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path: root/src/transport/plugin_transport_udp.c
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/*
     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/plugin_transport_udp.c
 * @brief Implementation of the UDP transport protocol
 * @author Christian Grothoff
 * @author Nathan Evans
 * @author Matthias Wachs
 */
#include "platform.h"
#include "plugin_transport_udp.h"
#include "gnunet_hello_lib.h"
#include "gnunet_util_lib.h"
#include "gnunet_fragmentation_lib.h"
#include "gnunet_nat_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_resolver_service.h"
#include "gnunet_signatures.h"
#include "gnunet_constants.h"
#include "gnunet_statistics_service.h"
#include "gnunet_transport_service.h"
#include "gnunet_transport_plugin.h"
#include "transport.h"

#define LOG(kind,...) GNUNET_log_from (kind, "transport-udp", __VA_ARGS__)


/**
 * Number of messages we can defragment in parallel.  We only really
 * defragment 1 message at a time, but if messages get re-ordered, we
 * may want to keep knowledge about the previous message to avoid
 * discarding the current message in favor of a single fragment of a
 * previous message.  3 should be good since we don't expect massive
 * message reorderings with UDP.
 */
#define UDP_MAX_MESSAGES_IN_DEFRAG 3

/**
 * We keep a defragmentation queue per sender address.  How many
 * sender addresses do we support at the same time? Memory consumption
 * is roughly a factor of 32k * UDP_MAX_MESSAGES_IN_DEFRAG times this
 * value. (So 128 corresponds to 12 MB and should suffice for
 * connecting to roughly 128 peers via UDP).
 */
#define UDP_MAX_SENDER_ADDRESSES_WITH_DEFRAG 128



/**
 * Closure for 'append_port'.
 */
struct PrettyPrinterContext
{
  /**
   * Function to call with the result.
   */
  GNUNET_TRANSPORT_AddressStringCallback asc;

  /**
   * Clsoure for 'asc'.
   */
  void *asc_cls;

  /**
   * Port to add after the IP address.
   */
  uint16_t port;
};

struct Session
{
  /**
   * Which peer is this session for?
   */
  struct GNUNET_PeerIdentity target;

  /**
   * Address of the other peer
   */
  const struct sockaddr *sock_addr;

  size_t addrlen;

  /**
   * Desired delay for next sending we send to other peer
   */
  struct GNUNET_TIME_Relative flow_delay_for_other_peer;

  /**
   * Desired delay for next sending we received from other peer
   */
  struct GNUNET_TIME_Absolute flow_delay_from_other_peer;

  /**
   * expected delay for ACKs
   */
  struct GNUNET_TIME_Relative last_expected_delay;


  struct GNUNET_ATS_Information ats;

  struct FragmentationContext * frag_ctx;
};


struct SessionCompareContext
{
  struct Session *res;
  const struct GNUNET_HELLO_Address *addr;
};


/**
 * Closure for 'process_inbound_tokenized_messages'
 */
struct SourceInformation
{
  /**
   * Sender identity.
   */
  struct GNUNET_PeerIdentity sender;

  /**
   * Source address.
   */
  const void *arg;

  /**
   * Number of bytes in source address.
   */
  size_t args;

  struct Session *session;
};


/**
 * Closure for 'find_receive_context'.
 */
struct FindReceiveContext
{
  /**
   * Where to store the result.
   */
  struct DefragContext *rc;

  /**
   * Address to find.
   */
  const struct sockaddr *addr;

  /**
   * Number of bytes in 'addr'.
   */
  socklen_t addr_len;

  struct Session *session;
};



/**
 * Data structure to track defragmentation contexts based
 * on the source of the UDP traffic.
 */
struct DefragContext
{

  /**
   * Defragmentation context.
   */
  struct GNUNET_DEFRAGMENT_Context *defrag;

  /**
   * Source address this receive context is for (allocated at the
   * end of the struct).
   */
  const struct sockaddr *src_addr;

  /**
   * Reference to master plugin struct.
   */
  struct Plugin *plugin;

  /**
   * Node in the defrag heap.
   */
  struct GNUNET_CONTAINER_HeapNode *hnode;

  /**
   * Length of 'src_addr'
   */
  size_t addr_len;
};



/**
 * Closure for 'process_inbound_tokenized_messages'
 */
struct FragmentationContext
{
  struct FragmentationContext * next;
  struct FragmentationContext * prev;

  struct Plugin * plugin;
  struct GNUNET_FRAGMENT_Context * frag;
  struct Session * session;

  struct GNUNET_TIME_Absolute timeout;


  /**
   * Function to call upon completion of the transmission.
   */
  GNUNET_TRANSPORT_TransmitContinuation cont;

  /**
   * Closure for 'cont'.
   */
  void *cont_cls;

  size_t bytes_to_send;
};


struct UDPMessageWrapper
{
  struct Session *session;
  struct UDPMessageWrapper *prev;
  struct UDPMessageWrapper *next;
  char *udp;
  size_t msg_size;

  struct GNUNET_TIME_Absolute timeout;

  /**
   * Function to call upon completion of the transmission.
   */
  GNUNET_TRANSPORT_TransmitContinuation cont;

  /**
   * Closure for 'cont'.
   */
  void *cont_cls;

  struct FragmentationContext *frag_ctx;

};


/**
 * UDP ACK Message-Packet header (after defragmentation).
 */
struct UDP_ACK_Message
{
  /**
   * Message header.
   */
  struct GNUNET_MessageHeader header;

  /**
   * Desired delay for flow control
   */
  uint32_t delay;

  /**
   * What is the identity of the sender
   */
  struct GNUNET_PeerIdentity sender;

};



/**
 * Function called for a quick conversion of the binary address to
 * a numeric address.  Note that the caller must not free the
 * address and that the next call to this function is allowed
 * to override the address again.
 *
 * @param cls closure
 * @param addr binary address
 * @param addrlen length of the address
 * @return string representing the same address
 */
const char *
udp_address_to_string (void *cls, const void *addr, size_t addrlen)
{
  static char rbuf[INET6_ADDRSTRLEN + 10];
  char buf[INET6_ADDRSTRLEN];
  const void *sb;
  struct in_addr a4;
  struct in6_addr a6;
  const struct IPv4UdpAddress *t4;
  const struct IPv6UdpAddress *t6;
  int af;
  uint16_t port;

  if (addrlen == sizeof (struct IPv6UdpAddress))
  {
    t6 = addr;
    af = AF_INET6;
    port = ntohs (t6->u6_port);
    memcpy (&a6, &t6->ipv6_addr, sizeof (a6));
    sb = &a6;
  }
  else if (addrlen == sizeof (struct IPv4UdpAddress))
  {
    t4 = addr;
    af = AF_INET;
    port = ntohs (t4->u4_port);
    memcpy (&a4, &t4->ipv4_addr, sizeof (a4));
    sb = &a4;
  }
  else
  {
    GNUNET_break_op (0);
    return NULL;
  }
  inet_ntop (af, sb, buf, INET6_ADDRSTRLEN);
  GNUNET_snprintf (rbuf, sizeof (rbuf), (af == AF_INET6) ? "[%s]:%u" : "%s:%u",
                   buf, port);
  return rbuf;
}


/**
 * Append our port and forward the result.
 *
 * @param cls a 'struct PrettyPrinterContext'
 * @param hostname result from DNS resolver
 */
static void
append_port (void *cls, const char *hostname)
{
  struct PrettyPrinterContext *ppc = cls;
  char *ret;

  if (hostname == NULL)
  {
    ppc->asc (ppc->asc_cls, NULL);
    GNUNET_free (ppc);
    return;
  }
  GNUNET_asprintf (&ret, "%s:%d", hostname, ppc->port);
  ppc->asc (ppc->asc_cls, ret);
  GNUNET_free (ret);
}


