gnunet-service-cadet_paths.c

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/*
     This file is part of GNUnet.
     Copyright (C) 2001-2017 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     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
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */
#include "platform.h"
#include "gnunet-service-cadet_connection.h"
#include "gnunet-service-cadet_tunnels.h"
#include "gnunet-service-cadet_peer.h"
#include "gnunet-service-cadet_paths.h"


#define LOG(level, ...) GNUNET_log_from(level, "cadet-pat", __VA_ARGS__)


struct CadetPeerPath {
  struct CadetPeerPathEntry **entries;

  struct GNUNET_CONTAINER_HeapNode *hn;

  GNUNET_CONTAINER_HeapCostType desirability;

  unsigned int entries_length;
};


static void
recalculate_path_desirability(struct CadetPeerPath *path)
{
  double result = 0.0;

  for (unsigned int i = 0; i < path->entries_length; i++)
    {
      struct CadetPeer *cp = path->entries[i]->peer;

      result += GCP_get_desirability_of_path(cp,
                                             i);
    }
  path->desirability = (GNUNET_CONTAINER_HeapCostType)result;
}


GNUNET_CONTAINER_HeapCostType
GCPP_get_desirability(const struct CadetPeerPath *path)
{
  return path->desirability;
}


struct CadetConnection *
GCPP_get_connection(struct CadetPeerPath *path,
                    struct CadetPeer *destination,
                    unsigned int off)
{
  struct CadetPeerPathEntry *entry;

  GNUNET_assert(off < path->entries_length);
  entry = path->entries[off];
  GNUNET_assert(entry->peer == destination);
  return entry->cc;
}


void
GCPP_add_connection(struct CadetPeerPath *path,
                    unsigned int off,
                    struct CadetConnection *cc)
{
  struct CadetPeerPathEntry *entry;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Adding %s to path %s at offset %u\n",
      GCC_2s(cc),
      GCPP_2s(path),
      off);
  GNUNET_assert(off < path->entries_length);
  entry = path->entries[off];
  GNUNET_assert(NULL == entry->cc);
  GNUNET_assert(NULL != cc);
  entry->cc = cc;
}



void
GCPP_del_connection(struct CadetPeerPath *path,
                    unsigned int off,
                    struct CadetConnection *cc)
{
  struct CadetPeerPathEntry *entry;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Removing connection %s to path %s at offset %u\n",
      GCC_2s(cc),
      GCPP_2s(path),
      off);
  GNUNET_assert(off < path->entries_length);
  entry = path->entries[off];
  GNUNET_assert(cc == entry->cc);
  entry->cc = NULL;
}


static void
attach_path(struct CadetPeerPath *path, unsigned int stop_at)
{
  GNUNET_assert(NULL == path->hn);

  /* Try to attach this path to a peer, working backwards from the end. */
  while (path->entries_length > stop_at)
    {
      unsigned int end = path->entries_length - 1;
      struct CadetPeerPathEntry *entry = path->entries[end];
      int force = GNUNET_NO;

      recalculate_path_desirability(path);
      /* If the entry already has a connection using it, force attach. */
      if (NULL != entry->cc)
        force = GNUNET_YES;
      path->hn = GCP_attach_path(entry->peer,
                                 path,
                                 end,
                                 force);
      if (NULL != path->hn)
        break;

      /* Attach failed, trim this entry from the path. */
      GNUNET_assert(NULL == entry->cc);
      GCP_path_entry_remove(entry->peer,
                            entry,
                            end);
      GNUNET_free(entry);
      path->entries[end] = NULL;
      path->entries_length--;
    }

  /* Shrink array to actual path length. */
  GNUNET_array_grow(path->entries,
                    path->entries_length,
                    path->entries_length);
}


void
GCPP_release(struct CadetPeerPath *path)
{
  struct CadetPeerPathEntry *entry;

