1 files changed, 267 insertions, 0 deletions

diff --git a/src/ot_livesync.c b/src/ot_livesync.c
new file mode 100644
index 0000000..85577f7
--- /dev/null
+++ b/src/ot_livesync.c
@@ -0,0 +1,267 @@
+/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
+ It is considered beerware. Prost. Skol. Cheers or whatever. */
+
+/* System */
+#include <arpa/inet.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+/* Opentracker */
+#include "ot_accesslist.h"
+#include "ot_ip.h"
+#include "ot_socket.h"
+#include "ot_livesync.h"
+#include "ot_mutex.h"
+#include "ot_stats.h"
+#include "trackerlogic.h"
+
+#ifdef WANT_SYNC_LIVE
+
+/* The multicast group, legacy opentrackers joined by default 224.0.23.5, so it
+   stays the default */
+static ot_ip6   g_group = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, 224, 0, 23, 5};
+static uint16_t g_port  = LIVESYNC_PORT;
+
+#define LIVESYNC_INCOMING_BUFFSIZE        (256 * 256)
+
+#define LIVESYNC_OUTGOING_BUFFSIZE_PEERS  1480
+#define LIVESYNC_OUTGOING_WATERMARK_PEERS (sizeof(ot_peer) + sizeof(ot_hash))
+
+#define LIVESYNC_MAXDELAY                 15 /* seconds */
+
+enum { OT_SYNC_PEER4, OT_SYNC_PEER6 };
+
+/* Forward declaration */
+static void           *livesync_worker(void *args);
+
+/* For incoming packets */
+static int             g_socket_in    = -1;
+
+/* For outgoing packets */
+static int             g_socket_out   = -1;
+
+static pthread_mutex_t g_outbuf_mutex = PTHREAD_MUTEX_INITIALIZER;
+typedef struct {
+  uint8_t data[LIVESYNC_OUTGOING_BUFFSIZE_PEERS];
+  size_t  fill;
+  ot_time next_packet_time;
+} sync_buffer;
+
+static sync_buffer g_v6_buf;
+static sync_buffer g_v4_buf;
+
+static pthread_t   thread_id;
+static int         thread_started;
+static _Atomic int thread_left;
+void livesync_init(void) {
+  uint32_t packet_type6 = htonl(OT_SYNC_PEER6);
+  uint32_t packet_type4 = htonl(OT_SYNC_PEER4);
+
+  if (g_socket_in == -1)
+    return;
+
+  /* Prepare outgoing peers buffer */
+  memcpy(g_v6_buf.data, &g_tracker_id, sizeof(g_tracker_id));
+  memcpy(g_v4_buf.data, &g_tracker_id, sizeof(g_tracker_id));
+
+  memcpy(g_v6_buf.data + sizeof(g_tracker_id), &packet_type6, sizeof(packet_type6));
+  memcpy(g_v4_buf.data + sizeof(g_tracker_id), &packet_type4, sizeof(packet_type4));
+
+  g_v6_buf.fill             = sizeof(g_tracker_id) + sizeof(uint32_t);
+  g_v4_buf.fill             = sizeof(g_tracker_id) + sizeof(uint32_t);
+
+  g_v6_buf.next_packet_time = time_future_seconds(LIVESYNC_MAXDELAY);
+  g_v4_buf.next_packet_time = time_future_seconds(LIVESYNC_MAXDELAY);
+
+  thread_started = !pthread_create(&thread_id, NULL, livesync_worker, NULL);
+}
+
+void livesync_deinit(void) {
+  if (thread_started) {
+    /* Repeats so it interrupts a read already under way */
+    while (!atomic_load(&thread_left)) {
+      pthread_kill(thread_id, OT_SIGNAL_WAKE);
+      usleep(1000);
+    }
+    pthread_join(thread_id, NULL);
+    thread_started = 0;
+  }
+
+  if (g_socket_in != -1)
+    close(g_socket_in);
+  if (g_socket_out != -1)
+    close(g_socket_out);
+}
+
+int livesync_set_group(const ot_ip6 group) {
+  /* v4 multicast is 224.0.0.0/4, and the socket layer has nothing else */
+  if (!ip_is_v4mapped(group) || (group[12] & 0xf0) != 0xe0)
+    return -1;
+  memcpy(g_group, group, sizeof(ot_ip6));
+  return 0;
+}
+
+void livesync_bind_mcast(ot_ip6 ip, uint16_t port) {
+  if (!ip_is_v4mapped(ip))
+    exerr("v6 mcast support not yet available.");
+
+  if (g_socket_in != -1)
+    exerr("Error: Livesync listen ip specified twice.");
+
+  g_port = port;
+
+  if ((g_socket_in = socket_mcast_join(g_group, ip, port)) == -1)
+    exerr("Error: Cant bind live sync incoming socket.");
+
+  if ((g_socket_out = socket_mcast_bind(ip, port, 0)) == -1)
+    exerr("Error: Cant bind live sync outgoing socket.");
+}
+
+/* Caller MUST hold g_outbuf_mutex. Returns with g_outbuf_mutex unlocked */
+static void livesync_issue_peersync(sync_buffer *buf) {
+  char   mycopy[LIVESYNC_OUTGOING_BUFFSIZE_PEERS];
+  size_t fill = buf->fill;
+
+  memcpy(mycopy, buf->data, fill);
+  buf->fill             = sizeof(g_tracker_id) + sizeof(uint32_t);
+  buf->next_packet_time = time_future_seconds(LIVESYNC_MAXDELAY);
+
+  /* From now this thread has a local copy of the buffer and
