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path: root/src/util/network.c
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/*
     This file is part of GNUnet.
     Copyright (C) 2009-2013 GNUnet e.V.

     GNUnet is free software: you can redistribute it and/or modify it
     under the terms of the GNU Affero General Public License as published
     by the Free Software Foundation, either version 3 of the License,
     or (at your option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Affero General Public License for more details.

     You should have received a copy of the GNU Affero General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.

     SPDX-License-Identifier: AGPL3.0-or-later
 */

/**
 * @file util/network.c
 * @brief basic, low-level networking interface
 * @author Nils Durner
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_util_lib.h"
#include "disk.h"

#define LOG(kind, ...) GNUNET_log_from(kind, "util-network", __VA_ARGS__)
#define LOG_STRERROR_FILE(kind, syscall, filename) GNUNET_log_from_strerror_file(kind, "util-network", syscall, filename)
#define LOG_STRERROR(kind, syscall) GNUNET_log_from_strerror(kind, "util-network", syscall)

#define DEBUG_NETWORK GNUNET_EXTRA_LOGGING


#ifndef INVALID_SOCKET
#define INVALID_SOCKET -1
#endif


/**
 * @brief handle to a socket
 */
struct GNUNET_NETWORK_Handle {
  int fd;

  /**
   * Address family / domain.
   */
  int af;

  /**
   * Type of the socket
   */
  int type;

  /**
   * Number of bytes in addr.
   */
  socklen_t addrlen;

  /**
   * Address we were bound to, or NULL.
   */
  struct sockaddr *addr;
};


/**
 * Test if the given protocol family is supported by this system.
 *
 * @param pf protocol family to test (PF_INET, PF_INET6, PF_UNIX)
 * @return #GNUNET_OK if the PF is supported
 */
int
GNUNET_NETWORK_test_pf(int pf)
{
  static int cache_v4 = -1;
  static int cache_v6 = -1;
  static int cache_un = -1;
  int s;
  int ret;

  switch (pf)
    {
    case PF_INET:
      if (-1 != cache_v4)
        return cache_v4;
      break;

    case PF_INET6:
      if (-1 != cache_v6)
        return cache_v6;
      break;

#ifdef PF_UNIX
    case PF_UNIX:
      if (-1 != cache_un)
        return cache_un;
      break;
#endif
    }
  s = socket(pf, SOCK_STREAM, 0);
  if (-1 == s)
    {
      if (EAFNOSUPPORT != errno)
        {
          GNUNET_log_strerror(GNUNET_ERROR_TYPE_WARNING,
                              "socket");
          return GNUNET_SYSERR;
        }
      ret = GNUNET_NO;
    }
  else
    {
      close(s);
      ret = GNUNET_OK;
    }
  switch (pf)
    {
    case PF_INET:
      cache_v4 = ret;
      break;

    case PF_INET6:
      cache_v6 = ret;
      break;

#ifdef PF_UNIX
    case PF_UNIX:
      cache_un = ret;
      break;
#endif
    }
  return ret;
}


/**
 * Given a unixpath that is too long (larger than UNIX_PATH_MAX),
 * shorten it to an acceptable length while keeping it unique
 * and making sure it remains a valid filename (if possible).
 *
 * @param unixpath long path, will be freed (or same pointer returned
 *        with moved 0-termination).
 * @return shortened unixpath, NULL on error
 */
char *
GNUNET_NETWORK_shorten_unixpath(char *unixpath)
{
  struct sockaddr_un dummy;
  size_t slen;
  char *end;
  struct GNUNET_HashCode sh;
  struct GNUNET_CRYPTO_HashAsciiEncoded ae;
  size_t upm;

  upm = sizeof(dummy.sun_path);
  slen = strlen(unixpath);
  if (slen < upm)
    return unixpath; /* no shortening required */
  GNUNET_CRYPTO_hash(unixpath, slen, &sh);
  while (16 + strlen(unixpath) >= upm)
    {
      if (NULL == (end = strrchr(unixpath, '/')))
        {
          GNUNET_log(GNUNET_ERROR_TYPE_ERROR,
                     _("Unable to shorten unix path `%s' while keeping name unique\n"),
                     unixpath);
          GNUNET_free(unixpath);
          return NULL;
        }
      *end = '\0';
    }
  GNUNET_CRYPTO_hash_to_enc(&sh, &ae);
  ae.encoding[16] = '\0';
  strcat(unixpath, (char *)ae.encoding);
  return unixpath;
}


