transmission/libtransmission/torrent-magnet.cc

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/*
* This file Copyright (C) 2012-2014 Mnemosyne LLC
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*
* It may be used under the GNU GPL versions 2 or 3
* or any future license endorsed by Mnemosyne LLC.
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*
*/
#include <algorithm>
#include <climits> /* INT_MAX */
#include <cstring> /* memcpy(), memset(), memcmp() */
#include <ctime>
#include <string_view>
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#include <event2/buffer.h>
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#include "transmission.h"
#include "crypto-utils.h" /* tr_sha1() */
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#include "error.h"
#include "file.h"
#include "log.h"
#include "magnet-metainfo.h"
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#include "metainfo.h"
#include "resume.h"
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#include "torrent-magnet.h"
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#include "torrent-metainfo.h"
#include "torrent.h"
#include "tr-assert.h"
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#include "utils.h"
#include "variant.h"
#include "web-utils.h"
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using namespace std::literals;
#define dbgmsg(tor, ...) tr_logAddDeepNamed(tr_torrentName(tor), __VA_ARGS__)
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/***
****
***/
/* don't ask for the same metadata piece more than this often */
static auto constexpr MinRepeatIntervalSecs = int{ 3 };
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struct metadata_node
{
time_t requestedAt;
int piece;
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};
struct tr_incomplete_metadata
{
char* metadata;
size_t metadata_size;
int pieceCount;
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/** sorted from least to most recently requested */
struct metadata_node* piecesNeeded;
int piecesNeededCount;
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};
static void incompleteMetadataFree(struct tr_incomplete_metadata* m)
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{
tr_free(m->metadata);
tr_free(m->piecesNeeded);
tr_free(m);
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}
bool tr_torrentSetMetadataSizeHint(tr_torrent* tor, int64_t size)
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{
if (tor->hasMetadata())
{
return false;
}
if (tor->incompleteMetadata != nullptr)
{
return false;
}
int const n = (size <= 0 || size > INT_MAX) ? -1 : size / METADATA_PIECE_SIZE + (size % METADATA_PIECE_SIZE != 0 ? 1 : 0);
dbgmsg(tor, "metadata is %" PRId64 " bytes in %d pieces", size, n);
if (n <= 0)
{
return false;
}
struct tr_incomplete_metadata* m = tr_new(struct tr_incomplete_metadata, 1);
if (m == nullptr)
{
return false;
}
m->pieceCount = n;
m->metadata = tr_new(char, size);
m->metadata_size = size;
m->piecesNeededCount = n;
m->piecesNeeded = tr_new(struct metadata_node, n);
if (m->metadata == nullptr || m->piecesNeeded == nullptr)
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{
incompleteMetadataFree(m);
return false;
}
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for (int i = 0; i < n; ++i)
{
m->piecesNeeded[i].piece = i;
m->piecesNeeded[i].requestedAt = 0;
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}
tor->incompleteMetadata = m;
return true;
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}
static size_t findInfoDictOffset(tr_torrent const* tor)
{
// load the torrent's .torrent file
auto benc = std::vector<char>{};
if (!tr_loadFile(benc, tor->torrentFile()) || std::empty(benc))
{
return {};
}
// parse the benc
auto top = tr_variant{};
auto const benc_sv = std::string_view{ std::data(benc), std::size(benc) };
if (!tr_variantFromBuf(&top, TR_VARIANT_PARSE_BENC | TR_VARIANT_PARSE_INPLACE, benc_sv))
{
return {};
}
auto offset = size_t{};
tr_variant* info_dict = nullptr;
if (tr_variantDictFindDict(&top, TR_KEY_info, &info_dict))
{
auto const info_dict_benc = tr_variantToStr(info_dict, TR_VARIANT_FMT_BENC);
auto const it = std::search(std::begin(benc), std::end(benc), std::begin(info_dict_benc), std::end(info_dict_benc));
if (it != std::end(benc))
{
offset = std::distance(std::begin(benc), it);
}
}
tr_variantFree(&top);
return offset;
}
static void ensureInfoDictOffsetIsCached(tr_torrent* tor)
{
TR_ASSERT(tor->hasMetadata());
if (!tor->info_dict_offset_is_cached)
{
tor->info_dict_offset = findInfoDictOffset(tor);
tor->info_dict_offset_is_cached = true;
}
}
void* tr_torrentGetMetadataPiece(tr_torrent* tor, int piece, size_t* len)
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{
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(piece >= 0);
TR_ASSERT(len != nullptr);
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if (!tor->hasMetadata())
{
return nullptr;
}
auto const fd = tr_sys_file_open(tor->torrentFile().c_str(), TR_SYS_FILE_READ, 0, nullptr);
if (fd == TR_BAD_SYS_FILE)
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{
return nullptr;
}
