text: /**
   * @file
   * Sockets BSD-Like API module
   *
   * @defgroup socket Socket API
   * @ingroup sequential_api
   * BSD-style socket API.\n
   * Thread-safe, to be called from non-TCPIP threads only.\n
   * Can be activated by defining @ref LWIP_SOCKET to 1.\n
   * Header is in posix/sys/socket.h\b
   */
  
  /*
   * 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>
   *
   * Improved by Marc Boucher <marc@mbsi.ca> and David Haas <dhaas@alum.rpi.edu>
   *
   */
  
  #include "lwip/opt.h"
  
  #if LWIP_SOCKET /* don't build if not configured for use in lwipopts.h */
  
  #include "lwip/sockets.h"
  #include "lwip/api.h"
  #include "lwip/sys.h"
  #include "lwip/igmp.h"
  #include "lwip/inet.h"
  #include "lwip/tcp.h"
  #include "lwip/raw.h"
  #include "lwip/udp.h"
  #include "lwip/memp.h"
  #include "lwip/pbuf.h"
  #include "lwip/priv/tcpip_priv.h"
  #if LWIP_CHECKSUM_ON_COPY
  #include "lwip/inet_chksum.h"
  #endif
  
  #include <string.h>
  
  /* If the netconn API is not required publicly, then we include the necessary
     files here to get the implementation */
  #if !LWIP_NETCONN
  #undef LWIP_NETCONN
  #define LWIP_NETCONN 1
  #include "api_msg.c"
  #include "api_lib.c"
  #include "netbuf.c"
  #undef LWIP_NETCONN
  #define LWIP_NETCONN 0
  #endif
  
  #if LWIP_IPV4
  #define IP4ADDR_PORT_TO_SOCKADDR(sin, ipaddr, port) do { \
        (sin)->sin_len = sizeof(struct sockaddr_in); \
        (sin)->sin_family = AF_INET; \
        (sin)->sin_port = lwip_htons((port)); \
        inet_addr_from_ip4addr(&(sin)->sin_addr, ipaddr); \
        memset((sin)->sin_zero, 0, SIN_ZERO_LEN); }while(0)
  #define SOCKADDR4_TO_IP4ADDR_PORT(sin, ipaddr, port) do { \
      inet_addr_to_ip4addr(ip_2_ip4(ipaddr), &((sin)->sin_addr)); \
      (port) = lwip_ntohs((sin)->sin_port); }while(0)
  #endif /* LWIP_IPV4 */
  
  #if LWIP_IPV6
  #define IP6ADDR_PORT_TO_SOCKADDR(sin6, ipaddr, port) do { \
        (sin6)->sin6_len = sizeof(struct sockaddr_in6); \
        (sin6)->sin6_family = AF_INET6; \
        (sin6)->sin6_port = lwip_htons((port)); \
        (sin6)->sin6_flowinfo = 0; \
        inet6_addr_from_ip6addr(&(sin6)->sin6_addr, ipaddr); \
        (sin6)->sin6_scope_id = 0; }while(0)
  #define SOCKADDR6_TO_IP6ADDR_PORT(sin6, ipaddr, port) do { \
      inet6_addr_to_ip6addr(ip_2_ip6(ipaddr), &((sin6)->sin6_addr)); \
      (port) = lwip_ntohs((sin6)->sin6_port); }while(0)
  #endif /* LWIP_IPV6 */
  
  #if LWIP_IPV4 && LWIP_IPV6
  static void sockaddr_to_ipaddr_port(const struct sockaddr* sockaddr, ip_addr_t* ipaddr, u16_t* port);
  
  #define IS_SOCK_ADDR_LEN_VALID(namelen)  (((namelen) == sizeof(struct sockaddr_in)) || \
                                           ((namelen) == sizeof(struct sockaddr_in6)))
  #define IS_SOCK_ADDR_TYPE_VALID(name)    (((name)->sa_family == AF_INET) || \
                                           ((name)->sa_family == AF_INET6))
  #define SOCK_ADDR_TYPE_MATCH(name, sock) \
         ((((name)->sa_family == AF_INET) && !(NETCONNTYPE_ISIPV6((sock)->conn->type))) || \
         (((name)->sa_family == AF_INET6) && (NETCONNTYPE_ISIPV6((sock)->conn->type))))
  #define IPADDR_PORT_TO_SOCKADDR(sockaddr, ipaddr, port) do { \
      if (IP_IS_V6(ipaddr)) { \
        IP6ADDR_PORT_TO_SOCKADDR((struct sockaddr_in6*)(void*)(sockaddr), ip_2_ip6(ipaddr), port); \
      } else { \
        IP4ADDR_PORT_TO_SOCKADDR((struct sockaddr_in*)(void*)(sockaddr), ip_2_ip4(ipaddr), port); \
      } } while(0)
  #define SOCKADDR_TO_IPADDR_PORT(sockaddr, ipaddr, port) sockaddr_to_ipaddr_port(sockaddr, ipaddr, &(port))
  #define DOMAIN_TO_NETCONN_TYPE(domain, type) (((domain) == AF_INET) ? \
    (type) : (enum netconn_type)((type) | NETCONN_TYPE_IPV6))
  #elif LWIP_IPV6 /* LWIP_IPV4 && LWIP_IPV6 */
  #define IS_SOCK_ADDR_LEN_VALID(namelen)  ((namelen) == sizeof(struct sockaddr_in6))
  #define IS_SOCK_ADDR_TYPE_VALID(name)    ((name)->sa_family == AF_INET6)
  #define SOCK_ADDR_TYPE_MATCH(name, sock) 1
  #define IPADDR_PORT_TO_SOCKADDR(sockaddr, ipaddr, port) \
          IP6ADDR_PORT_TO_SOCKADDR((struct sockaddr_in6*)(void*)(sockaddr), ip_2_ip6(ipaddr), port)
  #define SOCKADDR_TO_IPADDR_PORT(sockaddr, ipaddr, port) \
          SOCKADDR6_TO_IP6ADDR_PORT((const struct sockaddr_in6*)(const void*)(sockaddr), ipaddr, port)
  #define DOMAIN_TO_NETCONN_TYPE(domain, netconn_type) (netconn_type)
  #else /*-> LWIP_IPV4: LWIP_IPV4 && LWIP_IPV6 */
  #define IS_SOCK_ADDR_LEN_VALID(namelen)  ((namelen) == sizeof(struct sockaddr_in))
  #define IS_SOCK_ADDR_TYPE_VALID(name)    ((name)->sa_family == AF_INET)
  #define SOCK_ADDR_TYPE_MATCH(name, sock) 1
  #define IPADDR_PORT_TO_SOCKADDR(sockaddr, ipaddr, port) \
          IP4ADDR_PORT_TO_SOCKADDR((struct sockaddr_in*)(void*)(sockaddr), ip_2_ip4(ipaddr), port)
  #define SOCKADDR_TO_IPADDR_PORT(sockaddr, ipaddr, port) \
          SOCKADDR4_TO_IP4ADDR_PORT((const struct sockaddr_in*)(const void*)(sockaddr), ipaddr, port)
  #define DOMAIN_TO_NETCONN_TYPE(domain, netconn_type) (netconn_type)
  #endif /* LWIP_IPV6 */
  
  #define IS_SOCK_ADDR_TYPE_VALID_OR_UNSPEC(name)    (((name)->sa_family == AF_UNSPEC) || \
                                                      IS_SOCK_ADDR_TYPE_VALID(name))
  #define SOCK_ADDR_TYPE_MATCH_OR_UNSPEC(name, sock) (((name)->sa_family == AF_UNSPEC) || \
                                                      SOCK_ADDR_TYPE_MATCH(name, sock))
  #define IS_SOCK_ADDR_ALIGNED(name)      ((((mem_ptr_t)(name)) % 4) == 0)
  
  
  #define LWIP_SOCKOPT_CHECK_OPTLEN(optlen, opttype) do { if ((optlen) < sizeof(opttype)) { return EINVAL; }}while(0)
  #define LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, optlen, opttype) do { \
    LWIP_SOCKOPT_CHECK_OPTLEN(optlen, opttype); \
    if ((sock)->conn == NULL) { return EINVAL; } }while(0)
  #define LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, opttype) do { \
    LWIP_SOCKOPT_CHECK_OPTLEN(optlen, opttype); \
    if (((sock)->conn == NULL) || ((sock)->conn->pcb.tcp == NULL)) { return EINVAL; } }while(0)
  #define LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, opttype, netconntype) do { \
    LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, opttype); \
    if (NETCONNTYPE_GROUP(netconn_type((sock)->conn)) != netconntype) { return ENOPROTOOPT; } }while(0)
  
  
  #define LWIP_SETGETSOCKOPT_DATA_VAR_REF(name)     API_VAR_REF(name)
  #define LWIP_SETGETSOCKOPT_DATA_VAR_DECLARE(name) API_VAR_DECLARE(struct lwip_setgetsockopt_data, name)
  #define LWIP_SETGETSOCKOPT_DATA_VAR_FREE(name)    API_VAR_FREE(MEMP_SOCKET_SETGETSOCKOPT_DATA, name)
  #if LWIP_MPU_COMPATIBLE
  #define LWIP_SETGETSOCKOPT_DATA_VAR_ALLOC(name, sock) do { \
    name = (struct lwip_setgetsockopt_data *)memp_malloc(MEMP_SOCKET_SETGETSOCKOPT_DATA); \
    if (name == NULL) { \
      sock_set_errno(sock, ENOMEM); \
      return -1; \
    } }while(0)
  #else /* LWIP_MPU_COMPATIBLE */
  #define LWIP_SETGETSOCKOPT_DATA_VAR_ALLOC(name, sock)
  #endif /* LWIP_MPU_COMPATIBLE */
  
  #if LWIP_SO_SNDRCVTIMEO_NONSTANDARD
  #define LWIP_SO_SNDRCVTIMEO_OPTTYPE int
  #define LWIP_SO_SNDRCVTIMEO_SET(optval, val) (*(int *)(optval) = (val))
  #define LWIP_SO_SNDRCVTIMEO_GET_MS(optval)   ((s32_t)*(const int*)(optval))
  #else
  #define LWIP_SO_SNDRCVTIMEO_OPTTYPE struct timeval
  #define LWIP_SO_SNDRCVTIMEO_SET(optval, val)  do { \
    s32_t loc = (val); \
    ((struct timeval *)(optval))->tv_sec = (loc) / 1000U; \
    ((struct timeval *)(optval))->tv_usec = ((loc) % 1000U) * 1000U; }while(0)
  #define LWIP_SO_SNDRCVTIMEO_GET_MS(optval) ((((const struct timeval *)(optval))->tv_sec * 1000U) + (((const struct timeval *)(optval))->tv_usec / 1000U))
  #endif
  
  #define NUM_SOCKETS MEMP_NUM_NETCONN
  
  /** This is overridable for the rare case where more than 255 threads
   * select on the same socket...
   */
  #ifndef SELWAIT_T
  #define SELWAIT_T u8_t
  #endif
  
  /** Contains all internal pointers and states used for a socket */
  struct lwip_sock {
    /** sockets currently are built on netconns, each socket has one netconn */
    struct netconn *conn;
    /** data that was left from the previous read */
    void *lastdata;
    /** offset in the data that was left from the previous read */
    u16_t lastoffset;
    /** number of times data was received, set by event_callback(),
        tested by the receive and select functions */
    s16_t rcvevent;
    /** number of times data was ACKed (free send buffer), set by event_callback(),
        tested by select */
    u16_t sendevent;
    /** error happened for this socket, set by event_callback(), tested by select */
    u16_t errevent;
    /** last error that occurred on this socket (in fact, all our errnos fit into an u8_t) */
    u8_t err;
    /** counter of how many threads are waiting for this socket using select */
    SELWAIT_T select_waiting;
  };
  
  #if LWIP_NETCONN_SEM_PER_THREAD
  #define SELECT_SEM_T        sys_sem_t*
  #define SELECT_SEM_PTR(sem) (sem)
  #else /* LWIP_NETCONN_SEM_PER_THREAD */
  #define SELECT_SEM_T        sys_sem_t
  #define SELECT_SEM_PTR(sem) (&(sem))
  #endif /* LWIP_NETCONN_SEM_PER_THREAD */
  
  /** Description for a task waiting in select */
  struct lwip_select_cb {
    /** Pointer to the next waiting task */
    struct lwip_select_cb *next;
    /** Pointer to the previous waiting task */
    struct lwip_select_cb *prev;
    /** readset passed to select */
    fd_set *readset;
    /** writeset passed to select */
    fd_set *writeset;
    /** unimplemented: exceptset passed to select */
    fd_set *exceptset;
    /** don't signal the same semaphore twice: set to 1 when signalled */
    int sem_signalled;
    /** semaphore to wake up a task waiting for select */
    SELECT_SEM_T sem;
  };
  
