text: /**
   * @file
   * netconn API (to be used from non-TCPIP threads)
   */
  
  /*
   * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
   * All rights reserved.
   *
   * 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. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
   *
   * This file is part of the lwIP TCP/IP stack.
   *
   * Author: Adam Dunkels <adam@sics.se>
   *
   */
  #ifndef LWIP_HDR_API_H
  #define LWIP_HDR_API_H
  
  #include <net/lwip/lwip/opt.h>
  
  #if LWIP_NETCONN || LWIP_SOCKET /* don't build if not configured for use in lwipopts.h */
  /* Note: Netconn API is always available when sockets are enabled -
   * sockets are implemented on top of them */
  
  #include <net/lwip/lwip/arch.h>
  #include <net/lwip/lwip/netbuf.h>
  #include <net/lwip/lwip/sys.h>
  #include <net/lwip/lwip/ip_addr.h>
  #include <net/lwip/lwip/err.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /* Throughout this file, IP addresses and port numbers are expected to be in
   * the same byte order as in the corresponding pcb.
   */
  
  /* Flags for netconn_write (u8_t) */
  #define NETCONN_NOFLAG      0x00
  #define NETCONN_NOCOPY      0x00 /* Only for source code compatibility */
  #define NETCONN_COPY        0x01
  #define NETCONN_MORE        0x02
  #define NETCONN_DONTBLOCK   0x04
  #define NETCONN_NOAUTORCVD  0x08 /* prevent netconn_recv_data_tcp() from updating the tcp window - must be done manually via netconn_tcp_recvd() */
  #define NETCONN_NOFIN       0x10 /* upper layer already received data, leave FIN in queue until called again */
  
  /* Flags for struct netconn.flags (u8_t) */
  /** This netconn had an error, don't block on recvmbox/acceptmbox any more */
  #define NETCONN_FLAG_MBOXCLOSED               0x01
  /** Should this netconn avoid blocking? */
  #define NETCONN_FLAG_NON_BLOCKING             0x02
  /** Was the last connect action a non-blocking one? */
  #define NETCONN_FLAG_IN_NONBLOCKING_CONNECT   0x04
  #if LWIP_NETCONN_FULLDUPLEX
    /** The mbox of this netconn is being deallocated, don't use it anymore */
  #define NETCONN_FLAG_MBOXINVALID              0x08
  #endif /* LWIP_NETCONN_FULLDUPLEX */
  /** If a nonblocking write has been rejected before, poll_tcp needs to
      check if the netconn is writable again */
  #define NETCONN_FLAG_CHECK_WRITESPACE         0x10
  #if LWIP_IPV6
  /** If this flag is set then only IPv6 communication is allowed on the
      netconn. As per RFC#3493 this features defaults to OFF allowing
      dual-stack usage by default. */
  #define NETCONN_FLAG_IPV6_V6ONLY              0x20
  #endif /* LWIP_IPV6 */
  #if LWIP_NETBUF_RECVINFO
  /** Received packet info will be recorded for this netconn */
  #define NETCONN_FLAG_PKTINFO                  0x40
  #endif /* LWIP_NETBUF_RECVINFO */
  /** A FIN has been received but not passed to the application yet */
  #define NETCONN_FIN_RX_PENDING                0x80
  
  /* Helpers to process several netconn_types by the same code */
  #define NETCONNTYPE_GROUP(t)         ((t)&0xF0)
  #define NETCONNTYPE_DATAGRAM(t)      ((t)&0xE0)
  #if LWIP_IPV6
  #define NETCONN_TYPE_IPV6            0x08
  #define NETCONNTYPE_ISIPV6(t)        (((t)&NETCONN_TYPE_IPV6) != 0)
  #define NETCONNTYPE_ISUDPLITE(t)     (((t)&0xF3) == NETCONN_UDPLITE)
  #define NETCONNTYPE_ISUDPNOCHKSUM(t) (((t)&0xF3) == NETCONN_UDPNOCHKSUM)
  #else /* LWIP_IPV6 */
  #define NETCONNTYPE_ISIPV6(t)        (0)
  #define NETCONNTYPE_ISUDPLITE(t)     ((t) == NETCONN_UDPLITE)
  #define NETCONNTYPE_ISUDPNOCHKSUM(t) ((t) == NETCONN_UDPNOCHKSUM)
  #endif /* LWIP_IPV6 */
  
