text: /*
   * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at:
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include <config.h>
  #include "util.h"
  #include <ctype.h>
  #include <errno.h>
  #include <limits.h>
  #include <pthread.h>
  #include <stdarg.h>
  #include <stdint.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/stat.h>
  #include <unistd.h>
  #include "bitmap.h"
  #include "byte-order.h"
  #include "coverage.h"
  #include "ovs-rcu.h"
  #include "ovs-thread.h"
  #include "socket-util.h"
  #include "vlog.h"
  #ifdef HAVE_PTHREAD_SET_NAME_NP
  #include <pthread_np.h>
  #endif
  
  VLOG_DEFINE_THIS_MODULE(util);
  
  COVERAGE_DEFINE(util_xalloc);
  
  /* argv[0] without directory names. */
  char *program_name;
  
  /* Name for the currently running thread or process, for log messages, process
   * listings, and debuggers. */
  DEFINE_PER_THREAD_MALLOCED_DATA(char *, subprogram_name);
  
  /* --version option output. */
  static char *program_version;
  
  /* Buffer used by ovs_strerror() and ovs_format_message(). */
  DEFINE_STATIC_PER_THREAD_DATA(struct { char s[128]; },
                                strerror_buffer,
                                { "" });
  
  static char *xreadlink(const char *filename);
  
  void
  ovs_assert_failure(const char *where, const char *function,
                     const char *condition)
  {
      /* Prevent an infinite loop (or stack overflow) in case VLOG_ABORT happens
       * to trigger an assertion failure of its own. */
      static int reentry = 0;
  
      switch (reentry++) {
      case 0:
          VLOG_ABORT("%s: assertion %s failed in %s()",
                     where, condition, function);
          OVS_NOT_REACHED();
  
      case 1:
          fprintf(stderr, "%s: assertion %s failed in %s()",
                  where, condition, function);
          abort();
  
      default:
          abort();
      }
  }
  
  void
  out_of_memory(void)
  {
      ovs_abort(0, "virtual memory exhausted");
  }
  
  void *
  xcalloc(size_t count, size_t size)
  {
      void *p = count && size ? calloc(count, size) : malloc(1);
      COVERAGE_INC(util_xalloc);
      if (p == NULL) {
          out_of_memory();
      }
      return p;
  }
  
  void *
  xzalloc(size_t size)
  {
      return xcalloc(1, size);
  }
  
  void *
  xmalloc(size_t size)
  {
      void *p = malloc(size ? size : 1);
      COVERAGE_INC(util_xalloc);
      if (p == NULL) {
          out_of_memory();
      }
      return p;
  }
  
  void *
  xrealloc(void *p, size_t size)
  {
      p = realloc(p, size ? size : 1);
      COVERAGE_INC(util_xalloc);
      if (p == NULL) {
          out_of_memory();
      }
      return p;
  }
  
  void *
  xmemdup(const void *p_, size_t size)
  {
      void *p = xmalloc(size);
      memcpy(p, p_, size);
      return p;
  }
  
  char *
  xmemdup0(const char *p_, size_t length)
  {
      char *p = xmalloc(length + 1);
      memcpy(p, p_, length);
      p[length] = '\0';
      return p;
  }
  
  char *
  xstrdup(const char *s)
  {
      return xmemdup0(s, strlen(s));
  }
  
  char *
  xvasprintf(const char *format, va_list args)
  {
      va_list args2;
      size_t needed;
      char *s;
  
      va_copy(args2, args);
      needed = vsnprintf(NULL, 0, format, args);
  
      s = xmalloc(needed + 1);
  
      vsnprintf(s, needed + 1, format, args2);
      va_end(args2);
  
      return s;
  }
  
  void *
  x2nrealloc(void *p, size_t *n, size_t s)
  {
      *n = *n == 0 ? 1 : 2 * *n;
      return xrealloc(p, *n * s);
  }
  
  /* The desired minimum alignment for an allocated block of memory. */
  #define MEM_ALIGN MAX(sizeof(void *), 8)
  BUILD_ASSERT_DECL(IS_POW2(MEM_ALIGN));
  BUILD_ASSERT_DECL(CACHE_LINE_SIZE >= MEM_ALIGN);
  
  /* Allocates and returns 'size' bytes of memory in dedicated cache lines.  That
   * is, the memory block returned will not share a cache line with other data,
   * avoiding "false sharing".  (The memory returned will not be at the start of
   * a cache line, though, so don't assume such alignment.)
   *
   * Use free_cacheline() to free the returned memory block. */
  void *
  xmalloc_cacheline(size_t size)
  {
  #ifdef HAVE_POSIX_MEMALIGN
      void *p;
      int error;
  
      COVERAGE_INC(util_xalloc);
      error = posix_memalign(&p, CACHE_LINE_SIZE, size ? size : 1);
      if (error != 0) {
          out_of_memory();
      }
      return p;
  #else
      void **payload;
      void *base;
  
      /* Allocate room for:
       *
       *     - Up to CACHE_LINE_SIZE - 1 bytes before the payload, so that the
       *       start of the payload doesn't potentially share a cache line.
       *
       *     - A payload consisting of a void *, followed by padding out to
       *       MEM_ALIGN bytes, followed by 'size' bytes of user data.
       *
       *     - Space following the payload up to the end of the cache line, so
       *       that the end of the payload doesn't potentially share a cache line
       *       with some following block. */
      base = xmalloc((CACHE_LINE_SIZE - 1)
                     + ROUND_UP(MEM_ALIGN + size, CACHE_LINE_SIZE));
  
      /* Locate the payload and store a pointer to the base at the beginning. */
      payload = (void **) ROUND_UP((uintptr_t) base, CACHE_LINE_SIZE);
      *payload = base;
  
      return (char *) payload + MEM_ALIGN;
  #endif
  }
  
  /* Like xmalloc_cacheline() but clears the allocated memory to all zero
   * bytes. */
  void *
  xzalloc_cacheline(size_t size)
  {
      void *p = xmalloc_cacheline(size);
      memset(p, 0, size);
      return p;
  }
  
