transmission/libtransmission/webseed.cc

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// This file Copyright © 2008-2023 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>
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#include <cstdint> // uint64_t, uint32_t
#include <ctime>
#include <iterator>
#include <memory>
#include <numeric> // std::accumulate()
#include <set>
#include <string>
#include <string_view>
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#include <utility>
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#include <vector>
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#include <event2/buffer.h>
#include <fmt/core.h>
#include "libtransmission/transmission.h"
#include "libtransmission/bandwidth.h"
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#include "libtransmission/bitfield.h"
#include "libtransmission/block-info.h"
#include "libtransmission/cache.h"
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#include "libtransmission/peer-common.h"
#include "libtransmission/peer-mgr.h"
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#include "libtransmission/session.h"
#include "libtransmission/timer.h"
#include "libtransmission/torrent.h"
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#include "libtransmission/tr-assert.h"
#include "libtransmission/tr-macros.h"
#include "libtransmission/utils-ev.h"
#include "libtransmission/utils.h"
#include "libtransmission/web-utils.h"
#include "libtransmission/web.h"
#include "libtransmission/webseed.h"
using namespace std::literals;
namespace
{
class tr_webseed;
void on_idle(tr_webseed* w);
class tr_webseed_task
{
private:
libtransmission::evhelpers::evbuffer_unique_ptr const content_{ evbuffer_new() };
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->block_loc(blocks.end - 1).byte + tor->block_size(blocks.end - 1) }
, loc{ tor->block_loc(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;
};
void task_request_next_chunk(tr_webseed_task* task);
void onBufferGotData(evbuffer* /*buf*/, evbuffer_cb_info const* info, void* vtask);
class tr_webseed final : public tr_peer
{
public:
tr_webseed(struct tr_torrent* tor, std::string_view url, tr_peer_callback_webseed 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 }
, idle_timer_{ session->timerMaker().create([this]() { on_idle(this); }) }
, have_{ tor->piece_count() }
, bandwidth_{ &tor->bandwidth_ }
{
have_.set_has_all();
idle_timer_->start_repeating(IdleTimerInterval);
}
tr_webseed(tr_webseed&&) = delete;
tr_webseed(tr_webseed const&) = delete;
tr_webseed& operator=(tr_webseed&&) = delete;
tr_webseed& operator=(tr_webseed const&) = delete;
~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 isTransferringPieces( //
uint64_t now,
tr_direction dir,
tr_bytes_per_second_t* setme_bytes_per_second) const override
{
tr_bytes_per_second_t bytes_per_second = 0;
bool is_active = false;
if (dir == TR_DOWN)
{
is_active = !std::empty(tasks);
bytes_per_second = bandwidth_.get_piece_speed_bytes_per_second(now, dir);
}
if (setme_bytes_per_second != nullptr)
{
*setme_bytes_per_second = bytes_per_second;
}
return is_active;
}
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[[nodiscard]] TR_CONSTEXPR20 size_t activeReqCount(tr_direction dir) const noexcept override
{
if (dir == TR_CLIENT_TO_PEER) // blocks we've requested
{
return std::accumulate(
std::begin(tasks),
std::end(tasks),
size_t{},
[](size_t sum, auto const* task) { return sum + (task->blocks.end - task->blocks.begin); });
}
// webseed will never request blocks from us
return {};
}
[[nodiscard]] std::string display_name() const override
{
if (auto const parsed = tr_urlParse(base_url); parsed)
{
return fmt::format(FMT_STRING("{:s}:{:d}"), parsed->host, parsed->port);
}
return base_url;
}
[[nodiscard]] tr_bitfield const& has() const noexcept override
{
return have_;
}
void gotPieceData(uint32_t n_bytes)
{
bandwidth_.notify_bandwidth_consumed(TR_DOWN, n_bytes, true, tr_time_msec());
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publish(tr_peer_event::GotPieceData(n_bytes));
connection_limiter.gotData();
}
void publishRejection(tr_block_span_t block_span)
{
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auto const* const tor = getTorrent();
for (auto block = block_span.begin; block < block_span.end; ++block)
{
publish(tr_peer_event::GotRejected(tor->block_info(), block));
}
}
void requestBlocks(tr_block_span_t const* block_spans, size_t n_spans) override
{
auto* const tor = getTorrent();
if (tor == nullptr || !tor->is_running() || tor->is_done())
{
return;
}
for (auto const *span = block_spans, *end = span + n_spans; span != end; ++span)
{
auto* const task = new tr_webseed_task{ tor, this, *span };
evbuffer_add_cb(task->content(), onBufferGotData, task);
tasks.insert(task);
task_request_next_chunk(task);
tr_peerMgrClientSentRequests(tor, this, *span);
}
}
[[nodiscard]] RequestLimit canRequest() const noexcept override