  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Owner releases path %s\n",
      GCPP_2s(path));
  path->hn = NULL;
  entry = path->entries[path->entries_length - 1];
  GNUNET_assert(path == entry->path);
  GNUNET_assert(NULL == entry->cc);
  /* cut 'off' end of path */
  GCP_path_entry_remove(entry->peer,
                        entry,
                        path->entries_length - 1);
  GNUNET_free(entry);
  path->entries[path->entries_length - 1] = NULL;
  path->entries_length--;
  /* see if new peer at the end likes this path any better */
  attach_path(path, 0);
  if (NULL == path->hn)
    {
      /* nobody wants us, discard the path */
      GNUNET_assert(0 == path->entries_length);
      GNUNET_assert(NULL == path->entries);
      GNUNET_free(path);
    }
}


void
GCPP_update_score(struct CadetPeerPath *path,
                  unsigned int off,
                  int delta)
{
  struct CadetPeerPathEntry *entry;

  GNUNET_assert(off < path->entries_length);
  entry = path->entries[off];

  /* Add delta, with checks for overflows */
  if (delta >= 0)
    {
      if (delta + entry->score < entry->score)
        entry->score = INT_MAX;
      else
        entry->score += delta;
    }
  else
    {
      if (delta + entry->score > entry->score)
        entry->score = INT_MIN;
      else
        entry->score += delta;
    }
  recalculate_path_desirability(path);
}


struct CheckMatchContext {
  struct CadetPeerPath *match;

  struct CadetPeer **cpath;

  unsigned int cpath_length;
};


static int
check_match(void *cls,
            struct CadetPeerPath *path,
            unsigned int off)
{
  struct CheckMatchContext *cm_ctx = cls;

  GNUNET_assert(path->entries_length > off);
  if ((path->entries_length != off + 1) &&
      (off + 1 != cm_ctx->cpath_length))
    {
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "check_match mismatch because path %s is too long (%u vs. %u vs. %u)\n",
          GCPP_2s(path),
          path->entries_length,
          off + 1,
          cm_ctx->cpath_length);
      return GNUNET_YES; /* too long, goes somewhere else already, thus cannot be useful */
    }
  for (unsigned int i = 0; i < off; i++)
    if (cm_ctx->cpath[i] !=
        GCPP_get_peer_at_offset(path,
                                i))
      {
        LOG(GNUNET_ERROR_TYPE_DEBUG,
            "check_match path %s mismatches at offset %u\n",
            GCPP_2s(path),
            i);
        return GNUNET_YES; /* mismatch, ignore */
      }
  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "check_match found match with path %s\n",
      GCPP_2s(path));
  cm_ctx->match = path;
  return GNUNET_NO; /* match, we are done! */
}


static void
extend_path(struct CadetPeerPath *path,
            struct CadetPeer **peers,
            unsigned int num_peers,
            int force)
{
  unsigned int old_len = path->entries_length;
  int i;

  /* Expand path */
  GNUNET_array_grow(path->entries,
                    path->entries_length,
                    old_len + num_peers);
  for (i = num_peers - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = GNUNET_new(struct CadetPeerPathEntry);

      path->entries[old_len + i] = entry;
      entry->peer = peers[i];
      entry->path = path;
    }
  for (i = num_peers - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = path->entries[old_len + i];

      GCP_path_entry_add(entry->peer,
                         entry,
                         old_len + i);
    }

  /* If we extend an existing path, detach it from the
     old owner and re-attach to the new one */
  GCP_detach_path(path->entries[old_len - 1]->peer,
                  path,
                  path->hn);
  path->hn = NULL;
  path->entries_length = old_len + num_peers;
  if (GNUNET_YES == force)
    {
      int end = path->entries_length - 1;

      path->hn = GCP_attach_path(path->entries[end]->peer,
                                 path,
                                 end,
                                 GNUNET_YES);
    }
  else
    {
      attach_path(path, old_len);
    }
  if (NULL == path->hn)
    {
      /* none of the peers is interested in this path;
         re-attach. */
      GNUNET_assert(old_len == path->entries_length);
      path->hn = GCP_attach_path(path->entries[old_len - 1]->peer,
                                 path,
                                 old_len - 1,
                                 GNUNET_YES);
      GNUNET_assert(NULL != path->hn);
      return;
    }
  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Extended path %s\n",
      GCPP_2s(path));
}


void
GCPP_try_path_from_dht(const struct GNUNET_PeerIdentity *get_path,
                       unsigned int get_path_length,
                       const struct GNUNET_PeerIdentity *put_path,
                       unsigned int put_path_length)
{
  struct CadetPeer *cpath[get_path_length + put_path_length];
  struct CheckMatchContext cm_ctx;
  struct CadetPeerPath *path;
  unsigned int skip;
  unsigned int total_len;

