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gen_uuid.c

/*
 * gen_uuid.c --- generate a DCE-compatible uuid
 *
 * Copyright (C) 1996, 1997, 1998, 1999 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU 
 * Library General Public License.
 * %End-Header%
 */

/*
 * Force inclusion of SVID stuff since we need it if we're compiling in
 * gcc-wall wall mode
 */
#define _SVID_SOURCE

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#ifdef HAVE_SYS_SOCKIO_H
#include <sys/sockio.h>
#endif
#ifdef HAVE_NET_IF_H
#include <net/if.h>
#endif
#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

#include "uuidP.h"

#ifdef HAVE_SRANDOM
#define srand(x)  srandom(x)
#define rand()          random()
#endif

static int get_random_fd(void)
{
      struct timeval    tv;
      static int  fd = -2;
      int         i;

      if (fd == -2) {
            gettimeofday(&tv, 0);
            fd = open("/dev/urandom", O_RDONLY);
            if (fd == -1)
                  fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
            srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
      }
      /* Crank the random number generator a few times */
      gettimeofday(&tv, 0);
      for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
            rand();
      return fd;
}


/*
 * Generate a series of random bytes.  Use /dev/urandom if possible,
 * and if not, use srandom/random.
 */
static void get_random_bytes(void *buf, int nbytes)
{
      int i, fd = get_random_fd();
      int lose_counter = 0;
      char *cp = (char *) buf;

      if (fd >= 0) {
            while (nbytes > 0) {
                  i = read(fd, cp, nbytes);
                  if ((i < 0) &&
                      ((errno == EINTR) || (errno == EAGAIN)))
                        continue;
                  if (i <= 0) {
                        if (lose_counter++ == 8)
                              break;
                        continue;
                  }
                  nbytes -= i;
                  cp += i;
                  lose_counter = 0;
            }
      }

      /* XXX put something better here if no /dev/random! */
      for (i = 0; i < nbytes; i++)
            *cp++ = rand() & 0xFF;
      return;
}

/*
 * Get the ethernet hardware address, if we can find it...
 */
static int get_node_id(unsigned char *node_id)
{
#ifdef HAVE_NET_IF_H
      int         sd;
      struct ifreq      ifr, *ifrp;
      struct ifconf     ifc;
      char buf[1024];
      int         n, i;
      unsigned char     *a;
      
/*
 * BSD 4.4 defines the size of an ifreq to be
 * max(sizeof(ifreq), sizeof(ifreq.ifr_name)+ifreq.ifr_addr.sa_len
 * However, under earlier systems, sa_len isn't present, so the size is 
 * just sizeof(struct ifreq)
 */
#ifdef HAVE_SA_LEN
#ifndef max
#define max(a,b) ((a) > (b) ? (a) : (b))
#endif
#define ifreq_size(i) max(sizeof(struct ifreq),\
     sizeof((i).ifr_name)+(i).ifr_addr.sa_len)
#else
#define ifreq_size(i) sizeof(struct ifreq)
#endif /* HAVE_SA_LEN*/

      sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
      if (sd < 0) {
            return -1;
      }
      memset(buf, 0, sizeof(buf));
      ifc.ifc_len = sizeof(buf);
      ifc.ifc_buf = buf;
      if (ioctl (sd, SIOCGIFCONF, (char *)&ifc) < 0) {
            close(sd);
            return -1;
      }
      n = ifc.ifc_len;
      for (i = 0; i < n; i+= ifreq_size(*ifr) ) {
            ifrp = (struct ifreq *)((char *) ifc.ifc_buf+i);
            strncpy(ifr.ifr_name, ifrp->ifr_name, IFNAMSIZ);
#ifdef SIOCGIFHWADDR
            if (ioctl(sd, SIOCGIFHWADDR, &ifr) < 0)
                  continue;
            a = (unsigned char *) &ifr.ifr_hwaddr.sa_data;
#else
#ifdef SIOCGENADDR
            if (ioctl(sd, SIOCGENADDR, &ifr) < 0)
                  continue;
            a = (unsigned char *) ifr.ifr_enaddr;
#else
            /*
             * XXX we don't have a way of getting the hardware
             * address
             */
            close(sd);
            return 0;
#endif /* SIOCGENADDR */
#endif /* SIOCGIFHWADDR */
            if (!a[0] && !a[1] && !a[2] && !a[3] && !a[4] && !a[5])
                  continue;
            if (node_id) {
                  memcpy(node_id, a, 6);
                  close(sd);
                  return 1;
            }
      }
      close(sd);
#endif
      return 0;
}

