IABSD.fr/src/lib/libc/sys/sysctl.2

Branch : - branch - master - tag -

• Show log

  Commit

• Author : jca
  Date : 2026-04-04 19:26:32
  Hash : 9340cd4a
  Message : Fix hw.blockcpu sysctl variable name From Matthias Schmidt

• lib/libc/sys/sysctl.2

• .\"	$OpenBSD: sysctl.2,v 1.72 2026/04/04 19:26:32 jca Exp $
  .\"
  .\" Copyright (c) 1993
  .\"	The Regents of the University of California.  All rights reserved.
  .\"
  .\" Redistribution and use in source and binary forms, with or without
  .\" modification, are permitted provided that the following conditions
  .\" are met:
  .\" 1. Redistributions of source code must retain the above copyright
  .\"    notice, this list of conditions and the following disclaimer.
  .\" 2. Redistributions in binary form must reproduce the above copyright
  .\"    notice, this list of conditions and the following disclaimer in the
  .\"    documentation and/or other materials provided with the distribution.
  .\" 3. Neither the name of the University nor the names of its contributors
  .\"    may be used to endorse or promote products derived from this software
  .\"    without specific prior written permission.
  .\"
  .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  .\" SUCH DAMAGE.
  .\"
  .Dd $Mdocdate: April 4 2026 $
  .Dt SYSCTL 2
  .Os
  .Sh NAME
  .Nm sysctl
  .Nd get or set system information
  .Sh SYNOPSIS
  .In sys/types.h
  .In sys/sysctl.h
  .Ft int
  .Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
  .Sh DESCRIPTION
  The
  .Fn sysctl
  function retrieves system information and allows processes with
  appropriate privileges to set system information.
  The information available from
  .Fn sysctl
  consists of integers, strings, and tables.
  Information may be retrieved and set using the
  .Xr sysctl 8
  utility;
  the variable names used by this utility are given here in parentheses.
  .Pp
  Unless explicitly noted below,
  .Fn sysctl
  returns a consistent snapshot of the data requested.
  Consistency is obtained by locking the destination
  buffer into memory so that the data may be copied out without blocking.
  Calls to
  .Fn sysctl
  are serialized to avoid deadlock.
  .Pp
  The state is described using a
  .Dq Management Information Base (MIB)
  style name, listed in
  .Fa name ,
  which is a
  .Fa namelen
  length array of integers.
  .Pp
  The information is copied into the buffer specified by
  .Fa oldp .
  The size of the buffer is given by the location specified by
  .Fa oldlenp
  before the call,
  and that location gives the amount of data copied after a successful call.
  If the amount of data available is greater
  than the size of the buffer supplied,
  the call supplies as much data as fits in the buffer provided
  and returns with the error code
  .Er ENOMEM .
  If the old value is not desired,
  .Fa oldp
  and
  .Fa oldlenp
  should be set to
  .Dv NULL .
  .Pp
  The size of the available data can be determined by calling
  .Fn sysctl
  with a
  .Dv NULL
  parameter for
  .Fa oldp .
  The size of the available data will be returned in the location pointed to by
  .Fa oldlenp .
  For some operations, the amount of space may change often.
  For these operations,
  the system attempts to round up so that the returned size is
  large enough for a call to return the data shortly thereafter.
  .Pp
  The terminating NUL character is included in the lengths of string values.
  .Pp
  To set a new value,
  .Fa newp
  is set to point to a buffer of length
  .Fa newlen
  from which the requested value is to be taken.
  If a new value is not to be set,
  .Fa newp
  should be set to
  .Dv NULL
  and
  .Fa newlen
  set to 0.
  .Pp
  The top level names are defined with a
  .Dv CTL_
  prefix in
  .In sys/sysctl.h ,
  and are as follows.
  The next and subsequent levels down are found in the include files
  listed here, and described in separate sections below.
  .Bl -column "CTL_MACHDEP" "ufs/ffs/ffs_extern.h" "Description" -offset indent
  .It Sy "Name" Ta Sy "Next level names" Ta Sy "Description"
  .It Dv CTL_DDB Ta "ddb/db_var.h" Ta "Kernel debugger"
  .It Dv CTL_DEBUG Ta "sys/sysctl.h" Ta "Debugging"
  .It Dv CTL_HW Ta "sys/sysctl.h" Ta "Generic CPU, I/O"
  .It Dv CTL_KERN Ta "sys/sysctl.h" Ta "High kernel limits"
  .It Dv CTL_MACHDEP Ta "sys/sysctl.h" Ta "Machine dependent"
  .It Dv CTL_NET Ta "sys/socket.h" Ta "Networking"
  .It Dv CTL_VFS Ta "ufs/ffs/ffs_extern.h" Ta "Virtual file system"
  .It Dv CTL_VM Ta "uvm/uvmexp.h" Ta "Virtual memory"
  .El
  .Pp
  For example, the following retrieves the maximum number of processes allowed
  in the system:
  .Bd -literal -offset indent
  int mib[2], maxproc;
  size_t len;
  
  mib[0] = CTL_KERN;
  mib[1] = KERN_MAXPROC;
  len = sizeof(maxproc);
  if (sysctl(mib, 2, &maxproc, &len, NULL, 0) == -1)
  	err(1, "sysctl");
  .Ed
  .Ss CTL_DDB
  Integer information and settable variables are available for the
  .Dv CTL_DDB level ,
  as described below.
  More information is also available in
  .Xr ddb 4 .
  .Bl -column "Second level name" "integer" "Changeable" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv DBCTL_CONSOLE Ta "integer" Ta "yes"
  .It Dv DBCTL_LOG Ta "integer" Ta "yes"
  .It Dv DBCTL_MAXLINE Ta "integer" Ta "yes"
  .It Dv DBCTL_MAXWIDTH Ta "integer" Ta "yes"
  .It Dv DBCTL_PANIC Ta "integer" Ta "yes"
  .It Dv DBCTL_RADIX Ta "integer" Ta "yes"
  .It Dv DBCTL_TABSTOP Ta "integer" Ta "yes"
  .It Dv DBCTL_TRIGGER Ta "integer" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv DBCTL_CONSOLE Pq Va ddb.console
  When this variable is set, an architecture dependent magic key sequence
  on the console or a debugger button will permit entry into the kernel debugger.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be raised.
  .It Dv DBCTL_LOG Pq Va ddb.log
  When set, ddb output is also logged in the kernel message buffer.
  .It Dv DBCTL_MAXLINE Pq Va ddb.max_line
  Determines the number of lines to page in
  .Xr ddb 4 .
  This variable is also available as the ddb
  .Dv $lines
  variable.
  .It Dv DBCTL_MAXWIDTH Pq Va ddb.max_width
  Determines the maximum width of a line in
  .Xr ddb 4 .
  This variable is also available as the ddb
  .Dv $maxwidth
  variable.
  .It Dv DBCTL_PANIC Pq Va ddb.panic
  When this variable is set, system panics may drop into the kernel debugger.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be raised.
  .It Dv DBCTL_RADIX Pq Va ddb.radix
  Determines the default radix or base for non-prefixed numbers
  entered into
  .Xr ddb 4 .
  This variable is also available as the ddb
  .Dv $radix
  variable.
  .It Dv DBCTL_TABSTOP Pq Va ddb.tab_stop_width
  Width of a tab stop in
  .Xr ddb 4 .
  This variable is also available as the ddb
  .Dv $tabstops
  variable.
  .It Dv DBCTL_TRIGGER Pq Va ddb.trigger
  When
  .Dv DBCTL_CONSOLE
  is set,
  writing to
  .Dv DBCTL_TRIGGER
  causes the system to enter
  .Xr ddb 4 .
  When running with a
  .Xr securelevel 7
  greater than 0,
  the process writing to this variable must be running
  on the console in order to enter
  .Xr ddb 4 .
  .El
  .Ss CTL_DEBUG
  The debugging variables vary from system to system.
  A debugging variable may be added or deleted without need to recompile
  .Fn sysctl
  to know about it.
  Each time it runs,
  .Fn sysctl
  gets the list of debugging variables from the kernel and
  displays their current values.
  The system defines twenty
  .Vt struct ctldebug
  variables named
  .Va debug0
  through
  .Va debug19 .
  They are declared as separate variables so that they can be
  individually initialized at the location of their associated variable.
  The loader prevents multiple use of the same variable by issuing errors
  if a variable is initialized in more than one place.
  For example, to export the variable
  .Va dospecialcheck
  as a debugging variable, the following declaration would be used:
  .Bd -literal -offset indent
  int dospecialcheck = 1;
  struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
  .Ed
  .Ss CTL_HW
  The string and integer information available for the
  .Dv CTL_HW
  level is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "Second level name" "integer" "Changeable" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv HW_ALLOWPOWERDOWN Ta "integer" Ta "yes"
  .It Dv HW_BATTERY Ta "node" Ta "not applicable"
  .It Dv HW_BYTEORDER Ta "integer" Ta "no"
  .It Dv HW_CPUSPEED Ta "integer" Ta "no"
  .It Dv HW_DISKCOUNT Ta "integer" Ta "no"
  .It Dv HW_DISKNAMES Ta "string" Ta "no"
  .It Dv HW_DISKSTATS Ta "struct" Ta "no"
  .It Dv HW_MACHINE Ta "string" Ta "no"
  .It Dv HW_MODEL Ta "string" Ta "no"
  .It Dv HW_NCPU Ta "integer" Ta "no"
  .It Dv HW_NCPUFOUND Ta "integer" Ta "no"
  .It Dv HW_NCPUONLINE Ta "integer" Ta "no"
  .It Dv HW_PAGESIZE Ta "integer" Ta "no"
  .It Dv HW_PERFPOLICY Ta "string" Ta "yes"
  .It Dv HW_PHYSMEM Ta "integer" Ta "no"
  .It Dv HW_PHYSMEM64 Ta "int64_t" Ta "no"
  .It Dv HW_POWER Ta "integer" Ta "no"
  .It Dv HW_PRODUCT Ta "string" Ta "no"
  .It Dv HW_SENSORS Ta "node" Ta "not applicable"
  .It Dv HW_SETPERF Ta "integer" Ta "yes"
  .It Dv HW_SMT Ta "integer" Ta "yes"
  .It Dv HW_UCOMNAMES Ta "string" Ta "no"
  .It Dv HW_BLOCKCPU Ta "string" Ta "yes"
  .It Dv HW_USERMEM Ta "integer" Ta "no"
  .It Dv HW_USERMEM64 Ta "int64_t" Ta "no"
  .It Dv HW_UUID Ta "string" Ta "no"
  .It Dv HW_VENDOR Ta "string" Ta "no"
  .It Dv HW_VERSION Ta "string" Ta "no"
  .El
  .Bl -tag -width "123456"
  .It Dv HW_ALLOWPOWERDOWN Pq Va hw.allowpowerdown
  Some machines generate an interrupt when the power button is pressed
  and a driver can catch that interrupt.
  When this variable is set, such an event will cause the system to
  perform a regular shutdown and power off the machine.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Dv HW_BATTERY Pq Va hw.battery
  Control battery charging.
  These are only available on hardware that supports battery charging control.
  There are three subnodes:
  .Bl -column "HW_BATTERY_CHARGESTART" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv HW_BATTERY_CHARGEMODE Ta "integer" Ta "yes"
  .It Dv HW_BATTERY_CHARGESTART Ta "integer" Ta "maybe"
  .It Dv HW_BATTERY_CHARGESTOP Ta "integer" Ta "yes"
  .El
  .Pp
  Their meanings are as follows:
  .Bl -tag -width "123456"
  .It Dv HW_BATTERY_CHARGEMODE Pq Va hw.battery.chargemode
  Control if the battery is charged or discharged.
  A value of -1 means to (forcibly) discharge the battery.
  A value of 0 means to inhibit charging the battery.
  A value of 1 means to charge the battery, subject to the configured limits.
  .It Dv HW_BATTERY_CHARGESTART Pq Va hw.battery.chargestart
  The percentage below which the battery will start charging.
  Not all hardware allows setting this value.
  On hardware that does not allow setting this value the battery will typically
  start charging at a fixed percentage point below the value configured through
  .Dv HW_BATTERY_CHARGESTOP .
  .It Dv HW_BATTERY_CHARGESTOP Pq Va hw.battery.chargestop
  The percentage above which the battery will stop charging.
  Setting the value to 100 will fully charge the battery.
  .El
  .Pp
  By setting
  .Dv HW_BATTERY_CHARGEMODE
  to 1, and setting both
  .Dv HW_BATTERY_CHARGESTART
  and
  .Dv HW_BATTERY_CHARGESTOP ,
  the battery will be kept charged at a percentage between the configured limits.
  .It Dv HW_BYTEORDER Pq Va hw.byteorder
  The byteorder (4321 or 1234).
  .It Dv HW_CPUSPEED Pq Va hw.cpuspeed
  The current CPU frequency
  .Pq in MHz .
  .It Dv HW_DISKCOUNT Pq Va hw.diskcount
  The number of disks currently attached to the system.
  .It Dv HW_DISKNAMES Pq Va hw.disknames
  A comma-separated list of disk names.
  .It Dv HW_DISKSTATS Pq Va hw.diskstats
  An array of
  .Vt struct diskstats
  structures containing disk statistics.
