Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1328 insertions, 0 deletions

diff --git a/src/topology/gnunet-daemon-topology.c b/src/topology/gnunet-daemon-topology.c
new file mode 100644
index 0000000..38a648a
--- /dev/null
+++ b/src/topology/gnunet-daemon-topology.c
@@ -0,0 +1,1328 @@
+/*
+     This file is part of GNUnet.
+     (C) 2007, 2008, 2009, 2010 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+
+/**
+ * @file topology/gnunet-daemon-topology.c
+ * @brief code for maintaining the mesh topology
+ * @author Christian Grothoff
+ */
+
+#include <stdlib.h>
+#include "platform.h"
+#include "gnunet_constants.h"
+#include "gnunet_core_service.h"
+#include "gnunet_protocols.h"
+#include "gnunet_peerinfo_service.h"
+#include "gnunet_statistics_service.h"
+#include "gnunet_transport_service.h"
+#include "gnunet_util_lib.h"
+
+
+#define DEBUG_TOPOLOGY GNUNET_YES
+
+/**
+ * For how long do we blacklist a peer after a failed connection
+ * attempt?
+ */
+#define GREYLIST_AFTER_ATTEMPT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 15)
+
+/**
+ * For how long do we blacklist a friend after a failed connection
+ * attempt?
+ */
+#define GREYLIST_AFTER_ATTEMPT_FRIEND GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
+
+/**
+ * For how long do we blacklist anyone under any cirumstances after a failed connection
+ * attempt?
+ */
+#define GREYLIST_AFTER_ATTEMPT_MIN GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 15)
+
+/**
+ * For how long do we blacklist anyone under any cirumstances after a failed connection
+ * attempt?
+ */
+#define GREYLIST_AFTER_ATTEMPT_MAX GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 1)
+
+/**
+ * How often do we at most advertise any HELLO to a peer?
+ */
+#define HELLO_ADVERTISEMENT_MIN_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 4)
+
+/**
+ * How often do we at most advertise the same HELLO to the same peer?
+ */
+#define HELLO_ADVERTISEMENT_MIN_REPEAT_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 4)
+
+
+/**
+ * Record for neighbours, friends and blacklisted peers.
+ */
+struct Peer
+{
+  /**
+   * Which peer is this entry about?
+   */
+  struct GNUNET_PeerIdentity pid;
+
+  /**
+   * Our handle for the request to transmit HELLOs to this peer; NULL
+   * if no such request is pending.
+   */
+  struct GNUNET_CORE_TransmitHandle *hello_req;
+
+  /**
+   * Pointer to the HELLO message of this peer; can be NULL.
+   */
+  struct GNUNET_HELLO_Message *hello;
+
+  /**
+   * Bloom filter used to mark which peers already got the HELLO
+   * from this peer.
+   */
+  struct GNUNET_CONTAINER_BloomFilter *filter;
+
+  /**
+   * Until what time should we not try to connect again
+   * to this peer?
+   */
+  struct GNUNET_TIME_Absolute greylisted_until;
+
+  /**
+   * Next time we are allowed to transmit a HELLO to this peer?
+   */
+  struct GNUNET_TIME_Absolute next_hello_allowed;
+
+  /**
+   * When should we reset the bloom filter of this entry?
+   */
+  struct GNUNET_TIME_Absolute filter_expiration;
+
+  /**
+   * ID of task we use to wait for the time to send the next HELLO
+   * to this peer.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier hello_delay_task;
+
+  /**
+   * ID of task we use to clear peers from the greylist.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier greylist_clean_task;
+
+  /**
+   * How often have we tried so far?
+   */
+  unsigned int connect_attempts;
+
+  /**
+   * Is this peer listed here because he is a friend?
+   */
+  int is_friend;
+
+  /**
+   * Are we connected to this peer right now?
+   */
+  int is_connected;
+
+};
+
+
+/**
+ * Our peerinfo notification context.  We use notification
+ * to instantly learn about new peers as they are discovered.
+ */
+static struct GNUNET_PEERINFO_NotifyContext *peerinfo_notify;
+
+/**
+ * Our configuration.
+ */
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+/**
+ * Handle to the core API.
+ */
+static struct GNUNET_CORE_Handle *handle;
+
+/**
+ * Handle to the transport API.
+ */
+static struct GNUNET_TRANSPORT_Handle *transport;
+
+/**
+ * Identity of this peer.
+ */
+static struct GNUNET_PeerIdentity my_identity;
+
+/**
+ * All of our friends, all of our current neighbours and all peers for
+ * which we have HELLOs.  So pretty much everyone.  Maps peer identities
+ * to 'struct Peer *' values.
+ */
+static struct GNUNET_CONTAINER_MultiHashMap *peers;
+
+/**
+ * Handle for reporting statistics.
+ */
+static struct GNUNET_STATISTICS_Handle *stats;
+
+/**
+ * Blacklist (NULL if we have none).
+ */
+static struct GNUNET_TRANSPORT_Blacklist *blacklist;
+
+/**
+ * Task scheduled to try to add peers.
+ */
+static GNUNET_SCHEDULER_TaskIdentifier add_task;
+
+/**
+ * Flag to disallow non-friend connections (pure F2F mode).
+ */
+static int friends_only;
+
+/**
+ * Minimum number of friends to have in the
+ * connection set before we allow non-friends.
