.\"	$NetBSD: sysctl.3,v 1.108 2003/02/02 20:33:07 kleink Exp $
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.\"	@(#)sysctl.3	8.4 (Berkeley) 5/9/95
.\"
.Dd February 2, 2003
.Dt SYSCTL 3
.Os
.Sh NAME
.Nm sysctl
.Nd get or set system information
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include \*[Lt]sys/param.h\*[Gt]
.Fd #include \*[Lt]sys/sysctl.h\*[Gt]
.Ft int
.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
.Sh DESCRIPTION
The
.Nm
function retrieves system information and allows processes with
appropriate privileges to set system information.
The information available from
.Nm
consists of integers, strings, and tables.
Information may be retrieved and set from the command interface
using the
.Xr sysctl 8
utility.
.Pp
Unless explicitly noted below,
.Nm
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
.Nm
are serialized to avoid deadlock.
.Pp
The state is described using a ``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 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
.Nm
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
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 CTL_ prefix in
.Pa Aq 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.
.Pp
.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
.It Sy Pa Name	Next level names	Description
.It CTL\_KERN	sys/sysctl.h	High kernel limits
.It CTL\_VM	uvm/uvm_param.h	Virtual memory
.It CTL\_VFS	sys/mount.h	Filesystem
.It CTL\_NET	sys/socket.h	Networking
.It CTL\_DEBUG	sys/sysctl.h	Debugging
.It CTL\_HW	sys/sysctl.h	Generic CPU, I/O
.It CTL\_MACHDEP	sys/sysctl.h	Machine dependent
.It CTL\_USER	sys/sysctl.h	User-level
.It CTL\_DDB	sys/sysctl.h	In-kernel debugger
.It CTL\_PROC	sys/sysctl.h	Per-process
.It CTL\_VENDOR	?	Vendor specific
.El
.Pp
For example, the following retrieves the maximum number of processes allowed
in the system:
.Bd -literal -offset indent -compact
int mib[2], maxproc;
size_t len;
.sp
mib[0] = CTL_KERN;
mib[1] = KERN_MAXPROC;
len = sizeof(maxproc);
sysctl(mib, 2, \*[Am]maxproc, \*[Am]len, NULL, 0);
.Ed
.sp
To retrieve the standard search path for the system utilities:
.Bd -literal -offset indent -compact
int mib[2];
size_t len;
char *p;
.sp
mib[0] = CTL_USER;
mib[1] = USER_CS_PATH;
sysctl(mib, 2, NULL, \*[Am]len, NULL, 0);
p = malloc(len);
sysctl(mib, 2, p, \*[Am]len, NULL, 0);
.Ed
.Sh CTL_DEBUG
The debugging variables vary from system to system.
A debugging variable may be added or deleted without need to recompile
.Nm
to know about it.
Each time it runs,
.Nm
gets the list of debugging variables from the kernel and
displays their current values.
The system defines twenty
.Va ( struct ctldebug )
variables named
.Dv debug0
through
.Dv 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
.Dv dospecialcheck
as a debugging variable, the following declaration would be used:
.Bd -literal -offset indent -compact
int dospecialcheck = 1;
struct ctldebug debug5 = { "dospecialcheck", \*[Am]dospecialcheck };
.Ed
.Sh CTL_VFS
A distinguished second level name, VFS_GENERIC,
is used to get general information about all filesystems.
One of its third level identifiers is VFS_MAXTYPENUM
that gives the highest valid filesystem type number.
Its other third level identifier is VFS_CONF that
returns configuration information about the filesystem
type given as a fourth level identifier.
The remaining second level identifiers are the
filesystem type number returned by a
.Xr statfs 2
call or from VFS_CONF.
The third level identifiers available for each filesystem
are given in the header file that defines the mount
argument structure for that filesystem.
.Sh CTL_HW
The string and integer information available for the CTL_HW level
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "Second level nameXXXXXX" "struct disk_sysctlXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It HW\_MACHINE	string	no
.It HW\_MODEL	string	no
.It HW\_NCPU	integer	no
.It HW\_BYTEORDER	integer	no
.It HW\_PHYSMEM	integer	no
.It HW\_USERMEM	integer	no
.It HW\_PAGESIZE	integer	no
.\".It HW\_DISKNAMES	struct	no
.\".It HW\_DISKSTATS	struct	no
.It HW\_MACHINE\_ARCH	string	no
.It HW\_ALIGNBYTES	integer	no
.It HW\_DISKNAMES	string	no
.It HW\_DISKSTATS	struct disk_sysctl	no
.El
.Pp
.Bl -tag -width "123456"
.It Li HW_MACHINE
The machine class.