  /** A struct sockaddr replacement that has the same alignment as sockaddr_in/
   *  sockaddr_in6 if instantiated.
   */
  union sockaddr_aligned {
     struct sockaddr sa;
  #if LWIP_IPV6
     struct sockaddr_in6 sin6;
  #endif /* LWIP_IPV6 */
  #if LWIP_IPV4
     struct sockaddr_in sin;
  #endif /* LWIP_IPV4 */
  };
  
  #if LWIP_IGMP
  /* Define the number of IPv4 multicast memberships, default is one per socket */
  #ifndef LWIP_SOCKET_MAX_MEMBERSHIPS
  #define LWIP_SOCKET_MAX_MEMBERSHIPS NUM_SOCKETS
  #endif
  
  /* This is to keep track of IP_ADD_MEMBERSHIP calls to drop the membership when
     a socket is closed */
  struct lwip_socket_multicast_pair {
    /** the socket */
    struct lwip_sock* sock;
    /** the interface address */
    ip4_addr_t if_addr;
    /** the group address */
    ip4_addr_t multi_addr;
  };
  
  struct lwip_socket_multicast_pair socket_ipv4_multicast_memberships[LWIP_SOCKET_MAX_MEMBERSHIPS];
  
  static int  lwip_socket_register_membership(int s, const ip4_addr_t *if_addr, const ip4_addr_t *multi_addr);
  static void lwip_socket_unregister_membership(int s, const ip4_addr_t *if_addr, const ip4_addr_t *multi_addr);
  static void lwip_socket_drop_registered_memberships(int s);
  #endif /* LWIP_IGMP */
  
  /** The global array of available sockets */
  static struct lwip_sock sockets[NUM_SOCKETS];
  /** The global list of tasks waiting for select */
  static struct lwip_select_cb *select_cb_list;
  /** This counter is increased from lwip_select when the list is changed
      and checked in event_callback to see if it has changed. */
  static volatile int select_cb_ctr;
  
  #if LWIP_SOCKET_SET_ERRNO
  #ifndef set_errno
  #define set_errno(err) do { if (err) { errno = (err); } } while(0)
  #endif
  #else /* LWIP_SOCKET_SET_ERRNO */
  #define set_errno(err)
  #endif /* LWIP_SOCKET_SET_ERRNO */
  
  #define sock_set_errno(sk, e) do { \
    const int sockerr = (e); \
    sk->err = (u8_t)sockerr; \
    set_errno(sockerr); \
  } while (0)
  
  /* Forward declaration of some functions */
  static void event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len);
  #if !LWIP_TCPIP_CORE_LOCKING
  static void lwip_getsockopt_callback(void *arg);
  static void lwip_setsockopt_callback(void *arg);
  #endif
  static u8_t lwip_getsockopt_impl(int s, int level, int optname, void *optval, socklen_t *optlen);
  static u8_t lwip_setsockopt_impl(int s, int level, int optname, const void *optval, socklen_t optlen);
  
  #if LWIP_IPV4 && LWIP_IPV6
  static void
  sockaddr_to_ipaddr_port(const struct sockaddr* sockaddr, ip_addr_t* ipaddr, u16_t* port)
  {
    if ((sockaddr->sa_family) == AF_INET6) {
      SOCKADDR6_TO_IP6ADDR_PORT((const struct sockaddr_in6*)(const void*)(sockaddr), ipaddr, *port);
      ipaddr->type = IPADDR_TYPE_V6;
    } else {
      SOCKADDR4_TO_IP4ADDR_PORT((const struct sockaddr_in*)(const void*)(sockaddr), ipaddr, *port);
      ipaddr->type = IPADDR_TYPE_V4;
    }
  }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
  /** LWIP_NETCONN_SEM_PER_THREAD==1: initialize thread-local semaphore */
  void
  lwip_socket_thread_init(void)
  {
     netconn_thread_init();
  }
  
  /** LWIP_NETCONN_SEM_PER_THREAD==1: destroy thread-local semaphore */
  void
  lwip_socket_thread_cleanup(void)
  {
     netconn_thread_cleanup();
  }
  
  /**
   * Map a externally used socket index to the internal socket representation.
   *
   * @param s externally used socket index
   * @return struct lwip_sock for the socket or NULL if not found
   */
  static struct lwip_sock *
  get_socket(int s)
  {
    struct lwip_sock *sock;
  
    s -= LWIP_SOCKET_OFFSET;
  
    if ((s < 0) || (s >= NUM_SOCKETS)) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("get_socket(%d): invalid\n", s + LWIP_SOCKET_OFFSET));
      set_errno(EBADF);
      return NULL;
    }
  
    sock = &sockets[s];
  
    if (!sock->conn) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("get_socket(%d): not active\n", s + LWIP_SOCKET_OFFSET));
      set_errno(EBADF);
      return NULL;
    }
  
    return sock;
  }
  
  /**
   * Same as get_socket but doesn't set errno
   *
   * @param s externally used socket index
   * @return struct lwip_sock for the socket or NULL if not found
   */
  static struct lwip_sock *
  tryget_socket(int s)
  {
    s -= LWIP_SOCKET_OFFSET;
    if ((s < 0) || (s >= NUM_SOCKETS)) {
      return NULL;
    }
    if (!sockets[s].conn) {
      return NULL;
    }
    return &sockets[s];
  }
  
  /**
   * Allocate a new socket for a given netconn.
   *
   * @param newconn the netconn for which to allocate a socket
   * @param accepted 1 if socket has been created by accept(),
   *                 0 if socket has been created by socket()
   * @return the index of the new socket; -1 on error
   */
  static int
  alloc_socket(struct netconn *newconn, int accepted)
  {
    int i;
    SYS_ARCH_DECL_PROTECT(lev);
  
    /* allocate a new socket identifier */
    for (i = 0; i < NUM_SOCKETS; ++i) {
      /* Protect socket array */
      SYS_ARCH_PROTECT(lev);
      if (!sockets[i].conn && (sockets[i].select_waiting == 0)) {
        sockets[i].conn       = newconn;
        /* The socket is not yet known to anyone, so no need to protect
           after having marked it as used. */
        SYS_ARCH_UNPROTECT(lev);
        sockets[i].lastdata   = NULL;
        sockets[i].lastoffset = 0;
        sockets[i].rcvevent   = 0;
        /* TCP sendbuf is empty, but the socket is not yet writable until connected
         * (unless it has been created by accept()). */
        sockets[i].sendevent  = (NETCONNTYPE_GROUP(newconn->type) == NETCONN_TCP ? (accepted != 0) : 1);
        sockets[i].errevent   = 0;
        sockets[i].err        = 0;
        return i + LWIP_SOCKET_OFFSET;
      }
      SYS_ARCH_UNPROTECT(lev);
    }
    return -1;
  }
  
  /** Free a socket. The socket's netconn must have been
   * delete before!
   *
   * @param sock the socket to free
   * @param is_tcp != 0 for TCP sockets, used to free lastdata
   */
  static void
  free_socket(struct lwip_sock *sock, int is_tcp)
  {
    void *lastdata;
  
    lastdata         = sock->lastdata;
    sock->lastdata   = NULL;
    sock->lastoffset = 0;
    sock->err        = 0;
  
    /* Protect socket array */
    SYS_ARCH_SET(sock->conn, NULL);
    /* don't use 'sock' after this line, as another task might have allocated it */
  
    if (lastdata != NULL) {
      if (is_tcp) {
        pbuf_free((struct pbuf *)lastdata);
      } else {
        netbuf_delete((struct netbuf *)lastdata);
      }
    }
  }
  
  /* Below this, the well-known socket functions are implemented.
   * Use google.com or opengroup.org to get a good description :-)
   *
   * Exceptions are documented!
   */
  
  int
  lwip_accept(int s, struct sockaddr *addr, socklen_t *addrlen)
  {
    struct lwip_sock *sock, *nsock;
    struct netconn *newconn;
    ip_addr_t naddr;
    u16_t port = 0;
    int newsock;
    err_t err;
    SYS_ARCH_DECL_PROTECT(lev);
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d)...\n", s));
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (netconn_is_nonblocking(sock->conn) && (sock->rcvevent <= 0)) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d): returning EWOULDBLOCK\n", s));
      set_errno(EWOULDBLOCK);
      return -1;
    }
  
    /* wait for a new connection */
    err = netconn_accept(sock->conn, &newconn);
    if (err != ERR_OK) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d): netconn_acept failed, err=%d\n", s, err));
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
        sock_set_errno(sock, EOPNOTSUPP);
      } else if (err == ERR_CLSD) {
        sock_set_errno(sock, EINVAL);
      } else {
        sock_set_errno(sock, err_to_errno(err));
      }
      return -1;
    }
    LWIP_ASSERT("newconn != NULL", newconn != NULL);
  
    newsock = alloc_socket(newconn, 1);
    if (newsock == -1) {
      netconn_delete(newconn);
      sock_set_errno(sock, ENFILE);
      return -1;
    }
    LWIP_ASSERT("invalid socket index", (newsock >= LWIP_SOCKET_OFFSET) && (newsock < NUM_SOCKETS + LWIP_SOCKET_OFFSET));
    LWIP_ASSERT("newconn->callback == event_callback", newconn->callback == event_callback);
    nsock = &sockets[newsock - LWIP_SOCKET_OFFSET];
  
    /* See event_callback: If data comes in right away after an accept, even
     * though the server task might not have created a new socket yet.
     * In that case, newconn->socket is counted down (newconn->socket--),
     * so nsock->rcvevent is >= 1 here!
     */
    SYS_ARCH_PROTECT(lev);
    nsock->rcvevent += (s16_t)(-1 - newconn->socket);
    newconn->socket = newsock;
    SYS_ARCH_UNPROTECT(lev);
  
    /* Note that POSIX only requires us to check addr is non-NULL. addrlen must
     * not be NULL if addr is valid.
     */
    if (addr != NULL) {
      union sockaddr_aligned tempaddr;
      /* get the IP address and port of the remote host */
      err = netconn_peer(newconn, &naddr, &port);
      if (err != ERR_OK) {
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d): netconn_peer failed, err=%d\n", s, err));
        netconn_delete(newconn);
        free_socket(nsock, 1);
        sock_set_errno(sock, err_to_errno(err));
        return -1;
      }
      LWIP_ASSERT("addr valid but addrlen NULL", addrlen != NULL);
  
      IPADDR_PORT_TO_SOCKADDR(&tempaddr, &naddr, port);
      if (*addrlen > tempaddr.sa.sa_len) {
        *addrlen = tempaddr.sa.sa_len;
      }
      MEMCPY(addr, &tempaddr, *addrlen);
  
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d) returning new sock=%d addr=", s, newsock));
      ip_addr_debug_print_val(SOCKETS_DEBUG, naddr);
      LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F"\n", port));
    } else {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_accept(%d) returning new sock=%d", s, newsock));
    }
  
    sock_set_errno(sock, 0);
    return newsock;
  }
  
  int
  lwip_bind(int s, const struct sockaddr *name, socklen_t namelen)
  {
    struct lwip_sock *sock;
    ip_addr_t local_addr;
    u16_t local_port;
    err_t err;
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (!SOCK_ADDR_TYPE_MATCH(name, sock)) {
      /* sockaddr does not match socket type (IPv4/IPv6) */
      sock_set_errno(sock, err_to_errno(ERR_VAL));
      return -1;
    }
  
    /* check size, family and alignment of 'name' */
    LWIP_ERROR("lwip_bind: invalid address", (IS_SOCK_ADDR_LEN_VALID(namelen) &&
               IS_SOCK_ADDR_TYPE_VALID(name) && IS_SOCK_ADDR_ALIGNED(name)),
               sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
    LWIP_UNUSED_ARG(namelen);
  
    SOCKADDR_TO_IPADDR_PORT(name, &local_addr, local_port);
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_bind(%d, addr=", s));
    ip_addr_debug_print_val(SOCKETS_DEBUG, local_addr);
    LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F")\n", local_port));
  
  #if LWIP_IPV4 && LWIP_IPV6
    /* Dual-stack: Unmap IPv4 mapped IPv6 addresses */
    if (IP_IS_V6_VAL(local_addr) && ip6_addr_isipv4mappedipv6(ip_2_ip6(&local_addr))) {
      unmap_ipv4_mapped_ipv6(ip_2_ip4(&local_addr), ip_2_ip6(&local_addr));
      IP_SET_TYPE_VAL(local_addr, IPADDR_TYPE_V4);
    }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
    err = netconn_bind(sock->conn, &local_addr, local_port);
  
    if (err != ERR_OK) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_bind(%d) failed, err=%d\n", s, err));
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_bind(%d) succeeded\n", s));
    sock_set_errno(sock, 0);
    return 0;
  }
  
  int
  lwip_close(int s)
  {
    struct lwip_sock *sock;
    int is_tcp = 0;
    err_t err;
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_close(%d)\n", s));
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (sock->conn != NULL) {
      is_tcp = NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP;
    } else {
      LWIP_ASSERT("sock->lastdata == NULL", sock->lastdata == NULL);
    }
  