ensureInfoDictOffsetIsCached(tor);
auto const info_dict_size = tor->infoDictSize();
TR_ASSERT(info_dict_size > 0);
char* ret = nullptr;
if (size_t o = piece * METADATA_PIECE_SIZE; tr_sys_file_seek(fd, tor->infoDictOffset() + o, TR_SEEK_SET, nullptr, nullptr))
{
size_t const l = o + METADATA_PIECE_SIZE <= info_dict_size ? METADATA_PIECE_SIZE : info_dict_size - o;
if (0 < l && l <= METADATA_PIECE_SIZE)
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{
char* buf = tr_new(char, l);
auto n = uint64_t{};
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if (tr_sys_file_read(fd, buf, l, &n, nullptr) && n == l)
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{
*len = l;
ret = buf;
buf = nullptr;
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}
tr_free(buf);
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}
}
tr_sys_file_close(fd, nullptr);
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TR_ASSERT(ret == nullptr || *len > 0);
return ret;
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}
static int getPieceNeededIndex(struct tr_incomplete_metadata const* m, int piece)
{
for (int i = 0; i < m->piecesNeededCount; ++i)
{
if (m->piecesNeeded[i].piece == piece)
{
return i;
}
}
return -1;
}
static int getPieceLength(struct tr_incomplete_metadata const* m, int piece)
{
return piece + 1 == m->pieceCount ? // last piece
m->metadata_size - (piece * METADATA_PIECE_SIZE) :
METADATA_PIECE_SIZE;
}
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static void tr_buildMetainfoExceptInfoDict(tr_info const& tm, tr_variant* top)
{
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tr_variantInitDict(top, 6);
if (auto const& val = tm.comment(); !std::empty(val))
{
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tr_variantDictAddStr(top, TR_KEY_comment, val);
}
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if (auto const& val = tm.source(); !std::empty(val))
{
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tr_variantDictAddStr(top, TR_KEY_source, val);
}
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if (auto const& val = tm.creator(); !std::empty(val))
{
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tr_variantDictAddStr(top, TR_KEY_created_by, val);
}
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if (auto const val = tm.dateCreated(); val != 0)
{
tr_variantDictAddInt(top, TR_KEY_creation_date, val);
}
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if (auto const& announce_list = tm.announceList(); !std::empty(announce_list))
{
auto const n = std::size(announce_list);
if (n == 1)
{
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tr_variantDictAddStr(top, TR_KEY_announce, announce_list.at(0).announce_str.sv());
}
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else
{
auto* const announce_list_variant = tr_variantDictAddList(top, TR_KEY_announce_list, n);
tr_variant* tier_variant = nullptr;
auto current_tier = std::optional<tr_tracker_tier_t>{};
for (auto const& tracker : announce_list)
{
if (!current_tier || *current_tier != tracker.tier)
{
tier_variant = tr_variantListAddList(announce_list_variant, n);
}
tr_variantListAddStr(tier_variant, tracker.announce_str.sv());
}
}
}
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if (auto const n_webseeds = tm.webseedCount(); n_webseeds > 0)
{
auto* const webseeds_variant = tr_variantDictAddList(top, TR_KEY_url_list, n_webseeds);
for (size_t i = 0; i < n_webseeds; ++i)
{
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tr_variantListAddStr(webseeds_variant, tm.webseed(i));
}
}
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if (tm.fileCount() == 0)
{
// local transmission extensions.
// these temporary placeholders are used for magnets until we have the info dict.
auto* const magnet_info = tr_variantDictAddDict(top, TR_KEY_magnet_info, 2);
tr_variantDictAddStr(
magnet_info,
TR_KEY_info_hash,
std::string_view{ reinterpret_cast<char const*>(std::data(tm.infoHash())), std::size(tm.infoHash()) });
if (auto const& val = tm.name(); !std::empty(val))
{
tr_variantDictAddStr(magnet_info, TR_KEY_display_name, val);
}
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}
}
static bool useNewMetainfo(tr_torrent* tor, tr_incomplete_metadata* m, tr_error** error)
{
auto const sha1 = tr_sha1(std::string_view{ m->metadata, m->metadata_size });
bool const checksum_passed = sha1 && *sha1 == tor->infoHash();
if (!checksum_passed)
{
return false;
}
// checksum passed; now try to parse it as benc
auto info_dict_v = tr_variant{};
auto const info_dict_sv = std::string_view{ m->metadata, m->metadata_size };
if (!tr_variantFromBuf(&info_dict_v, TR_VARIANT_PARSE_BENC | TR_VARIANT_PARSE_INPLACE, info_dict_sv, nullptr, error))
{
return false;
}
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// yay we have an info dict. Let's make a .torrent file
auto top_v = tr_variant{};
tr_buildMetainfoExceptInfoDict(tor->info, &top_v);
tr_variantMergeDicts(tr_variantDictAddDict(&top_v, TR_KEY_info, 0), &info_dict_v);
auto const benc = tr_variantToStr(&top_v, TR_VARIANT_FMT_BENC);
// does this synthetic .torrent file parse?
