/*
 * ProFTPD: mod_load -- a module for refusing connections based on system load
 *
 * Copyright (c) 2001-2011 TJ Saunders
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA.
 *
 * As a special exemption, TJ Saunders and other respective copyright holders
 * give permission to link this program with OpenSSL, and distribute the
 * resulting executable, without including the source code for OpenSSL in the
 * source distribution.
 *
 * This is mod_load, contrib software for proftpd 1.2.x and above.
 * For more information contact TJ Saunders <tj@castaglia.org>.
 *
 * Based on the getloadavg.c file included in GNU make-3.79, which carries
 * the following copyright:
 *
 *   Copyright (C) 1985, 86, 87, 88, 89, 91, 92, 93, 1994, 1995, 1997
 *     Free Software Foundation, Inc.
 * 
 * $Id: mod_load.c.in,v 1.10 2011-05-23 20:58:46 castaglia Exp $
 * $Libraries: @MODULE_LIBS@ $
 */

#include "conf.h"
#include "privs.h"
#include "mod_load.h"

#define MOD_LOAD_VERSION		"mod_load/1.0.1"

/* Make sure the version of proftpd is as necessary. */
#if PROFTPD_VERSION_NUMBER < 0x0001030402
# error "ProFTPD 1.3.4rc2 or later required"
#endif

/* Support code.  Most of this is from getloadavg.c
 */

#if defined (unix) || defined (__unix)
# include <sys/param.h>
#endif

#ifndef HAVE_GETLOADAVG
# if !defined(LDAV_CVT) && defined(LOAD_AVE_CVT)
#  define LDAV_CVT(n) (LOAD_AVE_CVT (n) / 100.0)
# endif

# if !defined (BSD) && defined (ultrix)
#  define BSD
# endif

# ifdef NeXT
#  undef BSD
#  undef FSCALE
# endif

# ifdef __GNU__
#  undef BSD
#  undef FSCALE
# endif /* __GNU__ */

# if defined (HPUX) && !defined (hpux)
#  define hpux
# endif

# if defined (__hpux) && !defined (hpux)
#  define hpux
# endif

# if defined (__sun) && !defined (sun)
#  define sun
# endif

# if defined(hp300) && !defined(hpux)
#  define MORE_BSD
# endif

# if defined(ultrix) && defined(mips)
#  define decstation
# endif

# if defined (__SVR4) && !defined (SVR4)
#  define SVR4
# endif

# if (defined(sun) && defined(SVR4)) || defined (SOLARIS2)
#  define SUNOS_5
# endif

# if defined (__osf__) && (defined (__alpha) || defined (__alpha__))
#  define OSF_ALPHA
#  include <sys/mbuf.h>
#  include <sys/socket.h>
#  include <net/route.h>
#  include <sys/table.h>
# endif

# if defined (__osf__) && (defined (mips) || defined (__mips__))
#  define OSF_MIPS
#  include <sys/table.h>
# endif

# if !defined (tek4300) && defined (unix) && defined (m68k) && defined (mc68000) && defined (mc68020) && defined (_MACH_IND_SYS_TYPES)
#  define tek4300
# endif

# ifndef LOAD_AVE_TYPE

#  ifdef MORE_BSD
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef sun
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef decstation
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef _SEQUENT_
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef sgi
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef SVR4
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef sony_news
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef sequent
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef OSF_ALPHA
#   define LOAD_AVE_TYPE long
#  endif

#  if defined (ardent) && defined (titan)
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef tek4300
#   define LOAD_AVE_TYPE long
#  endif

#  if defined(alliant) && defined(i860) /* Alliant FX/2800 */
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef _AIX
#   define LOAD_AVE_TYPE long
#  endif