  #if LWIP_IGMP
    /* drop all possibly joined IGMP memberships */
    lwip_socket_drop_registered_memberships(s);
  #endif /* LWIP_IGMP */
  
    err = netconn_delete(sock->conn);
    if (err != ERR_OK) {
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
  
    free_socket(sock, is_tcp);
    set_errno(0);
    return 0;
  }
  
  int
  lwip_connect(int s, const struct sockaddr *name, socklen_t namelen)
  {
    struct lwip_sock *sock;
    err_t err;
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (!SOCK_ADDR_TYPE_MATCH_OR_UNSPEC(name, sock)) {
      /* sockaddr does not match socket type (IPv4/IPv6) */
      sock_set_errno(sock, err_to_errno(ERR_VAL));
      return -1;
    }
  
    LWIP_UNUSED_ARG(namelen);
    if (name->sa_family == AF_UNSPEC) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_connect(%d, AF_UNSPEC)\n", s));
      err = netconn_disconnect(sock->conn);
    } else {
      ip_addr_t remote_addr;
      u16_t remote_port;
  
      /* check size, family and alignment of 'name' */
      LWIP_ERROR("lwip_connect: invalid address", IS_SOCK_ADDR_LEN_VALID(namelen) &&
                 IS_SOCK_ADDR_TYPE_VALID_OR_UNSPEC(name) && IS_SOCK_ADDR_ALIGNED(name),
                 sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
  
      SOCKADDR_TO_IPADDR_PORT(name, &remote_addr, remote_port);
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_connect(%d, addr=", s));
      ip_addr_debug_print_val(SOCKETS_DEBUG, remote_addr);
      LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F")\n", remote_port));
  
  #if LWIP_IPV4 && LWIP_IPV6
      /* Dual-stack: Unmap IPv4 mapped IPv6 addresses */
      if (IP_IS_V6_VAL(remote_addr) && ip6_addr_isipv4mappedipv6(ip_2_ip6(&remote_addr))) {
        unmap_ipv4_mapped_ipv6(ip_2_ip4(&remote_addr), ip_2_ip6(&remote_addr));
        IP_SET_TYPE_VAL(remote_addr, IPADDR_TYPE_V4);
      }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
      err = netconn_connect(sock->conn, &remote_addr, remote_port);
    }
  
    if (err != ERR_OK) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_connect(%d) failed, err=%d\n", s, err));
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_connect(%d) succeeded\n", s));
    sock_set_errno(sock, 0);
    return 0;
  }
  
  /**
   * Set a socket into listen mode.
   * The socket may not have been used for another connection previously.
   *
   * @param s the socket to set to listening mode
   * @param backlog (ATTENTION: needs TCP_LISTEN_BACKLOG=1)
   * @return 0 on success, non-zero on failure
   */
  int
  lwip_listen(int s, int backlog)
  {
    struct lwip_sock *sock;
    err_t err;
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_listen(%d, backlog=%d)\n", s, backlog));
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    /* limit the "backlog" parameter to fit in an u8_t */
    backlog = LWIP_MIN(LWIP_MAX(backlog, 0), 0xff);
  
    err = netconn_listen_with_backlog(sock->conn, (u8_t)backlog);
  
    if (err != ERR_OK) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_listen(%d) failed, err=%d\n", s, err));
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
        sock_set_errno(sock, EOPNOTSUPP);
        return -1;
      }
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
  
    sock_set_errno(sock, 0);
    return 0;
  }
  
  int
  lwip_recvfrom(int s, void *mem, size_t len, int flags,
                struct sockaddr *from, socklen_t *fromlen)
  {
    struct lwip_sock *sock;
    void             *buf = NULL;
    struct pbuf      *p;
    u16_t            buflen, copylen;
    int              off = 0;
    u8_t             done = 0;
    err_t            err;
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom(%d, %p, %"SZT_F", 0x%x, ..)\n", s, mem, len, flags));
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    do {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: top while sock->lastdata=%p\n", sock->lastdata));
      /* Check if there is data left from the last recv operation. */
      if (sock->lastdata) {
        buf = sock->lastdata;
      } else {
        /* If this is non-blocking call, then check first */
        if (((flags & MSG_DONTWAIT) || netconn_is_nonblocking(sock->conn)) &&
            (sock->rcvevent <= 0)) {
          if (off > 0) {
            /* already received data, return that */
            sock_set_errno(sock, 0);
            return off;
          }
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom(%d): returning EWOULDBLOCK\n", s));
          set_errno(EWOULDBLOCK);
          return -1;
        }
  
        /* No data was left from the previous operation, so we try to get
           some from the network. */
        if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
          err = netconn_recv_tcp_pbuf(sock->conn, (struct pbuf **)&buf);
        } else {
          err = netconn_recv(sock->conn, (struct netbuf **)&buf);
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: netconn_recv err=%d, netbuf=%p\n",
          err, buf));
  
        if (err != ERR_OK) {
          if (off > 0) {
            if (err == ERR_CLSD) {
              /* closed but already received data, ensure select gets the FIN, too */
              event_callback(sock->conn, NETCONN_EVT_RCVPLUS, 0);
            }
            /* already received data, return that */
            sock_set_errno(sock, 0);
            return off;
          }
          /* We should really do some error checking here. */
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom(%d): buf == NULL, error is \"%s\"!\n",
            s, lwip_strerr(err)));
          sock_set_errno(sock, err_to_errno(err));
          if (err == ERR_CLSD) {
            return 0;
          } else {
            return -1;
          }
        }
        LWIP_ASSERT("buf != NULL", buf != NULL);
        sock->lastdata = buf;
      }
  
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
        p = (struct pbuf *)buf;
      } else {
        p = ((struct netbuf *)buf)->p;
      }
      buflen = p->tot_len;
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: buflen=%"U16_F" len=%"SZT_F" off=%d sock->lastoffset=%"U16_F"\n",
        buflen, len, off, sock->lastoffset));
  
      buflen -= sock->lastoffset;
  
      if (len > buflen) {
        copylen = buflen;
      } else {
        copylen = (u16_t)len;
      }
  
      /* copy the contents of the received buffer into
      the supplied memory pointer mem */
      pbuf_copy_partial(p, (u8_t*)mem + off, copylen, sock->lastoffset);
  
      off += copylen;
  
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
        LWIP_ASSERT("invalid copylen, len would underflow", len >= copylen);
        len -= copylen;
        if ((len <= 0) ||
            (p->flags & PBUF_FLAG_PUSH) ||
            (sock->rcvevent <= 0) ||
            ((flags & MSG_PEEK) != 0)) {
          done = 1;
        }
      } else {
        done = 1;
      }
  
      /* Check to see from where the data was.*/
      if (done) {
  #if !SOCKETS_DEBUG
        if (from && fromlen)
  #endif /* !SOCKETS_DEBUG */
        {
          u16_t port;
          ip_addr_t tmpaddr;
          ip_addr_t *fromaddr;
          union sockaddr_aligned saddr;
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom(%d): addr=", s));
          if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
            fromaddr = &tmpaddr;
            netconn_getaddr(sock->conn, fromaddr, &port, 0);
          } else {
            port = netbuf_fromport((struct netbuf *)buf);
            fromaddr = netbuf_fromaddr((struct netbuf *)buf);
          }
  
  #if LWIP_IPV4 && LWIP_IPV6
          /* Dual-stack: Map IPv4 addresses to IPv4 mapped IPv6 */
          if (NETCONNTYPE_ISIPV6(netconn_type(sock->conn)) && IP_IS_V4(fromaddr)) {
            ip4_2_ipv4_mapped_ipv6(ip_2_ip6(fromaddr), ip_2_ip4(fromaddr));
            IP_SET_TYPE(fromaddr, IPADDR_TYPE_V6);
          }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
          IPADDR_PORT_TO_SOCKADDR(&saddr, fromaddr, port);
          ip_addr_debug_print(SOCKETS_DEBUG, fromaddr);
          LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F" len=%d\n", port, off));
  #if SOCKETS_DEBUG
          if (from && fromlen)
  #endif /* SOCKETS_DEBUG */
          {
            if (*fromlen > saddr.sa.sa_len) {
              *fromlen = saddr.sa.sa_len;
            }
            MEMCPY(from, &saddr, *fromlen);
          }
        }
      }
  
      /* If we don't peek the incoming message... */
      if ((flags & MSG_PEEK) == 0) {
        /* If this is a TCP socket, check if there is data left in the
           buffer. If so, it should be saved in the sock structure for next
           time around. */
        if ((NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) && (buflen - copylen > 0)) {
          sock->lastdata = buf;
          sock->lastoffset += copylen;
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: lastdata now netbuf=%p\n", buf));
        } else {
          sock->lastdata = NULL;
          sock->lastoffset = 0;
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_recvfrom: deleting netbuf=%p\n", buf));
          if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
            pbuf_free((struct pbuf *)buf);
          } else {
            netbuf_delete((struct netbuf *)buf);
          }
          buf = NULL;
        }
      }
    } while (!done);
  
    sock_set_errno(sock, 0);
    return off;
  }
  
  int
  lwip_read(int s, void *mem, size_t len)
  {
    return lwip_recvfrom(s, mem, len, 0, NULL, NULL);
  }
  
  int
  lwip_recv(int s, void *mem, size_t len, int flags)
  {
    return lwip_recvfrom(s, mem, len, flags, NULL, NULL);
  }
  
  int
  lwip_send(int s, const void *data, size_t size, int flags)
  {
    struct lwip_sock *sock;
    err_t err;
    u8_t write_flags;
    size_t written;
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_send(%d, data=%p, size=%"SZT_F", flags=0x%x)\n",
                                s, data, size, flags));
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
  #if (LWIP_UDP || LWIP_RAW)
      return lwip_sendto(s, data, size, flags, NULL, 0);
  #else /* (LWIP_UDP || LWIP_RAW) */
      sock_set_errno(sock, err_to_errno(ERR_ARG));
      return -1;
  #endif /* (LWIP_UDP || LWIP_RAW) */
    }
  
    write_flags = NETCONN_COPY |
      ((flags & MSG_MORE)     ? NETCONN_MORE      : 0) |
      ((flags & MSG_DONTWAIT) ? NETCONN_DONTBLOCK : 0);
    written = 0;
    err = netconn_write_partly(sock->conn, data, size, write_flags, &written);
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_send(%d) err=%d written=%"SZT_F"\n", s, err, written));
    sock_set_errno(sock, err_to_errno(err));
    return (err == ERR_OK ? (int)written : -1);
  }
  
  int
  lwip_sendmsg(int s, const struct msghdr *msg, int flags)
  {
    struct lwip_sock *sock;
    int i;
  #if LWIP_TCP
    u8_t write_flags;
    size_t written;
  #endif
    int size = 0;
    err_t err = ERR_OK;
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    LWIP_ERROR("lwip_sendmsg: invalid msghdr", msg != NULL,
               sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
  
    LWIP_UNUSED_ARG(msg->msg_control);
    LWIP_UNUSED_ARG(msg->msg_controllen);
    LWIP_UNUSED_ARG(msg->msg_flags);
    LWIP_ERROR("lwip_sendmsg: invalid msghdr iov", (msg->msg_iov != NULL && msg->msg_iovlen != 0),
               sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
  
    if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
  #if LWIP_TCP
      write_flags = NETCONN_COPY |
      ((flags & MSG_MORE)     ? NETCONN_MORE      : 0) |
      ((flags & MSG_DONTWAIT) ? NETCONN_DONTBLOCK : 0);
  
      for (i = 0; i < msg->msg_iovlen; i++) {
        u8_t apiflags = write_flags;
        if (i + 1 < msg->msg_iovlen) {
          apiflags |= NETCONN_MORE;
        }
        written = 0;
        err = netconn_write_partly(sock->conn, msg->msg_iov[i].iov_base, msg->msg_iov[i].iov_len, write_flags, &written);
        if (err == ERR_OK) {
          size += written;
          /* check that the entire IO vector was accepected, if not return a partial write */
          if (written != msg->msg_iov[i].iov_len)
            break;
        }
        /* none of this IO vector was accepted, but previous was, return partial write and conceal ERR_WOULDBLOCK */
        else if (err == ERR_WOULDBLOCK && size > 0) {
          err = ERR_OK;
          /* let ERR_WOULDBLOCK persist on the netconn since we are returning ERR_OK */
          break;
        } else {
          size = -1;
          break;
        }
      }
      sock_set_errno(sock, err_to_errno(err));
      return size;
  #else /* LWIP_TCP */
      sock_set_errno(sock, err_to_errno(ERR_ARG));
      return -1;
  #endif /* LWIP_TCP */
    }
    /* else, UDP and RAW NETCONNs */
  #if LWIP_UDP || LWIP_RAW
    {
      struct netbuf *chain_buf;
  
      LWIP_UNUSED_ARG(flags);
      LWIP_ERROR("lwip_sendmsg: invalid msghdr name", (((msg->msg_name == NULL) && (msg->msg_namelen == 0)) ||
                 IS_SOCK_ADDR_LEN_VALID(msg->msg_namelen)) ,
                 sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
  