  .It Dv HW_MACHINE Pq Va hw.machine
  The kernel architecture as returned by
  .Xr uname 1
  .Fl m
  and by
  .Xr machine 1 .
  .It Dv HW_MODEL Pq Va hw.model
  The machine model.
  .It Dv HW_NCPU Pq Va hw.ncpu
  The number of CPUs configured.
  .It Dv HW_NCPUFOUND Pq Va hw.ncpufound
  The number of CPUs found.
  .It Dv HW_NCPUONLINE Pq Va hw.ncpuonline
  The number of CPUs online.
  .It Dv HW_PAGESIZE Pq Va hw.pagesize
  The software page size.
  .It Dv HW_PERFPOLICY Pq Va hw.perfpolicy
  The performance policy for power management.
  Can be one of
  .Dq manual ,
  .Dq auto ,
  or
  .Dq high .
  If the policy contains a comma, the second part specifies an alternative
  policy used while the system is running on battery.
  The
  .Nm
  API only exports the currently applicable policy.
  .\" XXX keep in sync with apmd(8)
  The default setting is
  .Dq high,auto .
  .It Dv HW_PHYSMEM
  The total physical memory, in bytes.
  This variable is deprecated; use
  .Dv HW_PHYSMEM64
  instead.
  .It Dv HW_PHYSMEM64 Pq Va hw.physmem
  The total physical memory, in bytes.
  .It Dv HW_POWER Pq Va hw.power
  Machine has wall-power.
  .It Dv HW_PRODUCT Pq Va hw.product
  The product name of the machine.
  .It Dv HW_SENSORS Pq Va hw.sensors
  Third level comprises an array of
  .Vt struct sensordev
  structures containing information about devices
  that may attach hardware monitoring sensors.
  .Pp
  Third, fourth and fifth levels together comprise an array of
  .Vt struct sensor
  structures containing snapshot readings of hardware monitoring sensors.
  In such usage, third level indicates the numerical representation
  of the sensor device name to which the sensor is attached
  (a device's xname and number are matched with the help of
  .Vt struct sensordev
  structure above),
  fourth level indicates sensor type and
  fifth level is an ordinal sensor number (unique to
  the specified sensor type on the specified sensor device).
  .Pp
  The
  .Sy sensordev
  and
  .Sy sensor
  structures
  and
  .Sy sensor_type
  enumeration
  are defined in
  .In sys/sensors.h .
  .It Dv HW_SERIALNO Pq Va hw.serialno
  The serial number of the machine.
  .It Dv HW_SETPERF Pq Va hw.setperf
  Current CPU performance
  .Pq percentage .
  It is only modifiable if
  .Dv HW_PERFPOLICY
  is set to
  .Dq manual .
  .It Dv HW_SMT Pq Va hw.smt
  If set to 1, enable simultaneous multithreading (SMT) on CPUs that
  support it.
  Deprecated, use
  .Va hw.blockcpu
  instead.
  .It Dv HW_BLOCKCPU Pq Va hw.blockcpu
  A series of characters
  .Ar ( S
  (SMT),
  .Ar P
  (Performance core),
  .Ar E
  (Efficiency core),
  and
  .Ar L
  (Lethargic, Low Power Efficiency core)
  representing cpu types to avoid schedule tasks onto.
  .It Dv HW_UCOMNAMES Pq Va hw.ucomnames
  A comma-separated list of currently attached
  .Xr ucom 4
  devices in the following format:
  .Pp
  .Sm off
  .D1 Sy ucom Ar N : Sy usb Ar bus.rootport.route.interface
  .Sm on
  .Pp
  The
  .Ar route
  consists of five hexadecimal digits identifying the path from
  the root port to the port containing the
  .Ar interface .
  .It Dv HW_USERMEM
  The amount of available non-kernel memory in bytes.
  This variable is deprecated; use
  .Dv HW_USERMEM64
  instead.
  .It Dv HW_USERMEM64 Pq Va hw.usermem
  The amount of available non-kernel memory in bytes.
  .It Dv HW_UUID Pq Va hw.uuid
  The universal unique identification number assigned to the machine.
  .It Dv HW_VENDOR Pq Va hw.vendor
  The vendor name for this machine.
  .It Dv HW_VERSION Pq Va hw.version
  The version or revision of this machine.
  .El
  .Ss CTL_KERN
  The string and integer information available for the
  .Dv CTL_KERN
  level is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  The types of data currently available are process information,
  system vnodes, the open file entries, routing table entries,
  virtual memory statistics, load average history, and clock rate
  information.
  .Bl -column "KERN_PROC_NOBROADCASTKILL" "u_int64_t[CPUSTATES]" "no" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_ALLOWDT Ta "integer" Ta "yes"
  .It Dv KERN_ALLOWKMEM Ta "integer" Ta "yes"
  .It Dv KERN_ARGMAX Ta "integer" Ta "no"
  .It Dv KERN_AUDIO Ta "node" Ta "yes"
  .It Dv KERN_BOOTTIME Ta "struct timeval" Ta "no"
  .It Dv KERN_CACHEPCT Ta "integer" Ta "yes"
  .It Dv KERN_CCPU Ta "integer" Ta "no"
  .It Dv KERN_CLOCKRATE Ta "struct clockinfo" Ta "no"
  .It Dv KERN_CONSDEV Ta "dev_t" Ta "no"
  .It Dv KERN_CPTIME Ta "long[CPUSTATES]" Ta "no"
  .It Dv KERN_CPTIME2 Ta "u_int64_t[CPUSTATES]" Ta "no"
  .It Dv KERN_CPUSTATS Ta "struct cpustats" Ta "no"
  .It Dv KERN_DOMAINNAME Ta "string" Ta "yes"
  .It Dv KERN_FILE Ta "struct kinfo_file" Ta "no"
  .It Dv KERN_FORKSTAT Ta "struct forkstat" Ta "no"
  .It Dv KERN_FSCALE Ta "integer" Ta "no"
  .It Dv KERN_FSYNC Ta "integer" Ta "no"
  .It Dv KERN_GLOBAL_PTRACE Ta "integer" Ta "yes"
  .It Dv KERN_HOSTID Ta "integer" Ta "yes"
  .It Dv KERN_HOSTNAME Ta "string" Ta "yes"
  .It Dv KERN_INTRCNT Ta "node" Ta "not applicable"
  .It Dv KERN_JOB_CONTROL Ta "integer" Ta "no"
  .It Dv KERN_MALLOCSTATS Ta "node" Ta "no"
  .It Dv KERN_MAXCLUSTERS Ta "integer" Ta "yes"
  .It Dv KERN_MAXFILES Ta "integer" Ta "yes"
  .It Dv KERN_MAXLOCKSPERUID Ta "integer" Ta "yes"
  .It Dv KERN_MAXPARTITIONS Ta "integer" Ta "no"
  .It Dv KERN_MAXPROC Ta "integer" Ta "yes"
  .It Dv KERN_MAXTHREAD Ta "integer" Ta "yes"
  .It Dv KERN_MAXVNODES Ta "integer" Ta "yes"
  .It Dv KERN_MBSTAT Ta "struct mbstat" Ta "no"
  .It Dv KERN_MSGBUF Ta "char[]" Ta "no"
  .It Dv KERN_MSGBUFSIZE Ta "integer" Ta "no"
  .It Dv KERN_NCHSTATS Ta "struct nchstats" Ta "no"
  .It Dv KERN_NFILES Ta "integer" Ta "no"
  .It Dv KERN_NGROUPS Ta "integer" Ta "no"
  .It Dv KERN_NOSUIDCOREDUMP Ta "integer" Ta "yes"
  .It Dv KERN_NPROCS Ta "integer" Ta "no"
  .It Dv KERN_NTHREADS Ta "integer" Ta "no"
  .It Dv KERN_NUMVNODES Ta "integer" Ta "no"
  .It Dv KERN_OSRELEASE Ta "string" Ta "no"
  .It Dv KERN_OSREV Ta "integer" Ta "no"
  .It Dv KERN_OSTYPE Ta "string" Ta "no"
  .It Dv KERN_OSVERSION Ta "string" Ta "no"
  .It Dv KERN_PFSTATUS Ta "struct pf_status" Ta "no"
  .It Dv KERN_POOL_DEBUG Ta "integer" Ta "yes"
  .It Dv KERN_POSIX1 Ta "integer" Ta "no"
  .It Dv KERN_PROC Ta "struct kinfo_proc" Ta "no"
  .It Dv KERN_PROC_ARGS Ta "node" Ta "not applicable"
  .It Dv KERN_PROC_CWD Ta "string" Ta "not applicable"
  .It Dv KERN_PROC_NOBROADCASTKILL Ta "node" Ta "not applicable"
  .It Dv KERN_PROC_VMMAP Ta "struct kinfo_vmentry" Ta "no"
  .It Dv KERN_PROF Ta "node" Ta "not applicable"
  .It Dv KERN_RAWPARTITION Ta "integer" Ta "no"
  .It Dv KERN_SAVED_IDS Ta "integer" Ta "no"
  .It Dv KERN_SECURELVL Ta "integer" Ta "raise only"
  .It Dv KERN_SEMINFO Ta "node" Ta "not applicable"
  .It Dv KERN_SHMINFO Ta "node" Ta "not applicable"
  .It Dv KERN_SOMAXCONN Ta "integer" Ta "yes"
  .It Dv KERN_SOMINCONN Ta "integer" Ta "yes"
  .It Dv KERN_SPLASSERT Ta "int" Ta "yes"
  .It Dv KERN_STACKGAPRANDOM Ta "integer" Ta "yes"
  .It Dv KERN_SYSVIPC_INFO Ta "node" Ta "not applicable"
  .It Dv KERN_SYSVMSG Ta "integer" Ta "no"
  .It Dv KERN_SYSVSEM Ta "integer" Ta "no"
  .It Dv KERN_SYSVSHM Ta "integer" Ta "no"
  .It Dv KERN_TIMECOUNTER Ta "node" Ta "not applicable"
  .It Dv KERN_TTY Ta "node" Ta "not applicable"
  .It Dv KERN_TTYCOUNT Ta "integer" Ta "no"
  .It Dv KERN_UTC_OFFSET Ta "integer" Ta "yes"
  .It Dv KERN_VERSION Ta "string" Ta "no"
  .It Dv KERN_VIDEO Ta "node" Ta "yes"
  .It Dv KERN_WATCHDOG Ta "node" Ta "not applicable"
  .It Dv KERN_WITNESS Ta "node" Ta "not applicable"
  .It Dv KERN_WXABORT Ta "integer" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv KERN_ALLOWDT Pq Va kern.allowdt
  Allow userland processes access to
  .Pa /dev/dt .
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Dv KERN_ALLOWKMEM Pq Va kern.allowkmem
  Allow userland processes access to
  .Pa /dev/mem
  and
  .Pa /dev/kmem .
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Dv KERN_ARGMAX Pq Va kern.argmax
  The maximum number of bytes allowed among the arguments to
  .Xr execve 2 .
  .It Dv KERN_AUDIO Pq Va kern.audio
  Control device-independent aspects of the
  .Xr audio 4
  subsystem.
  .Bl -column "KERN_AUDIO_KBDCONTROL" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_AUDIO_RECORD Ta "integer" Ta "yes"
  .It Dv KERN_AUDIO_KBDCONTROL Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_AUDIO_RECORD Pq Va kern.audio.record
  If set to the default value of 0, recording is muted by default
  for all audio devices.
  Otherwise, audio recording is enabled by default.
  For individual devices, this setting can be overridden with the
  .Xr mixerctl 8
  .Va record.enable
  variable.
  .It Dv KERN_AUDIO_KBDCONTROL Pq Va kern.audio.kbdcontrol
  If set to the default value of 1, the
  .Xr wskbd 4
  driver will attempt to adjust the level of the first
  .Xr audio 4
  device when the volume keys of multimedia keyboards are pressed.
  .El
  .It Dv KERN_BOOTTIME Pq Va kern.boottime
  A
  .Vt struct timeval
  structure is returned.
  This structure contains the time that the system was booted.
  .It Dv KERN_CACHEPCT Pq Va kern.bufcachepercent
  The maximum percentage of DMA-reachable physical memory
  the buffer cache may use.
  .It Dv KERN_CCPU Pq Va kern.ccpu
  The scheduler exponential decay value.
  .It Dv KERN_CLOCKRATE Pq Va kern.clockrate
  A
  .Vt struct clockinfo
  structure is returned.
  This structure contains the hard clock, statistics clock and profiling clock
  frequencies, and the number of microseconds per hard clock tick.
  .It Dv KERN_CONSDEV Pq Va kern.consdev
  The console device.
  .It Dv KERN_CPTIME Pq Va kern.cp_time
  An array of longs of size
  .Dv CPUSTATES
  is returned, containing statistics about the number of ticks spent by
  the system in interrupt processing, user processes
  .Po
  .Xr nice 1
  or normal
  .Pc ,
  system processing, lock spinning, or idling.
  .It Dv KERN_CPTIME2 Pq Va kern.cp_time2
  Similar to
  .Dv KERN_CPTIME ,
  but obtains information from only the single CPU specified by the
  third level name given.
  .It Dv KERN_CPUSTATS
  A
  .Vt struct cpustats
  structure is returned.
  This structure contains the array described in
  .Dv KERN_CPTIME2
  and a bit mask indicating the status of the CPU specified by the
  third level name.
