net.h

/****************************************************************************
 * include/nuttx/net/net.h
 *
 *   Copyright (C) 2007, 2009-2014, 2016-2017 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

#ifndef __INCLUDE_NUTTX_NET_NET_H
#define __INCLUDE_NUTTX_NET_NET_H

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

#include <nuttx/config.h>
#ifdef CONFIG_NET

#include <sys/socket.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdarg.h>
#include <semaphore.h>

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

/* Most internal network OS interfaces are not available in the user space in
 * PROTECTED and KERNEL builds.  In that context, the corresponding
 * application network interfaces must be used.  The differences between the two
 * sets of interfaces are:  The internal OS interfaces (1) do not cause
 * cancellation points and (2) they do not modify the errno variable.
 *
 * This is only important when compiling libraries (libc or libnx) that are
 * used both by the OS (libkc.a and libknx.a) or by the applications
 * (libuc.a and libunx.a).  The that case, the correct interface must be
 * used for the build context.
 *
 * The interfaces accept(), read(), recv(), recvfrom(), write(), send(),
 * sendto() are all cancellation points.
 *
 * REVISIT:  These cancellation points are an issue and may cause
 * violations:  It use of these internally will cause the calling function
 * to become a cancellation points!
 */

#if defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__)
#  define _NX_SEND(s,b,l,f)         nx_send(s,b,l,f)
#  define _NX_RECV(s,b,l,f)         nx_recv(s,b,l,f)
#  define _NX_RECVFROM(s,b,l,f,a,n) nx_recvfrom(s,b,l,f,a,n)
#  define _NX_GETERRNO(r)           (-(r))
#  define _NX_GETERRVAL(r)          (r)
#else
#  define _NX_SEND(s,b,l,f)         send(s,b,l,f)
#  define _NX_RECV(s,b,l,f)         recv(s,b,l,f)
#  define _NX_RECVFROM(s,b,l,f,a,n) recvfrom(s,b,l,f,a,n)
#  define _NX_GETERRNO(r)           errno
#  define _NX_GETERRVAL(r)          (-errno)
#endif

/* Socket descriptors are the index into the TCB sockets list, offset by the
 * following amount. This offset is used to distinguish file descriptors from
 * socket descriptors
 */

#ifdef CONFIG_NFILE_DESCRIPTORS
# define __SOCKFD_OFFSET CONFIG_NFILE_DESCRIPTORS
#else
# define __SOCKFD_OFFSET 0
#endif

/* Capabilities of a socket */

#define SOCKCAP_NONBLOCKING (1 << 0)  /* Bit 0: Socket supports non-blocking
                                       *        operation. */

/****************************************************************************
 * Public Types
 ****************************************************************************/

/* Data link layer type.  This type is used with netdev_register in order to
 * identify the type of the network driver.
 */

enum net_lltype_e
{
  NET_LL_ETHERNET = 0, /* Ethernet */
  NET_LL_LOOPBACK,     /* Local loopback */
  NET_LL_SLIP,         /* Serial Line Internet Protocol (SLIP) */
  NET_LL_TUN,          /* TUN Virtual Network Device */
  NET_LL_BLUETOOTH,    /* Bluetooth */
  NET_LL_IEEE80211,    /* IEEE 802.11 */
  NET_LL_IEEE802154,   /* IEEE 802.15.4 MAC */
  NET_LL_PKTRADIO      /* Non-standard packet radio */
};

/* This defines a bitmap big enough for one bit for each socket option */

typedef uint16_t sockopt_t;

/* This defines the storage size of a timeout value.  This effects only
 * range of supported timeout values.  With an LSB in seciseconds, the
 * 16-bit maximum of 65535 corresponds to 1 hr 49 min 13.5 sec at decisecond
 * resolution.
 */

typedef uint16_t socktimeo_t;

/* This type defines the type of the socket capabilities set */

typedef uint8_t sockcaps_t;

/* This callbacks are socket operations that may be performed on a socket of
 * a given address family.
 */