      /* initialize chain buffer with destination */
      chain_buf = netbuf_new();
      if (!chain_buf) {
        sock_set_errno(sock, err_to_errno(ERR_MEM));
        return -1;
      }
      if (msg->msg_name) {
        u16_t remote_port;
        SOCKADDR_TO_IPADDR_PORT((const struct sockaddr *)msg->msg_name, &chain_buf->addr, remote_port);
        netbuf_fromport(chain_buf) = remote_port;
      }
  #if LWIP_NETIF_TX_SINGLE_PBUF
      for (i = 0; i < msg->msg_iovlen; i++) {
        size += msg->msg_iov[i].iov_len;
      }
      /* Allocate a new netbuf and copy the data into it. */
      if (netbuf_alloc(chain_buf, (u16_t)size) == NULL) {
         err = ERR_MEM;
      } else {
        /* flatten the IO vectors */
        size_t offset = 0;
        for (i = 0; i < msg->msg_iovlen; i++) {
          MEMCPY(&((u8_t*)chain_buf->p->payload)[offset], msg->msg_iov[i].iov_base, msg->msg_iov[i].iov_len);
          offset += msg->msg_iov[i].iov_len;
        }
  #if LWIP_CHECKSUM_ON_COPY
        {
          /* This can be improved by using LWIP_CHKSUM_COPY() and aggregating the checksum for each IO vector */
          u16_t chksum = ~inet_chksum_pbuf(chain_buf->p);
          netbuf_set_chksum(chain_buf, chksum);
        }
  #endif /* LWIP_CHECKSUM_ON_COPY */
        err = ERR_OK;
      }
  #else /* LWIP_NETIF_TX_SINGLE_PBUF */
      /* create a chained netbuf from the IO vectors. NOTE: we assemble a pbuf chain
         manually to avoid having to allocate, chain, and delete a netbuf for each iov */
      for (i = 0; i < msg->msg_iovlen; i++) {
        struct pbuf *p = pbuf_alloc(PBUF_TRANSPORT, 0, PBUF_REF);
        if (p == NULL) {
          err = ERR_MEM; /* let netbuf_delete() cleanup chain_buf */
          break;
        }
        p->payload = msg->msg_iov[i].iov_base;
        LWIP_ASSERT("iov_len < u16_t", msg->msg_iov[i].iov_len <= 0xFFFF);
        p->len = p->tot_len = (u16_t)msg->msg_iov[i].iov_len;
        /* netbuf empty, add new pbuf */
        if (chain_buf->p == NULL) {
          chain_buf->p = chain_buf->ptr = p;
          /* add pbuf to existing pbuf chain */
        } else {
          pbuf_cat(chain_buf->p, p);
        }
      }
      /* save size of total chain */
      if (err == ERR_OK) {
        size = netbuf_len(chain_buf);
      }
  #endif /* LWIP_NETIF_TX_SINGLE_PBUF */
  
      if (err == ERR_OK) {
  #if LWIP_IPV4 && LWIP_IPV6
        /* Dual-stack: Unmap IPv4 mapped IPv6 addresses */
        if (IP_IS_V6_VAL(chain_buf->addr) && ip6_addr_isipv4mappedipv6(ip_2_ip6(&chain_buf->addr))) {
          unmap_ipv4_mapped_ipv6(ip_2_ip4(&chain_buf->addr), ip_2_ip6(&chain_buf->addr));
          IP_SET_TYPE_VAL(chain_buf->addr, IPADDR_TYPE_V4);
        }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
        /* send the data */
        err = netconn_send(sock->conn, chain_buf);
      }
  
      /* deallocated the buffer */
      netbuf_delete(chain_buf);
  
      sock_set_errno(sock, err_to_errno(err));
      return (err == ERR_OK ? size : -1);
    }
  #else /* LWIP_UDP || LWIP_RAW */
    sock_set_errno(sock, err_to_errno(ERR_ARG));
    return -1;
  #endif /* LWIP_UDP || LWIP_RAW */
  }
  
  int
  lwip_sendto(int s, const void *data, size_t size, int flags,
         const struct sockaddr *to, socklen_t tolen)
  {
    struct lwip_sock *sock;
    err_t err;
    u16_t short_size;
    u16_t remote_port;
    struct netbuf buf;
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) == NETCONN_TCP) {
  #if LWIP_TCP
      return lwip_send(s, data, size, flags);
  #else /* LWIP_TCP */
      LWIP_UNUSED_ARG(flags);
      sock_set_errno(sock, err_to_errno(ERR_ARG));
      return -1;
  #endif /* LWIP_TCP */
    }
  
    /* @todo: split into multiple sendto's? */
    LWIP_ASSERT("lwip_sendto: size must fit in u16_t", size <= 0xffff);
    short_size = (u16_t)size;
    LWIP_ERROR("lwip_sendto: invalid address", (((to == NULL) && (tolen == 0)) ||
               (IS_SOCK_ADDR_LEN_VALID(tolen) &&
               IS_SOCK_ADDR_TYPE_VALID(to) && IS_SOCK_ADDR_ALIGNED(to))),
               sock_set_errno(sock, err_to_errno(ERR_ARG)); return -1;);
    LWIP_UNUSED_ARG(tolen);
  
    /* initialize a buffer */
    buf.p = buf.ptr = NULL;
  #if LWIP_CHECKSUM_ON_COPY
    buf.flags = 0;
  #endif /* LWIP_CHECKSUM_ON_COPY */
    if (to) {
      SOCKADDR_TO_IPADDR_PORT(to, &buf.addr, remote_port);
    } else {
      remote_port = 0;
      ip_addr_set_any(NETCONNTYPE_ISIPV6(netconn_type(sock->conn)), &buf.addr);
    }
    netbuf_fromport(&buf) = remote_port;
  
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_sendto(%d, data=%p, short_size=%"U16_F", flags=0x%x to=",
                s, data, short_size, flags));
    ip_addr_debug_print(SOCKETS_DEBUG, &buf.addr);
    LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F"\n", remote_port));
  
    /* make the buffer point to the data that should be sent */
  #if LWIP_NETIF_TX_SINGLE_PBUF
    /* Allocate a new netbuf and copy the data into it. */
    if (netbuf_alloc(&buf, short_size) == NULL) {
      err = ERR_MEM;
    } else {
  #if LWIP_CHECKSUM_ON_COPY
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_RAW) {
        u16_t chksum = LWIP_CHKSUM_COPY(buf.p->payload, data, short_size);
        netbuf_set_chksum(&buf, chksum);
      } else
  #endif /* LWIP_CHECKSUM_ON_COPY */
      {
        MEMCPY(buf.p->payload, data, short_size);
      }
      err = ERR_OK;
    }
  #else /* LWIP_NETIF_TX_SINGLE_PBUF */
    err = netbuf_ref(&buf, data, short_size);
  #endif /* LWIP_NETIF_TX_SINGLE_PBUF */
    if (err == ERR_OK) {
  #if LWIP_IPV4 && LWIP_IPV6
      /* Dual-stack: Unmap IPv4 mapped IPv6 addresses */
      if (IP_IS_V6_VAL(buf.addr) && ip6_addr_isipv4mappedipv6(ip_2_ip6(&buf.addr))) {
        unmap_ipv4_mapped_ipv6(ip_2_ip4(&buf.addr), ip_2_ip6(&buf.addr));
        IP_SET_TYPE_VAL(buf.addr, IPADDR_TYPE_V4);
      }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
      /* send the data */
      err = netconn_send(sock->conn, &buf);
    }
  
    /* deallocated the buffer */
    netbuf_free(&buf);
  
    sock_set_errno(sock, err_to_errno(err));
    return (err == ERR_OK ? short_size : -1);
  }
  
  int
  lwip_socket(int domain, int type, int protocol)
  {
    struct netconn *conn;
    int i;
  
    LWIP_UNUSED_ARG(domain); /* @todo: check this */
  
    /* create a netconn */
    switch (type) {
    case SOCK_RAW:
      conn = netconn_new_with_proto_and_callback(DOMAIN_TO_NETCONN_TYPE(domain, NETCONN_RAW),
                                                 (u8_t)protocol, event_callback);
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_socket(%s, SOCK_RAW, %d) = ",
                                   domain == PF_INET ? "PF_INET" : "UNKNOWN", protocol));
      break;
    case SOCK_DGRAM:
      conn = netconn_new_with_callback(DOMAIN_TO_NETCONN_TYPE(domain,
                   ((protocol == IPPROTO_UDPLITE) ? NETCONN_UDPLITE : NETCONN_UDP)) ,
                   event_callback);
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_socket(%s, SOCK_DGRAM, %d) = ",
                                   domain == PF_INET ? "PF_INET" : "UNKNOWN", protocol));
      break;
    case SOCK_STREAM:
      conn = netconn_new_with_callback(DOMAIN_TO_NETCONN_TYPE(domain, NETCONN_TCP), event_callback);
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_socket(%s, SOCK_STREAM, %d) = ",
                                   domain == PF_INET ? "PF_INET" : "UNKNOWN", protocol));
      break;
    default:
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_socket(%d, %d/UNKNOWN, %d) = -1\n",
                                   domain, type, protocol));
      set_errno(EINVAL);
      return -1;
    }
  
    if (!conn) {
      LWIP_DEBUGF(SOCKETS_DEBUG, ("-1 / ENOBUFS (could not create netconn)\n"));
      set_errno(ENOBUFS);
      return -1;
    }
  
    i = alloc_socket(conn, 0);
  
    if (i == -1) {
      netconn_delete(conn);
      set_errno(ENFILE);
      return -1;
    }
    conn->socket = i;
    LWIP_DEBUGF(SOCKETS_DEBUG, ("%d\n", i));
    set_errno(0);
    return i;
  }
  
  int
  lwip_write(int s, const void *data, size_t size)
  {
    return lwip_send(s, data, size, 0);
  }
  
  int
  lwip_writev(int s, const struct iovec *iov, int iovcnt)
  {
    struct msghdr msg;
  
    msg.msg_name = NULL;
    msg.msg_namelen = 0;
    /* Hack: we have to cast via number to cast from 'const' pointer to non-const.
       Blame the opengroup standard for this inconsistency. */
    msg.msg_iov = LWIP_CONST_CAST(struct iovec *, iov);
    msg.msg_iovlen = iovcnt;
    msg.msg_control = NULL;
    msg.msg_controllen = 0;
    msg.msg_flags = 0;
    return lwip_sendmsg(s, &msg, 0);
  }
  
  /**
   * Go through the readset and writeset lists and see which socket of the sockets
   * set in the sets has events. On return, readset, writeset and exceptset have
   * the sockets enabled that had events.
   *
   * @param maxfdp1 the highest socket index in the sets
   * @param readset_in    set of sockets to check for read events
   * @param writeset_in   set of sockets to check for write events
   * @param exceptset_in  set of sockets to check for error events
   * @param readset_out   set of sockets that had read events
   * @param writeset_out  set of sockets that had write events
   * @param exceptset_out set os sockets that had error events
   * @return number of sockets that had events (read/write/exception) (>= 0)
   */
  static int
  lwip_selscan(int maxfdp1, fd_set *readset_in, fd_set *writeset_in, fd_set *exceptset_in,
               fd_set *readset_out, fd_set *writeset_out, fd_set *exceptset_out)
  {
    int i, nready = 0;
    fd_set lreadset, lwriteset, lexceptset;
    struct lwip_sock *sock;
    SYS_ARCH_DECL_PROTECT(lev);
  
    FD_ZERO(&lreadset);
    FD_ZERO(&lwriteset);
    FD_ZERO(&lexceptset);
  
    /* Go through each socket in each list to count number of sockets which
       currently match */
    for (i = LWIP_SOCKET_OFFSET; i < maxfdp1; i++) {
      /* if this FD is not in the set, continue */
      if (!(readset_in && FD_ISSET(i, readset_in)) &&
          !(writeset_in && FD_ISSET(i, writeset_in)) &&
          !(exceptset_in && FD_ISSET(i, exceptset_in))) {
        continue;
      }
      /* First get the socket's status (protected)... */
      SYS_ARCH_PROTECT(lev);
      sock = tryget_socket(i);
      if (sock != NULL) {
        void* lastdata = sock->lastdata;
        s16_t rcvevent = sock->rcvevent;
        u16_t sendevent = sock->sendevent;
        u16_t errevent = sock->errevent;
        SYS_ARCH_UNPROTECT(lev);
  
        /* ... then examine it: */
        /* See if netconn of this socket is ready for read */
        if (readset_in && FD_ISSET(i, readset_in) && ((lastdata != NULL) || (rcvevent > 0))) {
          FD_SET(i, &lreadset);
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_selscan: fd=%d ready for reading\n", i));
          nready++;
        }
        /* See if netconn of this socket is ready for write */
        if (writeset_in && FD_ISSET(i, writeset_in) && (sendevent != 0)) {
          FD_SET(i, &lwriteset);
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_selscan: fd=%d ready for writing\n", i));
          nready++;
        }
        /* See if netconn of this socket had an error */
        if (exceptset_in && FD_ISSET(i, exceptset_in) && (errevent != 0)) {
          FD_SET(i, &lexceptset);
          LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_selscan: fd=%d ready for exception\n", i));
          nready++;
        }
      } else {
        SYS_ARCH_UNPROTECT(lev);
        /* continue on to next FD in list */
      }
    }
    /* copy local sets to the ones provided as arguments */
    *readset_out = lreadset;
    *writeset_out = lwriteset;
    *exceptset_out = lexceptset;
  
