mod_load.c.in

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  count = sscanf (ldavgbuf, "%lf %lf %lf",
                  &load_ave[0], &load_ave[1], &load_ave[2]);
  if (count < 1)
    return -1;

  for (elem = 0; elem < nelem && elem < count; elem++)
    loadavg[elem] = load_ave[elem];

  return elem;

# endif /* __linux__ */

# if !defined (LDAV_DONE) && defined (__NetBSD__)
#  define LDAV_DONE
#  undef LOAD_AVE_TYPE

#  ifndef NETBSD_LDAV_FILE
#   define NETBSD_LDAV_FILE "/kern/loadavg"
#  endif

  unsigned long int load_ave[3], scale;
  int count;
  FILE *fp;

  fp = fopen (NETBSD_LDAV_FILE, "r");
  if (fp == NULL)
    return -1;
  count = fscanf (fp, "%lu %lu %lu %lu\n",
                  &load_ave[0], &load_ave[1], &load_ave[2],
                  &scale);
  (void) fclose (fp);
  if (count != 4)
    return -1;

  for (elem = 0; elem < nelem; elem++)
    loadavg[elem] = (double) load_ave[elem] / (double) scale;

  return elem;

# endif /* __NetBSD__ */

# if !defined (LDAV_DONE) && defined (NeXT)
#  define LDAV_DONE
  /* The NeXT code was adapted from iscreen 3.2.  */

  host_t host;
  struct processor_set_basic_info info;
  unsigned info_count;

  /* We only know how to get the 1-minute average for this system,
     so even if the caller asks for more than 1, we only return 1.  */

  if (!getloadavg_initialized)
    {
      if (processor_set_default (host_self (), &default_set) == KERN_SUCCESS)
        getloadavg_initialized = 1;
    }

  if (getloadavg_initialized)
    {
      info_count = PROCESSOR_SET_BASIC_INFO_COUNT;
      if (processor_set_info (default_set, PROCESSOR_SET_BASIC_INFO, &host,
                              (processor_set_info_t) &info, &info_count)
          != KERN_SUCCESS)
        getloadavg_initialized = 0;
      else
        {
          if (nelem > 0)
            loadavg[elem++] = (double) info.load_average / LOAD_SCALE;
        }
    }

  if (!getloadavg_initialized)
    return -1;
# endif /* NeXT */

# if !defined (LDAV_DONE) && defined (UMAX)
#  define LDAV_DONE
/* UMAX 4.2, which runs on the Encore Multimax multiprocessor, does not
   have a /dev/kmem.  Information about the workings of the running kernel
   can be gathered with inq_stats system calls.
   We only know how to get the 1-minute average for this system.  */

  struct proc_summary proc_sum_data;
  struct stat_descr proc_info;
  double load;
  register unsigned int i, j;

  if (cpus == 0)
    {
      register unsigned int c, i;
      struct cpu_config conf;
      struct stat_descr desc;

      desc.sd_next = 0;
      desc.sd_subsys = SUBSYS_CPU;
      desc.sd_type = CPUTYPE_CONFIG;
      desc.sd_addr = (char *) &conf;
      desc.sd_size = sizeof conf;

      if (inq_stats (1, &desc))
        return -1;

      c = 0;
      for (i = 0; i < conf.config_maxclass; ++i)
        {
          struct class_stats stats;
          bzero ((char *) &stats, sizeof stats);

          desc.sd_type = CPUTYPE_CLASS;
          desc.sd_objid = i;
          desc.sd_addr = (char *) &stats;
          desc.sd_size = sizeof stats;

          if (inq_stats (1, &desc))
            return -1;

          c += stats.class_numcpus;
        }
      cpus = c;
      samples = cpus < 2 ? 3 : (2 * cpus / 3);
    }

  proc_info.sd_next = 0;
  proc_info.sd_subsys = SUBSYS_PROC;
  proc_info.sd_type = PROCTYPE_SUMMARY;
  proc_info.sd_addr = (char *) &proc_sum_data;
  proc_info.sd_size = sizeof (struct proc_summary);
  proc_info.sd_sizeused = 0;

  if (inq_stats (1, &proc_info) != 0)
    return -1;

  load = proc_sum_data.ps_nrunnable;
  j = 0;
  for (i = samples - 1; i > 0; --i)
    {
      load += proc_sum_data.ps_nrun[j];
      if (j++ == PS_NRUNSIZE)
        j = 0;
    }

