Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1075 insertions, 0 deletions

diff --git a/src/mesh/mesh_tunnel_tree.c b/src/mesh/mesh_tunnel_tree.c
new file mode 100644
index 0000000..445b710
--- /dev/null
+++ b/src/mesh/mesh_tunnel_tree.c
@@ -0,0 +1,1075 @@
+/*
+     This file is part of GNUnet.
+     (C) 2001 - 2011 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 mesh/mesh_tunnel_tree.c
+ * @brief Tunnel tree handling functions
+ * @author Bartlomiej Polot
+ */
+
+#include "mesh.h"
+#include "mesh_tunnel_tree.h"
+
+#define MESH_TREE_DEBUG GNUNET_YES
+
+
+/**
+ * Node of path tree for a tunnel
+ */
+struct MeshTunnelTreeNode
+{
+  /**
+   * Peer this node describes
+   */
+  GNUNET_PEER_Id peer;
+
+  /**
+   * Parent node in the tree
+   */
+  struct MeshTunnelTreeNode *parent;
+
+  /**
+   * DLL of siblings
+   */
+  struct MeshTunnelTreeNode *next;
+
+  /**
+   * DLL of siblings
+   */
+  struct MeshTunnelTreeNode *prev;
+
+  /**
+   * DLL of children
+   */
+  struct MeshTunnelTreeNode *children_head;
+
+  /**
+   * DLL of children
+   */
+  struct MeshTunnelTreeNode *children_tail;
+
+    /**
+     * Status of the peer in the tunnel
+     */
+  enum MeshPeerState status;
+};
+
+
+/**
+ * Tree to reach all peers in the tunnel
+ */
+struct MeshTunnelTree
+{
+  /**
+   * Root node of peer tree
+   */
+  struct MeshTunnelTreeNode *root;
+
+  /**
+   * Node that represents our position in the tree (for non local tunnels)
+   */
+  struct MeshTunnelTreeNode *me;
+
+  /**
+   * DLL of disconneted nodes
+   */
+  struct MeshTunnelTreeNode *disconnected_head;
+
+  /**
+   * DLL of disconneted nodes
+   */
+  struct MeshTunnelTreeNode *disconnected_tail;
+
+  /**
+   * Cache of all peers and the first hop to them.
+   * Indexed by PeerIdentity, contains a pointer to the PeerIdentity
+   * of 1st hop.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *first_hops;
+
+};
+
+
+/**
+ * Create a new path
+ *
+ * @param length How many hops will the path have.
+ *
+ * @return A newly allocated path with a peer array of the specified length.
+ */
+struct MeshPeerPath *
+path_new (unsigned int length)
+{
+  struct MeshPeerPath *p;
+
+  p = GNUNET_malloc (sizeof (struct MeshPeerPath));
+  if (length > 0)
+  {
+    p->length = length;
+    p->peers = GNUNET_malloc (length * sizeof (GNUNET_PEER_Id));
+  }
+  return p;
+}
+
+
+/**
+ * Invert the path
+ *
+ * @param path the path to invert
+ */
+void
+path_invert (struct MeshPeerPath *path)
+{
+  GNUNET_PEER_Id aux;
+  unsigned int i;
+
+  for (i = 0; i < path->length / 2; i++)
+  {
+    aux = path->peers[i];
+    path->peers[i] = path->peers[path->length - i - 1];
+    path->peers[path->length - i - 1] = aux;
+  }
+}
+
+
+/**
+ * Duplicate a path, incrementing short peer's rc.
+ *
+ * @param path The path to duplicate.
+ */
+struct MeshPeerPath *
+path_duplicate (struct MeshPeerPath *path)
+{
+  struct MeshPeerPath *aux;
+  unsigned int i;
+
+  aux = path_new (path->length);
+  memcpy (aux->peers, path->peers, path->length * sizeof (GNUNET_PEER_Id));
+  for (i = 0; i < path->length; i++)
+    GNUNET_PEER_change_rc (path->peers[i], 1);
+  return aux;
+}
+
+
+/**
+ * Recusively update the info about what is the first hop to reach the node
+ *
+ * @param tree Tree this nodes belongs to.
+ * @param parent The node form which to start updating.