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

struct sock_intf_s
{
  CODE int        (*si_setup)(FAR struct socket *psock, int protocol);
  CODE sockcaps_t (*si_sockcaps)(FAR struct socket *psock);
  CODE void       (*si_addref)(FAR struct socket *psock);
  CODE int        (*si_bind)(FAR struct socket *psock,
                    FAR const struct sockaddr *addr, socklen_t addrlen);
  CODE int        (*si_getsockname)(FAR struct socket *psock,
                    FAR struct sockaddr *addr, FAR socklen_t *addrlen);
  CODE int        (*si_listen)(FAR struct socket *psock, int backlog);
  CODE int        (*si_connect)(FAR struct socket *psock,
                    FAR const struct sockaddr *addr, socklen_t addrlen);
  CODE int        (*si_accept)(FAR struct socket *psock, FAR struct sockaddr *addr,
                    FAR socklen_t *addrlen, FAR struct socket *newsock);
#ifndef CONFIG_DISABLE_POLL
  CODE int        (*si_poll)(FAR struct socket *psock,
                    FAR struct pollfd *fds, bool setup);
#endif
  CODE ssize_t    (*si_send)(FAR struct socket *psock, FAR const void *buf,
                    size_t len, int flags);
  CODE ssize_t    (*si_sendto)(FAR struct socket *psock, FAR const void *buf,
                    size_t len, int flags, FAR const struct sockaddr *to,
                    socklen_t tolen);
#ifdef CONFIG_NET_SENDFILE
  CODE ssize_t    (*si_sendfile)(FAR struct socket *psock,
                    FAR struct file *infile, FAR off_t *offset,
                    size_t count);
#endif
  CODE ssize_t    (*si_recvfrom)(FAR struct socket *psock, FAR void *buf,
                    size_t len, int flags, FAR struct sockaddr *from,
                    FAR socklen_t *fromlen);
  CODE int        (*si_close)(FAR struct socket *psock);
};

/* This is the internal representation of a socket reference by a file
 * descriptor.
 */

struct devif_callback_s;  /* Forward reference */

struct socket
{
  int16_t       s_crefs;     /* Reference count on the socket */
  uint8_t       s_domain;    /* IP domain: PF_INET, PF_INET6, or PF_PACKET */
  uint8_t       s_type;      /* Protocol type: Only SOCK_STREAM or SOCK_DGRAM */
  uint8_t       s_flags;     /* See _SF_* definitions */

  /* Socket options */

#ifdef CONFIG_NET_SOCKOPTS
  sockopt_t     s_options;   /* Selected socket options */
  socktimeo_t   s_rcvtimeo;  /* Receive timeout value (in deciseconds) */
  socktimeo_t   s_sndtimeo;  /* Send timeout value (in deciseconds) */
#ifdef CONFIG_NET_SOLINGER
  socktimeo_t   s_linger;    /* Linger timeout value (in deciseconds) */
#endif
#endif

  FAR void     *s_conn;      /* Connection: struct tcp_conn_s or udp_conn_s */

  /* Socket interface */

  FAR const struct sock_intf_s *s_sockif;

#if defined(CONFIG_NET_TCP_WRITE_BUFFERS) || defined(CONFIG_NET_UDP_WRITE_BUFFERS)
  /* Callback instance for TCP send() or UDP sendto() */

  FAR struct devif_callback_s *s_sndcb;
#endif
};

/* This defines a list of sockets indexed by the socket descriptor */

#if CONFIG_NSOCKET_DESCRIPTORS > 0
struct socketlist
{
  sem_t         sl_sem;      /* Manage access to the socket list */
  struct socket sl_sockets[CONFIG_NSOCKET_DESCRIPTORS];
};
#endif

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

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

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

/****************************************************************************
 * Name: net_setup
 *
 * Description:
 *   This is called from the OS initialization logic at power-up reset in
 *   order to configure networking data structures.  This is called prior
 *   to platform-specific driver initialization so that the networking
 *   subsystem is prepared to deal with network driver initialization
 *   actions.
 *
 *   Actions performed in this initialization phase assume that base OS
 *   facilities such as semaphores are available but this logic cannot
 *   depend upon OS resources such as interrupts or timers which are not
 *   yet available.
 *
 * Input Parameters:
 *   None
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_setup(void);

/****************************************************************************
 * Name: net_initialize
 *
 * Description:
 *   This function is called from the OS initialization logic at power-up
 *   reset AFTER initialization of hardware facilities such as timers and
 *   interrupts.   This logic completes the initialization started by
 *   net_setup().
 *
 * Input Parameters:
 *   None
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_initialize(void);