  .It Dv KERN_DOMAINNAME Pq Va kern.domainname
  Get or set the YP domain name like with
  .Xr getdomainname 3 ,
  .Xr setdomainname 3 ,
  and
  .Xr domainname 1 .
  .It Dv KERN_FILE Pq Va kern.file
  Return the entire file table, or a subset of it.
  An array of
  .Vt struct kinfo_file
  structures is returned,
  whose size depends on the current number of selected files in the system.
  The third and fourth level names are as follows:
  .Bl -column "Third level name" "Fourth level is:" -offset indent
  .It Sy "Third level name" Ta Sy "Fourth level is:"
  .It Dv KERN_FILE_BYFILE Ta "A file type"
  .It Dv KERN_FILE_BYPID Ta "A process ID"
  .It Dv KERN_FILE_BYUID Ta "A user ID"
  .El
  .Pp
  The fifth level name is the size of the
  .Vt struct kinfo_file
  and the sixth level name is the number of structures to return.
  .It Dv KERN_FORKSTAT Pq Va kern.forkstat
  A
  .Vt struct forkstat
  structure is returned.
  This structure contains information about the number of
  .Xr fork 2 ,
  .Xr vfork 2 ,
  and
  .Xr __tfork 3
  system calls as well as kernel thread creations since system startup,
  and the number of pages of virtual memory involved in each.
  .It Dv KERN_FSCALE Pq Va kern.fscale
  The kernel fixed-point scale factor.
  .It Dv KERN_FSYNC Pq Va kern.fsync
  Return 1 if the File Synchronisation Option is available on this system,
  otherwise 0.
  .It Dv KERN_GLOBAL_PTRACE Pq Va kern.global_ptrace
  When set to 1, permit
  .Xr ptrace 2
  to attach to any process with the appropriate privileges.
  When set to 0, processes may only attach to their own descendants.
  .It Dv KERN_HOSTID Pq Va kern.hostid
  Get or set the host ID.
  .It Dv KERN_HOSTNAME Pq Va kern.hostname
  Get or set the hostname like with
  .Xr gethostname 3 ,
  .Xr sethostname 3 ,
  and
  .Xr hostname 1 .
  .It Dv KERN_JOB_CONTROL Pq Va kern.job_control
  Return 1 if job control is available on this system, otherwise 0.
  .It Dv KERN_MALLOCSTATS Pq Va kern.malloc
  Return kernel memory bucket statistics.
  The third level names are detailed below.
  There are no changeable values in this branch.
  .Bl -column "KERN_MALLOC_KMEMNAMES" "string" -offset indent
  .It Sy "Third level name" Ta Sy "Type"
  .It Dv KERN_MALLOC_BUCKET Ta "node"
  .It Dv KERN_MALLOC_BUCKETS Ta "string"
  .It Dv KERN_MALLOC_KMEMNAMES Ta "string"
  .It Dv KERN_MALLOC_KMEMSTATS Ta "node"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_MALLOC_BUCKET.<size> Pq Va kern.malloc.bucket
  A node containing the statistics for the memory bucket of the
  specified size (in decimal notation, the number of bytes per bucket
  element, e.g., 16, 32, 128).
  Each node returns a
  .Vt struct kmembuckets .
  .Pp
  If a value is specified that does not correspond directly to a
  bucket size, the statistics for the closest larger bucket size will be
  returned instead.
  .Pp
  Note that bucket sizes are typically powers of 2.
  .It Dv KERN_MALLOC_BUCKETS Pq Va kern.malloc.buckets
  Return a comma-separated list of the bucket sizes used by the kernel.
  .It Dv KERN_MALLOC_KMEMNAMES Pq Va kern.malloc.kmemnames
  Return a comma-separated list of the names of the kernel
  .Xr malloc 9
  types.
  .It Dv KERN_MALLOC_KMEMSTATS Pq Va kern.malloc.kmemstat
  A node containing the statistics for the memory types of the specified
  name.
  Each node returns a
  .Vt struct kmemstats .
  .El
  .It Dv KERN_MAXCLUSTERS Pq Va kern.maxclusters
  The maximum number of
  .Xr mbuf 9
  clusters that may be allocated.
  .It Dv KERN_MAXFILES Pq Va kern.maxfiles
  The maximum number of open files that may be open in the system.
  .It Dv KERN_MAXLOCKSPERUID Pq Va kern.maxlocksperuid
  The maximum number of file locks per user;
  the default is 1024.
  .It Dv KERN_MAXPARTITIONS Pq Va kern.maxpartitions
  The maximum number of partitions allowed per disk.
  .It Dv KERN_MAXPROC Pq Va kern.maxproc
  The maximum number of simultaneous processes the system will allow.
  .It Dv KERN_MAXTHREAD Pq Va kern.maxthread
  The maximum number of simultaneous threads the system will allow.
  .It Dv KERN_MAXVNODES Pq Va kern.maxvnodes
  The maximum number of vnodes available on the system.
  .It Dv KERN_MBSTAT Pq Va kern.mbstat
  A
  .Vt struct mbstat
  structure is returned, containing statistics on
  .Xr mbuf 9
  usage.
  .It Dv KERN_MSGBUF Pq Va kern.msgbuf
  Returns a buffer containing kernel log messages;
  see
  .Xr dmesg 8 .
  .It Dv KERN_MSGBUFSIZE Pq Va kern.msgbufsize
  The size of the kernel message buffer.
  .It Dv KERN_NCHSTATS Pq Va kern.nchstats
  A
  .Vt struct nchstats
  structure is returned.
  This structure contains information about the
  filename to
  .Xr inode 5
  mapping cache.
  .It Dv KERN_NFILES Pq Va kern.nfiles
  Number of open files.
  .It Dv KERN_NGROUPS Pq Va kern.ngroups
  The maximum number of supplemental groups.
  .It Dv KERN_NOSUIDCOREDUMP Pq Va kern.nosuidcoredump
  Whether a process may dump core after changing user or group ID:
  .Bl -column "value" "condition" "current directory"
  .It Sy "value" Ta Sy "condition" Ta Sy "dump core to"
  .It 0 Ta "euid == 0" Ta "current directory"
  .It 1 Ta "never" Ta ""
  .It 2 Ta "always" Ta Pa "/var/crash"
  .It 3 Ta "depends" Ta Pa "/var/crash/$programname/"
  .El
  .It Dv KERN_NPROCS Pq Va kern.nprocs
  The number of entries in the kernel process table.
  .It Dv KERN_NTHREADS Pq Va kern.nthreads
  The number of entries in the kernel thread table.
  .It Dv KERN_NUMVNODES Pq Va kern.numvnodes
  Number of vnodes in use.
  .It Dv KERN_OSRELEASE Pq Va kern.osrelease
  The system release string as returned by
  .Xr uname 1
  .Fl r .
  .It Dv KERN_OSREV Pq Va kern.osrevision
  The system revision number.
  .It Dv KERN_OSTYPE Pq Va kern.ostype
  The system type string as returned by
  .Xr uname 1
  .Fl s ;
  it is always
  .Dq Ox .
  .It Dv KERN_OSVERSION Pq Va kern.osversion
  The kernel build version as returned by
  .Xr uname 1
  .Fl v .
  .It Dv KERN_PFSTATUS
  The
  .Vt struct pf_status
  structure.
  .It Dv KERN_POOL_DEBUG Pq Va kern.pool_debug
  Modify the memory pool debug level.
  Valid values are:
  .Pp
  .Bl -tag -width 3n -offset indent -compact
  .It 0
  Disable pool debugging.
  .It 1
  Enable use after free detection.
  .It 2
  In addition to 1, when calling either
  .Xr malloc 9
  or
  .Xr pool_get 9
  with flags indicating that sleeping is allowed then always yield.
  Useful to detect potential races.
  .El
  .It Dv KERN_POSIX1 Pq Va kern.posix1version
  The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
  attempts to comply.
  .It Dv KERN_PROC Pq Va kern.proc
  Return the entire process table, or a subset of it.
  An array of
  .Vt struct kinfo_proc
  structures is returned,
  whose size depends on the current number of selected processes in the system.
  The third and fourth level names are as follows:
  .Bl -column "KERN_PROC_SESSION" "Fourth level is:" -offset indent
  .It Sy "Third level name" Ta Sy "Fourth level is:"
  .It Dv KERN_PROC_ALL Ta "None"
  .It Dv KERN_PROC_KTHREAD Ta "A kernel thread"
  .It Dv KERN_PROC_PID Ta "A process ID"
  .It Dv KERN_PROC_PGRP Ta "A process group"
  .It Dv KERN_PROC_RUID Ta "A real user ID"
  .It Dv KERN_PROC_SESSION Ta "A session PID"
  .It Dv KERN_PROC_TTY Ta "A tty device"
  .It Dv KERN_PROC_UID Ta "A user ID"
  .El
  .Pp
  The fifth level name is the size of the
  .Vt struct kinfo_proc
  and the sixth level name is the number of structures to return.
  .It Dv KERN_PROC_ARGS Pq Va kern.procargs
  Returns the arguments or environment of a process.
  The third level name is the PID of the process.
  The fourth level name is one of:
  .Bl -column KERN_PROC_NARGV -offset indent
  .It Dv KERN_PROC_ARGV
  .It Dv KERN_PROC_ENV
  .It Dv KERN_PROC_NARGV
  .It Dv KERN_PROC_NENV
  .El
  .Pp
  .Dv KERN_PROC_NARGV
  and
  .Dv KERN_PROC_NENV
  return the number of elements as an
  .Vt int
  in the argv or env array.
  .Dv KERN_PROC_ARGV
  returns the argv array and
  .Dv KERN_PROC_ENV
  returns the environ array.
  The buffer pointed to by
  .Fa oldp
  is filled with an array of char pointers
  followed by the strings themselves.
  The last char pointer is a
  .Dv NULL
  pointer.
  .It Dv KERN_PROC_CWD Pq Va kern.proc_cwd
  Return the current working directory of a process.
  The third level name is the target process ID.
  A NUL-terminated string is returned.
  .It Dv KERN_PROC_NOBROADCASTKILL Pq Va kern.proc_nobroadcastkill
  When set, a process will no longer be signaled when sending broadcast signals.
  The third level name is the target process ID.
  .It Dv KERN_PROC_VMMAP Pq Va kern.proc_vmmap
  Return the entire process VM map entries.
  An array of
  .Vt struct kinfo_vmentry
  structures is returned,
  whose size depends on the current number of VM map entries
  of the selected process.
  Iteration is possible by setting the base address in the first element of
  .Vt struct kinfo_vmentry .
  .It Dv KERN_PROF Pq Va kern.profiling
  Return profiling information about the kernel.
  If the kernel is not compiled for profiling,
  attempts to retrieve any of the
  .Dv KERN_PROF
  values will fail with
  .Er EOPNOTSUPP .
  The third level names for the string and integer profiling information
  are detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "Third level name" "struct gmonparam" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv GPROF_COUNT Ta "u_short[]" Ta "yes"
  .It Dv GPROF_FROMS Ta "u_short[]" Ta "yes"
  .It Dv GPROF_GMONPARAM Ta "struct gmonparam" Ta "no"
  .It Dv GPROF_STATE Ta "integer" Ta "yes"
  .It Dv GPROF_TOS Ta "struct tostruct" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv GPROF_COUNT
  Array of statistical program counter counts.
  .It Dv GPROF_FROMS
  Array indexed by program counter of call-from points.
  .It Dv GPROF_GMONPARAM
  Structure giving the sizes of the above arrays.
  .It Dv GPROF_STATE
  Returns
  .Dv GMON_PROF_ON
  or
  .Dv GMON_PROF_OFF
  to show that profiling is running or stopped.
  .It Dv GPROF_TOS
  Array of
  .Vt struct tostruct
  describing destination of calls and their counts.
  .El
  .It Dv KERN_RAWPARTITION Pq Va kern.rawpartition
  The raw partition of a disk (a == 0).
  .It Dv KERN_SAVED_IDS Pq Va kern.saved_ids
  Returns 1 if saved set-group-ID and saved set-user-ID are available.
  .It Dv KERN_SECURELVL Pq Va kern.securelevel
  The system security level.
  This level may be raised by processes with appropriate privileges.
  It may only be lowered by process 1.
  .It Dv KERN_SEMINFO Pq Va kern.seminfo
  Return the elements of
  .Vt struct seminfo .
  If the kernel is not compiled with System V style semaphore support,
  attempts to retrieve any of the
  .Dv KERN_SEMINFO
  values will fail with
  .Er EOPNOTSUPP .
  The third level names for the elements of
  .Vt struct seminfo
  are detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "KERN_SEMINFO_SEMMNI" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_SEMINFO_SEMAEM Ta "integer" Ta "no"
  .It Dv KERN_SEMINFO_SEMMNI Ta "integer" Ta "yes"
  .It Dv KERN_SEMINFO_SEMMNS Ta "integer" Ta "yes"
  .It Dv KERN_SEMINFO_SEMMNU Ta "integer" Ta "yes"
  .It Dv KERN_SEMINFO_SEMMSL Ta "integer" Ta "yes"
  .It Dv KERN_SEMINFO_SEMOPM Ta "integer" Ta "yes"
  .It Dv KERN_SEMINFO_SEMUME Ta "integer" Ta "no"
  .It Dv KERN_SEMINFO_SEMUSZ Ta "integer" Ta "no"
  .It Dv KERN_SEMINFO_SEMVMX Ta "integer" Ta "no"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_SEMINFO_SEMAEM Pq Va kern.seminfo.semaem
  The adjust on exit maximum value.
