api_lib.c

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/*
 * 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>
 */
 
/* This is the part of the API that is linked with
   the application */
 
#include <net/opt.h>
 
#if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
 
#include <net/api.h>
#include <net/memp.h>
 
#include <net/ip.h>
#include <net/raw.h>
#include <net/udp.h>
#include <net/priv/api_msg.h>
#include <net/priv/tcp_priv.h>
#include <net/priv/tcpip_priv.h>
 
#include <string.h>
 
#define API_MSG_VAR_REF(name)               API_VAR_REF(name)
#define API_MSG_VAR_DECLARE(name)           API_VAR_DECLARE(struct api_msg, name)
#define API_MSG_VAR_ALLOC(name)             API_VAR_ALLOC(struct api_msg, MEMP_API_MSG, name, ERR_MEM)
#define API_MSG_VAR_ALLOC_RETURN_NULL(name) API_VAR_ALLOC(struct api_msg, MEMP_API_MSG, name, NULL)
#define API_MSG_VAR_FREE(name)              API_VAR_FREE(MEMP_API_MSG, name)
 
static err_t netconn_close_shutdown(struct netconn *conn, u8_t how);
 
static err_t
netconn_apimsg(tcpip_callback_fn fn, struct api_msg *apimsg)
{
  err_t err;
 
#ifdef LWIP_DEBUG
  /* catch functions that don't set err */
  apimsg->err = ERR_VAL;
#endif /* LWIP_DEBUG */
 
#if LWIP_NETCONN_SEM_PER_THREAD
  apimsg->op_completed_sem = LWIP_NETCONN_THREAD_SEM_GET();
#endif /* LWIP_NETCONN_SEM_PER_THREAD */
 
  err = tcpip_send_msg_wait_sem(fn, apimsg, LWIP_API_MSG_SEM(apimsg));
  if (err == ERR_OK) {
    return apimsg->err;
  }
  return err;
}
 
struct netconn*
netconn_new_with_proto_and_callback(enum netconn_type t, u8_t proto, netconn_callback callback)
{
  struct netconn *conn;
  API_MSG_VAR_DECLARE(msg);
  API_MSG_VAR_ALLOC_RETURN_NULL(msg);
 
  conn = netconn_alloc(t, callback);
  if (conn != NULL) {
    err_t err;
 
    API_MSG_VAR_REF(msg).msg.n.proto = proto;
    API_MSG_VAR_REF(msg).conn = conn;
    err = netconn_apimsg(lwip_netconn_do_newconn, &API_MSG_VAR_REF(msg));
    if (err != ERR_OK) {
      LWIP_ASSERT("freeing conn without freeing pcb", conn->pcb.tcp == NULL);
      LWIP_ASSERT("conn has no recvmbox", sys_mbox_valid(&conn->recvmbox));
#if LWIP_TCP
      LWIP_ASSERT("conn->acceptmbox shouldn't exist", !sys_mbox_valid(&conn->acceptmbox));
#endif /* LWIP_TCP */
#if !LWIP_NETCONN_SEM_PER_THREAD
      LWIP_ASSERT("conn has no op_completed", sys_sem_valid(&conn->op_completed));
      sys_sem_free(&conn->op_completed);
#endif /* !LWIP_NETCONN_SEM_PER_THREAD */
      sys_mbox_free(&conn->recvmbox);
      memp_free(MEMP_NETCONN, conn);
      API_MSG_VAR_FREE(msg);
      return NULL;
    }
  }
  API_MSG_VAR_FREE(msg);
  return conn;
}
 
err_t
netconn_delete(struct netconn *conn)
{
  err_t err;
  API_MSG_VAR_DECLARE(msg);
 
