direction dir)
{
return std::count_if(
std::begin(swarm->peers),
std::end(swarm->peers),
[dir](auto const& peer) { return peer->is_active(dir); });
};
auto& stats = swarm->stats;
stats.active_peer_count[TR_UP] = count_active_peers(TR_UP);
stats.active_peer_count[TR_DOWN] = count_active_peers(TR_DOWN);
stats.active_webseed_count = swarm->countActiveWebseeds(tr_time_msec());
return stats;
}
/* count how many bytes we want that connected peers have */
uint64_t tr_peerMgrGetDesiredAvailable(tr_torrent const* tor)
{
TR_ASSERT(tr_isTorrent(tor));
// common shortcuts...
if (!tor->is_running() || tor->is_stopping() || tor->is_done() || !tor->has_metainfo())
{
return 0;
}
tr_swarm const* const swarm = tor->swarm;
if (swarm == nullptr || std::empty(swarm->peers))
{
return 0;
}
auto available = swarm->peers.front()->has();
for (auto const* const peer : swarm->peers)
{
available |= peer->has();
}
if (available.has_all())
{
return tor->left_until_done();
}
auto desired_available = uint64_t{};
for (tr_piece_index_t i = 0, n = tor->piece_count(); i < n; ++i)
{
if (tor->piece_is_wanted(i) && available.test(i))
{
desired_available += tor->count_missing_bytes_in_piece(i);
}
}
TR_ASSERT(desired_available <= tor->total_size());
return desired_available;
}
tr_webseed_view tr_peerMgrWebseed(tr_torrent const* tor, size_t i)
{
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(tor->swarm != nullptr);
size_t const n = std::size(tor->swarm->webseeds);
TR_ASSERT(i < n);
return i >= n ? tr_webseed_view{} : tr_webseedView(tor->swarm->webseeds[i].get());
}
namespace
{
namespace peer_stat_helpers
{
[[nodiscard]] auto get_peer_stats(tr_peerMsgs const* peer, time_t now, uint64_t now_msec)
{
auto stats = tr_peer_stat{};
auto const* const atom = peer->atom;
auto const [addr, port] = peer->socketAddress();
addr.display_name(stats.addr, sizeof(stats.addr));
stats.client = peer->user_agent().c_str();
stats.port = port.host();
stats.from = atom->fromFirst;
stats.progress = peer->percentDone();
stats.isUTP = peer->is_utp_connection();
stats.isEncrypted = peer->is_encrypted();
stats.rateToPeer_KBps = tr_toSpeedKBps(peer->get_piece_speed_bytes_per_second(now_msec, TR_CLIENT_TO_PEER));
stats.rateToClient_KBps = tr_toSpeedKBps(peer->get_piece_speed_bytes_per_second(now_msec, TR_PEER_TO_CLIENT));
stats.peerIsChoked = peer->peer_is_choked();
stats.peerIsInterested = peer->peer_is_interested();
stats.clientIsChoked = peer->client_is_choked();
stats.clientIsInterested = peer->client_is_interested();
stats.isIncoming = peer->is_incoming_connection();
stats.isDownloadingFrom = peer->is_active(TR_PEER_TO_CLIENT);
stats.isUploadingTo = peer->is_active(TR_CLIENT_TO_PEER);
stats.isSeed = peer->isSeed();
stats.blocksToPeer = peer->blocks_sent_to_peer.count(now, CancelHistorySec);
stats.blocksToClient = peer->blocks_sent_to_client.count(now, CancelHistorySec);
stats.cancelsToPeer = peer->cancels_sent_to_peer.count(now, CancelHistorySec);
stats.cancelsToClient = peer->cancels_sent_to_client.count(now, CancelHistorySec);
stats.activeReqsToPeer = peer->activeReqCount(TR_CLIENT_TO_PEER);
stats.activeReqsToClient = peer->activeReqCount(TR_PEER_TO_CLIENT);
char* pch = stats.flagStr;
if (stats.isUTP)
{
*pch++ = 'T';
}
if (peer->swarm->optimistic == peer)
{
*pch++ = 'O';
}
if (stats.isDownloadingFrom)
{
*pch++ = 'D';
}
else if (stats.clientIsInterested)
{
*pch++ = 'd';
}
if (stats.isUploadingTo)
{
*pch++ = 'U';
}
else if (stats.peerIsInterested)
{
*pch++ = 'u';
}
if (!stats.clientIsChoked && !stats.clientIsInterested)
{
*pch++ = 'K';
}
if (!stats.peerIsChoked && !stats.peerIsInterested)
{
*pch++ = '?';
}
if (stats.isEncrypted)
{
*pch++ = 'E';
}
if (stats.from == TR_PEER_FROM_DHT)
{
