/*
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 .
SPDX-License-Identifier: AGPL3.0-or-later
*/
/**
* @file cadet/gnunet-service-cadet_paths.c
* @brief Information we track per path.
* @author Bartlomiej Polot
* @author Christian Grothoff
*/
#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__)
/**
* Information regarding a possible path to reach a peer.
*/
struct CadetPeerPath
{
/**
* Array of all the peers on the path. If @e hn is non-NULL, the
* last one is our owner.
*/
struct CadetPeerPathEntry **entries;
/**
* Node of this path in the owner's heap. Used to update our position
* in the heap whenever our @e desirability changes.
*/
struct GNUNET_CONTAINER_HeapNode *hn;
/**
* Desirability of the path. How unique is it for the various peers
* on it?
*/
GNUNET_CONTAINER_HeapCostType desirability;
/**
* Length of the @e entries array.
*/
unsigned int entries_length;
};
/**
* Calculate the path's desirability score.
*
* @param path path to calculate the score for
*/
static void
recalculate_path_desirability (struct CadetPeerPath *path)
{
double result = 0.0;
for (unsigned int i=0;ientries_length;i++)
{
struct CadetPeer *cp = path->entries[i]->peer;
result += GCP_get_desirability_of_path (cp,
i);
}
path->desirability = (GNUNET_CONTAINER_HeapCostType) result;
}
/**
* Return how much we like keeping the path. This is an aggregate
* score based on various factors, including the age of the path
* (older == better), and the value of this path to all of its ajacent
* peers. For example, long paths that end at a peer that we have no
* shorter way to reach are very desirable, while long paths that end
* at a peer for which we have a shorter way as well are much less
* desirable. Higher values indicate more valuable paths. The
* returned value should be used to decide which paths to remember.
*
* @param path path to return the length for
* @return desirability of the path, larger is more desirable
*/
GNUNET_CONTAINER_HeapCostType
GCPP_get_desirability (const struct CadetPeerPath *path)
{
return path->desirability;
}
/**
* Return connection to @a destination using @a path, or return
* NULL if no such connection exists.
*
* @param path path to traverse
* @param destination destination node to get to, must be on path
* @param off offset of @a destination on @a path
* @return NULL if we have no existing connection
* otherwise connection from us to @a destination via @a path
*/
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;
}
/**
* Notify @a path that it is used for connection @a cc
* which ends at the path's offset @a off.
*
* @param path the path to remember the @a cc
* @param off the offset where the @a cc ends
* @param cc the connection to remember
*/
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;
}
/**
* Notify @a path that it is no longer used for connection @a cc which
* ended at the path's offset @a off.
*
* @param path the path to forget the @a cc
* @param off the offset where the @a cc ended
* @param cc the connection to forget
*/
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;
}
/**
* Tries to attach @a path to a peer, working backwards from the end
* and stopping at @a stop_at. If path->hn is NULL on return then the
* path was not attached and you can assume that path->entries_length
* is equal to @a stop_at.
*
* @param path the path to attach
* @param stop_at the path length at which to stop trying
*/
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);
}
/**
* The owning peer of this path is no longer interested in maintaining
* it, so the path should be discarded or shortened (in case a
* previous peer on the path finds the path desirable).
*
* @param path the path that is being released
*/
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);
}
}
/**
* Updates the score for an entry on the path based
* on our experiences with using @a path.
*
* @param path the path to update
* @param off offset of the entry to update
* @param delta change in the score to apply
*/
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);
}
/**
* Closure for #find_peer_at() and #check_match().
*/
struct CheckMatchContext
{
/**
* Set to a matching path, if any.
*/
struct CadetPeerPath *match;
/**
* Array the combined paths.
*/
struct CadetPeer **cpath;
/**
* How long is the @e cpath array?
*/
unsigned int cpath_length;
};
/**
* Check if the given path is identical on all of the
* hops until @a off, and not longer than @a off. If the
* @a path matches, store it in `match`.
*
* @param cls the `struct CheckMatchContext` to check against
* @param path the path to check
* @param off offset to check at
* @return #GNUNET_YES (continue to iterate), or if found #GNUNET_NO
*/
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;icpath[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! */
}
/**
* Extend path @a path by the @a num_peers from the @a peers
* array, assuming the owners past the current owner want it.
*
* @param path path to extend
* @param peers list of peers beyond the end of @a path
* @param num_peers length of the @a peers array
* @param force force attachment, even if we have other
* paths already
*/
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));
}
/**
* Create a peer path based on the result of a DHT lookup. If we
* already know this path, or one that is longer, simply return NULL.
* Otherwise, we try to extend an existing path, or create a new one
* if applicable.
*
* @param get_path path of the get request
* @param get_path_length lenght of @a get_path
* @param put_path path of the put request
* @param put_path_length length of the @a put_path
* @return a path through the network
*/
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)
{
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));
}
/**
* We got an incoming connection, obtain the corresponding path.
*
* @param path_length number of segments on the @a path
* @param pids path through the network, in reverse order (we are at the end at index @a path_length)
* @return corresponding path object
*/
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=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;
}
/**
* Return the length of the path. Excludes one end of the
* path, so the loopback path has length 0.
*
* @param path path to return the length for
* @return number of peers on the path
*/
unsigned int
GCPP_get_length (struct CadetPeerPath *path)
{
return path->entries_length;
}
/**
* Find peer's offset on path.
*
* @param path path to search
* @param cp peer to look for
* @return offset of @a cp on @a path, or UINT_MAX if not found
*/
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;
}
/**
* Obtain the peer at offset @a off in @a path.
*
* @param path peer path to inspect
* @param off offset to return, must be smaller than path length
* @return the peer at offset @a off
*/
struct CadetPeer *
GCPP_get_peer_at_offset (struct CadetPeerPath *path,
unsigned int off)
{
GNUNET_assert (off < path->entries_length);
return path->entries[off]->peer;
}
/**
* Convert a path to a human-readable string.
*
* @param path path to convert
* @return string, to be freed by caller (unlike other *_2s APIs!)
*/
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 */