changelog

ctorrent源码

                        Enhanced CTorrent Change Log
     _________________________________________________________________

   Changes for "dnh2" Release

   Patches
     * The following patches or their functionality are incorporated:
       1380164 [dnh1.2]
       1357832 [invert] (included in dnh1.2)
       1352866 [dnh1.1]
       1266767 [passkey2]
       1239547 [dnh1]
       1170457 [standalone-sha1] Added as a fallback case in configure if
       OpenSSL is not found. To force it to be used, define
       USE_STANDALONE_SHA1 in config.h (after running configure).
       1164454 [ip]
       1119610 [vfat] This bug appears to be linux-specific; I've tried
       to handle it in a more general way that may apply to similar
       situations on other platforms and filesystems, but I have limited
       capability to test this.
       1067196 [lfs] This is the large-file support that many have asked
       for.

   Optimization
     * Use fewer call to random() by shifting the previously unused bits.
     * Time() calls have been greatly reduced; a global timestamp
       variable "now" is set once per main loop interation and referenced
       in functions that need a timestamp (except the caching I/O
       routines which were left alone).
     * Overall current bandwidth rates are now computed only once per
       main loop and referenced in any routines that evaluate or control
       bandwidth.
     * Avoid flushing peer output buffers except in SendModule. This
       allows for some consolidation of messages to reduce network
       overhead.

   Code Fixes
     * Fixed use of cfg_req_queue_length to be the actual queue size
       (queue was half of this value).
     * Fixed: "peer is" verbose output could fubar the terminal.
     * Formatting: Replaced indentation tabs with spaces for consistency.

   Operational Enhancements
     * Improved piece selection methods to include rarity as a factor.
       This is not strictly "rarest-first", as we do not make a
       comprehensive effort to find the "rarest" piece or rank pieces by
       rarity. Rather, we use a more efficient compromise and try to find
       the set of pieces that have "trade value" (another peer needs
       them) and make a random choice from that set. Here is the current
       preference order used in each mode:
       Trade Value is defined as:
         1. Piece that only this peer has (not considering other
            seeders), that a peer in which we're interested needs.
         2. Piece that not every peer in which we're interested has.
         3. Piece that only this peer has (not considering other
            seeders).
         4. Piece that not every peer has.
       Normal Mode
         1. Piece we tried to get from another peer but stopped due to
            choking or lost connection. (We have part of the piece
            already.)
         2. Piece most recently acquired by the peer (possibly/probably
            rare).
         3. Piece with trade value.
         4. Any piece not yet requested.
       Initial-piece Mode
         1. Piece with trade value which is already in progress.
         2. Piece with trade value that more than one peer has.
         3. Piece with trade value.
         4. Any piece not yet requested.
       Endgame Mode
         1. Piece with trade value which is already in progress, of which
            we have the least amount.
         2. Piece already in progress of which we have the least amount.
     * Advanced request queueing system.
          + Instead of requesting all of the slices for a piece at one
            time, we now measure latency to the peer and send requests
            based on how long it takes the data to arrive. This avoids
            wasting upload banwidth by having too many outstanding
            requests: If we get choked or lose the connection, the extra
            requests were wasted; in initial or endgame modes, more
            requests would have to be cancelled when we completed the
            piece.
          + A new piece will be queued for download when there is space
            in the queue and we've requested the slices that have been
            queued already. We also don't wait for the current piece to
            complete before sending requests for a new piece. This helps
            to maintain a continuous flow of data in the download
            pipeline.
          + When duplicating a request in initial or endgame mode, slices
            that have already been requested are queued last.
     * Don't send HAVE messages to seeders (to save UL bandwidth).
          + Since we maintain interested state, and know the peer is a
            seeder, we'll do the right thing when we become a seeder.
          + Not sending HAVE to all peers (leechers) that already have
            the piece is a bad idea IMO. If everyone takes the same
            attitude, none of us will know when another becomes a seeder
            and connections will remain open/occupied.
          + We do send a HAVE to seeders upon completing our first piece
            so that we don't continue to appear empty.
     * Endgame strategy is used in get1file mode to complete the file.
     * Queue management:
          + Don't accept requests from choked peers.
          + Discard peer's reponse_q when we choke them.
          + Don't send cancels when we get choked (according to spec &
            discussions).
          + Don't put full piece queues in pending.
          + Move closing peer's request queue to pending instead of
            discarding it.
     * Prefer uploading to or downloading from a peer after we skip them
       due to bandwidth limiting. This is done via the g_next_up and
       g_defer_up global variables in peer.cpp (for UL; s/up/dn for the
       DL versions). The peerlist Sort() function and peer "click"
       variables have been removed since they are not needed with this
       feature.