*pch++ = 'H';
}
else if (stats.from == TR_PEER_FROM_PEX)
{
*pch++ = 'X';
}
if (stats.isIncoming)
{
*pch++ = 'I';
}
*pch = '\0';
return stats;
}
} // namespace peer_stat_helpers
} // namespace
tr_peer_stat* tr_peerMgrPeerStats(tr_torrent const* tor, size_t* setme_count)
{
using namespace peer_stat_helpers;
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(tor->swarm->manager != nullptr);
auto const peers = tor->swarm->peers;
auto const n = std::size(peers);
auto* const ret = new tr_peer_stat[n];
auto const now = tr_time();
auto const now_msec = tr_time_msec();
std::transform(
std::begin(peers),
std::end(peers),
ret,
[&now, &now_msec](auto const* peer) { return get_peer_stats(peer, now, now_msec); });
*setme_count = n;
return ret;
}
namespace
{
namespace update_interest_helpers
{
/* does this peer have any pieces that we want? */
[[nodiscard]] bool isPeerInteresting(
tr_torrent const* const tor,
std::vector<bool> const& piece_is_interesting,
tr_peerMsgs const* const peer)
{
/* these cases should have already been handled by the calling code... */
TR_ASSERT(!tor->is_done());
TR_ASSERT(tor->client_can_download());
if (peer->isSeed())
{
return true;
}
for (tr_piece_index_t i = 0; i < tor->piece_count(); ++i)
{
if (piece_is_interesting[i] && peer->hasPiece(i))
{
return true;
}
}
return false;
}
// determine which peers to show interest in
void updateInterest(tr_swarm* swarm)
{
// sometimes this function isn't necessary
auto const* const tor = swarm->tor;
if (tor->is_done() || !tor->client_can_download())
{
return;
}
if (auto const& peers = swarm->peers; !std::empty(peers))
{
int const n = tor->piece_count();
// build a bitfield of interesting pieces...
auto piece_is_interesting = std::vector<bool>{};
piece_is_interesting.resize(n);
for (int i = 0; i < n; ++i)
{
piece_is_interesting[i] = tor->piece_is_wanted(i) && !tor->has_piece(i);
}
for (auto* const peer : peers)
{
peer->set_interested(isPeerInteresting(tor, piece_is_interesting, peer));
}
}
}
} // namespace update_interest_helpers
} // namespace
// ---
namespace
{
namespace rechoke_uploads_helpers
{
struct ChokeData
{
ChokeData(tr_peerMsgs* msgs_in, int rate_in, uint8_t salt_in, bool is_interested_in, bool was_choked_in, bool is_choked_in)
: msgs{ msgs_in }
, rate{ rate_in }
, salt{ salt_in }
, is_interested{ is_interested_in }
, was_choked{ was_choked_in }
, is_choked{ is_choked_in }
{
}
tr_peerMsgs* msgs;
int rate;
uint8_t salt;
bool is_interested;
bool was_choked;
bool is_choked;
[[nodiscard]] constexpr auto compare(ChokeData const& that) const noexcept // <=>
{
// prefer higher overall speeds
if (auto const val = tr_compare_3way(this->rate, that.rate); val != 0)
{
return -val;
}
if (this->was_choked != that.was_choked) // prefer unchoked
{
return this->was_choked ? 1 : -1;
}
return tr_compare_3way(this->salt, that.salt);
}
[[nodiscard]] constexpr auto operator<(ChokeData const& that) const noexcept
{
return compare(that) < 0;
}
};
/* get a rate for deciding which peers to choke and unchoke. */
[[nodiscard]] auto getRateBps(tr_torrent const* tor, tr_peer const* peer, uint64_t now)
{
if (tor->is_done())
{
return peer->get_piece_speed_bytes_per_second(now, TR_CLIENT_TO_PEER);
}
/* downloading a private torrent... take upload speed into account
* because there may only be a small window of opportunity to share */
if (tor->is_private())
{
return peer->get_piece_speed_bytes_per_second(now, TR_PEER_TO_CLIENT) +
peer->get_piece_speed_bytes_per_second(now, TR_CLIENT_TO_PEER);
}
/* downloading a public torrent */
return peer->get_piece_speed_bytes_per_second(now, TR_PEER_TO_CLIENT);
}
// an optimistically unchoked peer is immune from rechoking
// for this many calls to rechokeUploads().