/* Assume that the gettimeofday() has microsecond granularity */
#define MAX_ADJUSTMENT 10

static int get_clock(__u32 *clock_high, __u32 *clock_low, __u16 *ret_clock_seq)
{
      static int              adjustment = 0;
      static struct timeval         last = {0, 0};
      static __u16                  clock_seq;
      struct timeval                tv;
      unsigned long long            clock_reg;
      
try_again:
      gettimeofday(&tv, 0);
      if ((last.tv_sec == 0) && (last.tv_usec == 0)) {
            get_random_bytes(&clock_seq, sizeof(clock_seq));
            clock_seq &= 0x1FFF;
            last = tv;
            last.tv_sec--;
      }
      if ((tv.tv_sec < last.tv_sec) ||
          ((tv.tv_sec == last.tv_sec) &&
           (tv.tv_usec < last.tv_usec))) {
            clock_seq = (clock_seq+1) & 0x1FFF;
            adjustment = 0;
            last = tv;
      } else if ((tv.tv_sec == last.tv_sec) &&
          (tv.tv_usec == last.tv_usec)) {
            if (adjustment >= MAX_ADJUSTMENT)
                  goto try_again;
            adjustment++;
      } else {
            adjustment = 0;
            last = tv;
      }
            
      clock_reg = tv.tv_usec*10 + adjustment;
      clock_reg += ((unsigned long long) tv.tv_sec)*10000000;
      clock_reg += (((unsigned long long) 0x01B21DD2) << 32) + 0x13814000;

      *clock_high = clock_reg >> 32;
      *clock_low = clock_reg;
      *ret_clock_seq = clock_seq;
      return 0;
}

void uuid_generate_time(uuid_t out)
{
      static unsigned char node_id[6];
      static int has_init = 0;
      struct uuid uu;
      __u32 clock_mid;

      if (!has_init) {
            if (get_node_id(node_id) <= 0) {
                  get_random_bytes(node_id, 6);
                  /*
                   * Set multicast bit, to prevent conflicts
                   * with IEEE 802 addresses obtained from
                   * network cards
                   */
                  node_id[0] |= 0x80;
            }
            has_init = 1;
      }
      get_clock(&clock_mid, &uu.time_low, &uu.clock_seq);
      uu.clock_seq |= 0x8000;
      uu.time_mid = (__u16) clock_mid;
      uu.time_hi_and_version = (clock_mid >> 16) | 0x1000;
      memcpy(uu.node, node_id, 6);
      uuid_pack(&uu, out);
}

void uuid_generate_random(uuid_t out)
{
      uuid_t      buf;
      struct uuid uu;

      get_random_bytes(buf, sizeof(buf));
      uuid_unpack(buf, &uu);

      uu.clock_seq = (uu.clock_seq & 0x3FFF) | 0x8000;
      uu.time_hi_and_version = (uu.time_hi_and_version & 0x0FFF) | 0x4000;
      uuid_pack(&uu, out);
}

/*
 * This is the generic front-end to uuid_generate_random and
 * uuid_generate_time.  It uses uuid_generate_random only if
 * /dev/urandom is available, since otherwise we won't have
 * high-quality randomness.
 */
void uuid_generate(uuid_t out)
{
      if (get_random_fd() >= 0)
            uuid_generate_random(out);
      else
            uuid_generate_time(out);
}

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