  .It Dv KERN_SEMINFO_SEMMNI Pq Va kern.seminfo.semmni
  The maximum number of semaphore identifiers allowed.
  .It Dv KERN_SEMINFO_SEMMNS Pq Va kern.seminfo.semmns
  The maximum number of semaphores allowed in the system.
  .It Dv KERN_SEMINFO_SEMMNU Pq Va kern.seminfo.semmnu
  The maximum number of semaphore undo structures allowed in the system.
  .It Dv KERN_SEMINFO_SEMMSL Pq Va kern.seminfo.semmsl
  The maximum number of semaphores allowed per ID.
  .It Dv KERN_SEMINFO_SEMOPM Pq Va kern.seminfo.semopm
  The maximum number of operations per
  .Xr semop 2
  call.
  .It Dv KERN_SEMINFO_SEMUME Pq Va kern.seminfo.semume
  The maximum number of undo entries per process.
  .It Dv KERN_SEMINFO_SEMUSZ Pq Va kern.seminfo.semusz
  The size (in bytes) of the undo structure.
  .It Dv KERN_SEMINFO_SEMVMX Pq Va kern.seminfo.semvmx
  The semaphore maximum value.
  .El
  .It Dv KERN_SHMINFO Pq Va kern.shminfo
  Return the elements of
  .Vt struct shminfo .
  If the kernel is not compiled with System V style shared memory support,
  attempts to retrieve any of the
  .Dv KERN_SHMINFO
  values will fail with
  .Er EOPNOTSUPP .
  The third level names for the elements of
  .Vt struct shminfo
  are detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "KERN_SHMINFO_SHMMAX" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_SHMINFO_SHMALL Ta "integer" Ta "yes"
  .It Dv KERN_SHMINFO_SHMMAX Ta "integer" Ta "yes"
  .It Dv KERN_SHMINFO_SHMMIN Ta "integer" Ta "yes"
  .It Dv KERN_SHMINFO_SHMMNI Ta "integer" Ta "yes"
  .It Dv KERN_SHMINFO_SHMSEG Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_SHMINFO_SHMALL Pq Va kern.shminfo.shmall
  The maximum amount of total shared memory allowed in the system (in pages).
  .It Dv KERN_SHMINFO_SHMMAX Pq Va kern.shminfo.shmmax
  The maximum shared memory segment size (in bytes).
  .It Dv KERN_SHMINFO_SHMMIN Pq Va kern.shminfo.shmmin
  The minimum shared memory segment size (in bytes).
  .It Dv KERN_SHMINFO_SHMMNI Pq Va kern.shminfo.shmmni
  The maximum number of shared memory identifiers in the system.
  .It Dv KERN_SHMINFO_SHMSEG Pq Va kern.shminfo.shmseg
  The maximum number of shared memory segments per process.
  .El
  .It Dv KERN_SOMAXCONN Pq Va kern.somaxconn
  Upper bound on the number of half-open connections a process can allow
  to be associated with a socket, using
  .Xr listen 2 .
  The default value is 128.
  .It Dv KERN_SOMINCONN Pq Va kern.sominconn
  Lower bound on the number of half-open connections a process can allow
  to be associated with a socket, using
  .Xr listen 2 .
  The default value is 80.
  .It Dv KERN_SPLASSERT Pq Va kern.splassert
  Modify the system interrupt priority level.
  Valid values are:
  .Pp
  .Bl -tag -width 3n -offset indent -compact
  .It 0
  Disable error checking.
  .It 1
  Print a message if an error is detected.
  .It 2
  Print a message if an error is detected,
  and a stack trace if possible.
  .It 3
  The same as 2, but also drop into the kernel debugger.
  .El
  .Pp
  Any other value causes a system panic on errors.
  See
  .Xr splassert 9
  for more information.
  .It Dv KERN_STACKGAPRANDOM Pq Va kern.stackgap_random
  Sets the range of the random value added to the stack pointer on each
  program execution.
  The random value is added to make buffer overflow exploitation slightly
  harder.
  The bigger the number, the harder it is to brute force this added protection,
  but it also means bigger waste of memory.
  .It Dv KERN_SYSVIPC_INFO Pq Va kern.sysvipc_info
  Return System V style IPC configuration and run-time information.
  The third level name selects the System V style IPC facility.
  .Bl -column "KERN_SYSVIPC_MSG_INFO" "struct shm_sysctl_info" -offset indent
  .It Sy "Third level name" Ta Sy "Type"
  .It Dv KERN_SYSVIPC_MSG_INFO Ta "struct msg_sysctl_info"
  .It Dv KERN_SYSVIPC_SEM_INFO Ta "struct sem_sysctl_info"
  .It Dv KERN_SYSVIPC_SHM_INFO Ta "struct shm_sysctl_info"
  .El
  .Bl -tag -width "123456"
  .It Dv KERN_SYSVIPC_MSG_INFO
  Return information on the System V style message facility.
  The
  .Sy msg_sysctl_info
  structure is defined in
  .In sys/msg.h .
  .It Dv KERN_SYSVIPC_SEM_INFO
  Return information on the System V style semaphore facility.
  The
  .Sy sem_sysctl_info
  structure is defined in
  .In sys/sem.h .
  .It Dv KERN_SYSVIPC_SHM_INFO
  Return information on the System V style shared memory facility.
  The
  .Sy shm_sysctl_info
  structure is defined in
  .In sys/shm.h .
  .El
  .It Dv KERN_SYSVMSG Pq Va kern.sysvmsg
  Returns 1 if System V style message queue functionality is available on this
  system, otherwise 0.
  .It Dv KERN_SYSVSEM Pq Va kern.sysvem
  Returns 1 if System V style semaphore functionality is available on this
  system, otherwise 0.
  .It Dv KERN_SYSVSHM Pq Va kern.sysvshm
  Returns 1 if System V style shared memory functionality is available on this
  system, otherwise 0.
  .It Dv KERN_TIMECOUNTER Pq Va kern.timecounter
  Return statistics information about the kernel time counter.
  The third level names information is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "KERN_TIMECOUNTER_TIMESTEPWARNINGS" "integer" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_TIMECOUNTER_CHOICE Ta "string" Ta "no"
  .It Dv KERN_TIMECOUNTER_HARDWARE Ta "string" Ta "yes"
  .It Dv KERN_TIMECOUNTER_TICK Ta "integer" Ta "no"
  .It Dv KERN_TIMECOUNTER_TIMESTEPWARNINGS Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_TIMECOUNTER_CHOICE Pq Va kern.timecounter.choice
  Get the list of kernel time counter sources and their claimed
  quality (higher is better).
  .It Dv KERN_TIMECOUNTER_HARDWARE Pq Va kern.timecounter.hardware
  Get or set the kernel time counter source by name.
  .It Dv KERN_TIMECOUNTER_TICK Pq Va kern.timecounter.tick
  Get the number of times we have reset the kernel time counter
  information.
  .It Dv KERN_TIMECOUNTER_TIMESTEPWARNINGS Pq Va kern.timecounter.timestepwarnings
  Get or set a flag to log a message when the kernel time is
  stepped.
  .El
  .It Dv KERN_TTY Pq Va kern.tty
  Return statistics information about tty input/output.
  The third level names information is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "KERN_TTY_TKRAWCC" "struct itty" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_TTY_INFO Ta "struct itty" Ta "no"
  .It Dv KERN_TTY_TKCANCC Ta "int64_t" Ta "no"
  .It Dv KERN_TTY_TKNIN Ta "int64_t" Ta "no"
  .It Dv KERN_TTY_TKNOUT Ta "int64_t" Ta "no"
  .It Dv KERN_TTY_TKRAWCC Ta "int64_t" Ta "no"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_TTY_INFO Pq Va kern.tty.ttyinfo
  Returns an array of
  .Vt struct itty
  structures containing tty statistics.
  .It Dv KERN_TTY_TKCANCC Pq Va kern.tty.tk_cancc
  Returns the number of input characters in canonical mode.
  .It Dv KERN_TTY_TKNIN Pq Va kern.tty.tk_nin
  Returns the number of input characters from a
  .Xr tty 4 .
  .It Dv KERN_TTY_TKNOUT Pq Va kern.tty.tk_nout
  Returns the number of output characters on a
  .Xr tty 4 .
  .It Dv KERN_TTY_TKRAWCC Pq Va kern.tty.tk_rawcc
  Returns the number of input characters in raw mode.
  .El
  .It Dv KERN_TTYCOUNT Pq Va kern.ttycount
  Number of available
  .Xr tty 4
  devices.
  .It Dv KERN_UTC_OFFSET Pq Va kern.utc_offset
  The real-time clock's
  .Pq RTC
  offset from
  Coordinated Universal Time
  .Pq UTC
  expressed as minutes East of UTC+0.
  When set,
  time read from the RTC is adjusted to remove the offset
  and time written to the RTC is adjusted to reapply it.
  This may simplify multibooting with an operating system that
  does not run the RTC in UTC mode.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Dv KERN_VERSION Pq Va kern.version
  The system version string.
  .It Dv KERN_VIDEO Pq Va kern.video
  Control device-independent aspects of the
  .Xr video 4
  subsystem.
  Currently, there is one subnode:
  .Bl -column "KERN_VIDEO_RECORD" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_VIDEO_RECORD Ta "integer" Ta "yes"
  .El
  .Pp
  Its meaning is as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_VIDEO_RECORD Pq Va kern.video.record
  If set to the default value of 0, recording is blanked for all video devices.
  If the value is non-zero, video recording is enabled.
  .El
  .It Dv KERN_WATCHDOG Pq Va kern.watchdog
  Return information on hardware watchdog timers.
  If the kernel does not support a hardware watchdog timer,
  attempts to retrieve or set any of the
  .Dv KERN_WATCHDOG
  values will fail with
  .Er EOPNOTSUPP .
  .Bl -column "KERN_WATCHDOG_PERIOD" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_WATCHDOG_AUTO Ta "integer" Ta "yes"
  .It Dv KERN_WATCHDOG_PERIOD Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_WATCHDOG_AUTO Pq Va kern.watchdog.auto
  If set to 1, the kernel refreshes the watchdog timer periodically.
  If set to 0, a userland process must ensure that the watchdog timer
  gets refreshed by setting the
  .Dv KERN_WATCHDOG_PERIOD
  variable.
  .It Dv KERN_WATCHDOG_PERIOD Pq Va kern.watchdog.period
  The period of the watchdog timer in seconds.
  Set to 0 to disable the watchdog timer.
  .El
  .It Dv KERN_WITNESS Pq Va kern.witness
  Control settings of
  .Xr witness 4 .
  .Bl -column "KERN_WITNESS_LOCKTRACE" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv KERN_WITNESS_LOCKTRACE Ta "integer" Ta "yes"
  .It Dv KERN_WITNESS_WATCH Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Dv KERN_WITNESS_LOCKTRACE Pq Va kern.witness.locktrace
  When set,
  .Xr witness 4
  saves a stack trace on each lock acquisition.
  The stack traces of acquired locks can be viewed using
  .Xr ddb 4 .
  .It Dv KERN_WITNESS_WATCH Pq Va kern.witness.watch
  Control how
  .Xr witness 4
  behaves on error.
  Valid values are:
  .Pp
  .Bl -tag -width 3n -offset indent -compact
  .It -1
  Disable
  .Xr witness 4
  completely.
  System reboot is needed to re-enable it.
  .It 0
  Disable lock order checking.
  .It 1
  Print a message if an error is detected.
  .It 2
  Print a message if an error is detected,
  and a stack trace if possible.
  .It 3
  The same as 2, but also drop into the kernel debugger.
  .El
  .El
  .It Dv KERN_WXABORT Pq Va kern.wxabort
  Generate an abort,
  rather than returning an error,
  on W^X violation.
  .El
  .Ss CTL_MACHDEP
  The set of variables defined is architecture dependent.
  Most architectures define at least the following variables.
  .Bl -column "Second level name" "dev_t" "Changeable" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv CPU_CONSDEV Ta "dev_t" Ta "no"
  .El
  .Pp
  Consult the example file
  .Pa /etc/examples/sysctl.conf
  for a non-exhaustive list of
  .Va machdep
  variables.
  .Ss CTL_NET
  The string and integer information available for the
  .Dv CTL_NET
  level is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "Second level name" "routing messages" "Changeable" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv PF_ROUTE Ta "routing messages" Ta "no"
  .It Dv PF_INET Ta "IPv4 values" Ta "yes"
  .It Dv PF_INET6 Ta "IPv6 values" Ta "yes"
  .It Dv PF_UNIX Ta "UNIX-domain values" Ta "yes"
  .It Dv PF_KEY Ta "key management" Ta "no"
  .It Dv PF_MPLS Ta "MPLS values" Ta "yes"
  .It Dv PF_PIPEX Ta "PIPEX values" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv PF_ROUTE
  Return the entire routing table or a subset of it.
  The data is returned as a sequence of routing messages (see
  .Xr route 4
  for the header file, format, and meaning).
  The length of each message is contained in the message header.
  .Pp
  The third level name is a protocol number, which is currently always 0.
  The fourth level name is an address family, which may be set to 0 to
  select all address families.
