Live syncing between multiple tracker instances via udp multicast.

ot_livesync.c

@@ -0,0 +1,122 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+ It is considered beerware. Prost. Skol. Cheers or whatever.
+ 
+ $id$ */
+
+/* System */
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <string.h>
+
+/* Libowfat */
+#include "socket.h"
+
+/* Opentracker */
+#include "trackerlogic.h"
+#include "ot_livesync.h"
+#include "ot_accesslist.h"
+
+#ifdef WANT_SYNC_LIVE
+char groupip_1[4] = { LIVESYNC_MCASTDOMAIN_1 };
+
+/* For outgoing packets */
+int64 g_livesync_socket = -1;
+
+static uint8_t  livesync_inbuffer[LIVESYNC_BUFFINSIZE];
+static uint8_t  livesync_outbuffer_start[ LIVESYNC_BUFFSIZE ];
+static uint8_t *livesync_outbuffer_pos;
+static uint8_t *livesync_outbuffer_highwater = livesync_outbuffer_start + LIVESYNC_BUFFSIZE - LIVESYNC_BUFFWATER;
+static ot_time  livesync_lastpacket_time;
+
+void livesync_init( ) {
+  if( g_livesync_socket == -1 )
+    exerr( "No socket address for live sync specified." );
+  livesync_outbuffer_pos = livesync_outbuffer_start;
+  memmove( livesync_outbuffer_pos, &g_tracker_id, sizeof( g_tracker_id ) );
+  livesync_outbuffer_pos += sizeof( g_tracker_id );
+  livesync_lastpacket_time = g_now;
+}
+	
+void livesync_deinit() {
+	
+}
+
+void livesync_bind_mcast( char *ip, uint16_t port) {
+  char tmpip[4] = {0,0,0,0};
+  if( g_livesync_socket != -1 )
+    exerr("Livesync listen ip specified twice.");
+  if( socket_mcjoin4( ot_try_bind(tmpip, port, FLAG_MCA ), groupip_1, ip ) )
+    exerr("Cant join mcast group.");
+  g_livesync_socket = ot_try_bind( ip, port, FLAG_UDP );
+  io_dontwantread(g_livesync_socket);
+
+  socket_mcttl4(g_livesync_socket, 1);
+  socket_mcloop4(g_livesync_socket, 0);
+}
+
+static void livesync_issuepacket( ) {
+	socket_send4(g_livesync_socket, (char*)livesync_outbuffer_start, livesync_outbuffer_pos - livesync_outbuffer_start,
+               groupip_1, LIVESYNC_PORT);
+  livesync_outbuffer_pos = livesync_outbuffer_start + sizeof( g_tracker_id );
+  livesync_lastpacket_time = g_now;
+}
+
+/* Inform live sync about whats going on. */
+void livesync_tell( ot_hash * const info_hash, const ot_peer * const peer, const uint8_t peerflag ) {
+  memmove( livesync_outbuffer_pos                  , info_hash, sizeof(ot_hash));
+  memmove( livesync_outbuffer_pos + sizeof(ot_hash), peer,      sizeof(ot_peer));
+  OT_FLAG( livesync_outbuffer_pos + sizeof(ot_hash) ) |= peerflag;
+
+  livesync_outbuffer_pos += sizeof(ot_hash) + sizeof(ot_peer);
+  if( livesync_outbuffer_pos >= livesync_outbuffer_highwater )
+    livesync_issuepacket();
+}
+
+/* Tickle the live sync module from time to time, so no events get
+ stuck when there's not enough traffic to fill udp packets fast
+ enough */
+void livesync_ticker( ) {
+	if( ( g_now - livesync_lastpacket_time > LIVESYNC_MAXDELAY) &&
+      ( livesync_outbuffer_pos > livesync_outbuffer_start + sizeof( g_tracker_id ) ) )
+    livesync_issuepacket();
+}
+
+/* Handle an incoming live sync packet */
+void handle_livesync( int64 serversocket ) {
+  uint8_t in_ip[4]; uint16_t in_port;
+  ssize_t datalen = socket_recv4(serversocket, (char*)livesync_inbuffer, LIVESYNC_BUFFINSIZE, (char*)in_ip, &in_port);
+  int off = 4;
+
+  if( datalen < (ssize_t)(sizeof( g_tracker_id ) + sizeof( ot_hash ) + sizeof( ot_peer ) ) ) {
+    // TODO: log invalid sync packet
+    return;
+  }
+
+  if( !accesslist_isblessed((char*)in_ip, OT_PERMISSION_MAY_LIVESYNC)) {
+    // TODO: log invalid sync packet
+    return;
+  }
+
+  if( !memcmp( livesync_inbuffer, &g_tracker_id, sizeof( g_tracker_id ) ) ) {
+    // TODO: log packet coming from ourselves
+    return;
+  }
+
+  // Now basic sanity checks have been done on the live sync packet
+  // We might add more testing and logging.
+  while( off + (ssize_t)sizeof( ot_hash ) + (ssize_t)sizeof( ot_peer ) <= datalen ) {
+    ot_peer *peer = (ot_peer*)(livesync_inbuffer + off + sizeof(ot_hash));
+    ot_hash *hash = (ot_hash*)(livesync_inbuffer + off);
+
+    if( OT_FLAG(peer) & PEER_FLAG_STOPPED )
+      remove_peer_from_torrent(hash, peer, NULL, FLAG_MCA);
+    else
+      add_peer_to_torrent( hash, peer  WANT_SYNC_PARAM(1));
+
+    off += sizeof( ot_hash ) + sizeof( ot_peer );
+  }
+  
+}
+
+#endif
+const char *g_version_livesync_c = "$Source$: $Revision$\n";