auto constexpr OptimisticUnchokeMultiplier = uint8_t{ 4 };
void rechokeUploads(tr_swarm* s, uint64_t const now)
{
auto const lock = s->unique_lock();
auto& peers = s->peers;
auto const peer_count = std::size(peers);
auto choked = std::vector<ChokeData>{};
choked.reserve(peer_count);
auto const* const session = s->manager->session;
bool const choke_all = !s->tor->client_can_upload();
bool const is_maxed_out = s->tor->bandwidth_.is_maxed_out(TR_UP, now);
/* an optimistic unchoke peer's "optimistic"
* state lasts for N calls to rechokeUploads(). */
if (s->optimistic_unchoke_time_scaler > 0)
{
--s->optimistic_unchoke_time_scaler;
}
else
{
s->optimistic = nullptr;
}
/* sort the peers by preference and rate */
auto salter = tr_salt_shaker{};
for (auto* const peer : peers)
{
if (peer->isSeed())
{
/* choke seeds and partial seeds */
peer->set_choke(true);
}
else if (choke_all)
{
/* choke everyone if we're not uploading */
peer->set_choke(true);
}
else if (peer != s->optimistic)
{
choked.emplace_back(
peer,
getRateBps(s->tor, peer, now),
salter(),
peer->peer_is_interested(),
peer->peer_is_choked(),
true);
}
}
std::sort(std::begin(choked), std::end(choked));
/**
* Reciprocation and number of uploads capping is managed by unchoking
* the N peers which have the best upload rate and are interested.
* This maximizes the client's download rate. These N peers are
* referred to as downloaders, because they are interested in downloading
* from the client.
*
* Peers which have a better upload rate (as compared to the downloaders)
* but aren't interested get unchoked. If they become interested, the
* downloader with the worst upload rate gets choked. If a client has
* a complete file, it uses its upload rate rather than its download
* rate to decide which peers to unchoke.
*
* If our bandwidth is maxed out, don't unchoke any more peers.
*/
auto checked_choke_count = size_t{ 0U };
auto unchoked_interested = size_t{ 0U };
for (auto& item : choked)
{
if (unchoked_interested >= session->uploadSlotsPerTorrent())
{
break;
}
item.is_choked = is_maxed_out ? item.was_choked : false;
++checked_choke_count;
if (item.is_interested)
{
++unchoked_interested;
}
}
/* optimistic unchoke */
if (s->optimistic == nullptr && !is_maxed_out && checked_choke_count < std::size(choked))
{
auto rand_pool = std::vector<ChokeData*>{};
for (auto i = checked_choke_count, n = std::size(choked); i < n; ++i)
{
if (choked[i].is_interested)
{
rand_pool.push_back(&choked[i]);
}
}
if (auto const n = std::size(rand_pool); n != 0)
{
auto* c = rand_pool[tr_rand_int(n)];
c->is_choked = false;
s->optimistic = c->msgs;
s->optimistic_unchoke_time_scaler = OptimisticUnchokeMultiplier;
}
}
for (auto& item : choked)
{
item.msgs->set_choke(item.is_choked);
}
}
} // namespace rechoke_uploads_helpers
} // namespace
void tr_peerMgr::rechokePulse() const
{
using namespace update_interest_helpers;
using namespace rechoke_uploads_helpers;
auto const lock = unique_lock();
auto const now = tr_time_msec();
for (auto* const tor : session->torrents())
{
if (tor->is_running())
{
// possibly stop torrents that have seeded enough
tr_torrentCheckSeedLimit(tor);
}
if (tor->is_running())
{
if (auto* const swarm = tor->swarm; swarm->stats.peer_count > 0)
{
rechokeUploads(swarm, now);
updateInterest(swarm);
}
}
}
}
// --- Life and Death
namespace
{
namespace disconnect_helpers
{
// when many peers are available, keep idle ones this long
auto constexpr MinUploadIdleSecs = time_t{ 60 };
// when few peers are available, keep idle ones this long