  /** @ingroup netconn_common
   * Protocol family and type of the netconn
   */
  enum netconn_type {
    NETCONN_INVALID     = 0,
    /** TCP IPv4 */
    NETCONN_TCP         = 0x10,
  #if LWIP_IPV6
    /** TCP IPv6 */
    NETCONN_TCP_IPV6    = NETCONN_TCP | NETCONN_TYPE_IPV6 /* 0x18 */,
  #endif /* LWIP_IPV6 */
    /** UDP IPv4 */
    NETCONN_UDP         = 0x20,
    /** UDP IPv4 lite */
    NETCONN_UDPLITE     = 0x21,
    /** UDP IPv4 no checksum */
    NETCONN_UDPNOCHKSUM = 0x22,
  
  #if LWIP_IPV6
    /** UDP IPv6 (dual-stack by default, unless you call @ref netconn_set_ipv6only) */
    NETCONN_UDP_IPV6         = NETCONN_UDP | NETCONN_TYPE_IPV6 /* 0x28 */,
    /** UDP IPv6 lite (dual-stack by default, unless you call @ref netconn_set_ipv6only) */
    NETCONN_UDPLITE_IPV6     = NETCONN_UDPLITE | NETCONN_TYPE_IPV6 /* 0x29 */,
    /** UDP IPv6 no checksum (dual-stack by default, unless you call @ref netconn_set_ipv6only) */
    NETCONN_UDPNOCHKSUM_IPV6 = NETCONN_UDPNOCHKSUM | NETCONN_TYPE_IPV6 /* 0x2a */,
  #endif /* LWIP_IPV6 */
  
    /** Raw connection IPv4 */
    NETCONN_RAW         = 0x40
  #if LWIP_IPV6
    /** Raw connection IPv6 (dual-stack by default, unless you call @ref netconn_set_ipv6only) */
    , NETCONN_RAW_IPV6    = NETCONN_RAW | NETCONN_TYPE_IPV6 /* 0x48 */
  #endif /* LWIP_IPV6 */
  };
  
  /** Current state of the netconn. Non-TCP netconns are always
   * in state NETCONN_NONE! */
  enum netconn_state {
    NETCONN_NONE,
    NETCONN_WRITE,
    NETCONN_LISTEN,
    NETCONN_CONNECT,
    NETCONN_CLOSE
  };
  
  /** Used to inform the callback function about changes
   *
   * Event explanation:
   *
   * In the netconn implementation, there are three ways to block a client:
   *
   * - accept mbox (sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, 0); in netconn_accept())
   * - receive mbox (sys_arch_mbox_fetch(&conn->recvmbox, &buf, 0); in netconn_recv_data())
   * - send queue is full (sys_arch_sem_wait(LWIP_API_MSG_SEM(msg), 0); in lwip_netconn_do_write())
   *
   * The events have to be seen as events signaling the state of these mboxes/semaphores. For non-blocking
   * connections, you need to know in advance whether a call to a netconn function call would block or not,
   * and these events tell you about that.
   *
   * RCVPLUS events say: Safe to perform a potentially blocking call call once more.
   * They are counted in sockets - three RCVPLUS events for accept mbox means you are safe
   * to call netconn_accept 3 times without being blocked.
   * Same thing for receive mbox.
   *
   * RCVMINUS events say: Your call to to a possibly blocking function is "acknowledged".
   * Socket implementation decrements the counter.
   *
   * For TX, there is no need to count, its merely a flag. SENDPLUS means you may send something.
   * SENDPLUS occurs when enough data was delivered to peer so netconn_send() can be called again.
   * A SENDMINUS event occurs when the next call to a netconn_send() would be blocking.
   */
  enum netconn_evt {
    NETCONN_EVT_RCVPLUS,
    NETCONN_EVT_RCVMINUS,
    NETCONN_EVT_SENDPLUS,
    NETCONN_EVT_SENDMINUS,
    NETCONN_EVT_ERROR
  };
  
  #if LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD)
  /** Used for netconn_join_leave_group() */
  enum netconn_igmp {
    NETCONN_JOIN,
    NETCONN_LEAVE
  };
  #endif /* LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD) */
  
