nuttx/net/udp/udp.h

/****************************************************************************
 * net/udp/udp.h
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

#ifndef __NET_UDP_UDP_H
#define __NET_UDP_UDP_H

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <sys/socket.h>

#include <nuttx/queue.h>
#include <nuttx/semaphore.h>
#include <nuttx/net/ip.h>
#include <nuttx/net/net.h>
#include <nuttx/net/udp.h>
#include <nuttx/mm/iob.h>

#ifdef CONFIG_NET_UDP_NOTIFIER
#  include <nuttx/wqueue.h>
#endif

#if defined(CONFIG_NET_UDP) && !defined(CONFIG_NET_UDP_NO_STACK)

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define NET_UDP_HAVE_STACK 1

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
/* UDP write buffer dump macros */

#  ifdef CONFIG_DEBUG_FEATURES
#    define UDP_WBDUMP(msg,wrb,len,offset) \
       udp_wrbuffer_dump(msg,wrb,len,offset)
#  else
#    define UDP_WBDUMP(msg,wrb,len,offset)
#  endif
#endif

/* Allocate a new UDP data callback */

#define udp_callback_alloc(dev,conn) \
  devif_callback_alloc((dev), &(conn)->sconn.list, &(conn)->sconn.list_tail)
#define udp_callback_free(dev,conn,cb) \
  devif_conn_callback_free((dev), (cb), &(conn)->sconn.list, &(conn)->sconn.list_tail)

/* Definitions for the UDP connection struct flag field */

#define _UDP_FLAG_CONNECTMODE (1 << 0) /* Bit 0:  UDP connection-mode */

#define _UDP_ISCONNECTMODE(f) (((f) & _UDP_FLAG_CONNECTMODE) != 0)

/* This is a helper pointer for accessing the contents of the udp header */

#define UDPIPv4BUF ((FAR struct udp_hdr_s *)IPBUF(IPv4_HDRLEN))
#define UDPIPv6BUF ((FAR struct udp_hdr_s *)IPBUF(IPv6_HDRLEN))

/****************************************************************************
 * Public Type Definitions
 ****************************************************************************/

struct sockaddr;      /* Forward reference */
struct socket;        /* Forward reference */
struct net_driver_s;  /* Forward reference */
struct pollfd;        /* Forward reference */

/* Representation of a UDP connection */

struct devif_callback_s;  /* Forward reference */
struct udp_hdr_s;         /* Forward reference */

/* This is a container that holds the poll-related information */

struct udp_poll_s
{
  FAR struct udp_conn_s *conn;     /* Needed to handle loss of connection */
  FAR struct net_driver_s *dev;    /* Needed to free the callback structure */
  FAR struct pollfd *fds;          /* Needed to handle poll events */
  FAR struct devif_callback_s *cb; /* Needed to teardown the poll */
};

struct udp_conn_s
{
  /* Common prologue of all connection structures. */

  struct socket_conn_s sconn;

  /* UDP-specific content follows */

  union ip_binding_u u;   /* IP address binding */
  uint16_t lport;         /* Bound local port number (network byte order) */
  uint16_t rport;         /* Remote port number (network byte order) */
  uint8_t  flags;         /* See _UDP_FLAG_* definitions */
  uint8_t  domain;        /* IP domain: PF_INET or PF_INET6 */
  uint8_t  crefs;         /* Reference counts on this instance */

#if CONFIG_NET_RECV_BUFSIZE > 0
  int32_t  rcvbufs;       /* Maximum amount of bytes queued in recv */
#endif
#if CONFIG_NET_SEND_BUFSIZE > 0
  int32_t  sndbufs;       /* Maximum amount of bytes queued in send */
  sem_t    sndsem;        /* Semaphore signals send completion */
#endif
#ifdef CONFIG_NETDEV_RSS
  int      rcvcpu;        /* Last recvfrom cpuid */
#endif
  /* Read-ahead buffering.
   *
   *   readahead - An IOB chain where the UDP/IP read-ahead data is retained.
   */