  /* No ASSERT here because possible to get a (conn == NULL) if we got an accept error */
  if (conn == NULL) {
    return ERR_OK;
  }
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
#if LWIP_SO_SNDTIMEO || LWIP_SO_LINGER
  /* get the time we started, which is later compared to
     sys_now() + conn->send_timeout */
  API_MSG_VAR_REF(msg).msg.sd.time_started = sys_now();
#else /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
#if LWIP_TCP
  API_MSG_VAR_REF(msg).msg.sd.polls_left =
    ((LWIP_TCP_CLOSE_TIMEOUT_MS_DEFAULT + TCP_SLOW_INTERVAL - 1) / TCP_SLOW_INTERVAL) + 1;
#endif /* LWIP_TCP */
#endif /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
  err = netconn_apimsg(lwip_netconn_do_delconn, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  if (err != ERR_OK) {
    return err;
  }
 
  netconn_free(conn);
 
  return ERR_OK;
}
 
err_t
netconn_getaddr(struct netconn *conn, ip_addr_t *addr, u16_t *port, u8_t local)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  LWIP_ERROR("netconn_getaddr: invalid conn", (conn != NULL), return ERR_ARG;);
  LWIP_ERROR("netconn_getaddr: invalid addr", (addr != NULL), return ERR_ARG;);
  LWIP_ERROR("netconn_getaddr: invalid port", (port != NULL), return ERR_ARG;);
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.ad.local = local;
#if LWIP_MPU_COMPATIBLE
  err = netconn_apimsg(lwip_netconn_do_getaddr, &API_MSG_VAR_REF(msg));
  *addr = msg->msg.ad.ipaddr;
  *port = msg->msg.ad.port;
#else /* LWIP_MPU_COMPATIBLE */
  msg.msg.ad.ipaddr = addr;
  msg.msg.ad.port = port;
  err = netconn_apimsg(lwip_netconn_do_getaddr, &msg);
#endif /* LWIP_MPU_COMPATIBLE */
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_bind(struct netconn *conn, const ip_addr_t *addr, u16_t port)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
  
  LWIP_ERROR("netconn_bind: invalid conn", (conn != NULL), return ERR_ARG;);
 
#if LWIP_IPV4
  /* Don't propagate NULL pointer (IP_ADDR_ANY alias) to subsequent functions */
  if (addr == NULL) {
    addr = IP4_ADDR_ANY;
  }
#endif /* LWIP_IPV4 */
  
#if LWIP_IPV4 && LWIP_IPV6
  /* "Socket API like" dual-stack support: If IP to bind to is IP6_ADDR_ANY,
   * and NETCONN_FLAG_IPV6_V6ONLY is 0, use IP_ANY_TYPE to bind
   */
  if ((netconn_get_ipv6only(conn) == 0) &&
     ip_addr_cmp(addr, IP6_ADDR_ANY)) {
    addr = IP_ANY_TYPE;
  }
#endif /* LWIP_IPV4 && LWIP_IPV6 */
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.bc.ipaddr = API_MSG_VAR_REF(addr);
  API_MSG_VAR_REF(msg).msg.bc.port = port;
  err = netconn_apimsg(lwip_netconn_do_bind, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_connect(struct netconn *conn, const ip_addr_t *addr, u16_t port)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  LWIP_ERROR("netconn_connect: invalid conn", (conn != NULL), return ERR_ARG;);
 
#if LWIP_IPV4
  /* Don't propagate NULL pointer (IP_ADDR_ANY alias) to subsequent functions */
  if (addr == NULL) {
    addr = IP4_ADDR_ANY;
  }
#endif /* LWIP_IPV4 */
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.bc.ipaddr = API_MSG_VAR_REF(addr);
  API_MSG_VAR_REF(msg).msg.bc.port = port;
  err = netconn_apimsg(lwip_netconn_do_connect, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_disconnect(struct netconn *conn)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  LWIP_ERROR("netconn_disconnect: invalid conn", (conn != NULL), return ERR_ARG;);
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
  err = netconn_apimsg(lwip_netconn_do_disconnect, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_listen_with_backlog(struct netconn *conn, u8_t backlog)
{
#if LWIP_TCP
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  /* This does no harm. If TCP_LISTEN_BACKLOG is off, backlog is unused. */
  LWIP_UNUSED_ARG(backlog);
 