  if (nelem > 0)
    loadavg[elem++] = load / samples / cpus;
# endif /* UMAX */

# if !defined (LDAV_DONE) && defined (DGUX)
#  define LDAV_DONE
  /* This call can return -1 for an error, but with good args
     it's not supposed to fail.  The first argument is for no
     apparent reason of type `long int *'.  */
  dg_sys_info ((long int *) &load_info,
               DG_SYS_INFO_LOAD_INFO_TYPE,
               DG_SYS_INFO_LOAD_VERSION_0);

  if (nelem > 0)
    loadavg[elem++] = load_info.one_minute;
  if (nelem > 1)
    loadavg[elem++] = load_info.five_minute;
  if (nelem > 2)
    loadavg[elem++] = load_info.fifteen_minute;
# endif /* DGUX */

# if !defined (LDAV_DONE) && defined (apollo)
#  define LDAV_DONE
/* Apollo code from [e-mail] (Ray Lischner).

   This system call is not documented.  The load average is obtained as
   three long integers, for the load average over the past minute,
   five minutes, and fifteen minutes.  Each value is a scaled integer,
   with 16 bits of integer part and 16 bits of fraction part.

   I'm not sure which operating system first supported this system call,
   but I know that SR10.2 supports it.  */

  extern void proc1_$get_loadav ();
  unsigned long load_ave[3];

  proc1_$get_loadav (load_ave);

  if (nelem > 0)
    loadavg[elem++] = load_ave[0] / 65536.0;
  if (nelem > 1)
    loadavg[elem++] = load_ave[1] / 65536.0;
  if (nelem > 2)
    loadavg[elem++] = load_ave[2] / 65536.0;
# endif /* apollo */

# if !defined (LDAV_DONE) && defined (OSF_MIPS)
#  define LDAV_DONE

  struct tbl_loadavg load_ave;
  table (TBL_LOADAVG, 0, &load_ave, 1, sizeof (load_ave));
  loadavg[elem++]
    = (load_ave.tl_lscale == 0
       ? load_ave.tl_avenrun.d[0]
       : (load_ave.tl_avenrun.l[0] / (double) load_ave.tl_lscale));
# endif /* OSF_MIPS */

# if !defined (LDAV_DONE) && (defined (__MSDOS__) || defined (WINDOWS32))
#  define LDAV_DONE

  /* A faithful emulation is going to have to be saved for a rainy day.  */
  for ( ; elem < nelem; elem++)
    {
      loadavg[elem] = 0.0;
    }
# endif  /* __MSDOS__ || WINDOWS32 */

# if !defined (LDAV_DONE) && defined (OSF_ALPHA)
#  define LDAV_DONE

  struct tbl_loadavg load_ave;
  table (TBL_LOADAVG, 0, &load_ave, 1, sizeof (load_ave));
  for (elem = 0; elem < nelem; elem++)
    loadavg[elem]
      = (load_ave.tl_lscale == 0
       ? load_ave.tl_avenrun.d[elem]
       : (load_ave.tl_avenrun.l[elem] / (double) load_ave.tl_lscale));
# endif /* OSF_ALPHA */

# if !defined (LDAV_DONE) && defined (VMS)
  /* VMS specific code -- read from the Load Ave driver.  */

  LOAD_AVE_TYPE load_ave[3];
  static int getloadavg_initialized = 0;
#  ifdef eunice
  struct
  {
    int dsc$w_length;
    char *dsc$a_pointer;
  } descriptor;
#  endif

  /* Ensure that there is a channel open to the load ave device.  */
  if (!getloadavg_initialized)
    {
      /* Attempt to open the channel.  */
#  ifdef eunice
      descriptor.dsc$w_length = 18;
      descriptor.dsc$a_pointer = "$$VMS_LOAD_AVERAGE";
#  else
      $DESCRIPTOR (descriptor, "LAV0:");
#  endif
      if (sys$assign (&descriptor, &channel, 0, 0) & 1)
        getloadavg_initialized = 1;
    }

  /* Read the load average vector.  */
  if (getloadavg_initialized
      && !(sys$qiow (0, channel, IO$_READVBLK, 0, 0, 0,
                     load_ave, 12, 0, 0, 0, 0) & 1))
    {
      sys$dassgn (channel);
      getloadavg_initialized = 0;
    }

  if (!getloadavg_initialized)
    return -1;
# endif /* VMS */

# if !defined (LDAV_DONE) && defined(LOAD_AVE_TYPE) && !defined(VMS)

  /* UNIX-specific code -- read the average from /dev/kmem.  */

#  define LDAV_PRIVILEGED               /* This code requires special installation.  */

  LOAD_AVE_TYPE load_ave[3];

