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transmission/libtransmission/webseed.cc

523 lines
13 KiB
C++

// This file Copyright © 2008-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <iterator>
#include <set>
#include <string>
#include <string_view>
#include <event2/buffer.h>
#include <event2/event.h>
#include <fmt/format.h>
#include "transmission.h"
#include "bandwidth.h"
#include "cache.h"
#include "peer-mgr.h"
#include "torrent.h"
#include "trevent.h" /* tr_runInEventThread() */
#include "utils.h"
#include "web-utils.h"
#include "web.h"
#include "webseed.h"
using namespace std::literals;
namespace
{
class tr_webseed;
void on_idle(tr_webseed* w);
class tr_webseed_task
{
private:
std::shared_ptr<evbuffer> const content_{ evbuffer_new(), evbuffer_free };
public:
tr_webseed_task(tr_torrent* tor, tr_webseed* webseed_in, tr_block_span_t blocks_in)
: webseed{ webseed_in }
, session{ tor->session }
, blocks{ blocks_in }
, end_byte{ tor->blockLoc(blocks.end - 1).byte + tor->blockSize(blocks.end - 1) }
, loc{ tor->blockLoc(blocks.begin) }
{
}
tr_webseed* const webseed;
[[nodiscard]] auto* content() const
{
return content_.get();
}
tr_session* const session;
tr_block_span_t const blocks;
uint64_t const end_byte;
// the current position in the task; i.e., the next block to save
tr_block_info::Location loc;
bool dead = false;
};
/**
* Manages how many web tasks should be running at a time.
*
* - When all is well, allow multiple tasks running in parallel.
* - If we get an error, throttle down to only one at a time
* until we get piece data.
* - If we have too many errors in a row, put the peer in timeout
* and don't allow _any_ connections for awhile.
*/
class ConnectionLimiter
{
public:
constexpr void taskStarted() noexcept
{
++n_tasks;
}
void taskFinished(bool success)
{
if (!success)
{
taskFailed();
}
TR_ASSERT(n_tasks > 0);
--n_tasks;
}
constexpr void gotData() noexcept
{
TR_ASSERT(n_tasks > 0);
n_consecutive_failures = 0;
paused_until = 0;
}
[[nodiscard]] size_t slotsAvailable() const noexcept
{
if (isPaused())
{
return 0;
}
auto const max = maxConnections();
if (n_tasks >= max)
{
return 0;
}
return max - n_tasks;
}
private:
[[nodiscard]] bool isPaused() const noexcept
{
return paused_until > tr_time();
}
[[nodiscard]] constexpr size_t maxConnections() const noexcept
{
return n_consecutive_failures > 0 ? 1 : MaxConnections;
}
void taskFailed()
{
TR_ASSERT(n_tasks > 0);
if (++n_consecutive_failures >= MaxConsecutiveFailures)
{
paused_until = tr_time() + TimeoutIntervalSecs;
}
}
static time_t constexpr TimeoutIntervalSecs = 120;
static size_t constexpr MaxConnections = 4;
static size_t constexpr MaxConsecutiveFailures = MaxConnections;
size_t n_tasks = 0;
size_t n_consecutive_failures = 0;
time_t paused_until = 0;
};
class tr_webseed : public tr_peer
{
public:
tr_webseed(struct tr_torrent* tor, std::string_view url, tr_peer_callback callback_in, void* callback_data_in)
: tr_peer{ tor }
, torrent_id{ tr_torrentId(tor) }
, base_url{ url }
, callback{ callback_in }
, callback_data{ callback_data_in }
, bandwidth(&tor->bandwidth_)
, pulse_timer(evtimer_new(session->event_base, &tr_webseed::onTimer, this), event_free)
{
// init parent bits
have.setHasAll();
tr_peerUpdateProgress(tor, this);
startTimer();
}
~tr_webseed() override
{
// flag all the pending tasks as dead
std::for_each(std::begin(tasks), std::end(tasks), [](auto* task) { task->dead = true; });
tasks.clear();
}
[[nodiscard]] tr_torrent* getTorrent() const
{
return tr_torrentFindFromId(session, torrent_id);
}
[[nodiscard]] bool is_transferring_pieces(uint64_t now, tr_direction direction, unsigned int* setme_Bps) const override
{
unsigned int Bps = 0;
bool is_active = false;
if (direction == TR_DOWN)
{
is_active = !std::empty(tasks);
Bps = bandwidth.getPieceSpeedBytesPerSecond(now, direction);
}
if (setme_Bps != nullptr)
{
*setme_Bps = Bps;
}
return is_active;
}
void gotPieceData(uint32_t n_bytes)
{
bandwidth.notifyBandwidthConsumed(TR_DOWN, n_bytes, true, tr_time_msec());
publishClientGotPieceData(n_bytes);
connection_limiter.gotData();