    LWIP_ASSERT("nready >= 0", nready >= 0);
    return nready;
  }
  
  int
  lwip_select(int maxfdp1, fd_set *readset, fd_set *writeset, fd_set *exceptset,
              struct timeval *timeout)
  {
    u32_t waitres = 0;
    int nready;
    fd_set lreadset, lwriteset, lexceptset;
    u32_t msectimeout;
    struct lwip_select_cb select_cb;
    int i;
    int maxfdp2;
  #if LWIP_NETCONN_SEM_PER_THREAD
    int waited = 0;
  #endif
    SYS_ARCH_DECL_PROTECT(lev);
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_select(%d, %p, %p, %p, tvsec=%"S32_F" tvusec=%"S32_F")\n",
                    maxfdp1, (void *)readset, (void *) writeset, (void *) exceptset,
                    timeout ? (s32_t)timeout->tv_sec : (s32_t)-1,
                    timeout ? (s32_t)timeout->tv_usec : (s32_t)-1));
  
    /* Go through each socket in each list to count number of sockets which
       currently match */
    nready = lwip_selscan(maxfdp1, readset, writeset, exceptset, &lreadset, &lwriteset, &lexceptset);
  
    /* If we don't have any current events, then suspend if we are supposed to */
    if (!nready) {
      if (timeout && timeout->tv_sec == 0 && timeout->tv_usec == 0) {
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_select: no timeout, returning 0\n"));
        /* This is OK as the local fdsets are empty and nready is zero,
           or we would have returned earlier. */
        goto return_copy_fdsets;
      }
  
      /* None ready: add our semaphore to list:
         We don't actually need any dynamic memory. Our entry on the
         list is only valid while we are in this function, so it's ok
         to use local variables. */
  
      select_cb.next = NULL;
      select_cb.prev = NULL;
      select_cb.readset = readset;
      select_cb.writeset = writeset;
      select_cb.exceptset = exceptset;
      select_cb.sem_signalled = 0;
  #if LWIP_NETCONN_SEM_PER_THREAD
      select_cb.sem = LWIP_NETCONN_THREAD_SEM_GET();
  #else /* LWIP_NETCONN_SEM_PER_THREAD */
      if (sys_sem_new(&select_cb.sem, 0) != ERR_OK) {
        /* failed to create semaphore */
        set_errno(ENOMEM);
        return -1;
      }
  #endif /* LWIP_NETCONN_SEM_PER_THREAD */
  
      /* Protect the select_cb_list */
      SYS_ARCH_PROTECT(lev);
  
      /* Put this select_cb on top of list */
      select_cb.next = select_cb_list;
      if (select_cb_list != NULL) {
        select_cb_list->prev = &select_cb;
      }
      select_cb_list = &select_cb;
      /* Increasing this counter tells event_callback that the list has changed. */
      select_cb_ctr++;
  
      /* Now we can safely unprotect */
      SYS_ARCH_UNPROTECT(lev);
  
      /* Increase select_waiting for each socket we are interested in */
      maxfdp2 = maxfdp1;
      for (i = LWIP_SOCKET_OFFSET; i < maxfdp1; i++) {
        if ((readset && FD_ISSET(i, readset)) ||
            (writeset && FD_ISSET(i, writeset)) ||
            (exceptset && FD_ISSET(i, exceptset))) {
          struct lwip_sock *sock;
          SYS_ARCH_PROTECT(lev);
          sock = tryget_socket(i);
          if (sock != NULL) {
            sock->select_waiting++;
            LWIP_ASSERT("sock->select_waiting > 0", sock->select_waiting > 0);
          } else {
            /* Not a valid socket */
            nready = -1;
            maxfdp2 = i;
            SYS_ARCH_UNPROTECT(lev);
            break;
          }
          SYS_ARCH_UNPROTECT(lev);
        }
      }
  
      if (nready >= 0) {
        /* Call lwip_selscan again: there could have been events between
           the last scan (without us on the list) and putting us on the list! */
        nready = lwip_selscan(maxfdp1, readset, writeset, exceptset, &lreadset, &lwriteset, &lexceptset);
        if (!nready) {
          /* Still none ready, just wait to be woken */
          if (timeout == 0) {
            /* Wait forever */
            msectimeout = 0;
          } else {
            msectimeout =  ((timeout->tv_sec * 1000) + ((timeout->tv_usec + 500)/1000));
            if (msectimeout == 0) {
              /* Wait 1ms at least (0 means wait forever) */
              msectimeout = 1;
            }
          }
  
          waitres = sys_arch_sem_wait(SELECT_SEM_PTR(select_cb.sem), msectimeout);
  #if LWIP_NETCONN_SEM_PER_THREAD
          waited = 1;
  #endif
        }
      }
  
      /* Decrease select_waiting for each socket we are interested in */
      for (i = LWIP_SOCKET_OFFSET; i < maxfdp2; i++) {
        if ((readset && FD_ISSET(i, readset)) ||
            (writeset && FD_ISSET(i, writeset)) ||
            (exceptset && FD_ISSET(i, exceptset))) {
          struct lwip_sock *sock;
          SYS_ARCH_PROTECT(lev);
          sock = tryget_socket(i);
          if (sock != NULL) {
            /* for now, handle select_waiting==0... */
            LWIP_ASSERT("sock->select_waiting > 0", sock->select_waiting > 0);
            if (sock->select_waiting > 0) {
              sock->select_waiting--;
            }
          } else {
            /* Not a valid socket */
            nready = -1;
          }
          SYS_ARCH_UNPROTECT(lev);
        }
      }
      /* Take us off the list */
      SYS_ARCH_PROTECT(lev);
      if (select_cb.next != NULL) {
        select_cb.next->prev = select_cb.prev;
      }
      if (select_cb_list == &select_cb) {
        LWIP_ASSERT("select_cb.prev == NULL", select_cb.prev == NULL);
        select_cb_list = select_cb.next;
      } else {
        LWIP_ASSERT("select_cb.prev != NULL", select_cb.prev != NULL);
        select_cb.prev->next = select_cb.next;
      }
      /* Increasing this counter tells event_callback that the list has changed. */
      select_cb_ctr++;
      SYS_ARCH_UNPROTECT(lev);
  
  #if LWIP_NETCONN_SEM_PER_THREAD
      if (select_cb.sem_signalled && (!waited || (waitres == SYS_ARCH_TIMEOUT))) {
        /* don't leave the thread-local semaphore signalled */
        sys_arch_sem_wait(select_cb.sem, 1);
      }
  #else /* LWIP_NETCONN_SEM_PER_THREAD */
      sys_sem_free(&select_cb.sem);
  #endif /* LWIP_NETCONN_SEM_PER_THREAD */
  
      if (nready < 0) {
        /* This happens when a socket got closed while waiting */
        set_errno(EBADF);
        return -1;
      }
  
      if (waitres == SYS_ARCH_TIMEOUT) {
        /* Timeout */
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_select: timeout expired\n"));
        /* This is OK as the local fdsets are empty and nready is zero,
           or we would have returned earlier. */
        goto return_copy_fdsets;
      }
  
      /* See what's set */
      nready = lwip_selscan(maxfdp1, readset, writeset, exceptset, &lreadset, &lwriteset, &lexceptset);
    }
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_select: nready=%d\n", nready));
  return_copy_fdsets:
    set_errno(0);
    if (readset) {
      *readset = lreadset;
    }
    if (writeset) {
      *writeset = lwriteset;
    }
    if (exceptset) {
      *exceptset = lexceptset;
    }
    return nready;
  }
  
  /**
   * Callback registered in the netconn layer for each socket-netconn.
   * Processes recvevent (data available) and wakes up tasks waiting for select.
   */
  static void
  event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len)
  {
    int s;
    struct lwip_sock *sock;
    struct lwip_select_cb *scb;
    int last_select_cb_ctr;
    SYS_ARCH_DECL_PROTECT(lev);
  
    LWIP_UNUSED_ARG(len);
  
    /* Get socket */
    if (conn) {
      s = conn->socket;
      if (s < 0) {
        /* Data comes in right away after an accept, even though
         * the server task might not have created a new socket yet.
         * Just count down (or up) if that's the case and we
         * will use the data later. Note that only receive events
         * can happen before the new socket is set up. */
        SYS_ARCH_PROTECT(lev);
        if (conn->socket < 0) {
          if (evt == NETCONN_EVT_RCVPLUS) {
            conn->socket--;
          }
          SYS_ARCH_UNPROTECT(lev);
          return;
        }
        s = conn->socket;
        SYS_ARCH_UNPROTECT(lev);
      }
  
      sock = get_socket(s);
      if (!sock) {
        return;
      }
    } else {
      return;
    }
  
    SYS_ARCH_PROTECT(lev);
    /* Set event as required */
    switch (evt) {
      case NETCONN_EVT_RCVPLUS:
        sock->rcvevent++;
        break;
      case NETCONN_EVT_RCVMINUS:
        sock->rcvevent--;
        break;
      case NETCONN_EVT_SENDPLUS:
        sock->sendevent = 1;
        break;
      case NETCONN_EVT_SENDMINUS:
        sock->sendevent = 0;
        break;
      case NETCONN_EVT_ERROR:
        sock->errevent = 1;
        break;
      default:
        LWIP_ASSERT("unknown event", 0);
        break;
    }
  
    if (sock->select_waiting == 0) {
      /* noone is waiting for this socket, no need to check select_cb_list */
      SYS_ARCH_UNPROTECT(lev);
      return;
    }
  
    /* Now decide if anyone is waiting for this socket */
    /* NOTE: This code goes through the select_cb_list list multiple times
       ONLY IF a select was actually waiting. We go through the list the number
       of waiting select calls + 1. This list is expected to be small. */
  
    /* At this point, SYS_ARCH is still protected! */
  again:
    for (scb = select_cb_list; scb != NULL; scb = scb->next) {
      /* remember the state of select_cb_list to detect changes */
      last_select_cb_ctr = select_cb_ctr;
      if (scb->sem_signalled == 0) {
        /* semaphore not signalled yet */
        int do_signal = 0;
        /* Test this select call for our socket */
        if (sock->rcvevent > 0) {
          if (scb->readset && FD_ISSET(s, scb->readset)) {
            do_signal = 1;
          }
        }
        if (sock->sendevent != 0) {
          if (!do_signal && scb->writeset && FD_ISSET(s, scb->writeset)) {
            do_signal = 1;
          }
        }
        if (sock->errevent != 0) {
          if (!do_signal && scb->exceptset && FD_ISSET(s, scb->exceptset)) {
            do_signal = 1;
          }
        }
        if (do_signal) {
          scb->sem_signalled = 1;
          /* Don't call SYS_ARCH_UNPROTECT() before signaling the semaphore, as this might
             lead to the select thread taking itself off the list, invalidating the semaphore. */
          sys_sem_signal(SELECT_SEM_PTR(scb->sem));
        }
      }
      /* unlock interrupts with each step */
      SYS_ARCH_UNPROTECT(lev);
      /* this makes sure interrupt protection time is short */
      SYS_ARCH_PROTECT(lev);
      if (last_select_cb_ctr != select_cb_ctr) {
        /* someone has changed select_cb_list, restart at the beginning */
        goto again;
      }
    }
    SYS_ARCH_UNPROTECT(lev);
  }
  
  /**
   * Close one end of a full-duplex connection.
   */
  int
  lwip_shutdown(int s, int how)
  {
    struct lwip_sock *sock;
    err_t err;
    u8_t shut_rx = 0, shut_tx = 0;
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_shutdown(%d, how=%d)\n", s, how));
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    if (sock->conn != NULL) {
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
        sock_set_errno(sock, EOPNOTSUPP);
        return -1;
      }
    } else {
      sock_set_errno(sock, ENOTCONN);
      return -1;
    }
  
    if (how == SHUT_RD) {
      shut_rx = 1;
    } else if (how == SHUT_WR) {
      shut_tx = 1;
    } else if (how == SHUT_RDWR) {
      shut_rx = 1;
      shut_tx = 1;
    } else {
      sock_set_errno(sock, EINVAL);
      return -1;
    }
    err = netconn_shutdown(sock->conn, shut_rx, shut_tx);
  
    sock_set_errno(sock, err_to_errno(err));
    return (err == ERR_OK ? 0 : -1);
  }
  
  static int
  lwip_getaddrname(int s, struct sockaddr *name, socklen_t *namelen, u8_t local)
  {
    struct lwip_sock *sock;
    union sockaddr_aligned saddr;
    ip_addr_t naddr;
    u16_t port;
    err_t err;
  
    sock = get_socket(s);
    if (!sock) {
      return -1;
    }
  
    /* get the IP address and port */
    err = netconn_getaddr(sock->conn, &naddr, &port, local);
    if (err != ERR_OK) {
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
  