+ */
+static unsigned int minimum_friend_count;
+
+/**
+ * Number of peers (friends and others) that we are currently connected to.
+ */
+static unsigned int connection_count;
+
+/**
+ * Target number of connections.
+ */
+static unsigned int target_connection_count;
+
+/**
+ * Number of friends that we are currently connected to.
+ */
+static unsigned int friend_count;
+
+/**
+ * Should the topology daemon try to establish connections?
+ */
+static int autoconnect;
+
+
+/**
+ * Function that decides if a connection is acceptable or not.
+ * If we have a blacklist, only friends are allowed, so the check
+ * is rather simple.
+ *
+ * @param cls closure
+ * @param pid peer to approve or disapproave
+ * @return GNUNET_OK if the connection is allowed
+ */
+static int
+blacklist_check (void *cls, const struct GNUNET_PeerIdentity *pid)
+{
+  struct Peer *pos;
+
+  pos = GNUNET_CONTAINER_multihashmap_get (peers, &pid->hashPubKey);
+  if ((pos != NULL) && (pos->is_friend == GNUNET_YES))
+    return GNUNET_OK;
+  GNUNET_STATISTICS_update (stats, gettext_noop ("# peers blacklisted"), 1,
+                            GNUNET_NO);
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Whitelist all peers that we blacklisted; we've passed
+ * the minimum number of friends.
+ */
+static void
+whitelist_peers ()
+{
+  if (blacklist != NULL)
+  {
+    GNUNET_TRANSPORT_blacklist_cancel (blacklist);
+    blacklist = NULL;
+  }
+}
+
+
+/**
+ * Check if an additional connection from the given peer is allowed.
+ *
+ * @param peer connection to check
+ * @return GNUNET_OK if the connection is allowed
+ */
+static int
+is_connection_allowed (struct Peer *peer)
+{
+  if (0 ==
+      memcmp (&my_identity, &peer->pid, sizeof (struct GNUNET_PeerIdentity)))
+    return GNUNET_SYSERR;       /* disallow connections to self */
+  if (peer->is_friend)
+    return GNUNET_OK;
+  if (GNUNET_YES == friends_only)
+  {
+#if DEBUG_TOPOLOGY
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Determined that `%s' is not allowed to connect (not a friend)\n",
+                GNUNET_i2s (&peer->pid));
+#endif
+    return GNUNET_SYSERR;
+  }
+  if (friend_count >= minimum_friend_count)
+    return GNUNET_OK;
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Determined that `%s' is not allowed to connect (not enough connected friends)\n",
+              GNUNET_i2s (&peer->pid));
+#endif
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * Free all resources associated with the given peer.
+ *
+ * @param cls closure (not used)
+ * @param pid identity of the peer
+ * @param value peer to free
+ * @return GNUNET_YES (always: continue to iterate)
+ */
+static int
+free_peer (void *cls, const GNUNET_HashCode * pid, void *value)
+{
+  struct Peer *pos = value;
+
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_remove (peers, pid, pos));
+  if (pos->hello_req != NULL)
+    GNUNET_CORE_notify_transmit_ready_cancel (pos->hello_req);
+  if (pos->hello_delay_task != GNUNET_SCHEDULER_NO_TASK)
+    GNUNET_SCHEDULER_cancel (pos->hello_delay_task);
+  if (pos->greylist_clean_task != GNUNET_SCHEDULER_NO_TASK)
+    GNUNET_SCHEDULER_cancel (pos->greylist_clean_task);
+  GNUNET_free_non_null (pos->hello);
+  if (pos->filter != NULL)
+    GNUNET_CONTAINER_bloomfilter_free (pos->filter);
+  GNUNET_free (pos);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Discard peer entries for greylisted peers
+ * where the greylisting has expired.
+ *
+ * @param cls 'struct Peer' to greylist
+ * @param tc scheduler context
+ */
+static void
+remove_from_greylist (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);
+
+
+/**
+ * Try to connect to the specified peer.
+ *
+ * @param pos peer to connect to
+ */
+static void
+attempt_connect (struct Peer *pos)
+{
+  struct GNUNET_TIME_Relative rem;
+
+  if ((connection_count >= target_connection_count) &&
+      (friend_count >= minimum_friend_count))
+    return;
+  if (GNUNET_YES == pos->is_connected)
+    return;
+  if (GNUNET_OK != is_connection_allowed (pos))
+    return;
+  if (GNUNET_TIME_absolute_get_remaining (pos->greylisted_until).rel_value > 0)
+    return;
+  if (GNUNET_YES == pos->is_friend)
+    rem = GREYLIST_AFTER_ATTEMPT_FRIEND;
+  else
+    rem = GREYLIST_AFTER_ATTEMPT;
+  rem = GNUNET_TIME_relative_multiply (rem, connection_count);
+  rem = GNUNET_TIME_relative_divide (rem, target_connection_count);
+  if (pos->connect_attempts > 30)
+    pos->connect_attempts = 30;
+  rem = GNUNET_TIME_relative_multiply (rem, 1 << (++pos->connect_attempts));
+  rem = GNUNET_TIME_relative_max (rem, GREYLIST_AFTER_ATTEMPT_MIN);
+  rem = GNUNET_TIME_relative_min (rem, GREYLIST_AFTER_ATTEMPT_MAX);
+  pos->greylisted_until = GNUNET_TIME_relative_to_absolute (rem);
+  if (pos->greylist_clean_task != GNUNET_SCHEDULER_NO_TASK)
+    GNUNET_SCHEDULER_cancel (pos->greylist_clean_task);
+  pos->greylist_clean_task =
+      GNUNET_SCHEDULER_add_delayed (rem, &remove_from_greylist, pos);
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Asking  to connect to `%s'\n",
+              GNUNET_i2s (&pos->pid));
+#endif
+  GNUNET_STATISTICS_update (stats,
+                            gettext_noop
+                            ("# connect requests issued to transport"), 1,
+                            GNUNET_NO);
+  GNUNET_TRANSPORT_try_connect (transport, &pos->pid);
+}
+
+
+/**
+ * Discard peer entries for greylisted peers
+ * where the greylisting has expired.