.It Li HW_MODEL
The machine model
.It Li HW_NCPU
The number of cpus.
.ne 1i
.It Li HW_BYTEORDER
The byteorder (4,321, or 1,234).
.It Li HW_PHYSMEM
The bytes of physical memory.
.It Li HW_USERMEM
The bytes of non-kernel memory.
.It Li HW_PAGESIZE
The software page size.
.It Li HW_DISKNAMES
The list of (space separated) disk device names on the system.
.It Li HW_DISKSTATS
Return statistical information on the disk devices on the system.
An array of
.Va struct disk_sysctl
structures is returned,
whose size depends on the current number of such objects in the system.
The third level name is the size of the
.Va struct disk_sysctl .
.It Li HW_MACHINE_ARCH
The machine cpu class.
.It Li HW_ALIGNBYTES
Alignment constraint for all possible data types.
This shows the value
.Dv ALIGNBYTES
in
.Pa /usr/include/machine/param.h ,
at the kernel compilation time.
.El
.Sh CTL_KERN
The string and integer information available for the CTL_KERN level
is detailed below.
The changeable column shows whether a process with appropriate
privilege 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 "KERNXCHOWNXRESTRICTEDXXXXXX" "struct clockrateXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It KERN\_ARGMAX	integer	no
.It KERN\_AUTONICETIME	integer	yes
.It KERN\_AUTONICEVAL	integer	yes
.It KERN\_BOOTTIME	struct timeval	no
.It KERN\_CCPU	integer	no
.It KERN\_CLOCKRATE	struct clockinfo	no
.It KERN\_CP\_TIME	long[\|]	no
.It KERN\_DEFCORENAME	string	yes
.It KERN\_DOMAINNAME	string	yes
.It KERN\_FILE	struct file	no
.It KERN\_FORKFSLEEP	integer	yes
.It KERN\_FSCALE	integer	no
.It KERN\_FSYNC	integer	no
.It KERN\_HOSTID	integer	yes
.It KERN\_HOSTNAME	string	yes
.It KERN\_IOV\_MAX	integer	no
.It KERN\_JOB\_CONTROL	integer	no
.It KERN\_LABELOFFSET	integer	no
.It KERN\_LABELSECTOR	integer	no
.It KERN\_LOGIN\_NAME\_MAX	integer	no
.It KERN\_LOGSIGEXIT	integer	yes
.It KERN\_MAPPED\_FILES	integer	no
.It KERN\_MAXFILES	integer	yes
.It KERN\_MAXPARTITIONS	integer	no
.It KERN\_MAXPROC	integer	yes
.It KERN\_MAXPTYS	integer	yes
.It KERN\_MAXVNODES	integer	yes
.It KERN\_MBUF	node	not applicable
.It KERN\_MEMLOCK	integer	no
.It KERN\_MEMLOCK\_RANGE	integer	no
.It KERN\_MEMORY\_PROTECTION	integer	no
.It KERN\_MONOTONIC\_CLOCK	integer	no
.It KERN\_MSGBUF	char[\|]	no
.It KERN\_MSGBUFSIZE	integer	no
.It KERN\_NGROUPS	integer	no
.It KERN\_NTPTIME	struct ntptimeval	no
.It KERN\_OSRELEASE	string	no
.It KERN\_OSREV	integer	no
.It KERN\_OSTYPE	string	no
.It KERN\_POSIX1	integer	no
.It KERN\_POSIX\_BARRIERS	integer	no
.It KERN\_POSIX\_READER\_WRITER\_LOCKS	integer	no
.It KERN\_POSIX\_SEMAPHORES	integer	no
.It KERN\_POSIX\_SPIN\_LOCKS	integer	no
.It KERN\_POSIX\_THREADS	integer	no
.It KERN\_POSIX\_TIMERS	integer	no
.It KERN\_PROC	struct kinfo_proc	no
.It KERN\_PROC2	struct kinfo_proc2	no
.It KERN\_PROC\_ARGS	string	no
.It KERN\_PROF	node	not applicable
.It KERN\_RAWPARTITION	integer	no
.It KERN\_ROOT\_DEVICE	string	no
.It KERN\_RTC\_OFFSET	integer	no
.It KERN\_SAVED\_IDS	integer	no
.It KERN\_SECURELVL	integer	raise only
.It KERN\_SYNCHRONIZED\_IO	integer	no
.It KERN\_SYSVIPC\_INFO	node	not applicable
.It KERN\_SYSVMSG	integer	no
.It KERN\_SYSVSEM	integer	no
.It KERN\_SYSVSHM	integer	no
.It KERN\_TKSTAT	node	not applicable
.It KERN\_VERSION	string	no
.It KERN\_VNODE	struct vnode	no
.El
.ne 1i
.Pp
.Bl -tag -width "123456"
.It Li KERN_ARGMAX
The maximum bytes of argument to
.Xr execve 2 .
