transmission/libtransmission/webseed.cc

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// This file Copyright © 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 <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"
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#include "libtransmission/tr-strbuf.h"
#include "libtransmission/utils-ev.h"
#include "libtransmission/utils.h"
#include "libtransmission/web-utils.h"
#include "libtransmission/web.h"
#include "libtransmission/webseed.h"
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struct evbuffer;
using namespace std::literals;
using namespace libtransmission::Values;
namespace
{
class tr_webseed_impl;
class tr_webseed_task
{
public:
tr_webseed_task(tr_torrent const& tor, tr_webseed_impl* webseed_in, tr_block_span_t blocks_in)
: blocks{ blocks_in }
, webseed_{ webseed_in }
, session_{ tor.session }
, end_byte_{ tor.block_loc(blocks.end - 1).byte + tor.block_size(blocks.end - 1) }
, loc_{ tor.block_loc(blocks.begin) }
{
evbuffer_add_cb(content_.get(), on_buffer_got_data, this);
}
[[nodiscard]] auto* content() const
{
return content_.get();
}
void request_next_chunk();
bool dead = false;
tr_block_span_t const blocks;
private:
void use_fetched_blocks();
static void on_partial_data_fetched(tr_web::FetchResponse const& web_response);
static void on_buffer_got_data(evbuffer* /*buf*/, evbuffer_cb_info const* info, void* vtask);
tr_webseed_impl* const webseed_;
tr_session* const session_;
uint64_t const end_byte_;
// the current position in the task; i.e., the next block to save
tr_block_info::Location loc_;
libtransmission::evhelpers::evbuffer_unique_ptr const content_{ evbuffer_new() };
};
/**
* 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 task_started() noexcept
{
++n_tasks;
}
void task_finished(bool success)
{
if (!success)
{
task_failed();
}
TR_ASSERT(n_tasks > 0);
--n_tasks;
}
constexpr void got_data() noexcept
{
TR_ASSERT(n_tasks > 0);
n_consecutive_failures = 0;
paused_until = 0;
}
[[nodiscard]] size_t slots_available() const noexcept
{
if (is_paused())
{
return 0;
}
auto const max = max_connections();
if (n_tasks >= max)
{
return 0;
}
return max - n_tasks;
}
private:
[[nodiscard]] bool is_paused() const noexcept
{
return paused_until > tr_time();
}
[[nodiscard]] constexpr size_t max_connections() const noexcept
{
return n_consecutive_failures > 0 ? 1 : MaxConnections;
}
void task_failed()
{
TR_ASSERT(n_tasks > 0);
if (++n_consecutive_failures >= MaxConsecutiveFailures)
{
paused_until = tr_time() + TimeoutIntervalSecs;
}
}
static auto constexpr TimeoutIntervalSecs = time_t{ 120 };
static auto constexpr MaxConnections = size_t{ 4 };
static auto constexpr MaxConsecutiveFailures = MaxConnections;
size_t n_tasks = 0;
size_t n_consecutive_failures = 0;
time_t paused_until = 0;
};
class tr_webseed_impl final : public tr_webseed
{
public:
struct RequestLimit
{
// How many spans those blocks could be in.
// This is for webseeds, which make parallel requests.
size_t max_spans = 0;
// How many blocks we could request.
size_t max_blocks = 0;
};
tr_webseed_impl(tr_torrent& tor_in, std::string_view url, tr_peer_callback_webseed callback_in, void* callback_data_in)
: tr_webseed{ tor_in }
, tor{ tor_in }
, base_url{ url }
, idle_timer_{ session->timerMaker().create([this]() { on_idle(); }) }
, have_{ tor_in.piece_count() }
, bandwidth_{ &tor_in.bandwidth() }
, callback_{ callback_in }
, callback_data_{ callback_data_in }
{
have_.set_has_all();
idle_timer_->start_repeating(IdleTimerInterval);
}
tr_webseed_impl(tr_webseed_impl&&) = delete;
tr_webseed_impl(tr_webseed_impl const&) = delete;
tr_webseed_impl& operator=(tr_webseed_impl&&) = delete;
tr_webseed_impl& operator=(tr_webseed_impl const&) = delete;
~tr_webseed_impl() 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]] Speed get_piece_speed(uint64_t now, tr_direction dir) const override
{
return dir == TR_DOWN ? bandwidth_.get_piece_speed(now, dir) : Speed{};
}
[[nodiscard]] tr_webseed_view get_view() const override
{
auto const is_downloading = !std::empty(tasks);
auto const speed = get_piece_speed(tr_time_msec(), TR_DOWN);
return { base_url.c_str(), is_downloading, speed.base_quantity() };
}
[[nodiscard]] TR_CONSTEXPR20 size_t active_req_count(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))
{
return fmt::format("{:s}:{:d}", parsed->host, parsed->port);
}
return base_url;
}
[[nodiscard]] tr_bitfield const& has() const noexcept override
{
return have_;
}
void got_piece_data(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.got_data();
}
void publish_rejection(tr_block_span_t block_span)
{
for (auto block = block_span.begin; block < block_span.end; ++block)
{
publish(tr_peer_event::GotRejected(tor.block_info(), block));
}
}
void request_blocks(tr_block_span_t const* block_spans, size_t n_spans) override
{
if (!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 };
tasks.insert(task);
task->request_next_chunk();
tr_peerMgrClientSentRequests(&tor, this, *span);
}
}
void on_idle()
{
auto const [max_spans, max_blocks] = max_available_reqs();
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(&tor, this, max_blocks);
if (std::size(spans) > max_spans)
{
spans.resize(max_spans);
}
request_blocks(std::data(spans), std::size(spans));
}
[[nodiscard]] RequestLimit max_available_reqs() const noexcept
{
auto const n_slots = connection_limiter.slots_available();
if (n_slots == 0)
{
return {};
}
if (!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.
