transmission/libtransmission/torrent-magnet.c

/*
 * This file Copyright (C) Mnemosyne LLC
 *
 * This file is licensed by the GPL version 2. Works owned by the
 * Transmission project are granted a special exemption to clause 2 (b)
 * so that the bulk of its code can remain under the MIT license.
 * This exemption does not extend to derived works not owned by
 * the Transmission project.
 *
 * $Id$
 */

#include <assert.h>
#include <stdio.h> /* remove () */
#include <string.h> /* memcpy (), memset (), memcmp () */

#include <event2/buffer.h>

#include "transmission.h"
#include "crypto.h" /* tr_sha1 () */
#include "magnet.h"
#include "metainfo.h"
#include "resume.h"
#include "torrent.h"
#include "torrent-magnet.h"
#include "utils.h"
#include "variant.h"
#include "web.h"

#define dbgmsg(tor, ...) \
  do \
    { \
      if (tr_deepLoggingIsActive ()) \
        tr_deepLog (__FILE__, __LINE__, tr_torrentName (tor), __VA_ARGS__); \
    } \
  while (0)

/***
****
***/

enum
{
    /* don't ask for the same metadata piece more than this often */
    MIN_REPEAT_INTERVAL_SECS = 3
};

struct metadata_node
{
    time_t requestedAt;
    int piece;
};

struct tr_incomplete_metadata
{
    uint8_t * metadata;
    int metadata_size;
    int pieceCount;

    /** sorted from least to most recently requested */
    struct metadata_node * piecesNeeded;
    int piecesNeededCount;
};

static void
incompleteMetadataFree (struct tr_incomplete_metadata * m)
{
    tr_free (m->metadata);
    tr_free (m->piecesNeeded);
    tr_free (m);
}

void
tr_torrentSetMetadataSizeHint (tr_torrent * tor, int size)
{
    if (!tr_torrentHasMetadata (tor))
    {
        if (tor->incompleteMetadata == NULL)
        {
            int i;
            struct tr_incomplete_metadata * m;
            const int n = (size + (METADATA_PIECE_SIZE - 1)) / METADATA_PIECE_SIZE;
            dbgmsg (tor, "metadata is %d bytes in %d pieces", size, n);

            m = tr_new (struct tr_incomplete_metadata, 1);
            m->pieceCount = n;
            m->metadata = tr_new (uint8_t, size);
            m->metadata_size = size;
            m->piecesNeededCount = n;
            m->piecesNeeded = tr_new (struct metadata_node, n);

            for (i=0; i<n; ++i) {
                m->piecesNeeded[i].piece = i;
                m->piecesNeeded[i].requestedAt = 0;
            }

            tor->incompleteMetadata = m;
        }
    }
}

static int
findInfoDictOffset (const tr_torrent * tor)
{
    size_t fileLen;
    uint8_t * fileContents;
    int offset = 0;

    /* load the file, and find the info dict's offset inside the file */
    if ((fileContents = tr_loadFile (tor->info.torrent, &fileLen)))
    {
        tr_variant top;

        if (!tr_variantFromBenc (&top, fileContents, fileLen))
        {
            tr_variant * infoDict;

            if (tr_variantDictFindDict (&top, TR_KEY_info, &infoDict))
            {
                int infoLen;
                char * infoContents = tr_variantToStr (infoDict, TR_VARIANT_FMT_BENC, &infoLen);
                const uint8_t * i = (const uint8_t*) tr_memmem ((char*)fileContents, fileLen, infoContents, infoLen);
                offset = i != NULL ? i - fileContents : 0;
                tr_free (infoContents);
            }

            tr_variantFree (&top);
        }

        tr_free (fileContents);
    }

    return offset;
}

static void
ensureInfoDictOffsetIsCached (tr_torrent * tor)
{
    assert (tr_torrentHasMetadata (tor));