/**
 * Convert the transports address to a nice, human-readable
 * format.
 *
 * @param cls closure
 * @param type name of the transport that generated the address
 * @param addr one of the addresses of the host, NULL for the last address
 *        the specific address format depends on the transport
 * @param addrlen length of the address
 * @param numeric should (IP) addresses be displayed in numeric form?
 * @param timeout after how long should we give up?
 * @param asc function to call on each string
 * @param asc_cls closure for asc
 */
static void
udp_plugin_address_pretty_printer (void *cls, const char *type,
                                   const void *addr, size_t addrlen,
                                   int numeric,
                                   struct GNUNET_TIME_Relative timeout,
                                   GNUNET_TRANSPORT_AddressStringCallback asc,
                                   void *asc_cls)
{
  struct PrettyPrinterContext *ppc;
  const void *sb;
  size_t sbs;
  struct sockaddr_in a4;
  struct sockaddr_in6 a6;
  const struct IPv4UdpAddress *u4;
  const struct IPv6UdpAddress *u6;
  uint16_t port;

  if (addrlen == sizeof (struct IPv6UdpAddress))
  {
    u6 = addr;
    memset (&a6, 0, sizeof (a6));
    a6.sin6_family = AF_INET6;
#if HAVE_SOCKADDR_IN_SIN_LEN
    a6.sin6_len = sizeof (a6);
#endif
    a6.sin6_port = u6->u6_port;
    memcpy (&a6.sin6_addr, &u6->ipv6_addr, sizeof (struct in6_addr));
    port = ntohs (u6->u6_port);
    sb = &a6;
    sbs = sizeof (a6);
  }
  else if (addrlen == sizeof (struct IPv4UdpAddress))
  {
    u4 = addr;
    memset (&a4, 0, sizeof (a4));
    a4.sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
    a4.sin_len = sizeof (a4);
#endif
    a4.sin_port = u4->u4_port;
    a4.sin_addr.s_addr = u4->ipv4_addr;
    port = ntohs (u4->u4_port);
    sb = &a4;
    sbs = sizeof (a4);
  }
  else
  {
    /* invalid address */
    GNUNET_break_op (0);
    asc (asc_cls, NULL);
    return;
  }
  ppc = GNUNET_malloc (sizeof (struct PrettyPrinterContext));
  ppc->asc = asc;
  ppc->asc_cls = asc_cls;
  ppc->port = port;
  GNUNET_RESOLVER_hostname_get (sb, sbs, !numeric, timeout, &append_port, ppc);
}


/**
 * Check if the given port is plausible (must be either our listen
 * port or our advertised port).  If it is neither, we return
 * GNUNET_SYSERR.
 *
 * @param plugin global variables
 * @param in_port port number to check
 * @return GNUNET_OK if port is either open_port or adv_port
 */
static int
check_port (struct Plugin *plugin, uint16_t in_port)
{
  if ((in_port == plugin->port) || (in_port == plugin->aport))
    return GNUNET_OK;
  return GNUNET_SYSERR;
}



/**
 * Function that will be called to check if a binary address for this
 * plugin is well-formed and corresponds to an address for THIS peer
 * (as per our configuration).  Naturally, if absolutely necessary,
 * plugins can be a bit conservative in their answer, but in general
 * plugins should make sure that the address does not redirect
 * traffic to a 3rd party that might try to man-in-the-middle our
 * traffic.
 *
 * @param cls closure, should be our handle to the Plugin
 * @param addr pointer to the address
 * @param addrlen length of addr
 * @return GNUNET_OK if this is a plausible address for this peer
 *         and transport, GNUNET_SYSERR if not
 *
 */
static int
udp_plugin_check_address (void *cls, const void *addr, size_t addrlen)
{
  struct Plugin *plugin = cls;
  struct IPv4UdpAddress *v4;
  struct IPv6UdpAddress *v6;

  if ((addrlen != sizeof (struct IPv4UdpAddress)) &&
      (addrlen != sizeof (struct IPv6UdpAddress)))
  {
    GNUNET_break_op (0);
    return GNUNET_SYSERR;
  }
  if (addrlen == sizeof (struct IPv4UdpAddress))
  {
    v4 = (struct IPv4UdpAddress *) addr;
    if (GNUNET_OK != check_port (plugin, ntohs (v4->u4_port)))
      return GNUNET_SYSERR;
    if (GNUNET_OK !=
        GNUNET_NAT_test_address (plugin->nat, &v4->ipv4_addr,
                                 sizeof (struct in_addr)))
      return GNUNET_SYSERR;
  }
  else
  {
    v6 = (struct IPv6UdpAddress *) addr;
    if (IN6_IS_ADDR_LINKLOCAL (&v6->ipv6_addr))
    {
      GNUNET_break_op (0);
      return GNUNET_SYSERR;
    }
    if (GNUNET_OK != check_port (plugin, ntohs (v6->u6_port)))
      return GNUNET_SYSERR;
    if (GNUNET_OK !=
        GNUNET_NAT_test_address (plugin->nat, &v6->ipv6_addr,
                                 sizeof (struct in6_addr)))
      return GNUNET_SYSERR;
  }
  return GNUNET_OK;
}


/**
 * Destroy a session, plugin is being unloaded.
 *
 * @param cls unused
 * @param key hash of public key of target peer
 * @param value a 'struct PeerSession*' to clean up
 * @return GNUNET_OK (continue to iterate)
 */
static int
disconnect_and_free_it (void *cls, const GNUNET_HashCode * key, void *value)
{
  struct Plugin *plugin = cls;
  struct Session *s = value;
  struct UDPMessageWrapper *udpw;

#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Session %p to peer `%s' address ended \n",
         s,
         GNUNET_i2s (&s->target),
         GNUNET_a2s (s->sock_addr, s->addrlen));
#endif
  plugin->env->session_end (plugin->env->cls, &s->target, s);

  if (s->frag_ctx != NULL)
  {
    GNUNET_FRAGMENT_context_destroy(s->frag_ctx->frag);
    GNUNET_free (s->frag_ctx);
    s->frag_ctx = NULL;
  }

  udpw = plugin->msg_head;
  while (udpw != NULL)
  {
    if (udpw->session == s)
    {
      GNUNET_CONTAINER_DLL_remove(plugin->msg_head, plugin->msg_tail, udpw);

      if (udpw->cont != NULL)
        udpw->cont (udpw->cont_cls, &s->target, GNUNET_SYSERR);
      GNUNET_free (udpw);
    }
    udpw = plugin->msg_head;
  }

  GNUNET_assert (GNUNET_YES ==
                 GNUNET_CONTAINER_multihashmap_remove (plugin->sessions,
                                                       &s->target.hashPubKey,
                                                       s));


  GNUNET_free (s);
  return GNUNET_OK;
}


/**
 * Disconnect from a remote node.  Clean up session if we have one for this peer
 *
 * @param cls closure for this call (should be handle to Plugin)
 * @param target the peeridentity of the peer to disconnect
 * @return GNUNET_OK on success, GNUNET_SYSERR if the operation failed
 */
static void
udp_disconnect (void *cls, const struct GNUNET_PeerIdentity *target)
{
  struct Plugin *plugin = cls;
  GNUNET_assert (plugin != NULL);

  GNUNET_assert (target != NULL);
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Disconnecting from peer `%s'\n", GNUNET_i2s (target));
#endif
  /* Clean up sessions */
  GNUNET_CONTAINER_multihashmap_get_multiple (plugin->sessions, &target->hashPubKey, &disconnect_and_free_it, plugin);

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "FREEED SESSIONS from peer `%s'\n", GNUNET_i2s (target));
}

static struct Session *
create_session (struct Plugin *plugin, const struct GNUNET_PeerIdentity *target,
                const void *addr, size_t addrlen,
                GNUNET_TRANSPORT_TransmitContinuation cont, void *cont_cls)
{
  struct Session *s;
  const struct IPv4UdpAddress *t4;
  const struct IPv6UdpAddress *t6;
  struct sockaddr_in *v4;
  struct sockaddr_in6 *v6;
  size_t len;

