Imported Upstream version 0.9.2upstream/0.9.2

1 files changed, 1276 insertions, 0 deletions

diff --git a/src/transport/gnunet-service-transport_validation.c b/src/transport/gnunet-service-transport_validation.c
new file mode 100644
index 0000000..a6d9424
--- /dev/null
+++ b/src/transport/gnunet-service-transport_validation.c
@@ -0,0 +1,1276 @@
+/*
+     This file is part of GNUnet.
+     (C) 2010,2011 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 transport/gnunet-service-transport_validation.c
+ * @brief address validation subsystem
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "gnunet-service-transport_validation.h"
+#include "gnunet-service-transport_plugins.h"
+#include "gnunet-service-transport_hello.h"
+#include "gnunet-service-transport_blacklist.h"
+#include "gnunet-service-transport.h"
+#include "gnunet_hello_lib.h"
+#include "gnunet_ats_service.h"
+#include "gnunet_peerinfo_service.h"
+#include "gnunet_signatures.h"
+
+
+/**
+ * How long is a PONG signature valid?  We'll recycle a signature until
+ * 1/4 of this time is remaining.  PONGs should expire so that if our
+ * external addresses change an adversary cannot replay them indefinitely.
+ * OTOH, we don't want to spend too much time generating PONG signatures,
+ * so they must have some lifetime to reduce our CPU usage.
+ */
+#define PONG_SIGNATURE_LIFETIME GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 1)
+
+/**
+ * After how long do we expire an address in a HELLO that we just
+ * validated?  This value is also used for our own addresses when we
+ * create a HELLO.
+ */
+#define HELLO_ADDRESS_EXPIRATION GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_HOURS, 12)
+
+/**
+ * How often do we allow PINGing an address that we have not yet
+ * validated?  This also determines how long we track an address that
+ * we cannot validate (because after this time we can destroy the
+ * validation record).
+ */
+#define UNVALIDATED_PING_KEEPALIVE GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 5)
+
+/**
+ * How often do we PING an address that we have successfully validated
+ * in the past but are not actively using?  Should be (significantly)
+ * smaller than HELLO_ADDRESS_EXPIRATION.
+ */
+#define VALIDATED_PING_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 15)
+
+/**
+ * How often do we PING an address that we are currently using?
+ */
+#define CONNECTED_PING_FREQUENCY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MINUTES, 2)
+
+/**
+ * How much delay is acceptable for sending the PING or PONG?
+ */
+#define ACCEPTABLE_PING_DELAY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 1)
+
+/**
+ * Size of the validation map hashmap.
+ */
+#define VALIDATION_MAP_SIZE 256
+
+/**
+ * Priority to use for PINGs
+ */
+#define PING_PRIORITY 2
+
+/**
+ * Priority to use for PONGs
+ */
+#define PONG_PRIORITY 4
+
+
+GNUNET_NETWORK_STRUCT_BEGIN
+
+/**
+ * Message used to ask a peer to validate receipt (to check an address
+ * from a HELLO).  Followed by the address we are trying to validate,
+ * or an empty address if we are just sending a PING to confirm that a
+ * connection which the receiver (of the PING) initiated is still valid.
+ */
+struct TransportPingMessage
+{
+
+  /**
+   * Type will be GNUNET_MESSAGE_TYPE_TRANSPORT_PING
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Challenge code (to ensure fresh reply).
+   */
+  uint32_t challenge GNUNET_PACKED;
+
+  /**
+   * Who is the intended recipient?
+   */
+  struct GNUNET_PeerIdentity target;
+
+};
+
+
+/**
+ * Message used to validate a HELLO.  The challenge is included in the
+ * confirmation to make matching of replies to requests possible.  The
+ * signature signs our public key, an expiration time and our address.<p>
+ *
+ * This message is followed by our transport address that the PING tried
+ * to confirm (if we liked it).  The address can be empty (zero bytes)
+ * if the PING had not address either (and we received the request via
+ * a connection that we initiated).
+ */
+struct TransportPongMessage
+{
+
+  /**
+   * Type will be GNUNET_MESSAGE_TYPE_TRANSPORT_PONG
+   */
+  struct GNUNET_MessageHeader header;
+
+  /**
+   * Challenge code from PING (showing freshness).  Not part of what
+   * is signed so that we can re-use signatures.
+   */
+  uint32_t challenge GNUNET_PACKED;
+
+  /**
+   * Signature.
+   */
+  struct GNUNET_CRYPTO_RsaSignature signature;
+
+  /**
+   * GNUNET_SIGNATURE_PURPOSE_TRANSPORT_PONG_OWN to confirm that this is a
+   * plausible address for the signing peer.
+   */
+  struct GNUNET_CRYPTO_RsaSignaturePurpose purpose;
+
+  /**
+   * When does this signature expire?
+   */
+  struct GNUNET_TIME_AbsoluteNBO expiration;
+
+  /**
+   * Size of address appended to this message (part of what is
+   * being signed, hence not redundant).
+   */
+  uint32_t addrlen GNUNET_PACKED;
+
+};
+GNUNET_NETWORK_STRUCT_END
+
+/**
+ * Information about an address under validation
+ */
+struct ValidationEntry
+{
+
+  /**
+   * The address.