  /* precompute 'cpath' so we can avoid doing the lookups lots of times */
  skip = 0;
  memset(cpath,
         0,
         sizeof(cpath));   /* Just to trigger harder errors later. */
  total_len = get_path_length + put_path_length;
  for (unsigned int off = 0; off < total_len; off++)
    {
      const struct GNUNET_PeerIdentity *pid;

      pid = (off < get_path_length)
            ? &get_path[get_path_length - off - 1]
            : &put_path[get_path_length + put_path_length - off - 1];
      /* Check that I am not in the path */
      if (0 == GNUNET_memcmp(&my_full_id,
                             pid))
        {
          skip = off + 1;
          continue;
        }
      cpath[off - skip] = GCP_get(pid,
                                  GNUNET_YES);
      /* Check that no peer is twice on the path */
      for (unsigned int i = 0; i < off - skip; i++)
        {
          if (cpath[i] == cpath[off - skip])
            {
              skip = off - i;
              break;
            }
        }
    }
  if (skip >= total_len)
    {
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Path discovered from DHT is one big cycle?\n");
      return;
    }
  total_len -= skip;

  /* First figure out if this path is a subset of an existing path, an
     extension of an existing path, or a new path. */
  cm_ctx.cpath_length = total_len;
  cm_ctx.cpath = cpath;
  cm_ctx.match = NULL;
  for (int i = total_len - 1; i >= 0; i--)
    {
      GCP_iterate_paths_at(cpath[i],
                           (unsigned int)i,
                           &check_match,
                           &cm_ctx);
      if (NULL != cm_ctx.match)
        {
          if (i == total_len - 1)
            {
              /* Existing path includes this one, nothing to do! */
              LOG(GNUNET_ERROR_TYPE_DEBUG,
                  "Path discovered from DHT is already known\n");
              return;
            }
          if (cm_ctx.match->entries_length == i + 1)
            {
              /* Existing path ends in the middle of new path, extend it! */
              LOG(GNUNET_ERROR_TYPE_DEBUG,
                  "Trying to extend existing path %s by additional links discovered from DHT\n",
                  GCPP_2s(cm_ctx.match));
              extend_path(cm_ctx.match,
                          &cpath[i + 1],
                          total_len - i - 1,
                          GNUNET_NO);
              return;
            }
        }
    }

  /* No match at all, create completely new path */
  path = GNUNET_new(struct CadetPeerPath);
  path->entries_length = total_len;
  path->entries = GNUNET_new_array(path->entries_length,
                                   struct CadetPeerPathEntry *);
  for (int i = path->entries_length - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = GNUNET_new(struct CadetPeerPathEntry);

      path->entries[i] = entry;
      entry->peer = cpath[i];
      entry->path = path;
    }
  for (int i = path->entries_length - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = path->entries[i];

      GCP_path_entry_add(entry->peer,
                         entry,
                         i);
    }

  /* Finally, try to attach it */
  attach_path(path, 0);
  if (NULL == path->hn)
    {
      /* None of the peers on the path care about it. */
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Path discovered from DHT is not interesting to us\n");
      GNUNET_assert(0 == path->entries_length);
      GNUNET_assert(NULL == path->entries);
      GNUNET_free(path);
      return;
    }
  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Created new path %s based on information from DHT\n",
      GCPP_2s(path));
}


struct CadetPeerPath *
GCPP_get_path_from_route(unsigned int path_length,
                         const struct GNUNET_PeerIdentity *pids)
{
  struct CheckMatchContext cm_ctx;
  struct CadetPeer *cpath[path_length];
  struct CadetPeerPath *path;

  /* precompute inverted 'cpath' so we can avoid doing the lookups and
     have the correct order */
  for (unsigned int off = 0; off < path_length; off++)
    cpath[off] = GCP_get(&pids[path_length - 1 - off],
                         GNUNET_YES);