  The fifth and sixth level names are as follows:
  .Bl -column "Fifth level name" "Sixth level is:" -offset indent
  .It Sy "Fifth level name" Ta Sy "Sixth level is:"
  .It Dv NET_RT_DUMP Ta "priority"
  .It Dv NET_RT_FLAGS Ta "rtflags"
  .It Dv NET_RT_IFLIST Ta "None"
  .It Dv NET_RT_IFNAMES Ta "None"
  .It Dv NET_RT_STATS Ta "None"
  .It Dv NET_RT_TABLE Ta "rtableid"
  .El
  .Bl -tag -width "123456"
  .It Dv NET_RT_DUMP
  If set to 0, show all routes.
  If set to any number, show all routes with that number priority.
  If set to a negative number, show routes that do not have the positive
  priority value.
  .El
  .Pp
  An optional seventh level name can be provided to select the routing table
  on which to run the operation.
  If not provided, the current routing table is used.
  .It Dv PF_INET
  Get or set various global information about IPv4
  .Pq Internet Protocol version 4 .
  The third level name is the protocol.
  The fourth level name is the variable name.
  The currently defined protocols and names are:
  .Bl -column "Protocol name" "ipsec-expire-acquire" "structure" "Changeable" -offset 2n
  .It Sy "Protocol name" Ta Sy "Variable name" Ta Sy "Type" Ta Sy "Changeable"
  .It ah Ta enable Ta integer Ta yes
  .It bpf Ta bufsize Ta integer Ta yes
  .It bpf Ta maxbufsize Ta integer Ta yes
  .It carp Ta allow Ta integer Ta yes
  .It carp Ta log Ta integer Ta yes
  .It carp Ta preempt Ta integer Ta yes
  .It divert Ta recvspace Ta integer Ta yes
  .It divert Ta sendspace Ta integer Ta yes
  .It esp Ta enable Ta integer Ta yes
  .It esp Ta udpencap Ta integer Ta yes
  .It esp Ta udpencap_port Ta integer Ta yes
  .It etherip Ta allow Ta integer Ta yes
  .It gre Ta allow Ta integer Ta yes
  .It gre Ta wccp Ta integer Ta yes
  .It icmp Ta bmcastecho Ta integer Ta yes
  .It icmp Ta errppslimit Ta integer Ta yes
  .It icmp Ta maskrepl Ta integer Ta yes
  .It icmp Ta rediraccept Ta integer Ta yes
  .It icmp Ta redirtimeout Ta integer Ta yes
  .It icmp Ta stats Ta structure Ta no
  .It icmp Ta tstamprepl Ta integer Ta yes
  .It ip Ta arpqueued Ta integer Ta no
  .It ip Ta arpdown Ta integer Ta yes
  .It ip Ta arptimeout Ta integer Ta yes
  .It ip Ta arpq Ta node Ta "N/A"
  .It ip Ta directed-broadcast Ta integer Ta yes
  .It ip Ta encdebug Ta integer Ta yes
  .It ip Ta forwarding Ta integer Ta yes
  .It ip Ta ipsec-allocs Ta integer Ta yes
  .It ip Ta ipsec-auth-alg Ta string Ta yes
  .It ip Ta ipsec-bytes Ta integer Ta yes
  .It ip Ta ipsec-comp-alg Ta string Ta yes
  .It ip Ta ipsec-enc-alg Ta string Ta yes
  .It ip Ta ipsec-expire-acquire Ta integer Ta yes
  .It ip Ta ipsec-firstuse Ta integer Ta yes
  .It ip Ta ipsec-invalid-life Ta integer Ta yes
  .It ip Ta ipsec-pfs Ta integer Ta yes
  .It ip Ta ipsec-soft-allocs Ta integer Ta yes
  .It ip Ta ipsec-soft-bytes Ta integer Ta yes
  .It ip Ta ipsec-soft-firstuse Ta integer Ta yes
  .It ip Ta ipsec-soft-timeout Ta integer Ta yes
  .It ip Ta ipsec-timeout Ta integer Ta yes
  .It ip Ta maxqueue Ta integer Ta yes
  .It ip Ta mforwarding Ta integer Ta yes
  .It ip Ta mtudisc Ta integer Ta yes
  .It ip Ta mtudisctimeout Ta integer Ta yes
  .It ip Ta multipath Ta integer Ta yes
  .It ip Ta portfirst Ta integer Ta yes
  .It ip Ta porthifirst Ta integer Ta yes
  .It ip Ta porthilast Ta integer Ta yes
  .It ip Ta portlast Ta integer Ta yes
  .It ip Ta redirect Ta integer Ta yes
  .It ip Ta sourceroute Ta integer Ta yes
  .It ip Ta stats Ta structure Ta no
  .It ip Ta ttl Ta integer Ta yes
  .It ipcomp Ta enable Ta integer Ta yes
  .It ipip Ta allow Ta integer Ta yes
  .It tcp Ta ackonpush Ta integer Ta yes
  .It tcp Ta always_keepalive Ta integer Ta yes
  .It tcp Ta baddynamic Ta array Ta yes
  .It tcp Ta ecn Ta integer Ta yes
  .It tcp Ta ident Ta structure Ta no
  .It tcp Ta keepidle Ta integer Ta yes
  .It tcp Ta keepinittime Ta integer Ta yes
  .It tcp Ta keepintvl Ta integer Ta yes
  .It tcp Ta mssdflt Ta integer Ta yes
  .It tcp Ta reasslimit Ta integer Ta yes
  .It tcp Ta rfc1323 Ta integer Ta yes
  .It tcp Ta rfc3390 Ta integer Ta yes
  .It tcp Ta rootonly Ta array Ta yes
  .It tcp Ta rstppslimit Ta integer Ta yes
  .It tcp Ta sack Ta integer Ta yes
  .It tcp Ta stats Ta structure Ta no
  .It tcp Ta synbucketlimit Ta integer Ta yes
  .It tcp Ta syncachelimit Ta integer Ta yes
  .It tcp Ta synhashsize Ta integer Ta yes
  .It tcp Ta synuselimit Ta integer Ta yes
  .It tcp Ta tso Ta integer Ta yes
  .It udp Ta baddynamic Ta array Ta yes
  .It udp Ta checksum Ta integer Ta yes
  .It udp Ta recvspace Ta integer Ta yes
  .It udp Ta rootonly Ta array Ta yes
  .It udp Ta sendspace Ta integer Ta yes
  .It udp Ta stats Ta structure Ta no
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Li ah.enable Pq Va net.inet.ah.enable
  If set to 1, enable the Authentication Header
  .Pq AH
  IPsec protocol.
  Enabled by default.
  See
  .Xr ipsec 4
  for more information.
  .It Li bpf.bufsize Pq Va net.bpf.bufsize
  The initial size of
  .Xr bpf 4
  buffers.
  .It Li bpf.maxbufsize Pq Va net.bpf.maxbufsize
  The maximum size a user may request a
  .Xr bpf 4
  buffer to be.
  .It Li carp.allow Pq Va net.inet.carp.allow
  If set to 0, incoming
  .Xr carp 4
  packets will not be processed.
  If set to any other value, processing will occur.
  Enabled by default.
  .It Li carp.log Pq Va net.inet.carp.log
  Controls the verbosity of
  .Xr carp 4
  logging.
  May be a value between 0 and 7 corresponding with
  .Xr syslog 3
  priorities.
  The default value is 2.
  .It Li carp.preempt Pq Va net.inet.carp.preempt
  If set to 0,
  .Xr carp 4
  will not attempt to become master if it is receiving advertisements from
  another active master.
  If set to any other value, carp will become master of the virtual host if it
  believes it can send advertisements more frequently than the current master.
  Disabled by default.
  .It Li divert.recvspace Pq Va net.inet.divert.recvspace
  Returns the default divert receive buffer size.
  .It Li divert.sendspace Pq Va net.inet.divert.sendspace
  Returns the default divert send buffer size.
  .It Li esp.enable Pq Va net.inet.esp.enable
  If set to 1, enable the Encapsulating Security Payload
  .Pq ESP
  IPsec protocol.
  Enabled by default.
  See
  .Xr ipsec 4
  for more information.
  .It Li esp.udpencap Pq Va net.inet.esp.udpencap
  If set to 1, enable processing of UDP encapsulated ESP packets.
  Enabled by default.
  .It Li esp.udpencap_port Pq Va net.inet.udpencap_port
  Contains the value of the UDP port that triggers
  decapsulation for incoming UDP encapsulated ESP packets.
  The default port is 4500.
  .It Li etherip.allow Pq Va net.inet.etherip.allow
  If set to 0, incoming Ethernet-in-IPv4 packets will not be processed.
  If set to any other value, processing will occur.
  .It Li gre.allow Pq Va net.inet.gre.allow
  If set to 0, incoming GRE packets will not be processed.
  If set to any other value, processing will occur.
  .It Li gre.wccp Pq Va net.inet.gre.wccp
  If set to 0, incoming WCCPv1-style GRE packets will not be processed.
  If set to any other value, and gre.allow allows GRE packet processing,
  WCCPv1-style GRE packets will be processed.
  .It Li icmp.bmcastecho Pq Va net.inet.icmp.bmcastecho
  If set to 1, respond to ICMP echo requests destined for
  broadcast and multicast addresses.
  Note, enabling this could open a system to a type of denial of service attack
  called
  .Qq smurfing ,
  and is thus not advised.
  .It Li icmp.errppslimit Pq Va net.inet.icmp.errppslimit
  This variable specifies the maximum number of outgoing ICMP error messages
  per second.
  ICMP error messages exceeding this value are subject to rate limitation
  and will not go out from the node.
  A negative value disables rate limitation.
  .It Li icmp.maskrepl Pq Va kern.inet.icmp.maskrepl
  Returns 1 if ICMP network mask requests are to be answered.
  .It Li icmp.rediraccept Pq Va kern.inet.icmp.rediraccept
  If set to non-zero, the host will accept ICMP redirect packets.
  Note that routers will never accept ICMP redirect packets,
  and the variable is meaningful on IP hosts only.
  .It Li icmp.redirtimeout Pq Va net.inet.icmp.redrttimeout
  This variable specifies the lifetime of routing entries generated by incoming
  ICMP redirects.
  The default timeout is 10 minutes.
  .It Li icmp.stats Pq Va kern.inet.icmp.stats
  Returns the ICMP statistics in a struct icmpstat.
  .It Li icmp.tstamprepl Pq Va net.inet.icmp.tstamprepl
  If set to 1, reply to ICMP timestamp requests.
  If set to 0, ignore timestamp requests.
  .It Li ip.arpqueued Pq Va net.inet.ip.arpqueued
  Number of packets ARP resolution is holding onto until it gets a MAC
  address for an IP.
  .It Li ip.arpdown Pq Va net.inet.ip.arpdown
  Lifetime of unresolved ARP entries, in seconds.
  .It Li ip.arptimeout Pq Va net.inet.ip.arptimeout
  Lifetime of resolved ARP entries, in seconds.
  .It Li ip.arpq
  Fifth level comprises an array of
  .Vt struct ifqueue
  structures containing information about ARP queue.
  The fifth level names for the elements of
  .Vt struct ifqueue
  are detailed below.
  .Bl -column "Fifth level name" "integer" "Changeable" -offset indent
  .It Sy "Fifth level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv IFQCTL_DROPS Ta "integer" Ta "no"
  .It Dv IFQCTL_LEN Ta "integer" Ta "no"
  .It Dv IFQCTL_MAXLEN Ta "integer" Ta "yes"
  .El
  .Pp
  The variables are as follows:
  .Pp
  .Bl -tag -width Ds -compact
  .It Dv IFQCTL_DROPS Pq Va net.inet.ip.arpq.drops
  Returns number of packet dropped.
  .It Dv IFQCTL_LEN Pq Va net.inet.ip.arpq.len
  Returns the current queue length.
  .It Dv IFQCTL_MAXLEN Pq Va net.inet.ip.arpq.maxlen
  Get or set the maximum number of queue length.
  .El
  .It Li ip.directed-broadcast Pq Va net.inet.ip.directed-broadcast
  Returns 1 if directed broadcast behavior is enabled for the host.
  .It Li ip.encdebug Pq Va net.inet.ip.encdebug
  Returns 1 when error message reporting is enabled for the host.
  If the kernel has been compiled with the
  .Dv ENCDEBUG
  option,
  then debugging information will also be reported when this variable is set.
  .It Li ip.forwarding Pq Va net.inet.ip.forwarding
  If set to 0, IP forwarding is disabled.
  The IP stack also requires the destination IP address of incoming packets
  to match the IP address of the network interface the packet is bound to.
  If set to 1, IP forwarding is enabled for the host,
  indicating the host is acting as a router.
  If set to 2, IP forwarding is restricted to traffic that has been
  IPsec encapsulated or decapsulated by the host.
  Enabling packet forwarding (values either 1 or 2) relaxes the requirements
  on incoming packets,
  so that its destination address must match just any IP address
  bound to the host.
  The default value is 0.
  .It Li ip.ipsec-allocs Pq Va net.inet.ip.ipsec-allocs
  The number of IPsec flows that can use a security association before
  it expires.
  If set to less than or equal to zero, the security association will not
  expire because of this counter.
  The default value is 0.
  .It Li ip.ipsec-auth-alg Pq Va net.inet.ip.ipsec-auth-alg
  This is the default authentication algorithm the kernel will instruct
  key management daemons to negotiate when establishing security
  associations on behalf of the kernel.