  #if LWIP_DNS
  /* Used for netconn_gethostbyname_addrtype(), these should match the DNS_ADDRTYPE defines in dns.h */
  #define NETCONN_DNS_DEFAULT   NETCONN_DNS_IPV4_IPV6
  #define NETCONN_DNS_IPV4      0
  #define NETCONN_DNS_IPV6      1
  #define NETCONN_DNS_IPV4_IPV6 2 /* try to resolve IPv4 first, try IPv6 if IPv4 fails only */
  #define NETCONN_DNS_IPV6_IPV4 3 /* try to resolve IPv6 first, try IPv4 if IPv6 fails only */
  #endif /* LWIP_DNS */
  
  /* forward-declare some structs to avoid to include their headers */
  struct ip_pcb;
  struct tcp_pcb;
  struct udp_pcb;
  struct raw_pcb;
  struct netconn;
  struct api_msg;
  
  /** A callback prototype to inform about events for a netconn */
  typedef void (* netconn_callback)(struct netconn *, enum netconn_evt, u16_t len);
  
  /** A netconn descriptor */
  struct netconn {
    /** type of the netconn (TCP, UDP or RAW) */
    enum netconn_type type;
    /** current state of the netconn */
    enum netconn_state state;
    /** the lwIP internal protocol control block */
    union {
      struct ip_pcb  *ip;
      struct tcp_pcb *tcp;
      struct udp_pcb *udp;
      struct raw_pcb *raw;
    } pcb;
    /** the last asynchronous unreported error this netconn had */
    err_t pending_err;
  #if !LWIP_NETCONN_SEM_PER_THREAD
    /** sem that is used to synchronously execute functions in the core context */
    sys_sem_t op_completed;
  #endif
    /** mbox where received packets are stored until they are fetched
        by the netconn application thread (can grow quite big) */
    sys_mbox_t recvmbox;
  #if LWIP_TCP
    /** mbox where new connections are stored until processed
        by the application thread */
    sys_mbox_t acceptmbox;
  #endif /* LWIP_TCP */
  #if LWIP_NETCONN_FULLDUPLEX
    /** number of threads waiting on an mbox. This is required to unblock
        all threads when closing while threads are waiting. */
    int mbox_threads_waiting;
  #endif
    /** only used for socket layer */
  #if LWIP_SOCKET
    int socket;
  #endif /* LWIP_SOCKET */
  #if LWIP_SO_SNDTIMEO
    /** timeout to wait for sending data (which means enqueueing data for sending
        in internal buffers) in milliseconds */
    s32_t send_timeout;
  #endif /* LWIP_SO_RCVTIMEO */
  #if LWIP_SO_RCVTIMEO
    /** timeout in milliseconds to wait for new data to be received
        (or connections to arrive for listening netconns) */
    u32_t recv_timeout;
  #endif /* LWIP_SO_RCVTIMEO */
  #if LWIP_SO_RCVBUF
    /** maximum amount of bytes queued in recvmbox
        not used for TCP: adjust TCP_WND instead! */
    int recv_bufsize;
    /** number of bytes currently in recvmbox to be received,
        tested against recv_bufsize to limit bytes on recvmbox
        for UDP and RAW, used for FIONREAD */
    int recv_avail;
  #endif /* LWIP_SO_RCVBUF */
  #if LWIP_SO_LINGER
     /** values <0 mean linger is disabled, values > 0 are seconds to linger */
    s16_t linger;
  #endif /* LWIP_SO_LINGER */
    /** flags holding more netconn-internal state, see NETCONN_FLAG_* defines */
    u8_t flags;
  #if LWIP_TCP
    /** TCP: when data passed to netconn_write doesn't fit into the send buffer,
        this temporarily stores the message.
        Also used during connect and close. */
    struct api_msg *current_msg;
  #endif /* LWIP_TCP */
    /** A callback function that is informed about events for this netconn */
    netconn_callback callback;
  };
  
  /** This vector type is passed to @ref netconn_write_vectors_partly to send
   * multiple buffers at once.
   * ATTENTION: This type has to directly map struct iovec since one is casted
   *            into the other!
   */
  struct netvector {
    /** pointer to the application buffer that contains the data to send */
    const void *ptr;
    /** size of the application data to send */
    size_t len;
  };
  