+   */
+  struct GNUNET_HELLO_Address *address;
+
+  /**
+   * Handle to the blacklist check (if we're currently in it).
+   */
+  struct GST_BlacklistCheck *bc;
+
+  /**
+   * Public key of the peer.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+  /**
+   * The identity of the peer. FIXME: duplicated (also in 'address')
+   */
+  struct GNUNET_PeerIdentity pid;
+
+  /**
+   * ID of task that will clean up this entry if nothing happens.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier timeout_task;
+
+  /**
+   * ID of task that will trigger address revalidation.
+   */
+  GNUNET_SCHEDULER_TaskIdentifier revalidation_task;
+
+  /**
+   * At what time did we send the latest validation request (PING)?
+   */
+  struct GNUNET_TIME_Absolute send_time;
+
+  /**
+   * Until when is this address valid?
+   * ZERO if it is not currently considered valid.
+   */
+  struct GNUNET_TIME_Absolute valid_until;
+
+  /**
+   * How long until we can try to validate this address again?
+   * FOREVER if the address is for an unsupported plugin (from PEERINFO)
+   * ZERO if the address is considered valid (no validation needed)
+   * otherwise a time in the future if we're currently denying re-validation
+   */
+  struct GNUNET_TIME_Absolute revalidation_block;
+
+  /**
+   * Last observed latency for this address (round-trip), delay between
+   * last PING sent and PONG received; FOREVER if we never got a PONG.
+   */
+  struct GNUNET_TIME_Relative latency;
+
+  /**
+   * Challenge number we used.
+   */
+  uint32_t challenge;
+
+  /**
+   * When passing the address in 'add_valid_peer_address', did we
+   * copy the address to the HELLO yet?
+   */
+  int copied;
+
+  /**
+   * Are we currently using this address for a connection?
+   */
+  int in_use;
+
+  /**
+   * Are we expecting a PONG message for this validation entry?
+   */
+  int expecting_pong;
+};
+
+
+/**
+ * Context of currently active requests to peerinfo
+ * for validation of HELLOs.
+ */
+struct CheckHelloValidatedContext
+{
+
+  /**
+   * This is a doubly-linked list.
+   */
+  struct CheckHelloValidatedContext *next;
+
+  /**
+   * This is a doubly-linked list.
+   */
+  struct CheckHelloValidatedContext *prev;
+
+  /**
+   * Hello that we are validating.
+   */
+  const struct GNUNET_HELLO_Message *hello;
+
+};
+
+
+/**
+ * Head of linked list of HELLOs awaiting validation.
+ */
+static struct CheckHelloValidatedContext *chvc_head;
+
+/**
+ * Tail of linked list of HELLOs awaiting validation
+ */
+static struct CheckHelloValidatedContext *chvc_tail;
+
+/**
+ * Map of PeerIdentities to 'struct ValidationEntry*'s (addresses
+ * of the given peer that we are currently validating, have validated
+ * or are blocked from re-validation for a while).
+ */
+static struct GNUNET_CONTAINER_MultiHashMap *validation_map;
+
+/**
+ * Context for peerinfo iteration.
+ */
+static struct GNUNET_PEERINFO_NotifyContext *pnc;
+
+
+/**
+ * Context for the validation entry match function.
+ */
+struct ValidationEntryMatchContext
+{
+  /**
+   * Where to store the result?
+   */
+  struct ValidationEntry *ve;
+
+  /**
+   * Address we're interested in.
+   */
+  const struct GNUNET_HELLO_Address *address;
+
+};
+
+
+/**
+ * Iterate over validation entries until a matching one is found.
+ *
+ * @param cls the 'struct ValidationEntryMatchContext'
+ * @param key peer identity (unused)
+ * @param value a 'struct ValidationEntry' to match
+ * @return GNUNET_YES if the entry does not match,
+ *         GNUNET_NO if the entry does match
+ */
+static int
+validation_entry_match (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct ValidationEntryMatchContext *vemc = cls;
+  struct ValidationEntry *ve = value;
+
+  if (0 == GNUNET_HELLO_address_cmp (ve->address, vemc->address))
+  {
+    vemc->ve = ve;
+    return GNUNET_NO;
+  }
+  return GNUNET_YES;
+}
+
+
+/**
+ * Iterate over validation entries and free them.
+ *
+ * @param cls (unused)
+ * @param key peer identity (unused)
+ * @param value a 'struct ValidationEntry' to clean up
+ * @return GNUNET_YES (continue to iterate)
+ */
+static int
+cleanup_validation_entry (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct ValidationEntry *ve = value;
+
+  if (NULL != ve->bc)
+  {
+    GST_blacklist_test_cancel (ve->bc);
+    ve->bc = NULL;
+  }
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_remove (validation_map,
+                                                      &ve->pid.hashPubKey, ve));
+  GNUNET_HELLO_address_free (ve->address);
+  if (GNUNET_SCHEDULER_NO_TASK != ve->timeout_task)
+  {
+    GNUNET_SCHEDULER_cancel (ve->timeout_task);
+    ve->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  if (GNUNET_SCHEDULER_NO_TASK != ve->revalidation_task)
+  {
+    GNUNET_SCHEDULER_cancel (ve->revalidation_task);
+    ve->revalidation_task = GNUNET_SCHEDULER_NO_TASK;
+  }
+  GNUNET_free (ve);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Address validation cleanup task.  Assesses if the record is no
+ * longer valid and then possibly triggers its removal.