+ * @param hop If known, ID of the first hop.
+ *            If not known, NULL to find out and pass on children.
+ */
+static void
+tree_node_update_first_hops (struct MeshTunnelTree *tree,
+                             struct MeshTunnelTreeNode *parent,
+                             struct GNUNET_PeerIdentity *hop);
+
+
+/**
+ * Get the length of a path.
+ *
+ * @param path The path to measure, with the local peer at any point of it.
+ *
+ * @return Number of hops to reach destination.
+ *         UINT_MAX in case the peer is not in the path.
+ */
+unsigned int
+path_get_length (struct MeshPeerPath *path)
+{
+  if (NULL == path)
+    return UINT_MAX;
+  return path->length;
+}
+
+
+/**
+ * Destroy the path and free any allocated resources linked to it
+ *
+ * @param p the path to destroy
+ *
+ * @return GNUNET_OK on success
+ */
+int
+path_destroy (struct MeshPeerPath *p)
+{
+  if (NULL == p)
+    return GNUNET_OK;
+  GNUNET_PEER_decrement_rcs (p->peers, p->length);
+  GNUNET_free_non_null (p->peers);
+  GNUNET_free (p);
+  return GNUNET_OK;
+}
+
+
+
+/**
+ * Allocates and initializes a new node.
+ * Sets ID and parent of the new node and inserts it in the DLL of the parent
+ *
+ * @param parent Node that will be the parent from the new node, NULL for root
+ * @param peer Short Id of the new node
+ *
+ * @return Newly allocated node
+ */
+static struct MeshTunnelTreeNode *
+tree_node_new (struct MeshTunnelTreeNode *parent, GNUNET_PEER_Id peer)
+{
+  struct MeshTunnelTreeNode *node;
+
+  node = GNUNET_malloc (sizeof (struct MeshTunnelTreeNode));
+  node->peer = peer;
+  GNUNET_PEER_change_rc (peer, 1);
+  node->parent = parent;
+  if (NULL != parent)
+    GNUNET_CONTAINER_DLL_insert (parent->children_head, parent->children_tail,
+                                 node);
+
+  return node;
+}
+
+
+/**
+ * Recursively find the given peer.
+ *
+ * @param parent Node where to start looking.
+ * @param peer_id Short ID of the peer to find.
+ *
+ * @return Pointer to the node of the peer. NULL if not found.
+ */
+static struct MeshTunnelTreeNode *
+tree_node_find_peer (struct MeshTunnelTreeNode *parent, GNUNET_PEER_Id peer_id)
+{
+  struct MeshTunnelTreeNode *n;
+  struct MeshTunnelTreeNode *r;
+
+  if (parent->peer == peer_id)
+    return parent;
+  for (n = parent->children_head; NULL != n; n = n->next)
+  {
+    r = tree_node_find_peer (n, peer_id);
+    if (NULL != r)
+      return r;
+  }
+  return NULL;
+}
+
+
+/**
+ * Recusively update the info about what is the first hop to reach the node
+ *
+ * @param tree Tree this nodes belongs to.
+ * @param parent ID from node form which to start updating.
+ * @param hop If known, ID of the first hop.
+ *            If not known, NULL to find out and pass on children.