  Such security associations can occur as a result of a process having
  requested some security level through
  .Xr setsockopt 2 ,
  or as a result of dynamic VPN entries.
  Supported values are hmac-md5, hmac-sha1, and hmac-ripemd160.
  If set to any other value, it is left to the key management daemons to
  select an authentication algorithm for the security association.
  The default value is hmac-sha1.
  .It Li ip.ipsec-bytes Pq Va net.inet.ip.ipsec-bytes
  The number of bytes that will be processed by a security association
  before it expires.
  If set to less than or equal to zero, the security association will not
  expire because of this counter.
  The default value is 0.
  .It Li ip.ipsec-comp-alg Pq Va net.inet.ip.ipsec-comp-alg
  The compression algorithm to use with an IP Compression Association
  .Pq IPCA .
  Currently the only possible value is
  .Dq deflate .
  .It Li ip.ipsec-enc-alg Pq Va net.inet.ip.ipsec-enc-alg
  This is the default encryption algorithm the kernel will instruct key
  management daemons to negotiate when establishing security
  associations on behalf of the kernel.
  Such security associations can occur as a result of a process having
  requested some security level through
  .Xr setsockopt 2 ,
  or as a result of dynamic VPN entries.
  Supported values are aes, des, 3des, blowfish and cast128.
  If set to any other value, it is left to the key management daemons to
  select an encryption algorithm for the security association.
  The default value is aes.
  .It Li ip.ipsec-expire-acquire Pq Va net.inet.ip.ipsec-expire-acquire
  How long the kernel should allow key management to dynamically acquire
  security associations before re-sending a request.
  The default value is 30 seconds.
  .It Li ip.ipsec-firstuse Pq Va net.inet.ip.ipsec-firstuse
  The number of seconds after a security association is first used before
  it expires.
  If set to less than or equal to zero, the security association will
  not expire because of this timer.
  The default value is 7200 seconds.
  .It Li ip.ipsec-invalid-life Pq Va net.inet.ip.ipsec-invalid-life
  The lifetime of embryonic Security Associations (SAs that key management
  daemons have reserved but not fully established yet) in seconds.
  If set to less than or equal to zero, embryonic SAs will not expire.
  The default value is 60.
  .It Li ip.ipsec-pfs Pq Va net.inet.ip.ipsec-pfs
  If set to any non-zero value, the kernel will ask the key management
  daemons to use Perfect Forward Secrecy when establishing IPsec
  Security Associations.
  Perfect Forward Secrecy makes IPsec Security Associations
  cryptographically distinct from each other, such that breaking the key
  for one such SA does not compromise any others.
  Requiring PFS for every security association significantly increases the
  computational load of
  .Xr isakmpd 8
  exchanges.
  The default value is 1.
  .It Li ip.ipsec-soft-allocs Pq Va net.inet.ip.ipsec-soft-allocs
  The number of IPsec flows that can use a security association before a
  message is sent by the kernel to key management for renegotiation
  of the security association.
  If set to less than or equal to zero, no message is sent to key
  management.
  The default value is 0.
  .It Li ip.ipsec-soft-bytes Pq Va net.inet.ip.ipsec-soft-bytes
  The number of bytes that will be processed by a security association
  before a message is sent by the kernel to key management for
  renegotiation of the security association.
  If set to less than or equal to zero, no message is sent to key
  management.
  The default value is 0.
  .It Li ip.ipsec-soft-firstuse Pq Va net.inet.ip.ipsec-soft-firstuse
  The number of seconds after a security association is first used
  before a message is sent by the kernel to key management for
  renegotiation of the security association.
  If set to less than or equal to zero, no message is sent to key
  management.
  The default value is 3600 seconds.
  .It Li ip.ipsec-soft-timeout Pq Va net.inet.ip.ipsec-soft-timeout
  The number of seconds after a security association is established
  before a message is sent by the kernel to key management for
  renegotiation of the security association.
  If set to less than or equal to zero, no message is sent to key
  management.
  The default value is 80000 seconds.
  .It Li ip.ipsec-timeout Pq Va net.inet.ip.ipsec-timeout
  The number of seconds after a security association is established
  before it will expire.
  If set to less than or equal to zero, the security association will
  not expire because of this timer.
  The default value is 86400 seconds.
  .It Li ip.maxqueue Pq Va net.inet.ip.maxqueue
  Fragment flood protection.
  Sets the maximum number of unassembled IP fragments in the fragment queue.
  .It Li ip.mforwarding Pq Va net.inet.ip.mforwarding
  If set to 1, then multicast forwarding is enabled for the host.
  The default is 0.
  .It Li ip.mtudisc Pq Va net.inet.ip.mtudisc
  Returns 1 if Path MTU Discovery is enabled.
  .It Li ip.mtudisctimeout Pq Va net.inet.ip.mtudisctimeout
  Number of seconds in which a route added by the Path MTU
  Discovery engine will time out.
  When the route times out, the Path MTU Discovery engine will attempt
  to probe a larger path MTU.
  .It Li ip.multipath Pq Va net.inet.ip.multipath
  This variable enables multipath routing for IPv4 addresses.
  If set to 0, only the first route selected will be used for a given
  destination regardless of how many routes exist in the routing table.
  .It Li ip.portfirst Pq Va net.inet.ip.portfirst
  Minimum registered port number for TCP/UDP port allocation.
  Registered ports can be used by ordinary user processes
  or programs executed by ordinary users.
  Cannot be less than 1024 or greater than 49151.
  Must be less than ip.portlast.
  .It Li ip.porthifirst Pq Va net.inet.ip.porthifirst
  Minimum dynamic/private port number for TCP/UDP port allocation.
  Dynamic/private ports can be used by ordinary user processes
  or programs executed by ordinary users.
  Cannot be less than 49152 or greater than 65535.
  Must be less than ip.porthilast.
  .It Li ip.porthilast Pq Va net.inet.ip.porthilast
  Maximum dynamic/private port number for TCP/UDP port allocation.
  Dynamic/private ports can be used by ordinary user processes
  or programs executed by ordinary users.
  Cannot be less than 49152 or greater than 65535.
  Must be greater than ip.porthifirst.
  .It Li ip.portlast Pq Va net.inet.ip.portlast
  Maximum registered port number for TCP/UDP port allocation.
  Registered ports can be used by ordinary user processes
  or programs executed by ordinary users.
  Cannot be less than 1024 or greater than 49151.
  Must be greater than ip.portfirst.
  .It Li ip.redirect Pq Va net.inet.ip.redirect
  Returns 1 when ICMP redirects may be sent by the host.
  This option is ignored unless the host is routing IP packets,
  and should normally be enabled on all systems.
  .It Li ip.sourceroute Pq Va net.inet.ip.sourceroute
  Returns 1 when forwarding of source-routed packets is enabled for
  the host.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Li ip.stats Pq Va net.inet.ip.stats
  Returns the IP statistics in a struct ipstat.
  .It Li ip.ttl Pq Va net.inet.ip.ttl
  The maximum time-to-live (hop count) value for an IP packet
  sourced by the system.
  This value applies to normal transport protocols, not to ICMP.
  .It Li ipcomp.enable Pq Va net.inet.ipcomp.enable
  Enable the IPComp protocol.
  See
  .Xr ipcomp 4
  for more information.
  .It Li ipip.allow Pq Va net.inet.ipip.allow
  If set to 0, incoming IP-in-IP packets will not be processed.
  If set to any other value, processing will occur; furthermore, if set
  to 2, no checks for spoofing of loopback addresses will be done.
  This is useful only for debugging purposes, and should never be used
  in production systems.
  .It Li tcp.ackonpush Pq Va net.inet.tcp.ackonpush
  Returns 1 if TCP segments with the
  .Dv TH_PUSH
  flag set are being acknowledged immediately, otherwise 0.
  .It Li tcp.baddynamic Pq Va net.inet.tcp.baddynamic
  An array of
  .Vt in_port_t
  is returned specifying the bitmask of TCP ports between 512
  and 1023 inclusive that should not be allocated dynamically
  by the kernel (i.e., they must be bound specifically by port number).
  .It Li tcp.ecn Pq Va net.inet.tcp.ecn
  Returns 1 if Explicit Congestion Notifications for TCP are enabled.
  .It Li tcp.ident Pq Va net.inet.tcp.ident
  A
  .Vt struct tcp_ident_mapping
  specifying a local and foreign endpoint of a TCP
  socket is filled in with the effective and real UIDs of the process that
  owns the socket.
  If no such socket exists, then the effective and real UID values are
  both set to \-1.
  .It Li tcp.keepidle Pq Va net.inet.tcp.keepidle
  If the socket option
  .Dv SO_KEEPALIVE
  has been set on a socket, then this value specifies how much time in seconds
  a connection needs to be idle before keepalives are sent.
  .It Li tcp.keepinittime Pq Va net.inet.tcp.keepinittime
  Time in seconds to keep alive the initial SYN packet of a TCP handshake.
  .It Li tcp.keepintvl Pq Va net.inet.tcp.keepintvl
  Time in seconds after a keepalive probe is sent until, in the absence of any
  response, another probe is sent.
  .It Li tcp.always_keepalive Pq Va net.inet.tcp.always_keepalive
  Act as if the option
  .Dv SO_KEEPALIVE
  was set on all TCP sockets.
  .It Li tcp.mssdflt Pq Va net.inet.tcp.mssdflt
  The maximum segment size that is used as default for non-local connections.
  The default value is 512.
  .It Li tcp.reasslimit Pq Va net.inet.tcp.reasslimit
  The maximum number of out-of-order TCP
  segments the system will store for reassembly.
  .It Li tcp.rfc1323 Pq Va net.inet.tcp.rfc1323
  Returns 1 if RFC 1323 extensions to TCP are enabled.
  .It Li tcp.rfc3390 Pq Va net.inet.tcp.rfc3390
  Returns 1 if the TCP Initial Window
  is increased to 4 * MSS or 4380 bytes, as specified in RFC 3390.
  Returns 2 if the TCP Initial Window
  is increased to 10 * MSS or 14600 bytes, as specified in
  RFC 6928.
  .It Li tcp.rootonly Pq Va net.inet.tcp.rootonly
  An array of
  .Vt in_port_t
  is returned specifying the bitmask of TCP ports
  that can only be bound by processes with root euid.
  When running with a
  .Xr securelevel 7
  greater than 0,
  this variable may not be changed.
  .It Li tcp.rstppslimit Pq Va net.inet.tcp.rstppslimit
  This variable specifies the maximum number of outgoing TCP RST packets
  per second.
  TCP RST packets exceeding this value are subject to rate limitation
  and will not go out from the node.
  A negative value disables rate limitation.
  .It Li tcp.sack Pq Va net.inet.tcp.sack
  Returns 1 if RFC 2018 Selective Acknowledgements are enabled.
  .It Li tcp.stats Pq Va net.inet.tcp.stats
  Returns the TCP statistics in a struct tcpstat.
  .It Li tcp.synbucketlimit Pq Va net.inet.tcp.synbucketlimit
  The maximum number of entries allowed per hash bucket in the TCP SYN cache.
  .It Li tcp.syncachelimit Pq Va net.inet.tcp.syncachelimit
  The maximum number of entries allowed in the TCP SYN cache.
  .It Li tcp.synhashsize Pq Va net.inet.tcp.synhashsize
  The number of buckets in the TCP SYN cache hash array.
  After the value is set, the actual size changes when the alternative
  SYN cache becomes empty and both SYN caches are swapped.
  .It Li tcp.synuselimit Pq Va net.inet.tcp.synuselimit
  The minimum number of times the hash function for the TCP SYN cache is used
  before it is reseeded.
  .It Li tcp.tso Pq Va net.inet.tcp.tso
  If set to 0, disable TCP segmentation offload (TSO).
  If set to 1, TSO is enabled (the default).
  .It Li udp.baddynamic Pq Va net.inet.udp.baddynamic
  Analogous to
  .Li tcp.baddynamic
  but for UDP sockets.
  .It Li udp.checksum Pq Va net.inet.udp.checksum
  Returns 1 when UDP checksums are being computed and checked.
  Disabling UDP checksums is strongly discouraged.
  .It Li udp.recvspace Pq Va net.inet.udp.recvspace
  Returns the default UDP receive buffer size.
  .It Li udp.rootonly Pq Va net.inet.udp.rootonly
  Analogous to
  .Li tcp.rootonly
  but for UDP sockets.
  .It Li udp.sendspace Pq Va net.inet.udp.sendspace
  Returns the default UDP send buffer size.
  .It Li udp.stats Pq Va net.inet.udp.stats
  Returns the UDP statistics in a struct udpstat.
  .El
  .It Dv PF_INET6
  Get or set various global information about IPv6
  .Pq Internet Protocol version 6 .
  The third level name is the protocol.
  The fourth level name is the variable name.