auto constexpr MaxUploadIdleSecs = time_t{ 60 * 5 };
[[nodiscard]] bool shouldPeerBeClosed(tr_swarm const* s, tr_peerMsgs const* peer, size_t peer_count, time_t const now)
{
/* if it's marked for purging, close it */
if (peer->do_purge)
{
tr_logAddTraceSwarm(s, fmt::format("purging peer {} because its do_purge flag is set", peer->display_name()));
return true;
}
auto const* tor = s->tor;
auto const* const atom = peer->atom;
/* disconnect if we're both seeds and enough time has passed for PEX */
if (tor->is_done() && peer->isSeed())
{
return !tor->allows_pex() || now - atom->time >= 30;
}
/* disconnect if it's been too long since piece data has been transferred.
* this is on a sliding scale based on number of available peers... */
{
auto const relax_strictness_if_fewer_than_n = static_cast<size_t>(std::lround(tor->peer_limit() * 0.9));
/* if we have >= relaxIfFewerThan, strictness is 100%.
* if we have zero connections, strictness is 0% */
float const strictness = peer_count >= relax_strictness_if_fewer_than_n ?
1.0 :
peer_count / (float)relax_strictness_if_fewer_than_n;
auto const lo = MinUploadIdleSecs;
auto const hi = MaxUploadIdleSecs;
time_t const limit = hi - (hi - lo) * strictness;
time_t const idle_time = now - std::max(atom->time, atom->piece_data_time);
if (idle_time > limit)
{
tr_logAddTraceSwarm(
s,
fmt::format(
"purging peer {} because it's been {} secs since we shared anything",
peer->display_name(),
idle_time));
return true;
}
}
return false;
}
void closePeer(tr_peer* peer)
{
TR_ASSERT(peer != nullptr);
auto const* const s = peer->swarm;
/* if we transferred piece data, then they might be good peers,
so reset their `num_fails' weight to zero. otherwise we connected
to them fruitlessly, so mark it as another fail */
if (auto* const atom = peer->atom; atom->piece_data_time != 0)
{
tr_logAddTraceSwarm(s, fmt::format("resetting atom {} num_fails to 0", peer->display_name()));
atom->num_fails = 0;
}
else
{
++atom->num_fails;
tr_logAddTraceSwarm(s, fmt::format("incremented atom {} num_fails to {}", peer->display_name(), atom->num_fails));
}
tr_logAddTraceSwarm(s, fmt::format("removing bad peer {}", peer->display_name()));
peer->swarm->removePeer(peer);
}
constexpr struct
{
[[nodiscard]] constexpr static int compare(tr_peer const* a, tr_peer const* b) // <=>
{
if (a->do_purge != b->do_purge)
{
return a->do_purge ? 1 : -1;
}
/* the one to give us data more recently goes first */
if (auto const val = tr_compare_3way(a->atom->piece_data_time, b->atom->piece_data_time); val != 0)
{
return -val;
}
/* the one we connected to most recently goes first */
return -tr_compare_3way(a->atom->time, b->atom->time);
}
[[nodiscard]] constexpr bool operator()(tr_peer const* a, tr_peer const* b) const // less than
{
return compare(a, b) < 0;
}
} ComparePeerByMostActive{};
constexpr auto ComparePeerByLeastActive = [](tr_peer const* a, tr_peer const* b)
{
return ComparePeerByMostActive(b, a);
};
[[nodiscard]] auto getPeersToClose(tr_swarm const* const swarm, time_t const now_sec)
{
auto const& peers = swarm->peers;
auto const peer_count = std::size(peers);
auto peers_to_close = std::vector<tr_peer*>{};
peers_to_close.reserve(peer_count);
for (auto* peer : swarm->peers)
{
if (shouldPeerBeClosed(swarm, peer, peer_count, now_sec))
{
peers_to_close.push_back(peer);
}
}
return peers_to_close;
}
void closeBadPeers(tr_swarm* s, time_t const now_sec)
{
for (auto* peer : getPeersToClose(s, now_sec))
{
closePeer(peer);
}
}
void enforceSwarmPeerLimit(tr_swarm* swarm, size_t max)
{
// do we have too many peers?