#  ifdef convex
#   define LOAD_AVE_TYPE double
#   ifndef LDAV_CVT
#    define LDAV_CVT(n) (n)
#   endif
#  endif

# endif /* No LOAD_AVE_TYPE.  */

# ifdef OSF_ALPHA
#  undef FSCALE
#  define FSCALE 1024.0
# endif

# if defined(alliant) && defined(i860) /* Alliant FX/2800 */
#  undef FSCALE
#  define FSCALE 100.0
# endif

# ifndef        FSCALE

#  ifdef MORE_BSD
#   define FSCALE 2048.0
#  endif

#  if defined(MIPS) || defined(SVR4) || defined(decstation)
#   define FSCALE 256
#  endif

#  if defined (sgi) || defined (sequent)
#   undef FSCALE
#   define      FSCALE 1000.0
#  endif

#  if defined (ardent) && defined (titan)
#   define FSCALE 65536.0
#  endif

#  ifdef tek4300
#   define FSCALE 100.0
#  endif

#  ifdef _AIX
#   define FSCALE 65536.0
#  endif

# endif /* Not FSCALE.  */

# if !defined (LDAV_CVT) && defined (FSCALE)
#  define       LDAV_CVT(n) (((double) (n)) / FSCALE)
# endif

# ifndef NLIST_STRUCT

#  ifdef MORE_BSD
#   define NLIST_STRUCT
#  endif

#  ifdef sun
#   define NLIST_STRUCT
#  endif

#  ifdef decstation
#   define NLIST_STRUCT
#  endif

#  ifdef hpux
#   define NLIST_STRUCT
#  endif

#  if defined (_SEQUENT_) || defined (sequent)
#   define NLIST_STRUCT
#  endif

#  ifdef sgi
#   define NLIST_STRUCT
#  endif

#  ifdef SVR4
#   define NLIST_STRUCT
#  endif

#  ifdef sony_news
#   define NLIST_STRUCT
#  endif

#  ifdef OSF_ALPHA
#   define NLIST_STRUCT
#  endif

#  if defined (ardent) && defined (titan)
#   define NLIST_STRUCT
#  endif

#  ifdef tek4300
#   define NLIST_STRUCT
#  endif

#  ifdef butterfly
#   define NLIST_STRUCT
#  endif

#  if defined(alliant) && defined(i860) /* Alliant FX/2800 */
#   define NLIST_STRUCT
#  endif

#  ifdef _AIX
#   define NLIST_STRUCT
#  endif

# endif /* defined (NLIST_STRUCT) */

# if defined(sgi) || (defined(mips) && !defined(BSD))
#  define FIXUP_KERNEL_SYMBOL_ADDR(nl) ((nl)[0].n_value &= ~(1 << 31))
# endif

# if !defined (KERNEL_FILE) && defined (sequent)
#  define KERNEL_FILE "/dynix"
# endif

# if !defined (KERNEL_FILE) && defined (hpux)
#  define KERNEL_FILE "/hp-ux"
# endif

# if !defined(KERNEL_FILE) && (defined(_SEQUENT_) || defined(MIPS) || defined(SVR4) || defined(ISC) || defined (sgi) || (defined (ardent) && defined (titan)))
#  define KERNEL_FILE "/unix"
# endif

# if !defined (LDAV_SYMBOL) && defined (alliant)
#  define LDAV_SYMBOL "_Loadavg"
# endif

# if !defined(LDAV_SYMBOL) && ((defined(hpux) && !defined(hp9000s300)) || defined(_SEQUENT_) || defined(SVR4) || defined(ISC) || defined(sgi) || (defined (ardent) && defined (titan)) || defined (_AIX))
#  define LDAV_SYMBOL "avenrun"
# endif

# ifdef HAVE_UNISTD_H
#  include <unistd.h>
# endif

# include <stdio.h>

# if !defined(LOAD_AVE_TYPE) && (defined(BSD) || defined(LDAV_CVT) || defined(KERNEL_FILE) || defined(LDAV_SYMBOL))
#  define LOAD_AVE_TYPE double
# endif

# ifdef LOAD_AVE_TYPE

#  ifndef VMS
#   ifndef __linux__
#    ifndef NLIST_STRUCT
#     include <a.out.h>
#    else /* NLIST_STRUCT */
#     include <nlist.h>
#    endif /* NLIST_STRUCT */

#    ifdef SUNOS_5
#     include <fcntl.h>
#     include <kvm.h>
#     include <kstat.h>
#    endif

#    if defined (hpux) && defined (HAVE_PSTAT_GETDYNAMIC)
#     include <sys/pstat.h>
#    endif

#    ifndef KERNEL_FILE
#     define KERNEL_FILE "/vmunix"
#    endif /* KERNEL_FILE */

#    ifndef LDAV_SYMBOL
#     define LDAV_SYMBOL "_avenrun"
#    endif /* LDAV_SYMBOL */
#   endif /* __linux__ */

#  else /* VMS */

#   ifndef eunice
#    include <iodef.h>
#    include <descrip.h>
#   else /* eunice */
#    include <vms/iodef.h>
#   endif /* eunice */
#  endif /* VMS */

#  ifndef LDAV_CVT
#   define LDAV_CVT(n) ((double) (n))
#  endif /* !LDAV_CVT */

# endif /* LOAD_AVE_TYPE */

# if defined(__GNU__) && !defined (NeXT)
#  define NeXT
#  define host_self mach_host_self
# endif

# ifdef NeXT
#  ifdef HAVE_MACH_MACH_H
#   include <mach/mach.h>
#  else
#   include <mach.h>
#  endif
# endif /* NeXT */

# ifdef sgi
#  include <sys/sysmp.h>
# endif /* sgi */

# ifdef UMAX
#  include <stdio.h>
#  include <signal.h>
#  include <sys/time.h>
#  include <sys/wait.h>
#  include <sys/syscall.h>