  /** Register an Network connection event */
  #define API_EVENT(c,e,l) if (c->callback) {         \
                             (*c->callback)(c, e, l); \
                           }
  
  /* Network connection functions: */
  
  /** @ingroup netconn_common
   * Create new netconn connection
   * @param t @ref netconn_type */
  #define netconn_new(t)                  netconn_new_with_proto_and_callback(t, 0, NULL)
  #define netconn_new_with_callback(t, c) netconn_new_with_proto_and_callback(t, 0, c)
  struct netconn *netconn_new_with_proto_and_callback(enum netconn_type t, u8_t proto,
                                               netconn_callback callback);
  err_t   netconn_prepare_delete(struct netconn *conn);
  err_t   netconn_delete(struct netconn *conn);
  /** Get the type of a netconn (as enum netconn_type). */
  #define netconn_type(conn) (conn->type)
  
  err_t   netconn_getaddr(struct netconn *conn, ip_addr_t *addr,
                          u16_t *port, u8_t local);
  /** @ingroup netconn_common */
  #define netconn_peer(c,i,p) netconn_getaddr(c,i,p,0)
  /** @ingroup netconn_common */
  #define netconn_addr(c,i,p) netconn_getaddr(c,i,p,1)
  
  err_t   netconn_bind(struct netconn *conn, const ip_addr_t *addr, u16_t port);
  err_t   netconn_bind_if(struct netconn *conn, u8_t if_idx);
  err_t   netconn_connect(struct netconn *conn, const ip_addr_t *addr, u16_t port);
  err_t   netconn_disconnect (struct netconn *conn);
  err_t   netconn_listen_with_backlog(struct netconn *conn, u8_t backlog);
  /** @ingroup netconn_tcp */
  #define netconn_listen(conn) netconn_listen_with_backlog(conn, TCP_DEFAULT_LISTEN_BACKLOG)
  err_t   netconn_accept(struct netconn *conn, struct netconn **new_conn);
  err_t   netconn_recv(struct netconn *conn, struct netbuf **new_buf);
  err_t   netconn_recv_udp_raw_netbuf(struct netconn *conn, struct netbuf **new_buf);
  err_t   netconn_recv_udp_raw_netbuf_flags(struct netconn *conn, struct netbuf **new_buf, u8_t apiflags);
  err_t   netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf);
  err_t   netconn_recv_tcp_pbuf_flags(struct netconn *conn, struct pbuf **new_buf, u8_t apiflags);
  err_t   netconn_tcp_recvd(struct netconn *conn, size_t len);
  err_t   netconn_sendto(struct netconn *conn, struct netbuf *buf,
                               const ip_addr_t *addr, u16_t port);
  err_t   netconn_send(struct netconn *conn, struct netbuf *buf);
  err_t   netconn_write_partly(struct netconn *conn, const void *dataptr, size_t size,
                               u8_t apiflags, size_t *bytes_written);
  err_t   netconn_write_vectors_partly(struct netconn *conn, struct netvector *vectors, u16_t vectorcnt,
                                       u8_t apiflags, size_t *bytes_written);
  /** @ingroup netconn_tcp */
  #define netconn_write(conn, dataptr, size, apiflags) \
            netconn_write_partly(conn, dataptr, size, apiflags, NULL)
  err_t   netconn_close(struct netconn *conn);
  err_t   netconn_shutdown(struct netconn *conn, u8_t shut_rx, u8_t shut_tx);
  
  #if LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD)
  err_t   netconn_join_leave_group(struct netconn *conn, const ip_addr_t *multiaddr,
                               const ip_addr_t *netif_addr, enum netconn_igmp join_or_leave);
  err_t   netconn_join_leave_group_netif(struct netconn *conn, const ip_addr_t *multiaddr,
                               u8_t if_idx, enum netconn_igmp join_or_leave);
  #endif /* LWIP_IGMP || (LWIP_IPV6 && LWIP_IPV6_MLD) */
  #if LWIP_DNS
  #if LWIP_IPV4 && LWIP_IPV6
  err_t   netconn_gethostbyname_addrtype(const char *name, ip_addr_t *addr, u8_t dns_addrtype);
  #define netconn_gethostbyname(name, addr) netconn_gethostbyname_addrtype(name, addr, NETCONN_DNS_DEFAULT)
  #else /* LWIP_IPV4 && LWIP_IPV6 */
  err_t   netconn_gethostbyname(const char *name, ip_addr_t *addr);
  #define netconn_gethostbyname_addrtype(name, addr, dns_addrtype) netconn_gethostbyname(name, addr)
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  #endif /* LWIP_DNS */
  