/**
 * If services crash, they can leave a unix domain socket file on the
 * disk. This needs to be manually removed, because otherwise both
 * bind() and connect() for the respective address will fail.  In this
 * function, we test if such a left-over file exists, and if so,
 * remove it (unless there is a listening service at the address).
 *
 * @param un unix domain socket address to check
 */
void
GNUNET_NETWORK_unix_precheck(const struct sockaddr_un *un)
{
  int s;
  int eno;
  struct stat sbuf;
  int ret;

  s = socket(AF_UNIX, SOCK_STREAM, 0);
  if (-1 == s)
    {
      GNUNET_log_strerror(GNUNET_ERROR_TYPE_WARNING,
                          "Failed to open AF_UNIX socket");
      return;
    }
  ret = connect(s,
                (struct sockaddr *)un,
                sizeof(struct sockaddr_un));
  eno = errno;
  GNUNET_break(0 == close(s));
  if (0 == ret)
    return; /* another process is listening, do not remove! */
  if (ECONNREFUSED != eno)
    return; /* some other error, likely "no such file or directory" -- all well */
  /* should unlink, but sanity checks first */
  if (0 != stat(un->sun_path,
                &sbuf))
    return; /* failed to 'stat', likely does not exist after all */
  if (S_IFSOCK != (S_IFMT & sbuf.st_mode))
    return; /* refuse to unlink anything except sockets */
  /* finally, really unlink */
  GNUNET_log(GNUNET_ERROR_TYPE_INFO,
             "Removing left-over `%s' from previous exeuction\n",
             un->sun_path);
  if (0 != unlink(un->sun_path))
    GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING,
                             "unlink",
                             un->sun_path);
}


#ifndef FD_COPY
#define FD_COPY(s, d) do { GNUNET_memcpy((d), (s), sizeof(fd_set)); } while (0)
#endif


/**
 * Set if a socket should use blocking or non-blocking IO.
 *
 * @param fd socket
 * @param doBlock blocking mode
 * @return #GNUNET_OK on success, #GNUNET_SYSERR on error
 */
int
GNUNET_NETWORK_socket_set_blocking(struct GNUNET_NETWORK_Handle *fd,
                                   int doBlock)
{
  int flags = fcntl(fd->fd, F_GETFL);

  if (flags == -1)
    {
      LOG_STRERROR(GNUNET_ERROR_TYPE_WARNING,
                   "fcntl");
      return GNUNET_SYSERR;
    }
  if (doBlock)
    flags &= ~O_NONBLOCK;

  else
    flags |= O_NONBLOCK;
  if (0 != fcntl(fd->fd,
                 F_SETFL,
                 flags))

    {
      LOG_STRERROR(GNUNET_ERROR_TYPE_WARNING,
                   "fcntl");
      return GNUNET_SYSERR;
    }
  return GNUNET_OK;
}


/**
 * Make a socket non-inheritable to child processes
 *
 * @param h the socket to make non-inheritable
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 * @warning Not implemented on Windows
 */
static int
socket_set_inheritable(const struct GNUNET_NETWORK_Handle *h)
{
  int i;
  i = fcntl(h->fd, F_GETFD);
  if (i < 0)
    return GNUNET_SYSERR;
  if (i == (i | FD_CLOEXEC))
    return GNUNET_OK;
  i |= FD_CLOEXEC;
  if (fcntl(h->fd, F_SETFD, i) < 0)
    return GNUNET_SYSERR;

  return GNUNET_OK;
}


#ifdef DARWIN
/**
 * The MSG_NOSIGNAL equivalent on Mac OS X
 *
 * @param h the socket to make non-delaying
 */
static int
socket_set_nosigpipe(const struct GNUNET_NETWORK_Handle *h)
{
  int abs_value = 1;

  if (0 !=
      setsockopt(h->fd, SOL_SOCKET, SO_NOSIGPIPE,
                 (const void *)&abs_value,
                 sizeof(abs_value)))
    return GNUNET_SYSERR;
  return GNUNET_OK;
}
#endif


/**
 * Disable delays when sending data via the socket.
 * (GNUnet makes sure that messages are as big as
 * possible already).
 *
 * @param h the socket to make non-delaying
 */
static void
socket_set_nodelay(const struct GNUNET_NETWORK_Handle *h)
{
  int value = 1;

  if (0 !=
      setsockopt(h->fd,
                 IPPROTO_TCP,
                 TCP_NODELAY,
                 &value, sizeof(value)))
    LOG_STRERROR(GNUNET_ERROR_TYPE_WARNING,
                 "setsockopt");
}