  LWIP_ERROR("netconn_listen: invalid conn", (conn != NULL), return ERR_ARG;);
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
#if TCP_LISTEN_BACKLOG
  API_MSG_VAR_REF(msg).msg.lb.backlog = backlog;
#endif /* TCP_LISTEN_BACKLOG */
  err = netconn_apimsg(lwip_netconn_do_listen, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
#else /* LWIP_TCP */
  LWIP_UNUSED_ARG(conn);
  LWIP_UNUSED_ARG(backlog);
  return ERR_ARG;
#endif /* LWIP_TCP */
}
 
err_t
netconn_accept(struct netconn *conn, struct netconn **new_conn)
{
#if LWIP_TCP
  void *accept_ptr;
  struct netconn *newconn;
#if TCP_LISTEN_BACKLOG
  API_MSG_VAR_DECLARE(msg);
#endif /* TCP_LISTEN_BACKLOG */
 
  LWIP_ERROR("netconn_accept: invalid pointer",    (new_conn != NULL),                  return ERR_ARG;);
  *new_conn = NULL;
  LWIP_ERROR("netconn_accept: invalid conn",       (conn != NULL),                      return ERR_ARG;);
 
  if (ERR_IS_FATAL(conn->last_err)) {
    /* don't recv on fatal errors: this might block the application task
       waiting on acceptmbox forever! */
    return conn->last_err;
  }
  if (!sys_mbox_valid(&conn->acceptmbox)) {
    return ERR_CLSD;
  }
 
#if TCP_LISTEN_BACKLOG
  API_MSG_VAR_ALLOC(msg);
#endif /* TCP_LISTEN_BACKLOG */
 
#if LWIP_SO_RCVTIMEO
  if (sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
#if TCP_LISTEN_BACKLOG
    API_MSG_VAR_FREE(msg);
#endif /* TCP_LISTEN_BACKLOG */
    return ERR_TIMEOUT;
  }
#else
  sys_arch_mbox_fetch(&conn->acceptmbox, &accept_ptr, 0);
#endif /* LWIP_SO_RCVTIMEO*/
  newconn = (struct netconn *)accept_ptr;
  /* Register event with callback */
  API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
 
  if (accept_ptr == &netconn_aborted) {
    /* a connection has been aborted: out of pcbs or out of netconns during accept */
    /* @todo: set netconn error, but this would be fatal and thus block further accepts */
#if TCP_LISTEN_BACKLOG
    API_MSG_VAR_FREE(msg);
#endif /* TCP_LISTEN_BACKLOG */
    return ERR_ABRT;
  }
  if (newconn == NULL) {
    /* connection has been aborted */
    /* in this special case, we set the netconn error from application thread, as
       on a ready-to-accept listening netconn, there should not be anything running
       in tcpip_thread */
    NETCONN_SET_SAFE_ERR(conn, ERR_CLSD);
#if TCP_LISTEN_BACKLOG
    API_MSG_VAR_FREE(msg);
#endif /* TCP_LISTEN_BACKLOG */
    return ERR_CLSD;
  }
#if TCP_LISTEN_BACKLOG
  /* Let the stack know that we have accepted the connection. */
  API_MSG_VAR_REF(msg).conn = newconn;
  /* don't care for the return value of lwip_netconn_do_recv */
  netconn_apimsg(lwip_netconn_do_accepted, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
#endif /* TCP_LISTEN_BACKLOG */
 
  *new_conn = newconn;
  /* don't set conn->last_err: it's only ERR_OK, anyway */
  return ERR_OK;
#else /* LWIP_TCP */
  LWIP_UNUSED_ARG(conn);
  LWIP_UNUSED_ARG(new_conn);
  return ERR_ARG;
#endif /* LWIP_TCP */
}
 
static err_t
netconn_recv_data(struct netconn *conn, void **new_buf)
{
  void *buf = NULL;
  u16_t len;
#if LWIP_TCP
  API_MSG_VAR_DECLARE(msg);
#if LWIP_MPU_COMPATIBLE
  msg = NULL;
#endif
#endif /* LWIP_TCP */
 