  switch (addrlen)
  {
  case sizeof (struct IPv4UdpAddress):
    if (NULL == plugin->sockv4)
    {
      return NULL;
    }
    t4 = addr;
    s = GNUNET_malloc (sizeof (struct Session) + sizeof (struct sockaddr_in));
    len = sizeof (struct sockaddr_in);
    v4 = (struct sockaddr_in *) &s[1];
    v4->sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
    v4->sin_len = sizeof (struct sockaddr_in);
#endif
    v4->sin_port = t4->u4_port;
    v4->sin_addr.s_addr = t4->ipv4_addr;
    s->ats = plugin->env->get_address_type (plugin->env->cls, (const struct sockaddr *) v4, sizeof (struct sockaddr_in));
    break;
  case sizeof (struct IPv6UdpAddress):
    if (NULL == plugin->sockv6)
    {
      return NULL;
    }
    t6 = addr;
    s =
        GNUNET_malloc (sizeof (struct Session) + sizeof (struct sockaddr_in6));
    len = sizeof (struct sockaddr_in6);
    v6 = (struct sockaddr_in6 *) &s[1];
    v6->sin6_family = AF_INET6;
#if HAVE_SOCKADDR_IN_SIN_LEN
    v6->sin6_len = sizeof (struct sockaddr_in6);
#endif
    v6->sin6_port = t6->u6_port;
    v6->sin6_addr = t6->ipv6_addr;
    s->ats = plugin->env->get_address_type (plugin->env->cls, (const struct sockaddr *) v6, sizeof (struct sockaddr_in6));
    break;
  default:
    /* Must have a valid address to send to */
    GNUNET_break_op (0);
    return NULL;
  }

  s->addrlen = len;
  s->target = *target;
  s->sock_addr = (const struct sockaddr *) &s[1];
  s->flow_delay_for_other_peer = GNUNET_TIME_relative_get_zero();
  s->flow_delay_from_other_peer = GNUNET_TIME_absolute_get_zero();
  s->last_expected_delay = GNUNET_TIME_UNIT_SECONDS;

  return s;
}

static int session_cmp_it (void *cls,
                           const GNUNET_HashCode * key,
                           void *value)
{
  struct SessionCompareContext * cctx = cls;
  const struct GNUNET_HELLO_Address *address = cctx->addr;
  struct Session *s = value;

  socklen_t s_addrlen = s->addrlen;

#if VERBOSE_UDP
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Comparing  address %s <-> %s\n",
      udp_address_to_string (NULL, (void *) address->address, address->address_length),
      GNUNET_a2s (s->sock_addr, s->addrlen));
#endif

  if ((address->address_length == sizeof (struct IPv4UdpAddress)) &&
      (s_addrlen == sizeof (struct sockaddr_in)))
  {
    struct IPv4UdpAddress * u4 = NULL;
    u4 = (struct IPv4UdpAddress *) address->address;
    const struct sockaddr_in *s4 = (const struct sockaddr_in *) s->sock_addr;
    if ((0 == memcmp ((const void *) &u4->ipv4_addr,(const void *) &s4->sin_addr, sizeof (struct in_addr))) &&
        (u4->u4_port == s4->sin_port))
    {
      cctx->res = s;
      return GNUNET_NO;
    }

  }
  if ((address->address_length == sizeof (struct IPv6UdpAddress)) &&
      (s_addrlen == sizeof (struct sockaddr_in6)))
  {
    struct IPv6UdpAddress * u6 = NULL;
    u6 = (struct IPv6UdpAddress *) address->address;
    const struct sockaddr_in6 *s6 = (const struct sockaddr_in6 *) s->sock_addr;
    if ((0 == memcmp (&u6->ipv6_addr, &s6->sin6_addr, sizeof (struct in6_addr))) &&
        (u6->u6_port == s6->sin6_port))
    {
      cctx->res = s;
      return GNUNET_NO;
    }
  }


  return GNUNET_YES;
}


/**
 * Creates a new outbound session the transport service will use to send data to the
 * peer
 *
 * @param cls the plugin
 * @param address the address
 * @return the session or NULL of max connections exceeded
 */
static struct Session *
udp_plugin_get_session (void *cls,
                  const struct GNUNET_HELLO_Address *address)
{
  struct Session * s = NULL;
  struct Plugin * plugin = cls;

  GNUNET_assert (plugin != NULL);
  GNUNET_assert (address != NULL);

  if ((address->address == NULL) ||
      ((address->address_length != sizeof (struct IPv4UdpAddress)) &&
      (address->address_length != sizeof (struct IPv6UdpAddress))))
  {
    GNUNET_break (0);
    return NULL;
  }

  /* check if session already exists */
  struct SessionCompareContext cctx;
  cctx.addr = address;
  cctx.res = NULL;
#if VERBOSE_UDP
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Looking for existing session for peer `%s' `%s' \n", GNUNET_i2s (&address->peer), udp_address_to_string(NULL, address->address, address->address_length));
#endif
  GNUNET_CONTAINER_multihashmap_get_multiple(plugin->sessions, &address->peer.hashPubKey, session_cmp_it, &cctx);
  if (cctx.res != NULL)
  {
#if VERBOSE_UDP
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Found existing session %p\n", cctx.res);
#endif
    return cctx.res;
  }

  /* otherwise create new */
  s = create_session (plugin,
      &address->peer,
      address->address,
      address->address_length,
      NULL, NULL);
#if VERBOSE
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
              "Creating new session %p for peer `%s' address `%s'\n",
              s,
              GNUNET_i2s(&address->peer),
              udp_address_to_string(NULL,address->address,address->address_length));
#endif
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONTAINER_multihashmap_put (plugin->sessions,
                                                    &s->target.hashPubKey,
                                                    s,
                                                    GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));

  return s;
}

/**
 * Function that is called with messages created by the fragmentation
 * module.  In the case of the 'proc' callback of the
 * GNUNET_FRAGMENT_context_create function, this function must
 * eventually call 'GNUNET_FRAGMENT_context_transmission_done'.
 *
 * @param cls closure, the 'struct FragmentationContext'
 * @param msg the message that was created
 */
static void
enqueue_fragment (void *cls, const struct GNUNET_MessageHeader *msg)
{
  struct FragmentationContext *frag_ctx = cls;
  struct Plugin *plugin = frag_ctx->plugin;
  struct UDPMessageWrapper * udpw;

  size_t msg_len = ntohs (msg->size);

#if VERBOSE_UDP
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Enqueuing fragment with %u bytes %u\n", msg_len , sizeof (struct UDPMessageWrapper));
#endif

  udpw = GNUNET_malloc (sizeof (struct UDPMessageWrapper) + msg_len);
  udpw->session = frag_ctx->session;
  udpw->udp = (char *) &udpw[1];

  udpw->msg_size = msg_len;
  udpw->cont = frag_ctx->cont;
  udpw->cont_cls = frag_ctx->cont_cls;
  udpw->timeout = frag_ctx->timeout;
  udpw->frag_ctx = frag_ctx;
  memcpy (udpw->udp, msg, msg_len);

  GNUNET_CONTAINER_DLL_insert(plugin->msg_head, plugin->msg_tail, udpw);
}


/**
 * Function that can be used by the transport service to transmit
 * a message using the plugin.   Note that in the case of a
 * peer disconnecting, the continuation MUST be called
 * prior to the disconnect notification itself.  This function
 * will be called with this peer's HELLO message to initiate
 * a fresh connection to another peer.
 *
 * @param cls closure
 * @param session which session must be used
 * @param msgbuf the message to transmit
 * @param msgbuf_size number of bytes in 'msgbuf'
 * @param priority how important is the message (most plugins will
 *                 ignore message priority and just FIFO)
 * @param to how long to wait at most for the transmission (does not
 *                require plugins to discard the message after the timeout,
 *                just advisory for the desired delay; most plugins will ignore
 *                this as well)
 * @param cont continuation to call once the message has
 *        been transmitted (or if the transport is ready
 *        for the next transmission call; or if the
 *        peer disconnected...); can be NULL
 * @param cont_cls closure for cont
 * @return number of bytes used (on the physical network, with overheads);
 *         -1 on hard errors (i.e. address invalid); 0 is a legal value
 *         and does NOT mean that the message was not transmitted (DV)
 */
static ssize_t
udp_plugin_send (void *cls,
                  struct Session *s,
                  const char *msgbuf, size_t msgbuf_size,
                  unsigned int priority,
                  struct GNUNET_TIME_Relative to,
                  GNUNET_TRANSPORT_TransmitContinuation cont, void *cont_cls)
{
  struct Plugin *plugin = cls;
  size_t mlen = msgbuf_size + sizeof (struct UDPMessage);

  struct UDPMessageWrapper * udpw;
  struct UDPMessage *udp;
  char mbuf[mlen];
  GNUNET_assert (plugin != NULL);
  GNUNET_assert (s != NULL);

  if (mlen >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }

  if (GNUNET_YES != GNUNET_CONTAINER_multihashmap_contains_value(plugin->sessions, &s->target.hashPubKey, s))
  {
    GNUNET_break (0);
    return GNUNET_SYSERR;
  }