/**
 * Perform proper canonical initialization for a network handle.
 * Set it to non-blocking, make it non-inheritable to child
 * processes, disable SIGPIPE, enable "nodelay" (if non-UNIX
 * stream socket) and check that it is smaller than FD_SETSIZE.
 *
 * @param h socket to initialize
 * @param af address family of the socket
 * @param type socket type
 * @return #GNUNET_OK on success, #GNUNET_SYSERR if initialization
 *         failed and the handle was destroyed
 */
static int
initialize_network_handle(struct GNUNET_NETWORK_Handle *h,
                          int af,
                          int type)
{
  int eno;

  h->af = af;
  h->type = type;
  if (h->fd == INVALID_SOCKET)
    {
      eno = errno;
      GNUNET_free(h);
      errno = eno;
      return GNUNET_SYSERR;
    }

  if (h->fd >= FD_SETSIZE)
    {
      GNUNET_break(GNUNET_OK == GNUNET_NETWORK_socket_close(h));
      errno = EMFILE;
      return GNUNET_SYSERR;
    }

  if (GNUNET_OK != socket_set_inheritable(h))
    LOG_STRERROR(GNUNET_ERROR_TYPE_ERROR | GNUNET_ERROR_TYPE_BULK,
                 "socket_set_inheritable");

  if (GNUNET_SYSERR == GNUNET_NETWORK_socket_set_blocking(h, GNUNET_NO))
    {
      eno = errno;
      GNUNET_break(0);
      GNUNET_break(GNUNET_OK == GNUNET_NETWORK_socket_close(h));
      errno = eno;
      return GNUNET_SYSERR;
    }
#ifdef DARWIN
  if (GNUNET_SYSERR == socket_set_nosigpipe(h))
    {
      eno = errno;
      GNUNET_break(0);
      GNUNET_break(GNUNET_OK == GNUNET_NETWORK_socket_close(h));
      errno = eno;
      return GNUNET_SYSERR;
    }
#endif
  if ((type == SOCK_STREAM)
#ifdef AF_UNIX
      && (af != AF_UNIX)
#endif
      )
    socket_set_nodelay(h);
  return GNUNET_OK;
}


/**
 * accept a new connection on a socket
 *
 * @param desc bound socket
 * @param address address of the connecting peer, may be NULL
 * @param address_len length of @a address
 * @return client socket
 */
struct GNUNET_NETWORK_Handle *
GNUNET_NETWORK_socket_accept(const struct GNUNET_NETWORK_Handle *desc,
                             struct sockaddr *address,
                             socklen_t *address_len)
{
  struct GNUNET_NETWORK_Handle *ret;
  int eno;

  ret = GNUNET_new(struct GNUNET_NETWORK_Handle);
#if DEBUG_NETWORK
  {
    struct sockaddr_storage name;
    socklen_t namelen = sizeof(name);

    int gsn = getsockname(desc->fd,
                          (struct sockaddr *)&name,
                          &namelen);

    if (0 == gsn)
      LOG(GNUNET_ERROR_TYPE_DEBUG,
          "Accepting connection on `%s'\n",
          GNUNET_a2s((const struct sockaddr *)&name,
                     namelen));
  }
#endif
  ret->fd = accept(desc->fd,
                   address,
                   address_len);
  if (-1 == ret->fd)
    {
      eno = errno;
      GNUNET_free(ret);
      errno = eno;
      return NULL;
    }
  if (GNUNET_OK !=
      initialize_network_handle(ret,
                                (NULL != address) ? address->sa_family : desc->af,
                                SOCK_STREAM))
    {
      return NULL;
    }
  return ret;
}


/**
 * Bind a socket to a particular address.
 *
 * @param desc socket to bind
 * @param address address to be bound
 * @param address_len length of @a address
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_bind(struct GNUNET_NETWORK_Handle *desc,
                           const struct sockaddr *address,
                           socklen_t address_len)
{
  int ret;

#ifdef IPV6_V6ONLY
#ifdef IPPROTO_IPV6
  {
    const int on = 1;

    if (AF_INET6 == desc->af)
      if (setsockopt(desc->fd,
                     IPPROTO_IPV6,
                     IPV6_V6ONLY,
                     (const void *)&on,
                     sizeof(on)))
        LOG_STRERROR(GNUNET_ERROR_TYPE_DEBUG,
                     "setsockopt");
  }
#endif
#endif
  if (AF_UNIX == address->sa_family)
    GNUNET_NETWORK_unix_precheck((const struct sockaddr_un *)address);
  {
    const int on = 1;