  The currently defined protocols and names are:
  .Bl -column "Protocol name" "multicast_mtudisc" "integer" "yes" -offset indent
  .It Sy "Protocol name" Ta Sy "Variable name" Ta Sy "Type" Ta Sy "Changeable"
  .It icmp6 Ta errppslimit Ta integer Ta yes
  .It icmp6 Ta mtudisc_hiwat Ta integer Ta yes
  .It icmp6 Ta mtudisc_lowat Ta integer Ta yes
  .It icmp6 Ta nd6_delay Ta integer Ta yes
  .It icmp6 Ta nd6_mmaxtries Ta integer Ta yes
  .It icmp6 Ta nd6_umaxtries Ta integer Ta yes
  .It icmp6 Ta redirtimeout Ta integer Ta yes
  .It ip6 Ta dad_count Ta integer Ta yes
  .It ip6 Ta dad_pending Ta integer Ta yes
  .It ip6 Ta defmcasthlim Ta integer Ta yes
  .It ip6 Ta forwarding Ta integer Ta yes
  .It ip6 Ta hdrnestlimit Ta integer Ta yes
  .It ip6 Ta hlim Ta integer Ta yes
  .It ip6 Ta maxdynroutes Ta integer Ta yes
  .It ip6 Ta maxfragpackets Ta integer Ta yes
  .It ip6 Ta maxfrags Ta integer Ta yes
  .It ip6 Ta mforwarding Ta integer Ta yes
  .It ip6 Ta mtudisctimeout Ta integer Ta yes
  .It ip6 Ta multicast_mtudisc Ta integer Ta yes
  .It ip6 Ta multipath Ta integer Ta yes
  .It ip6 Ta neighborgcthresh Ta integer Ta yes
  .It ip6 Ta redirect Ta integer Ta yes
  .El
  .Pp
  The variables are as follows:
  .Pp
  .Bl -tag -width "123456" -compact
  .It Li icmp6.errppslimit Pq Va net.inet6.icmp6.errppslimit
  This variable specifies the maximum number of outgoing ICMPv6 error messages
  per second.
  ICMPv6 error messages exceeding this value are subject to rate limitation
  and will not go out from the node.
  A negative value will disable the rate limitation.
  .Pp
  .It Li icmp6.mtudisc_hiwat Pq Va net.inet6.icmp6.mtudisc_hiwat
  .It Li icmp6.mtudisc_lowat Pq Va net.inet6.icmp6.mtudisc_lowat
  These variables define the maximum number of routing table entries
  created due to path MTU discovery
  .Pq preventing denial-of-service attacks with ICMPv6 too big messages .
  After IPv6 path MTU discovery happens, path MTU information is kept in
  the routing table.
  If the number of routing table entries exceeds this value,
  the kernel will not attempt to keep the path MTU information.
  .Li icmp6.mtudisc_hiwat
  is used when we have verified ICMPv6 too big messages.
  .Li icmp6.mtudisc_lowat
  is used when we have unverified ICMPv6 too big messages.
  Verification is performed by using address/port pairs kept in connected PCBs.
  A negative value disables the upper limit.
  .Pp
  .It Li icmp6.nd6_delay Pq Va net.inet6.icmp6.nd6_delay
  This variable specifies the
  .Dv DELAY_FIRST_PROBE_TIME
  timing constant in IPv6 neighbor discovery specification
  .Pq RFC 4861 ,
  in seconds.
  .Pp
  .It Li icmp6.nd6_mmaxtries Pq Va net.inet6.icmp6.nd6_mmaxtries
  This variable specifies the
  .Dv MAX_MULTICAST_SOLICIT
  constant in IPv6 neighbor discovery specification
  .Pq RFC 4861 .
  .Pp
  .It Li icmp6.nd6_umaxtries Pq Va net.inet6.icmp6.nd6_umaxtries
  This variable specifies the
  .Dv MAX_UNICAST_SOLICIT
  constant in IPv6 neighbor discovery specification
  .Pq RFC 4861 .
  .Pp
  .It Li icmp6.redirtimeout Pq Va net.inet6.icmp6.redirtimeout
  The variable specifies the lifetime of routing entries generated by
  incoming ICMPv6 redirects.
  .Pp
  .It Li ip6.dad_count Pq Va net.inet6.ip6.dad_count
  This variable configures the number of IPv6 DAD
  .Pq duplicated address detection
  probe packets.
  These packets are generated when IPv6 interfaces are first brought up.
  .Pp
  .It Li ip6.dad_pending Pq Va net.inet6.ip6.dad_pending
  This variable displays the number of pending IPv6 DAD
  .Pq duplicated address detection
  before completion.
  It is used to make sure that DAD is completed before
  .Xr netstart 8
  is executed.
  .Pp
  .It Li ip6.defmcasthlim Pq Va net.inet6.ip6.defmcasthlim
  The default hop limit value for an IPv6 multicast packet sourced by the node.
  This value applies to all the transport protocols on top of IPv6.
  Methods for overriding this value are documented in
  .Xr ip6 4 .
  .Pp
  .It Li ip6.forwarding Pq Va net.inet6.ip6.forwarding
  Returns 1 when IPv6 forwarding is enabled for the node,
  meaning that the node is acting as a router.
  Returns 0 when IPv6 forwarding is disabled for the node,
  meaning that the node is acting as a host.
  Note that IPv6 defines node behavior for the
  .Dq router
  and
  .Dq host
  cases quite differently, and changing this variable during operation
  may cause serious trouble.
  Hence, this variable should only be set at bootstrap time.
  As with IPv4, if forwarding is disabled then the destination address of
  incoming packets must match the IP address bound to the interface.
  If forwarding is enabled, the check is relaxed
  so that the destination IP address of incoming packets must match
  just any address bound to the host.
  .Pp
  .It Li ip6.hdrnestlimit Pq Va net.inet6.ip6.hdrnestlimit
  The number of IPv6 extension headers permitted on incoming IPv6 packets.
  If set to 0, the node will accept as many extension headers as possible.
  .Pp
  .It Li ip6.hlim Pq Va net.inet6.ip6.hlim
  The default hop limit value for an IPv6 unicast packet sourced by the node.
  This value applies to all the transport protocols on top of IPv6.
  Methods for overriding this value are documented in
  .Xr ip6 4 .
  .Pp
  .It Li ip6.maxdynroutes Pq Va net.inet6.ip6.maxdynroutes
  Maximum number of routes created by redirect.
  Set to negative to disable.
  The default value is 4096.
  .Pp
  .It Li ip6.maxfragpackets Pq Va net.inet6.ip6.maxfragpackets
  The maximum number of fragmented packets the node will accept.
  0 means that the node will not accept any fragmented packets.
  \-1 means that the node will accept as many fragmented packets as it receives.
  The flag is provided basically for avoiding possible DoS attacks.
  .Pp
  .It Li ip6.maxfrags Pq Va net.inet6.ip6.maxfrags
  The maximum number of fragments the node will accept.
  0 means that the node will not accept any fragments.
  \-1 means that the node will accept as many fragments as it receives.
  The flag is provided basically for avoiding possible DoS attacks.
  .Pp
  .It Li ip6.mforwarding Pq Va net.inet6.ip6.mforwarding
  If set to 1, then multicast forwarding is enabled for the host.
  The default is 0.
  .Pp
  .It Li ip6.multicast_mtudisc Pq Va net.inet6.ip6.multicast_mtudisc
  This variable controls generation of ICMPv6 Too Big messages
  when the machine is performing as an IPv6 multicast router.
  If set to 1, an ICMPv6 Too Big message will be generated for multicast packets
  which were too big to be forwarded.
  If set to 0, the ICMPv6 Too Big message will be suppressed.
  .Pp
  .It Li ip6.multipath Pq Va net.inet6.ip6.multipath
  This variable enables multipath routing for IPv6 addresses.
  If set to 0, only the first route selected will be used for a given
  destination regardless of how many routes exist in the routing table.
  .Pp
  .It Li ip6.mtudisctimeout Pq Va net.inet6.ip6.mtudisctimeout
  Number of seconds in which a route added by the Path MTU
  Discovery engine will time out.
  When the route times out, the Path MTU Discovery engine will attempt
  to probe a larger path MTU.
  .Pp
  .It Li ip6.neighborgcthresh Pq Va net.inet6.ip6.neighborgcthresh
  Maximum number of entries in neighbor cache.
  Set to negative to disable.
  The default value is 2048.
  .Pp
  .It Li ip6.redirect Pq Va net.inet6.ip6.redirect
  Returns 1 when ICMPv6 redirects may be sent by the node.
  This option is ignored unless the node is routing IP packets,
  and should normally be enabled on all systems.
  .El
  .Pp
  We reuse
  .Li net.inet.tcp
  and
  .Li net.inet.udp
  for TCP/UDP over IPv6.
  .It Dv PF_UNIX
  Get or set various global information about UNIX-domain protocol family.
  The third level name is the socket type.
  The fourth level name is the variable name.
  The currently defined socket types and names are:
  .Bl -column "Protocol name" "ipsec-expire-acquire" "structure" "Changeable" -offset 2n
  .It Sy "Socket type" Ta Sy "Variable name" Ta Sy "Type" Ta Sy "Changeable"
  .It stream Ta recvspace Ta integer Ta yes
  .It stream Ta sendspace Ta integer Ta yes
  .It dgram Ta recvspace Ta integer Ta yes
  .It dgram Ta sendspace Ta integer Ta yes
  .It seqpacket Ta recvspace Ta integer Ta yes
  .It seqpacket Ta sendspace Ta integer Ta yes
  .It inflight Ta Ta integer Ta no
  .It deferred Ta Ta integer Ta no
  .El
  .Pp
  The variables are as follows:
  .Bl -tag -width "123456"
  .It Li stream.recvspace Pq Va net.unix.stream.recvspace
  Returns the default
  .Dv SOCK_STREAM
  receive buffer size.
  .It Li stream.sendspace Pq Va net.unix.stream.sendspace
  Returns the default
  .Dv SOCK_STREAM
  send buffer size.
  .It Li dgram.recvspace Pq Va net.unix.dgram.recvspace
  Returns the default
  .Dv SOCK_DGRAM
  receive buffer size.
  .It Li dgram.sendspace Pq Va net.unix.dgram.sendspace
  Returns the default
  .Dv SOCK_DGRAM
  send buffer size.
  .It Li seqpacket.recvspace Pq Va net.unix.seqpacket.recvspace
  Returns the default
  .Dv SOCK_SEQPACKET
  receive buffer size.
  .It Li seqpacket.sendspace Pq Va net.unix.seqpacket.sendspace
  Returns the default
  .Dv SOCK_SEQPACKET
  send buffer size.
  .It Li inflight Pq Va net.unix.inflight
  Returns the number of file descriptors inflight.
  .It Li deferred Pq Va net.unix.deferred
  Returns the number of file descriptors to be closed.
  .El
  .It Dv PF_KEY
  Return
  .Xr ipsec 4
  database dumps.
  The second level name is
  .Dv PF_KEY_V2 .
  The third level name selects the database as follows:
  .Pp
  .Bl -tag -width "NET_KEY_SADB_DUMP" -offset indent -compact
  .It Dv NET_KEY_SADB_DUMP
  Security Association database (SADB).
  .It Dv NET_KEY_SPD_DUMP
  IPsec flow database (SPD).
  .El
  .It Dv PF_MPLS
  Get or set global information about MPLS (Multiprotocol Label Switching).
  .Bl -column "MPLSCTL_MAPTTL_IP6 " "integer" "not applicable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv MPLSCTL_DEFTTL Ta integer Ta yes
  .It Dv MPLSCTL_MAPTTL_IP Ta integer Ta yes
  .It Dv MPLSCTL_MAPTTL_IP6 Ta integer Ta yes
  .El
  .Bl -tag -width "123456"
  .It Dv MPLSCTL_DEFTTL Pq Va net.mpls.ttl
  Set or get the default TTL value which is used for MPLS (Shim) Header.
  The default is 255.
  .It Dv MPLSCTL_MAPTTL_IP Pq Va net.mpls.mapttl_ip
  If set to 1, the TTL field is synchronized between the IP header and the
  MPLS label stack.
  If set to 0, the IP header TTL is not modified while passing through MPLS
  and the MPLS label stack is initialized with the
  .Dv MPLSCTL_DEFTTL .
  The default is 1.
  .It Dv MPLSCTL_MAPTTL_IP6 Pq Va net.mpls.mapttl_ip6
  If set to 1, the TTL field is synchronized between the IPv6 header and the
  MPLS label stack.
  If set to 0, the IPv6 header TTL is not modified while passing through MPLS
  and the MPLS label stack is initialized with the
  .Dv MPLSCTL_DEFTTL .
  The default is 0.
  .El
  .It Dv PF_PIPEX Pq Va net.pipex
  Get or set global information about PIPEX.
  .Pp
  The currently defined variable names are:
  .Bl -column "Third level name" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv PIPEXCTL_ENABLE Ta integer Ta yes
  .El
  .Bl -tag -width "123456"
  .It Dv PIPEXCTL_ENABLE
  If set to 1, enable PIPEX processing.
  The default is 0.
  .El
  .El
  .Ss CTL_VFS
  The string and integer information available for the
  .Dv CTL_VFS
  level is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "Second level name" "VFS generic info" "Changeable" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv VFS_GENERIC Ta "VFS generic info" Ta "no"
  .It Dv "filesystem #" Ta "filesystem info" Ta "no"
  .El
  .Bl -tag -width "123456"
  .It Dv VFS_GENERIC
  This second level identifier requests generic information about the
  VFS layer.
  Within it, the following third level identifiers exist:
  .Bl -column "Third level name" "struct vfsconf" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv VFS_CONF Ta "struct vfsconf" Ta "no"
  .It Dv VFS_MAXTYPENUM Ta "int" Ta "no"
  .El
  .It filesystem #
  After finding the filesystem dependent
  .Va vfc_typenum
  using
  .Dv VFS_GENERIC
  with
  .Dv VFS_CONF ,
  it is possible to access filesystem dependent information.