  FAR struct iob_s *readahead;   /* Read-ahead buffering */

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
  /* Write buffering
   *
   *   write_q   - The queue of unsent I/O buffers.  The head of this
   *               list may be partially sent.  FIFO ordering.
   */

  sq_queue_t write_q;             /* Write buffering for UDP packets */
  FAR struct net_driver_s *dev;   /* Last device */

  /* Callback instance for UDP sendto() */

  FAR struct devif_callback_s *sndcb;
#endif

#if defined(CONFIG_NET_IGMP) || defined(CONFIG_NET_MLD)
  struct ip_mreqn mreq;
#endif

  /* The following is a list of poll structures of threads waiting for
   * socket events.
   */

  struct udp_poll_s pollinfo[CONFIG_NET_UDP_NPOLLWAITERS];

#ifdef CONFIG_NET_TIMESTAMP
  int timestamp; /* Nonzero when SO_TIMESTAMP is enabled */
#endif
};

/* This structure supports UDP write buffering.  It is simply a container
 * for a IOB list and associated destination address.
 */

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
struct udp_wrbuffer_s
{
  sq_entry_t wb_node;              /* Supports a singly linked list */
  struct sockaddr_storage wb_dest; /* Destination address */
  FAR struct iob_s *wb_iob;        /* Head of the I/O buffer chain */
};
#endif

/****************************************************************************
 * Public Data
 ****************************************************************************/

#ifdef __cplusplus
#  define EXTERN extern "C"
extern "C"
{
#else
#  define EXTERN extern
#endif

/****************************************************************************
 * Public Function Prototypes
 ****************************************************************************/

/****************************************************************************
 * Name: udp_initialize
 *
 * Description:
 *   Initialize the UDP connection structures.  Called once and only from
 *   the UIP layer.
 *
 ****************************************************************************/

void udp_initialize(void);

/****************************************************************************
 * Name: udp_alloc
 *
 * Description:
 *   Allocate a new, uninitialized UDP connection structure.  This is
 *   normally something done by the implementation of the socket() API
 *
 ****************************************************************************/

FAR struct udp_conn_s *udp_alloc(uint8_t domain);

/****************************************************************************
 * Name: udp_free
 *
 * Description:
 *   Free a UDP connection structure that is no longer in use. This should be
 *   done by the implementation of close().
 *
 ****************************************************************************/

void udp_free(FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: udp_active
 *
 * Description:
 *   Find a connection structure that is the appropriate
 *   connection to be used within the provided UDP/IP header
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

FAR struct udp_conn_s *udp_active(FAR struct net_driver_s *dev,
                                  FAR struct udp_conn_s *conn,
                                  FAR struct udp_hdr_s *udp);

/****************************************************************************
 * Name: udp_nextconn
 *
 * Description:
 *   Traverse the list of allocated UDP connections
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

FAR struct udp_conn_s *udp_nextconn(FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: udp_select_port
 *
 * Description:
 *   Select an unused port number.
 *
 *   NOTE that in principle this function could fail if there is no available
 *   port number.  There is no check for that case and it would actually
 *   in an infinite loop if that were the case.  In this simple, small UDP
 *   implementation, it is reasonable to assume that that error cannot happen
 *   and that a port number will always be available.
 *
 * Returned Value:
 *   Next available port number in host byte order, 0 for failure.
 *
 ****************************************************************************/

uint16_t udp_select_port(uint8_t domain, FAR union ip_binding_u *u);

/****************************************************************************
 * Name: udp_bind
 *
 * Description:
 *   This function implements the low-level parts of the standard UDP bind()
 *   operation.
 *
 * Assumptions:
 *   This function is called from normal user level code.
 *
 ****************************************************************************/

int udp_bind(FAR struct udp_conn_s *conn, FAR const struct sockaddr *addr);