    if (!tor->infoDictOffsetIsCached)
    {
        tor->infoDictOffset = findInfoDictOffset (tor);
        tor->infoDictOffsetIsCached = true;
    }
}

void*
tr_torrentGetMetadataPiece (tr_torrent * tor, int piece, int * len)
{
    char * ret = NULL;

    assert (tr_isTorrent (tor));
    assert (piece >= 0);
    assert (len != NULL);

    if (tr_torrentHasMetadata (tor))
    {
        FILE * fp;

        ensureInfoDictOffsetIsCached (tor);

        assert (tor->infoDictLength > 0);
        assert (tor->infoDictOffset >= 0);

        fp = fopen (tor->info.torrent, "rb");
        if (fp != NULL)
        {
            const int o = piece  * METADATA_PIECE_SIZE;

            if (!fseek (fp, tor->infoDictOffset + o, SEEK_SET))
            {
                const int l = o + METADATA_PIECE_SIZE <= tor->infoDictLength
                            ? METADATA_PIECE_SIZE
                            : tor->infoDictLength - o;

                if (0<l && l<=METADATA_PIECE_SIZE)
                {
                    char * buf = tr_new (char, l);
                    const int n = fread (buf, 1, l, fp);
                    if (n == l)
                    {
                        *len = l;
                        ret = buf;
                        buf = NULL;
                    }

                    tr_free (buf);
                }
            }

            fclose (fp);
        }
    }

    return ret;
}

void
tr_torrentSetMetadataPiece (tr_torrent  * tor, int piece, const void  * data, int len)
{
    int i;
    struct tr_incomplete_metadata * m;
    const int offset = piece * METADATA_PIECE_SIZE;

    assert (tr_isTorrent (tor));

    dbgmsg (tor, "got metadata piece %d", piece);

    /* are we set up to download metadata? */
    m = tor->incompleteMetadata;
    if (m == NULL)
        return;

    /* does this data pass the smell test? */
    if (offset + len > m->metadata_size)
        return;

    /* do we need this piece? */
    for (i=0; i<m->piecesNeededCount; ++i)
        if (m->piecesNeeded[i].piece == piece)
            break;
    if (i==m->piecesNeededCount)
        return;

    memcpy (m->metadata + offset, data, len);

    tr_removeElementFromArray (m->piecesNeeded, i,
                               sizeof (struct metadata_node),
                               m->piecesNeededCount--);

    dbgmsg (tor, "saving metainfo piece %d... %d remain", piece, m->piecesNeededCount);

    /* are we done? */
    if (m->piecesNeededCount == 0)
    {
        bool success = false;
        bool checksumPassed = false;
        bool metainfoParsed = false;
        uint8_t sha1[SHA_DIGEST_LENGTH];

        /* we've got a complete set of metainfo... see if it passes the checksum test */
        dbgmsg (tor, "metainfo piece %d was the last one", piece);
        tr_sha1 (sha1, m->metadata, m->metadata_size, NULL);
        if ((checksumPassed = !memcmp (sha1, tor->info.hash, SHA_DIGEST_LENGTH)))
        {
            /* checksum passed; now try to parse it as benc */
            tr_variant infoDict;
            const int err = tr_variantFromBenc (&infoDict, m->metadata, m->metadata_size);
            dbgmsg (tor, "err is %d", err);
            if ((metainfoParsed = !err))
            {
                /* yay we have bencoded metainfo... merge it into our .torrent file */
                tr_variant newMetainfo;
                char * path = tr_strdup (tor->info.torrent);

                if (!tr_variantFromFile (&newMetainfo, TR_VARIANT_FMT_BENC, path))
                {
                    bool hasInfo;
                    tr_info info;
                    int infoDictLength;