+ *
+ * @param cls 'struct Peer' to greylist
+ * @param tc scheduler context
+ */
+static void
+remove_from_greylist (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct Peer *pos = cls;
+  struct GNUNET_TIME_Relative rem;
+
+  pos->greylist_clean_task = GNUNET_SCHEDULER_NO_TASK;
+  rem = GNUNET_TIME_absolute_get_remaining (pos->greylisted_until);
+  if (rem.rel_value == 0)
+  {
+    attempt_connect (pos);
+  }
+  else
+  {
+    pos->greylist_clean_task =
+        GNUNET_SCHEDULER_add_delayed (rem, &remove_from_greylist, pos);
+  }
+  if ((GNUNET_NO == pos->is_friend) && (GNUNET_NO == pos->is_connected) &&
+      (NULL == pos->hello))
+  {
+    free_peer (NULL, &pos->pid.hashPubKey, pos);
+    return;
+  }
+}
+
+
+/**
+ * Create a new entry in the peer list.
+ *
+ * @param peer identity of the new entry
+ * @param hello hello message, can be NULL
+ * @param is_friend is the new entry for a friend?
+ * @return the new entry
+ */
+static struct Peer *
+make_peer (const struct GNUNET_PeerIdentity *peer,
+           const struct GNUNET_HELLO_Message *hello, int is_friend)
+{
+  struct Peer *ret;
+
+  ret = GNUNET_malloc (sizeof (struct Peer));
+  ret->pid = *peer;
+  ret->is_friend = is_friend;
+  if (hello != NULL)
+  {
+    ret->hello = GNUNET_malloc (GNUNET_HELLO_size (hello));
+    memcpy (ret->hello, hello, GNUNET_HELLO_size (hello));
+  }
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_put (peers, &peer->hashPubKey,
+                                                   ret,
+                                                   GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY));
+  return ret;
+}
+
+
+/**
+ * Setup bloom filter for the given peer entry.
+ *
+ * @param peer entry to initialize
+ */
+static void
+setup_filter (struct Peer *peer)
+{
+  /* 2^{-5} chance of not sending a HELLO to a peer is
+   * acceptably small (if the filter is 50% full);
+   * 64 bytes of memory are small compared to the rest
+   * of the data structure and would only really become
+   * "useless" once a HELLO has been passed on to ~100
+   * other peers, which is likely more than enough in
+   * any case; hence 64, 5 as bloomfilter parameters. */
+  peer->filter = GNUNET_CONTAINER_bloomfilter_init (NULL, 64, 5);
+  peer->filter_expiration =
+      GNUNET_TIME_relative_to_absolute
+      (HELLO_ADVERTISEMENT_MIN_REPEAT_FREQUENCY);
+  /* never send a peer its own HELLO */
+  GNUNET_CONTAINER_bloomfilter_add (peer->filter, &peer->pid.hashPubKey);
+}
+
+
+/**
+ * Function to fill send buffer with HELLO.
+ *
+ * @param cls 'struct Peer' of the target peer
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+hello_advertising_ready (void *cls, size_t size, void *buf);
+
+
+/**
+ * Closure for 'find_advertisable_hello'.
+ */
+struct FindAdvHelloContext
+{
+
+  /**
+   * Peer we want to advertise to.
+   */
+  struct Peer *peer;
+
+  /**
+   * Where to store the result (peer selected for advertising).
+   */
+  struct Peer *result;
+
+  /**
+   * Maximum HELLO size we can use right now.
+   */
+  size_t max_size;
+
+  struct GNUNET_TIME_Relative next_adv;
+};
+
+
+/**
+ * Find a peer that would be reasonable for advertising.
+ *
+ * @param cls closure
+ * @param pid identity of a peer
+ * @param value 'struct Peer*' for the peer we are considering
+ * @return GNUNET_YES (continue iteration)
+ */
+static int
+find_advertisable_hello (void *cls, const GNUNET_HashCode * pid, void *value)
+{
+  struct FindAdvHelloContext *fah = cls;
+  struct Peer *pos = value;
+  struct GNUNET_TIME_Relative rst_time;
+  size_t hs;
+
+  if (pos == fah->peer)
+    return GNUNET_YES;
+  if (pos->hello == NULL)
+    return GNUNET_YES;
+  rst_time = GNUNET_TIME_absolute_get_remaining (pos->filter_expiration);
+  if (0 == rst_time.rel_value)
+  {
+    /* time to discard... */
+    GNUNET_CONTAINER_bloomfilter_free (pos->filter);
+    setup_filter (pos);
+  }
+  fah->next_adv = GNUNET_TIME_relative_min (rst_time, fah->next_adv);
+  hs = GNUNET_HELLO_size (pos->hello);
+  if (hs > fah->max_size)
+    return GNUNET_YES;
+  if (GNUNET_NO ==
+      GNUNET_CONTAINER_bloomfilter_test (pos->filter,
+                                         &fah->peer->pid.hashPubKey))
+    fah->result = pos;
+  return GNUNET_YES;
+}
+
+
+/**
+ * Calculate when we would like to send the next HELLO to this
+ * peer and ask for it.