  /* Get the address of LDAV_SYMBOL.  */
  if (offset == 0)
    {
#  ifndef sgi
#   ifndef NLIST_STRUCT
      strcpy (nl[0].n_name, LDAV_SYMBOL);
      strcpy (nl[1].n_name, "");
#   else /* NLIST_STRUCT */
#    ifdef NLIST_NAME_UNION
      nl[0].n_un.n_name = LDAV_SYMBOL;
      nl[1].n_un.n_name = 0;
#    else /* not NLIST_NAME_UNION */
      nl[0].n_name = LDAV_SYMBOL;
      nl[1].n_name = 0;
#    endif /* not NLIST_NAME_UNION */
#   endif /* NLIST_STRUCT */

#   ifndef SUNOS_5
      if (
#    if !(defined (_AIX) && !defined (ps2))
          nlist (KERNEL_FILE, nl)
#    else  /* _AIX */
          knlist (nl, 1, sizeof (nl[0]))
#    endif
          >= 0)
          /* Omit "&& nl[0].n_type != 0 " -- it breaks on Sun386i.  */
          {
#    ifdef FIXUP_KERNEL_SYMBOL_ADDR
            FIXUP_KERNEL_SYMBOL_ADDR (nl);
#    endif
            offset = nl[0].n_value;
          }
#   endif /* !SUNOS_5 */
#  else  /* sgi */
      int ldav_off;

      ldav_off = sysmp (MP_KERNADDR, MPKA_AVENRUN);
      if (ldav_off != -1)
        offset = (long) ldav_off & 0x7fffffff;
#  endif /* sgi */
    }

  /* Make sure we have /dev/kmem open.  */
  if (!getloadavg_initialized)
    {
#  ifndef SUNOS_5
      channel = open ("/dev/kmem", 0);
      if (channel >= 0)
        {
          /* Set the channel to close on exec, so it does not
             litter any child's descriptor table.  */
#   ifdef F_SETFD
#    ifndef FD_CLOEXEC
#     define FD_CLOEXEC 1
#    endif
          (void) fcntl (channel, F_SETFD, FD_CLOEXEC);
#   endif
          getloadavg_initialized = 1;
        }
#  else /* SUNOS_5 */
      /* We pass 0 for the kernel, corefile, and swapfile names
         to use the currently running kernel.  */
      kd = kvm_open (0, 0, 0, O_RDONLY, 0);
      if (kd != 0)
        {
          /* nlist the currently running kernel.  */
          kvm_nlist (kd, nl);
          offset = nl[0].n_value;
          getloadavg_initialized = 1;
        }
#  endif /* SUNOS_5 */
    }

  /* If we can, get the load average values.  */
  if (offset && getloadavg_initialized)
    {
      /* Try to read the load.  */
#  ifndef SUNOS_5
      if (lseek (channel, offset, 0) == -1L
          || read (channel, (char *) load_ave, sizeof (load_ave))
          != sizeof (load_ave))
        {
          close (channel);
          getloadavg_initialized = 0;
        }
#  else  /* SUNOS_5 */
      if (kvm_read (kd, offset, (char *) load_ave, sizeof (load_ave))
          != sizeof (load_ave))
        {
          kvm_close (kd);
          getloadavg_initialized = 0;
        }
#  endif /* SUNOS_5 */
    }

  if (offset == 0 || !getloadavg_initialized)
    return -1;
# endif /* LOAD_AVE_TYPE and not VMS */

# if !defined (LDAV_DONE) && defined (LOAD_AVE_TYPE) /* Including VMS.  */
  if (nelem > 0)
    loadavg[elem++] = LDAV_CVT (load_ave[0]);
  if (nelem > 1)
    loadavg[elem++] = LDAV_CVT (load_ave[1]);
  if (nelem > 2)
    loadavg[elem++] = LDAV_CVT (load_ave[2]);

#  define LDAV_DONE
# endif /* !LDAV_DONE && LOAD_AVE_TYPE */

# ifdef LDAV_DONE
  return elem;
# else
  /* Set errno to zero to indicate that there was no particular error;
     this function just can't work at all on this system.  */
  errno = 0;
  return -1;
# endif
}

#endif /* !HAVE_GETLOADAVG */

static double load_get_system_load() {
  int res;
  double loadavg = -1.0;