  #if LWIP_IPV4 && LWIP_IPV6
    /* Dual-stack: Map IPv4 addresses to IPv4 mapped IPv6 */
    if (NETCONNTYPE_ISIPV6(netconn_type(sock->conn)) &&
        IP_IS_V4_VAL(naddr)) {
      ip4_2_ipv4_mapped_ipv6(ip_2_ip6(&naddr), ip_2_ip4(&naddr));
      IP_SET_TYPE_VAL(naddr, IPADDR_TYPE_V6);
    }
  #endif /* LWIP_IPV4 && LWIP_IPV6 */
  
    IPADDR_PORT_TO_SOCKADDR(&saddr, &naddr, port);
  
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getaddrname(%d, addr=", s));
    ip_addr_debug_print_val(SOCKETS_DEBUG, naddr);
    LWIP_DEBUGF(SOCKETS_DEBUG, (" port=%"U16_F")\n", port));
  
    if (*namelen > saddr.sa.sa_len) {
      *namelen = saddr.sa.sa_len;
    }
    MEMCPY(name, &saddr, *namelen);
  
    sock_set_errno(sock, 0);
    return 0;
  }
  
  int
  lwip_getpeername(int s, struct sockaddr *name, socklen_t *namelen)
  {
    return lwip_getaddrname(s, name, namelen, 0);
  }
  
  int
  lwip_getsockname(int s, struct sockaddr *name, socklen_t *namelen)
  {
    return lwip_getaddrname(s, name, namelen, 1);
  }
  
  int
  lwip_getsockopt(int s, int level, int optname, void *optval, socklen_t *optlen)
  {
    u8_t err;
    struct lwip_sock *sock = get_socket(s);
  #if !LWIP_TCPIP_CORE_LOCKING
    LWIP_SETGETSOCKOPT_DATA_VAR_DECLARE(data);
  #endif /* !LWIP_TCPIP_CORE_LOCKING */
  
    if (!sock) {
      return -1;
    }
  
    if ((NULL == optval) || (NULL == optlen)) {
      sock_set_errno(sock, EFAULT);
      return -1;
    }
  
  #if LWIP_TCPIP_CORE_LOCKING
    /* core-locking can just call the -impl function */
    LOCK_TCPIP_CORE();
    err = lwip_getsockopt_impl(s, level, optname, optval, optlen);
    UNLOCK_TCPIP_CORE();
  
  #else /* LWIP_TCPIP_CORE_LOCKING */
  
  #if LWIP_MPU_COMPATIBLE
    /* MPU_COMPATIBLE copies the optval data, so check for max size here */
    if (*optlen > LWIP_SETGETSOCKOPT_MAXOPTLEN) {
      sock_set_errno(sock, ENOBUFS);
      return -1;
    }
  #endif /* LWIP_MPU_COMPATIBLE */
  
    LWIP_SETGETSOCKOPT_DATA_VAR_ALLOC(data, sock);
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).s = s;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).level = level;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optname = optname;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optlen = *optlen;
  #if !LWIP_MPU_COMPATIBLE
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optval.p = optval;
  #endif /* !LWIP_MPU_COMPATIBLE */
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).err = 0;
  #if LWIP_NETCONN_SEM_PER_THREAD
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem = LWIP_NETCONN_THREAD_SEM_GET();
  #else
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem = &sock->conn->op_completed;
  #endif
    err = tcpip_callback(lwip_getsockopt_callback, &LWIP_SETGETSOCKOPT_DATA_VAR_REF(data));
    if (err != ERR_OK) {
      LWIP_SETGETSOCKOPT_DATA_VAR_FREE(data);
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
    sys_arch_sem_wait((sys_sem_t*)(LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem), 0);
  
    /* write back optlen and optval */
    *optlen = LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optlen;
  #if LWIP_MPU_COMPATIBLE
    MEMCPY(optval, LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optval,
      LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optlen);
  #endif /* LWIP_MPU_COMPATIBLE */
  
    /* maybe lwip_getsockopt_internal has changed err */
    err = LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).err;
    LWIP_SETGETSOCKOPT_DATA_VAR_FREE(data);
  #endif /* LWIP_TCPIP_CORE_LOCKING */
  
    sock_set_errno(sock, err);
    return err ? -1 : 0;
  }
  
  #if !LWIP_TCPIP_CORE_LOCKING
  /** lwip_getsockopt_callback: only used without CORE_LOCKING
   * to get into the tcpip_thread
   */
  static void
  lwip_getsockopt_callback(void *arg)
  {
    struct lwip_setgetsockopt_data *data;
    LWIP_ASSERT("arg != NULL", arg != NULL);
    data = (struct lwip_setgetsockopt_data*)arg;
  
    data->err = lwip_getsockopt_impl(data->s, data->level, data->optname,
  #if LWIP_MPU_COMPATIBLE
      data->optval,
  #else /* LWIP_MPU_COMPATIBLE */
      data->optval.p,
  #endif /* LWIP_MPU_COMPATIBLE */
      &data->optlen);
  
    sys_sem_signal((sys_sem_t*)(data->completed_sem));
  }
  #endif  /* LWIP_TCPIP_CORE_LOCKING */
  
  /** lwip_getsockopt_impl: the actual implementation of getsockopt:
   * same argument as lwip_getsockopt, either called directly or through callback
   */
  static u8_t
  lwip_getsockopt_impl(int s, int level, int optname, void *optval, socklen_t *optlen)
  {
    u8_t err = 0;
    struct lwip_sock *sock = tryget_socket(s);
    if (!sock) {
      return EBADF;
    }
  
    switch (level) {
  
  /* Level: SOL_SOCKET */
    case SOL_SOCKET:
      switch (optname) {
  
  #if LWIP_TCP
      case SO_ACCEPTCONN:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, int);
        if (NETCONNTYPE_GROUP(sock->conn->type) != NETCONN_TCP) {
          return ENOPROTOOPT;
        }
        if ((sock->conn->pcb.tcp != NULL) && (sock->conn->pcb.tcp->state == LISTEN)) {
          *(int*)optval = 1;
        } else {
          *(int*)optval = 0;
        }
        break;
  #endif /* LWIP_TCP */
  
      /* The option flags */
      case SO_BROADCAST:
      case SO_KEEPALIVE:
  #if SO_REUSE
      case SO_REUSEADDR:
  #endif /* SO_REUSE */
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, int);
        *(int*)optval = ip_get_option(sock->conn->pcb.ip, optname);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, SOL_SOCKET, optname=0x%x, ..) = %s\n",
                                    s, optname, (*(int*)optval?"on":"off")));
        break;
  
      case SO_TYPE:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, int);
        switch (NETCONNTYPE_GROUP(netconn_type(sock->conn))) {
        case NETCONN_RAW:
          *(int*)optval = SOCK_RAW;
          break;
        case NETCONN_TCP:
          *(int*)optval = SOCK_STREAM;
          break;
        case NETCONN_UDP:
          *(int*)optval = SOCK_DGRAM;
          break;
        default: /* unrecognized socket type */
          *(int*)optval = netconn_type(sock->conn);
          LWIP_DEBUGF(SOCKETS_DEBUG,
                      ("lwip_getsockopt(%d, SOL_SOCKET, SO_TYPE): unrecognized socket type %d\n",
                      s, *(int *)optval));
        }  /* switch (netconn_type(sock->conn)) */
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, SOL_SOCKET, SO_TYPE) = %d\n",
                    s, *(int *)optval));
        break;
  
      case SO_ERROR:
        LWIP_SOCKOPT_CHECK_OPTLEN(*optlen, int);
        /* only overwrite ERR_OK or temporary errors */
        if (((sock->err == 0) || (sock->err == EINPROGRESS)) && (sock->conn != NULL)) {
          sock_set_errno(sock, err_to_errno(sock->conn->last_err));
        }
        *(int *)optval = (sock->err == 0xFF ? (int)-1 : (int)sock->err);
        sock->err = 0;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, SOL_SOCKET, SO_ERROR) = %d\n",
                    s, *(int *)optval));
        break;
  
  #if LWIP_SO_SNDTIMEO
      case SO_SNDTIMEO:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, LWIP_SO_SNDRCVTIMEO_OPTTYPE);
        LWIP_SO_SNDRCVTIMEO_SET(optval, netconn_get_sendtimeout(sock->conn));
        break;
  #endif /* LWIP_SO_SNDTIMEO */
  #if LWIP_SO_RCVTIMEO
      case SO_RCVTIMEO:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, LWIP_SO_SNDRCVTIMEO_OPTTYPE);
        LWIP_SO_SNDRCVTIMEO_SET(optval, netconn_get_recvtimeout(sock->conn));
        break;
  #endif /* LWIP_SO_RCVTIMEO */
  #if LWIP_SO_RCVBUF
      case SO_RCVBUF:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, int);
        *(int *)optval = netconn_get_recvbufsize(sock->conn);
        break;
  #endif /* LWIP_SO_RCVBUF */
  #if LWIP_SO_LINGER
      case SO_LINGER:
        {
          s16_t conn_linger;
          struct linger* linger = (struct linger*)optval;
          LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, struct linger);
          conn_linger = sock->conn->linger;
          if (conn_linger >= 0) {
            linger->l_onoff = 1;
            linger->l_linger = (int)conn_linger;
          } else {
            linger->l_onoff = 0;
            linger->l_linger = 0;
          }
        }
        break;
  #endif /* LWIP_SO_LINGER */
  #if LWIP_UDP
      case SO_NO_CHECK:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, *optlen, int, NETCONN_UDP);
  #if LWIP_UDPLITE
        if ((udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_UDPLITE) != 0) {
          /* this flag is only available for UDP, not for UDP lite */
          return EAFNOSUPPORT;
        }
  #endif /* LWIP_UDPLITE */
        *(int*)optval = (udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_NOCHKSUM) ? 1 : 0;
        break;
  #endif /* LWIP_UDP*/
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, SOL_SOCKET, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  
  /* Level: IPPROTO_IP */
    case IPPROTO_IP:
      switch (optname) {
      case IP_TTL:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, int);
        *(int*)optval = sock->conn->pcb.ip->ttl;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, IP_TTL) = %d\n",
                    s, *(int *)optval));
        break;
      case IP_TOS:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, int);
        *(int*)optval = sock->conn->pcb.ip->tos;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, IP_TOS) = %d\n",
                    s, *(int *)optval));
        break;
  #if LWIP_MULTICAST_TX_OPTIONS
      case IP_MULTICAST_TTL:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, u8_t);
        if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_UDP) {
          return ENOPROTOOPT;
        }
        *(u8_t*)optval = udp_get_multicast_ttl(sock->conn->pcb.udp);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, IP_MULTICAST_TTL) = %d\n",
                    s, *(int *)optval));
        break;
      case IP_MULTICAST_IF:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, struct in_addr);
        if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_UDP) {
          return ENOPROTOOPT;
        }
        inet_addr_from_ip4addr((struct in_addr*)optval, udp_get_multicast_netif_addr(sock->conn->pcb.udp));
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, IP_MULTICAST_IF) = 0x%"X32_F"\n",
                    s, *(u32_t *)optval));
        break;
      case IP_MULTICAST_LOOP:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, u8_t);
        if ((sock->conn->pcb.udp->flags & UDP_FLAGS_MULTICAST_LOOP) != 0) {
          *(u8_t*)optval = 1;
        } else {
          *(u8_t*)optval = 0;
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, IP_MULTICAST_LOOP) = %d\n",
                    s, *(int *)optval));
        break;
  #endif /* LWIP_MULTICAST_TX_OPTIONS */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IP, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  
  #if LWIP_TCP
  /* Level: IPPROTO_TCP */
    case IPPROTO_TCP:
      /* Special case: all IPPROTO_TCP option take an int */
      LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, *optlen, int, NETCONN_TCP);
      if (sock->conn->pcb.tcp->state == LISTEN) {
        return EINVAL;
      }
      switch (optname) {
      case TCP_NODELAY:
        *(int*)optval = tcp_nagle_disabled(sock->conn->pcb.tcp);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_NODELAY) = %s\n",
                    s, (*(int*)optval)?"on":"off") );
        break;
      case TCP_KEEPALIVE:
        *(int*)optval = (int)sock->conn->pcb.tcp->keep_idle;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_KEEPALIVE) = %d\n",
                    s, *(int *)optval));
        break;
  
  #if LWIP_TCP_KEEPALIVE
      case TCP_KEEPIDLE:
        *(int*)optval = (int)(sock->conn->pcb.tcp->keep_idle/1000);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_KEEPIDLE) = %d\n",
                    s, *(int *)optval));
        break;
      case TCP_KEEPINTVL:
        *(int*)optval = (int)(sock->conn->pcb.tcp->keep_intvl/1000);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_KEEPINTVL) = %d\n",
                    s, *(int *)optval));
        break;
      case TCP_KEEPCNT:
        *(int*)optval = (int)sock->conn->pcb.tcp->keep_cnt;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, TCP_KEEPCNT) = %d\n",
                    s, *(int *)optval));
        break;
  #endif /* LWIP_TCP_KEEPALIVE */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_TCP, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_TCP */
  