+ *
+ * @param cls the 'struct ValidationEntry'
+ * @param tc scheduler context (unused)
+ */
+static void
+timeout_hello_validation (void *cls,
+                          const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct ValidationEntry *ve = cls;
+  struct GNUNET_TIME_Absolute max;
+  struct GNUNET_TIME_Relative left;
+
+  ve->timeout_task = GNUNET_SCHEDULER_NO_TASK;
+  max = GNUNET_TIME_absolute_max (ve->valid_until, ve->revalidation_block);
+  left = GNUNET_TIME_absolute_get_remaining (max);
+  if (left.rel_value > 0)
+  {
+    /* should wait a bit longer */
+    ve->timeout_task =
+        GNUNET_SCHEDULER_add_delayed (left, &timeout_hello_validation, ve);
+    return;
+  }
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# address records discarded"), 1,
+                            GNUNET_NO);
+  cleanup_validation_entry (NULL, &ve->pid.hashPubKey, ve);
+}
+
+
+/**
+ * Function called with the result from blacklisting.
+ * Send a PING to the other peer if a communication is allowed.
+ *
+ * @param cls our 'struct ValidationEntry'
+ * @param pid identity of the other peer
+ * @param result GNUNET_OK if the connection is allowed, GNUNET_NO if not
+ */
+static void
+transmit_ping_if_allowed (void *cls, const struct GNUNET_PeerIdentity *pid,
+                          int result)
+{
+  struct ValidationEntry *ve = cls;
+  struct TransportPingMessage ping;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+  const struct GNUNET_MessageHeader *hello;
+  ssize_t ret;
+  size_t tsize;
+  size_t slen;
+  uint16_t hsize;
+
+  ve->bc = NULL;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Transmitting plain PING to `%s' %s\n",
+              GNUNET_i2s (pid), GST_plugins_a2s (ve->address));
+
+  slen = strlen (ve->address->transport_name) + 1;
+  hello = GST_hello_get ();
+  hsize = ntohs (hello->size);
+  tsize =
+      sizeof (struct TransportPingMessage) + ve->address->address_length +
+      slen + hsize;
+
+  ping.header.size =
+      htons (sizeof (struct TransportPingMessage) +
+             ve->address->address_length + slen);
+  ping.header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_PING);
+  ping.challenge = htonl (ve->challenge);
+  ping.target = *pid;
+
+  if (tsize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _
+                ("Not transmitting `%s' with `%s', message too big (%u bytes!). This should not happen.\n"),
+                "HELLO", "PING", (unsigned int) tsize);
+    /* message too big (!?), get rid of HELLO */
+    hsize = 0;
+    tsize =
+        sizeof (struct TransportPingMessage) + ve->address->address_length +
+        slen + hsize;
+  }
+  {
+    char message_buf[tsize];
+
+    /* build message with structure:
+     *  [HELLO][TransportPingMessage][Transport name][Address] */
+    memcpy (message_buf, hello, hsize);
+    memcpy (&message_buf[hsize], &ping, sizeof (struct TransportPingMessage));
+    memcpy (&message_buf[sizeof (struct TransportPingMessage) + hsize],
+            ve->address->transport_name, slen);
+    memcpy (&message_buf[sizeof (struct TransportPingMessage) + slen + hsize],
+            ve->address, ve->address->address_length);
+    papi = GST_plugins_find (ve->address->transport_name);
+    if (papi == NULL)
+      ret = -1;
+    else
+    {
+      GNUNET_assert (papi->send != NULL);
+      GNUNET_assert (papi->get_session != NULL);
+      struct Session * session = papi->get_session(papi->cls, ve->address);
+
+      if (session != NULL)
+      {
+        ret = papi->send (papi->cls, session,
+                          message_buf, tsize,
+                          PING_PRIORITY, ACCEPTABLE_PING_DELAY,
+                          NULL, NULL);
+      }
+      else
+      {
+        /* Could not get a valid session */
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Could not get a valid session for `%s' %s\n",
+                    GNUNET_i2s (pid), GST_plugins_a2s (ve->address));
+        ret = -1;
+      }
+    }
+  }
+  if (-1 != ret)
+  {
+    ve->send_time = GNUNET_TIME_absolute_get ();
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# PING without HELLO messages sent"), 1,
+                              GNUNET_NO);
+    ve->expecting_pong = GNUNET_YES;
+  }
+}
+
+
+/**
+ * Do address validation again to keep address valid.