  /* Frees a memory block allocated with xmalloc_cacheline() or
   * xzalloc_cacheline(). */
  void
  free_cacheline(void *p)
  {
  #ifdef HAVE_POSIX_MEMALIGN
      free(p);
  #else
      if (p) {
          free(*(void **) ((uintptr_t) p - MEM_ALIGN));
      }
  #endif
  }
  
  char *
  xasprintf(const char *format, ...)
  {
      va_list args;
      char *s;
  
      va_start(args, format);
      s = xvasprintf(format, args);
      va_end(args);
  
      return s;
  }
  
  /* Similar to strlcpy() from OpenBSD, but it never reads more than 'size - 1'
   * bytes from 'src' and doesn't return anything. */
  void
  ovs_strlcpy(char *dst, const char *src, size_t size)
  {
      if (size > 0) {
          size_t len = strnlen(src, size - 1);
          memcpy(dst, src, len);
          dst[len] = '\0';
      }
  }
  
  /* Copies 'src' to 'dst'.  Reads no more than 'size - 1' bytes from 'src'.
   * Always null-terminates 'dst' (if 'size' is nonzero), and writes a zero byte
   * to every otherwise unused byte in 'dst'.
   *
   * Except for performance, the following call:
   *     ovs_strzcpy(dst, src, size);
   * is equivalent to these two calls:
   *     memset(dst, '\0', size);
   *     ovs_strlcpy(dst, src, size);
   *
   * (Thus, ovs_strzcpy() is similar to strncpy() without some of the pitfalls.)
   */
  void
  ovs_strzcpy(char *dst, const char *src, size_t size)
  {
      if (size > 0) {
          size_t len = strnlen(src, size - 1);
          memcpy(dst, src, len);
          memset(dst + len, '\0', size - len);
      }
  }
  
  /* Prints 'format' on stderr, formatting it like printf() does.  If 'err_no' is
   * nonzero, then it is formatted with ovs_retval_to_string() and appended to
   * the message inside parentheses.  Then, terminates with abort().
   *
   * This function is preferred to ovs_fatal() in a situation where it would make
   * sense for a monitoring process to restart the daemon.
   *
   * 'format' should not end with a new-line, because this function will add one
   * itself. */
  void
  ovs_abort(int err_no, const char *format, ...)
  {
      va_list args;
  
      va_start(args, format);
      ovs_abort_valist(err_no, format, args);
  }
  
  /* Same as ovs_abort() except that the arguments are supplied as a va_list. */
  void
  ovs_abort_valist(int err_no, const char *format, va_list args)
  {
      ovs_error_valist(err_no, format, args);
      abort();
  }
  
  /* Prints 'format' on stderr, formatting it like printf() does.  If 'err_no' is
   * nonzero, then it is formatted with ovs_retval_to_string() and appended to
   * the message inside parentheses.  Then, terminates with EXIT_FAILURE.
   *
   * 'format' should not end with a new-line, because this function will add one
   * itself. */
  void
  ovs_fatal(int err_no, const char *format, ...)
  {
      va_list args;
  
      va_start(args, format);
      ovs_fatal_valist(err_no, format, args);
  }
  
  /* Same as ovs_fatal() except that the arguments are supplied as a va_list. */
  void
  ovs_fatal_valist(int err_no, const char *format, va_list args)
  {
      ovs_error_valist(err_no, format, args);
      exit(EXIT_FAILURE);
  }
  
  /* Prints 'format' on stderr, formatting it like printf() does.  If 'err_no' is
   * nonzero, then it is formatted with ovs_retval_to_string() and appended to
   * the message inside parentheses.
   *
   * 'format' should not end with a new-line, because this function will add one
   * itself. */
  void
  ovs_error(int err_no, const char *format, ...)
  {
      va_list args;
  
      va_start(args, format);
      ovs_error_valist(err_no, format, args);
      va_end(args);
  }
  
  /* Same as ovs_error() except that the arguments are supplied as a va_list. */
  void
  ovs_error_valist(int err_no, const char *format, va_list args)
  {
      const char *subprogram_name = get_subprogram_name();
      int save_errno = errno;
  
      if (subprogram_name[0]) {
          fprintf(stderr, "%s(%s): ", program_name, subprogram_name);
      } else {
          fprintf(stderr, "%s: ", program_name);
      }
  
      vfprintf(stderr, format, args);
      if (err_no != 0) {
          fprintf(stderr, " (%s)", ovs_retval_to_string(err_no));
      }
      putc('\n', stderr);
  
      errno = save_errno;
  }
  
  /* Many OVS functions return an int which is one of:
   * - 0: no error yet
   * - >0: errno value
   * - EOF: end of file (not necessarily an error; depends on the function called)
   *
   * Returns the appropriate human-readable string. The caller must copy the
   * string if it wants to hold onto it, as the storage may be overwritten on
   * subsequent function calls.
   */
  const char *
  ovs_retval_to_string(int retval)
  {
      return (!retval ? ""
              : retval == EOF ? "End of file"
              : ovs_strerror(retval));
  }
  
  /* This function returns the string describing the error number in 'error'
   * for POSIX platforms.  For Windows, this function can be used for C library
   * calls.  For socket calls that are also used in Windows, use sock_strerror()
   * instead.  For WINAPI calls, look at ovs_lasterror_to_string(). */
  const char *
  ovs_strerror(int error)
  {
      enum { BUFSIZE = sizeof strerror_buffer_get()->s };
      int save_errno;
      char *buffer;
      char *s;
  
      save_errno = errno;
      buffer = strerror_buffer_get()->s;
  