  #if LWIP_IPV6
  /* Level: IPPROTO_IPV6 */
    case IPPROTO_IPV6:
      switch (optname) {
      case IPV6_V6ONLY:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, *optlen, int);
        *(int*)optval = (netconn_get_ipv6only(sock->conn) ? 1 : 0);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IPV6, IPV6_V6ONLY) = %d\n",
                    s, *(int *)optval));
        break;
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_IPV6, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_IPV6 */
  
  #if LWIP_UDP && LWIP_UDPLITE
    /* Level: IPPROTO_UDPLITE */
    case IPPROTO_UDPLITE:
      /* Special case: all IPPROTO_UDPLITE option take an int */
      LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, *optlen, int);
      /* If this is no UDP lite socket, ignore any options. */
      if (!NETCONNTYPE_ISUDPLITE(netconn_type(sock->conn))) {
        return ENOPROTOOPT;
      }
      switch (optname) {
      case UDPLITE_SEND_CSCOV:
        *(int*)optval = sock->conn->pcb.udp->chksum_len_tx;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV) = %d\n",
                    s, (*(int*)optval)) );
        break;
      case UDPLITE_RECV_CSCOV:
        *(int*)optval = sock->conn->pcb.udp->chksum_len_rx;
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV) = %d\n",
                    s, (*(int*)optval)) );
        break;
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_UDPLITE, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_UDP */
    /* Level: IPPROTO_RAW */
    case IPPROTO_RAW:
      switch (optname) {
  #if LWIP_IPV6 && LWIP_RAW
      case IPV6_CHECKSUM:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, *optlen, int, NETCONN_RAW);
        if (sock->conn->pcb.raw->chksum_reqd == 0) {
          *(int *)optval = -1;
        } else {
          *(int *)optval = sock->conn->pcb.raw->chksum_offset;
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_RAW, IPV6_CHECKSUM) = %d\n",
                    s, (*(int*)optval)) );
        break;
  #endif /* LWIP_IPV6 && LWIP_RAW */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, IPPROTO_RAW, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
    default:
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_getsockopt(%d, level=0x%x, UNIMPL: optname=0x%x, ..)\n",
                                  s, level, optname));
      err = ENOPROTOOPT;
      break;
    } /* switch (level) */
  
    return err;
  }
  
  int
  lwip_setsockopt(int s, int level, int optname, const void *optval, socklen_t optlen)
  {
    u8_t err = 0;
    struct lwip_sock *sock = get_socket(s);
  #if !LWIP_TCPIP_CORE_LOCKING
    LWIP_SETGETSOCKOPT_DATA_VAR_DECLARE(data);
  #endif /* !LWIP_TCPIP_CORE_LOCKING */
  
    if (!sock) {
      return -1;
    }
  
    if (NULL == optval) {
      sock_set_errno(sock, EFAULT);
      return -1;
    }
  
  #if LWIP_TCPIP_CORE_LOCKING
    /* core-locking can just call the -impl function */
    LOCK_TCPIP_CORE();
    err = lwip_setsockopt_impl(s, level, optname, optval, optlen);
    UNLOCK_TCPIP_CORE();
  
  #else /* LWIP_TCPIP_CORE_LOCKING */
  
  #if LWIP_MPU_COMPATIBLE
    /* MPU_COMPATIBLE copies the optval data, so check for max size here */
    if (optlen > LWIP_SETGETSOCKOPT_MAXOPTLEN) {
      sock_set_errno(sock, ENOBUFS);
      return -1;
    }
  #endif /* LWIP_MPU_COMPATIBLE */
  
    LWIP_SETGETSOCKOPT_DATA_VAR_ALLOC(data, sock);
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).s = s;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).level = level;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optname = optname;
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optlen = optlen;
  #if LWIP_MPU_COMPATIBLE
    MEMCPY(LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optval, optval, optlen);
  #else /* LWIP_MPU_COMPATIBLE */
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).optval.pc = (const void*)optval;
  #endif /* LWIP_MPU_COMPATIBLE */
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).err = 0;
  #if LWIP_NETCONN_SEM_PER_THREAD
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem = LWIP_NETCONN_THREAD_SEM_GET();
  #else
    LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem = &sock->conn->op_completed;
  #endif
    err = tcpip_callback(lwip_setsockopt_callback, &LWIP_SETGETSOCKOPT_DATA_VAR_REF(data));
    if (err != ERR_OK) {
      LWIP_SETGETSOCKOPT_DATA_VAR_FREE(data);
      sock_set_errno(sock, err_to_errno(err));
      return -1;
    }
    sys_arch_sem_wait((sys_sem_t*)(LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).completed_sem), 0);
  
    /* maybe lwip_getsockopt_internal has changed err */
    err = LWIP_SETGETSOCKOPT_DATA_VAR_REF(data).err;
    LWIP_SETGETSOCKOPT_DATA_VAR_FREE(data);
  #endif  /* LWIP_TCPIP_CORE_LOCKING */
  
    sock_set_errno(sock, err);
    return err ? -1 : 0;
  }
  
  #if !LWIP_TCPIP_CORE_LOCKING
  /** lwip_setsockopt_callback: only used without CORE_LOCKING
   * to get into the tcpip_thread
   */
  static void
  lwip_setsockopt_callback(void *arg)
  {
    struct lwip_setgetsockopt_data *data;
    LWIP_ASSERT("arg != NULL", arg != NULL);
    data = (struct lwip_setgetsockopt_data*)arg;
  
    data->err = lwip_setsockopt_impl(data->s, data->level, data->optname,
  #if LWIP_MPU_COMPATIBLE
      data->optval,
  #else /* LWIP_MPU_COMPATIBLE */
      data->optval.pc,
  #endif /* LWIP_MPU_COMPATIBLE */
      data->optlen);
  
    sys_sem_signal((sys_sem_t*)(data->completed_sem));
  }
  #endif  /* LWIP_TCPIP_CORE_LOCKING */
  
  /** lwip_setsockopt_impl: the actual implementation of setsockopt:
   * same argument as lwip_setsockopt, either called directly or through callback
   */
  static u8_t
  lwip_setsockopt_impl(int s, int level, int optname, const void *optval, socklen_t optlen)
  {
    u8_t err = 0;
    struct lwip_sock *sock = tryget_socket(s);
    if (!sock) {
      return EBADF;
    }
  
    switch (level) {
  
  /* Level: SOL_SOCKET */
    case SOL_SOCKET:
      switch (optname) {
  
      /* SO_ACCEPTCONN is get-only */
  
      /* The option flags */
      case SO_BROADCAST:
      case SO_KEEPALIVE:
  #if SO_REUSE
      case SO_REUSEADDR:
  #endif /* SO_REUSE */
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, int);
        if (*(const int*)optval) {
          ip_set_option(sock->conn->pcb.ip, optname);
        } else {
          ip_reset_option(sock->conn->pcb.ip, optname);
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, SOL_SOCKET, optname=0x%x, ..) -> %s\n",
                    s, optname, (*(const int*)optval?"on":"off")));
        break;
  
      /* SO_TYPE is get-only */
      /* SO_ERROR is get-only */
  
  #if LWIP_SO_SNDTIMEO
      case SO_SNDTIMEO:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, optlen, LWIP_SO_SNDRCVTIMEO_OPTTYPE);
        netconn_set_sendtimeout(sock->conn, LWIP_SO_SNDRCVTIMEO_GET_MS(optval));
        break;
  #endif /* LWIP_SO_SNDTIMEO */
  #if LWIP_SO_RCVTIMEO
      case SO_RCVTIMEO:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, optlen, LWIP_SO_SNDRCVTIMEO_OPTTYPE);
        netconn_set_recvtimeout(sock->conn, (int)LWIP_SO_SNDRCVTIMEO_GET_MS(optval));
        break;
  #endif /* LWIP_SO_RCVTIMEO */
  #if LWIP_SO_RCVBUF
      case SO_RCVBUF:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, optlen, int);
        netconn_set_recvbufsize(sock->conn, *(const int*)optval);
        break;
  #endif /* LWIP_SO_RCVBUF */
  #if LWIP_SO_LINGER
      case SO_LINGER:
        {
          const struct linger* linger = (const struct linger*)optval;
          LWIP_SOCKOPT_CHECK_OPTLEN_CONN(sock, optlen, struct linger);
          if (linger->l_onoff) {
            int lingersec = linger->l_linger;
            if (lingersec < 0) {
              return EINVAL;
            }
            if (lingersec > 0xFFFF) {
              lingersec = 0xFFFF;
            }
            sock->conn->linger = (s16_t)lingersec;
          } else {
            sock->conn->linger = -1;
          }
        }
        break;
  #endif /* LWIP_SO_LINGER */
  #if LWIP_UDP
      case SO_NO_CHECK:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, int, NETCONN_UDP);
  #if LWIP_UDPLITE
        if ((udp_flags(sock->conn->pcb.udp) & UDP_FLAGS_UDPLITE) != 0) {
          /* this flag is only available for UDP, not for UDP lite */
          return EAFNOSUPPORT;
        }
  #endif /* LWIP_UDPLITE */
        if (*(const int*)optval) {
          udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) | UDP_FLAGS_NOCHKSUM);
        } else {
          udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) & ~UDP_FLAGS_NOCHKSUM);
        }
        break;
  #endif /* LWIP_UDP */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, SOL_SOCKET, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  
  /* Level: IPPROTO_IP */
    case IPPROTO_IP:
      switch (optname) {
      case IP_TTL:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, int);
        sock->conn->pcb.ip->ttl = (u8_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_IP, IP_TTL, ..) -> %d\n",
                    s, sock->conn->pcb.ip->ttl));
        break;
      case IP_TOS:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, int);
        sock->conn->pcb.ip->tos = (u8_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_IP, IP_TOS, ..)-> %d\n",
                    s, sock->conn->pcb.ip->tos));
        break;
  #if LWIP_MULTICAST_TX_OPTIONS
      case IP_MULTICAST_TTL:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, u8_t, NETCONN_UDP);
        udp_set_multicast_ttl(sock->conn->pcb.udp, (u8_t)(*(const u8_t*)optval));
        break;
      case IP_MULTICAST_IF:
        {
          ip4_addr_t if_addr;
          LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, struct in_addr, NETCONN_UDP);
          inet_addr_to_ip4addr(&if_addr, (const struct in_addr*)optval);
          udp_set_multicast_netif_addr(sock->conn->pcb.udp, &if_addr);
        }
        break;
      case IP_MULTICAST_LOOP:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, u8_t, NETCONN_UDP);
        if (*(const u8_t*)optval) {
          udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) | UDP_FLAGS_MULTICAST_LOOP);
        } else {
          udp_setflags(sock->conn->pcb.udp, udp_flags(sock->conn->pcb.udp) & ~UDP_FLAGS_MULTICAST_LOOP);
        }
        break;
  #endif /* LWIP_MULTICAST_TX_OPTIONS */
  #if LWIP_IGMP
      case IP_ADD_MEMBERSHIP:
      case IP_DROP_MEMBERSHIP:
        {
          /* If this is a TCP or a RAW socket, ignore these options. */
          /* @todo: assign membership to this socket so that it is dropped when closing the socket */
          err_t igmp_err;
          const struct ip_mreq *imr = (const struct ip_mreq *)optval;
          ip4_addr_t if_addr;
          ip4_addr_t multi_addr;
          LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, struct ip_mreq, NETCONN_UDP);
          inet_addr_to_ip4addr(&if_addr, &imr->imr_interface);
          inet_addr_to_ip4addr(&multi_addr, &imr->imr_multiaddr);
          if (optname == IP_ADD_MEMBERSHIP) {
            if (!lwip_socket_register_membership(s, &if_addr, &multi_addr)) {
              /* cannot track membership (out of memory) */
              err = ENOMEM;
              igmp_err = ERR_OK;
            } else {
              igmp_err = igmp_joingroup(&if_addr, &multi_addr);
            }
          } else {
            igmp_err = igmp_leavegroup(&if_addr, &multi_addr);
            lwip_socket_unregister_membership(s, &if_addr, &multi_addr);
          }
          if (igmp_err != ERR_OK) {
            err = EADDRNOTAVAIL;
          }
        }
        break;
  #endif /* LWIP_IGMP */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_IP, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  
  #if LWIP_TCP
  /* Level: IPPROTO_TCP */
    case IPPROTO_TCP:
      /* Special case: all IPPROTO_TCP option take an int */
      LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, int, NETCONN_TCP);
      if (sock->conn->pcb.tcp->state == LISTEN) {
        return EINVAL;
      }
      switch (optname) {
      case TCP_NODELAY:
        if (*(const int*)optval) {
          tcp_nagle_disable(sock->conn->pcb.tcp);
        } else {
          tcp_nagle_enable(sock->conn->pcb.tcp);
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_NODELAY) -> %s\n",
                    s, (*(const int *)optval)?"on":"off") );
        break;
      case TCP_KEEPALIVE:
        sock->conn->pcb.tcp->keep_idle = (u32_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPALIVE) -> %"U32_F"\n",
                    s, sock->conn->pcb.tcp->keep_idle));
        break;
  