{
auto const n_slots = connection_limiter.slotsAvailable();
if (n_slots == 0)
{
return {};
}
if (auto const* const tor = getTorrent(); tor == nullptr || !tor->is_running() || tor->is_done())
{
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 };
return { n_slots, n_slots * PreferredBlocksPerTask };
}
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void publish(tr_peer_event const& peer_event)
{
if (callback != nullptr)
{
(*callback)(this, peer_event, callback_data);
}
}
tr_torrent_id_t const torrent_id;
std::string const base_url;
tr_peer_callback_webseed const callback;
void* const callback_data;
ConnectionLimiter connection_limiter;
std::set<tr_webseed_task*> tasks;
private:
static auto constexpr IdleTimerInterval = 2s;
std::unique_ptr<libtransmission::Timer> const idle_timer_;
tr_bitfield have_;
tr_bandwidth bandwidth_;
};
// ---
struct write_block_data
{
private:
libtransmission::evhelpers::evbuffer_unique_ptr const content_{ evbuffer_new() };
public:
write_block_data(
tr_session* session,
tr_torrent_id_t tor_id,
tr_block_index_t block,
std::unique_ptr<Cache::BlockData> data,
tr_webseed* webseed)
: session_{ session }
, tor_id_{ tor_id }
, block_{ block }
, data_{ std::move(data) }
, webseed_{ webseed }
{
}
void write_block_func()
{
if (auto const* const tor = tr_torrentFindFromId(session_, tor_id_); tor != nullptr)
{
session_->cache->write_block(tor_id_, block_, std::move(data_));
webseed_->publish(tr_peer_event::GotBlock(tor->block_info(), block_));
}
delete this;
}
private:
tr_session* const session_;
tr_torrent_id_t const tor_id_;
tr_block_index_t const block_;
std::unique_ptr<Cache::BlockData> data_;
tr_webseed* const webseed_;
};
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->block_size(task->loc.block);
if (evbuffer_get_length(buf) < block_size)
{
break;
}
if (tor->has_block(task->loc.block))
{
evbuffer_drain(buf, block_size);
}
else
{
auto block_buf = std::make_unique<Cache::BlockData>(block_size);
evbuffer_remove(task->content(), std::data(*block_buf), std::size(*block_buf));
auto* const data = new write_block_data{ session, tor->id(), task->loc.block, std::move(block_buf), webseed };
session->runInSessionThread(&write_block_data::write_block_func, data);
}
task->loc = tor->byte_loc(task->loc.byte + block_size);
TR_ASSERT(task->loc.byte <= task->end_byte);
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 lock = task->session->unique_lock();
task->webseed->gotPieceData(n_added);
}
void on_idle(tr_webseed* webseed)
{
auto const [max_spans, max_blocks] = webseed->canRequest();
if (max_spans == 0 || max_blocks == 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 spans = tr_peerMgrGetNextRequests(webseed->getTorrent(), webseed, max_blocks);
if (std::size(spans) > max_spans)
{
spans.resize(max_spans);
}
webseed->requestBlocks(std::data(spans), std::size(spans));
}
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);
if (task->dead)
{
delete task;
return;
}
auto* const webseed = task->webseed;
webseed->connection_limiter.taskFinished(success);
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;
}
useFetchedBlocks(task);
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()) == 0);
TR_ASSERT(task->loc.byte == task->end_byte);
webseed->tasks.erase(task);
delete task;
on_idle(webseed);
}
template<typename OutputIt>
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void makeUrl(tr_webseed const* const webseed, std::string_view name, OutputIt out)
{
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auto const& url = webseed->base_url;
out = std::copy(std::begin(url), std::end(url), out);
if (tr_strv_ends_with(url, "/"sv) && !std::empty(name))
{
tr_urlPercentEncode(out, name, false);
}
}
void task_request_next_chunk(tr_webseed_task* task)
{
auto* const webseed = task->webseed;
auto const* const tor = webseed->getTorrent();
if (tor == nullptr)
{
return;
}
auto const loc = tor->byte_loc(task->loc.byte + evbuffer_get_length(task->content()));
auto const [file_index, file_offset] = tor->file_offset(loc);
auto const left_in_file = tor->file_size(file_index) - file_offset;
auto const left_in_task = task->end_byte - loc.byte;
auto const this_chunk = std::min(left_in_file, left_in_task);
TR_ASSERT(this_chunk > 0U);
webseed->connection_limiter.taskStarted();
auto url = tr_urlbuf{};
makeUrl(webseed, tor->file_subpath(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->id();
options.buffer = task->content();
tor->session->fetch(std::move(options));
}
} // namespace
// ---
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tr_peer* tr_webseedNew(tr_torrent* torrent, std::string_view url, tr_peer_callback_webseed 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 = tr_bytes_per_second_t{ 0 };
auto const is_downloading = peer->isTransferringPieces(tr_time_msec(), TR_DOWN, &bytes_per_second);
return { w->base_url.c_str(), is_downloading, bytes_per_second };
}