    /* This is required here for TCP sockets, but only on UNIX */
    if ((SOCK_STREAM == desc->type) &&
        (0 != setsockopt(desc->fd,
                         SOL_SOCKET,
                         SO_REUSEADDR,
                         &on, sizeof(on))))
      LOG_STRERROR(GNUNET_ERROR_TYPE_DEBUG,
                   "setsockopt");
  }
  {
    /* set permissions of newly created non-abstract UNIX domain socket to
       "user-only"; applications can choose to relax this later */
    mode_t old_mask = 0; /* assigned to make compiler happy */
    const struct sockaddr_un *un = (const struct sockaddr_un *)address;
    int not_abstract = 0;

    if ((AF_UNIX == address->sa_family)
        && ('\0' != un->sun_path[0]))  /* Not an abstract socket */
      not_abstract = 1;
    if (not_abstract)
      old_mask = umask(S_IWGRP | S_IRGRP | S_IXGRP | S_IWOTH | S_IROTH | S_IXOTH);

  ret = bind(desc->fd,
             address,
             address_len);

  if (not_abstract)
    (void)umask(old_mask);
}
  if (0 != ret)
    return GNUNET_SYSERR;

  desc->addr = GNUNET_malloc(address_len);
  GNUNET_memcpy(desc->addr, address, address_len);
  desc->addrlen = address_len;

  return GNUNET_OK;
}


/**
 * Close a socket
 *
 * @param desc socket
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_close(struct GNUNET_NETWORK_Handle *desc)
{
  int ret;

  ret = close(desc->fd);

  const struct sockaddr_un *un = (const struct sockaddr_un *)desc->addr;

  /* Cleanup the UNIX domain socket and its parent directories in case of non
     abstract sockets */
  if ((AF_UNIX == desc->af) &&
      (NULL != desc->addr) &&
      ('\0' != un->sun_path[0]))
    {
      char *dirname = GNUNET_strndup(un->sun_path,
                                     sizeof(un->sun_path));

      if (0 != unlink(dirname))
        {
          LOG_STRERROR_FILE(GNUNET_ERROR_TYPE_WARNING,
                            "unlink",
                            dirname);
        }
      else
        {
          size_t len;

          len = strlen(dirname);
          while ((len > 0) && (dirname[len] != DIR_SEPARATOR))
            len--;
          dirname[len] = '\0';
          if ((0 != len) && (0 != rmdir(dirname)))
            {
              switch (errno)
                {
                case EACCES:
                case ENOTEMPTY:
                case EPERM:
                  /* these are normal and can just be ignored */
                  break;

                default:
                  GNUNET_log_strerror_file(GNUNET_ERROR_TYPE_WARNING,
                                           "rmdir",
                                           dirname);
                  break;
                }
            }
        }
      GNUNET_free(dirname);
    }
  GNUNET_NETWORK_socket_free_memory_only_(desc);
  return (ret == 0) ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Only free memory of a socket, keep the file descriptor untouched.
 *
 * @param desc socket
 */
void
GNUNET_NETWORK_socket_free_memory_only_(struct GNUNET_NETWORK_Handle *desc)
{
  GNUNET_free_non_null(desc->addr);
  GNUNET_free(desc);
}


/**
 * Box a native socket (and check that it is a socket).
 *
 * @param fd socket to box
 * @return NULL on error (including not supported on target platform)
 */
struct GNUNET_NETWORK_Handle *
GNUNET_NETWORK_socket_box_native(SOCKTYPE fd)
{
  struct GNUNET_NETWORK_Handle *ret;

  if (fcntl(fd, F_GETFD) < 0)
    return NULL;                /* invalid FD */
  ret = GNUNET_new(struct GNUNET_NETWORK_Handle);
  ret->fd = fd;
  ret->af = AF_UNSPEC;
  return ret;
}


/**
 * Connect a socket to some remote address.
 *
 * @param desc socket
 * @param address peer address
 * @param address_len length of @a address
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_connect(const struct GNUNET_NETWORK_Handle *desc,
                              const struct sockaddr *address,
                              socklen_t address_len)
{
  int ret;

  ret = connect(desc->fd,
                address,
                address_len);

  return ret == 0 ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Get socket options
 *
 * @param desc socket
 * @param level protocol level of the option
 * @param optname identifier of the option
 * @param optval options
 * @param optlen length of @a optval
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_getsockopt(const struct GNUNET_NETWORK_Handle *desc,
                                 int level,
                                 int optname,
                                 void *optval,
                                 socklen_t *optlen)
{
  int ret;

  ret = getsockopt(desc->fd,
                   level,
                   optname,
                   optval, optlen);

  return ret == 0 ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Listen on a socket
 *
 * @param desc socket
 * @param backlog length of the listen queue
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_listen(const struct GNUNET_NETWORK_Handle *desc,
                             int backlog)
{
  int ret;

  ret = listen(desc->fd,
               backlog);

  return ret == 0 ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * How much data is available to be read on this descriptor?
 *
 * @param desc socket
 * @returns #GNUNET_SYSERR if no data is available, or on error!
 */
ssize_t
GNUNET_NETWORK_socket_recvfrom_amount(const struct GNUNET_NETWORK_Handle *desc)
{
  int error;