/****************************************************************************
 * Critical section management.
 *
 * Semaphore based locking is used:
 *
 *   net_lock()          - Takes the semaphore().  Implements a re-entrant mutex.
 *   net_unlock()        - Gives the semaphore().
 *   net_lockedwait()    - Like pthread_cond_wait(); releases the semaphore
 *                         momentarily to wait on another semaphore()
 *
 ****************************************************************************/

/****************************************************************************
 * Name: net_lock
 *
 * Description:
 *   Take the network lock
 *
 * Input Parameters:
 *   None
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_lock(void);

/****************************************************************************
 * Name: net_unlock
 *
 * Description:
 *   Release the network lock.
 *
 * Input Parameters:
 *   None
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_unlock(void);

/****************************************************************************
 * Name: net_timedwait
 *
 * Description:
 *   Atomically wait for sem (or a timeout( while temporarily releasing
 *   the lock on the network.
 *
 * Input Parameters:
 *   sem     - A reference to the semaphore to be taken.
 *   abstime - The absolute time to wait until a timeout is declared.
 *
 * Returned Value:
 *   Zero (OK) is returned on success; a negated errno value is returned on
 *   any failure.
 *
 ****************************************************************************/

struct timespec;
int net_timedwait(sem_t *sem, FAR const struct timespec *abstime);

/****************************************************************************
 * Name: net_lockedwait
 *
 * Description:
 *   Atomically wait for sem while temporarily releasing the network lock.
 *
 * Input Parameters:
 *   sem - A reference to the semaphore to be taken.
 *
 * Returned Value:
 *   Zero (OK) is returned on success; a negated errno value is returned on
 *   any failure.
 *
 ****************************************************************************/

int net_lockedwait(sem_t *sem);

/****************************************************************************
 * Name: net_setipid
 *
 * Description:
 *   This function may be used at boot time to set the initial ip_id.
 *
 * Assumptions:
 *
 ****************************************************************************/

void net_setipid(uint16_t id);

/****************************************************************************
 * Name: net_checksd
 *
 * Description:
 *   Check if the socket descriptor is valid for the provided TCB and if it
 *   supports the requested access.  This trivial operation is part of the
 *   fdopen() operation when the fdopen() is performed on a socket descriptor.
 *   It simply performs some sanity checking before permitting the socket
 *   descriptor to be wrapped as a C FILE stream.
 *
 ****************************************************************************/

int net_checksd(int fd, int oflags);

/****************************************************************************
 * Name: net_initlist
 *
 * Description:
 *   Initialize a list of sockets for a new task
 *
 * Input Parameters:
 *   list -- A reference to the pre-alloated socket list to be initialized.
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_initlist(FAR struct socketlist *list);

/****************************************************************************
 * Name: net_releaselist
 *
 * Description:
 *   Release resources held by the socket list
 *
 * Input Parameters:
 *   list -- A reference to the pre-allocated socket list to be un-initialized.
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void net_releaselist(FAR struct socketlist *list);

/****************************************************************************
 * Name: sockfd_socket
 *
 * Description:
 *   Given a socket descriptor, return the underlying socket structure.
 *
 * Input Parameters:
 *   sockfd - The socket descriptor index o use.
 *
 * Returned Value:
 *   On success, a reference to the socket structure associated with the
 *   the socket descriptor is returned.  NULL is returned on any failure.
 *
 ****************************************************************************/

FAR struct socket *sockfd_socket(int sockfd);

/****************************************************************************
 * Name: psock_socket
 *
 * Description:
 *   socket() creates an endpoint for communication and returns a socket
 *   structure.
 *
 * Input Parameters:
 *   domain   (see sys/socket.h)
 *   type     (see sys/socket.h)
 *   protocol (see sys/socket.h)
 *   psock    A pointer to a user allocated socket structure to be initialized.
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error:
 *
 *   EACCES
 *     Permission to create a socket of the specified type and/or protocol
 *     is denied.
 *   EAFNOSUPPORT
 *     The implementation does not support the specified address family.
 *   EINVAL
 *     Unknown protocol, or protocol family not available.
 *   EMFILE
 *     Process file table overflow.
 *   ENFILE
 *     The system limit on the total number of open files has been reached.
 *   ENOBUFS or ENOMEM
 *     Insufficient memory is available. The socket cannot be created until
 *     sufficient resources are freed.
 *   EPROTONOSUPPORT
 *     The protocol type or the specified protocol is not supported within
 *     this domain.
 *
 * Assumptions:
 *
 ****************************************************************************/

int psock_socket(int domain, int type, int protocol, FAR struct socket *psock);