  /* First figure out if this path is a subset of an existing path, an
     extension of an existing path, or a new path. */
  cm_ctx.cpath = cpath;
  cm_ctx.cpath_length = path_length;
  cm_ctx.match = NULL;
  for (int i = path_length - 1; i >= 0; i--)
    {
      GCP_iterate_paths_at(cpath[i],
                           (unsigned int)i,
                           &check_match,
                           &cm_ctx);
      if (NULL != cm_ctx.match)
        {
          if (i == path_length - 1)
            {
              /* Existing path includes this one, return the match! */
              LOG(GNUNET_ERROR_TYPE_DEBUG,
                  "Returning existing path %s as inverse for incoming connection\n",
                  GCPP_2s(cm_ctx.match));
              return cm_ctx.match;
            }
          if (cm_ctx.match->entries_length == i + 1)
            {
              /* Existing path ends in the middle of new path, extend it! */
              LOG(GNUNET_ERROR_TYPE_DEBUG,
                  "Extending existing path %s to create inverse for incoming connection\n",
                  GCPP_2s(cm_ctx.match));
              extend_path(cm_ctx.match,
                          &cpath[i + 1],
                          path_length - i - 1,
                          GNUNET_YES);
              /* Check that extension was successful */
              GNUNET_assert(cm_ctx.match->entries_length == path_length);
              return cm_ctx.match;
            }
          /* Eh, we found a match but couldn't use it? Something is wrong. */
          GNUNET_break(0);
        }
    }

  /* No match at all, create completely new path */
  path = GNUNET_new(struct CadetPeerPath);
  path->entries_length = path_length;
  path->entries = GNUNET_new_array(path->entries_length,
                                   struct CadetPeerPathEntry *);
  for (int i = path_length - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = GNUNET_new(struct CadetPeerPathEntry);

      path->entries[i] = entry;
      entry->peer = cpath[i];
      entry->path = path;
    }
  for (int i = path_length - 1; i >= 0; i--)
    {
      struct CadetPeerPathEntry *entry = path->entries[i];

      GCP_path_entry_add(entry->peer,
                         entry,
                         i);
    }
  recalculate_path_desirability(path);
  LOG(GNUNET_ERROR_TYPE_DEBUG,
      "Created new path %s to create inverse for incoming connection\n",
      GCPP_2s(path));
  path->hn = GCP_attach_path(cpath[path_length - 1],
                             path,
                             path_length - 1,
                             GNUNET_YES);
  return path;
}


unsigned int
GCPP_get_length(struct CadetPeerPath *path)
{
  return path->entries_length;
}


unsigned int
GCPP_find_peer(struct CadetPeerPath *path,
               struct CadetPeer *cp)
{
  for (unsigned int off = 0;
       off < path->entries_length;
       off++)
    if (cp == GCPP_get_peer_at_offset(path,
                                      off))
      return off;
  return UINT_MAX;
}


struct CadetPeer *
GCPP_get_peer_at_offset(struct CadetPeerPath *path,
                        unsigned int off)
{
  GNUNET_assert(off < path->entries_length);
  return path->entries[off]->peer;
}


const char *
GCPP_2s(struct CadetPeerPath *path)
{
  static char buf[2048];
  size_t off;
  const unsigned int max_plen = (sizeof(buf) - 16) / 5 - 2; /* 5 characters per entry */

  off = 0;
  for (unsigned int i = 0;
       i < path->entries_length;
       i++)
    {
      if ((path->entries_length > max_plen) &&
          (i == max_plen / 2))
        off += GNUNET_snprintf(&buf[off],
                               sizeof(buf) - off,
                               "...-");
      if ((path->entries_length > max_plen) &&
          (i > max_plen / 2) &&
          (i < path->entries_length - max_plen / 2))
        continue;
      off += GNUNET_snprintf(&buf[off],
                             sizeof(buf) - off,
                             "%s%s",
                             GNUNET_i2s(GCP_get_id(GCPP_get_peer_at_offset(path,
                                                                           i))),
                             (i == path->entries_length - 1) ? "" : "-");
    }
  GNUNET_snprintf(&buf[off],
                  sizeof(buf) - off,
                  "(%p)",
                  path);
  return buf;
}


/* end of gnunet-service-cadet-new_paths.c */