#  ifdef UMAX_43
#   include <machine/cpu.h>
#   include <inq_stats/statistics.h>
#   include <inq_stats/sysstats.h>
#   include <inq_stats/cpustats.h>
#   include <inq_stats/procstats.h>
#  else /* Not UMAX_43.  */
#   include <sys/sysdefs.h>
#   include <sys/statistics.h>
#   include <sys/sysstats.h>
#   include <sys/cpudefs.h>
#   include <sys/cpustats.h>
#   include <sys/procstats.h>
#  endif /* Not UMAX_43.  */
# endif /* UMAX */

# ifdef DGUX
#  include <sys/dg_sys_info.h>
# endif

# if defined(HAVE_FCNTL_H) || defined(_POSIX_VERSION)
#  include <fcntl.h>
# else
#  include <sys/file.h>
# endif

# ifdef NeXT
static processor_set_t default_set;
static int getloadavg_initialized;
# endif /* NeXT */

# ifdef UMAX
static unsigned int cpus = 0;
static unsigned int samples;
# endif /* UMAX */

# ifdef DGUX
static struct dg_sys_info_load_info load_info;  /* what-a-mouthful! */
# endif /* DGUX */

# if !defined(HAVE_LIBKSTAT) && defined(LOAD_AVE_TYPE) && !defined(__linux__)
/* File descriptor open to /dev/kmem or VMS load ave driver.  */
static int channel;
/* Nonzero iff channel is valid.  */
static int getloadavg_initialized;
/* Offset in kmem to seek to read load average, or 0 means invalid.  */
static long offset;

#  if !defined(VMS) && !defined(sgi) && !defined(__linux__)
static struct nlist nl[2];
#  endif /* Not VMS or sgi */

#  ifdef SUNOS_5
static kvm_t *kd;
#  endif /* SUNOS_5 */

# endif /* LOAD_AVE_TYPE && !HAVE_LIBKSTAT */

/* Put the 1 minute, 5 minute and 15 minute load averages into the first
 * NELEM elements of LOADAVG.  Return the number written (never more than 3,
 * but may be less than NELEM), or -1 if an error occurred.
 */

static int getloadavg(double *loadavg, int nelem) {
  int elem = 0;                 /* Return value.  */

# ifdef NO_GET_LOAD_AVG
#  define LDAV_DONE
  /* 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;
  elem = -1;
# endif

# if !defined (LDAV_DONE) && defined (HAVE_LIBKSTAT)
/* Use libkstat because we don't have to be root.  */
#  define LDAV_DONE
  kstat_ctl_t *kc;
  kstat_t *ksp;
  kstat_named_t *kn;

  kc = kstat_open ();
  if (kc == 0)
    return -1;
  ksp = kstat_lookup (kc, "unix", 0, "system_misc");
  if (ksp == 0 )
    return -1;
  if (kstat_read (kc, ksp, 0) == -1)
    return -1;


  kn = kstat_data_lookup (ksp, "avenrun_1min");
  if (kn == 0)
    {
      /* Return -1 if no load average information is available.  */
      nelem = 0;
      elem = -1;
    }

  if (nelem >= 1)
    loadavg[elem++] = (double) kn->value.ul/FSCALE;

  if (nelem >= 2)
    {
      kn = kstat_data_lookup (ksp, "avenrun_5min");
      if (kn != 0)
        {
          loadavg[elem++] = (double) kn->value.ul/FSCALE;

          if (nelem >= 3)
            {
              kn = kstat_data_lookup (ksp, "avenrun_15min");
              if (kn != 0)
                loadavg[elem++] = (double) kn->value.ul/FSCALE;
            }
        }
    }

  kstat_close (kc);
# endif /* HAVE_LIBKSTAT */

# if !defined (LDAV_DONE) && defined (hpux) && defined (HAVE_PSTAT_GETDYNAMIC)
/* Use pstat_getdynamic() because we don't have to be root.  */
#  define LDAV_DONE
#  undef LOAD_AVE_TYPE

  struct pst_dynamic dyn_info;
  if (pstat_getdynamic (&dyn_info, sizeof (dyn_info), 0, 0) < 0)
    return -1;
  if (nelem > 0)
    loadavg[elem++] = dyn_info.psd_avg_1_min;
  if (nelem > 1)
    loadavg[elem++] = dyn_info.psd_avg_5_min;
  if (nelem > 2)
    loadavg[elem++] = dyn_info.psd_avg_15_min;

# endif /* hpux && HAVE_PSTAT_GETDYNAMIC */

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

#  ifndef LINUX_LDAV_FILE
#   define LINUX_LDAV_FILE "/proc/loadavg"
#  endif

  char ldavgbuf[40];
  double load_ave[3];
  int fd, count;

  fd = open (LINUX_LDAV_FILE, O_RDONLY);
  if (fd == -1)
    return -1;
  count = read (fd, ldavgbuf, 40);
  (void) close (fd);
  if (count <= 0)
    return -1;

  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 lisch@mentorg.com (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 */

module load_module;

static double load_get_system_load(void) {
  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 PR_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"));
    }

    pr_session_disconnect(&load_module, PR_SESS_DISCONNECT_MODULE_ACL,
      "MaxLoad");
  }

  /* 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
};