  LWIP_ERROR("netconn_recv: invalid pointer", (new_buf != NULL), return ERR_ARG;);
  *new_buf = NULL;
  LWIP_ERROR("netconn_recv: invalid conn",    (conn != NULL),    return ERR_ARG;);
#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
  if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
#endif /* (LWIP_UDP || LWIP_RAW) */
  {
    if (!sys_mbox_valid(&conn->recvmbox)) {
      /* This happens when calling this function after receiving FIN */
      return sys_mbox_valid(&conn->acceptmbox) ? ERR_CONN : ERR_CLSD;
    }
  }
#endif /* LWIP_TCP */
  LWIP_ERROR("netconn_recv: invalid recvmbox", sys_mbox_valid(&conn->recvmbox), return ERR_CONN;);
 
  if (ERR_IS_FATAL(conn->last_err)) {
    /* don't recv on fatal errors: this might block the application task
       waiting on recvmbox forever! */
    /* @todo: this does not allow us to fetch data that has been put into recvmbox
       before the fatal error occurred - is that a problem? */
    return conn->last_err;
  }
#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
  if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
#endif /* (LWIP_UDP || LWIP_RAW) */
  {
    API_MSG_VAR_ALLOC(msg);
  }
#endif /* LWIP_TCP */
 
#if LWIP_SO_RCVTIMEO
  if (sys_arch_mbox_fetch(&conn->recvmbox, &buf, conn->recv_timeout) == SYS_ARCH_TIMEOUT) {
#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
    if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
#endif /* (LWIP_UDP || LWIP_RAW) */
    {
      API_MSG_VAR_FREE(msg);
    }
#endif /* LWIP_TCP */
    return ERR_TIMEOUT;
  }
#else
  sys_arch_mbox_fetch(&conn->recvmbox, &buf, 0);
#endif /* LWIP_SO_RCVTIMEO*/
 
#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
  if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
#endif /* (LWIP_UDP || LWIP_RAW) */
  {
    /* Let the stack know that we have taken the data. */
    /* @todo: Speedup: Don't block and wait for the answer here
       (to prevent multiple thread-switches). */
    API_MSG_VAR_REF(msg).conn = conn;
    if (buf != NULL) {
      API_MSG_VAR_REF(msg).msg.r.len = ((struct pbuf *)buf)->tot_len;
    } else {
      API_MSG_VAR_REF(msg).msg.r.len = 1;
    }
 
    /* don't care for the return value of lwip_netconn_do_recv */
    netconn_apimsg(lwip_netconn_do_recv, &API_MSG_VAR_REF(msg));
    API_MSG_VAR_FREE(msg);
 
    /* If we are closed, we indicate that we no longer wish to use the socket */
    if (buf == NULL) {
      API_EVENT(conn, NETCONN_EVT_RCVMINUS, 0);
      if (conn->pcb.ip == NULL) {
        /* race condition: RST during recv */
        return conn->last_err == ERR_OK ? ERR_RST : conn->last_err;
      }
      /* RX side is closed, so deallocate the recvmbox */
      netconn_close_shutdown(conn, NETCONN_SHUT_RD);
      /* Don' store ERR_CLSD as conn->err since we are only half-closed */
      return ERR_CLSD;
    }
    len = ((struct pbuf *)buf)->tot_len;
  }
#endif /* LWIP_TCP */
#if LWIP_TCP && (LWIP_UDP || LWIP_RAW)
  else
#endif /* LWIP_TCP && (LWIP_UDP || LWIP_RAW) */
#if (LWIP_UDP || LWIP_RAW)
  {
    LWIP_ASSERT("buf != NULL", buf != NULL);
    len = netbuf_len((struct netbuf*)buf);
  }
#endif /* (LWIP_UDP || LWIP_RAW) */
 
#if LWIP_SO_RCVBUF
  SYS_ARCH_DEC(conn->recv_avail, len);
#endif /* LWIP_SO_RCVBUF */
  /* Register event with callback */
  API_EVENT(conn, NETCONN_EVT_RCVMINUS, len);
 
  LWIP_DEBUGF(API_LIB_DEBUG, ("netconn_recv_data: received %p, len=%"U16_F"\n", buf, len));
 