}
void publishRejection(tr_block_span_t block_span)
{
auto e = tr_peer_event{};
e.eventType = TR_PEER_CLIENT_GOT_REJ;
for (auto block = block_span.begin; block < block_span.end; ++block)
{
auto const loc = getTorrent()->blockLoc(block);
e.pieceIndex = loc.piece;
e.offset = loc.piece_offset;
publish(&e);
}
}
void publishGotBlock(tr_torrent const* tor, tr_block_info::Location loc)
{
TR_ASSERT(loc.block_offset == 0);
TR_ASSERT(loc.block < tor->blockCount());
auto e = tr_peer_event{};
e.eventType = TR_PEER_CLIENT_GOT_BLOCK;
e.pieceIndex = loc.piece;
e.offset = loc.piece_offset;
e.length = tor->blockSize(loc.block);
publish(&e);
}
int const torrent_id;
std::string const base_url;
tr_peer_callback const callback;
void* const callback_data;
Bandwidth bandwidth;
ConnectionLimiter connection_limiter;
std::set<tr_webseed_task*> tasks;
private:
void publish(tr_peer_event* event)
{
if (callback != nullptr)
{
(*callback)(this, event, callback_data);
}
}
void publishClientGotPieceData(uint32_t length)
{
auto e = tr_peer_event{};
e.eventType = TR_PEER_CLIENT_GOT_PIECE_DATA;
e.length = length;
publish(&e);
}
void startTimer()
{
tr_timerAddMsec(pulse_timer.get(), IdleTimerMsec);
}
static void onTimer(evutil_socket_t /*fd*/, short /*what*/, void* vwebseed)
{
auto* const webseed = static_cast<tr_webseed*>(vwebseed);
on_idle(webseed);
webseed->startTimer();
}
std::shared_ptr<event> const pulse_timer;
static int constexpr IdleTimerMsec = 2000;
};
/***
****
***/
struct write_block_data
{
private:
std::shared_ptr<evbuffer> const content_{ evbuffer_new(), evbuffer_free };
public:
write_block_data(tr_session* session_in, int torrent_id_in, tr_webseed* webseed_in, tr_block_info::Location loc_in)
: session{ session_in }
, torrent_id{ torrent_id_in }
, webseed{ webseed_in }
, loc{ loc_in }
{
TR_ASSERT(loc.block_offset == 0);
}
[[nodiscard]] auto* content() const
{
return content_.get();
}
void write_block_func()
{
auto* const buf = this->content();
if (auto* const tor = tr_torrentFindFromId(this->session, this->torrent_id); tor != nullptr)
{
auto const len = evbuffer_get_length(buf);
TR_ASSERT(tor->blockSize(this->loc.block) == len);
tr_cacheWriteBlock(tor->session->cache, tor, this->loc, len, buf);
webseed->publishGotBlock(tor, this->loc);
TR_ASSERT(evbuffer_get_length(buf) == 0);
}
delete this;
}
private:
tr_session* const session;
int const torrent_id;
tr_webseed* const webseed;
tr_block_info::Location const loc;
};
void useFetchedBlocks(tr_webseed_task* task)
{
auto* const session = task->session;
auto const lock = session->unique_lock();
auto* const webseed = task->webseed;
auto const* const tor = webseed->getTorrent();
if (tor == nullptr)
{
return;
}
auto* const buf = task->content();
for (;;)
{
auto const block_size = tor->blockSize(task->loc.block);
if (evbuffer_get_length(buf) < block_size)
{
break;
}
if (tor->hasBlock(task->loc.block))
{
evbuffer_drain(buf, block_size);
}
else
{
auto* const data = new write_block_data{ session, tor->uniqueId, webseed, task->loc };
evbuffer_remove_buffer(task->content(), data->content(), block_size);
tr_runInEventThread(session, &write_block_data::write_block_func, data);
}
task->loc = tor->byteLoc(task->loc.byte + block_size);
TR_ASSERT(task->loc.byte == task->end_byte || task->loc.block_offset == 0);
}
}
/***
****
***/
void onBufferGotData(evbuffer* /*buf*/, evbuffer_cb_info const* info, void* vtask)
{
size_t const n_added = info->n_added;
auto* const task = static_cast<tr_webseed_task*>(vtask);
if (n_added == 0 || task->dead)
{
return;
}
auto const* const session = task->session;
auto const lock = session->unique_lock();
auto* const webseed = task->webseed;
webseed->gotPieceData(n_added);
useFetchedBlocks(task);
}
void task_request_next_chunk(tr_webseed_task* task);
void on_idle(tr_webseed* w)
{
auto* const tor = w->getTorrent();
if (tor == nullptr || !tor->isRunning || tor->isDone())
{
return;
}
auto const slots_available = w->connection_limiter.slotsAvailable();
if (slots_available == 0)
{
return;
}
// Prefer to request large, contiguous chunks from webseeds.