+ *
+ * @param cls the 'struct ValidationEntry'
+ * @param tc scheduler context (unused)
+ */
+static void
+revalidate_address (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
+{
+  struct ValidationEntry *ve = cls;
+  struct GNUNET_TIME_Relative canonical_delay;
+  struct GNUNET_TIME_Relative delay;
+  struct GST_BlacklistCheck *bc;
+  uint32_t rdelay;
+
+  ve->revalidation_task = GNUNET_SCHEDULER_NO_TASK;
+  delay = GNUNET_TIME_absolute_get_remaining (ve->revalidation_block);
+  /* How long until we can possibly permit the next PING? */
+  canonical_delay =
+      (ve->in_use ==
+       GNUNET_YES) ? CONNECTED_PING_FREQUENCY
+      : ((GNUNET_TIME_absolute_get_remaining (ve->valid_until).rel_value >
+          0) ? VALIDATED_PING_FREQUENCY : UNVALIDATED_PING_KEEPALIVE);
+  if (delay.rel_value > canonical_delay.rel_value * 2)
+  {
+    /* situation changed, recalculate delay */
+    delay = canonical_delay;
+    ve->revalidation_block = GNUNET_TIME_relative_to_absolute (delay);
+  }
+  if (delay.rel_value > 0)
+  {
+    /* should wait a bit longer */
+    ve->revalidation_task =
+        GNUNET_SCHEDULER_add_delayed (delay, &revalidate_address, ve);
+    return;
+  }
+  ve->revalidation_block = GNUNET_TIME_relative_to_absolute (canonical_delay);
+
+  /* schedule next PINGing with some extra random delay to avoid synchronous re-validations */
+  rdelay =
+      GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
+                                canonical_delay.rel_value);
+  delay =
+      GNUNET_TIME_relative_add (canonical_delay,
+                                GNUNET_TIME_relative_multiply
+                                (GNUNET_TIME_UNIT_MILLISECONDS, rdelay));
+  ve->revalidation_task =
+      GNUNET_SCHEDULER_add_delayed (delay, &revalidate_address, ve);
+
+  /* start PINGing by checking blacklist */
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# address revalidations started"), 1,
+                            GNUNET_NO);
+  bc = GST_blacklist_test_allowed (&ve->pid, ve->address->transport_name,
+                                   &transmit_ping_if_allowed, ve);
+  if (NULL != bc)
+    ve->bc = bc;                /* only set 'bc' if 'transmit_ping_if_allowed' was not already
+                                 * called... */
+}
+
+
+/**
+ * Find a ValidationEntry entry for the given neighbour that matches
+ * the given address and transport.  If none exists, create one (but
+ * without starting any validation).
+ *
+ * @param public_key public key of the peer, NULL for unknown
+ * @param address address to find
+ * @return validation entry matching the given specifications, NULL
+ *         if we don't have an existing entry and no public key was given
+ */
+static struct ValidationEntry *
+find_validation_entry (const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded
+                       *public_key, const struct GNUNET_HELLO_Address *address)
+{
+  struct ValidationEntryMatchContext vemc;
+  struct ValidationEntry *ve;
+
+  vemc.ve = NULL;
+  vemc.address = address;
+  GNUNET_CONTAINER_multihashmap_get_multiple (validation_map,
+                                              &address->peer.hashPubKey,
+                                              &validation_entry_match, &vemc);
+  if (NULL != (ve = vemc.ve))
+    return ve;
+  if (public_key == NULL)
+    return NULL;
+  ve = GNUNET_malloc (sizeof (struct ValidationEntry));
+  ve->address = GNUNET_HELLO_address_copy (address);
+  ve->public_key = *public_key;
+  ve->pid = address->peer;
+  ve->latency = GNUNET_TIME_UNIT_FOREVER_REL;
+  ve->challenge =
+      GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE, UINT32_MAX);
+  ve->timeout_task =
+      GNUNET_SCHEDULER_add_delayed (UNVALIDATED_PING_KEEPALIVE,
+                                    &timeout_hello_validation, ve);
+  GNUNET_CONTAINER_multihashmap_put (validation_map, &address->peer.hashPubKey,
+                                     ve,
+                                     GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
+  ve->expecting_pong = GNUNET_NO;
+  return ve;
+}
+
+
+/**
+ * Iterator which adds the given address to the set of validated
+ * addresses.
+ *
+ * @param cls original HELLO message
+ * @param address the address
+ * @param expiration expiration time
+ * @return GNUNET_OK (keep the address)
+ */
+static int
+add_valid_address (void *cls, const struct GNUNET_HELLO_Address *address,
+                   struct GNUNET_TIME_Absolute expiration)
+{
+  const struct GNUNET_HELLO_Message *hello = cls;
+  struct ValidationEntry *ve;
+  struct GNUNET_PeerIdentity pid;
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+
+  if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value == 0)
+    return GNUNET_OK;           /* expired */
+  if ((GNUNET_OK != GNUNET_HELLO_get_id (hello, &pid)) ||
+      (GNUNET_OK != GNUNET_HELLO_get_key (hello, &public_key)))
+  {
+    GNUNET_break (0);
+    return GNUNET_OK;           /* invalid HELLO !? */
+  }
+  if (0 == memcmp (&GST_my_identity, &pid, sizeof (struct GNUNET_PeerIdentity)))
+  {
+    /* Peerinfo returned own identity, skip validation */
+    return GNUNET_OK;
+  }
+
+  ve = find_validation_entry (&public_key, address);
+  ve->valid_until = GNUNET_TIME_absolute_max (ve->valid_until, expiration);
+
+  if (GNUNET_SCHEDULER_NO_TASK == ve->revalidation_task)
+    ve->revalidation_task = GNUNET_SCHEDULER_add_now (&revalidate_address, ve);
+  GNUNET_ATS_address_update (GST_ats, address, NULL, NULL, 0);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Function called for any HELLO known to PEERINFO.