+ */
+static void
+tree_node_update_first_hops (struct MeshTunnelTree *tree,
+                             struct MeshTunnelTreeNode *parent,
+                             struct GNUNET_PeerIdentity *hop)
+{
+  struct GNUNET_PeerIdentity pi;
+  struct GNUNET_PeerIdentity *copy;
+  struct GNUNET_PeerIdentity id;
+  struct MeshTunnelTreeNode *n;
+
+#if MESH_TREE_DEBUG
+  GNUNET_PEER_resolve (parent->peer, &id);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Finding first hop for %s.\n",
+              GNUNET_i2s (&id));
+#endif
+  if (NULL == hop)
+  {
+    struct MeshTunnelTreeNode *aux;
+    struct MeshTunnelTreeNode *old;
+
+    aux = old = parent;
+    while (aux != tree->me)
+    {
+#if MESH_TREE_DEBUG
+      GNUNET_PEER_resolve (aux->peer, &id);
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   ... checking %s.\n",
+                  GNUNET_i2s (&id));
+#endif
+      old = aux;
+      aux = aux->parent;
+      GNUNET_assert (NULL != aux);
+    }
+#if MESH_TREE_DEBUG
+    GNUNET_PEER_resolve (old->peer, &id);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   It's %s!\n",
+                GNUNET_i2s (&id));
+#endif
+    hop = &pi;
+    GNUNET_PEER_resolve (old->peer, hop);
+  }
+  GNUNET_PEER_resolve (parent->peer, &id);
+  copy = GNUNET_CONTAINER_multihashmap_get (tree->first_hops, &id.hashPubKey);
+  if (NULL == copy)
+    copy = GNUNET_malloc (sizeof (struct GNUNET_PeerIdentity));
+  *copy = *hop;
+
+  (void) GNUNET_CONTAINER_multihashmap_put (tree->first_hops, &id.hashPubKey,
+                                            copy,
+                                            GNUNET_CONTAINER_MULTIHASHMAPOPTION_REPLACE);
+
+  for (n = parent->children_head; NULL != n; n = n->next)
+  {
+    tree_node_update_first_hops (tree, n, hop);
+  }
+}
+
+
+static void
+tree_node_debug (struct MeshTunnelTreeNode *n, uint16_t level)
+{
+  struct MeshTunnelTreeNode *c;
+  struct GNUNET_PeerIdentity id;;
+  uint16_t i;
+
+  for (i = 0; i < level; i++)
+    FPRINTF (stderr, "%s",  "  ");
+  if (n->status == MESH_PEER_READY)
+    FPRINTF (stderr, "%s",  "#");
+  if (n->status == MESH_PEER_SEARCHING)
+    FPRINTF (stderr, "%s",  "+");
+  if (n->status == MESH_PEER_RELAY)
+    FPRINTF (stderr, "%s",  "-");
+  if (n->status == MESH_PEER_RECONNECTING)
+    FPRINTF (stderr, "%s",  "*");
+
+  GNUNET_PEER_resolve (n->peer, &id);
+  FPRINTF (stderr, "%s, [%u, %p] ", GNUNET_i2s (&id), n->peer, n);
+  if (NULL != n->parent)
+  {
+    GNUNET_PEER_resolve (n->parent->peer, &id);
+    FPRINTF (stderr, "(-> %s [%u])\n", GNUNET_i2s (&id), n->parent->peer);
+  }
+  else
+    FPRINTF (stderr, "%s",  "(root)\n");
+  for (c = n->children_head; NULL != c; c = c->next)
+    tree_node_debug (c, level + 1);
+}
+
+
+/**
+ * Destroys and frees the node and all children
+ *
+ * @param parent Parent node to be destroyed
+ */
+static void
+tree_node_destroy (struct MeshTunnelTreeNode *parent)
+{
+  struct MeshTunnelTreeNode *n;
+  struct MeshTunnelTreeNode *next;
+
+#if MESH_TREE_DEBUG
+  struct GNUNET_PeerIdentity id;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree: Destroying node %u\n",
+              parent->peer);
+  GNUNET_PEER_resolve (parent->peer, &id);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   (%s)\n", GNUNET_i2s (&id));
+#endif
+  n = parent->children_head;
+  while (NULL != n)
+  {
+    next = n->next;
+    tree_node_destroy (n);
+    n = next;
+  }
+  GNUNET_PEER_change_rc (parent->peer, -1);
+  if (NULL != parent->parent)
+    GNUNET_CONTAINER_DLL_remove (parent->parent->children_head,
+                                 parent->parent->children_tail, parent);
+  GNUNET_free (parent);
+}
+
+
+
+/**
+ * Create a new tree.
+ *
+ * @param peer A short peer id of the root of the tree.
+ *
+ * @return A newly allocated and initialized tunnel tree.
+ */
+struct MeshTunnelTree *
+tree_new (GNUNET_PEER_Id peer)
+{
+  struct MeshTunnelTree *tree;
+
+  tree = GNUNET_malloc (sizeof (struct MeshTunnelTree));
+  tree->first_hops = GNUNET_CONTAINER_multihashmap_create (32);
+  tree->root = tree_node_new (NULL, peer);
+  tree->root->status = MESH_PEER_ROOT;
+
+  if (1 == peer)
+  {
+    tree->me = tree->root;
+  }
+
+  return tree;
+}
+
+
+/**
+ * Set the status of a node.