/****************************************************************************
 * Name: udp_connect
 *
 * Description:
 *   This function simply assigns a remote address to UDP "connection"
 *   structure.  This function is called as part of the implementation of:
 *
 *   - connect().  If connect() is called for a SOCK_DGRAM socket, then
 *       this logic performs the moral equivalent of connect() operation
 *       for the UDP socket.
 *   - recvfrom() and sendto().  This function is called to set the
 *       remote address of the peer.
 *
 *   The function will automatically allocate an unused local port for the
 *   new connection if the socket is not yet bound to a local address.
 *   However, another port can be chosen by using the udp_bind() call,
 *   after the udp_connect() function has been called.
 *
 * Input Parameters:
 *   conn - A reference to UDP connection structure.  A value of NULL will
 *          disconnect from any previously connected address.
 *   addr - The address of the remote host.
 *
 * Assumptions:
 *   This function is called (indirectly) from user code.  Interrupts may
 *   be enabled.
 *
 ****************************************************************************/

int udp_connect(FAR struct udp_conn_s *conn,
                FAR const struct sockaddr *addr);

#if defined(CONFIG_NET_IGMP)
/****************************************************************************
 * Name: udp_leavegroup
 *
 * Description:
 *   This function leaves the multicast group to which the conn belongs.
 *
 * Input Parameters:
 *   conn - A reference to UDP connection structure.  A value of NULL will
 *          disconnect from any previously connected address.
 *
 * Assumptions:
 *   This function is called (indirectly) from user code.  Interrupts may
 *   be enabled.
 *
 ****************************************************************************/

void udp_leavegroup(FAR struct udp_conn_s *conn);
#else
#define udp_leavegroup(c)
#endif

/****************************************************************************
 * Name: udp_close
 *
 * Description:
 *   Break any current UDP connection
 *
 * Input Parameters:
 *   psock - An instance of the internal socket structure.
 *
 * Assumptions:
 *   Called from normal user-level logic
 *
 ****************************************************************************/

int udp_close(FAR struct socket *psock);

/****************************************************************************
 * Name: udp_ipv4_select
 *
 * Description:
 *   Configure to send or receive an UDP IPv4 packet
 *
 ****************************************************************************/

#ifdef CONFIG_NET_IPv4
void udp_ipv4_select(FAR struct net_driver_s *dev);
#endif

/****************************************************************************
 * Name: udp_ipv6_select
 *
 * Description:
 *   Configure to send or receive an UDP IPv6 packet
 *
 ****************************************************************************/

#ifdef CONFIG_NET_IPv6
void udp_ipv6_select(FAR struct net_driver_s *dev);
#endif

/****************************************************************************
 * Name: udp_poll
 *
 * Description:
 *   Poll a UDP "connection" structure for availability of TX data
 *
 * Input Parameters:
 *   dev  - The device driver structure to use in the send operation
 *   conn - The UDP "connection" to poll for TX data
 *
 * Returned Value:
 *   None
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

void udp_poll(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: psock_udp_cansend
 *
 * Description:
 *   psock_udp_cansend() returns a value indicating if a write to the socket
 *   would block.  It is still possible that the write may block if another
 *   write occurs first.
 *
 * Input Parameters:
 *   conn     A reference to UDP connection structure.
 *
 * Returned Value:
 *   -ENOSYS (Function not implemented, always have to wait to send).
 *
 * Assumptions:
 *   None
 *
 ****************************************************************************/

int psock_udp_cansend(FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: udp_send
 *
 * Description:
 *   Set-up to send a UDP packet
 *
 * Input Parameters:
 *   dev  - The device driver structure to use in the send operation
 *   conn - The UDP "connection" structure holding port information
 *
 * Returned Value:
 *   None
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

void udp_send(FAR struct net_driver_s *dev, FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: udp_setsockopt
 *
 * Description:
 *   udp_setsockopt() sets the UDP-protocol option specified by the
 *   'option' argument to the value pointed to by the 'value' argument for
 *   the socket specified by the 'psock' argument.
 *
 *   See <netinet/udp.h> for the a complete list of values of UDP protocol
 *   options.
 *
 * Input Parameters:
 *   psock     Socket structure of socket to operate on
 *   option    identifies the option to set
 *   value     Points to the argument value
 *   value_len The length of the argument value
 *
 * Returned Value:
 *   Returns zero (OK) on success.  On failure, it returns a negated errno
 *   value to indicate the nature of the error.  See psock_setcockopt() for
 *   the list of possible error values.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDPPROTO_OPTIONS
int udp_setsockopt(FAR struct socket *psock, int option,
                   FAR const void *value, socklen_t value_len);
#endif