   Options & Features
     * The -c option now reports file completion status.
          + As a side effect the metainfo details are printed twice. This
            allows you to view the torrent contents while pieces are
            being verified.
          + Total percentage completion is also added to the output.
     * "-E" option to seed to a specified UL:DL ratio. Seeding will stop
       when this ratio or the timeout (-e) is reached. If CTorrent starts
       as a seeder, the ratio is interpreted as UL:[torrent size].
     * If "-e 0" is specified (explicitly) and -E is used, there will be
       no timeout; seeding will continue until the ratio is reached.
     * The "-m" option previously didn't do anything, and it isn't clear
       what it was originally going to do. Now the default value is 1,
       and CTorrent will try to maintain at least this many peers by
       contacting the tracker early if the peer count falls below this
       value. This feature was present in release dnh1 but the value was
       not changeable.
       Actually it seems likely that this was to be number of peers that
       the client would try to obtain (by initiating connections), as the
       "official" client does; this is mentioned as a note in the online
       specification. I don't really see the value in that though. That
       said, the option as implemented here should rarely be used. It
       might be useful only with torrents that have significantly more
       than max_peers total peers and use a long tracker update interval
       (such that you tend to drop a lot of peers betwen updates).
     * "-z" option to set the slice size (the unit of a request, i.e. the
       discrete amount of data that will be requested from a peer at one
       time). The slice size now defaults to 16K regardless of the piece
       length. Request queue size is computed and set based on the slice
       size, as it now affects only system resources (though not a lot)
       and not the way that requests are sent.
     * Add support for "key" and "trackerid" tracker interaction
       parameters.
     * Support/display tracker warning message
     * Now able to handle torrents with more than 255 files.
     * Support for [1]CTorrent Control Server, an application and
       protocol for monitoring and managing multiple Enhanced CTorrent
       clients. The "-S" option is used to connect to CTCS, as in "-S
       localhost:2780" if CTCS is listening at port 2780 on the local
       system. Appending a colon ("-S localhost:2780:") will prompt for a
       password to authenticate with CTCS.

   Peer Handling
     * Count immediate choke-unchoke (either order) as an error (two
       errors actually, since it's so wasteful).
       It may be that some clients do this to stimulate the peer when
       they think it hasn't responded to their last unchoke (due to high
       latency). It would be better for them to just repeat the unchoke
       rather than choke-unchoke, as by choking they will cause the peer
       to send the requests again.
     * Detect unresponsive peer connections and try to fix them or
       disconnect them. Basically, if a peer doesn't respond to our
       request in a reasonable time then we first assume that our request
       was lost in transmission; if it happens again then we assume the
       connection is unreliable.
     * Handle peers that suppress HAVE messages so we don't always think
       that they're empty (and thus give them preferential treatment for
       uploading). If we've sent the peer an amount of data equivalent to
       two pieces, assume that they now have at least one complete piece.
     _________________________________________________________________

   Changes for "dnh1.2" Release

   These are just corrections to the previous release that I felt were
   necessary. Much more improvement is coming in the dnh2 release.

   Bug/code fixes
     * Bitfield::Invert patch [1357832 on sourceforge] described below.
     * Fixed "piece length too long" check to reflect the actual queue
       length used.
     * Accept 128K slice size for peer requests.
     * "Return" keyword in Random_init() removed due to potential compile
       error.