+ *
+ * @param cls for which peer to schedule the HELLO
+ * @param tc task context
+ */
+static void
+schedule_next_hello (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct Peer *pl = cls;
+  struct FindAdvHelloContext fah;
+  size_t next_want;
+  struct GNUNET_TIME_Relative delay;
+
+  pl->hello_delay_task = GNUNET_SCHEDULER_NO_TASK;
+  GNUNET_assert (GNUNET_YES == pl->is_connected);
+  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
+    return;                     /* we're out of here */
+  if (pl->hello_req != NULL)
+    return;                     /* did not finish sending the previous one */
+  /* find applicable HELLOs */
+  fah.peer = pl;
+  fah.result = NULL;
+  fah.max_size = GNUNET_SERVER_MAX_MESSAGE_SIZE - 1;
+  fah.next_adv = GNUNET_TIME_UNIT_FOREVER_REL;
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &find_advertisable_hello, &fah);
+  pl->hello_delay_task =
+      GNUNET_SCHEDULER_add_delayed (fah.next_adv, &schedule_next_hello, pl);
+  if (fah.result == NULL)
+    return;
+  next_want = GNUNET_HELLO_size (fah.result->hello);
+  delay = GNUNET_TIME_absolute_get_remaining (pl->next_hello_allowed);
+  if (delay.rel_value == 0)
+  {
+    /* now! */
+    pl->hello_req =
+        GNUNET_CORE_notify_transmit_ready (handle, GNUNET_YES, 0,
+                                           GNUNET_CONSTANTS_SERVICE_TIMEOUT,
+                                           &pl->pid, next_want,
+                                           &hello_advertising_ready, pl);
+  }
+}
+
+
+/**
+ * Cancel existing requests for sending HELLOs to this peer
+ * and recalculate when we should send HELLOs to it based
+ * on our current state (something changed!).
+ *
+ * @param cls closure, 'struct Peer' to skip, or NULL
+ * @param pid identity of a peer
+ * @param value 'struct Peer*' for the peer
+ * @return GNUNET_YES (always)
+ */
+static int
+reschedule_hellos (void *cls, const GNUNET_HashCode * pid, void *value)
+{
+  struct Peer *peer = value;
+  struct Peer *skip = cls;
+
+  if (skip == peer)
+    return GNUNET_YES;
+  if (!peer->is_connected)
+    return GNUNET_YES;
+  if (peer->hello_req != NULL)
+  {
+    GNUNET_CORE_notify_transmit_ready_cancel (peer->hello_req);
+    peer->hello_req = NULL;
+  }
+  if (peer->hello_delay_task != GNUNET_SCHEDULER_NO_TASK)
+  {
+    GNUNET_SCHEDULER_cancel (peer->hello_delay_task);
+    peer->hello_delay_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  peer->hello_delay_task =
+      GNUNET_SCHEDULER_add_now (&schedule_next_hello, peer);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Method called whenever a peer connects.
+ *
+ * @param cls closure
+ * @param peer peer identity this notification is about
+ * @param atsi performance data
+ * @param atsi_count number of records in 'atsi'
+ */
+static void
+connect_notify (void *cls, const struct GNUNET_PeerIdentity *peer,
+                const struct GNUNET_ATS_Information *atsi,
+                unsigned int atsi_count)
+{
+  struct Peer *pos;
+
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Core told us that we are connecting to `%s'\n",
+              GNUNET_i2s (peer));
+#endif
+  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+
+  connection_count++;
+  GNUNET_STATISTICS_set (stats, gettext_noop ("# peers connected"),
+                         connection_count, GNUNET_NO);
+  pos = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+  if (pos == NULL)
+  {
+    pos = make_peer (peer, NULL, GNUNET_NO);
+    GNUNET_break (GNUNET_OK == is_connection_allowed (pos));
+  }
+  else
+  {
+    GNUNET_assert (GNUNET_NO == pos->is_connected);
+    pos->greylisted_until.abs_value = 0;        /* remove greylisting */
+  }
+  pos->is_connected = GNUNET_YES;
+  pos->connect_attempts = 0;    /* re-set back-off factor */
+  if (pos->is_friend)
+  {
+    if ((friend_count == minimum_friend_count - 1) &&
+        (GNUNET_YES != friends_only))
+      whitelist_peers ();
+    friend_count++;
+    GNUNET_STATISTICS_set (stats, gettext_noop ("# friends connected"),
+                           friend_count, GNUNET_NO);
+  }
+  reschedule_hellos (NULL, &peer->hashPubKey, pos);
+}
+
+
+/**
+ * Try to add more peers to our connection set.