+ *
+ * @param tree Tree.
+ * @param peer A short peer id of the node.
+ * @param status New status to set.
+ */
+void
+tree_set_status (struct MeshTunnelTree *tree, GNUNET_PEER_Id peer,
+                 enum MeshPeerState status)
+{
+  struct MeshTunnelTreeNode *n;
+
+  n = tree_find_peer (tree, peer);
+  if (NULL == n)
+    return;
+  n->status = status;
+}
+
+
+/**
+ * Get the status of a node.
+ *
+ * @param tree Tree whose node's status we want to now.
+ * @param peer A short peer id of the node.
+ *
+ * @return Status of the peer.
+ */
+enum MeshPeerState
+tree_get_status (struct MeshTunnelTree *tree, GNUNET_PEER_Id peer)
+{
+  struct MeshTunnelTreeNode *n;
+
+  n = tree_find_peer (tree, peer);
+  if (NULL == n)
+    return MESH_PEER_INVALID;
+  return n->status;
+}
+
+
+/**
+ * Get the id of the predecessor of the local node.
+ *
+ * @param tree Tree whose local id we want to now.
+ *
+ * @return Short peer id of local peer.
+ */
+GNUNET_PEER_Id
+tree_get_predecessor (struct MeshTunnelTree *tree)
+{
+  if (NULL != tree->me && NULL != tree->me->parent)
+    return tree->me->parent->peer;
+  else
+    return (GNUNET_PEER_Id) 0;
+}
+
+
+/**
+ * Find the first peer whom to send a packet to go down this path
+ *
+ * @param t The tunnel tree to use
+ * @param peer The peerinfo of the peer we are trying to reach
+ *
+ * @return peerinfo of the peer who is the first hop in the tunnel
+ *         NULL on error
+ */
+struct GNUNET_PeerIdentity *
+tree_get_first_hop (struct MeshTunnelTree *t, GNUNET_PEER_Id peer)
+{
+  struct GNUNET_PeerIdentity id;
+  struct GNUNET_PeerIdentity *r;
+
+  GNUNET_PEER_resolve (peer, &id);
+  r = GNUNET_CONTAINER_multihashmap_get (t->first_hops, &id.hashPubKey);
+  if (NULL == r)
+  {
+    struct MeshTunnelTreeNode *n;
+
+    n = tree_find_peer (t, peer);
+    if (NULL != t->me && NULL != n)
+    {
+      tree_node_update_first_hops (t, n, NULL);
+      r = GNUNET_CONTAINER_multihashmap_get (t->first_hops, &id.hashPubKey);
+      GNUNET_assert (NULL != r);
+    }
+    else
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  "Tree structure inconsistent! me: %p, n: %p", t->me, n);
+      GNUNET_break (0);
+    }
+  }
+
+  return r;
+}
+
+
+/**
+ * Find the given peer in the tree.
+ *
+ * @param tree Tree where to look for the peer.
+ * @param peer_id Short ID of the peer to find.
+ *
+ * @return Pointer to the node of the peer. NULL if not found.
+ */
+struct MeshTunnelTreeNode *
+tree_find_peer (struct MeshTunnelTree *tree, GNUNET_PEER_Id peer_id)
+{
+  return tree_node_find_peer (tree->root, peer_id);
+}
+
+
+/**
+ * Recusively mark peer and children as disconnected, notify client
+ *
+ * @param tree Tree this node belongs to
+ * @param parent Node to be clean, potentially with children
+ * @param cb Callback to use to notify about disconnected peers.
+ * @param cbcls Closure for cb.