  *new_buf = buf;
  /* don't set conn->last_err: it's only ERR_OK, anyway */
  return ERR_OK;
}
 
err_t
netconn_recv_tcp_pbuf(struct netconn *conn, struct pbuf **new_buf)
{
  LWIP_ERROR("netconn_recv: invalid conn", (conn != NULL) &&
             NETCONNTYPE_GROUP(netconn_type(conn)) == NETCONN_TCP, return ERR_ARG;);
 
  return netconn_recv_data(conn, (void **)new_buf);
}
 
err_t
netconn_recv(struct netconn *conn, struct netbuf **new_buf)
{
#if LWIP_TCP
  struct netbuf *buf = NULL;
  err_t err;
#endif /* LWIP_TCP */
 
  LWIP_ERROR("netconn_recv: invalid pointer", (new_buf != NULL), return ERR_ARG;);
  *new_buf = NULL;
  LWIP_ERROR("netconn_recv: invalid conn",    (conn != NULL),    return ERR_ARG;);
 
#if LWIP_TCP
#if (LWIP_UDP || LWIP_RAW)
  if (NETCONNTYPE_GROUP(conn->type) == NETCONN_TCP)
#endif /* (LWIP_UDP || LWIP_RAW) */
  {
    struct pbuf *p = NULL;
    /* This is not a listening netconn, since recvmbox is set */
 
    buf = (struct netbuf *)memp_malloc(MEMP_NETBUF);
    if (buf == NULL) {
      return ERR_MEM;
    }
 
    err = netconn_recv_data(conn, (void **)&p);
    if (err != ERR_OK) {
      memp_free(MEMP_NETBUF, buf);
      return err;
    }
    LWIP_ASSERT("p != NULL", p != NULL);
 
    buf->p = p;
    buf->ptr = p;
    buf->port = 0;
    ip_addr_set_zero(&buf->addr);
    *new_buf = buf;
    /* don't set conn->last_err: it's only ERR_OK, anyway */
    return ERR_OK;
  }
#endif /* LWIP_TCP */
#if LWIP_TCP && (LWIP_UDP || LWIP_RAW)
  else
#endif /* LWIP_TCP && (LWIP_UDP || LWIP_RAW) */
  {
#if (LWIP_UDP || LWIP_RAW)
    return netconn_recv_data(conn, (void **)new_buf);
#endif /* (LWIP_UDP || LWIP_RAW) */
  }
}
 
err_t
netconn_sendto(struct netconn *conn, struct netbuf *buf, const ip_addr_t *addr, u16_t port)
{
  if (buf != NULL) {
    ip_addr_set(&buf->addr, addr);
    buf->port = port;
    return netconn_send(conn, buf);
  }
  return ERR_VAL;
}
 
err_t
netconn_send(struct netconn *conn, struct netbuf *buf)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  LWIP_ERROR("netconn_send: invalid conn",  (conn != NULL), return ERR_ARG;);
 
  LWIP_DEBUGF(API_LIB_DEBUG, ("netconn_send: sending %"U16_F" bytes\n", buf->p->tot_len));
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.b = buf;
  err = netconn_apimsg(lwip_netconn_do_send, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_write_partly(struct netconn *conn, const void *dataptr, size_t size,
                     u8_t apiflags, size_t *bytes_written)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
  u8_t dontblock;
 
  LWIP_ERROR("netconn_write: invalid conn",  (conn != NULL), return ERR_ARG;);
  LWIP_ERROR("netconn_write: invalid conn->type",  (NETCONNTYPE_GROUP(conn->type)== NETCONN_TCP), return ERR_VAL;);
  if (size == 0) {
    return ERR_OK;
  }
  dontblock = netconn_is_nonblocking(conn) || (apiflags & NETCONN_DONTBLOCK);
#if LWIP_SO_SNDTIMEO
  if (conn->send_timeout != 0) {
    dontblock = 1;
  }
#endif /* LWIP_SO_SNDTIMEO */
  if (dontblock && !bytes_written) {
    /* This implies netconn_write() cannot be used for non-blocking send, since
       it has no way to return the number of bytes written. */
    return ERR_VAL;
  }
 