+ *
+ * @param cls closure, not used
+ * @param pid identity of a peer
+ * @param value 'struct Peer*' for the peer
+ * @return GNUNET_YES (continue to iterate)
+ */
+static int
+try_add_peers (void *cls, const GNUNET_HashCode * pid, void *value)
+{
+  struct Peer *pos = value;
+
+  attempt_connect (pos);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Last task run during shutdown.  Disconnects us from
+ * the transport and core.
+ *
+ * @param cls unused, NULL
+ * @param tc scheduler context
+ */
+static void
+add_peer_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  add_task = GNUNET_SCHEDULER_NO_TASK;
+
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &try_add_peers, NULL);
+}
+
+/**
+ * Method called whenever a peer disconnects.
+ *
+ * @param cls closure
+ * @param peer peer identity this notification is about
+ */
+static void
+disconnect_notify (void *cls, const struct GNUNET_PeerIdentity *peer)
+{
+  struct Peer *pos;
+
+  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Core told us that we disconnected from `%s'\n",
+              GNUNET_i2s (peer));
+#endif
+  pos = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+  if (pos == NULL)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  if (pos->is_connected != GNUNET_YES)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  pos->is_connected = GNUNET_NO;
+  connection_count--;
+  if (NULL != pos->hello_req)
+  {
+    GNUNET_CORE_notify_transmit_ready_cancel (pos->hello_req);
+    pos->hello_req = NULL;
+  }
+  if (GNUNET_SCHEDULER_NO_TASK != pos->hello_delay_task)
+  {
+    GNUNET_SCHEDULER_cancel (pos->hello_delay_task);
+    pos->hello_delay_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  GNUNET_STATISTICS_set (stats, gettext_noop ("# peers connected"),
+                         connection_count, GNUNET_NO);
+  if (pos->is_friend)
+  {
+    friend_count--;
+    GNUNET_STATISTICS_set (stats, gettext_noop ("# friends connected"),
+                           friend_count, GNUNET_NO);
+  }
+  if (((connection_count < target_connection_count) ||
+       (friend_count < minimum_friend_count)) &&
+      (GNUNET_SCHEDULER_NO_TASK == add_task))
+    add_task = GNUNET_SCHEDULER_add_now (&add_peer_task, NULL);
+  if ((friend_count < minimum_friend_count) && (blacklist == NULL))
+    blacklist = GNUNET_TRANSPORT_blacklist (cfg, &blacklist_check, NULL);
+}
+
+
+/**
+ * Iterator called on each address.
+ *
+ * @param cls flag that we will set if we see any addresses
+ * @param address the address of the peer
+ * @param expiration when will the given address expire
+ * @return GNUNET_SYSERR always, to terminate iteration
+ */
+static int
+address_iterator (void *cls, const struct GNUNET_HELLO_Address *address,
+                  struct GNUNET_TIME_Absolute expiration)
+{
+  int *flag = cls;
+
+  *flag = GNUNET_YES;
+  return GNUNET_SYSERR;
+}
+
+
+/**
+ * We've gotten a HELLO from another peer.  Consider it for
+ * advertising.
+ *
+ * @param hello the HELLO we got
+ */
+static void
+consider_for_advertising (const struct GNUNET_HELLO_Message *hello)
+{
+  int have_address;
+  struct GNUNET_PeerIdentity pid;
+  struct GNUNET_TIME_Absolute dt;
+  struct GNUNET_HELLO_Message *nh;
+  struct Peer *peer;
+  uint16_t size;
+
+  if (GNUNET_OK != GNUNET_HELLO_get_id (hello, &pid))
+  {
+    GNUNET_break (0);
+    return;
+  }
+  if (0 == memcmp (&pid, &my_identity, sizeof (struct GNUNET_PeerIdentity)))
+    return;                     /* that's me! */
+  have_address = GNUNET_NO;
+  GNUNET_HELLO_iterate_addresses (hello, GNUNET_NO, &address_iterator,
+                                  &have_address);
+  if (GNUNET_NO == have_address)
+    return;                     /* no point in advertising this one... */
+  peer = GNUNET_CONTAINER_multihashmap_get (peers, &pid.hashPubKey);
+  if (peer == NULL)
+  {
+    peer = make_peer (&pid, hello, GNUNET_NO);
+  }
+  else if (peer->hello != NULL)
+  {
+    dt = GNUNET_HELLO_equals (peer->hello, hello, GNUNET_TIME_absolute_get ());
+    if (dt.abs_value == GNUNET_TIME_UNIT_FOREVER_ABS.abs_value)
+      return;                   /* nothing new here */
+  }
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Found `%s' from peer `%s' for advertising\n", "HELLO",
+              GNUNET_i2s (&pid));
+#endif
+  if (peer->hello != NULL)
+  {
+    nh = GNUNET_HELLO_merge (peer->hello, hello);
+    GNUNET_free (peer->hello);
+    peer->hello = nh;
+  }
+  else
+  {
+    size = GNUNET_HELLO_size (hello);
+    peer->hello = GNUNET_malloc (size);
+    memcpy (peer->hello, hello, size);
+  }
+  if (peer->filter != NULL)
+    GNUNET_CONTAINER_bloomfilter_free (peer->filter);
+  setup_filter (peer);
+  /* since we have a new HELLO to pick from, re-schedule all
+   * HELLO requests that are not bound by the HELLO send rate! */
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &reschedule_hellos, peer);
+}
+
+
+/**
+ * PEERINFO calls this function to let us know about a possible peer
+ * that we might want to connect to.