/****************************************************************************
 * Name: net_close
 *
 * Description:
 *   Performs the close operation on socket descriptors
 *
 * Input Parameters:
 *   sockfd   Socket descriptor of socket
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 * Assumptions:
 *
 ****************************************************************************/

int net_close(int sockfd);

/****************************************************************************
 * Name: psock_close
 *
 * Description:
 *   Performs the close operation on a socket instance
 *
 * Input Parameters:
 *   psock   Socket instance
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 ****************************************************************************/

int psock_close(FAR struct socket *psock);

/****************************************************************************
 * Name: psock_bind
 *
 * Description:
 *   bind() gives the socket 'psock' the local address 'addr'. 'addr' is
 *   'addrlen' bytes long. Traditionally, this is called "assigning a name to
 *   a socket." When a socket is created with socket, it exists in a name
 *   space (address family) but has no name assigned.
 *
 * Input Parameters:
 *   psock    Socket structure of the socket to bind
 *   addr     Socket local address
 *   addrlen  Length of 'addr'
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 *   EACCES
 *     The address is protected, and the user is not the superuser.
 *   EADDRINUSE
 *     The given address is already in use.
 *   EINVAL
 *     The socket is already bound to an address.
 *   ENOTSOCK
 *     psock is a descriptor for a file, not a socket.
 *
 * Assumptions:
 *
 ****************************************************************************/

struct sockaddr; /* Forward reference. Defined in nuttx/include/sys/socket.h */
int psock_bind(FAR struct socket *psock, FAR const struct sockaddr *addr,
               socklen_t addrlen);

/****************************************************************************
 * Name: psock_listen
 *
 * Description:
 *   To accept connections, a socket is first created with psock_socket(), a
 *   willingness to accept incoming connections and a queue limit for
 *   incoming connections are specified with psock_listen(), and then the
 *   connections are accepted with psock_accept(). The psock_listen() call
 *   applies only to sockets of type SOCK_STREAM or SOCK_SEQPACKET.
 *
 * Input Parameters:
 *   psock    Reference to an internal, boound socket structure.
 *   backlog  The maximum length the queue of pending connections may grow.
 *            If a connection request arrives with the queue full, the client
 *            may receive an error with an indication of ECONNREFUSED or,
 *            if the underlying protocol supports retransmission, the request
 *            may be ignored so that retries succeed.
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 *   EADDRINUSE
 *     Another socket is already listening on the same port.
 *   EOPNOTSUPP
 *     The socket is not of a type that supports the listen operation.
 *
 ****************************************************************************/

int psock_listen(FAR struct socket *psock, int backlog);

/****************************************************************************
 * Name: psock_accept
 *
 * Description:
 *   The psock_accept function is used with connection-based socket types
 *   (SOCK_STREAM, SOCK_SEQPACKET and SOCK_RDM). It extracts the first
 *   connection request on the queue of pending connections, creates a new
 *   connected socket with mostly the same properties as 'sockfd', and
 *   allocates a new socket descriptor for the socket, which is returned. The
 *   newly created socket is no longer in the listening state. The original
 *   socket 'sockfd' is unaffected by this call.  Per file descriptor flags
 *   are not inherited across an psock_accept.
 *
 *   The 'sockfd' argument is a socket descriptor that has been created with
 *   socket(), bound to a local address with bind(), and is listening for
 *   connections after a call to listen().
 *
 *   On return, the 'addr' structure is filled in with the address of the
 *   connecting entity. The 'addrlen' argument initially contains the size
 *   of the structure pointed to by 'addr'; on return it will contain the
 *   actual length of the address returned.
 *
 *   If no pending connections are present on the queue, and the socket is
 *   not marked as non-blocking, psock_accept blocks the caller until a
 *   connection is present. If the socket is marked non-blocking and no
 *   pending connections are present on the queue, psock_accept returns
 *   EAGAIN.
 *
 * Input Parameters:
 *   psock    Reference to the listening socket structure
 *   addr     Receives the address of the connecting client
 *   addrlen  Input: allocated size of 'addr', Return: returned size of 'addr'
 *   newsock  Location to return the accepted socket information.
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 * EAGAIN or EWOULDBLOCK
 *   The socket is marked non-blocking and no connections are present to
 *   be accepted.
 * EOPNOTSUPP
 *   The referenced socket is not of type SOCK_STREAM.
 * EINTR
 *   The system call was interrupted by a signal that was caught before
 *   a valid connection arrived.
 * ECONNABORTED
 *   A connection has been aborted.
 * EINVAL
 *   Socket is not listening for connections.
 * EMFILE
 *   The per-process limit of open file descriptors has been reached.
 * ENFILE
 *   The system maximum for file descriptors has been reached.
 * EFAULT
 *   The addr parameter is not in a writable part of the user address
 *   space.
 * ENOBUFS or ENOMEM
 *   Not enough free memory.
 * EPROTO
 *   Protocol error.
 * EPERM
 *   Firewall rules forbid connection.
 *
 ****************************************************************************/