ot_livesync.h

@@ -0,0 +1,85 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+ It is considered beerware. Prost. Skol. Cheers or whatever.
+ 
+ $id$ */
+
+#ifndef __OT_LIVESYNC_H__
+#define __OT_LIVESYNC_H__
+
+#include "io.h"
+#include "trackerlogic.h"
+
+/*
+  Syncing is done as udp packets in the multicast domain 224.23.42.N port 9696
+
+  Each tracker should join the multicast group and send its live sync packets
+  to that group, using a ttl of 1
+
+  Format of a live sync packet is straight forward and depends on N:
+
+  For N == 1: (simple tracker2tracker sync)
+    0x0000 0x04 id of tracker instance
+  [ 0x0004 0x14 info_hash
+    0x0018 0x04 peer's ipv4 address
+    0x001c 0x02 peer's port
+    0x0020 0x02 peer flags v1 ( SEEDING = 0x80, COMPLETE = 0x40, STOPPED = 0x20 )
+  ]*
+ 
+  For N == 2: (aggregator syncs)
+    0x0000 0x04 id of tracker instance
+  [ 0x0004 0x14 info_hash
+    0x0018 0x01 number of peers
+    [ 0x0019 0x04 peer's ipv4 address
+      0x001a 0x02 peer's port
+      0x0021 0x02 peer flags v1 ( SEEDING = 0x80, COMPLETE = 0x40, STOPPED = 0x20 )
+    ]+
+  ]*
+ 
+
+ */
+
+#ifdef WANT_SYNC_LIVE
+
+#define LIVESYNC_PORT 9696
+#define LIVESYNC_MCASTDOMAIN_1 224,23,42,1
+#define LIVESYNC_MCASTDOMAIN_2 224,23,42,2
+extern char groupip_1[4];
+extern char groupip_2[4];
+
+extern int64 g_livesync_socket;
+
+#define LIVESYNC_BUFFINSIZE (256*256)
+#define LIVESYNC_BUFFSIZE  1504
+#define LIVESYNC_BUFFWATER (sizeof(ot_peer)+sizeof(ot_hash))
+
+#define LIVESYNC_MAXDELAY  15
+
+void livesync_init();
+void livesync_deinit();
+
+/* Join multicast group for listening and create sending socket */
+void livesync_bind_mcast( char *ip, uint16_t port );
+
+/* Inform live sync about whats going on. */
+void livesync_tell( ot_hash * const info_hash, const ot_peer * const peer, const uint8_t peerflag );
+
+/* Tickle the live sync module from time to time, so no events get
+   stuck when there's not enough traffic to fill udp packets fast
+   enough */
+void livesync_ticker( );
+
+/* Handle an incoming live sync packet */
+void handle_livesync( const int64 serversocket );
+
+#else
+
+/* If no syncing is required, save calling code from #ifdef 
+   constructions */
+
+#define livesync_init()
+#define livesync_ticker()
+#define handle_livesync(a)
+
+#endif
+
+#endif