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "UDP transmits %u-byte message to `%s' using address `%s'\n",
         msgbuf_size,
         GNUNET_i2s (&s->target),
         GNUNET_a2s(s->sock_addr, s->addrlen));

  /* Message */
  udp = (struct UDPMessage *) mbuf;
  udp->header.size = htons (mlen);
  udp->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_UDP_MESSAGE);
  udp->reserved = htonl (0);
  udp->sender = *plugin->env->my_identity;

  if (mlen <= UDP_MTU)
  {
    udpw = GNUNET_malloc (sizeof (struct UDPMessageWrapper) + mlen);
    udpw->session = s;
    udpw->udp = (char *) &udpw[1];
    udpw->msg_size = mlen;
    udpw->timeout = GNUNET_TIME_absolute_add(GNUNET_TIME_absolute_get(), to);
    udpw->cont = cont;
    udpw->cont_cls = cont_cls;
    udpw->frag_ctx = NULL;

    memcpy (udpw->udp, udp, sizeof (struct UDPMessage));
    memcpy (&udpw->udp[sizeof (struct UDPMessage)], msgbuf, msgbuf_size);

    GNUNET_CONTAINER_DLL_insert(plugin->msg_head, plugin->msg_tail, udpw);
  }
  else
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "UDP has to fragment message \n");
    if  (s->frag_ctx != NULL)
      return GNUNET_SYSERR;
    memcpy (&udp[1], msgbuf, msgbuf_size);
    struct FragmentationContext * frag_ctx = GNUNET_malloc(sizeof (struct FragmentationContext));

    frag_ctx->plugin = plugin;
    frag_ctx->session = s;
    frag_ctx->cont = cont;
    frag_ctx->cont_cls = cont_cls;
    frag_ctx->timeout = GNUNET_TIME_absolute_add(GNUNET_TIME_absolute_get(), to);
    frag_ctx->bytes_to_send = mlen;
    frag_ctx->frag = GNUNET_FRAGMENT_context_create (plugin->env->stats,
              UDP_MTU,
              &plugin->tracker,
              s->last_expected_delay,
              &udp->header,
              &enqueue_fragment,
              frag_ctx);

    s->frag_ctx = frag_ctx;

  }
  return mlen;
}

static ssize_t udp_plugin_send_wrapper (void *cls,
                                        const struct
                                        GNUNET_PeerIdentity *
                                        target,
                                        const char *msgbuf,
                                        size_t msgbuf_size,
                                        uint32_t priority,
                                        struct
                                        GNUNET_TIME_Relative
                                        timeout,
                                        struct Session * session,
                                        const void *addr,
                                        size_t addrlen,
                                        int force_address,
                                        GNUNET_TRANSPORT_TransmitContinuation
                                        cont, void *cont_cls)
{
  int ret;
  struct Session * s = NULL;
  struct GNUNET_HELLO_Address * ha = NULL;

  ha = GNUNET_HELLO_address_allocate(target, "", addr,addrlen);
  GNUNET_assert (ha != NULL);
  s = udp_plugin_get_session(cls, ha);
  GNUNET_assert (s != NULL);
  GNUNET_free (ha);
  ret = udp_plugin_send (cls, s, msgbuf, msgbuf_size, priority, timeout, cont, cont_cls);

  return ret;
}


/**
 * Our external IP address/port mapping has changed.
 *
 * @param cls closure, the 'struct LocalAddrList'
 * @param add_remove GNUNET_YES to mean the new public IP address, GNUNET_NO to mean
 *     the previous (now invalid) one
 * @param addr either the previous or the new public IP address
 * @param addrlen actual lenght of the address
 */
static void
udp_nat_port_map_callback (void *cls, int add_remove,
                           const struct sockaddr *addr, socklen_t addrlen)
{
  struct Plugin *plugin = cls;
  struct IPv4UdpAddress u4;
  struct IPv6UdpAddress u6;
  void *arg;
  size_t args;

  /* convert 'addr' to our internal format */
  switch (addr->sa_family)
  {
  case AF_INET:
    GNUNET_assert (addrlen == sizeof (struct sockaddr_in));
    u4.ipv4_addr = ((struct sockaddr_in *) addr)->sin_addr.s_addr;
    u4.u4_port = ((struct sockaddr_in *) addr)->sin_port;
    arg = &u4;
    args = sizeof (u4);
    break;
  case AF_INET6:
    GNUNET_assert (addrlen == sizeof (struct sockaddr_in6));
    memcpy (&u6.ipv6_addr, &((struct sockaddr_in6 *) addr)->sin6_addr,
            sizeof (struct in6_addr));
    u6.u6_port = ((struct sockaddr_in6 *) addr)->sin6_port;
    arg = &u6;
    args = sizeof (u6);
    break;
  default:
    GNUNET_break (0);
    return;
  }
  /* modify our published address list */
  plugin->env->notify_address (plugin->env->cls, add_remove, arg, args);
}



/**
 * Message tokenizer has broken up an incomming message. Pass it on
 * to the service.
 *
 * @param cls the 'struct Plugin'
 * @param client the 'struct SourceInformation'
 * @param hdr the actual message
 */
static void
process_inbound_tokenized_messages (void *cls, void *client,
                                    const struct GNUNET_MessageHeader *hdr)
{
  struct Plugin *plugin = cls;
  struct SourceInformation *si = client;
  struct GNUNET_ATS_Information ats[2];
  struct GNUNET_TIME_Relative delay;

  GNUNET_assert (si->session != NULL);
  /* setup ATS */
  ats[0].type = htonl (GNUNET_ATS_QUALITY_NET_DISTANCE);
  ats[0].value = htonl (1);
  ats[1] = si->session->ats;
  GNUNET_break (ntohl(ats[1].value) != GNUNET_ATS_NET_UNSPECIFIED);

  delay = plugin->env->receive (plugin->env->cls,
                &si->sender,
                hdr,
                (const struct GNUNET_ATS_Information *) &ats, 2,
                NULL,
                si->arg,
                si->args);
  si->session->flow_delay_for_other_peer = delay;
}


/**
 * We've received a UDP Message.  Process it (pass contents to main service).
 *
 * @param plugin plugin context
 * @param msg the message
 * @param sender_addr sender address
 * @param sender_addr_len number of bytes in sender_addr
 */
static void
process_udp_message (struct Plugin *plugin, const struct UDPMessage *msg,
                     const struct sockaddr *sender_addr,
                     socklen_t sender_addr_len)
{
  struct SourceInformation si;
  struct Session * s = NULL;
  struct IPv4UdpAddress u4;
  struct IPv6UdpAddress u6;
  struct GNUNET_ATS_Information ats;
  const void *arg;
  size_t args;

  if (0 != ntohl (msg->reserved))
  {
    GNUNET_break_op (0);
    return;
  }
  if (ntohs (msg->header.size) <
      sizeof (struct GNUNET_MessageHeader) + sizeof (struct UDPMessage))
  {
    GNUNET_break_op (0);
    return;
  }

  ats.type = htonl (GNUNET_ATS_NETWORK_TYPE);
  ats.value = htonl (GNUNET_ATS_NET_UNSPECIFIED);
  /* convert address */
  switch (sender_addr->sa_family)
  {
  case AF_INET:
    GNUNET_assert (sender_addr_len == sizeof (struct sockaddr_in));
    u4.ipv4_addr = ((struct sockaddr_in *) sender_addr)->sin_addr.s_addr;
    u4.u4_port = ((struct sockaddr_in *) sender_addr)->sin_port;
    arg = &u4;
    args = sizeof (u4);
    break;
  case AF_INET6:
    GNUNET_assert (sender_addr_len == sizeof (struct sockaddr_in6));
    u6.ipv6_addr = ((struct sockaddr_in6 *) sender_addr)->sin6_addr;
    u6.u6_port = ((struct sockaddr_in6 *) sender_addr)->sin6_port;
    arg = &u6;
    args = sizeof (u6);
    break;
  default:
    GNUNET_break (0);
    return;
  }
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Received message with %u bytes from peer `%s' at `%s'\n",
       (unsigned int) ntohs (msg->header.size), GNUNET_i2s (&msg->sender),
       GNUNET_a2s (sender_addr, sender_addr_len));
#endif

  struct GNUNET_HELLO_Address * address = GNUNET_HELLO_address_allocate(&msg->sender, "udp", arg, args);
  s = udp_plugin_get_session(plugin, address);
  GNUNET_free (address);