  err_t   netconn_err(struct netconn *conn);
  #define netconn_recv_bufsize(conn)      ((conn)->recv_bufsize)
  
  #define netconn_set_flags(conn, set_flags)     do { (conn)->flags = (u8_t)((conn)->flags |  (set_flags)); } while(0)
  #define netconn_clear_flags(conn, clr_flags)   do { (conn)->flags = (u8_t)((conn)->flags & (u8_t)(~(clr_flags) & 0xff)); } while(0)
  #define netconn_is_flag_set(conn, flag)        (((conn)->flags & (flag)) != 0)
  
  /** Set the blocking status of netconn calls (@todo: write/send is missing) */
  #define netconn_set_nonblocking(conn, val)  do { if(val) { \
    netconn_set_flags(conn, NETCONN_FLAG_NON_BLOCKING); \
  } else { \
    netconn_clear_flags(conn, NETCONN_FLAG_NON_BLOCKING); }} while(0)
  /** Get the blocking status of netconn calls (@todo: write/send is missing) */
  #define netconn_is_nonblocking(conn)        (((conn)->flags & NETCONN_FLAG_NON_BLOCKING) != 0)
  
  #if LWIP_IPV6
  /** @ingroup netconn_common
   * TCP: Set the IPv6 ONLY status of netconn calls (see NETCONN_FLAG_IPV6_V6ONLY)
   */
  #define netconn_set_ipv6only(conn, val)  do { if(val) { \
    netconn_set_flags(conn, NETCONN_FLAG_IPV6_V6ONLY); \
  } else { \
    netconn_clear_flags(conn, NETCONN_FLAG_IPV6_V6ONLY); }} while(0)
  /** @ingroup netconn_common
   * TCP: Get the IPv6 ONLY status of netconn calls (see NETCONN_FLAG_IPV6_V6ONLY)
   */
  #define netconn_get_ipv6only(conn)        (((conn)->flags & NETCONN_FLAG_IPV6_V6ONLY) != 0)
  #endif /* LWIP_IPV6 */
  
  #if LWIP_SO_SNDTIMEO
  /** Set the send timeout in milliseconds */
  #define netconn_set_sendtimeout(conn, timeout)      ((conn)->send_timeout = (timeout))
  /** Get the send timeout in milliseconds */
  #define netconn_get_sendtimeout(conn)               ((conn)->send_timeout)
  #endif /* LWIP_SO_SNDTIMEO */
  #if LWIP_SO_RCVTIMEO
  /** Set the receive timeout in milliseconds */
  #define netconn_set_recvtimeout(conn, timeout)      ((conn)->recv_timeout = (timeout))
  /** Get the receive timeout in milliseconds */
  #define netconn_get_recvtimeout(conn)               ((conn)->recv_timeout)
  #endif /* LWIP_SO_RCVTIMEO */
  #if LWIP_SO_RCVBUF
  /** Set the receive buffer in bytes */
  #define netconn_set_recvbufsize(conn, recvbufsize)  ((conn)->recv_bufsize = (recvbufsize))
  /** Get the receive buffer in bytes */
  #define netconn_get_recvbufsize(conn)               ((conn)->recv_bufsize)
  #endif /* LWIP_SO_RCVBUF*/
  
  #if LWIP_NETCONN_SEM_PER_THREAD
  void netconn_thread_init(void);
  void netconn_thread_cleanup(void);
  #else /* LWIP_NETCONN_SEM_PER_THREAD */
  #define netconn_thread_init()
  #define netconn_thread_cleanup()
  #endif /* LWIP_NETCONN_SEM_PER_THREAD */
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* LWIP_NETCONN || LWIP_SOCKET */
  
  #endif /* LWIP_HDR_API_H */
  