int psock_accept(FAR struct socket *psock, FAR struct sockaddr *addr,
                 FAR socklen_t *addrlen, FAR struct socket *newsock);

/****************************************************************************
 * Name: psock_connect
 *
 * Description:
 *   connect() connects the socket referred to by the structure 'psock'
 *   to the address specified by 'addr'. The addrlen argument specifies
 *   the size of 'addr'.  The format of the address in 'addr' is
 *   determined by the address space of the socket 'psock'.
 *
 *   If the socket 'psock' is of type SOCK_DGRAM then 'addr' is the address
 *   to which datagrams are sent by default, and the only address from which
 *   datagrams are received. If the socket is of type SOCK_STREAM or
 *   SOCK_SEQPACKET, this call attempts to make a connection to the socket
 *   that is bound to the address specified by 'addr'.
 *
 *   Generally, connection-based protocol sockets may successfully connect()
 *   only once; connectionless protocol sockets may use connect() multiple
 *   times to change their association.  Connectionless sockets may dissolve
 *   the association by connecting to an address with the sa_family member of
 *   sockaddr set to AF_UNSPEC.
 *
 * Input Parameters:
 *   psock     Pointer to a socket structure initialized by psock_socket()
 *   addr      Server address (form depends on type of socket)
 *   addrlen   Length of actual 'addr'
 *
 * Returned Value:
 *  Returns zero (OK) on success.  On failure, it returns a negated errno
 *  value to indicate the nature of the error.
 *
 *     EACCES, EPERM
 *       The user tried to connect to a broadcast address without having the
 *       socket broadcast flag enabled or the connection request failed
 *       because of a local firewall rule.
 *     EADDRINUSE
 *       Local address is already in use.
 *     EAFNOSUPPORT
 *       The passed address didn't have the correct address family in its
 *       sa_family field.
 *     EAGAIN
 *       No more free local ports or insufficient entries in the routing
 *       cache.
 *     EALREADY
 *       The socket is non-blocking and a previous connection attempt has
 *       not yet been completed.
 *     EBADF
 *       The file descriptor is not a valid index in the descriptor table.
 *     ECONNREFUSED
 *       No one listening on the remote address.
 *     EFAULT
 *       The socket structure address is outside the user's address space.
 *     EINPROGRESS
 *       The socket is non-blocking and the connection cannot be completed
 *       immediately.
 *     EINTR
 *       The system call was interrupted by a signal that was caught.
 *     EISCONN
 *       The socket is already connected.
 *     ENETUNREACH
 *       Network is unreachable.
 *     ENOTSOCK
 *       The file descriptor is not associated with a socket.
 *     ETIMEDOUT
 *       Timeout while attempting connection. The server may be too busy
 *       to accept new connections.
 *
 * Assumptions:
 *
 ****************************************************************************/

int psock_connect(FAR struct socket *psock, FAR const struct sockaddr *addr,
                  socklen_t addrlen);