static 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)
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{
(*callback_)(this, peer_event, callback_data_);
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}
}
tr_torrent& tor;
std::string const base_url;
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_;
tr_peer_callback_webseed const callback_;
void* const callback_data_;
};
// ---
void tr_webseed_task::use_fetched_blocks()
{
auto const lock = session_->unique_lock();
auto const& tor = webseed_->tor;
for (auto* const buf = content();;)
{
auto const block_size = tor.block_size(loc_.block);
if (evbuffer_get_length(buf) < block_size)
{
break;
}
if (tor.has_block(loc_.block))
{
evbuffer_drain(buf, block_size);
}
else
{
auto block_buf = new Cache::BlockData(block_size);
evbuffer_remove(buf, std::data(*block_buf), std::size(*block_buf));
session_->run_in_session_thread(
[session = session_, tor_id = tor.id(), block = loc_.block, block_buf, webseed = webseed_]()
{
auto data = std::unique_ptr<Cache::BlockData>{ block_buf };
if (auto const* const torrent = tr_torrentFindFromId(session, tor_id); torrent != nullptr)
{
session->cache->write_block(tor_id, block, std::move(data));
webseed->publish(tr_peer_event::GotBlock(torrent->block_info(), block));
}
});
}
loc_ = tor.byte_loc(loc_.byte + block_size);
TR_ASSERT(loc_.byte <= end_byte_);
TR_ASSERT(loc_.byte == end_byte_ || loc_.block_offset == 0);
}
}
// ---
void tr_webseed_task::on_buffer_got_data(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_->got_piece_data(n_added);
}
void tr_webseed_task::on_partial_data_fetched(tr_web::FetchResponse const& web_response)
{
auto const& [status, body, primary_ip, did_connect, did_timeout, vtask] = web_response;
auto 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.task_finished(success);
if (!success)
{
webseed->publish_rejection({ task->loc_.block, task->blocks.end });
webseed->tasks.erase(task);
delete task;
return;
}
task->use_fetched_blocks();
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();
return;
}
TR_ASSERT(evbuffer_get_length(task->content()) == 0);
TR_ASSERT(task->loc_.byte == task->end_byte_);
webseed->tasks.erase(task);
delete task;
webseed->on_idle();
}
template<typename OutputIt>
void makeUrl(tr_webseed_impl 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 tr_webseed_task::request_next_chunk()
{
auto const& tor = webseed_->tor;
auto const downloaded_loc = tor.byte_loc(loc_.byte + evbuffer_get_length(content()));
auto const [file_index, file_offset] = tor.file_offset(downloaded_loc);
auto const left_in_file = tor.file_size(file_index) - file_offset;
auto const left_in_task = end_byte_ - downloaded_loc.byte;
auto const this_chunk = std::min(left_in_file, left_in_task);
TR_ASSERT(this_chunk > 0U);
webseed_->connection_limiter.task_started();
auto url = tr_urlbuf{};
makeUrl(webseed_, tor.file_subpath(file_index), std::back_inserter(url));
auto options = tr_web::FetchOptions{ url.sv(), on_partial_data_fetched, this };
options.range = fmt::format("{:d}-{:d}", file_offset, file_offset + this_chunk - 1);
options.speed_limit_tag = tor.id();
options.buffer = content();
tor.session->fetch(std::move(options));
}
} // namespace
// ---
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std::unique_ptr<tr_webseed> tr_webseed::create(
tr_torrent& torrent,
std::string_view url,
tr_peer_callback_webseed callback,
void* callback_data)
{
return std::make_unique<tr_webseed_impl>(torrent, url, callback, callback_data);
}