/****************************************************************************
 * Name: udp_wrbuffer_initialize
 *
 * Description:
 *   Initialize the list of free write buffers
 *
 * Assumptions:
 *   Called once early initialization.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
void udp_wrbuffer_initialize(void);
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_alloc
 *
 * Description:
 *   Allocate a UDP write buffer by taking a pre-allocated buffer from
 *   the free list.  This function is called from UDP logic when a buffer
 *   of UDP data is about to sent
 *
 * Input Parameters:
 *   None
 *
 * Assumptions:
 *   Called from user logic with the network locked.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
struct udp_wrbuffer_s;
FAR struct udp_wrbuffer_s *udp_wrbuffer_alloc(void);
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_timedalloc
 *
 * Description:
 *   Allocate a UDP write buffer by taking a pre-allocated buffer from
 *   the free list.  This function is called from udp logic when a buffer
 *   of udp data is about to sent
 *   This function is wrapped version of udp_wrbuffer_alloc(),
 *   this wait will be terminated when the specified timeout expires.
 *
 * Input Parameters:
 *   timeout   - The relative time to wait until a timeout is declared.
 *
 * Assumptions:
 *   Called from user logic with the network locked.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
FAR struct udp_wrbuffer_s *udp_wrbuffer_timedalloc(unsigned int timeout);
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_tryalloc
 *
 * Description:
 *   Try to allocate a UDP write buffer by taking a pre-allocated buffer from
 *   the free list.  This function is called from UDP logic when a buffer
 *   of UDP data is about to be sent if the socket is non-blocking. Returns
 *   immediately if allocation fails.
 *
 * Input parameters:
 *   None
 *
 * Assumptions:
 *   Called from user logic with the network locked.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
#ifdef CONFIG_NET_JUMBO_FRAME
FAR struct udp_wrbuffer_s *udp_wrbuffer_tryalloc(int len);
#else
FAR struct udp_wrbuffer_s *udp_wrbuffer_tryalloc(void);
#endif
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_release
 *
 * Description:
 *   Release a UDP write buffer by returning the buffer to the free list.
 *   This function is called from user logic after it is consumed the
 *   buffered data.
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
void udp_wrbuffer_release(FAR struct udp_wrbuffer_s *wrb);
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_inqueue_size
 *
 * Description:
 *   Get the in-queued write buffer size from connection
 *
 * Input Parameters:
 *   conn - The UDP connection of interest
 *
 * Assumptions:
 *   Called from user logic with the network locked.
 *
 ****************************************************************************/

#if CONFIG_NET_SEND_BUFSIZE > 0
uint32_t udp_wrbuffer_inqueue_size(FAR struct udp_conn_s *conn);
#endif /* CONFIG_NET_SEND_BUFSIZE */

/****************************************************************************
 * Name: udp_wrbuffer_test
 *
 * Description:
 *   Check if there is room in the write buffer.  Does not reserve any space.
 *
 * Assumptions:
 *   None.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
int udp_wrbuffer_test(void);
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_wrbuffer_dump
 *
 * Description:
 *   Dump the contents of a write buffer.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_WRITE_BUFFERS
#ifdef CONFIG_DEBUG_FEATURES
void udp_wrbuffer_dump(FAR const char *msg, FAR struct udp_wrbuffer_s *wrb,
                       unsigned int len, unsigned int offset);
#else
#  define udp_wrbuffer_dump(msg,wrb)
#endif
#endif /* CONFIG_NET_UDP_WRITE_BUFFERS */

