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113 lines
3.3 KiB
C
113 lines
3.3 KiB
C
/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
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It is considered beerware. Prost. Skol. Cheers or whatever.
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$id$ */
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#ifndef __OT_LIVESYNC_H__
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#define __OT_LIVESYNC_H__
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#include "io.h"
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#include "trackerlogic.h"
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/*
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Syncing is done as udp packets in the multicast domain 224.0.42.5 port 9696
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Each tracker should join the multicast group and send its live sync packets
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to that group, using a ttl of 1
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Format of all sync packets is straight forward, packet type determines
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which kind of packet this is:
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0x0000 0x04 id of tracker instance
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0x0004 0x04 packet type
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########
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######## PEER SYNC PROTOCOL ########
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########
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Each tracker instance accumulates announce requests until its buffer is
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full or a timeout is reached. Then it broadcasts its live sync packer:
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packet type SYNC_LIVE
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[ 0x0008 0x14 info_hash
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0x001c 0x04 peer's ipv4 address
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0x0020 0x02 peer's port
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0x0024 0x02 peer flags v1 ( SEEDING = 0x80, COMPLETE = 0x40, STOPPED = 0x20 )
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]*
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########
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######## SCRAPE SYNC PROTOCOL ########
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########
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Each tracker instance SHOULD broadcast a beacon once in every 5 minutes after
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running at least 30 minutes:
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packet type SYNC_SCRAPE_BEACON
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[ 0x0008 0x08 amount of torrents served
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]
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If a tracker instance receives a beacon from another instance that has more than
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twice its torrent count, it asks for a scrape. It must wait for at least 5 + 1
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minutes in order to inspect beacons from all tracker instances and chose the one
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with most torrents.
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If it sees a SYNC_SCRAPE_TELL within that time frame, it's likely, that another
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scrape sync is going on. So one tracker instance MUST NOT react to beacons within
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5 minutes of last seeing a SYNC_SCRAPE_TELL packet. After a scrape sync all
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tracker instances have updated their torrents, so an instance in a "want inquire"
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state should wait for the next round of beacons to chose the tracker with most
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data again.
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packet type SYNC_SCRAPE_INQUIRE
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[ 0x0008 0x04 id of tracker instance to inquire
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]
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The inquired tracker instance answers with as many scrape tell packets it needs
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to deliver stats about all its torrents
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packet type SYNC_SCRAPE_TELL
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[ 0x0008 0x14 info_hash
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0x001c 0x04 base offset (i.e. when was it last announced, in minutes)
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0x0020 0x08 downloaded count
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]*
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Each tracker instance that receives a scrape tell, looks up each torrent and
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compares downloaded count with its own counter. It can send out its own scrape
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tell packets, if it knows more.
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*/
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#ifdef WANT_SYNC_LIVE
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#define LIVESYNC_PORT 9696
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void livesync_init();
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void livesync_deinit();
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/* Join multicast group for listening and create sending socket */
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void livesync_bind_mcast( char *ip, uint16_t port );
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/* Inform live sync about whats going on. */
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void livesync_tell( ot_hash * const info_hash, const ot_peer * const peer );
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/* Tickle the live sync module from time to time, so no events get
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stuck when there's not enough traffic to fill udp packets fast
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enough */
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void livesync_ticker( );
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/* Handle an incoming live sync packet */
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void handle_livesync( const int64 serversocket );
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#else
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/* If no syncing is required, save calling code from #ifdef
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constructions */
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#define livesync_deinit()
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#define livesync_init()
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#define livesync_ticker()
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#define handle_livesync(a)
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#endif
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#endif
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