  API_MSG_VAR_ALLOC(msg);
  /* non-blocking write sends as much  */
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.w.dataptr = dataptr;
  API_MSG_VAR_REF(msg).msg.w.apiflags = apiflags;
  API_MSG_VAR_REF(msg).msg.w.len = size;
#if LWIP_SO_SNDTIMEO
  if (conn->send_timeout != 0) {
    /* get the time we started, which is later compared to
        sys_now() + conn->send_timeout */
    API_MSG_VAR_REF(msg).msg.w.time_started = sys_now();
  } else {
    API_MSG_VAR_REF(msg).msg.w.time_started = 0;
  }
#endif /* LWIP_SO_SNDTIMEO */
 
  /* For locking the core: this _can_ be delayed on low memory/low send buffer,
     but if it is, this is done inside api_msg.c:do_write(), so we can use the
     non-blocking version here. */
  err = netconn_apimsg(lwip_netconn_do_write, &API_MSG_VAR_REF(msg));
  if ((err == ERR_OK) && (bytes_written != NULL)) {
    if (dontblock) {
      /* nonblocking write: maybe the data has been sent partly */
      *bytes_written = API_MSG_VAR_REF(msg).msg.w.len;
    } else {
      /* blocking call succeeded: all data has been sent if it */
      *bytes_written = size;
    }
  }
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
static err_t
netconn_close_shutdown(struct netconn *conn, u8_t how)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
  LWIP_UNUSED_ARG(how);
 
  LWIP_ERROR("netconn_close: invalid conn",  (conn != NULL), return ERR_ARG;);
 
  API_MSG_VAR_ALLOC(msg);
  API_MSG_VAR_REF(msg).conn = conn;
#if LWIP_TCP
  /* shutting down both ends is the same as closing */
  API_MSG_VAR_REF(msg).msg.sd.shut = how;
#if LWIP_SO_SNDTIMEO || LWIP_SO_LINGER
  /* get the time we started, which is later compared to
     sys_now() + conn->send_timeout */
  API_MSG_VAR_REF(msg).msg.sd.time_started = sys_now();
#else /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
  API_MSG_VAR_REF(msg).msg.sd.polls_left =
    ((LWIP_TCP_CLOSE_TIMEOUT_MS_DEFAULT + TCP_SLOW_INTERVAL - 1) / TCP_SLOW_INTERVAL) + 1;
#endif /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
#endif /* LWIP_TCP */
  err = netconn_apimsg(lwip_netconn_do_close, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
 
err_t
netconn_close(struct netconn *conn)
{
  /* shutting down both ends is the same as closing */
  return netconn_close_shutdown(conn, NETCONN_SHUT_RDWR);
}
 
err_t
netconn_shutdown(struct netconn *conn, u8_t shut_rx, u8_t shut_tx)
{
  return netconn_close_shutdown(conn, (shut_rx ? NETCONN_SHUT_RD : 0) | (shut_tx ? NETCONN_SHUT_WR : 0));
}
 
#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)
{
  API_MSG_VAR_DECLARE(msg);
  err_t err;
 
  LWIP_ERROR("netconn_join_leave_group: invalid conn",  (conn != NULL), return ERR_ARG;);
 
  API_MSG_VAR_ALLOC(msg);
 
#if LWIP_IPV4
  /* Don't propagate NULL pointer (IP_ADDR_ANY alias) to subsequent functions */
  if (multiaddr == NULL) {
    multiaddr = IP4_ADDR_ANY;
  }
  if (netif_addr == NULL) {
    netif_addr = IP4_ADDR_ANY;
  }
#endif /* LWIP_IPV4 */
 
  API_MSG_VAR_REF(msg).conn = conn;
  API_MSG_VAR_REF(msg).msg.jl.multiaddr = API_MSG_VAR_REF(multiaddr);
  API_MSG_VAR_REF(msg).msg.jl.netif_addr = API_MSG_VAR_REF(netif_addr);
  API_MSG_VAR_REF(msg).msg.jl.join_or_leave = join_or_leave;
  err = netconn_apimsg(lwip_netconn_do_join_leave_group, &API_MSG_VAR_REF(msg));
  API_MSG_VAR_FREE(msg);
 
  return err;
}
#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)
#else
err_t
netconn_gethostbyname(const char *name, ip_addr_t *addr)
#endif
{
  API_VAR_DECLARE(struct dns_api_msg, msg);
#if !LWIP_MPU_COMPATIBLE
  sys_sem_t sem;
#endif /* LWIP_MPU_COMPATIBLE */
  err_t err;
  err_t cberr;
 