+     has modified the protected element */
+  pthread_mutex_unlock(&g_outbuf_mutex);
+
+  socket_mcast_send(g_socket_out, mycopy, fill, g_group, g_port);
+}
+
+static void livesync_handle_peersync(struct ot_workstruct *ws, size_t peer_size) {
+  size_t off = sizeof(g_tracker_id) + sizeof(uint32_t);
+
+  /* Prepare peer record for v4mapped expansion */
+  if (peer_size == OT_PEER_SIZE4)
+    memcpy(&ws->peer, ip_v4mapped_prefix, sizeof(ip_v4mapped_prefix));
+
+  /* Now basic sanity checks have been done on the live sync packet
+     We might add more testing and logging. */
+  while ((ssize_t)(off + sizeof(ot_hash) + peer_size) <= ws->request_size) {
+    char *peer_ip = ws->request + off + sizeof(ot_hash);
+    if (peer_size == OT_PEER_SIZE4)
+        memcpy(&ws->peer[0] + sizeof(ip_v4mapped_prefix), peer_ip, peer_size);
+    else
+        memcpy(&ws->peer, peer_ip, peer_size);
+    ws->hash = (ot_hash *)(ws->request + off);
+
+    if (!g_opentracker_running)
+      return;
+
+    if (OT_PEERFLAG(ws->peer) & PEER_FLAG_STOPPED)
+      remove_peer_from_torrent(FLAG_MCA, ws);
+    else
+      add_peer_to_torrent_and_return_peers(FLAG_MCA, ws, /* amount = */ 0);
+
+    off += sizeof(ot_hash) + peer_size;
+  }
+
+  stats_issue_event(ws, EVENT_SYNC, 0, (ws->request_size - sizeof(g_tracker_id) - sizeof(uint32_t)) / ((ssize_t)sizeof(ot_hash) + peer_size));
+}
+
+/* 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(void) {
+  if (g_socket_out == -1)
+    return;
+
+  /* livesync_issue_peersync sets g_next_packet_time */
+  pthread_mutex_lock(&g_outbuf_mutex);
+  if (time_now_seconds() > g_v6_buf.next_packet_time && g_v6_buf.fill > sizeof(g_tracker_id) + sizeof(uint32_t))
+    livesync_issue_peersync(&g_v6_buf);
+  else
+    pthread_mutex_unlock(&g_outbuf_mutex);
+
+  pthread_mutex_lock(&g_outbuf_mutex);
+  if (time_now_seconds() > g_v4_buf.next_packet_time && g_v4_buf.fill > sizeof(g_tracker_id) + sizeof(uint32_t))
+    livesync_issue_peersync(&g_v4_buf);
+  else
+    pthread_mutex_unlock(&g_outbuf_mutex);
+}
+
+/* Inform live sync about whats going on. */
+void livesync_tell(struct ot_workstruct *ws) {
+  size_t       peer_size; /* initialized in next line */
+  ot_peer     *peer_src;
+  sync_buffer *dest_buf;
+
+  if (g_socket_out == -1)
+    return;
+
+  peer_src = peer_from_peer6(&ws->peer, &peer_size);
+  dest_buf = peer_size == OT_PEER_SIZE6 ? &g_v6_buf : &g_v4_buf;
+
+  pthread_mutex_lock(&g_outbuf_mutex);
+
+  memcpy(dest_buf->data + dest_buf->fill, ws->hash, sizeof(ot_hash));
+  dest_buf->fill += sizeof(ot_hash);
+
+  memcpy(dest_buf->data + dest_buf->fill, peer_src, peer_size);
+  dest_buf->fill += peer_size;
+
+  if (dest_buf->fill >= LIVESYNC_OUTGOING_BUFFSIZE_PEERS - LIVESYNC_OUTGOING_WATERMARK_PEERS)
+    livesync_issue_peersync(dest_buf);
+  else
+    pthread_mutex_unlock(&g_outbuf_mutex);
+}
+
+static void *livesync_worker(void *args) {
+  struct ot_workstruct ws;
+  ot_ip6               in_ip;
+  uint16_t             in_port;
+
+  (void)args;
+
+  if (workstruct_init(&ws, LIVESYNC_INCOMING_BUFFSIZE) == -1) {
+    fprintf(stderr, "Warning: live sync could not get its buffers and will not run.\n");
+    atomic_store(&thread_left, 1);
+    return NULL;
+  }
+  ws.request = ws.inbuf;
+
+  while (g_opentracker_running) {
+    uint32_t packet_type;
+
+    ws.request_size = socket_recv(g_socket_in, ws.inbuf, LIVESYNC_INCOMING_BUFFSIZE, in_ip, &in_port);
+
+    /* Expect at least tracker id and packet type */
+    if (ws.request_size <= (ssize_t)(sizeof(g_tracker_id) + sizeof(uint32_t)))
+      continue;
+    if (!accesslist_is_blessed(in_ip, OT_PERMISSION_MAY_LIVESYNC))
+      continue;
+    if (!memcmp(ws.inbuf, &g_tracker_id, sizeof(g_tracker_id))) {
+      /* TODO: log packet coming from ourselves */
+      continue;
+    }
+
+    memcpy(&packet_type, ws.inbuf + sizeof(g_tracker_id), sizeof(packet_type));
+
+    switch (ntohl(packet_type)) {
+    case OT_SYNC_PEER6:
+      livesync_handle_peersync(&ws, OT_PEER_SIZE6);
+      break;
+    case OT_SYNC_PEER4:
+      livesync_handle_peersync(&ws, OT_PEER_SIZE4);
+      break;
+    default:
+      break;
+    }
+  }
+
+  workstruct_deinit(&ws);
+  atomic_store(&thread_left, 1);
+  return NULL;
+}
+
+#endif