1 files changed, 273 insertions, 0 deletions

diff --git a/trackerlogic.c b/trackerlogic.c
new file mode 100644
index 0000000..d21fc01
--- /dev/null
+++ b/trackerlogic.c
@@ -0,0 +1,273 @@
+// THIS REALLY BELONGS INTO A HEADER FILE
+//
+//
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+
+typedef unsigned char ot_hash[20];
+typedef unsigned char ot_ip[ 4/*0*/ ];
+typedef unsigned long ot_time;
+// tunables
+const unsigned long OT_TIMEOUT          = 2700;
+const unsigned long OT_HUGE_FILESIZE    = 1024*1024*256; // Thats 256MB per file, enough for 204800 peers of 128 bytes
+
+#define OT_COMPACT_ONLY
+
+#define MEMMOVE              memmove
+#define BZERO                bzero
+#define FORMAT_FIXED_STRING  sprintf
+#define FORMAT_FORMAT_STRING sprintf
+#define BINARY_FIND          binary_search
+
+typedef struct {
+#ifndef OT_COMPACT_ONLY
+  ot_hash         id;
+  ot_hash         key;
+#endif
+  ot_ip           ip;
+  unsigned short  port;
+  ot_time         death;
+  unsigned char   flags;
+} ot_peer;
+unsigned char PEER_FLAG_SEEDING   = 0x80;
+unsigned char PEER_IP_LENGTH_MASK = 0x3f;
+
+typedef struct {
+  ot_hash         hash;
+  ot_peer        *peer_list;
+  unsigned long   peer_count;
+  unsigned long   seed_count;
+} ot_torrent;
+
+void *map_file( char *file_name );
+
+// This behaves quite like bsearch but allows to find
+// the insertion point for inserts after unsuccessful searches
+// in this case exactmatch is 0 on exit
+//
+void *binary_search( const void *key, const void *base,
+                     const unsigned long member_count, const unsigned long member_size,
+                     int (*compar) (const void *, const void *),
+                     int *exactmatch );
+
+int compare_hash( const void *hash1, const void *hash2 ) { return memcmp( hash1, hash2, sizeof( ot_hash )); }
+int compare_ip_port( const void *peer1, const void *peer2 ) { return memcmp( peer1, peer2, 6); }
+
+//
+//
+// END OF STUFF THAT BELONGS INTO A HEADER FILE
+
+ot_torrent *torrents_pointer = 0;
+unsigned long torrents_count = 0;
+unsigned char *scratchspace;
+
+ot_torrent *add_peer_to_torrent( ot_hash hash, ot_peer *peer ) {
+  ot_torrent *torrent;
+  ot_peer    *peer_dest;
+  int exactmatch;
+
+  torrent = BINARY_FIND( hash, torrents_pointer, torrents_count, sizeof( ot_torrent ), compare_hash, &exactmatch );
+  if( !exactmatch ) {
+    // Assume, OS will provide us with space, after all, this is file backed
+    MEMMOVE( torrent + 1, torrent, ( torrents_pointer + torrents_count ) - torrent );
+
+    // Create a new torrent entry, then
+    MEMMOVE( &torrent->hash, hash, sizeof( ot_hash ) );
+    torrent->peer_list  = map_file( hash );
+    torrent->peer_count = 0;
+    torrent->seed_count = 0;
+  }
+
+  peer_dest = BINARY_FIND( peer, torrent->peer_list, torrent->peer_count, sizeof( ot_peer ), compare_ip_port, &exactmatch );
+  if( exactmatch ) {
+    // If peer was a seeder but isn't anymore, decrease seeder count
+    if( ( peer_dest->flags & PEER_FLAG_SEEDING ) && !( peer->flags & PEER_FLAG_SEEDING ) )
+      torrent->seed_count--;
+    if( !( peer_dest->flags & PEER_FLAG_SEEDING ) && ( peer->flags & PEER_FLAG_SEEDING ) )
+      torrent->seed_count++;
+  } else {
+    // Assume, OS will provide us with space, after all, this is file backed
+    MEMMOVE( peer_dest + 1, peer_dest, ( torrent->peer_list + torrent->peer_count ) - peer_dest );
+
+    // Create a new peer entry, then
+    MEMMOVE( peer_dest, peer, sizeof( ot_peer ) );
+
+    torrent->peer_count++;
+    torrent->seed_count+= ( peer->flags & PEER_FLAG_SEEDING ) ? 1 : 0;
+  }
+
+  // Set new time out time
+  peer_dest->death = now() + OT_TIMEOUT;
+
+  return torrent;
+}
+
+#define SETINVALID( i )   (scratchspace[index] = 3);
+#define SETSELECTED( i )  (scratchspace[index] = 1);
+#define TESTSELECTED( i ) (scratchspace[index] == 1 )
+#define TESTSET( i )      (scratchspace[index])
+#define RANDOM            random()
+
+inline int TESTVALIDPEER( ot_peer *p ) { return p->death > now(); }
+
+// Compiles a list of random peers for a torrent
+// * scratch space keeps track of death or already selected peers
+// * reply must have enough space to hold 1+(1+16+2+1)*amount+1 bytes
+// * Selector function can be anything, maybe test for seeds, etc.