+ */
+static void
+tree_mark_peers_disconnected (struct MeshTunnelTree *tree,
+                              struct MeshTunnelTreeNode *parent,
+                              MeshTreeCallback cb, void *cbcls)
+{
+  struct GNUNET_PeerIdentity *pi;
+  struct GNUNET_PeerIdentity id;
+  struct MeshTunnelTreeNode *n;
+
+  for (n = parent->children_head; NULL != n; n = n->next)
+  {
+    tree_mark_peers_disconnected (tree, n, cb, cbcls);
+  }
+  if (MESH_PEER_READY == parent->status)
+  {
+    if (NULL != cb)
+      cb (cbcls, parent->peer);
+    parent->status = MESH_PEER_RECONNECTING;
+  }
+
+  /* Remove and free info about first hop */
+  GNUNET_PEER_resolve (parent->peer, &id);
+  pi = GNUNET_CONTAINER_multihashmap_get (tree->first_hops, &id.hashPubKey);
+  GNUNET_CONTAINER_multihashmap_remove_all (tree->first_hops, &id.hashPubKey);
+  if (NULL != pi)
+    GNUNET_free (pi);
+}
+
+
+/**
+ * Iterate over all children of the local node.
+ *
+ * @param tree Tree to use. Must have "me" set.
+ * @param cb Callback to call over each child.
+ * @param cls Closure.
+ */
+void
+tree_iterate_children (struct MeshTunnelTree *tree, MeshTreeCallback cb,
+                       void *cls)
+{
+  struct MeshTunnelTreeNode *n;
+
+  if (NULL == tree->me)
+  {
+    GNUNET_break (0);
+    return;
+  }
+  for (n = tree->me->children_head; NULL != n; n = n->next)
+  {
+    cb (cls, n->peer);
+  }
+}
+
+
+/**
+ * Recusively update the info about what is the first hop to reach the node
+ *
+ * @param tree Tree this nodes belongs to.
+ * @param parent_id Short ID from node form which to start updating.
+ * @param hop If known, ID of the first hop.
+ *            If not known, NULL to find out and pass on children.
+ */
+void
+tree_update_first_hops (struct MeshTunnelTree *tree, GNUNET_PEER_Id parent_id,
+                        struct GNUNET_PeerIdentity *hop)
+{
+  tree_node_update_first_hops (tree, tree_find_peer (tree, parent_id), hop);
+}
+
+
+/**
+ * Delete the current path to the peer, including all now unused relays.
+ * The destination peer is NOT destroyed, it is returned in order to either set
+ * a new path to it or destroy it explicitly, taking care of it's child nodes.
+ *
+ * @param t Tunnel tree where to delete the path from.
+ * @param peer_id Short ID of the destination peer whose path we want to remove.
+ * @param cb Callback to use to notify about disconnected peers.
+ * @param cbcls Closure for cb.
+ *
+ * @return pointer to the pathless node.
+ *         NULL when not found
+ */
+struct MeshTunnelTreeNode *
+tree_del_path (struct MeshTunnelTree *t, GNUNET_PEER_Id peer_id,
+               MeshTreeCallback cb, void *cbcls)
+{
+  struct MeshTunnelTreeNode *parent;
+  struct MeshTunnelTreeNode *node;
+  struct MeshTunnelTreeNode *n;
+
+#if MESH_TREE_DEBUG
+  struct GNUNET_PeerIdentity id;
+
+  GNUNET_PEER_resolve (peer_id, &id);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Deleting path to %s.\n",
+              GNUNET_i2s (&id));
+#endif
+  if (peer_id == t->root->peer)
+    return NULL;
+
+  for (n = t->disconnected_head; NULL != n; n = n->next)
+  {
+    if (n->peer == peer_id)
+    {
+      /* Was already pathless, waiting for reconnection */
+      GNUNET_CONTAINER_DLL_remove (t->disconnected_head, t->disconnected_tail,
+                                   n);
+      return n;
+    }
+  }
+  n = tree_find_peer (t, peer_id);
+  if (NULL == n)
+    return NULL;
+  node = n;
+
+  parent = n->parent;
+  GNUNET_CONTAINER_DLL_remove (parent->children_head, parent->children_tail, n);
+  n->parent = NULL;
+
+  while (MESH_PEER_RELAY == parent->status && NULL == parent->children_head)
+  {
+#if MESH_TREE_DEBUG
+    GNUNET_PEER_resolve (parent->peer, &id);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Deleting node %s.\n",
+                GNUNET_i2s (&id));
+#endif
+    n = parent->parent;
+    tree_node_destroy (parent);
+    parent = n;
+  }
+#if MESH_TREE_DEBUG
+  GNUNET_PEER_resolve (parent->peer, &id);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Not deleted peer %s.\n",
+              GNUNET_i2s (&id));
+#endif
+
+  tree_mark_peers_disconnected (t, node, cb, cbcls);
+
+  return node;
+}
+
+
+/**
+ * Return a newly allocated individual path to reach a peer from the local peer,
+ * according to the path tree of some tunnel.