+ *
+ * @param cls unused
+ * @param peer id of the peer, NULL for last call
+ * @param hello hello message for the peer (can be NULL)
+ * @param err_msg error message
+ */
+static void
+process_peerinfo_hello (void *cls, const struct GNUNET_PeerIdentity *peer,
+                        const struct GNUNET_HELLO_Message *hello,
+                        const char *err_msg)
+{
+  GNUNET_assert (NULL != peer);
+  if (NULL == hello)
+    return;
+  GNUNET_assert (NULL ==
+                 GNUNET_HELLO_iterate_addresses (hello, GNUNET_NO,
+                                                 &add_valid_address,
+                                                 (void *) hello));
+}
+
+
+/**
+ * Start the validation subsystem.
+ */
+void
+GST_validation_start ()
+{
+  validation_map = GNUNET_CONTAINER_multihashmap_create (VALIDATION_MAP_SIZE);
+  pnc = GNUNET_PEERINFO_notify (GST_cfg, &process_peerinfo_hello, NULL);
+}
+
+
+/**
+ * Stop the validation subsystem.
+ */
+void
+GST_validation_stop ()
+{
+  struct CheckHelloValidatedContext *chvc;
+
+  GNUNET_CONTAINER_multihashmap_iterate (validation_map,
+                                         &cleanup_validation_entry, NULL);
+  GNUNET_CONTAINER_multihashmap_destroy (validation_map);
+  validation_map = NULL;
+  while (NULL != (chvc = chvc_head))
+  {
+    GNUNET_CONTAINER_DLL_remove (chvc_head, chvc_tail, chvc);
+    GNUNET_free (chvc);
+  }
+  GNUNET_PEERINFO_notify_cancel (pnc);
+}
+
+
+/**
+ * Send the given PONG to the given address.
+ *
+ * @param cls the PONG message
+ * @param public_key public key for the peer, never NULL
+ * @param valid_until is ZERO if we never validated the address,
+ *                    otherwise a time up to when we consider it (or was) valid
+ * @param validation_block  is FOREVER if the address is for an unsupported plugin (from PEERINFO)
+ *                          is ZERO if the address is considered valid (no validation needed)
+ *                          otherwise a time in the future if we're currently denying re-validation
+ * @param address target address
+ */
+static void
+multicast_pong (void *cls,
+                const struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded
+                *public_key, struct GNUNET_TIME_Absolute valid_until,
+                struct GNUNET_TIME_Absolute validation_block,
+                const struct GNUNET_HELLO_Address *address)
+{
+  struct TransportPongMessage *pong = cls;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+
+  papi = GST_plugins_find (address->transport_name);
+  if (papi == NULL)
+    return;
+
+  GNUNET_assert (papi->send != NULL);
+  GNUNET_assert (papi->get_session != NULL);
+
+  struct Session * session = papi->get_session(papi->cls, address);
+  if (session == NULL)
+  {
+     GNUNET_break (0);
+     return;
+  }
+
+  papi->send (papi->cls, session,
+              (const char *) pong, ntohs (pong->header.size),
+              PONG_PRIORITY, ACCEPTABLE_PING_DELAY,
+              NULL, NULL);
+}
+
+
+/**
+ * We've received a PING.  If appropriate, generate a PONG.
+ *
+ * @param sender peer sending the PING
+ * @param hdr the PING
+ * @param sender_address the sender address as we got it
+ * @param session session we got the PING from
+ */
+void
+GST_validation_handle_ping (const struct GNUNET_PeerIdentity *sender,
+                            const struct GNUNET_MessageHeader *hdr,
+                            const struct GNUNET_HELLO_Address *sender_address,
+                            struct Session *session)
+{
+  const struct TransportPingMessage *ping;
+  struct TransportPongMessage *pong;
+  struct GNUNET_TRANSPORT_PluginFunctions *papi;
+  struct GNUNET_CRYPTO_RsaSignature *sig_cache;
+  struct GNUNET_TIME_Absolute *sig_cache_exp;
+  const char *addr;
+  const char *addrend;
+  size_t alen;
+  size_t slen;
+  ssize_t ret;
+  struct GNUNET_HELLO_Address address;
+
+  if (ntohs (hdr->size) < sizeof (struct TransportPingMessage))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  ping = (const struct TransportPingMessage *) hdr;
+  if (0 !=
+      memcmp (&ping->target, &GST_my_identity,
+              sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# PING message for different peer received"), 1,
+                              GNUNET_NO);
+    return;
+  }
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# PING messages received"), 1,
+                            GNUNET_NO);
+  addr = (const char *) &ping[1];
+  alen = ntohs (hdr->size) - sizeof (struct TransportPingMessage);
+  /* peer wants to confirm that this is one of our addresses, this is what is
+   * used for address validation */
+
+  sig_cache = NULL;
+  sig_cache_exp = NULL;
+
+  if (0 < alen)
+  {
+    addrend = memchr (addr, '\0', alen);
+    if (NULL == addrend)
+    {
+      GNUNET_break_op (0);
+      return;
+    }
+    addrend++;
+    slen = strlen (addr) + 1;
+    alen -= slen;
+    address.address = addrend;
+    address.address_length = alen;
+    address.transport_name = addr;