                    /* remove any old .torrent and .resume files */
                    remove (path);
                    tr_torrentRemoveResume (tor);

                    dbgmsg (tor, "Saving completed metadata to \"%s\"", path);
                    tr_variantMergeDicts (tr_variantDictAddDict (&newMetainfo, TR_KEY_info, 0), &infoDict);

                    memset (&info, 0, sizeof (tr_info));
                    success = tr_metainfoParse (tor->session, &newMetainfo, &info, &hasInfo, &infoDictLength);

                    if (success && !tr_getBlockSize (info.pieceSize))
                    {
                        tr_torrentSetLocalError (tor, "%s", _("Magnet torrent's metadata is not usable"));
                        success = false;
                    }

                    if (success)
                    {
                        /* keep the new info */
                        tor->info = info;
                        tor->infoDictLength = infoDictLength;

                        /* save the new .torrent file */
                        tr_variantToFile (&newMetainfo, TR_VARIANT_FMT_BENC, tor->info.torrent);
                        tr_sessionSetTorrentFile (tor->session, tor->info.hashString, tor->info.torrent);
                        tr_torrentGotNewInfoDict (tor);
                        tr_torrentSetDirty (tor);
                    }

                    tr_variantFree (&newMetainfo);
                }

                tr_variantFree (&infoDict);
                tr_free (path);
            }
        }

        if (success)
        {
            incompleteMetadataFree (tor->incompleteMetadata);
            tor->incompleteMetadata = NULL;
        }
        else /* drat. */
        {
            const int n = m->pieceCount;
            for (i=0; i<n; ++i)
            {
                m->piecesNeeded[i].piece = i;
                m->piecesNeeded[i].requestedAt = 0;
            }
            m->piecesNeededCount = n;
            dbgmsg (tor, "metadata error; trying again. %d pieces left", n);

            tr_err ("magnet status: checksum passed %d, metainfo parsed %d",
                  (int)checksumPassed, (int)metainfoParsed);
        }
    }
}

bool
tr_torrentGetNextMetadataRequest (tr_torrent * tor, time_t now, int * setme_piece)
{
    bool have_request = false;
    struct tr_incomplete_metadata * m;

    assert (tr_isTorrent (tor));

    m = tor->incompleteMetadata;

    if ((m != NULL)
        && (m->piecesNeededCount > 0)
        && (m->piecesNeeded[0].requestedAt + MIN_REPEAT_INTERVAL_SECS < now))
    {
        int i;
        const int piece = m->piecesNeeded[0].piece;

        tr_removeElementFromArray (m->piecesNeeded, 0,
                                   sizeof (struct metadata_node),
                                   m->piecesNeededCount--);

        i = m->piecesNeededCount++;
        m->piecesNeeded[i].piece = piece;
        m->piecesNeeded[i].requestedAt = now;

        dbgmsg (tor, "next piece to request: %d", piece);
        *setme_piece = piece;
        have_request = true;
    }

    return have_request;
}

double
tr_torrentGetMetadataPercent (const tr_torrent * tor)
{
    double ret;

    if (tr_torrentHasMetadata (tor))
        ret = 1.0;
    else {
        const struct tr_incomplete_metadata * m = tor->incompleteMetadata;
        if (!m || !m->pieceCount)
            ret = 0.0;
        else
            ret = (m->pieceCount - m->piecesNeededCount) / (double)m->pieceCount;
    }

    return ret;
}

char*
tr_torrentInfoGetMagnetLink (const tr_info * inf)
{
    int i;
    const char * name;
    struct evbuffer * s = evbuffer_new ();

    evbuffer_add_printf (s, "magnet:?xt=urn:btih:%s", inf->hashString);

    name = inf->name;
    if (name && *name)
    {
        evbuffer_add_printf (s, "%s", "&dn=");
        tr_http_escape (s, name, -1, true);
    }

    for (i=0; i<inf->trackerCount; ++i)
    {
        evbuffer_add_printf (s, "%s", "&tr=");
        tr_http_escape (s, inf->trackers[i].announce, -1, true);
    }

    return evbuffer_free_to_str (s);
}