  /* It is necessary on some platforms (such as Solaris) to have root
   * privs when doing this, as the information is determined by reading
   * the image of the running kernel (yikes!)
   */
  PRIVS_ROOT
  res = getloadavg(&loadavg, 1);
  PRIVS_RELINQUISH

  /* Return the default value if we did not receive the expected number
   * of elements from getloadavg().
   */
  if (res != 1)
    return -1.0;

  return loadavg;
}

/* Configuration handlers
 */

/* usage: MaxLoad max [mesg] */
MODRET set_maxload(cmd_rec *cmd) {
  double loadval = 0.0;
  config_rec *c = NULL;

  if (cmd->argc-1 < 1 || cmd->argc-1 > 2)
    CONF_ERROR(cmd, "incorrect number of parameters");

  CHECK_CONF(cmd, CONF_ROOT|CONF_VIRTUAL|CONF_GLOBAL);

  if (strcasecmp(cmd->argv[1], "none") == 0)
    loadval = -1.0;
  else {
    loadval = atof(cmd->argv[1]);
    if (loadval < 0.0)
      CONF_ERROR(cmd, "positive load limit required");
  }

  c = add_config_param(cmd->argv[0], cmd->argc-1, NULL);
  c->argv[0] = pcalloc(c->pool, sizeof(double));

  if (loadval < 0.0)
    c->argv[0] = NULL;

  else
    *((double *) c->argv[0]) = loadval;

  if (cmd->argc-1 == 2) {
    c->argv[1] = pcalloc(c->pool, sizeof(char *));
    c->argv[1] = pstrdup(c->pool, cmd->argv[2]);
  }
 
  return HANDLED(cmd);
}

/* Initialization functions
 */

static int load_sess_init(void) {
  config_rec *c = NULL;
  double max_load = 0.0, curr_load = 0.0;
  char curr_load_str[16], max_load_str[16];

  /* Lookup any configured load limit. */
  c = find_config(main_server->conf, CONF_PARAM, "MaxLoad", FALSE);
  if (!c)
    return 0;

  /* If the config_rec is present, but argv[0] is NULL, do nothing */
  if (!c->argv[0])
    return 0;
  max_load = *((double *) c->argv[0]);

  curr_load = load_get_system_load();
  if (curr_load < 0) {
    pr_log_pri(PR_LOG_NOTICE,
      "notice: unable to determine system load average: %s", strerror(errno));
    return 0;
  }

  pr_log_debug(DEBUG5, MOD_LOAD_VERSION ": current system load: %.2f",
    curr_load);

  if (curr_load >= max_load) {
    pr_log_pri(PR_LOG_INFO, "MaxLoad (%.2f) reached: connection denied",
      max_load);

    if (c->argc == 2)
      pr_response_send(R_421, "%s", (const char *) c->argv[1]);
    else
      pr_response_send(R_421, "System busy, try again later");

    end_login(1);
  }

  /* Register some Variable entries for showing the system load. */
  memset(curr_load_str, '\0', sizeof(curr_load_str));
  snprintf(curr_load_str, sizeof(curr_load_str)-1, "%.2f", curr_load);
  if (pr_var_set(session.pool, "%{mod_load.curr_load}",
      "Current system load average", PR_VAR_TYPE_STR,
      curr_load_str, NULL, 0) < 0)
    pr_log_debug(DEBUG1, MOD_LOAD_VERSION
      ": error setting %%{mod_load.curr_load} variable: %s", strerror(errno));

  memset(max_load_str, '\0', sizeof(max_load_str));
  snprintf(max_load_str, sizeof(max_load_str)-1, "%.2f", max_load);
  if (pr_var_set(session.pool, "%{mod_load.max_load}",
      "Maximum system load average", PR_VAR_TYPE_STR,
      max_load_str, NULL, 0) < 0)
    pr_log_debug(DEBUG1, MOD_LOAD_VERSION
      ": error setting %%{mod_load.max_load} variable: %s", strerror(errno));

  return 0;
}

/* Module API tables
 */

static conftable load_conftab[] = {
  { "MaxLoad",		set_maxload,		NULL },
  { NULL }
};

module load_module = {
  NULL, NULL,

  /* Module API version 2.0 */
  0x20,

  /* Module name */
  "load",

  /* Module configuration handler table */
  load_conftab,

  /* Module command table */
  NULL,

  /* Module authentication handler table */
  NULL,

  /* Module initialization function */
  NULL,

  /* Session initialization function */
  load_sess_init,

  /* Module version */
  MOD_LOAD_VERSION
};