/****************************************************************************
 * Name: udp_ipv4_input
 *
 * Description:
 *   Handle incoming UDP input in an IPv4 packet
 *
 * Input Parameters:
 *   dev - The device driver structure containing the received UDP packet
 *
 * Returned Value:
 *   OK  The packet has been processed  and can be deleted
 *   ERROR Hold the packet and try again later. There is a listening socket
 *         but no receive in place to catch the packet yet.
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

#ifdef CONFIG_NET_IPv4
int udp_ipv4_input(FAR struct net_driver_s *dev);
#endif

/****************************************************************************
 * Name: udp_ipv6_input
 *
 * Description:
 *   Handle incoming UDP input in an IPv6 packet
 *
 * Input Parameters:
 *   dev   - The device driver structure containing the received UDP packet
 *   iplen - The size of the IPv6 header.  This may be larger than
 *           IPv6_HDRLEN the IPv6 header if IPv6 extension headers are
 *           present.
 *
 * Returned Value:
 *   OK  The packet has been processed  and can be deleted
 *   ERROR Hold the packet and try again later. There is a listening socket
 *         but no receive in place to catch the packet yet.
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

#ifdef CONFIG_NET_IPv6
int udp_ipv6_input(FAR struct net_driver_s *dev, unsigned int iplen);
#endif

/****************************************************************************
 * Name: udp_find_laddr_device
 *
 * Description:
 *   Select the network driver to use with the UDP transaction using the
 *   locally bound IP address.
 *
 * Input Parameters:
 *   conn - UDP connection structure (not currently used).
 *
 * Returned Value:
 *   A pointer to the network driver to use.  NULL is returned if driver is
 *   not bound to any local device.
 *
 ****************************************************************************/

FAR struct net_driver_s *udp_find_laddr_device(FAR struct udp_conn_s *conn);

/****************************************************************************
 * Name: udp_find_raddr_device
 *
 * Description:
 *   Select the network driver to use with the UDP transaction using the
 *   remote IP address.
 *
 * Input Parameters:
 *   conn - UDP connection structure (not currently used).
 *
 * Returned Value:
 *   A pointer to the network driver to use.
 *
 ****************************************************************************/

FAR struct net_driver_s *
udp_find_raddr_device(FAR struct udp_conn_s *conn,
                      FAR struct sockaddr_storage *remote);

/****************************************************************************
 * Name: udp_callback
 *
 * Description:
 *   Inform the application holding the UDP socket of a change in state.
 *
 * Returned Value:
 *   OK if packet has been processed, otherwise ERROR.
 *
 * Assumptions:
 *   Called from network stack logic with the network stack locked
 *
 ****************************************************************************/

uint16_t udp_callback(FAR struct net_driver_s *dev,
                      FAR struct udp_conn_s *conn, uint16_t flags);

/****************************************************************************
 * Name: psock_udp_recvfrom
 *
 * Description:
 *   Perform the recvfrom operation for a UDP SOCK_DGRAM
 *
 * Input Parameters:
 *   psock    Pointer to the socket structure for the SOCK_DRAM socket
 *   msg      Receive info and buffer for receive data
 *   flags    Receive flags
 *
 * Returned Value:
 *   On success, returns the number of characters received.  On  error,
 *   -errno is returned (see recvfrom for list of errnos).
 *
 * Assumptions:
 *
 ****************************************************************************/

ssize_t psock_udp_recvfrom(FAR struct socket *psock, FAR struct msghdr *msg,
                           int flags);

/****************************************************************************
 * Name: psock_udp_sendto
 *
 * Description:
 *   This function implements the UDP-specific logic of the standard
 *   sendto() socket operation.
 *
 * Input Parameters:
 *   psock    A pointer to a NuttX-specific, internal socket structure
 *   buf      Data to send
 *   len      Length of data to send
 *   flags    Send flags
 *   to       Address of recipient
 *   tolen    The length of the address structure
 *
 *   NOTE: All input parameters were verified by sendto() before this
 *   function was called.
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  On  error,
 *   a negated errno value is returned.  See the description in
 *   net/socket/sendto.c for the list of appropriate return value.
 *
 ****************************************************************************/

ssize_t psock_udp_sendto(FAR struct socket *psock,
                         FAR const void *buf, size_t len, int flags,
                         FAR const struct sockaddr *to, socklen_t tolen);