  /* How much is there to be read? */
  int pending;

  error = ioctl(desc->fd,
                FIONREAD,
                &pending);
  if (0 == error)
    return (ssize_t)pending;
  return GNUNET_SYSERR;
}


/**
 * Read data from a socket (always non-blocking).
 *
 * @param desc socket
 * @param buffer buffer
 * @param length length of @a buffer
 * @param src_addr either the source to recv from, or all zeroes
 *        to be filled in by recvfrom
 * @param addrlen length of the @a src_addr
 */
ssize_t
GNUNET_NETWORK_socket_recvfrom(const struct GNUNET_NETWORK_Handle *desc,
                               void *buffer,
                               size_t length,
                               struct sockaddr *src_addr,
                               socklen_t *addrlen)
{
  int ret;
  int flags;

  flags = 0;

#ifdef MSG_DONTWAIT
  flags |= MSG_DONTWAIT;
#endif
  ret = recvfrom(desc->fd,
                 buffer,
                 length,
                 flags,
                 src_addr,
                 addrlen);
  return ret;
}


/**
 * Read data from a connected socket (always non-blocking).
 *
 * @param desc socket
 * @param buffer buffer
 * @param length length of @a buffer
 * @return number of bytes received, -1 on error
 */
ssize_t
GNUNET_NETWORK_socket_recv(const struct GNUNET_NETWORK_Handle *desc,
                           void *buffer,
                           size_t length)
{
  int ret;
  int flags;

  flags = 0;

#ifdef MSG_DONTWAIT
  flags |= MSG_DONTWAIT;
#endif
  ret = recv(desc->fd,
             buffer,
             length,
             flags);
  return ret;
}


/**
 * Send data (always non-blocking).
 *
 * @param desc socket
 * @param buffer data to send
 * @param length size of the @a buffer
 * @return number of bytes sent, #GNUNET_SYSERR on error
 */
ssize_t
GNUNET_NETWORK_socket_send(const struct GNUNET_NETWORK_Handle *desc,
                           const void *buffer,
                           size_t length)
{
  int ret;
  int flags;

  flags = 0;
#ifdef MSG_DONTWAIT
  flags |= MSG_DONTWAIT;
#endif
#ifdef MSG_NOSIGNAL
  flags |= MSG_NOSIGNAL;
#endif
  ret = send(desc->fd,
             buffer,
             length,
             flags);
  return ret;
}


/**
 * Send data to a particular destination (always non-blocking).
 * This function only works for UDP sockets.
 *
 * @param desc socket
 * @param message data to send
 * @param length size of the @a message
 * @param dest_addr destination address
 * @param dest_len length of @a address
 * @return number of bytes sent, #GNUNET_SYSERR on error
 */
ssize_t
GNUNET_NETWORK_socket_sendto(const struct GNUNET_NETWORK_Handle *desc,
                             const void *message,
                             size_t length,
                             const struct sockaddr *dest_addr,
                             socklen_t dest_len)
{
  int ret;
  int flags;

  flags = 0;

#ifdef MSG_DONTWAIT
  flags |= MSG_DONTWAIT;
#endif
#ifdef MSG_NOSIGNAL
  flags |= MSG_NOSIGNAL;
#endif
  ret = sendto(desc->fd, message, length, flags, dest_addr, dest_len);
  return ret;
}