auto const n = swarm->peerCount();
if (n <= max)
{
return;
}
// close all but the `max` most active
auto peers = std::vector<tr_peerMsgs*>{ n - max };
std::partial_sort_copy(
std::begin(swarm->peers),
std::end(swarm->peers),
std::begin(peers),
std::end(peers),
ComparePeerByLeastActive);
std::for_each(std::begin(peers), std::end(peers), closePeer);
}
void enforceSessionPeerLimit(tr_session* session)
{
// No need to disconnect if we are under the peer limit
auto const max = session->peerLimit();
if (tr_peerMsgs::size() <= max)
{
return;
}
// Make a list of all the peers.
auto peers = std::vector<tr_peer*>{};
peers.reserve(tr_peerMsgs::size());
for (auto const* const tor : session->torrents())
{
peers.insert(std::end(peers), std::begin(tor->swarm->peers), std::end(tor->swarm->peers));
}
TR_ASSERT(tr_peerMsgs::size() == std::size(peers));
if (std::size(peers) > max)
{
std::partial_sort(std::begin(peers), std::begin(peers) + max, std::end(peers), ComparePeerByMostActive);
std::for_each(std::begin(peers) + max, std::end(peers), closePeer);
}
}
} // namespace disconnect_helpers
} // namespace
void tr_peerMgr::reconnectPulse()
{
using namespace disconnect_helpers;
auto const lock = session->unique_lock();
auto const now_sec = tr_time();
// remove crappy peers
for (auto* const tor : session->torrents())
{
auto* const swarm = tor->swarm;
if (!swarm->is_running)
{
swarm->removeAllPeers();
}
else
{
closeBadPeers(swarm, now_sec);
}
}
// if we're over the per-torrent peer limits, cull some peers
for (auto* const tor : session->torrents())
{
if (tor->is_running())
{
enforceSwarmPeerLimit(tor->swarm, tor->peer_limit());
}
}
// if we're over the per-session peer limits, cull some peers
enforceSessionPeerLimit(session);
// try to make new peer connections
make_new_peer_connections();
}
// --- Bandwidth Allocation
namespace
{
namespace bandwidth_helpers
{
void pumpAllPeers(tr_peerMgr* mgr)
{
for (auto* const tor : mgr->session->torrents())
{
for (auto* const peer : tor->swarm->peers)
{
peer->pulse();
}
}
}
void queuePulse(tr_session* session, tr_direction dir)
{
TR_ASSERT(session != nullptr);
TR_ASSERT(tr_isDirection(dir));
if (!session->queueEnabled(dir))
{
return;
}
auto const n = session->countQueueFreeSlots(dir);
for (auto* tor : session->getNextQueuedTorrents(dir, n))
{
tr_torrentStartNow(tor);
session->onQueuedTorrentStarted(tor);
}
}
} // namespace bandwidth_helpers
} // namespace
void tr_peerMgr::bandwidthPulse()
{
using namespace bandwidth_helpers;
auto const lock = unique_lock();
pumpAllPeers(this);
// allocate bandwidth to the peers
static auto constexpr Msec = std::chrono::duration_cast<std::chrono::milliseconds>(BandwidthTimerPeriod).count();
session->top_bandwidth_.allocate(Msec);
// torrent upkeep
for (auto* const tor : session->torrents())
{
tor->do_idle_work();
tr_torrentMagnetDoIdleWork(tor);
}
/* pump the queues */
queuePulse(session, TR_UP);
queuePulse(session, TR_DOWN);
reconnectPulse();
}
// ---
bool tr_swarm::peer_is_in_use(peer_atom const& atom) const
{
return atom.is_connected || outgoing_handshakes.count(atom.socket_address) != 0U ||
manager->incoming_handshakes.count(atom.socket_address) != 0U;
}
namespace
{
namespace connect_helpers
{
/* is this atom someone that we'd want to initiate a connection to? */
[[nodiscard]] bool isPeerCandidate(tr_torrent const* tor, peer_atom const& atom, time_t const now)
{
// have we already tried and failed to connect?