+ *
+ * @param cls closure (not used)
+ * @param peer potential peer to connect to
+ * @param hello HELLO for this peer (or NULL)
+ * @param err_msg NULL if successful, otherwise contains error message
+ */
+static void
+process_peer (void *cls, const struct GNUNET_PeerIdentity *peer,
+              const struct GNUNET_HELLO_Message *hello, const char *err_msg)
+{
+  struct Peer *pos;
+
+  if (err_msg != NULL)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                _("Error in communication with PEERINFO service: %s\n"),
+                err_msg);
+    GNUNET_PEERINFO_notify_cancel (peerinfo_notify);
+    peerinfo_notify = GNUNET_PEERINFO_notify (cfg, &process_peer, NULL);
+    return;
+  }
+  GNUNET_assert (peer != NULL);
+  if (0 == memcmp (&my_identity, peer, sizeof (struct GNUNET_PeerIdentity)))
+    return;                     /* that's me! */
+  if (hello == NULL)
+  {
+    /* free existing HELLO, if any */
+    pos = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+    if (NULL != pos)
+    {
+      GNUNET_free_non_null (pos->hello);
+      pos->hello = NULL;
+      if (pos->filter != NULL)
+      {
+        GNUNET_CONTAINER_bloomfilter_free (pos->filter);
+        pos->filter = NULL;
+      }
+      if ((!pos->is_connected) && (!pos->is_friend) &&
+          (0 ==
+           GNUNET_TIME_absolute_get_remaining (pos->
+                                               greylisted_until).rel_value))
+        free_peer (NULL, &pos->pid.hashPubKey, pos);
+    }
+    return;
+  }
+  consider_for_advertising (hello);
+  pos = GNUNET_CONTAINER_multihashmap_get (peers, &peer->hashPubKey);
+  if (pos == NULL)
+    pos = make_peer (peer, hello, GNUNET_NO);
+  GNUNET_assert (NULL != pos);
+  if (GNUNET_YES == pos->is_connected)
+  {
+#if DEBUG_TOPOLOGY
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Already connected to peer `%s'\n",
+                GNUNET_i2s (peer));
+#endif
+    return;
+  }
+  if (GNUNET_TIME_absolute_get_remaining (pos->greylisted_until).rel_value > 0)
+  {
+#if DEBUG_TOPOLOGY
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Already tried peer `%s' recently\n",
+                GNUNET_i2s (peer));
+#endif
+    return;                     /* peer still greylisted */
+  }
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Considering connecting to peer `%s'\n",
+              GNUNET_i2s (peer));
+#endif
+  attempt_connect (pos);
+}
+
+
+/**
+ * Function called after GNUNET_CORE_connect has succeeded
+ * (or failed for good).
+ *
+ * @param cls closure
+ * @param server handle to the server, NULL if we failed
+ * @param my_id ID of this peer, NULL if we failed
+ */
+static void
+core_init (void *cls, struct GNUNET_CORE_Handle *server,
+           const struct GNUNET_PeerIdentity *my_id)
+{
+  if (server == NULL)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _
+                ("Failed to connect to core service, can not manage topology!\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  handle = server;
+  my_identity = *my_id;
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "I am peer `%s'\n", GNUNET_i2s (my_id));
+#endif
+  peerinfo_notify = GNUNET_PEERINFO_notify (cfg, &process_peer, NULL);
+}
+
+
+/**
+ * Read the friends file.
+ */
+static void
+read_friends_file (const struct GNUNET_CONFIGURATION_Handle *cfg)
+{
+  char *fn;
+  char *data;
+  size_t pos;
+  struct GNUNET_PeerIdentity pid;
+  struct stat frstat;
+  struct GNUNET_CRYPTO_HashAsciiEncoded enc;
+  unsigned int entries_found;
+  struct Peer *fl;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg, "TOPOLOGY", "FRIENDS", &fn))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _("Option `%s' in section `%s' not specified!\n"), "FRIENDS",
+                "TOPOLOGY");
+    return;
+  }
+  if (GNUNET_OK != GNUNET_DISK_file_test (fn))
+    GNUNET_DISK_fn_write (fn, NULL, 0,
+                          GNUNET_DISK_PERM_USER_READ |
+                          GNUNET_DISK_PERM_USER_WRITE);
+  if (0 != STAT (fn, &frstat))
+  {
+    if ((friends_only) || (minimum_friend_count > 0))
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  _("Could not read friends list `%s'\n"), fn);
+    GNUNET_free (fn);
+    return;
+  }
+  if (frstat.st_size == 0)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _("Friends file `%s' is empty.\n"),
+                fn);
+    GNUNET_free (fn);
+    return;
+  }
+  data = GNUNET_malloc_large (frstat.st_size);
+  if (data == NULL)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("Failed to read friends list from `%s': out of memory\n"),
+                fn);
+    GNUNET_free (fn);
+    return;
+  }
+  if (frstat.st_size != GNUNET_DISK_fn_read (fn, data, frstat.st_size))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("Failed to read friends list from `%s'\n"), fn);
+    GNUNET_free (fn);
+    GNUNET_free (data);
+    return;
+  }
+  entries_found = 0;
+  pos = 0;
+  while ((pos < frstat.st_size) && isspace ((unsigned char) data[pos]))
+    pos++;
+  while ((frstat.st_size >= sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded)) &&
+         (pos <=
+          frstat.st_size - sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded)))
+  {
+    memcpy (&enc, &data[pos], sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded));
+    if (!isspace
+        ((unsigned char)
+         enc.encoding[sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded) - 1]))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  _
+                  ("Syntax error in topology specification at offset %llu, skipping bytes.\n"),