/**
 * Set socket option
 *
 * @param fd socket
 * @param level protocol level of the option
 * @param option_name option identifier
 * @param option_value value to set
 * @param option_len size of @a option_value
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_setsockopt(struct GNUNET_NETWORK_Handle *fd,
                                 int level,
                                 int option_name,
                                 const void *option_value,
                                 socklen_t option_len)
{
  int ret;

  ret = setsockopt(fd->fd,
                   level,
                   option_name,
                   option_value,
                   option_len);

  return ret == 0 ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Create a new socket.  Configure it for non-blocking IO and
 * mark it as non-inheritable to child processes (set the
 * close-on-exec flag).
 *
 * @param domain domain of the socket
 * @param type socket type
 * @param protocol network protocol
 * @return new socket, NULL on error
 */
struct GNUNET_NETWORK_Handle *
GNUNET_NETWORK_socket_create(int domain,
                             int type,
                             int protocol)
{
  struct GNUNET_NETWORK_Handle *ret;
  int fd;

  fd = socket(domain, type, protocol);
  if (-1 == fd)
    return NULL;
  ret = GNUNET_new(struct GNUNET_NETWORK_Handle);
  ret->fd = fd;
  if (GNUNET_OK !=
      initialize_network_handle(ret,
                                domain,
                                type))
    return NULL;
  return ret;
}


/**
 * Shut down socket operations
 * @param desc socket
 * @param how type of shutdown
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_shutdown(struct GNUNET_NETWORK_Handle *desc,
                               int how)
{
  int ret;

  ret = shutdown(desc->fd, how);

  return (0 == ret) ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Disable the "CORK" feature for communication with the given socket,
 * forcing the OS to immediately flush the buffer on transmission
 * instead of potentially buffering multiple messages.  Essentially
 * reduces the OS send buffers to zero.
 *
 * @param desc socket
 * @return #GNUNET_OK on success, #GNUNET_SYSERR otherwise
 */
int
GNUNET_NETWORK_socket_disable_corking(struct GNUNET_NETWORK_Handle *desc)
{
  int ret = 0;

#if LINUX
  int value = 0;

  if (0 !=
      (ret =
         setsockopt(desc->fd,
                    SOL_SOCKET,
                    SO_SNDBUF,
                    &value,
                    sizeof(value))))
    LOG_STRERROR(GNUNET_ERROR_TYPE_WARNING,
                 "setsockopt");
  if (0 !=
      (ret =
         setsockopt(desc->fd,
                    SOL_SOCKET,
                    SO_RCVBUF,
                    &value,
                    sizeof(value))))
    LOG_STRERROR(GNUNET_ERROR_TYPE_WARNING,
                 "setsockopt");
#endif
  return ret == 0 ? GNUNET_OK : GNUNET_SYSERR;
}


/**
 * Reset FD set
 *
 * @param fds fd set
 */
void
GNUNET_NETWORK_fdset_zero(struct GNUNET_NETWORK_FDSet *fds)
{
  FD_ZERO(&fds->sds);
  fds->nsds = 0;
}


/**
 * Add a socket to the FD set
 *
 * @param fds fd set
 * @param desc socket to add
 */
void
GNUNET_NETWORK_fdset_set(struct GNUNET_NETWORK_FDSet *fds,
                         const struct GNUNET_NETWORK_Handle *desc)
{
  FD_SET(desc->fd,
         &fds->sds);
  fds->nsds = GNUNET_MAX(fds->nsds,
                         desc->fd + 1);
}


/**
 * Check whether a socket is part of the fd set
 *
 * @param fds fd set
 * @param desc socket
 * @return 0 if the FD is not set
 */
int
GNUNET_NETWORK_fdset_isset(const struct GNUNET_NETWORK_FDSet *fds,
                           const struct GNUNET_NETWORK_Handle *desc)
{
  return FD_ISSET(desc->fd,
                  &fds->sds);
}


/**
 * Add one fd set to another
 *
 * @param dst the fd set to add to
 * @param src the fd set to add from
 */
void
GNUNET_NETWORK_fdset_add(struct GNUNET_NETWORK_FDSet *dst,
                         const struct GNUNET_NETWORK_FDSet *src)
{
  int nfds;

  for (nfds = src->nsds; nfds >= 0; nfds--)
    if (FD_ISSET(nfds, &src->sds))
      FD_SET(nfds, &dst->sds);
  dst->nsds = GNUNET_MAX(dst->nsds,
                         src->nsds);
}


/**
 * Copy one fd set to another
 *
 * @param to destination
 * @param from source
 */
void
GNUNET_NETWORK_fdset_copy(struct GNUNET_NETWORK_FDSet *to,
                          const struct GNUNET_NETWORK_FDSet *from)
{
  FD_COPY(&from->sds,
          &to->sds);
  to->nsds = from->nsds;
}


/**
 * Return file descriptor for this network handle
 *
 * @param desc wrapper to process
 * @return POSIX file descriptor
 */
int
GNUNET_NETWORK_get_fd(const struct GNUNET_NETWORK_Handle *desc)
{
  return desc->fd;
}