+ *
+ * @param t Tunnel from which to read the path tree.
+ * @param peer Short ID of the destination peer to whom we want a path.
+ *
+ * @return A newly allocated individual path to reach the destination peer.
+ *         Path must be destroyed afterwards.
+ */
+struct MeshPeerPath *
+tree_get_path_to_peer (struct MeshTunnelTree *t, GNUNET_PEER_Id peer)
+{
+  struct MeshTunnelTreeNode *n;
+  struct MeshPeerPath *p;
+
+  n = tree_find_peer (t, peer);
+  if (NULL == n)
+  {
+    GNUNET_break (0);
+    return NULL;
+  }
+  p = path_new (0);
+
+  /* Building the path (inverted!) */
+  while (n->peer != 1)
+  {
+    GNUNET_array_append (p->peers, p->length, n->peer);
+    GNUNET_PEER_change_rc (n->peer, 1);
+    n = n->parent;
+    if (NULL == n)
+    {
+      GNUNET_break (0);
+      path_destroy (p);
+      return NULL;
+    }
+  }
+  GNUNET_array_append (p->peers, p->length, 1);
+  GNUNET_PEER_change_rc (1, 1);
+
+  path_invert (p);
+
+  return p;
+}
+
+
+
+/**
+ * Integrate a stand alone path into the tunnel tree.
+ * If the peer toward which the new path is already in the tree, the peer
+ * and its children will be maked as disconnected and the callback
+ * will be called on each one of them. They will be maked as online only after
+ * receiving a PATH ACK for the new path for each one of them, so the caller
+ * should take care of sending a new CREATE PATH message for each disconnected
+ * peer.
+ *
+ * @param t Tunnel where to add the new path.
+ * @param p Path to be integrated.
+ * @param cb Callback to use to notify about peers temporarily disconnecting.
+ * @param cbcls Closure for cb.
+ *
+ * @return GNUNET_OK in case of success.
+ *         GNUNET_SYSERR in case of error.
+ *
+ * TODO: optimize
+ * - go backwards on path looking for each peer in the present tree
+ * - do not disconnect peers until new path is created & connected
+ */
+int
+tree_add_path (struct MeshTunnelTree *t, const struct MeshPeerPath *p,
+               MeshTreeCallback cb, void *cbcls)
+{
+  struct MeshTunnelTreeNode *parent;
+  struct MeshTunnelTreeNode *oldnode;
+  struct MeshTunnelTreeNode *n;
+  struct MeshTunnelTreeNode *c;
+  struct GNUNET_PeerIdentity id;
+  int me;
+  unsigned int i;
+
+#if MESH_TREE_DEBUG
+  GNUNET_PEER_resolve (p->peers[p->length - 1], &id);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "tree:   Adding path [%u] towards peer %s.\n", p->length,
+              GNUNET_i2s (&id));
+#endif
+
+  GNUNET_assert (0 != p->length);
+  parent = n = t->root;
+  if (n->peer != p->peers[0])
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  if (1 == p->length)
+    return GNUNET_OK;
+  oldnode = tree_del_path (t, p->peers[p->length - 1], cb, cbcls);
+  /* Look for the first node that is not already present in the tree
+   *
+   * Assuming that the tree is somewhat balanced, O(log n * log N).
+   * - Length of the path is expected to be log N (size of whole network).
+   * - Each level of the tree is expected to have log n children (size of tree).