  #if LWIP_TCP_KEEPALIVE
      case TCP_KEEPIDLE:
        sock->conn->pcb.tcp->keep_idle = 1000*(u32_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPIDLE) -> %"U32_F"\n",
                    s, sock->conn->pcb.tcp->keep_idle));
        break;
      case TCP_KEEPINTVL:
        sock->conn->pcb.tcp->keep_intvl = 1000*(u32_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPINTVL) -> %"U32_F"\n",
                    s, sock->conn->pcb.tcp->keep_intvl));
        break;
      case TCP_KEEPCNT:
        sock->conn->pcb.tcp->keep_cnt = (u32_t)(*(const int*)optval);
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, TCP_KEEPCNT) -> %"U32_F"\n",
                    s, sock->conn->pcb.tcp->keep_cnt));
        break;
  #endif /* LWIP_TCP_KEEPALIVE */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_TCP, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_TCP*/
  
  #if LWIP_IPV6
  /* Level: IPPROTO_IPV6 */
    case IPPROTO_IPV6:
      switch (optname) {
      case IPV6_V6ONLY:
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, int, NETCONN_TCP);
        if (*(const int*)optval) {
          netconn_set_ipv6only(sock->conn, 1);
        } else {
          netconn_set_ipv6only(sock->conn, 0);
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_IPV6, IPV6_V6ONLY, ..) -> %d\n",
                    s, (netconn_get_ipv6only(sock->conn) ? 1 : 0)));
        break;
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_IPV6, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_IPV6 */
  
  #if LWIP_UDP && LWIP_UDPLITE
    /* Level: IPPROTO_UDPLITE */
    case IPPROTO_UDPLITE:
      /* Special case: all IPPROTO_UDPLITE option take an int */
      LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB(sock, optlen, int);
      /* If this is no UDP lite socket, ignore any options. */
      if (!NETCONNTYPE_ISUDPLITE(netconn_type(sock->conn))) {
        return ENOPROTOOPT;
      }
      switch (optname) {
      case UDPLITE_SEND_CSCOV:
        if ((*(const int*)optval != 0) && ((*(const int*)optval < 8) || (*(const int*)optval > 0xffff))) {
          /* don't allow illegal values! */
          sock->conn->pcb.udp->chksum_len_tx = 8;
        } else {
          sock->conn->pcb.udp->chksum_len_tx = (u16_t)*(const int*)optval;
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_UDPLITE, UDPLITE_SEND_CSCOV) -> %d\n",
                    s, (*(const int*)optval)) );
        break;
      case UDPLITE_RECV_CSCOV:
        if ((*(const int*)optval != 0) && ((*(const int*)optval < 8) || (*(const int*)optval > 0xffff))) {
          /* don't allow illegal values! */
          sock->conn->pcb.udp->chksum_len_rx = 8;
        } else {
          sock->conn->pcb.udp->chksum_len_rx = (u16_t)*(const int*)optval;
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_UDPLITE, UDPLITE_RECV_CSCOV) -> %d\n",
                    s, (*(const int*)optval)) );
        break;
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_UDPLITE, UNIMPL: optname=0x%x, ..)\n",
                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
  #endif /* LWIP_UDP */
    /* Level: IPPROTO_RAW */
    case IPPROTO_RAW:
      switch (optname) {
  #if LWIP_IPV6 && LWIP_RAW
      case IPV6_CHECKSUM:
        /* It should not be possible to disable the checksum generation with ICMPv6
         * as per RFC 3542 chapter 3.1 */
        if(sock->conn->pcb.raw->protocol == IPPROTO_ICMPV6) {
          return EINVAL;
        }
  
        LWIP_SOCKOPT_CHECK_OPTLEN_CONN_PCB_TYPE(sock, optlen, int, NETCONN_RAW);
        if (*(const int *)optval < 0) {
          sock->conn->pcb.raw->chksum_reqd = 0;
        } else if (*(const int *)optval & 1) {
          /* Per RFC3542, odd offsets are not allowed */
          return EINVAL;
        } else {
          sock->conn->pcb.raw->chksum_reqd = 1;
          sock->conn->pcb.raw->chksum_offset = (u16_t)*(const int *)optval;
        }
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_RAW, IPV6_CHECKSUM, ..) -> %d\n",
                    s, sock->conn->pcb.raw->chksum_reqd));
        break;
  #endif /* LWIP_IPV6 && LWIP_RAW */
      default:
        LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, IPPROTO_RAW, UNIMPL: optname=0x%x, ..)\n",
                                    s, optname));
        err = ENOPROTOOPT;
        break;
      }  /* switch (optname) */
      break;
    default:
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_setsockopt(%d, level=0x%x, UNIMPL: optname=0x%x, ..)\n",
                  s, level, optname));
      err = ENOPROTOOPT;
      break;
    }  /* switch (level) */
  
    return err;
  }
  
  int
  lwip_ioctl(int s, long cmd, void *argp)
  {
    struct lwip_sock *sock = get_socket(s);
    u8_t val;
  #if LWIP_SO_RCVBUF
    u16_t buflen = 0;
    int recv_avail;
  #endif /* LWIP_SO_RCVBUF */
  
    if (!sock) {
      return -1;
    }
  
    switch (cmd) {
  #if LWIP_SO_RCVBUF || LWIP_FIONREAD_LINUXMODE
    case FIONREAD:
      if (!argp) {
        sock_set_errno(sock, EINVAL);
        return -1;
      }
  #if LWIP_FIONREAD_LINUXMODE
      if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
        struct pbuf *p;
        if (sock->lastdata) {
          p = ((struct netbuf *)sock->lastdata)->p;
          *((int*)argp) = p->tot_len - sock->lastoffset;
        } else {
          struct netbuf *rxbuf;
          err_t err;
          if (sock->rcvevent <= 0) {
            *((int*)argp) = 0;
          } else {
            err = netconn_recv(sock->conn, &rxbuf);
            if (err != ERR_OK) {
              *((int*)argp) = 0;
            } else {
              sock->lastdata = rxbuf;
              sock->lastoffset = 0;
              *((int*)argp) = rxbuf->p->tot_len;
            }
          }
        }
        return 0;
      }
  #endif /* LWIP_FIONREAD_LINUXMODE */
  
  #if LWIP_SO_RCVBUF
      /* we come here if either LWIP_FIONREAD_LINUXMODE==0 or this is a TCP socket */
      SYS_ARCH_GET(sock->conn->recv_avail, recv_avail);
      if (recv_avail < 0) {
        recv_avail = 0;
      }
      *((int*)argp) = recv_avail;
  
      /* Check if there is data left from the last recv operation. /maq 041215 */
      if (sock->lastdata) {
        struct pbuf *p = (struct pbuf *)sock->lastdata;
        if (NETCONNTYPE_GROUP(netconn_type(sock->conn)) != NETCONN_TCP) {
          p = ((struct netbuf *)p)->p;
        }
        buflen = p->tot_len;
        buflen -= sock->lastoffset;
  
        *((int*)argp) += buflen;
      }
  
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_ioctl(%d, FIONREAD, %p) = %"U16_F"\n", s, argp, *((u16_t*)argp)));
      sock_set_errno(sock, 0);
      return 0;
  #else /* LWIP_SO_RCVBUF */
      break;
  #endif /* LWIP_SO_RCVBUF */
  #endif /* LWIP_SO_RCVBUF || LWIP_FIONREAD_LINUXMODE */
  
    case (long)FIONBIO:
      val = 0;
      if (argp && *(u32_t*)argp) {
        val = 1;
      }
      netconn_set_nonblocking(sock->conn, val);
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_ioctl(%d, FIONBIO, %d)\n", s, val));
      sock_set_errno(sock, 0);
      return 0;
  
    default:
      break;
    } /* switch (cmd) */
    LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_ioctl(%d, UNIMPL: 0x%lx, %p)\n", s, cmd, argp));
    sock_set_errno(sock, ENOSYS); /* not yet implemented */
    return -1;
  }
  
  /** A minimal implementation of fcntl.
   * Currently only the commands F_GETFL and F_SETFL are implemented.
   * Only the flag O_NONBLOCK is implemented.
   */
  int
  lwip_fcntl(int s, int cmd, int val)
  {
    struct lwip_sock *sock = get_socket(s);
    int ret = -1;
  
    if (!sock) {
      return -1;
    }
  
    switch (cmd) {
    case F_GETFL:
      ret = netconn_is_nonblocking(sock->conn) ? O_NONBLOCK : 0;
      sock_set_errno(sock, 0);
      break;
    case F_SETFL:
      if ((val & ~O_NONBLOCK) == 0) {
        /* only O_NONBLOCK, all other bits are zero */
        netconn_set_nonblocking(sock->conn, val & O_NONBLOCK);
        ret = 0;
        sock_set_errno(sock, 0);
      } else {
        sock_set_errno(sock, ENOSYS); /* not yet implemented */
      }
      break;
    default:
      LWIP_DEBUGF(SOCKETS_DEBUG, ("lwip_fcntl(%d, UNIMPL: %d, %d)\n", s, cmd, val));
      sock_set_errno(sock, ENOSYS); /* not yet implemented */
      break;
    }
    return ret;
  }
  
  #if LWIP_IGMP
  /** Register a new IGMP membership. On socket close, the membership is dropped automatically.
   *
   * ATTENTION: this function is called from tcpip_thread (or under CORE_LOCK).
   *
   * @return 1 on success, 0 on failure
   */
  static int
  lwip_socket_register_membership(int s, const ip4_addr_t *if_addr, const ip4_addr_t *multi_addr)
  {
    struct lwip_sock *sock = get_socket(s);
    int i;
  
    if (!sock) {
      return 0;
    }
  
    for (i = 0; i < LWIP_SOCKET_MAX_MEMBERSHIPS; i++) {
      if (socket_ipv4_multicast_memberships[i].sock == NULL) {
        socket_ipv4_multicast_memberships[i].sock = sock;
        ip4_addr_copy(socket_ipv4_multicast_memberships[i].if_addr, *if_addr);
        ip4_addr_copy(socket_ipv4_multicast_memberships[i].multi_addr, *multi_addr);
        return 1;
      }
    }
    return 0;
  }
  
  /** Unregister a previously registered membership. This prevents dropping the membership
   * on socket close.
   *
   * ATTENTION: this function is called from tcpip_thread (or under CORE_LOCK).
   */
  static void
  lwip_socket_unregister_membership(int s, const ip4_addr_t *if_addr, const ip4_addr_t *multi_addr)
  {
    struct lwip_sock *sock = get_socket(s);
    int i;
  
    if (!sock) {
      return;
    }
  
    for (i = 0; i < LWIP_SOCKET_MAX_MEMBERSHIPS; i++) {
      if ((socket_ipv4_multicast_memberships[i].sock == sock) &&
          ip4_addr_cmp(&socket_ipv4_multicast_memberships[i].if_addr, if_addr) &&
          ip4_addr_cmp(&socket_ipv4_multicast_memberships[i].multi_addr, multi_addr)) {
        socket_ipv4_multicast_memberships[i].sock = NULL;
        ip4_addr_set_zero(&socket_ipv4_multicast_memberships[i].if_addr);
        ip4_addr_set_zero(&socket_ipv4_multicast_memberships[i].multi_addr);
        return;
      }
    }
  }
  
  /** Drop all memberships of a socket that were not dropped explicitly via setsockopt.
   *
   * ATTENTION: this function is NOT called from tcpip_thread (or under CORE_LOCK).
   */
  static void
  lwip_socket_drop_registered_memberships(int s)
  {
    struct lwip_sock *sock = get_socket(s);
    int i;
  
    if (!sock) {
      return;
    }
  
    for (i = 0; i < LWIP_SOCKET_MAX_MEMBERSHIPS; i++) {
      if (socket_ipv4_multicast_memberships[i].sock == sock) {
        ip_addr_t multi_addr, if_addr;
        ip_addr_copy_from_ip4(multi_addr, socket_ipv4_multicast_memberships[i].multi_addr);
        ip_addr_copy_from_ip4(if_addr, socket_ipv4_multicast_memberships[i].if_addr);
        socket_ipv4_multicast_memberships[i].sock = NULL;
        ip4_addr_set_zero(&socket_ipv4_multicast_memberships[i].if_addr);
        ip4_addr_set_zero(&socket_ipv4_multicast_memberships[i].multi_addr);
  
        netconn_join_leave_group(sock->conn, &multi_addr, &if_addr, NETCONN_LEAVE);
      }
    }
  }
  #endif /* LWIP_IGMP */
  #endif /* LWIP_SOCKET */
  