/**
 * Return sockaddr for this network handle
 *
 * @param desc wrapper to process
 * @return sockaddr
 */
struct sockaddr*
GNUNET_NETWORK_get_addr(const struct GNUNET_NETWORK_Handle *desc)
{
  return desc->addr;
}


/**
 * Return sockaddr length for this network handle
 *
 * @param desc wrapper to process
 * @return socklen_t for sockaddr
 */
socklen_t
GNUNET_NETWORK_get_addrlen(const struct GNUNET_NETWORK_Handle *desc)
{
  return desc->addrlen;
}


/**
 * Copy a native fd set
 *
 * @param to destination
 * @param from native source set
 * @param nfds the biggest socket number in from + 1
 */
void
GNUNET_NETWORK_fdset_copy_native(struct GNUNET_NETWORK_FDSet *to,
                                 const fd_set *from,
                                 int nfds)
{
  FD_COPY(from,
          &to->sds);
  to->nsds = nfds;
}


/**
 * Set a native fd in a set
 *
 * @param to destination
 * @param nfd native FD to set
 */
void
GNUNET_NETWORK_fdset_set_native(struct GNUNET_NETWORK_FDSet *to,
                                int nfd)
{
  GNUNET_assert((nfd >= 0) && (nfd < FD_SETSIZE));
  FD_SET(nfd, &to->sds);
  to->nsds = GNUNET_MAX(nfd + 1,
                        to->nsds);
}


/**
 * Test native fd in a set
 *
 * @param to set to test, NULL for empty set
 * @param nfd native FD to test, or -1 for none
 * @return #GNUNET_YES if FD is set in the set
 */
int
GNUNET_NETWORK_fdset_test_native(const struct GNUNET_NETWORK_FDSet *to,
                                 int nfd)
{
  if ((-1 == nfd) ||
      (NULL == to))
    return GNUNET_NO;
  return FD_ISSET(nfd, &to->sds) ? GNUNET_YES : GNUNET_NO;
}


/**
 * Add a file handle to the fd set
 * @param fds fd set
 * @param h the file handle to add
 */
void
GNUNET_NETWORK_fdset_handle_set(struct GNUNET_NETWORK_FDSet *fds,
                                const struct GNUNET_DISK_FileHandle *h)
{
  int fd;

  GNUNET_assert(GNUNET_OK ==
                GNUNET_DISK_internal_file_handle_(h,
                                                  &fd,
                                                  sizeof(int)));
  FD_SET(fd,
         &fds->sds);
  fds->nsds = GNUNET_MAX(fd + 1,
                         fds->nsds);
}


/**
 * Add a file handle to the fd set
 * @param fds fd set
 * @param h the file handle to add
 */
void
GNUNET_NETWORK_fdset_handle_set_first(struct GNUNET_NETWORK_FDSet *fds,
                                      const struct GNUNET_DISK_FileHandle *h)
{
  GNUNET_NETWORK_fdset_handle_set(fds, h);
}


/**
 * Check if a file handle is part of an fd set
 *
 * @param fds fd set
 * @param h file handle
 * @return #GNUNET_YES if the file handle is part of the set
 */
int
GNUNET_NETWORK_fdset_handle_isset(const struct GNUNET_NETWORK_FDSet *fds,
                                  const struct GNUNET_DISK_FileHandle *h)
{
  return FD_ISSET(h->fd,
                  &fds->sds);
}


/**
 * Checks if two fd sets overlap
 *
 * @param fds1 first fd set
 * @param fds2 second fd set
 * @return #GNUNET_YES if they do overlap, #GNUNET_NO otherwise
 */
int
GNUNET_NETWORK_fdset_overlap(const struct GNUNET_NETWORK_FDSet *fds1,
                             const struct GNUNET_NETWORK_FDSet *fds2)
{
  int nfds;

  nfds = GNUNET_MIN(fds1->nsds,
                    fds2->nsds);
  while (nfds > 0)
    {
      nfds--;
      if ((FD_ISSET(nfds,
                    &fds1->sds)) &&
          (FD_ISSET(nfds,
                    &fds2->sds)))
        return GNUNET_YES;
    }
  return GNUNET_NO;
}


/**
 * Creates an fd set
 *
 * @return a new fd set
 */
struct GNUNET_NETWORK_FDSet *
GNUNET_NETWORK_fdset_create()
{
  struct GNUNET_NETWORK_FDSet *fds;

  fds = GNUNET_new(struct GNUNET_NETWORK_FDSet);
  GNUNET_NETWORK_fdset_zero(fds);
  return fds;
}