  .Pp
  Some filesystems may contain settings.
  .Bl -tag -width "123"
  .It FFS
  .Bl -column "FFS_SD_DIRECT_BLK_PTRS" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv FFS_DIRHASH_DIRSIZE Ta "integer" Ta "yes"
  .It Dv FFS_DIRHASH_MAXMEM Ta "integer" Ta "yes"
  .It Dv FFS_DIRHASH_MEM Ta "integer" Ta "no"
  .It Dv FFS_MAX_SOFTDEPS Ta "integer" Ta "yes"
  .It Dv FFS_SD_BLK_LIMIT_HIT Ta "integer" Ta "yes"
  .It Dv FFS_SD_BLK_LIMIT_PUSH Ta "integer" Ta "yes"
  .It Dv FFS_SD_DIR_ENTRY Ta "integer" Ta "yes"
  .It Dv FFS_SD_DIRECT_BLK_PTRS Ta "integer" Ta "yes"
  .It Dv FFS_SD_INDIR_BLK_PTRS Ta "integer" Ta "yes"
  .It Dv FFS_SD_INO_LIMIT_HIT Ta "integer" Ta "yes"
  .It Dv FFS_SD_INO_LIMIT_PUSH Ta "integer" Ta "yes"
  .It Dv FFS_SD_INODE_BITMAP Ta "integer" Ta "yes"
  .It Dv FFS_SD_SYNC_LIMIT_HIT Ta "integer" Ta "yes"
  .It Dv FFS_SD_TICKDELAY Ta "integer" Ta "yes"
  .It Dv FFS_SD_WORKLIST_PUSH Ta "integer" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv FFS_DIRHASH_DIRSIZE Pq Va vfs.ffs.dirhash_dirsize
  The minimum size of a directory, in bytes, before it is considered for hashing.
  .It Dv FFS_DIRHASH_MAXMEM Pq Va vfs.ffs.dirhash_maxmem
  The maximum amount of memory, in bytes, to be used for storing directory
  hashes.
  .It Dv FFS_DIRHASH_MEM Pq Va vfs.ffs.dirhash_mem
  The amount of memory currently used by all directory hashes.
  .It Dv FFS_MAX_SOFTDEPS Pq Va vfs.ffs.max_softdeps
  Maximum structures before slowdowns.
  .It Dv FFS_SD_BLK_LIMIT_HIT Pq Va vfs.ffs.sd_blk_limit_hit
  Number of times block slowdown imposed.
  .It Dv FFS_SD_BLK_LIMIT_PUSH Pq Va vfs.ffs.sd_blk_limit_push
  Number of times block limit neared.
  .It Dv FFS_SD_DIR_ENTRY Pq Va vfs.ffs.sd_dir_entry
  Bufs redirtied as dir entry cannot write.
  .It Dv FFS_SD_DIRECT_BLK_PTRS Pq Va vfs.ffs.sd_direct_blk_ptrs
  Bufs redirtied as direct ptrs not written.
  .It Dv FFS_SD_INDIR_BLK_PTRS Pq Va vfs.ffs.sd_indir_blk_ptrs
  Bufs redirtied as indirect ptrs not written.
  .It Dv FFS_SD_INO_LIMIT_HIT Pq Va vfs.ffs.sd_ino_limit_hit
  Number of times inode limit imposed.
  .It Dv FFS_SD_INO_LIMIT_PUSH Pq Va vfs.ffs.sd_ino_limit_push
  Number of times inode limit neared.
  .It Dv FFS_SD_INODE_BITMAP Pq Va vfs.ffs.sd_inode_bitmap
  Bufs redirtied as inode bitmap not written.
  .It Dv FFS_SD_SYNC_LIMIT_HIT Pq Va vfs.ffs.sd_sync_limit_hit
  Number of synchronous slowdowns imposed.
  .It Dv FFS_SD_TICKDELAY Pq Va vfs.ffs.sd_tickdelay
  Ticks to pause during slowdown.
  .It Dv FFS_SD_WORKLIST_PUSH Pq Va vfs.ffs.sd_worklist_push
  Number of worklist cleanups.
  .El
  .It NFS
  .Bl -column "Third level name" "struct nfsstats" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv NFS_NFSSTATS Ta "struct nfsstats" Ta "yes"
  .It Dv NFS_NIOTHREADS Ta "int" Ta "yes"
  .El
  .Bl -tag -width Ds
  .It Dv NFS_NIOTHREADS Pq Va vfs.nfs.iothreads
  The number of I/O kernel threads for NFS clients.
  The default is 4;
  the maximum is 20.
  .El
  .It FUSE
  .Bl -column "FUSEFS_POOL_NBPAGES" "Type" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv FUSEFS_INFBUFS Ta "int" Ta "no"
  .It Dv FUSEFS_OPENDEVS Ta "int" Ta "no"
  .It Dv FUSEFS_POOL_NBPAGES Ta "int" Ta "no"
  .It Dv FUSEFS_WAITFBUFS Ta "int" Ta "no"
  .El
  .Bl -tag -width Ds
  .It Dv FUSEFS_INFBUFS Pq Va vfs.fuse.fusefs_fbufs_in
  The number of inbound fusebufs.
  .It Dv FUSEFS_OPENDEVS Pq Va vfs.fuse.fusefs_open_devices
  The number of FUSE devices opened.
  .It Dv FUSEFS_POOL_NBPAGES Pq Va vfs.fuse.fusefs_pool_pages
  The number of pages used for fusebuf memory.
  .It Dv FUSEFS_WAITFBUFS Pq Va vfs.fuse.fusefs_fbufs_wait
  The number of fusebufs waiting for a response.
  .El
  .El
  .El
  .Ss CTL_VM
  The string and integer information available for the
  .Dv CTL_VM
  level is detailed below.
  The changeable column shows whether a process with appropriate
  privileges may change the value.
  .Bl -column "Second level name" "swap encrypt values" "yes" -offset indent
  .It Sy "Second level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv VM_ANONMIN Ta "integer" Ta "yes"
  .It Dv VM_LOADAVG Ta "struct loadavg" Ta "no"
  .It Dv VM_MALLOC_CONF Ta "string" Ta "yes"
  .It Dv VM_MAXSLP Ta "integer" Ta "no"
  .It Dv VM_METER Ta "struct vmtotal" Ta "no"
  .It Dv VM_NKMEMPAGES Ta "integer" Ta "no"
  .It Dv VM_PSSTRINGS Ta "struct psstrings" Ta "no"
  .It Dv VM_SWAPENCRYPT Ta "swap encrypt values" Ta "yes"
  .It Dv VM_USPACE Ta "integer" Ta "no"
  .It Dv VM_UVMEXP Ta "struct uvmexp" Ta "no"
  .It Dv VM_VNODEMIN Ta "integer" Ta "yes"
  .It Dv VM_VTEXTMIN Ta "integer" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv VM_ANONMIN Pq Va vm.anonmin
  Percentage of physical memory available for
  pages which contain anonymous mapping.
  .It Dv VM_LOADAVG Pq Va vm.loadavg
  Return the load average history.
  The returned data consists of a
  .Vt struct loadavg .
  .It Dv VM_MALLOC_CONF Pq Va vm.malloc_conf
  String of option flags for the
  .Xr malloc 3
  family of functions
  which will be applied to all programs starting in the future.
  The string contains a maximum of 15 characters.
  .It Dv VM_MAXSLP Pq Va vm.maxslp
  The time for a process to be blocked before being swappable,
  in seconds.
  .It Dv VM_METER Pq Va vm.vmmeter
  Return the system wide virtual memory statistics.
  The returned data consists of a
  .Vt struct vmtotal .
  .It Dv VM_NKMEMPAGES Pq Va vm.nkmempages
  Number of pages in kmem_map.
  .It Dv VM_PSSTRINGS Pq Va vm.psstrings
  Returns the address of the process
  .Vt struct ps_strings .
  The
  .Xr ps 1
  program uses it to locate the argument and environment strings.
  .It Dv VM_SWAPENCRYPT
  Contains statistics about swap encryption.
  The string and integer information available for the third level is
  detailed below.
  .Bl -column "Third level name" "integer" "Changeable" -offset indent
  .It Sy "Third level name" Ta Sy "Type" Ta Sy "Changeable"
  .It Dv SWPENC_CREATED Ta "integer" Ta "no"
  .It Dv SWPENC_DELETED Ta "integer" Ta "no"
  .It Dv SWPENC_ENABLE Ta "integer" Ta "yes"
  .El
  .Bl -tag -width "123456"
  .It Dv SWPENC_CREATED Pq Va vm.swapencrypt.keyscreated
  The number of encryption keys that have been randomly created.
  The swap partition is divided into sections of normally 512KB.
  Each section has its own encryption key.
  .It Dv SWPENC_DELETED Pq Va vm.swapencrypt.keysdeleted
  The number of encryption keys that have been deleted, thus effectively
  erasing the data that has been encrypted with them.
  Encryption keys are deleted when their reference counter reaches zero.
  .It Dv SWPENC_ENABLE Pq Va vm.swapencrypt.enable
  Set to 1 to enable swap encryption for all processes.
  A 0 disables swap encryption.
  Turning this option on does not affect swap data already on the disk,
  but all newly written data will be encrypted.
  When swap encryption is turned on, automatic
  .Xr crash 8
  dumps are disabled.
  .El
  .It Dv VM_USPACE Pq Va vm.uspace
  The number of bytes allocated for each kernel stack.
  .It Dv VM_UVMEXP Pq Va vm.uvmexp
  Contains statistics about the UVM memory management system.
  .It Dv VM_VNODEMIN Pq Va vm.vnodemin
  Percentage of physical memory available for
  pages which contain cached file data.
  .It Dv VM_VTEXTMIN Pq Va vm.vtextmin
  Percentage of physical memory available for
  pages which contain cached executable data.
  .El
  .Sh RETURN VALUES
  If the call to
  .Fn sysctl
  is unsuccessful, \-1 is returned and
  .Va errno
  is set appropriately.
  .Sh FILES
  .Bl -tag -width "uvm/uvmXswapXencrypt.h  " -compact
  .It In sys/sysctl.h
  top level identifiers and second level kernel and hardware
  identifiers
  .It In sys/socket.h
  second level network identifiers
  .It In sys/gmon.h
  third level profiling identifiers
  .It In uvm/uvmexp.h
  second level virtual memory identifiers
  .It In uvm/uvm_swap_encrypt.h
  third level virtual memory identifiers
  .It In net/if.h
  packet input/output queue identifiers
  .It In net/pipex.h
  third level PIPEX identifiers
  .It In netinet/in.h
  third and fourth level IPv4/v6 identifiers
  .It In netinet/ip_divert.h
  fourth level divert identifiers
  .It In netinet/icmp_var.h
  fourth level ICMP identifiers
  .It In netinet/icmp6.h
  fourth level ICMPv6 identifiers
  .It In netinet/tcp_var.h
  fourth level TCP identifiers
  .It In netinet/udp_var.h
  fourth level UDP identifiers
  .It In ddb/db_var.h
  second level ddb identifiers
  .It In sys/mount.h
  second level vfs identifiers
  .It In miscfs/fuse/fusefs.h
  third level fusefs identifiers
  .It In nfs/nfs.h
  third level NFS identifiers
  .It In ufs/ffs/ffs_extern.h
  third level FFS identifiers
  .It In machine/cpu.h
  second level CPU identifiers
  .El
  .Sh ERRORS
  The following errors may be reported:
  .Bl -tag -width Er
  .It Bq Er EFAULT
  The buffer
  .Fa name ,
  .Fa oldp ,
  .Fa newp ,
  or length pointer
  .Fa oldlenp
  contains an invalid address.
  .It Bq Er EINVAL
  The
  .Fa name
  array is less than two or greater than
  .Dv CTL_MAXNAME .
  .It Bq Er EINVAL
  A non-null
  .Fa newp
  pointer is given and its specified length in
  .Fa newlen
  is too large or too small.
  .It Bq Er ENOMEM
  The length pointed to by
  .Fa oldlenp
  is too short to hold the requested value.
  .It Bq Er ENOENT
  The mib specified does not exist, or exceeds the range that is possible.
  .It Bq Er ENXIO
  If the mib is a sparsely populated array, this error may be returned
  instead.
  .It Bq Er ENOTDIR
  The
  .Fa name
  array specifies an intermediate rather than terminal name.
  .It Bq Er EOPNOTSUPP
  The
  .Fa name
  array specifies a value that is unknown.
  .It Bq Er EPERM
  An attempt is made to set a read-only value.
  .It Bq Er EPERM
  A process without appropriate privileges attempts to set a value.
  .It Bq Er EPERM
  An attempt to change a value protected by the current kernel security
  level is made.
  .It Bq Er ESRCH
  No process could be found which corresponds to the given process ID.
  .El
  .Sh SEE ALSO
  .Xr pathconf 2 ,
  .Xr sysconf 3 ,
  .Xr ddb 4 ,
  .Xr sysctl.conf 5 ,
  .Xr securelevel 7 ,
  .Xr sysctl 8
  .Sh HISTORY
  The
  .Fn sysctl
  function first appeared in
  .Bx 4.4 .