auto parsed = tr_metainfoParse(tor->session, &top_v, error);
tr_variantFree(&top_v);
tr_variantFree(&info_dict_v);
if (!parsed)
{
return false;
}
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// save it
auto const& torrent_dir = tor->session->torrent_dir;
auto const filename = tr_magnet_metainfo::makeFilename(
torrent_dir,
tor->name(),
tor->infoHashString(),
tr_magnet_metainfo::BasenameFormat::Hash,
".torrent"sv);
if (!tr_saveFile(filename, benc, error))
{
return false;
}
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// tor should keep this metainfo
tor->swapMetainfo(*parsed);
tr_torrentGotNewInfoDict(tor);
tor->setDirty();
return true;
}
static void onHaveAllMetainfo(tr_torrent* tor, tr_incomplete_metadata* m)
{
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tr_error* error = nullptr;
if (useNewMetainfo(tor, m, &error))
{
incompleteMetadataFree(tor->incompleteMetadata);
tor->incompleteMetadata = nullptr;
tor->isStopping = true;
tor->magnetVerify = true;
tor->startAfterVerify = !tor->prefetchMagnetMetadata;
tor->markEdited();
}
else /* drat. */
{
int const n = m->pieceCount;
for (int i = 0; i < n; ++i)
{
m->piecesNeeded[i].piece = i;
m->piecesNeeded[i].requestedAt = 0;
}
m->piecesNeededCount = n;
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char const* const msg = error != nullptr && error->message != nullptr ? error->message : "unknown error";
dbgmsg(tor, "metadata error: %s. (trying again; %d pieces left)", msg, n);
tr_error_clear(&error);
}
}
void tr_torrentSetMetadataPiece(tr_torrent* tor, int piece, void const* data, int len)
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{
TR_ASSERT(tr_isTorrent(tor));
TR_ASSERT(data != nullptr);
TR_ASSERT(len >= 0);
dbgmsg(tor, "got metadata piece %d of %d bytes", piece, len);
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// are we set up to download metadata?
tr_incomplete_metadata* const m = tor->incompleteMetadata;
if (m == nullptr)
{
return;
}
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// sanity test: is `piece` in range?
if ((piece < 0) || (piece >= m->pieceCount))
{
return;
}
// sanity test: is `len` the right size?
if (getPieceLength(m, piece) != len)
{
return;
}
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// do we need this piece?
int const idx = getPieceNeededIndex(m, piece);
if (idx == -1)
{
return;
}
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size_t const offset = piece * METADATA_PIECE_SIZE;
std::copy_n(reinterpret_cast<char const*>(data), len, m->metadata + offset);
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tr_removeElementFromArray(m->piecesNeeded, idx, sizeof(struct metadata_node), m->piecesNeededCount);
--m->piecesNeededCount;
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dbgmsg(tor, "saving metainfo piece %d... %d remain", piece, m->piecesNeededCount);
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/* are we done? */
if (m->piecesNeededCount == 0)
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{
dbgmsg(tor, "metainfo piece %d was the last one", piece);
onHaveAllMetainfo(tor, m);
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}
}
bool tr_torrentGetNextMetadataRequest(tr_torrent* tor, time_t now, int* setme_piece)
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{
TR_ASSERT(tr_isTorrent(tor));
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bool have_request = false;
struct tr_incomplete_metadata* m = tor->incompleteMetadata;
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if (m != nullptr && m->piecesNeededCount > 0 && m->piecesNeeded[0].requestedAt + MinRepeatIntervalSecs < now)
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{
int const piece = m->piecesNeeded[0].piece;
tr_removeElementFromArray(m->piecesNeeded, 0, sizeof(struct metadata_node), m->piecesNeededCount);
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int i = m->piecesNeededCount - 1;
m->piecesNeeded[i].piece = piece;
m->piecesNeeded[i].requestedAt = now;
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dbgmsg(tor, "next piece to request: %d", piece);
*setme_piece = piece;
have_request = true;
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}
return have_request;
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}
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double tr_torrentGetMetadataPercent(tr_torrent const* tor)
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{
if (tor->hasMetadata())
{
return 1.0;
}
auto const* const m = tor->incompleteMetadata;
return m == nullptr || m->pieceCount == 0 ? 0.0 : (m->pieceCount - m->piecesNeededCount) / (double)m->pieceCount;
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}
/* TODO: this should be renamed tr_metainfoGetMagnetLink() and moved to metainfo.c for consistency */
char* tr_torrentInfoGetMagnetLink(tr_info const* inf)
{
auto buf = std::string{};
buf += "magnet:?xt=urn:btih:"sv;
buf += inf->infoHashString();
auto const& name = inf->name();
if (!std::empty(name))
{
buf += "&dn="sv;
tr_http_escape(buf, name, true);
}
for (size_t i = 0, n = std::size(*inf->announce_list); i < n; ++i)
{
buf += "&tr="sv;
tr_http_escape(buf, inf->announce_list->at(i).announce.full, true);
}
for (size_t i = 0, n = inf->webseedCount(); i < n; ++i)
{
buf += "&ws="sv;
tr_http_escape(buf, inf->webseed(i), true);
}
return tr_strvDup(buf);
}
char* tr_torrentGetMagnetLink(tr_torrent const* tor)
{
return tr_torrentInfoGetMagnetLink(&tor->info);
}