  /* iterate over all embedded messages */
  si.session = s;
  si.sender = msg->sender;
  si.arg = arg;
  si.args = args;

  GNUNET_SERVER_mst_receive (plugin->mst, &si, (const char *) &msg[1],
                             ntohs (msg->header.size) -
                             sizeof (struct UDPMessage), GNUNET_YES, GNUNET_NO);
}


/**
 * Scan the heap for a receive context with the given address.
 *
 * @param cls the 'struct FindReceiveContext'
 * @param node internal node of the heap
 * @param element value stored at the node (a 'struct ReceiveContext')
 * @param cost cost associated with the node
 * @return GNUNET_YES if we should continue to iterate,
 *         GNUNET_NO if not.
 */
static int
find_receive_context (void *cls, struct GNUNET_CONTAINER_HeapNode *node,
                      void *element, GNUNET_CONTAINER_HeapCostType cost)
{
  struct FindReceiveContext *frc = cls;
  struct DefragContext *e = element;

  if ((frc->addr_len == e->addr_len) &&
      (0 == memcmp (frc->addr, e->src_addr, frc->addr_len)))
  {
    frc->rc = e;
    return GNUNET_NO;
  }
  return GNUNET_YES;
}


/**
 * Process a defragmented message.
 *
 * @param cls the 'struct ReceiveContext'
 * @param msg the message
 */
static void
fragment_msg_proc (void *cls, const struct GNUNET_MessageHeader *msg)
{
  struct DefragContext *rc = cls;

  if (ntohs (msg->type) != GNUNET_MESSAGE_TYPE_TRANSPORT_UDP_MESSAGE)
  {
    GNUNET_break (0);
    return;
  }
  if (ntohs (msg->size) < sizeof (struct UDPMessage))
  {
    GNUNET_break (0);
    return;
  }
  process_udp_message (rc->plugin, (const struct UDPMessage *) msg,
                       rc->src_addr, rc->addr_len);
}

struct LookupContext
{
  const struct sockaddr * addr;
  size_t addrlen;

  struct Session *res;
};

static int
lookup_session_by_addr_it (void *cls, const GNUNET_HashCode * key, void *value)
{
  struct LookupContext *l_ctx = cls;
  struct Session * s = value;

  if ((s->addrlen == l_ctx->addrlen) &&
      (0 == memcmp (s->sock_addr, l_ctx->addr, s->addrlen)))
  {
    l_ctx->res = s;
    return GNUNET_NO;
  }
  return GNUNET_YES;
}

/**
 * Transmit an acknowledgement.
 *
 * @param cls the 'struct ReceiveContext'
 * @param id message ID (unused)
 * @param msg ack to transmit
 */
static void
ack_proc (void *cls, uint32_t id, const struct GNUNET_MessageHeader *msg)
{
  struct DefragContext *rc = cls;

  size_t msize = sizeof (struct UDP_ACK_Message) + ntohs (msg->size);
  struct UDP_ACK_Message *udp_ack;
  uint32_t delay = 0;
  struct UDPMessageWrapper *udpw;
  struct Session *s;

  struct LookupContext l_ctx;
  l_ctx.addr = rc->src_addr;
  l_ctx.addrlen = rc->addr_len;
  l_ctx.res = NULL;
  GNUNET_CONTAINER_multihashmap_iterate (rc->plugin->sessions,
      &lookup_session_by_addr_it,
      &l_ctx);
  s = l_ctx.res;

  GNUNET_assert (s != NULL);

  if (s->flow_delay_for_other_peer.rel_value <= UINT32_MAX)
    delay = s->flow_delay_for_other_peer.rel_value;

#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Sending ACK to `%s' including delay of %u ms\n",
       GNUNET_a2s (rc->src_addr,
                   (rc->src_addr->sa_family ==
                    AF_INET) ? sizeof (struct sockaddr_in) : sizeof (struct
                                                                     sockaddr_in6)),
       delay);
#endif
  udpw = GNUNET_malloc (sizeof (struct UDPMessageWrapper) + msize);
  udpw->cont = NULL;
  udpw->cont_cls = NULL;
  udpw->frag_ctx = NULL;
  udpw->msg_size = msize;
  udpw->session = s;
  udpw->timeout = GNUNET_TIME_absolute_get_forever();
  udpw->udp = (char *)&udpw[1];

  udp_ack = (struct UDP_ACK_Message *) udpw->udp;
  udp_ack->header.size = htons ((uint16_t) msize);
  udp_ack->header.type = htons (GNUNET_MESSAGE_TYPE_TRANSPORT_UDP_ACK);
  udp_ack->delay = htonl (delay);
  udp_ack->sender = *rc->plugin->env->my_identity;
  memcpy (&udp_ack[1], msg, ntohs (msg->size));

  GNUNET_CONTAINER_DLL_insert(rc->plugin->msg_head, rc->plugin->msg_tail, udpw);
}


static void read_process_msg (struct Plugin *plugin,
    const struct GNUNET_MessageHeader *msg,
    char *addr,
    socklen_t fromlen)
{
  if (ntohs (msg->size) < sizeof (struct UDPMessage))
  {
    GNUNET_break_op (0);
    return;
  }
  process_udp_message (plugin, (const struct UDPMessage *) msg,
                       (const struct sockaddr *) addr, fromlen);
  return;
}

static void read_process_ack (struct Plugin *plugin,
    const struct GNUNET_MessageHeader *msg,
    char *addr,
    socklen_t fromlen)
{
  const struct GNUNET_MessageHeader *ack;
  const struct UDP_ACK_Message *udp_ack;
  struct LookupContext l_ctx;
  struct Session *s = NULL;
  struct GNUNET_TIME_Relative flow_delay;

  if (ntohs (msg->size) <
      sizeof (struct UDP_ACK_Message) + sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break_op (0);
    return;
  }

  udp_ack = (const struct UDP_ACK_Message *) msg;

  l_ctx.addr = (const struct sockaddr *) addr;
  l_ctx.addrlen = fromlen;
  l_ctx.res = NULL;
  GNUNET_CONTAINER_multihashmap_iterate (plugin->sessions,
      &lookup_session_by_addr_it,
      &l_ctx);
  s = l_ctx.res;

  if ((s == NULL) || (s->frag_ctx == NULL))
    return;

  flow_delay.rel_value = (uint64_t) ntohl (udp_ack->delay);
  LOG (GNUNET_ERROR_TYPE_DEBUG, "We received a sending delay of %llu\n",
       flow_delay.rel_value);
  s->flow_delay_from_other_peer =
      GNUNET_TIME_relative_to_absolute (flow_delay);

  ack = (const struct GNUNET_MessageHeader *) &udp_ack[1];
  if (ntohs (ack->size) !=
      ntohs (msg->size) - sizeof (struct UDP_ACK_Message))
  {
    GNUNET_break_op (0);
    return;
  }

  if (GNUNET_OK != GNUNET_FRAGMENT_process_ack (s->frag_ctx->frag, ack))
  {
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "UDP processes %u-byte acknowledgement from `%s' at `%s'\n",
       (unsigned int) ntohs (msg->size), GNUNET_i2s (&udp_ack->sender),
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen));
#endif
    return;
  }

#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "FULL MESSAGE ACKed\n",
       (unsigned int) ntohs (msg->size), GNUNET_i2s (&udp_ack->sender),
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen));
#endif
  s->last_expected_delay = GNUNET_FRAGMENT_context_destroy (s->frag_ctx->frag);

  struct UDPMessageWrapper * udpw = plugin->msg_head;
  while (udpw!= NULL)
  {
    if ((udpw->frag_ctx != NULL) && (udpw->frag_ctx == s->frag_ctx))
    {
      GNUNET_CONTAINER_DLL_remove(plugin->msg_head, plugin->msg_tail, udpw);
      GNUNET_free (udpw);
    }
    udpw = udpw->next;
  }

  if (s->frag_ctx->cont != NULL)
    s->frag_ctx->cont
    (s->frag_ctx->cont_cls, &udp_ack->sender, GNUNET_OK);
  GNUNET_free (s->frag_ctx);
  s->frag_ctx = NULL;
  return;
}

static void read_process_fragment (struct Plugin *plugin,
    const struct GNUNET_MessageHeader *msg,
    char *addr,
    socklen_t fromlen)
{
  struct DefragContext *d_ctx;
  struct GNUNET_TIME_Absolute now;
  struct FindReceiveContext frc;


  frc.rc = NULL;
  frc.addr = (const struct sockaddr *) addr;
  frc.addr_len = fromlen;