// The actual value of '64' is arbitrary here; we could probably
// be smarter about this.
auto constexpr PreferredBlocksPerTask = size_t{ 64 };
auto const spans = tr_peerMgrGetNextRequests(tor, w, slots_available * PreferredBlocksPerTask);
for (size_t i = 0; i < slots_available && i < std::size(spans); ++i)
{
auto const& span = spans[i];
auto* const task = new tr_webseed_task{ tor, w, span };
evbuffer_add_cb(task->content(), onBufferGotData, task);
w->tasks.insert(task);
task_request_next_chunk(task);
tr_peerMgrClientSentRequests(tor, w, span);
}
}
void onPartialDataFetched(tr_web::FetchResponse const& web_response)
{
auto const& [status, body, did_connect, did_timeout, vtask] = web_response;
bool const success = status == 206;
auto* const task = static_cast<tr_webseed_task*>(vtask);
auto* const webseed = task->webseed;
webseed->connection_limiter.taskFinished(success);
if (task->dead)
{
delete task;
return;
}
if (auto const* const tor = webseed->getTorrent(); tor == nullptr)
{
return;
}
if (!success)
{
webseed->publishRejection({ task->loc.block, task->blocks.end });
webseed->tasks.erase(task);
delete task;
return;
}
if (task->loc.byte < task->end_byte)
{
// Request finished successfully but there's still data missing.
// That means we've reached the end of a file and need to request
// the next one
task_request_next_chunk(task);
return;
}
TR_ASSERT(evbuffer_get_length(task->content()) < tr_block_info::BlockSize);
webseed->tasks.erase(task);
delete task;
on_idle(webseed);
}
template<typename OutputIt>
void makeUrl(tr_webseed* w, std::string_view name, OutputIt out)
{
auto const url = w->base_url;
out = std::copy(std::begin(url), std::end(url), out);
if (tr_strvEndsWith(url, "/"sv) && !std::empty(name))
{
tr_http_escape(out, name, false);
}
}
void task_request_next_chunk(tr_webseed_task* task)
{
auto* const webseed = task->webseed;
auto* const tor = webseed->getTorrent();
if (tor == nullptr)
{
return;
}
auto const [file_index, file_offset] = tor->fileOffset(task->loc);
auto const left_in_file = tor->fileSize(file_index) - file_offset;
auto const left_in_task = task->end_byte - task->loc.byte;
auto const this_chunk = std::min(left_in_file, left_in_task);
webseed->connection_limiter.taskStarted();
auto url = tr_urlbuf{};
makeUrl(webseed, tor->fileSubpath(file_index), std::back_inserter(url));
auto options = tr_web::FetchOptions{ url.sv(), onPartialDataFetched, task };
options.range = fmt::format(FMT_STRING("{:d}-{:d}"), file_offset, file_offset + this_chunk - 1);
options.speed_limit_tag = tor->uniqueId;
options.buffer = task->content();
tor->session->web->fetch(std::move(options));
}
} // namespace
/***
****
***/
tr_peer* tr_webseedNew(tr_torrent* torrent, std::string_view url, tr_peer_callback callback, void* callback_data)
{
return new tr_webseed(torrent, url, callback, callback_data);
}
tr_webseed_view tr_webseedView(tr_peer const* peer)
{
auto const* w = dynamic_cast<tr_webseed const*>(peer);
if (w == nullptr)
{
return {};
}
auto bytes_per_second = unsigned{ 0 };
auto const is_downloading = peer->is_transferring_pieces(tr_time_msec(), TR_DOWN, &bytes_per_second);
return { w->base_url.c_str(), is_downloading, bytes_per_second };
}