  LWIP_ERROR("netconn_gethostbyname: invalid name", (name != NULL), return ERR_ARG;);
  LWIP_ERROR("netconn_gethostbyname: invalid addr", (addr != NULL), return ERR_ARG;);
#if LWIP_MPU_COMPATIBLE
  if (strlen(name) >= DNS_MAX_NAME_LENGTH) {
    return ERR_ARG;
  }
#endif
 
  API_VAR_ALLOC(struct dns_api_msg, MEMP_DNS_API_MSG, msg, ERR_MEM);
#if LWIP_MPU_COMPATIBLE
  strncpy(API_VAR_REF(msg).name, name, DNS_MAX_NAME_LENGTH-1);
  API_VAR_REF(msg).name[DNS_MAX_NAME_LENGTH-1] = 0;
#else /* LWIP_MPU_COMPATIBLE */
  msg.err = &err;
  msg.sem = &sem;
  API_VAR_REF(msg).addr = API_VAR_REF(addr);
  API_VAR_REF(msg).name = name;
#endif /* LWIP_MPU_COMPATIBLE */
#if LWIP_IPV4 && LWIP_IPV6
  API_VAR_REF(msg).dns_addrtype = dns_addrtype;
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_NETCONN_SEM_PER_THREAD
  API_VAR_REF(msg).sem = LWIP_NETCONN_THREAD_SEM_GET();
#else /* LWIP_NETCONN_SEM_PER_THREAD*/
  err = sys_sem_new(API_EXPR_REF(API_VAR_REF(msg).sem), 0);
  if (err != ERR_OK) {
    API_VAR_FREE(MEMP_DNS_API_MSG, msg);
    return err;
  }
#endif /* LWIP_NETCONN_SEM_PER_THREAD */
 
  cberr = tcpip_callback(lwip_netconn_do_gethostbyname, &API_VAR_REF(msg));
  if (cberr != ERR_OK) {
#if !LWIP_NETCONN_SEM_PER_THREAD
    sys_sem_free(API_EXPR_REF(API_VAR_REF(msg).sem));
#endif /* !LWIP_NETCONN_SEM_PER_THREAD */
    API_VAR_FREE(MEMP_DNS_API_MSG, msg);
    return cberr;
  }
  sys_sem_wait(API_EXPR_REF_SEM(API_VAR_REF(msg).sem));
#if !LWIP_NETCONN_SEM_PER_THREAD
  sys_sem_free(API_EXPR_REF(API_VAR_REF(msg).sem));
#endif /* !LWIP_NETCONN_SEM_PER_THREAD */
 
#if LWIP_MPU_COMPATIBLE
  *addr = msg->addr;
  err = msg->err;
#endif /* LWIP_MPU_COMPATIBLE */
 
  API_VAR_FREE(MEMP_DNS_API_MSG, msg);
  return err;
}
#endif /* LWIP_DNS*/
 
#if LWIP_NETCONN_SEM_PER_THREAD
void
netconn_thread_init(void)
{
  sys_sem_t *sem = LWIP_NETCONN_THREAD_SEM_GET();
  if ((sem == NULL) || !sys_sem_valid(sem)) {
    /* call alloc only once */
    LWIP_NETCONN_THREAD_SEM_ALLOC();
    LWIP_ASSERT("LWIP_NETCONN_THREAD_SEM_ALLOC() failed", sys_sem_valid(LWIP_NETCONN_THREAD_SEM_GET()));
  }
}
 
void
netconn_thread_cleanup(void)
{
  sys_sem_t *sem = LWIP_NETCONN_THREAD_SEM_GET();
  if ((sem != NULL) && sys_sem_valid(sem)) {
    /* call free only once */
    LWIP_NETCONN_THREAD_SEM_FREE();
  }
}
#endif /* LWIP_NETCONN_SEM_PER_THREAD */
 
#endif /* LWIP_NETCONN */