#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG, "UDP processes %u-byte fragment from `%s'\n",
       (unsigned int) ntohs (msg->size),
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen));
#endif

  /* Lookup existing receive context for this address */
  GNUNET_CONTAINER_heap_iterate (plugin->defrag_ctxs,
                                 &find_receive_context,
                                 &frc);
  now = GNUNET_TIME_absolute_get ();
  d_ctx = frc.rc;

  if (d_ctx == NULL)
  {
    /* Create a new defragmentation context */
    d_ctx = GNUNET_malloc (sizeof (struct DefragContext) + fromlen);
    memcpy (&d_ctx[1], addr, fromlen);
    d_ctx->src_addr = (const struct sockaddr *) &d_ctx[1];
    d_ctx->addr_len = fromlen;
    d_ctx->plugin = plugin;
    d_ctx->defrag =
        GNUNET_DEFRAGMENT_context_create (plugin->env->stats, UDP_MTU,
                                          UDP_MAX_MESSAGES_IN_DEFRAG, d_ctx,
                                          &fragment_msg_proc, &ack_proc);
    d_ctx->hnode =
        GNUNET_CONTAINER_heap_insert (plugin->defrag_ctxs, d_ctx,
                                      (GNUNET_CONTAINER_HeapCostType)
                                      now.abs_value);
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Created new defragmentation context for %u-byte fragment from `%s'\n",
       (unsigned int) ntohs (msg->size),
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen));
#endif
  }
  else
  {
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Found existing defragmentation context for %u-byte fragment from `%s'\n",
       (unsigned int) ntohs (msg->size),
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen));
#endif
  }

  if (GNUNET_OK == GNUNET_DEFRAGMENT_process_fragment (d_ctx->defrag, msg))
  {
    /* keep this 'rc' from expiring */
    GNUNET_CONTAINER_heap_update_cost (plugin->defrag_ctxs, d_ctx->hnode,
                                       (GNUNET_CONTAINER_HeapCostType)
                                       now.abs_value);
  }
  if (GNUNET_CONTAINER_heap_get_size (plugin->defrag_ctxs) >
      UDP_MAX_SENDER_ADDRESSES_WITH_DEFRAG)
  {
    /* remove 'rc' that was inactive the longest */
    d_ctx = GNUNET_CONTAINER_heap_remove_root (plugin->defrag_ctxs);
    GNUNET_assert (NULL != d_ctx);
    GNUNET_DEFRAGMENT_context_destroy (d_ctx->defrag);
    GNUNET_free (d_ctx);
  }
}

/**
 * Read and process a message from the given socket.
 *
 * @param plugin the overall plugin
 * @param rsock socket to read from
 */
static void
udp_select_read (struct Plugin *plugin, struct GNUNET_NETWORK_Handle *rsock)
{
  socklen_t fromlen;
  char addr[32];
  char buf[65536];
  ssize_t size;
  const struct GNUNET_MessageHeader *msg;

  fromlen = sizeof (addr);
  memset (&addr, 0, sizeof (addr));
  size = GNUNET_NETWORK_socket_recvfrom (rsock, buf, sizeof (buf),
                                      (struct sockaddr *) &addr, &fromlen);

  if (size < sizeof (struct GNUNET_MessageHeader))
  {
    GNUNET_break_op (0);
    return;
  }
  msg = (const struct GNUNET_MessageHeader *) buf;

  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "UDP received %u-byte message from `%s' type %i\n", (unsigned int) size,
       GNUNET_a2s ((const struct sockaddr *) addr, fromlen), ntohs (msg->type));

  if (size != ntohs (msg->size))
  {
    GNUNET_break_op (0);
    return;
  }

  switch (ntohs (msg->type))
  {
  case GNUNET_MESSAGE_TYPE_TRANSPORT_BROADCAST_BEACON:
    udp_broadcast_receive (plugin, &buf, size, addr, fromlen);
    return;

  case GNUNET_MESSAGE_TYPE_TRANSPORT_UDP_MESSAGE:
    read_process_msg (plugin, msg, addr, fromlen);
    return;

  case GNUNET_MESSAGE_TYPE_TRANSPORT_UDP_ACK:
    read_process_ack (plugin, msg, addr, fromlen);;
    return;

  case GNUNET_MESSAGE_TYPE_FRAGMENT:
    read_process_fragment (plugin, msg, addr, fromlen);
    return;

  default:
    GNUNET_break_op (0);
    return;
  }
}

size_t
udp_select_send (struct Plugin *plugin)
{
  ssize_t sent;
  size_t slen;
  struct GNUNET_TIME_Absolute max;
  struct GNUNET_TIME_Absolute ;

  struct UDPMessageWrapper *udpw = plugin->msg_head;
  const struct sockaddr * sa = udpw->session->sock_addr;

  max = GNUNET_TIME_absolute_max(udpw->timeout, GNUNET_TIME_absolute_get());

  while (udpw != NULL)
  {
    if (max.abs_value != udpw->timeout.abs_value)
    {
      /* Message timed out */

      if (udpw->cont != NULL)
        udpw->cont (udpw->cont_cls, &udpw->session->target, GNUNET_SYSERR);
      if (udpw->frag_ctx != NULL)
      {
#if DEBUG_UDP
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Fragmented message for peer `%s' with size %u timed out\n",
            GNUNET_i2s(&udpw->session->target), udpw->frag_ctx->bytes_to_send);
#endif
        udpw->session->last_expected_delay = GNUNET_FRAGMENT_context_destroy(udpw->frag_ctx->frag);
        GNUNET_free (udpw->frag_ctx);
        udpw->session->frag_ctx = NULL;
      }
      else
      {
#if DEBUG_UDP
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Message for peer `%s' with size %u timed out\n",
            GNUNET_i2s(&udpw->session->target), udpw->msg_size);
#endif
      }

      GNUNET_CONTAINER_DLL_remove(plugin->msg_head, plugin->msg_tail, udpw);
      GNUNET_free (udpw);
      udpw = plugin->msg_head;
    }
    else
    {
      struct GNUNET_TIME_Relative delta = GNUNET_TIME_absolute_get_remaining (udpw->session->flow_delay_from_other_peer);
      if (delta.rel_value == 0)
      {
        /* this message is not delayed */
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Message for peer `%s' (%u bytes) is not delayed \n",
            GNUNET_i2s(&udpw->session->target), udpw->msg_size);
        break;
      }
      else
      {
        /* this message is delayed, try next */
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Message for peer `%s' (%u bytes) is delayed for %llu \n",
            GNUNET_i2s(&udpw->session->target), udpw->msg_size,
            delta);
        udpw = udpw->next;
      }
    }

  }

  if (udpw == NULL)
  {
    /* No message left */
    return 0;
  }

  switch (sa->sa_family)
  {
  case AF_INET:
    if (NULL == plugin->sockv4)
      return 0;
    sent =
        GNUNET_NETWORK_socket_sendto (plugin->sockv4, udpw->udp, udpw->msg_size,
                                      sa, slen = sizeof (struct sockaddr_in));
    break;
  case AF_INET6:
    if (NULL == plugin->sockv6)
      return 0;
    sent =
        GNUNET_NETWORK_socket_sendto (plugin->sockv6, udpw->udp, udpw->msg_size,
                                      sa, slen = sizeof (struct sockaddr_in6));
    break;
  default:
    GNUNET_break (0);
    return 0;
  }
  if (GNUNET_SYSERR == sent)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "sendto");
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "UDP transmitted %u-byte message to %s (%d: %s)\n",
         (unsigned int) (udpw->msg_size), GNUNET_a2s (sa, slen), (int) sent,
         (sent < 0) ? STRERROR (errno) : "ok");
    if (udpw->cont != NULL)
      udpw->cont (udpw->cont_cls, &udpw->session->target, GNUNET_SYSERR);
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "UDP transmitted %u-byte message to %s (%d: %s)\n",
       (unsigned int) (udpw->msg_size), GNUNET_a2s (sa, slen), (int) sent,
       (sent < 0) ? STRERROR (errno) : "ok");