/****************************************************************************
 * Name: udp_pollsetup
 *
 * Description:
 *   Setup to monitor events on one UDP/IP socket
 *
 * Input Parameters:
 *   psock - The UDP/IP socket of interest
 *   fds   - The structure describing the events to be monitored, OR NULL if
 *           this is a request to stop monitoring events.
 *
 * Returned Value:
 *  0: Success; Negated errno on failure
 *
 ****************************************************************************/

int udp_pollsetup(FAR struct socket *psock, FAR struct pollfd *fds);

/****************************************************************************
 * Name: udp_pollteardown
 *
 * Description:
 *   Teardown monitoring of events on an UDP/IP socket
 *
 * Input Parameters:
 *   psock - The UDP/IP socket of interest
 *   fds   - The structure describing the events to be monitored, OR NULL if
 *           this is a request to stop monitoring events.
 *
 * Returned Value:
 *  0: Success; Negated errno on failure
 *
 ****************************************************************************/

int udp_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds);

/****************************************************************************
 * Name: udp_readahead_notifier_setup
 *
 * Description:
 *   Set up to perform a callback to the worker function when an UDP data
 *   is added to the read-ahead buffer.  The worker function will execute
 *   on the low priority worker thread.
 *
 * Input Parameters:
 *   worker - The worker function to execute on the low priority work
 *            queue when data is available in the UDP read-ahead buffer.
 *   conn  - The UDP connection where read-ahead data is needed.
 *   arg    - A user-defined argument that will be available to the worker
 *            function when it runs.
 *
 * Returned Value:
 *   > 0   - The notification is in place.  The returned value is a key that
 *           may be used later in a call to udp_notifier_teardown().
 *   == 0  - There is already buffered read-ahead data.  No notification
 *           will be provided.
 *   < 0   - An unexpected error occurred and no notification will occur.
 *           The returned value is a negated errno value that indicates the
 *           nature of the failure.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_NOTIFIER
int udp_readahead_notifier_setup(worker_t worker,
                                 FAR struct udp_conn_s *conn,
                                 FAR void *arg);
#endif

/****************************************************************************
 * Name: udp_writebuffer_notifier_setup
 *
 * Description:
 *   Set up to perform a callback to the worker function when an UDP write
 *   buffer is emptied.  The worker function will execute on the high
 *   priority worker thread.
 *
 * Input Parameters:
 *   worker - The worker function to execute on the low priority work
 *            queue when data is available in the UDP read-ahead buffer.
 *   conn   - The UDP connection where read-ahead data is needed.
 *   arg    - A user-defined argument that will be available to the worker
 *            function when it runs.
 *
 * Returned Value:
 *   > 0   - The notification is in place.  The returned value is a key that
 *           may be used later in a call to udp_notifier_teardown().
 *   == 0  - There is already buffered read-ahead data.  No notification
 *           will be provided.
 *   < 0   - An unexpected error occurred and no notification will occur.
 *           The returned value is a negated errno value that indicates the
 *           nature of the failure.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_NOTIFIER
int udp_writebuffer_notifier_setup(worker_t worker,
                                   FAR struct udp_conn_s *conn,
                                   FAR void *arg);
#endif

/****************************************************************************
 * Name: udp_notifier_teardown
 *
 * Description:
 *   Eliminate a UDP read-ahead notification previously setup by
 *   udp_readahead_notifier_setup().  This function should only be called if
 *   the notification should be aborted prior to the notification.  The
 *   notification will automatically be torn down after the notification.
 *
 * Input Parameters:
 *   key - The key value returned from a previous call to
 *         udp_readahead_notifier_setup().
 *
 * Returned Value:
 *   None.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_NOTIFIER
void udp_notifier_teardown(int key);
#endif