+// * that RANDOM may return huge values
+// * does not yet check not to return self
+// * it is not guaranteed to see all peers, so no assumptions on active seeders/peers may be done
+// * since compact format cannot handle v6 addresses, it must be enabled by OT_COMPACT_ONLY
+//
+void return_peers_for_torrent( ot_torrent *torrent, unsigned long amount, char *reply ) {
+  register ot_peer *peer_base = torrent->peer_list;
+  unsigned long     peer_count = torrent->peer_count;
+  unsigned long     selected_count = 0, invalid_count = 0;
+  unsigned long     index = 0;
+
+  // optimize later ;)
+  BZERO( scratchspace, peer_count );
+
+  while( ( selected_count < amount ) && ( selected_count + invalid_count < peer_count ) ) {
+    // skip to first non-flagged peer
+    while( TESTSET(index) ) index = ( index + 1 ) % peer_count;
+
+    if( TESTVALIDPEER( peer_base + index ) ) {
+      SETINVALID(index); invalid_count++;
+    } else {
+      SETSELECTED(index); selected_count++;
+      index = ( index + RANDOM ) % peer_count;
+    }
+  }
+
+  // Now our scratchspace contains a list of selected_count valid peers
+  // Collect them into a reply string
+  index = 0;
+
+#ifndef OT_COMPACT_ONLY
+  reply += FORMAT_FIXED_STRING( reply, "d5:peersl" );
+#else
+  reply += FORMAT_FORMAT_STRING( reply, "d5:peers%i:",6*selected_count );
+#endif
+
+  while( selected_count-- ) {
+    ot_peer *peer;
+    while( !TESTSELECTED( index ) ) ++index;
+    peer = peer_base + index;
+#ifdef OT_COMPACT_ONLY
+    MEMMOVE( reply, &peer->ip, 4 );
+    MEMMOVE( reply+4, &peer->port, 2 );
+    reply += 6;
+#else
+    reply += FORMAT_FORMAT_STRING( reply, "d2:ip%d:%s7:peer id20:%20c4:porti%ie",
+      peer->flags & PEER_IP_LENGTH_MASK,
+      peer->ip,
+      peer->id,
+      peer->port );
+#endif
+  }
+#ifndef OT_COMPACT_ONLY
+  reply += FORMAT_FIXED_STRING( reply, "ee" );
+#else
+  reply += FORMAT_FIXED_STRING( reply, "e" );
+#endif
+}
+
+// Compacts a torrents peer list
+// * torrents older than OT_TIMEOUT are being kicked
+// * is rather expansive
+// * if this fails, torrent file is invalid, should add flag
+//
+void heal_torrent( ot_torrent *torrent ) {
+  unsigned long index = 0, base = 0, end, seed_count = 0;
+
+  // Initialize base to first dead peer.
+  while( ( base < torrent->peer_count ) && torrent->peer_list[base].death <= now() ) {
+    seed_count += ( torrent->peer_list[base].flags & PEER_FLAG_SEEDING ) ? 1 : 0;
+    base++;
+  }
+
+  // No dead peers? Home.
+  if( base == torrent->peer_count ) return;
+
+  // From now index always looks to the next living peer while base keeps track of
+  // the dead peer that marks the beginning of insert space.
+  index = base + 1;
+
+  while( 1 ) {
+    // Let index search for next living peer
+    while( ( index < torrent->peer_count ) && torrent->peer_list[index].death > now() ) index++;
+
+    // No further living peers found - base is our new peer count
+    if( index == torrent->peer_count ) {
+      torrent->peer_count = base;
+      torrent->seed_count = seed_count;
+      return;
+    }
+
+    end = index + 1;
+
+    // Let end search for next dead peer (end of living peers)
+    while( ( end < torrent->peer_count ) && torrent->peer_list[end].death <= now() ) {
+      seed_count += ( torrent->peer_list[end].flags & PEER_FLAG_SEEDING ) ? 1 : 0;
+      end++;
+    }
+
+    // We either hit a dead peer or the end of our peers
+    // In both cases: move block towards base
+    MEMMOVE( torrent->peer_list + base, torrent->peer_list + index, ( end - index ) * sizeof( ot_peer ) );
+    base += end - index;
+
+    index = end;
+  }
+}
+
+void *binary_search( const void *key, const void *base,
+                     unsigned long member_count, const unsigned long member_size,
+                     int (*compar) (const void *, const void *),
+                     int *exactmatch ) {
+  unsigned char *lookat = ((unsigned char*)base) + member_size * (member_count >> 1);
+  *exactmatch = 1;
+
+  while( member_count ) {
+    int cmp = compar((void*)lookat, key);
+    if (cmp == 0) return (void *)lookat;
+    if (cmp < 0) {
+      base = (void*)(lookat + member_size);
+      --member_count;
+    }
+    member_count >>= 1;
+    lookat = ((unsigned char*)base) + member_size * (member_count >> 1);
+  }
+  *exactmatch = 0;
+  return (void*)lookat;
+
+}
+
+// This function maps a "huge" file into process space
+// * I guess, we should be checking for more errors...
+void *map_file( char *file_name ) {
+  char *map;
+  int file_desc=open(file_name,O_RDWR|O_CREAT|O_NDELAY,0644);
+
+  if( file_desc < 0) return 0;
+
+  map=mmap(0,OT_HUGE_FILESIZE,PROT_READ|PROT_WRITE,MAP_SHARED,file_desc,0);
+  close(file_desc);
+
+  return (map == (char*)-1) ? 0 : map;
+}
+
+int init_logic( ) {
+  unlink( "./opentracker_map_index.idx" );
+  torrents_pointer = map_file( "./opentracker_map_index.idx" );
+  torrents_count   = 0;
+  scratchspace     = map_file( "./scratchspace" );
+}
+
+void deinit_logic( ) {
+  unmap_file( torrents_pointer );
+}