+   */
+  me = t->root->peer == 1 ? 0 : -1;
+  for (i = 1; i < p->length; i++)
+  {
+#if MESH_TREE_DEBUG
+    GNUNET_PEER_resolve (p->peers[i], &id);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Looking for peer %s.\n",
+                GNUNET_i2s (&id));
+#endif
+    parent = n;
+    if (p->peers[i] == 1)
+      me = i;
+    for (c = n->children_head; NULL != c; c = c->next)
+    {
+      if (c->peer == p->peers[i])
+      {
+#if MESH_TREE_DEBUG
+        GNUNET_PEER_resolve (parent->peer, &id);
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "tree:   Found in children of %s.\n", GNUNET_i2s (&id));
+#endif
+        n = c;
+        break;
+      }
+    }
+    /*  If we couldn't find a child equal to path[i], we have reached the end
+     * of the common path. */
+    if (parent == n)
+      break;
+  }
+#if MESH_TREE_DEBUG
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   All childen visited.\n");
+#endif
+  /* Add the rest of the path as a branch from parent. */
+  while (i < p->length)
+  {
+#if MESH_TREE_DEBUG
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Adding peer %u to %u.\n",
+                p->peers[i], parent->peer);
+    GNUNET_PEER_resolve (p->peers[i], &id);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Adding peer %s.\n",
+                GNUNET_i2s (&id));
+    GNUNET_PEER_resolve (parent->peer, &id);
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:     to %s.\n",
+                GNUNET_i2s (&id));
+#endif
+
+    if (i == p->length - 1 && NULL != oldnode)
+    {
+#if MESH_TREE_DEBUG
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "tree:   Putting old node into place.\n");
+#endif
+      oldnode->parent = parent;
+      GNUNET_CONTAINER_DLL_insert (parent->children_head, parent->children_tail,
+                                   oldnode);
+      tree_node_update_first_hops (t, oldnode, NULL);
+      n = oldnode;
+    }
+    else
+    {
+#if MESH_TREE_DEBUG
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   Creating new node.\n");
+#endif
+      n = tree_node_new (parent, p->peers[i]);
+      n->status = MESH_PEER_RELAY;
+      if (n->peer == 1)
+      {
+        t->me = n;
+        me = i;
+      }
+    }
+    i++;
+    parent = n;
+  }
+  n->status = MESH_PEER_SEARCHING;
+
+  GNUNET_break (-1 != me);
+
+  /* Add info about first hop into hashmap. */
+  if (-1 != me && me < p->length - 1)
+  {
+#if MESH_TREE_DEBUG
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "MESH:   finding first hop (own pos %d/%u)\n", me,
+                p->length - 1);
+#endif
+    GNUNET_PEER_resolve (p->peers[me + 1], &id);
+    tree_update_first_hops (t, p->peers[me + 1], &id);
+  }
+#if MESH_TREE_DEBUG
+  else
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "MESH:   was last in path, not updating first hops (%d/%u)\n",
+                me, p->length - 1);
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree:   New node added.\n");
+#endif
+  if (NULL == t->me)
+    t->me = tree_find_peer (t, 1);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Notifies a tree that a connection it might be using is broken.
+ * Marks all peers down the paths as disconnected and notifies the client.
+ *
+ * @param t Tree to use.
+ * @param p1 Short id of one of the peers (order unimportant)
+ * @param p2 Short id of one of the peers (order unimportant)
+ * @param cb Function to call for every peer that is marked as disconnected.
+ * @param cbcls Closure for cb.
+ *
+ * @return Short ID of the first disconnected peer in the tree.
+ */
+GNUNET_PEER_Id
+tree_notify_connection_broken (struct MeshTunnelTree *t, GNUNET_PEER_Id p1,
+                               GNUNET_PEER_Id p2, MeshTreeCallback cb,
+                               void *cbcls)
+{
+  struct MeshTunnelTreeNode *n;
+  struct MeshTunnelTreeNode *c;
+
+  n = tree_find_peer (t, p1);
+  if (NULL == n)
+    return 0;
+  if (NULL != n->parent && n->parent->peer == p2)
+  {
+    tree_mark_peers_disconnected (t, n, cb, cbcls);
+    GNUNET_CONTAINER_DLL_remove (n->parent->children_head,
+                                 n->parent->children_tail, n);
+    GNUNET_CONTAINER_DLL_insert (t->disconnected_head, t->disconnected_tail, n);
+    return p1;
+  }
+  for (c = n->children_head; NULL != c; c = c->next)
+  {
+    if (c->peer == p2)
+    {
+      tree_mark_peers_disconnected (t, c, cb, cbcls);
+      GNUNET_CONTAINER_DLL_remove (n->children_head, n->children_tail, c);
+      GNUNET_CONTAINER_DLL_insert (t->disconnected_head, t->disconnected_tail,
+                                   c);
+      return p2;
+    }
+  }
+  return 0;
+}
+
+
+/**
+ * Deletes a peer from a tunnel, liberating all unused resources on the path to
+ * it. It shouldn't have children, if it has they will be destroyed as well.