  #if STRERROR_R_CHAR_P
      /* GNU style strerror_r() might return an immutable static string, or it
       * might write and return 'buffer', but in either case we can pass the
       * returned string directly to the caller. */
      s = strerror_r(error, buffer, BUFSIZE);
  #else  /* strerror_r() returns an int. */
      s = buffer;
      if (strerror_r(error, buffer, BUFSIZE)) {
          /* strerror_r() is only allowed to fail on ERANGE (because the buffer
           * is too short).  We don't check the actual failure reason because
           * POSIX requires strerror_r() to return the error but old glibc
           * (before 2.13) returns -1 and sets errno. */
          snprintf(buffer, BUFSIZE, "Unknown error %d", error);
      }
  #endif
  
      errno = save_errno;
  
      return s;
  }
  
  /* Sets global "program_name" and "program_version" variables.  Should
   * be called at the beginning of main() with "argv[0]" as the argument
   * to 'argv0'.
   *
   * 'version' should contain the version of the caller's program.  If 'version'
   * is the same as the VERSION #define, the caller is assumed to be part of Open
   * vSwitch.  Otherwise, it is assumed to be an external program linking against
   * the Open vSwitch libraries.
   *
   * The 'date' and 'time' arguments should likely be called with
   * "__DATE__" and "__TIME__" to use the time the binary was built.
   * Alternatively, the "set_program_name" macro may be called to do this
   * automatically.
   */
  void
  set_program_name__(const char *argv0, const char *version, const char *date,
                     const char *time)
  {
      char *basename;
  #ifdef _WIN32
      size_t max_len = strlen(argv0) + 1;
  
      SetErrorMode(GetErrorMode() | SEM_NOGPFAULTERRORBOX);
      _set_output_format(_TWO_DIGIT_EXPONENT);
  
      basename = xmalloc(max_len);
      _splitpath_s(argv0, NULL, 0, NULL, 0, basename, max_len, NULL, 0);
  #else
      const char *slash = strrchr(argv0, '/');
      basename = xstrdup(slash ? slash + 1 : argv0);
  #endif
  
      assert_single_threaded();
      free(program_name);
      program_name = basename;
      free(program_version);
  
      if (!strcmp(version, VERSION)) {
          program_version = xasprintf("%s (Open vSwitch) "VERSION"\n"
                                      "Compiled %s %s\n",
                                      program_name, date, time);
      } else {
          program_version = xasprintf("%s %s\n"
                                      "Open vSwitch Library "VERSION"\n"
                                      "Compiled %s %s\n",
                                      program_name, version, date, time);
      }
  }
  
  /* Returns the name of the currently running thread or process. */
  const char *
  get_subprogram_name(void)
  {
      const char *name = subprogram_name_get();
      return name ? name : "";
  }
  
  /* Sets the formatted value of 'format' as the name of the currently running
   * thread or process.  (This appears in log messages and may also be visible in
   * system process listings and debuggers.) */
  void
  set_subprogram_name(const char *format, ...)
  {
      char *pname;
  
      if (format) {
          va_list args;
  
          va_start(args, format);
          pname = xvasprintf(format, args);
          va_end(args);
      } else {
          pname = xstrdup(program_name);
      }
  
      free(subprogram_name_set(pname));
  
  #if HAVE_GLIBC_PTHREAD_SETNAME_NP
      pthread_setname_np(pthread_self(), pname);
  #elif HAVE_NETBSD_PTHREAD_SETNAME_NP
      pthread_setname_np(pthread_self(), "%s", pname);
  #elif HAVE_PTHREAD_SET_NAME_NP
      pthread_set_name_np(pthread_self(), pname);
  #endif
  }
  
  /* Returns a pointer to a string describing the program version.  The
   * caller must not modify or free the returned string.
   */
  const char *
  get_program_version(void)
  {
      return program_version;
  }
  
  /* Print the version information for the program.  */
  void
  ovs_print_version(uint8_t min_ofp, uint8_t max_ofp)
  {
      printf("%s", program_version);
      if (min_ofp || max_ofp) {
          printf("OpenFlow versions %#x:%#x\n", min_ofp, max_ofp);
      }
  }
  
  /* Writes the 'size' bytes in 'buf' to 'stream' as hex bytes arranged 16 per
   * line.  Numeric offsets are also included, starting at 'ofs' for the first
   * byte in 'buf'.  If 'ascii' is true then the corresponding ASCII characters
   * are also rendered alongside. */
  void
  ovs_hex_dump(FILE *stream, const void *buf_, size_t size,
               uintptr_t ofs, bool ascii)
  {
    const uint8_t *buf = buf_;
    const size_t per_line = 16; /* Maximum bytes per line. */
  
    while (size > 0)
      {
        size_t start, end, n;
        size_t i;
  
        /* Number of bytes on this line. */
        start = ofs % per_line;
        end = per_line;
        if (end - start > size)
          end = start + size;
        n = end - start;
  
        /* Print line. */
        fprintf(stream, "%08"PRIxMAX"  ", (uintmax_t) ROUND_DOWN(ofs, per_line));
        for (i = 0; i < start; i++)
          fprintf(stream, "   ");
        for (; i < end; i++)
          fprintf(stream, "%02x%c",
                  buf[i - start], i == per_line / 2 - 1? '-' : ' ');
        if (ascii)
          {
            for (; i < per_line; i++)
              fprintf(stream, "   ");
            fprintf(stream, "|");
            for (i = 0; i < start; i++)
              fprintf(stream, " ");
            for (; i < end; i++) {
                int c = buf[i - start];
                putc(c >= 32 && c < 127 ? c : '.', stream);
            }
            for (; i < per_line; i++)
              fprintf(stream, " ");
            fprintf(stream, "|");
          }
        fprintf(stream, "\n");
  
        ofs += n;
        buf += n;
        size -= n;
      }
  }
  
  bool
  str_to_int(const char *s, int base, int *i)
  {
      long long ll;
      bool ok = str_to_llong(s, base, &ll);
      *i = ll;
      return ok;
  }
  
  bool
  str_to_long(const char *s, int base, long *li)
  {
      long long ll;
      bool ok = str_to_llong(s, base, &ll);
      *li = ll;
      return ok;
  }
  
  bool
  str_to_llong(const char *s, int base, long long *x)
  {
      int save_errno = errno;
      char *tail;
      errno = 0;
      *x = strtoll(s, &tail, base);
      if (errno == EINVAL || errno == ERANGE || tail == s || *tail != '\0') {
          errno = save_errno;
          *x = 0;
          return false;
      } else {
          errno = save_errno;
          return true;
      }
  }
  
  bool
  str_to_uint(const char *s, int base, unsigned int *u)
  {
      long long ll;
      bool ok = str_to_llong(s, base, &ll);
      if (!ok || ll < 0 || ll > UINT_MAX) {
  	*u = 0;
  	return false;
      } else {
  	*u = ll;
  	return true;
      }
  }
  