if (atom.is_unreachable())
{
return false;
}
// not if we're both seeds
if (tor->is_done() && atom.isSeed())
{
return false;
}
// not if we've already got a connection to them...
if (tor->swarm->peer_is_in_use(atom))
{
return false;
}
// not if we just tried them already
if (now - atom.time < atom.getReconnectIntervalSecs(now))
{
return false;
}
// not if they're blocklisted
if (atom.isBlocklisted(tor->session))
{
return false;
}
// not if they're banned...
if (atom.is_banned())
{
return false;
}
return true;
}
struct peer_candidate
{
peer_candidate() = default;
peer_candidate(uint64_t score_in, tr_torrent* tor_in, peer_atom* atom_in)
: score{ score_in }
, tor{ tor_in }
, atom{ atom_in }
{
}
uint64_t score;
tr_torrent* tor;
peer_atom* atom;
};
[[nodiscard]] bool torrentWasRecentlyStarted(tr_torrent const* tor)
{
return difftime(tr_time(), tor->startDate) < 120;
}
[[nodiscard]] constexpr uint64_t addValToKey(uint64_t value, int width, uint64_t addme)
{
value = value << (uint64_t)width;
value |= addme;
return value;
}
/* smaller value is better */
[[nodiscard]] uint64_t getPeerCandidateScore(tr_torrent const* tor, peer_atom const& atom, uint8_t salt)
{
auto i = uint64_t{};
auto score = uint64_t{};
bool const failed = atom.lastConnectionAt < atom.lastConnectionAttemptAt;
/* prefer peers we've connected to, or never tried, over peers we failed to connect to. */
i = failed ? 1 : 0;
score = addValToKey(score, 1, i);
/* prefer the one we attempted least recently (to cycle through all peers) */
i = atom.lastConnectionAttemptAt;
score = addValToKey(score, 32, i);
/* prefer peers belonging to a torrent of a higher priority */
switch (tor->get_priority())
{
case TR_PRI_HIGH:
i = 0;
break;
case TR_PRI_NORMAL:
i = 1;
break;
case TR_PRI_LOW:
i = 2;
break;
}
score = addValToKey(score, 4, i);
/* prefer recently-started torrents */
i = torrentWasRecentlyStarted(tor) ? 0 : 1;
score = addValToKey(score, 1, i);
/* prefer torrents we're downloading with */
i = tor->is_done() ? 1 : 0;
score = addValToKey(score, 1, i);
/* prefer peers that are known to be connectible */
i = (atom.flags & ADDED_F_CONNECTABLE) != 0 ? 0 : 1;
score = addValToKey(score, 1, i);
/* prefer peers that we might be able to upload to */
i = (atom.flags & ADDED_F_SEED_FLAG) == 0 ? 0 : 1;
score = addValToKey(score, 1, i);
/* Prefer peers that we got from more trusted sources.