/**
 * Releases the associated memory of an fd set
 *
 * @param fds fd set
 */
void
GNUNET_NETWORK_fdset_destroy(struct GNUNET_NETWORK_FDSet *fds)
{
  GNUNET_free(fds);
}


/**
 * Test if the given @a port is available.
 *
 * @param ipproto transport protocol to test (i.e. IPPROTO_TCP)
 * @param port port number to test
 * @return #GNUNET_OK if the port is available, #GNUNET_NO if not
 */
int
GNUNET_NETWORK_test_port_free(int ipproto,
                              uint16_t port)
{
  struct GNUNET_NETWORK_Handle *socket;
  int bind_status;
  int socktype;
  char open_port_str[6];
  struct addrinfo hint;
  struct addrinfo *ret;
  struct addrinfo *ai;

  GNUNET_snprintf(open_port_str,
                  sizeof(open_port_str),
                  "%u",
                  (unsigned int)port);
  socktype = (IPPROTO_TCP == ipproto) ? SOCK_STREAM : SOCK_DGRAM;
  ret = NULL;
  memset(&hint, 0, sizeof(hint));
  hint.ai_family = AF_UNSPEC; /* IPv4 and IPv6 */
  hint.ai_socktype = socktype;
  hint.ai_protocol = ipproto;
  hint.ai_addrlen = 0;
  hint.ai_addr = NULL;
  hint.ai_canonname = NULL;
  hint.ai_next = NULL;
  hint.ai_flags = AI_PASSIVE | AI_NUMERICSERV; /* Wild card address */
  GNUNET_assert(0 == getaddrinfo(NULL,
                                 open_port_str,
                                 &hint,
                                 &ret));
  bind_status = GNUNET_NO;
  for (ai = ret; NULL != ai; ai = ai->ai_next)
    {
      socket = GNUNET_NETWORK_socket_create(ai->ai_family,
                                            ai->ai_socktype,
                                            ai->ai_protocol);
      if (NULL == socket)
        continue;
      bind_status = GNUNET_NETWORK_socket_bind(socket,
                                               ai->ai_addr,
                                               ai->ai_addrlen);
      GNUNET_NETWORK_socket_close(socket);
      if (GNUNET_OK != bind_status)
        break;
    }
  freeaddrinfo(ret);
  return bind_status;
}


/**
 * Check if sockets or pipes meet certain conditions
 *
 * @param rfds set of sockets or pipes to be checked for readability
 * @param wfds set of sockets or pipes to be checked for writability
 * @param efds set of sockets or pipes to be checked for exceptions
 * @param timeout relative value when to return
 * @return number of selected sockets or pipes, #GNUNET_SYSERR on error
 */
int
GNUNET_NETWORK_socket_select(struct GNUNET_NETWORK_FDSet *rfds,
                             struct GNUNET_NETWORK_FDSet *wfds,
                             struct GNUNET_NETWORK_FDSet *efds,
                             const struct GNUNET_TIME_Relative timeout)
{
  int nfds;
  struct timeval tv;

  if (NULL != rfds)
    nfds = rfds->nsds;
  else
    nfds = 0;
  if (NULL != wfds)
    nfds = GNUNET_MAX(nfds,
                      wfds->nsds);
  if (NULL != efds)
    nfds = GNUNET_MAX(nfds,
                      efds->nsds);
  if ((0 == nfds) &&
      (timeout.rel_value_us == GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us))
    {
      GNUNET_break(0);
      LOG(GNUNET_ERROR_TYPE_ERROR,
          _("Fatal internal logic error, process hangs in `%s' (abort with CTRL-C)!\n"),
          "select");
    }
  if (timeout.rel_value_us / GNUNET_TIME_UNIT_SECONDS.rel_value_us > (unsigned long long)LONG_MAX)
    {
      tv.tv_sec = LONG_MAX;
      tv.tv_usec = 999999L;
    }
  else
    {
      tv.tv_sec = (long)(timeout.rel_value_us / GNUNET_TIME_UNIT_SECONDS.rel_value_us);
      tv.tv_usec =
        (timeout.rel_value_us -
         (tv.tv_sec * GNUNET_TIME_UNIT_SECONDS.rel_value_us));
    }
  return select(nfds,
                (NULL != rfds) ? &rfds->sds : NULL,
                (NULL != wfds) ? &wfds->sds : NULL,
                (NULL != efds) ? &efds->sds : NULL,
                (timeout.rel_value_us ==
                 GNUNET_TIME_UNIT_FOREVER_REL.rel_value_us) ? NULL : &tv);
}

/* end of network.c */