/****************************************************************************
 * Name: psock_send
 *
 * Description:
 *   The psock_send() call may be used only when the socket is in a
 *   connected state (so that the intended recipient is known).  This is an
 *   internal OS interface.  It is functionally equivalent to send() except
 *   that:
 *
 *   - It is not a cancellation point,
 *   - It does not modify the errno variable, and
 *   - I accepts the internal socket structure as an input rather than an
 *     task-specific socket descriptor.
 *
 *   See comments with send() for more a more complete description of the
 *   functionality.
 *
 * Input Parameters:
 *   psock - An instance of the internal socket structure.
 *   buf   - Data to send
 *   len   - Length of data to send
 *   flags - Send flags
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  On any failure, a
 *   negated errno value is returned (See comments with send() for a list
 *   of the appropriate errno value).
 *
 ****************************************************************************/

ssize_t psock_send(FAR struct socket *psock, const void *buf, size_t len,
                   int flags);

/****************************************************************************
 * Name: nx_send
 *
 * Description:
 *   The nx_send() call may be used only when the socket is in a
 *   connected state (so that the intended recipient is known).  This is an
 *   internal OS interface.  It is functionally equivalent to send() except
 *   that:
 *
 *   - It is not a cancellation point, and
 *   - It does not modify the errno variable.
 *
 *   See comments with send() for more a more complete description of the
 *   functionality.
 *
 * Input Parameters:
 *   sockfd - Socket descriptor of the socket
 *   buf    - Data to send
 *   len    - Length of data to send
 *   flags  - Send flags
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  On any failure, a
 *   negated errno value is returned (See comments with send() for a list
 *   of the appropriate errno value).
 *
 ****************************************************************************/

ssize_t nx_send(int sockfd, FAR const void *buf, size_t len, int flags);

/****************************************************************************
 * Name: psock_sendto
 *
 * Description:
 *   If sendto() is used on a connection-mode (SOCK_STREAM, SOCK_SEQPACKET)
 *   socket, the parameters to and 'tolen' are ignored (and the error EISCONN
 *   may be returned when they are not NULL and 0), and the error ENOTCONN is
 *   returned when the socket was not actually connected.
 *
 * 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
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  On any failure, a
 *   negated errno value is returned.  One of:
 *
 *   EAGAIN or EWOULDBLOCK
 *     The socket is marked non-blocking and the requested operation
 *     would block.
 *   EBADF
 *     An invalid descriptor was specified.
 *   ECONNRESET
 *     Connection reset by peer.
 *   EDESTADDRREQ
 *     The socket is not connection-mode, and no peer address is set.
 *   EFAULT
 *      An invalid user space address was specified for a parameter.
 *   EINTR
 *      A signal occurred before any data was transmitted.
 *   EINVAL
 *      Invalid argument passed.
 *   EISCONN
 *     The connection-mode socket was connected already but a recipient
 *     was specified. (Now either this error is returned, or the recipient
 *     specification is ignored.)
 *   EMSGSIZE
 *     The socket type requires that message be sent atomically, and the
 *     size of the message to be sent made this impossible.
 *   ENOBUFS
 *     The output queue for a network interface was full. This generally
 *     indicates that the interface has stopped sending, but may be
 *     caused by transient congestion.
 *   ENOMEM
 *     No memory available.
 *   ENOTCONN
 *     The socket is not connected, and no target has been given.
 *   ENOTSOCK
 *     The argument s is not a socket.
 *   EOPNOTSUPP
 *     Some bit in the flags argument is inappropriate for the socket
 *     type.
 *   EPIPE
 *     The local end has been shut down on a connection oriented socket.
 *     In this case the process will also receive a SIGPIPE unless
 *     MSG_NOSIGNAL is set.
 *
 ****************************************************************************/

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

/****************************************************************************
 * Name: psock_recvfrom
 *
 * Description:
 *   psock_recvfrom() receives messages from a socket, and may be used to
 *   receive data on a socket whether or not it is connection-oriented.
 *   This is an internal OS interface.  It is functionally equivalent to
 *   recvfrom() except that:
 *
 *   - It is not a cancellation point,
 *   - It does not modify the errno variable, and
 *   - I accepts the internal socket structure as an input rather than an
 *     task-specific socket descriptor.
 *
 * Input Parameters:
 *   psock   - A pointer to a NuttX-specific, internal socket structure
 *   buf     - Buffer to receive data
 *   len     - Length of buffer
 *   flags   - Receive flags
 *   from    - Address of source (may be NULL)
 *   fromlen - The length of the address structure
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  If no data is
 *   available to be received and the peer has performed an orderly shutdown,
 *   recv() will return 0.  Otherwise, on any failure, a negated errno value
 *   is returned (see comments with send() for a list of appropriate errno
 *   values).
 *
 ****************************************************************************/

ssize_t psock_recvfrom(FAR struct socket *psock, FAR void *buf, size_t len,
                       int flags, FAR struct sockaddr *from,
                       FAR socklen_t *fromlen);