/****************************************************************************
 * Name: udp_readahead_signal
 *
 * Description:
 *   Read-ahead data has been buffered.  Notify all threads waiting for
 *   read-ahead data to become available.
 *
 *   When read-ahead data becomes available, *all* of the workers waiting
 *   for read-ahead data will be executed.  If there are multiple workers
 *   waiting for read-ahead data then only the first to execute will get the
 *   data. Others will need to call udp_readahead_notifier_setup once again.
 *
 * Input Parameters:
 *   conn  - The UDP connection where read-ahead data was just buffered.
 *
 * Returned Value:
 *   None.
 *
 ****************************************************************************/

#ifdef CONFIG_NET_UDP_NOTIFIER
void udp_readahead_signal(FAR struct udp_conn_s *conn);
#endif

/****************************************************************************
 * Name: udp_writebuffer_signal
 *
 * Description:
 *   All buffer Tx data has been sent.  Signal all threads waiting for the
 *   write buffers to become empty.
 *
 *   When write buffer becomes empty, *all* of the workers waiting
 *   for that event data will be executed.  If there are multiple workers
 *   waiting for read-ahead data then only the first to execute will get the
 *   data.  Others will need to call udp_writebuffer_notifier_setup() once
 *   again.
 *
 * Input Parameters:
 *   conn  - The UDP connection where read-ahead data was just buffered.
 *
 * Returned Value:
 *   None.
 *
 ****************************************************************************/

#if defined(CONFIG_NET_UDP_WRITE_BUFFERS) && defined(CONFIG_NET_UDP_NOTIFIER)
void udp_writebuffer_signal(FAR struct udp_conn_s *conn);
#endif

/****************************************************************************
 * Name: udp_txdrain
 *
 * Description:
 *   Wait for all write buffers to be sent (or for a timeout to occur).
 *
 * Input Parameters:
 *   psock   - An instance of the internal socket structure.
 *   timeout - The relative time when the timeout will occur
 *
 * Returned Value:
 *   Zero (OK) is returned on success; a negated errno value is returned
 *   on any failure.
 *
 ****************************************************************************/

#if defined(CONFIG_NET_UDP_WRITE_BUFFERS) && defined(CONFIG_NET_UDP_NOTIFIER)
int udp_txdrain(FAR struct socket *psock, unsigned int timeout);
#else
#  define udp_txdrain(conn, timeout) (0)
#endif

/****************************************************************************
 * Name: udp_ioctl
 *
 * Description:
 *   This function performs udp specific ioctl() operations.
 *
 * Parameters:
 *   conn     The TCP connection of interest
 *   cmd      The ioctl command
 *   arg      The argument of the ioctl cmd
 *
 ****************************************************************************/

int udp_ioctl(FAR struct udp_conn_s *conn, int cmd, unsigned long arg);

/****************************************************************************
 * Name: udp_sendbuffer_notify
 *
 * Description:
 *   Notify the send buffer semaphore
 *
 * Input Parameters:
 *   conn - The UDP connection of interest
 *
 * Assumptions:
 *   Called from user logic with the network locked.
 *
 ****************************************************************************/

#if CONFIG_NET_SEND_BUFSIZE > 0
void udp_sendbuffer_notify(FAR struct udp_conn_s *conn);
#endif /* CONFIG_NET_SEND_BUFSIZE */

/****************************************************************************
 * Name: udpip_hdrsize
 *
 * Description:
 *   Get the total size of L3 and L4 UDP header
 *
 * Input Parameters:
 *   conn     The connection structure associated with the socket
 *
 * Returned Value:
 *   the total size of L3 and L4 TCP header
 *
 ****************************************************************************/

uint16_t udpip_hdrsize(FAR struct udp_conn_s *conn);

#undef EXTERN
#ifdef __cplusplus
}
#endif

#endif /* CONFIG_NET_UDP && !CONFIG_NET_UDP_NO_STACK */
#endif /* __NET_UDP_UDP_H */