+    address.peer = *sender;
+    if (GNUNET_YES !=
+        GST_hello_test_address (&address, &sig_cache, &sig_cache_exp))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                  _
+                  ("Not confirming PING with address `%s' since I cannot confirm having this address.\n"),
+                  GST_plugins_a2s (&address));
+      return;
+    }
+  }
+  else
+  {
+    addrend = NULL;             /* make gcc happy */
+    slen = 0;
+    static struct GNUNET_CRYPTO_RsaSignature no_address_signature;
+    static struct GNUNET_TIME_Absolute no_address_signature_expiration;
+
+    sig_cache = &no_address_signature;
+    sig_cache_exp = &no_address_signature_expiration;
+  }
+
+  pong = GNUNET_malloc (sizeof (struct TransportPongMessage) + alen + slen);
+  pong->header.size =
+      htons (sizeof (struct TransportPongMessage) + alen + slen);
+  pong->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_PONG);
+  pong->purpose.size =
+      htonl (sizeof (struct GNUNET_CRYPTO_RsaSignaturePurpose) +
+             sizeof (uint32_t) + sizeof (struct GNUNET_TIME_AbsoluteNBO) +
+             alen + slen);
+  pong->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_TRANSPORT_PONG_OWN);
+  pong->challenge = ping->challenge;
+  pong->addrlen = htonl (alen + slen);
+  memcpy (&pong[1], addr, slen);
+  memcpy (&((char *) &pong[1])[slen], addrend, alen);
+  if (GNUNET_TIME_absolute_get_remaining (*sig_cache_exp).rel_value <
+      PONG_SIGNATURE_LIFETIME.rel_value / 4)
+  {
+    /* create / update cached sig */
+#if DEBUG_TRANSPORT
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Creating PONG signature to indicate ownership.\n");
+#endif
+    *sig_cache_exp = GNUNET_TIME_relative_to_absolute (PONG_SIGNATURE_LIFETIME);
+    pong->expiration = GNUNET_TIME_absolute_hton (*sig_cache_exp);
+    GNUNET_assert (GNUNET_OK ==
+                   GNUNET_CRYPTO_rsa_sign (GST_my_private_key, &pong->purpose,
+                                           sig_cache));
+  }
+  else
+  {
+    pong->expiration = GNUNET_TIME_absolute_hton (*sig_cache_exp);
+  }
+  pong->signature = *sig_cache;
+
+  GNUNET_assert (sender_address != NULL);
+
+  /* first see if the session we got this PING from can be used to transmit
+   * a response reliably */
+  papi = GST_plugins_find (sender_address->transport_name);
+  if (papi == NULL)
+    ret = -1;
+  else
+  {
+    GNUNET_assert (papi->send != NULL);
+    GNUNET_assert (papi->get_session != NULL);
+
+    if (session == NULL)
+    {
+      session = papi->get_session (papi->cls, sender_address);
+    }
+    if (session == NULL)
+    {
+      GNUNET_break (0);
+      ret = -1;
+    }
+    else
+    {
+      ret = papi->send (papi->cls, session,
+                        (const char *) pong, ntohs (pong->header.size),
+                        PONG_PRIORITY, ACCEPTABLE_PING_DELAY,
+                        NULL, NULL);
+    }
+  }
+  if (ret != -1)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Transmitted PONG to `%s' via reliable mechanism\n",
+                GNUNET_i2s (sender));
+    /* done! */
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# PONGs unicast via reliable transport"), 1,
+                              GNUNET_NO);
+    GNUNET_free (pong);
+    return;
+  }
+
+  /* no reliable method found, try transmission via all known addresses */
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop
+                            ("# PONGs multicast to all available addresses"), 1,
+                            GNUNET_NO);
+  GST_validation_get_addresses (sender, &multicast_pong, pong);
+  GNUNET_free (pong);
+}
+
+
+/**
+ * Context for the 'validate_address' function
+ */
+struct ValidateAddressContext
+{
+  /**
+   * Hash of the public key of the peer whose address is being validated.
+   */
+  struct GNUNET_PeerIdentity pid;
+
+  /**
+   * Public key of the peer whose address is being validated.
+   */
+  struct GNUNET_CRYPTO_RsaPublicKeyBinaryEncoded public_key;
+};
+
+
+/**
+ * Iterator callback to go over all addresses and try to validate them
+ * (unless blocked or already validated).
+ *
+ * @param cls pointer to a 'struct ValidateAddressContext'
+ * @param address the address
+ * @param expiration expiration time
+ * @return GNUNET_OK (keep the address)
+ */
+static int
+validate_address_iterator (void *cls,
+                           const struct GNUNET_HELLO_Address *address,
+                           struct GNUNET_TIME_Absolute expiration)
+{
+  const struct ValidateAddressContext *vac = cls;
+  struct ValidationEntry *ve;
+
+  if (GNUNET_TIME_absolute_get_remaining (expiration).rel_value == 0)
+    return GNUNET_OK;           /* expired */
+  ve = find_validation_entry (&vac->public_key, address);
+  if (GNUNET_SCHEDULER_NO_TASK == ve->revalidation_task)
+    ve->revalidation_task = GNUNET_SCHEDULER_add_now (&revalidate_address, ve);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Add the validated peer address to the HELLO.