/* recv using the underlying socket structure */

#define psock_recv(psock,buf,len,flags) \
  psock_recvfrom(psock,buf,len,flags,NULL,0)

/****************************************************************************
 * Name: nx_recvfrom
 *
 * Description:
 *   nx_recvfrom() receives messages from a socket, and may be used to
 *   receive data on a socket whether or not it is connection-oriented.
 *   This is an internal OS interface.  It is functionally equivalent to
 *   recvfrom() except that:
 *
 *   - It is not a cancellation point, and
 *   - It does not modify the errno variable.
 *
 * Input Parameters:
 *   sockfd  - Socket descriptor of socket
 *   buf     - Buffer to receive data
 *   len     - Length of buffer
 *   flags   - Receive flags
 *   from    - Address of source (may be NULL)
 *   fromlen - The length of the address structure
 *
 * Returned Value:
 *   On success, returns the number of characters sent.  If no data is
 *   available to be received and the peer has performed an orderly shutdown,
 *   recv() will return 0.  Otherwise, on any failure, a negated errno value
 *   is returned (see comments with send() for a list of appropriate errno
 *   values).
 *
 ****************************************************************************/

ssize_t nx_recvfrom(int sockfd, FAR void *buf, size_t len, int flags,
                    FAR struct sockaddr *from, FAR socklen_t *fromlen);

/* Internal version os recv */

#define nx_recv(psock,buf,len,flags) nx_recvfrom(psock,buf,len,flags,NULL,0)

/****************************************************************************
 * Name: psock_getsockopt
 *
 * Description:
 *   getsockopt() retrieve thse value for the option specified by the
 *   'option' argument for the socket specified by the 'psock' argument. If
 *   the size of the option value is greater than 'value_len', the value
 *   stored in the object pointed to by the 'value' argument will be silently
 *   truncated. Otherwise, the length pointed to by the 'value_len' argument
 *   will be modified to indicate the actual length of the'value'.
 *
 *   The 'level' argument specifies the protocol level of the option. To
 *   retrieve options at the socket level, specify the level argument as
 *   SOL_SOCKET.
 *
 *   See <sys/socket.h> a complete list of values for the 'option' argument.
 *
 * Input Parameters:
 *   psock     Socket structure of the socket to query
 *   level     Protocol level to set the option
 *   option    identifies the option to get
 *   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:
 *
 *  EINVAL
 *    The specified option is invalid at the specified socket 'level' or the
 *    socket has been shutdown.
 *  ENOPROTOOPT
 *    The 'option' is not supported by the protocol.
 *  ENOTSOCK
 *    The 'psock' argument does not refer to a socket.
 *  ENOBUFS
 *    Insufficient resources are available in the system to complete the
 *    call.
 *
 ****************************************************************************/

int psock_getsockopt(FAR struct socket *psock, int level, int option,
                     FAR void *value, FAR socklen_t *value_len);

/****************************************************************************
 * Name: psock_setsockopt
 *
 * Description:
 *   psock_setsockopt() sets the option specified by the 'option' argument,
 *   at the protocol level specified by the 'level' argument, to the value
 *   pointed to by the 'value' argument for the socket on the 'psock' argument.
 *
 *   The 'level' argument specifies the protocol level of the option. To set
 *   options at the socket level, specify the level argument as SOL_SOCKET.
 *
 *   See <sys/socket.h> a complete list of values for the 'option' argument.
 *
 * Input Parameters:
 *   psock     Socket structure of socket to operate on
 *   level     Protocol level to set the option
 *   option    identifies the option to set
 *   value     Points to the argument value
 *   value_len The length of the argument value
 *
 * Returned Value: