polite.h

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/**
 * \file
 *         Header file for Polite Anonymous best effort local Broadcast (polite)
 * \author
 *         Adam Dunkels <adam@sics.se>
 */

/**
 * \addtogroup rime
 * @{
 */

/**
 * \defgroup rimepolite Polite anonymous best effort local broadcast
 * @{
 *
 * The polite module sends one local area broadcast packet within one
 * time interval. If a packet with the same header is received from a
 * neighbor within the interval, the packet is not sent.
 *
 * The polite primitive is a generalization of the polite gossip
 * algorithm from Trickle (Levis et al, NSDI 2004).  The polite gossip
 * algorithm is designed to reduce the total amount of packet
 * transmissions by not repeating a message that other nodes have
 * already sent.  The purpose of the polite broadcast primitive is to
 * avoid that multiple copies of a specific set of packet attributes
 * is sent on a specified logical channel in the local neighborhood
 * during a time interval.
 *
 * The polite broadcast primitive is useful for implementing broadcast
 * protocols that use, e.g., negative acknowledgements.  If many nodes
 * need to send the negative acknowledgement to a sender, it is enough
 * if only a single message is delivered to the sender.
 *
 * The upper layer protocol or application that uses the polite
 * broadcast primitive provides an interval time, and message along
 * with a list of packet attributes for which multiple copies should
 * be avoided.  The polite broadcast primitive stores the outgoing
 * message in a queue buffer, stores the list of packet attributes,
 * and sets up a timer.  The timer is set to a random time during the
 * second half of the interval time.
 *
 * During the first half of the time interval, the sender listens for
 * other transmissions.  If it hears a packet that matches the
 * attributes provided by the upper layer protocol or application, the
 * sender drops the packet.  The send timer has been set to a random
 * time some time during the second half of the interval.  When the
 * timer fires, and the sender has not yet heard a transmission of the
 * same packet attributes, the sender broadcasts its packet to all its
 * neighbors.
 *
 * The polite broadcast module does not add any packet attributes to
 * outgoing packets apart from those added by the upper layer.
 *
 * \section channels Channels
 *
 * The polite module uses 1 channel.
 *
 */

#ifndef POLITE_H_
#define POLITE_H_

#include "net/rime/abc.h"
#include "net/queuebuf.h"
#include "sys/ctimer.h"

struct polite_conn;

#define POLITE_ATTRIBUTES ABC_ATTRIBUTES

/**
 * \brief      A structure with callback functions for a polite connection.
 *
 *             This structure holds a list of callback functions used
 *             a a polite connection. The functions are called when
 *             events occur on the connection.
 *
 */
struct polite_callbacks {
  /**
   * Called when a packet is received on the connection.
   */
  void (* recv)(struct polite_conn *c);

  /**
   * Called when a packet is sent on the connection.
   */
  void (* sent)(struct polite_conn *c);

  /**
   * Called when a packet is dropped because a packet was heard from a
   * neighbor.
   */
  void (* dropped)(struct polite_conn *c);
};

/**
 * An opaque structure with no user-visible elements that holds the
 * state of a polite connection,
 */
struct polite_conn {
  struct abc_conn c;
  const struct polite_callbacks *cb;
  struct ctimer t;
  struct queuebuf *q;
  uint8_t hdrsize;
};

/**
 * \brief      Open a polite connection
 * \param c    A pointer to a struct polite_conn.
 * \param channel The channel number to be used for this connection
 * \param cb   A pointer to the callbacks used for this connection
 *
 *             This function opens a polite connection on the
 *             specified channel. The callbacks are called when a
 *             packet is received, or when another event occurs on the
 *             connection (see \ref "struct polite_callbacks").
 */
void polite_open(struct polite_conn *c, uint16_t channel,
                 const struct polite_callbacks *cb);

/**
 * \brief      Close a polite connection
 * \param c    A pointer to a struct polite_conn that has previously been opened with polite_open().
 *
 *             This function closes a polite connection that has
 *             previously been opened with polite_open().
 */
void polite_close(struct polite_conn *c);


/**
 * \brief      Send a packet on a polite connection.
 * \param c    A pointer to a struct polite_conn that has previously been opened with polite_open().
 * \param interval The timer interval in which the packet should be sent.
 * \param hdrsize The size of the header that should be unique within the time interval.
 *
 *             This function sends a packet from the packetbuf on the
 *             polite connection. The packet is sent some time during
 *             the time interval, but only if no other packet is
 *             received with the same header.
 *
 */
int  polite_send(struct polite_conn *c, clock_time_t interval, uint8_t hdrsize);

/**
 * \brief      Cancel a pending packet
 * \param c    A pointer to a struct polite_conn that has previously been opened with polite_open().
 *
 *             This function cancels a pending transmission that has
 *             previously been started with polite_send().
 */
void polite_cancel(struct polite_conn *c);

#endif /* POLITE_H_ */

/** @} */
/** @} */