* lower `fromBest` values indicate more trusted sources */
score = addValToKey(score, 4, atom.fromBest);
/* salt */
score = addValToKey(score, 8, salt);
return score;
}
[[nodiscard]] tr_peerMgr::OutboundCandidates get_peer_candidates(tr_session* session)
{
auto const now = tr_time();
auto const now_msec = tr_time_msec();
// leave 5% of connection slots for incoming connections -- ticket #2609
if (auto const max_candidates = static_cast<size_t>(session->peerLimit() * 0.95); max_candidates <= tr_peerMsgs::size())
{
return {};
}
auto candidates = std::vector<peer_candidate>{};
candidates.reserve(peer_atom::atom_count());
/* populate the candidate array */
auto salter = tr_salt_shaker{};
for (auto* const tor : session->torrents())
{
auto* const swarm = tor->swarm;
if (!swarm->is_running)
{
continue;
}
/* if everyone in the swarm is seeds and pex is disabled because
* the torrent is private, then don't initiate connections */
bool const seeding = tor->is_done();
if (seeding && swarm->isAllSeeds() && tor->is_private())
{
continue;
}
/* if we've already got enough peers in this torrent... */
if (tor->peer_limit() <= swarm->peerCount())
{
continue;
}
/* if we've already got enough speed in this torrent... */
if (seeding && tor->bandwidth_.is_maxed_out(TR_UP, now_msec))
{
continue;
}
for (auto& [socket_address, atom] : swarm->pool)
{
if (isPeerCandidate(tor, atom, now))
{
candidates.emplace_back(getPeerCandidateScore(tor, atom, salter()), tor, &atom);
}
}
}
// only keep the best `max` candidates
if (auto const max = tr_peerMgr::OutboundCandidates::requested_inline_size; max < std::size(candidates))
{
std::partial_sort(
std::begin(candidates),
std::begin(candidates) + max,
std::end(candidates),
[](auto const& a, auto const& b) { return a.score < b.score; });
candidates.resize(max);
}
auto ret = tr_peerMgr::OutboundCandidates{};
for (auto const& candidate : candidates)
{
ret.emplace_back(candidate.tor->id(), candidate.atom->socket_address);
}
return ret;
}
void initiateConnection(tr_peerMgr* mgr, tr_swarm* s, peer_atom& atom)
{
using namespace handshake_helpers;
auto const now = tr_time();
bool utp = mgr->session->allowsUTP() && !atom.utp_failed;
if (atom.fromFirst == TR_PEER_FROM_PEX)
{
/* PEX has explicit signalling for µTP support. If an atom
originally came from PEX and doesn't have the µTP flag, skip the
µTP connection attempt. Are we being optimistic here? */
utp = utp && (atom.flags & ADDED_F_UTP_FLAGS) != 0;
}
auto* const session = mgr->session;
if (tr_peer_socket::limit_reached(session) || (!utp && !session->allowsTCP()))
{
return;
}
tr_logAddTraceSwarm(
s,
fmt::format("Starting an OUTGOING {} connection with {}", utp ? " µTP" : "TCP", atom.display_name()));
auto peer_io = tr_peerIo::new_outgoing(
session,
&session->top_bandwidth_,
atom.socket_address,
s->tor->info_hash(),
s->tor->completeness == TR_SEED,
utp);
if (!peer_io)
{
tr_logAddTraceSwarm(s, fmt::format("peerIo not created; marking peer {} as unreachable", atom.display_name()));
atom.set_unreachable();
++atom.num_fails;
}
else
{
s->outgoing_handshakes.try_emplace(
atom.socket_address,
&mgr->handshake_mediator_,
peer_io,
session->encryptionMode(),
[mgr](tr_handshake::Result const& result) { return on_handshake_done(mgr, result); });
}
atom.lastConnectionAttemptAt = now;
atom.time = now;
}
} // namespace connect_helpers
} // namespace
void tr_peerMgr::make_new_peer_connections()
{
using namespace connect_helpers;
auto const lock = session->unique_lock();
// get the candidates if we need to
auto& peers = outbound_candidates_;
if (std::empty(peers))
{
peers = get_peer_candidates(session);
}
// initiate connections to the first N candidates
auto const n_this_pass = std::min(std::size(peers), MaxConnectionsPerPulse);
for (size_t i = 0; i < n_this_pass; ++i)
{
auto const& [tor_id, sock_addr] = peers[i];
auto* const tor = session->torrents().get(tor_id);
auto* const atom = tor->swarm->get_existing_atom(sock_addr);
if (tor != nullptr && atom != nullptr)
{
initiateConnection(this, tor->swarm, *atom);
}
}
// remove the first N candidates from the list
peers.erase(std::begin(peers), std::begin(peers) + n_this_pass);
}
// ---
bool HandshakeMediator::is_peer_known_seed(tr_torrent_id_t tor_id, tr_socket_address const& socket_address) const
{
auto const* const tor = session_.torrents().get(tor_id);
return tor != nullptr && tor->swarm != nullptr && tor->swarm->peer_is_a_seed(socket_address);
}
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