  /* This was just a message fragment */
  if (udpw->frag_ctx != NULL)
  {
    GNUNET_FRAGMENT_context_transmission_done (udpw->frag_ctx->frag);
  }
  /* This was a complete message*/
  else
  {
    if (udpw->cont != NULL)
      udpw->cont (udpw->cont_cls, &udpw->session->target, GNUNET_OK);
  }

  GNUNET_CONTAINER_DLL_remove(plugin->msg_head, plugin->msg_tail, udpw);
  GNUNET_free (udpw);

  return sent;
}

/**
 * We have been notified that our readset has something to read.  We don't
 * know which socket needs to be read, so we have to check each one
 * Then reschedule this function to be called again once more is available.
 *
 * @param cls the plugin handle
 * @param tc the scheduling context (for rescheduling this function again)
 */
static void
udp_plugin_select (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct Plugin *plugin = cls;

  plugin->select_task = GNUNET_SCHEDULER_NO_TASK;
  if ((tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN) != 0)
    return;

  if ((tc->reason & GNUNET_SCHEDULER_REASON_READ_READY) != 0)
  {
    if ((NULL != plugin->sockv4) &&
      (GNUNET_NETWORK_fdset_isset (tc->read_ready, plugin->sockv4)))
        udp_select_read (plugin, plugin->sockv4);
    if ((NULL != plugin->sockv6) &&
      (GNUNET_NETWORK_fdset_isset (tc->read_ready, plugin->sockv6)))
        udp_select_read (plugin, plugin->sockv6);
  }

  if ((tc->reason & GNUNET_SCHEDULER_REASON_WRITE_READY) != 0)
  {
    if (plugin->msg_head != NULL)
      udp_select_send (plugin);
  }

  plugin->select_task = GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
                                   GNUNET_SCHEDULER_NO_TASK,
                                   GNUNET_TIME_UNIT_FOREVER_REL, plugin->rs,
                                   plugin->ws, &udp_plugin_select, plugin);

}


static int
setup_sockets (struct Plugin *plugin, struct sockaddr_in6 *serverAddrv6, struct sockaddr_in *serverAddrv4)
{
  int tries;
  int sockets_created = 0;
  struct sockaddr *serverAddr;
  struct sockaddr *addrs[2];
  socklen_t addrlens[2];
  socklen_t addrlen;

  /* Create IPv6 socket */
  if (plugin->enable_ipv6 == GNUNET_YES)
  {
    plugin->sockv6 = GNUNET_NETWORK_socket_create (PF_INET6, SOCK_DGRAM, 0);
    if (NULL == plugin->sockv6)
    {
      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING, "socket");
    }
    else
    {
#if HAVE_SOCKADDR_IN_SIN_LEN
      serverAddrv6.sin6_len = sizeof (serverAddrv6);
#endif
      serverAddrv6->sin6_family = AF_INET6;
      serverAddrv6->sin6_addr = in6addr_any;
      serverAddrv6->sin6_port = htons (plugin->port);
      addrlen = sizeof (struct sockaddr_in6);
      serverAddr = (struct sockaddr *) serverAddrv6;
#if DEBUG_UDP
      LOG (GNUNET_ERROR_TYPE_DEBUG, "Binding to IPv6 port %d\n",
           ntohs (serverAddrv6->sin6_port));
#endif
      tries = 0;
      while (GNUNET_NETWORK_socket_bind (plugin->sockv6, serverAddr, addrlen) !=
             GNUNET_OK)
      {
        serverAddrv6->sin6_port = htons (GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG, 33537) + 32000);        /* Find a good, non-root port */
#if DEBUG_UDP
        LOG (GNUNET_ERROR_TYPE_DEBUG,
             "IPv6 Binding failed, trying new port %d\n",
             ntohs (serverAddrv6->sin6_port));
#endif
        tries++;
        if (tries > 10)
        {
          GNUNET_NETWORK_socket_close (plugin->sockv6);
          plugin->sockv6 = NULL;
          break;
        }
      }
      if (plugin->sockv6 != NULL)
      {
#if DEBUG_UDP
        LOG (GNUNET_ERROR_TYPE_DEBUG,
             "IPv6 socket created on port %d\n",
             ntohs (serverAddrv6->sin6_port));
#endif
        addrs[sockets_created] = (struct sockaddr *) serverAddrv6;
        addrlens[sockets_created] = sizeof (struct sockaddr_in6);
        sockets_created++;
      }
    }
  }

  /* Create IPv4 socket */
  plugin->sockv4 = GNUNET_NETWORK_socket_create (PF_INET, SOCK_DGRAM, 0);
  if (NULL == plugin->sockv4)
  {
    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING, "socket");
  }
  else
  {
#if HAVE_SOCKADDR_IN_SIN_LEN
    serverAddrv4.sin_len = sizeof (serverAddrv4);
#endif
    serverAddrv4->sin_family = AF_INET;
    serverAddrv4->sin_addr.s_addr = INADDR_ANY;
    serverAddrv4->sin_port = htons (plugin->port);
    addrlen = sizeof (struct sockaddr_in);
    serverAddr = (struct sockaddr *) serverAddrv4;

#if DEBUG_UDP
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Binding to IPv4 port %d\n",
         ntohs (serverAddrv4->sin_port));
#endif
    tries = 0;
    while (GNUNET_NETWORK_socket_bind (plugin->sockv4, serverAddr, addrlen) !=
           GNUNET_OK)
    {
      serverAddrv4->sin_port = htons (GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_STRONG, 33537) + 32000);   /* Find a good, non-root port */
#if DEBUG_UDP
      LOG (GNUNET_ERROR_TYPE_DEBUG, "IPv4 Binding failed, trying new port %d\n",
           ntohs (serverAddrv4->sin_port));
#endif
      tries++;
      if (tries > 10)
      {
        GNUNET_NETWORK_socket_close (plugin->sockv4);
        plugin->sockv4 = NULL;
        break;
      }
    }
    if (plugin->sockv4 != NULL)
    {
      addrs[sockets_created] = (struct sockaddr *) serverAddrv4;
      addrlens[sockets_created] = sizeof (struct sockaddr_in);
      sockets_created++;
    }
  }

  /* Create file descriptors */
  plugin->rs = GNUNET_NETWORK_fdset_create ();
  plugin->ws = GNUNET_NETWORK_fdset_create ();
  GNUNET_NETWORK_fdset_zero (plugin->rs);
  GNUNET_NETWORK_fdset_zero (plugin->ws);
  if (NULL != plugin->sockv4)
  {
    GNUNET_NETWORK_fdset_set (plugin->rs, plugin->sockv4);
    GNUNET_NETWORK_fdset_set (plugin->ws, plugin->sockv4);
  }
  if (NULL != plugin->sockv6)
  {
    GNUNET_NETWORK_fdset_set (plugin->rs, plugin->sockv6);
    GNUNET_NETWORK_fdset_set (plugin->ws, plugin->sockv6);
  }

  if (sockets_created == 0)
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, _("Failed to open UDP sockets\n"));

  plugin->select_task =
      GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
                                   GNUNET_SCHEDULER_NO_TASK,
                                   GNUNET_TIME_UNIT_FOREVER_REL, plugin->rs,
                                   plugin->ws, &udp_plugin_select, plugin);

  plugin->nat = GNUNET_NAT_register (plugin->env->cfg,
                           GNUNET_NO, plugin->port,
                           sockets_created,
                           (const struct sockaddr **) addrs, addrlens,
                           &udp_nat_port_map_callback, NULL, plugin);

  return sockets_created;
}


/**
 * The exported method. Makes the core api available via a global and
 * returns the udp transport API.
 *
 * @param cls our 'struct GNUNET_TRANSPORT_PluginEnvironment'
 * @return our 'struct GNUNET_TRANSPORT_PluginFunctions'
 */
void *
libgnunet_plugin_transport_udp_init (void *cls)
{
  struct GNUNET_TRANSPORT_PluginEnvironment *env = cls;
  struct GNUNET_TRANSPORT_PluginFunctions *api;
  struct Plugin *plugin;

  unsigned long long port;
  unsigned long long aport;
  unsigned long long broadcast;
  unsigned long long udp_max_bps;
  unsigned long long enable_v6;
  char * bind4_address;
  char * bind6_address;
  struct GNUNET_TIME_Relative interval;

  struct sockaddr_in serverAddrv4;
  struct sockaddr_in6 serverAddrv6;

  int res;