+ * If the tree is not local and no longer has any paths, the root node will be
+ * destroyed and marked as NULL.
+ *
+ * @param t Tunnel tree to use.
+ * @param peer Short ID of the peer to remove from the tunnel tree.
+ * @param cb Callback to notify client of disconnected peers.
+ * @param cbcls Closure for cb.
+ *
+ * @return GNUNET_OK or GNUNET_SYSERR
+ */
+int
+tree_del_peer (struct MeshTunnelTree *t, GNUNET_PEER_Id peer,
+               MeshTreeCallback cb, void *cbcls)
+{
+  struct MeshTunnelTreeNode *n;
+
+  n = tree_del_path (t, peer, cb, cbcls);
+  if (NULL == n)
+  {
+    GNUNET_break (0);
+    return GNUNET_YES;
+  }
+  GNUNET_break_op (NULL == n->children_head);
+  tree_node_destroy (n);
+  if (NULL == t->root->children_head && t->me != t->root)
+  {
+    tree_node_destroy (t->root);
+    t->root = NULL;
+    return GNUNET_NO;
+  }
+  return GNUNET_YES;
+}
+
+
+
+/**
+ * Get the cost of the path relative to the already built tunnel tree.
+ *
+ * @param t The tunnel tree to which compare.
+ * @param path The individual path to reach a peer. It has to start at the
+ *             root of the tree to be comparable.
+ *
+ * @return Number of hops to reach destination, UINT_MAX in case the peer is not
+ *         in the path.
+ *
+ * TODO: adapt to allow any start / root combination
+ * TODO: take in account state of the nodes
+ */
+unsigned int
+tree_get_path_cost (struct MeshTunnelTree *t, struct MeshPeerPath *path)
+{
+  struct MeshTunnelTreeNode *n;
+  struct MeshTunnelTreeNode *p;
+  unsigned int i;
+  unsigned int l;
+
+  l = path_get_length (path);
+  p = t->root;
+  if (t->root->peer != path->peers[0])
+  {
+    GNUNET_break (0);
+    return UINT_MAX;
+  }
+  for (i = 1; i < l; i++)
+  {
+    for (n = p->children_head; NULL != n; n = n->next)
+    {
+      if (path->peers[i] == n->peer)
+      {
+        break;
+      }
+    }
+    if (NULL == n)
+      return l - i;
+    p = n;
+  }
+  return l - i;
+}
+
+
+/**
+ * Print the tree on stderr
+ *
+ * @param t The tree
+ */
+void
+tree_debug (struct MeshTunnelTree *t)
+{
+  tree_node_debug (t->root, 0);
+}
+
+
+/**
+ * Iterator over hash map peer entries and frees all data in it.
+ * Used prior to destroying a hashmap. Makes you miss anonymous functions in C.
+ *
+ * @param cls closure
+ * @param key current key code (will no longer contain valid data!!)
+ * @param value value in the hash map (treated as void *)
+ * @return GNUNET_YES if we should continue to iterate, GNUNET_NO if not.
+ */
+static int
+iterate_free (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  GNUNET_free (value);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Destroy the whole tree and free all used memory and Peer_Ids
+ *
+ * @param t Tree to be destroyed
+ */
+void
+tree_destroy (struct MeshTunnelTree *t)
+{
+#if MESH_TREE_DEBUG
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "tree: Destroying tree\n");
+#endif
+  tree_node_destroy (t->root);
+  GNUNET_CONTAINER_multihashmap_iterate (t->first_hops, &iterate_free, NULL);
+  GNUNET_CONTAINER_multihashmap_destroy (t->first_hops);
+  GNUNET_free (t);
+}