  /* Converts floating-point string 's' into a double.  If successful, stores
   * the double in '*d' and returns true; on failure, stores 0 in '*d' and
   * returns false.
   *
   * Underflow (e.g. "1e-9999") is not considered an error, but overflow
   * (e.g. "1e9999)" is. */
  bool
  str_to_double(const char *s, double *d)
  {
      int save_errno = errno;
      char *tail;
      errno = 0;
      *d = strtod(s, &tail);
      if (errno == EINVAL || (errno == ERANGE && *d != 0)
          || tail == s || *tail != '\0') {
          errno = save_errno;
          *d = 0;
          return false;
      } else {
          errno = save_errno;
          return true;
      }
  }
  
  /* Returns the value of 'c' as a hexadecimal digit. */
  int
  hexit_value(int c)
  {
      switch (c) {
      case '0': case '1': case '2': case '3': case '4':
      case '5': case '6': case '7': case '8': case '9':
          return c - '0';
  
      case 'a': case 'A':
          return 0xa;
  
      case 'b': case 'B':
          return 0xb;
  
      case 'c': case 'C':
          return 0xc;
  
      case 'd': case 'D':
          return 0xd;
  
      case 'e': case 'E':
          return 0xe;
  
      case 'f': case 'F':
          return 0xf;
  
      default:
          return -1;
      }
  }
  
  /* Returns the integer value of the 'n' hexadecimal digits starting at 's', or
   * UINT_MAX if one of those "digits" is not really a hex digit.  If 'ok' is
   * nonnull, '*ok' is set to true if the conversion succeeds or to false if a
   * non-hex digit is detected. */
  unsigned int
  hexits_value(const char *s, size_t n, bool *ok)
  {
      unsigned int value;
      size_t i;
  
      value = 0;
      for (i = 0; i < n; i++) {
          int hexit = hexit_value(s[i]);
          if (hexit < 0) {
              if (ok) {
                  *ok = false;
              }
              return UINT_MAX;
          }
          value = (value << 4) + hexit;
      }
      if (ok) {
          *ok = true;
      }
      return value;
  }
  
  /* Returns the current working directory as a malloc()'d string, or a null
   * pointer if the current working directory cannot be determined. */
  char *
  get_cwd(void)
  {
      long int path_max;
      size_t size;
  
      /* Get maximum path length or at least a reasonable estimate. */
  #ifndef _WIN32
      path_max = pathconf(".", _PC_PATH_MAX);
  #else
      path_max = MAX_PATH;
  #endif
      size = (path_max < 0 ? 1024
              : path_max > 10240 ? 10240
              : path_max);
  
      /* Get current working directory. */
      for (;;) {
          char *buf = xmalloc(size);
          if (getcwd(buf, size)) {
              return xrealloc(buf, strlen(buf) + 1);
          } else {
              int error = errno;
              free(buf);
              if (error != ERANGE) {
                  VLOG_WARN("getcwd failed (%s)", ovs_strerror(error));
                  return NULL;
              }
              size *= 2;
          }
      }
  }
  
  static char *
  all_slashes_name(const char *s)
  {
      return xstrdup(s[0] == '/' && s[1] == '/' && s[2] != '/' ? "//"
                     : s[0] == '/' ? "/"
                     : ".");
  }
  
  #ifndef _WIN32
  /* Returns the directory name portion of 'file_name' as a malloc()'d string,
   * similar to the POSIX dirname() function but thread-safe. */
  char *
  dir_name(const char *file_name)
  {
      size_t len = strlen(file_name);
      while (len > 0 && file_name[len - 1] == '/') {
          len--;
      }
      while (len > 0 && file_name[len - 1] != '/') {
          len--;
      }
      while (len > 0 && file_name[len - 1] == '/') {
          len--;
      }
      return len ? xmemdup0(file_name, len) : all_slashes_name(file_name);
  }
  
  /* Returns the file name portion of 'file_name' as a malloc()'d string,
   * similar to the POSIX basename() function but thread-safe. */
  char *
  base_name(const char *file_name)
  {
      size_t end, start;
  
      end = strlen(file_name);
      while (end > 0 && file_name[end - 1] == '/') {
          end--;
      }
  
      if (!end) {
          return all_slashes_name(file_name);
      }
  
      start = end;
      while (start > 0 && file_name[start - 1] != '/') {
          start--;
      }
  
      return xmemdup0(file_name + start, end - start);
  }
  #endif /* _WIN32 */
  
  /* If 'file_name' starts with '/', returns a copy of 'file_name'.  Otherwise,
   * returns an absolute path to 'file_name' considering it relative to 'dir',
   * which itself must be absolute.  'dir' may be null or the empty string, in
   * which case the current working directory is used.
   *
   * Returns a null pointer if 'dir' is null and getcwd() fails. */
  char *
  abs_file_name(const char *dir, const char *file_name)
  {
      if (file_name[0] == '/') {
          return xstrdup(file_name);
      } else if (dir && dir[0]) {
          char *separator = dir[strlen(dir) - 1] == '/' ? "" : "/";
          return xasprintf("%s%s%s", dir, separator, file_name);
      } else {
          char *cwd = get_cwd();
          if (cwd) {
              char *abs_name = xasprintf("%s/%s", cwd, file_name);
              free(cwd);
              return abs_name;
          } else {
              return NULL;
          }
      }
  }
  
  /* Like readlink(), but returns the link name as a null-terminated string in
   * allocated memory that the caller must eventually free (with free()).
   * Returns NULL on error, in which case errno is set appropriately. */
  static char *
  xreadlink(const char *filename)
  {
      size_t size;
  
      for (size = 64; ; size *= 2) {
          char *buf = xmalloc(size);
          ssize_t retval = readlink(filename, buf, size);
          int error = errno;
  
          if (retval >= 0 && retval < size) {
              buf[retval] = '\0';
              return buf;
          }
  
          free(buf);
          if (retval < 0) {
              errno = error;
              return NULL;
          }
      }
  }
  
  /* Returns a version of 'filename' with symlinks in the final component
   * dereferenced.  This differs from realpath() in that:
   *
   *     - 'filename' need not exist.
   *
   *     - If 'filename' does exist as a symlink, its referent need not exist.
   *
   *     - Only symlinks in the final component of 'filename' are dereferenced.
   *
   * For Windows platform, this function returns a string that has the same
   * value as the passed string.
   *
   * The caller must eventually free the returned string (with free()). */
  char *
  follow_symlinks(const char *filename)
  {
  #ifndef _WIN32
      struct stat s;
      char *fn;
      int i;
  
      fn = xstrdup(filename);
      for (i = 0; i < 10; i++) {
          char *linkname;
          char *next_fn;
  
          if (lstat(fn, &s) != 0 || !S_ISLNK(s.st_mode)) {
              return fn;
          }
  
          linkname = xreadlink(fn);
          if (!linkname) {
              VLOG_WARN("%s: readlink failed (%s)",
                        filename, ovs_strerror(errno));
              return fn;
          }
  
          if (linkname[0] == '/') {
              /* Target of symlink is absolute so use it raw. */
              next_fn = linkname;
          } else {
              /* Target of symlink is relative so add to 'fn''s directory. */
              char *dir = dir_name(fn);
  
              if (!strcmp(dir, ".")) {
                  next_fn = linkname;
              } else {
                  char *separator = dir[strlen(dir) - 1] == '/' ? "" : "/";
                  next_fn = xasprintf("%s%s%s", dir, separator, linkname);
                  free(linkname);
              }
  
              free(dir);
          }
  
          free(fn);
          fn = next_fn;
      }
  
      VLOG_WARN("%s: too many levels of symlinks", filename);
      free(fn);
  #endif
      return xstrdup(filename);
  }
  
  /* Pass a value to this function if it is marked with
   * __attribute__((warn_unused_result)) and you genuinely want to ignore
   * its return value.  (Note that every scalar type can be implicitly
   * converted to bool.) */
  void ignore(bool x OVS_UNUSED) { }
  
  /* Returns an appropriate delimiter for inserting just before the 0-based item
   * 'index' in a list that has 'total' items in it. */
  const char *
  english_list_delimiter(size_t index, size_t total)
  {
      return (index == 0 ? ""
              : index < total - 1 ? ", "
              : total > 2 ? ", and "
              : " and ");
  }
  
  /* Returns the number of trailing 0-bits in 'n'.  Undefined if 'n' == 0. */
  #if __GNUC__ >= 4
  /* Defined inline in util.h. */
  #else
  /* Returns the number of trailing 0-bits in 'n'.  Undefined if 'n' == 0. */
  int
  raw_ctz(uint64_t n)
  {
      uint64_t k;
      int count = 63;
  
  #define CTZ_STEP(X)                             \
      k = n << (X);                               \
      if (k) {                                    \
          count -= X;                             \
          n = k;                                  \
      }
      CTZ_STEP(32);
      CTZ_STEP(16);
      CTZ_STEP(8);
      CTZ_STEP(4);
      CTZ_STEP(2);
      CTZ_STEP(1);
  #undef CTZ_STEP
  
      return count;
  }
  
  /* Returns the number of leading 0-bits in 'n'.  Undefined if 'n' == 0. */
  int
  raw_clz64(uint64_t n)
  {
      uint64_t k;
      int count = 63;
  
  #define CLZ_STEP(X)                             \
      k = n >> (X);                               \
      if (k) {                                    \
          count -= X;                             \
          n = k;                                  \
      }
      CLZ_STEP(32);
      CLZ_STEP(16);
      CLZ_STEP(8);
      CLZ_STEP(4);
      CLZ_STEP(2);
      CLZ_STEP(1);
  #undef CLZ_STEP
  
      return count;
  }
  #endif
  
  #if NEED_COUNT_1BITS_8
  #define INIT1(X)                                \
      ((((X) & (1 << 0)) != 0) +                  \
       (((X) & (1 << 1)) != 0) +                  \
       (((X) & (1 << 2)) != 0) +                  \
       (((X) & (1 << 3)) != 0) +                  \
       (((X) & (1 << 4)) != 0) +                  \
       (((X) & (1 << 5)) != 0) +                  \
       (((X) & (1 << 6)) != 0) +                  \
       (((X) & (1 << 7)) != 0))
  #define INIT2(X)   INIT1(X),  INIT1((X) +  1)
  #define INIT4(X)   INIT2(X),  INIT2((X) +  2)
  #define INIT8(X)   INIT4(X),  INIT4((X) +  4)
  #define INIT16(X)  INIT8(X),  INIT8((X) +  8)
  #define INIT32(X) INIT16(X), INIT16((X) + 16)
  #define INIT64(X) INIT32(X), INIT32((X) + 32)
  
  const uint8_t count_1bits_8[256] = {
      INIT64(0), INIT64(64), INIT64(128), INIT64(192)
  };
  #endif
  
  /* Returns true if the 'n' bytes starting at 'p' are zeros. */
  bool
  is_all_zeros(const uint8_t *p, size_t n)
  {
      size_t i;
  
      for (i = 0; i < n; i++) {
          if (p[i] != 0x00) {
              return false;
          }
      }
      return true;
  }
  
  /* Returns true if the 'n' bytes starting at 'p' are 0xff. */
  bool
  is_all_ones(const uint8_t *p, size_t n)
  {
      size_t i;
  
      for (i = 0; i < n; i++) {
          if (p[i] != 0xff) {
              return false;
          }
      }
      return true;
  }
  
  /* Copies 'n_bits' bits starting from bit 'src_ofs' in 'src' to the 'n_bits'
   * starting from bit 'dst_ofs' in 'dst'.  'src' is 'src_len' bytes long and
   * 'dst' is 'dst_len' bytes long.
   *
   * If you consider all of 'src' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in src[src_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in src[src_len -
   * 2], and so on.  Similarly for 'dst'.
   *
   * Required invariants:
   *   src_ofs + n_bits <= src_len * 8
   *   dst_ofs + n_bits <= dst_len * 8
   *   'src' and 'dst' must not overlap.
   */
  void
  bitwise_copy(const void *src_, unsigned int src_len, unsigned int src_ofs,
               void *dst_, unsigned int dst_len, unsigned int dst_ofs,
               unsigned int n_bits)
  {
      const uint8_t *src = src_;
      uint8_t *dst = dst_;
  
      src += src_len - (src_ofs / 8 + 1);
      src_ofs %= 8;
  
      dst += dst_len - (dst_ofs / 8 + 1);
      dst_ofs %= 8;
  
      if (src_ofs == 0 && dst_ofs == 0) {
          unsigned int n_bytes = n_bits / 8;
          if (n_bytes) {
              dst -= n_bytes - 1;
              src -= n_bytes - 1;
              memcpy(dst, src, n_bytes);
  
              n_bits %= 8;
              src--;
              dst--;
          }
          if (n_bits) {
              uint8_t mask = (1 << n_bits) - 1;
              *dst = (*dst & ~mask) | (*src & mask);
          }
      } else {
          while (n_bits > 0) {
              unsigned int max_copy = 8 - MAX(src_ofs, dst_ofs);
              unsigned int chunk = MIN(n_bits, max_copy);
              uint8_t mask = ((1 << chunk) - 1) << dst_ofs;
  
              *dst &= ~mask;
              *dst |= ((*src >> src_ofs) << dst_ofs) & mask;
  
              src_ofs += chunk;
              if (src_ofs == 8) {
                  src--;
                  src_ofs = 0;
              }
              dst_ofs += chunk;
              if (dst_ofs == 8) {
                  dst--;
                  dst_ofs = 0;
              }
              n_bits -= chunk;
          }
      }
  }
  
  /* Zeros the 'n_bits' bits starting from bit 'dst_ofs' in 'dst'.  'dst' is
   * 'dst_len' bytes long.
   *
   * If you consider all of 'dst' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
   * 2], and so on.
   *
   * Required invariant:
   *   dst_ofs + n_bits <= dst_len * 8
   */
  void
  bitwise_zero(void *dst_, unsigned int dst_len, unsigned dst_ofs,
               unsigned int n_bits)
  {
      uint8_t *dst = dst_;
  
      if (!n_bits) {
          return;
      }
  
      dst += dst_len - (dst_ofs / 8 + 1);
      dst_ofs %= 8;
  
      if (dst_ofs) {
          unsigned int chunk = MIN(n_bits, 8 - dst_ofs);
  
          *dst &= ~(((1 << chunk) - 1) << dst_ofs);
  
          n_bits -= chunk;
          if (!n_bits) {
              return;
          }
  
          dst--;
      }
  
      while (n_bits >= 8) {
          *dst-- = 0;
          n_bits -= 8;
      }
  
      if (n_bits) {
          *dst &= ~((1 << n_bits) - 1);
      }
  }
  
  /* Sets to 1 all of the 'n_bits' bits starting from bit 'dst_ofs' in 'dst'.
   * 'dst' is 'dst_len' bytes long.
   *
   * If you consider all of 'dst' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
   * 2], and so on.
   *
   * Required invariant:
   *   dst_ofs + n_bits <= dst_len * 8
   */
  void
  bitwise_one(void *dst_, unsigned int dst_len, unsigned dst_ofs,
              unsigned int n_bits)
  {
      uint8_t *dst = dst_;
  
      if (!n_bits) {
          return;
      }
  
      dst += dst_len - (dst_ofs / 8 + 1);
      dst_ofs %= 8;
  
      if (dst_ofs) {
          unsigned int chunk = MIN(n_bits, 8 - dst_ofs);
  
          *dst |= ((1 << chunk) - 1) << dst_ofs;
  
          n_bits -= chunk;
          if (!n_bits) {
              return;
          }
  
          dst--;
      }
  
      while (n_bits >= 8) {
          *dst-- = 0xff;
          n_bits -= 8;
      }
  
      if (n_bits) {
          *dst |= (1 << n_bits) - 1;
      }
  }
  
  /* Scans the 'n_bits' bits starting from bit 'dst_ofs' in 'dst' for 1-bits.
   * Returns false if any 1-bits are found, otherwise true.  'dst' is 'dst_len'
   * bytes long.
   *
   * If you consider all of 'dst' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
   * 2], and so on.
   *
   * Required invariant:
   *   dst_ofs + n_bits <= dst_len * 8
   */
  bool
  bitwise_is_all_zeros(const void *p_, unsigned int len, unsigned int ofs,
                       unsigned int n_bits)
  {
      const uint8_t *p = p_;
  
      if (!n_bits) {
          return true;
      }
  
      p += len - (ofs / 8 + 1);
      ofs %= 8;
  
      if (ofs) {
          unsigned int chunk = MIN(n_bits, 8 - ofs);
  
          if (*p & (((1 << chunk) - 1) << ofs)) {
              return false;
          }
  
          n_bits -= chunk;
          if (!n_bits) {
              return true;
          }
  
          p--;
      }
  
      while (n_bits >= 8) {
          if (*p) {
              return false;
          }
          n_bits -= 8;
          p--;
      }
  
      if (n_bits && *p & ((1 << n_bits) - 1)) {
          return false;
      }
  
      return true;
  }
  
  /* Copies the 'n_bits' low-order bits of 'value' into the 'n_bits' bits
   * starting at bit 'dst_ofs' in 'dst', which is 'dst_len' bytes long.
   *
   * If you consider all of 'dst' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
   * 2], and so on.
   *
   * Required invariants:
   *   dst_ofs + n_bits <= dst_len * 8
   *   n_bits <= 64
   */
  void
  bitwise_put(uint64_t value,
              void *dst, unsigned int dst_len, unsigned int dst_ofs,
              unsigned int n_bits)
  {
      ovs_be64 n_value = htonll(value);
      bitwise_copy(&n_value, sizeof n_value, 0,
                   dst, dst_len, dst_ofs,
                   n_bits);
  }
  
  /* Returns the value of the 'n_bits' bits starting at bit 'src_ofs' in 'src',
   * which is 'src_len' bytes long.
   *
   * If you consider all of 'src' to be a single unsigned integer in network byte
   * order, then bit N is the bit with value 2**N.  That is, bit 0 is the bit
   * with value 1 in src[src_len - 1], bit 1 is the bit with value 2, bit 2 is
   * the bit with value 4, ..., bit 8 is the bit with value 1 in src[src_len -
   * 2], and so on.
   *
   * Required invariants:
   *   src_ofs + n_bits <= src_len * 8
   *   n_bits <= 64
   */
  uint64_t
  bitwise_get(const void *src, unsigned int src_len,
              unsigned int src_ofs, unsigned int n_bits)
  {
      ovs_be64 value = htonll(0);
  
      bitwise_copy(src, src_len, src_ofs,
                   &value, sizeof value, 0,
                   n_bits);
      return ntohll(value);
  }
  
  /* ovs_scan */
  
  struct scan_spec {
      unsigned int width;
      enum {
          SCAN_DISCARD,
          SCAN_CHAR,
          SCAN_SHORT,
          SCAN_INT,
          SCAN_LONG,
          SCAN_LLONG,
          SCAN_INTMAX_T,
          SCAN_PTRDIFF_T,
          SCAN_SIZE_T
      } type;
  };
  
  static const char *
  skip_spaces(const char *s)
  {
      while (isspace((unsigned char) *s)) {
          s++;
      }
      return s;
  }
  
  static const char *
  scan_int(const char *s, const struct scan_spec *spec, int base, va_list *args)
  {
      const char *start = s;
      uintmax_t value;
      bool negative;
      int n_digits;
  
      negative = *s == '-';
      s += *s == '-' || *s == '+';
  
      if ((!base || base == 16) && *s == '0' && (s[1] == 'x' || s[1] == 'X')) {
          base = 16;
          s += 2;
      } else if (!base) {
          base = *s == '0' ? 8 : 10;
      }
  
      if (s - start >= spec->width) {
          return NULL;
      }
  
      value = 0;
      n_digits = 0;
      while (s - start < spec->width) {
          int digit = hexit_value(*s);
  
          if (digit < 0 || digit >= base) {
              break;
          }
          value = value * base + digit;
          n_digits++;
          s++;
      }
      if (!n_digits) {
          return NULL;
      }
  
      if (negative) {
          value = -value;
      }
  
      switch (spec->type) {
      case SCAN_DISCARD:
          break;
      case SCAN_CHAR:
          *va_arg(*args, char *) = value;
          break;
      case SCAN_SHORT:
          *va_arg(*args, short int *) = value;
          break;
      case SCAN_INT:
          *va_arg(*args, int *) = value;
          break;
      case SCAN_LONG:
          *va_arg(*args, long int *) = value;
          break;
      case SCAN_LLONG:
          *va_arg(*args, long long int *) = value;
          break;
      case SCAN_INTMAX_T:
          *va_arg(*args, intmax_t *) = value;
          break;
      case SCAN_PTRDIFF_T:
          *va_arg(*args, ptrdiff_t *) = value;
          break;
      case SCAN_SIZE_T:
          *va_arg(*args, size_t *) = value;
          break;
      }
      return s;
  }
  
  static const char *
  skip_digits(const char *s)
  {
      while (*s >= '0' && *s <= '9') {
          s++;
      }
      return s;
  }
  
  static const char *
  scan_float(const char *s, const struct scan_spec *spec, va_list *args)
  {
      const char *start = s;
      long double value;
      char *tail;
      char *copy;
      bool ok;
  
      s += *s == '+' || *s == '-';
      s = skip_digits(s);
      if (*s == '.') {
          s = skip_digits(s + 1);
      }
      if (*s == 'e' || *s == 'E') {
          s++;
          s += *s == '+' || *s == '-';
          s = skip_digits(s);
      }
  
      if (s - start > spec->width) {
          s = start + spec->width;
      }
  
      copy = xmemdup0(start, s - start);
      value = strtold(copy, &tail);
      ok = *tail == '\0';
      free(copy);
      if (!ok) {
          return NULL;
      }
  
      switch (spec->type) {
      case SCAN_DISCARD:
          break;
      case SCAN_INT:
          *va_arg(*args, float *) = value;
          break;
      case SCAN_LONG:
          *va_arg(*args, double *) = value;
          break;
      case SCAN_LLONG:
          *va_arg(*args, long double *) = value;
          break;
  
      case SCAN_CHAR:
      case SCAN_SHORT:
      case SCAN_INTMAX_T:
      case SCAN_PTRDIFF_T:
      case SCAN_SIZE_T:
          OVS_NOT_REACHED();
      }
      return s;
  }
  
  static void
  scan_output_string(const struct scan_spec *spec,
                     const char *s, size_t n,
                     va_list *args)
  {
      if (spec->type != SCAN_DISCARD) {
          char *out = va_arg(*args, char *);
          memcpy(out, s, n);
          out[n] = '\0';
      }
  }
  
  static const char *
  scan_string(const char *s, const struct scan_spec *spec, va_list *args)
  {
      size_t n;
  
      for (n = 0; n < spec->width; n++) {
          if (!s[n] || isspace((unsigned char) s[n])) {
              break;
          }
      }
      if (!n) {
          return NULL;
      }
  
      scan_output_string(spec, s, n, args);
      return s + n;
  }
  
  static const char *
  parse_scanset(const char *p_, unsigned long *set, bool *complemented)
  {
      const uint8_t *p = (const uint8_t *) p_;
  
      *complemented = *p == '^';
      p += *complemented;
  
      if (*p == ']') {
          bitmap_set1(set, ']');
          p++;
      }
  
      while (*p && *p != ']') {
          if (p[1] == '-' && p[2] != ']' && p[2] > *p) {
              bitmap_set_multiple(set, *p, p[2] - *p + 1, true);
              p += 3;
          } else {
              bitmap_set1(set, *p++);
          }
      }
      if (*p == ']') {
          p++;
      }
      return (const char *) p;
  }
  
  static const char *
  scan_set(const char *s, const struct scan_spec *spec, const char **pp,
           va_list *args)
  {
      unsigned long set[BITMAP_N_LONGS(UCHAR_MAX + 1)];
      bool complemented;
      unsigned int n;
  
      /* Parse the scan set. */
      memset(set, 0, sizeof set);
      *pp = parse_scanset(*pp, set, &complemented);
  
      /* Parse the data. */
      n = 0;
      while (s[n]
             && bitmap_is_set(set, (unsigned char) s[n]) == !complemented
             && n < spec->width) {
          n++;
      }
      if (!n) {
          return NULL;
      }
      scan_output_string(spec, s, n, args);
      return s + n;
  }
  
  static const char *
  scan_chars(const char *s, const struct scan_spec *spec, va_list *args)
  {
      unsigned int n = spec->width == UINT_MAX ? 1 : spec->width;
  
      if (strlen(s) < n) {
          return NULL;
      }
      if (spec->type != SCAN_DISCARD) {
          memcpy(va_arg(*args, char *), s, n);
      }
      return s + n;
  }
  
  /* This is an implementation of the standard sscanf() function, with the
   * following exceptions:
   *
   *   - It returns true if the entire format was successfully scanned and
   *     converted, false if any conversion failed.
   *
   *   - The standard doesn't define sscanf() behavior when an out-of-range value
   *     is scanned, e.g. if a "%"PRIi8 conversion scans "-1" or "0x1ff".  Some
   *     implementations consider this an error and stop scanning.  This
   *     implementation never considers an out-of-range value an error; instead,
   *     it stores the least-significant bits of the converted value in the
   *     destination, e.g. the value 255 for both examples earlier.
   *
   *   - Only single-byte characters are supported, that is, the 'l' modifier
   *     on %s, %[, and %c is not supported.  The GNU extension 'a' modifier is
   *     also not supported.
   *
   *   - %p is not supported.
   */
  bool
  ovs_scan(const char *s, const char *format, ...)
  {
      const char *const start = s;
      bool ok = false;
      const char *p;
      va_list args;
  
      va_start(args, format);
      p = format;
      while (*p != '\0') {
          struct scan_spec spec;
          unsigned char c = *p++;
          bool discard;
  
          if (isspace(c)) {
              s = skip_spaces(s);
              continue;
          } else if (c != '%') {
              if (*s != c) {
                  goto exit;
              }
              s++;
              continue;
          } else if (*p == '%') {
              if (*s++ != '%') {
                  goto exit;
              }
              p++;
              continue;
          }
  
          /* Parse '*' flag. */
          discard = *p == '*';
          p += discard;
  
          /* Parse field width. */
          spec.width = 0;
          while (*p >= '0' && *p <= '9') {
              spec.width = spec.width * 10 + (*p++ - '0');
          }
          if (spec.width == 0) {
              spec.width = UINT_MAX;
          }
  
          /* Parse type modifier. */
          switch (*p) {
          case 'h':
              if (p[1] == 'h') {
                  spec.type = SCAN_CHAR;
                  p += 2;
              } else {
                  spec.type = SCAN_SHORT;
                  p++;
              }
              break;
  
          case 'j':
              spec.type = SCAN_INTMAX_T;
              p++;
              break;
  
          case 'l':
              if (p[1] == 'l') {
                  spec.type = SCAN_LLONG;
                  p += 2;
              } else {
                  spec.type = SCAN_LONG;
                  p++;
              }
              break;
  
          case 'L':
          case 'q':
              spec.type = SCAN_LLONG;
              p++;
              break;
  
          case 't':
              spec.type = SCAN_PTRDIFF_T;
              p++;
              break;
  
          case 'z':
              spec.type = SCAN_SIZE_T;
              p++;
              break;
  
          default:
              spec.type = SCAN_INT;
              break;
          }
  
          if (discard) {
              spec.type = SCAN_DISCARD;
          }
  
          c = *p++;
          if (c != 'c' && c != 'n' && c != '[') {
              s = skip_spaces(s);
          }
          switch (c) {
          case 'd':
              s = scan_int(s, &spec, 10, &args);
              break;
  
          case 'i':
              s = scan_int(s, &spec, 0, &args);
              break;
  
          case 'o':
              s = scan_int(s, &spec, 8, &args);
              break;
  
          case 'u':
              s = scan_int(s, &spec, 10, &args);
              break;
  
          case 'x':
          case 'X':
              s = scan_int(s, &spec, 16, &args);
              break;
  
          case 'e':
          case 'f':
          case 'g':
          case 'E':
          case 'G':
              s = scan_float(s, &spec, &args);
              break;
  
          case 's':
              s = scan_string(s, &spec, &args);
              break;
  
          case '[':
              s = scan_set(s, &spec, &p, &args);
              break;
  
          case 'c':
              s = scan_chars(s, &spec, &args);
              break;
  
          case 'n':
              if (spec.type != SCAN_DISCARD) {
                  *va_arg(args, int *) = s - start;
              }
              break;
          }
  
          if (!s) {
              goto exit;
          }
      }
      ok = true;
  
  exit:
      va_end(args);
      return ok;
  }
  
  void
  xsleep(unsigned int seconds)
  {
      ovsrcu_quiesce_start();
  #ifdef _WIN32
      Sleep(seconds * 1000);
  #else
      sleep(seconds);
  #endif
      ovsrcu_quiesce_end();
  }
  
  #ifdef _WIN32
  
  char *
  ovs_format_message(int error)
  {
      enum { BUFSIZE = sizeof strerror_buffer_get()->s };
      char *buffer = strerror_buffer_get()->s;
  
      FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                    NULL, error, 0, buffer, BUFSIZE, NULL);
      return buffer;
  }
  
  /* Returns a null-terminated string that explains the last error.
   * Use this function to get the error string for WINAPI calls. */
  char *
  ovs_lasterror_to_string(void)
  {
      return ovs_format_message(GetLastError());
  }
  
  int
  ftruncate(int fd, off_t length)
  {
      int error;
  
      error = _chsize_s(fd, length);
      if (error) {
          return -1;
      }
      return 0;
  }
  
  OVS_CONSTRUCTOR(winsock_start) {
      WSADATA wsaData;
      int error;
  
      error = WSAStartup(MAKEWORD(2, 2), &wsaData);
      if (error != 0) {
          VLOG_FATAL("WSAStartup failed: %s", sock_strerror(sock_errno()));
     }
  }
  #endif
  