+ *
+ * @param cls the 'struct ValidationEntry' with the validated address
+ * @param max space in buf
+ * @param buf where to add the address
+ * @return number of bytes written, 0 to signal the
+ *         end of the iteration.
+ */
+static size_t
+add_valid_peer_address (void *cls, size_t max, void *buf)
+{
+  struct ValidationEntry *ve = cls;
+
+  if (GNUNET_YES == ve->copied)
+    return 0;                   /* terminate */
+  ve->copied = GNUNET_YES;
+  return GNUNET_HELLO_add_address (ve->address, ve->valid_until, buf, max);
+}
+
+
+/**
+ * We've received a PONG.  Check if it matches a pending PING and
+ * mark the respective address as confirmed.
+ *
+ * @param sender peer sending the PONG
+ * @param hdr the PONG
+ */
+void
+GST_validation_handle_pong (const struct GNUNET_PeerIdentity *sender,
+                            const struct GNUNET_MessageHeader *hdr)
+{
+  const struct TransportPongMessage *pong;
+  struct ValidationEntry *ve;
+  const char *tname;
+  const char *addr;
+  size_t addrlen;
+  size_t slen;
+  size_t size;
+  struct GNUNET_HELLO_Message *hello;
+  struct GNUNET_HELLO_Address address;
+
+  if (ntohs (hdr->size) < sizeof (struct TransportPongMessage))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  GNUNET_STATISTICS_update (GST_stats,
+                            gettext_noop ("# PONG messages received"), 1,
+                            GNUNET_NO);
+
+  pong = (const struct TransportPongMessage *) hdr;
+  tname = (const char *) &pong[1];
+  size = ntohs (hdr->size) - sizeof (struct TransportPongMessage);
+  addr = memchr (tname, '\0', size);
+  if (NULL == addr)
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+  addr++;
+  slen = strlen (tname) + 1;
+  addrlen = size - slen;
+  address.peer = *sender;
+  address.address = addr;
+  address.address_length = addrlen;
+  address.transport_name = tname;
+  ve = find_validation_entry (NULL, &address);
+  if ((NULL == ve) || (ve->expecting_pong == GNUNET_NO))
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# PONGs dropped, no matching pending validation"),
+                              1, GNUNET_NO);
+    return;
+  }
+  /* now check that PONG is well-formed */
+  if (0 != memcmp (&ve->pid, sender, sizeof (struct GNUNET_PeerIdentity)))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+
+  if (GNUNET_OK !=
+      GNUNET_CRYPTO_rsa_verify (GNUNET_SIGNATURE_PURPOSE_TRANSPORT_PONG_OWN,
+                                &pong->purpose, &pong->signature,
+                                &ve->public_key))
+  {
+    GNUNET_break_op (0);
+    return;
+  }
+
+  if (GNUNET_TIME_absolute_get_remaining
+      (GNUNET_TIME_absolute_ntoh (pong->expiration)).rel_value == 0)
+  {
+    GNUNET_STATISTICS_update (GST_stats,
+                              gettext_noop
+                              ("# PONGs dropped, signature expired"), 1,
+                              GNUNET_NO);
+    return;
+  }
+#if DEBUG_TRANSPORT
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Address validated for peer `%s' with plugin `%s': `%s'\n",
+              GNUNET_i2s (sender), tname, GST_plugins_a2s (tname, addr,
+                                                           addrlen));
+#endif
+
+  /* validity achieved, remember it! */
+  ve->expecting_pong = GNUNET_NO;
+  ve->valid_until = GNUNET_TIME_relative_to_absolute (HELLO_ADDRESS_EXPIRATION);
+  ve->latency = GNUNET_TIME_absolute_get_duration (ve->send_time);
+  {
+    struct GNUNET_ATS_Information ats;
+
+    ats.type = htonl (GNUNET_ATS_QUALITY_NET_DELAY);
+    ats.value = htonl ((uint32_t) ve->latency.rel_value);
+    GNUNET_ATS_address_update (GST_ats, ve->address, NULL, &ats, 1);
+  }
+  /* build HELLO to store in PEERINFO */
+  ve->copied = GNUNET_NO;
+  hello = GNUNET_HELLO_create (&ve->public_key, &add_valid_peer_address, ve);
+  GNUNET_PEERINFO_add_peer (GST_peerinfo, hello);
+  GNUNET_free (hello);
+}
+
+
+/**
+ * We've received a HELLO, check which addresses are new and trigger
+ * validation.