  /* Get port number */
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-udp", "PORT",
                                             &port))
    port = 2086;
  if (GNUNET_OK !=
      GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-udp",
                                             "ADVERTISED_PORT", &aport))
    aport = port;
  if (port > 65535)
  {
    LOG (GNUNET_ERROR_TYPE_WARNING,
         _("Given `%s' option is out of range: %llu > %u\n"), "PORT", port,
         65535);
    return NULL;
  }

  /* Protocols */
  if ((GNUNET_YES ==
       GNUNET_CONFIGURATION_get_value_yesno (env->cfg, "nat",
                                             "DISABLEV6")))
  {
    enable_v6 = GNUNET_NO;
  }
  else
    enable_v6 = GNUNET_YES;


  /* Addresses */
  memset (&serverAddrv6, 0, sizeof (serverAddrv6));
  memset (&serverAddrv4, 0, sizeof (serverAddrv4));

  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_get_value_string (env->cfg, "transport-udp",
                                             "BINDTO", &bind4_address))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Binding udp plugin to specific address: `%s'\n",
         bind4_address);
    if (1 != inet_pton (AF_INET, bind4_address, &serverAddrv4.sin_addr))
    {
      GNUNET_free (bind4_address);
      return NULL;
    }
  }

  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_get_value_string (env->cfg, "transport-udp",
                                             "BINDTO6", &bind6_address))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Binding udp plugin to specific address: `%s'\n",
         bind6_address);
    if (1 !=
        inet_pton (AF_INET6, bind6_address, &serverAddrv6.sin6_addr))
    {
      LOG (GNUNET_ERROR_TYPE_ERROR, _("Invalid IPv6 address: `%s'\n"),
           bind6_address);
      GNUNET_free_non_null (bind4_address);
      GNUNET_free (bind6_address);
      return NULL;
    }
  }


  /* Enable neighbour discovery */
  broadcast = GNUNET_CONFIGURATION_get_value_yesno (env->cfg, "transport-udp",
                                            "BROADCAST");
  if (broadcast == GNUNET_SYSERR)
    broadcast = GNUNET_NO;

  if (GNUNET_SYSERR == GNUNET_CONFIGURATION_get_value_time (env->cfg, "transport-udp",
                                           "BROADCAST_INTERVAL", &interval))
  {
    interval = GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 10);
  }

  /* Maximum datarate */
  if (GNUNET_OK != GNUNET_CONFIGURATION_get_value_number (env->cfg, "transport-udp",
                                             "MAX_BPS", &udp_max_bps))
  {
    udp_max_bps = 1024 * 1024 * 50;     /* 50 MB/s == infinity for practical purposes */
  }

  plugin = GNUNET_malloc (sizeof (struct Plugin));
  api = GNUNET_malloc (sizeof (struct GNUNET_TRANSPORT_PluginFunctions));

  GNUNET_BANDWIDTH_tracker_init (&plugin->tracker,
                                 GNUNET_BANDWIDTH_value_init ((uint32_t)udp_max_bps), 30);


  plugin->sessions = GNUNET_CONTAINER_multihashmap_create (10);
  plugin->defrag_ctxs = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
  plugin->mst = GNUNET_SERVER_mst_create (&process_inbound_tokenized_messages, plugin);
  plugin->port = port;
  plugin->aport = aport;
  plugin->broadcast_interval = interval;
  plugin->enable_ipv6 = enable_v6;
  plugin->env = env;

  api->cls = plugin;
  api->send = NULL;
  api->disconnect = &udp_disconnect;
  api->address_pretty_printer = &udp_plugin_address_pretty_printer;
  api->address_to_string = &udp_address_to_string;
  api->check_address = &udp_plugin_check_address;
  api->get_session = &udp_plugin_get_session;
  api->send = &udp_plugin_send_wrapper;
  api->send_with_session = &udp_plugin_send;

  LOG (GNUNET_ERROR_TYPE_DEBUG, "Setting up sockets\n");
  res = setup_sockets (plugin, &serverAddrv6, &serverAddrv4);
  if ((res == 0) || ((plugin->sockv4 == NULL) && (plugin->sockv6 == NULL)))
  {
    LOG (GNUNET_ERROR_TYPE_ERROR, "Failed to create network sockets, plugin failed\n");
    GNUNET_free (plugin);
    GNUNET_free (api);
    return NULL;
  }

  LOG (GNUNET_ERROR_TYPE_DEBUG, "Starting broadcasting\n");
  if (broadcast == GNUNET_YES)
    setup_broadcast (plugin, &serverAddrv6, &serverAddrv4);


  GNUNET_free_non_null (bind4_address);
  GNUNET_free_non_null (bind6_address);
  return api;
}

int heap_cleanup_iterator (void *cls,
                          struct GNUNET_CONTAINER_HeapNode *
                          node, void *element,
                          GNUNET_CONTAINER_HeapCostType
                          cost)
{
  struct DefragContext * d_ctx = element;

  GNUNET_CONTAINER_heap_remove_node (node);
  GNUNET_DEFRAGMENT_context_destroy(d_ctx->defrag);
  GNUNET_free (d_ctx);

  return GNUNET_YES;
}


/**
 * The exported method. Makes the core api available via a global and
 * returns the udp transport API.
 *
 * @param cls our 'struct GNUNET_TRANSPORT_PluginEnvironment'
 * @return our 'struct GNUNET_TRANSPORT_PluginFunctions'
 */
void *
libgnunet_plugin_transport_udp_done (void *cls)
{
  struct GNUNET_TRANSPORT_PluginFunctions *api = cls;
  struct Plugin *plugin = api->cls;
  stop_broadcast (plugin);

  if (plugin->select_task != GNUNET_SCHEDULER_NO_TASK)
  {
    GNUNET_SCHEDULER_cancel (plugin->select_task);
    plugin->select_task = GNUNET_SCHEDULER_NO_TASK;
  }

  /* Closing sockets */
  if (plugin->sockv4 != NULL)
  {
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (plugin->sockv4));
    plugin->sockv4 = NULL;
  }
  if (plugin->sockv6 != NULL)
  {
    GNUNET_break (GNUNET_OK == GNUNET_NETWORK_socket_close (plugin->sockv6));
    plugin->sockv6 = NULL;
  }
  GNUNET_NETWORK_fdset_destroy (plugin->rs);
  GNUNET_NETWORK_fdset_destroy (plugin->ws);
  GNUNET_NAT_unregister (plugin->nat);

  if (plugin->defrag_ctxs != NULL)
  {
    GNUNET_CONTAINER_heap_iterate(plugin->defrag_ctxs,
        heap_cleanup_iterator, NULL);
    GNUNET_CONTAINER_heap_destroy(plugin->defrag_ctxs);
    plugin->defrag_ctxs = NULL;
  }
  if (plugin->mst != NULL)
  {
    GNUNET_SERVER_mst_destroy(plugin->mst);
    plugin->mst = NULL;
  }

  /* Clean up leftover messages */
  struct UDPMessageWrapper *udpw = plugin->msg_head;
  while (udpw != NULL)
  {
    struct UDPMessageWrapper *tmp = udpw->next;
    GNUNET_CONTAINER_DLL_remove(plugin->msg_head, plugin->msg_tail, udpw);
    if (udpw->cont != NULL)
      udpw->cont (udpw->cont_cls, &udpw->session->target, GNUNET_SYSERR);
    GNUNET_free (udpw);
    udpw = tmp;
  }

  /* Clean up sessions */
#if DEBUG_UDP
  LOG (GNUNET_ERROR_TYPE_DEBUG,
       "Cleaning up sessions\n");
#endif
  GNUNET_CONTAINER_multihashmap_iterate (plugin->sessions, &disconnect_and_free_it, plugin);
  GNUNET_CONTAINER_multihashmap_destroy (plugin->sessions);

  plugin->nat = NULL;
  GNUNET_free (plugin);
  GNUNET_free (api);
  return NULL;
}


/* end of plugin_transport_udp.c */