+                  (unsigned long long) pos);
+      pos++;
+      while ((pos < frstat.st_size) && (!isspace ((unsigned char) data[pos])))
+        pos++;
+      continue;
+    }
+    enc.encoding[sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded) - 1] = '\0';
+    if (GNUNET_OK !=
+        GNUNET_CRYPTO_hash_from_string ((char *) &enc, &pid.hashPubKey))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  _
+                  ("Syntax error in topology specification at offset %llu, skipping bytes `%s'.\n"),
+                  (unsigned long long) pos, &enc);
+    }
+    else
+    {
+      if (0 != memcmp (&pid, &my_identity, sizeof (struct GNUNET_PeerIdentity)))
+      {
+        entries_found++;
+        fl = make_peer (&pid, NULL, GNUNET_YES);
+        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                    _("Found friend `%s' in configuration\n"),
+                    GNUNET_i2s (&fl->pid));
+      }
+      else
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                    _("Found myself `%s' in friend list (useless, ignored)\n"),
+                    GNUNET_i2s (&pid));
+      }
+    }
+    pos = pos + sizeof (struct GNUNET_CRYPTO_HashAsciiEncoded);
+    while ((pos < frstat.st_size) && isspace ((unsigned char) data[pos]))
+      pos++;
+  }
+  GNUNET_free (data);
+  GNUNET_free (fn);
+  GNUNET_STATISTICS_update (stats, gettext_noop ("# friends in configuration"),
+                            entries_found, GNUNET_NO);
+  if ((minimum_friend_count > entries_found) && (friends_only == GNUNET_NO))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _
+                ("Fewer friends specified than required by minimum friend count. Will only connect to friends.\n"));
+  }
+  if ((minimum_friend_count > target_connection_count) &&
+      (friends_only == GNUNET_NO))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                _
+                ("More friendly connections required than target total number of connections.\n"));
+  }
+}
+
+
+/**
+ * This function is called whenever an encrypted HELLO message is
+ * received.
+ *
+ * @param cls closure
+ * @param other the other peer involved (sender or receiver, NULL
+ *        for loopback messages where we are both sender and receiver)
+ * @param message the actual HELLO message
+ * @param atsi performance data
+ * @param atsi_count number of records in 'atsi'
+ * @return GNUNET_OK to keep the connection open,
+ *         GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+handle_encrypted_hello (void *cls, const struct GNUNET_PeerIdentity *other,
+                        const struct GNUNET_MessageHeader *message,
+                        const struct GNUNET_ATS_Information *atsi,
+                        unsigned int atsi_count)
+{
+  struct Peer *peer;
+  struct GNUNET_PeerIdentity pid;
+
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Received encrypted `%s' from peer `%s'",
+              "HELLO", GNUNET_i2s (other));
+#endif
+  if (GNUNET_OK !=
+      GNUNET_HELLO_get_id ((const struct GNUNET_HELLO_Message *) message, &pid))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  GNUNET_STATISTICS_update (stats, gettext_noop ("# HELLO messages received"),
+                            1, GNUNET_NO);
+  peer = GNUNET_CONTAINER_multihashmap_get (peers, &pid.hashPubKey);
+  if (peer == NULL)
+  {
+    if ((GNUNET_YES == friends_only) || (friend_count < minimum_friend_count))
+      return GNUNET_OK;
+  }
+  else
+  {
+    if ((GNUNET_YES != peer->is_friend) && (GNUNET_YES == friends_only))
+      return GNUNET_OK;
+    if ((GNUNET_YES != peer->is_friend) &&
+        (friend_count < minimum_friend_count))
+      return GNUNET_OK;
+  }
+  if (transport != NULL)
+    GNUNET_TRANSPORT_offer_hello (transport, message, NULL, NULL);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Function to fill send buffer with HELLO.
+ *
+ * @param cls 'struct Peer' of the target peer
+ * @param size number of bytes available in buf
+ * @param buf where the callee should write the message
+ * @return number of bytes written to buf
+ */
+static size_t
+hello_advertising_ready (void *cls, size_t size, void *buf)
+{
+  struct Peer *pl = cls;
+  struct FindAdvHelloContext fah;
+  size_t want;
+
+  pl->hello_req = NULL;
+  GNUNET_assert (GNUNET_YES == pl->is_connected);
+  /* find applicable HELLOs */
+  fah.peer = pl;
+  fah.result = NULL;
+  fah.max_size = size;
+  fah.next_adv = GNUNET_TIME_UNIT_FOREVER_REL;
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &find_advertisable_hello, &fah);
+  want = 0;
+  if (fah.result != NULL)
+  {
+    want = GNUNET_HELLO_size (fah.result->hello);
+    GNUNET_assert (want <= size);
+    memcpy (buf, fah.result->hello, want);
+    GNUNET_CONTAINER_bloomfilter_add (fah.result->filter, &pl->pid.hashPubKey);
+#if DEBUG_TOPOLOGY
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sending `%s' with %u bytes", "HELLO",
+                (unsigned int) want);
+#endif
+    GNUNET_STATISTICS_update (stats,
+                              gettext_noop ("# HELLO messages gossipped"), 1,
+                              GNUNET_NO);
+  }
+
+  if (pl->hello_delay_task != GNUNET_SCHEDULER_NO_TASK)
+    GNUNET_SCHEDULER_cancel (pl->hello_delay_task);
+  pl->next_hello_allowed =
+      GNUNET_TIME_relative_to_absolute (HELLO_ADVERTISEMENT_MIN_FREQUENCY);
+  pl->hello_delay_task = GNUNET_SCHEDULER_add_now (&schedule_next_hello, pl);
+  return want;
+}
+
+
+/**
+ * Last task run during shutdown.  Disconnects us from
+ * the transport and core.