+ *
+ * @param hello the HELLO we received
+ */
+void
+GST_validation_handle_hello (const struct GNUNET_MessageHeader *hello)
+{
+  const struct GNUNET_HELLO_Message *hm =
+      (const struct GNUNET_HELLO_Message *) hello;
+  struct ValidateAddressContext vac;
+  struct GNUNET_HELLO_Message *h;
+
+  if ((GNUNET_OK != GNUNET_HELLO_get_id (hm, &vac.pid)) ||
+      (GNUNET_OK != GNUNET_HELLO_get_key (hm, &vac.public_key)))
+  {
+    /* malformed HELLO */
+    GNUNET_break (0);
+    return;
+  }
+  if (0 ==
+      memcmp (&GST_my_identity, &vac.pid, sizeof (struct GNUNET_PeerIdentity)))
+    return;
+  /* Add peer identity without addresses to peerinfo service */
+  h = GNUNET_HELLO_create (&vac.public_key, NULL, NULL);
+  GNUNET_PEERINFO_add_peer (GST_peerinfo, h);
+#if VERBOSE_VALIDATION
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              _("Adding `%s' without addresses for peer `%s'\n"), "HELLO",
+              GNUNET_i2s (&vac.pid));
+#endif
+  GNUNET_free (h);
+  GNUNET_assert (NULL ==
+                 GNUNET_HELLO_iterate_addresses (hm, GNUNET_NO,
+                                                 &validate_address_iterator,
+                                                 &vac));
+}
+
+
+/**
+ * Closure for 'iterate_addresses'
+ */
+struct IteratorContext
+{
+  /**
+   * Function to call on each address.
+   */
+  GST_ValidationAddressCallback cb;
+
+  /**
+   * Closure for 'cb'.
+   */
+  void *cb_cls;
+
+};
+
+
+/**
+ * Call the callback in the closure for each validation entry.
+ *
+ * @param cls the 'struct GST_ValidationIteratorContext'
+ * @param key the peer's identity
+ * @param value the 'struct ValidationEntry'
+ * @return GNUNET_OK (continue to iterate)
+ */
+static int
+iterate_addresses (void *cls, const GNUNET_HashCode * key, void *value)
+{
+  struct IteratorContext *ic = cls;
+  struct ValidationEntry *ve = value;
+
+  ic->cb (ic->cb_cls, &ve->public_key, ve->valid_until, ve->revalidation_block,
+          ve->address);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Call the given function for each address for the given target.
+ * Can either give a snapshot (synchronous API) or be continuous.
+ *
+ * @param target peer information is requested for
+ * @param cb function to call; will not be called after this function returns
+ * @param cb_cls closure for 'cb'
+ */
+void
+GST_validation_get_addresses (const struct GNUNET_PeerIdentity *target,
+                              GST_ValidationAddressCallback cb, void *cb_cls)
+{
+  struct IteratorContext ic;
+
+  ic.cb = cb;
+  ic.cb_cls = cb_cls;
+  GNUNET_CONTAINER_multihashmap_get_multiple (validation_map,
+                                              &target->hashPubKey,
+                                              &iterate_addresses, &ic);
+}
+
+
+/**
+ * Update if we are using an address for a connection actively right now.
+ * Based on this, the validation module will measure latency for the
+ * address more or less often.
+ *
+ * @param address the address
+ * @param session the session
+ * @param in_use GNUNET_YES if we are now using the address for a connection,
+ *               GNUNET_NO if we are no longer using the address for a connection
+ */
+void
+GST_validation_set_address_use (const struct GNUNET_HELLO_Address *address,
+                                struct Session *session,
+                                int in_use)
+{
+  struct ValidationEntry *ve;
+
+  if (NULL != address)
+    ve = find_validation_entry (NULL, address);
+  else
+    ve = NULL;                  /* FIXME: lookup based on session... */
+  if (NULL == ve)
+  {
+    /* this can happen for inbound connections (sender_address_len == 0); */
+    return;
+  }
+  if (ve->in_use == in_use)
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "GST_validation_set_address_use: %s %s: ve->in_use %i <-> in_use %i\n",
+                GNUNET_i2s (&address->peer), GST_plugins_a2s (address), ve->in_use,
+                in_use);
+  GNUNET_break (ve->in_use != in_use);  /* should be different... */
+  ve->in_use = in_use;
+  if (in_use == GNUNET_YES)
+  {
+    /* from now on, higher frequeny, so reschedule now */
+    GNUNET_SCHEDULER_cancel (ve->revalidation_task);
+    ve->revalidation_task = GNUNET_SCHEDULER_add_now (&revalidate_address, ve);
+  }
+}
+
+
+/**
+ * Query validation about the latest observed latency on a given
+ * address.
+ *
+ * @param sender peer
+ * @param address the address
+ * @param session session
+ * @return observed latency of the address, FOREVER if the address was
+ *         never successfully validated
+ */
+struct GNUNET_TIME_Relative
+GST_validation_get_address_latency (const struct GNUNET_PeerIdentity *sender,
+                                    const struct GNUNET_HELLO_Address *address,
+                                    struct Session *session)
+{
+  struct ValidationEntry *ve;
+
+  if (NULL == address)
+  {
+    GNUNET_break (0);           // FIXME: support having latency only with session...
+    return GNUNET_TIME_UNIT_FOREVER_REL;
+  }
+  ve = find_validation_entry (NULL, address);
+  if (NULL == ve)
+    return GNUNET_TIME_UNIT_FOREVER_REL;
+  return ve->latency;
+}
+
+
+/* end of file gnunet-service-transport_validation.c */