+ *
+ * @param cls unused, NULL
+ * @param tc scheduler context
+ */
+static void
+cleaning_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  if (NULL != peerinfo_notify)
+  {
+    GNUNET_PEERINFO_notify_cancel (peerinfo_notify);
+    peerinfo_notify = NULL;
+  }
+  if (GNUNET_SCHEDULER_NO_TASK != add_task)
+  {
+    GNUNET_SCHEDULER_cancel (add_task);
+    add_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  GNUNET_TRANSPORT_disconnect (transport);
+  transport = NULL;
+  GNUNET_CONTAINER_multihashmap_iterate (peers, &free_peer, NULL);
+  GNUNET_CONTAINER_multihashmap_destroy (peers);
+  if (handle != NULL)
+  {
+    GNUNET_CORE_disconnect (handle);
+    handle = NULL;
+  }
+  whitelist_peers ();
+  if (stats != NULL)
+  {
+    GNUNET_STATISTICS_destroy (stats, GNUNET_NO);
+    stats = NULL;
+  }
+}
+
+
+/**
+ * Main function that will be run.
+ *
+ * @param cls closure
+ * @param args remaining command-line arguments
+ * @param cfgfile name of the configuration file used (for saving, can be NULL!)
+ * @param c configuration
+ */
+static void
+run (void *cls, char *const *args, const char *cfgfile,
+     const struct GNUNET_CONFIGURATION_Handle *c)
+{
+  static struct GNUNET_CORE_MessageHandler handlers[] = {
+    {&handle_encrypted_hello, GNUNET_MESSAGE_TYPE_HELLO, 0},
+    {NULL, 0, 0}
+  };
+  unsigned long long opt;
+
+  cfg = c;
+  stats = GNUNET_STATISTICS_create ("topology", cfg);
+  autoconnect =
+      GNUNET_CONFIGURATION_get_value_yesno (cfg, "TOPOLOGY", "AUTOCONNECT");
+  friends_only =
+      GNUNET_CONFIGURATION_get_value_yesno (cfg, "TOPOLOGY", "FRIENDS-ONLY");
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_number (cfg, "TOPOLOGY", "MINIMUM-FRIENDS",
+                                             &opt))
+    opt = 0;
+  minimum_friend_count = (unsigned int) opt;
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_number (cfg, "TOPOLOGY",
+                                             "TARGET-CONNECTION-COUNT", &opt))
+    opt = 16;
+  target_connection_count = (unsigned int) opt;
+  peers = GNUNET_CONTAINER_multihashmap_create (target_connection_count * 2);
+
+  if ((friends_only == GNUNET_YES) || (minimum_friend_count > 0))
+    read_friends_file (cfg);
+#if DEBUG_TOPOLOGY
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Topology would like %u connections with at least %u friends (%s)\n",
+              target_connection_count, minimum_friend_count,
+              autoconnect ? "autoconnect enabled" : "autoconnect disabled");
+#endif
+  if ((friend_count < minimum_friend_count) && (blacklist == NULL))
+    blacklist = GNUNET_TRANSPORT_blacklist (cfg, &blacklist_check, NULL);
+  transport = GNUNET_TRANSPORT_connect (cfg, NULL, NULL, NULL, NULL, NULL);
+  handle =
+      GNUNET_CORE_connect (cfg, 1, NULL, &core_init, &connect_notify,
+                           &disconnect_notify, NULL, GNUNET_NO, NULL, GNUNET_NO,
+                           handlers);
+  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &cleaning_task,
+                                NULL);
+  if (NULL == transport)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("Failed to connect to `%s' service.\n"), "transport");
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (NULL == handle)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _("Failed to connect to `%s' service.\n"), "core");
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+}
+
+
+/**
+ * The main function for the topology daemon.
+ *
+ * @param argc number of arguments from the command line
+ * @param argv command line arguments
+ * @return 0 ok, 1 on error
+ */
+int
+main (int argc, char *const *argv)
+{
+  static const struct GNUNET_GETOPT_CommandLineOption options[] = {
+    GNUNET_GETOPT_OPTION_END
+  };
+  int ret;
+
+  ret =
+      (GNUNET_OK ==
+       GNUNET_PROGRAM_run (argc, argv, "gnunet-daemon-topology",
+                           _
+                           ("GNUnet topology control (maintaining P2P mesh and F2F constraints)"),
+                           options, &run, NULL)) ? 0 : 1;
+  return ret;
+}
+
+/* end of gnunet-daemon-topology.c */