.It Li KERN_AUTONICETIME
The number of seconds of cpu-time a non-root process may accumulate before
having its priority lowered from the default to the value of KERN_AUTONICEVAL.
If set to 0, automatic lowering of priority is not performed, and if set to \-1
all non-root processes are immediately lowered.
.It Li KERN_AUTONICEVAL
The priority assigned for automatically niced processes.
.It Li KERN_BOOTTIME
A
.Va struct timeval
structure is returned.
This structure contains the time that the system was booted.
.It Li KERN_CCPU
The scheduler exponential decay value.
.It Li KERN_CLOCKRATE
A
.Va struct clockinfo
structure is returned.
This structure contains the clock, statistics clock and profiling clock
frequencies, the number of micro-seconds per hz tick, and the clock
skew rate.
.It Li KERN_CP_TIME
Return an array if CPUSTATES longs is returned.
This array contains the
number of clock ticks spent in different CPU states.
.It Li KERN_DEFCORENAME
Default template for the name of core dump files (see also PROC_PID_CORENAME
in the per-process variables CTL_PROC, and
.Xr core 5
for format of this template).
The default value is
.Nm %n.core
and can be changed with the kernel configuration option
.Cd options DEFCORENAME
(see
.Xr options 4
).
.It Li KERN_DOMAINNAME
Get or set the YP domain name.
.It Li KERN_FILE
Return the entire file table.
The returned data consists of a single
.Va struct filehead
followed by an array of
.Va struct file ,
whose size depends on the current number of such objects in the system.
.It Li KERN_FSCALE
The kernel fixed-point scale factor.
.It Li KERN_FORKFSLEEP
If
.Xr fork 2
system call fails due to limit on number of processes (either
the global maxproc limit or user's one), wait for this many
miliseconds before returning
.Er EAGAIN
error to process.
Useful to keep heavily forking runaway processes in bay.
Default zero (no sleep).
Maximum is 20 seconds.
.It Li KERN_FSYNC
Return 1 if the POSIX 1003.1b File Synchronization Option is available
on this system,
otherwise 0.
.It Li KERN_HOSTID
Get or set the host id.
.It Li KERN_HOSTNAME
Get or set the hostname.
.It Li KERN_IOV_MAX
Return the maximum number of
.Va iovec
structures that a process has available for use with
.Xr preadv 2 ,
.Xr pwritev 2 ,
.Xr readv 2 ,
.Xr recvmsg 2 ,
.Xr sendmsg 2
and
.Xr writev 2 .
.It Li KERN_JOB_CONTROL
Return 1 if job control is available on this system, otherwise 0.
.It Li KERN_LABELOFFSET
The offset within the sector specified by KERN_LABELSECTOR of the
.Xr disklabel 5 .
.It Li KERN_LABELSECTOR
The sector number containing the
.Xr disklabel 5 .
.It Li KERN_LOGIN_NAME_MAX
The size of the storage required for a login name, in bytes,
including the terminating NUL.
.It Li KERN_LOGSIGEXIT
If this flag is non-zero, the kernel will
.Xr log 9
all process exits due to signals which create a
.Xr core 5
file, and whether the coredump was created.
.It Li KERN_MAPPED_FILES
Returns 1 if the POSIX 1003.1b Memory Mapped Files Option is available
on this system,
otherwise 0.
.It Li KERN_MAXFILES
The maximum number of open files that may be open in the system.
.It Li KERN_MAXPARTITIONS
The maximum number of partitions allowed per disk.
.It Li KERN_MAXPROC
The maximum number of simultaneous processes the system will allow.
.It Li KERN_MAXPTYS
The maximum number of pseudo terminals.
This value can be both raised and lowered, though it cannot
be set lower than number of currently used ptys.
See also
.Xr pty 4 .
.It Li KERN_MAXVNODES
The maximum number of vnodes available on the system.
This can only be raised.
.It Li KERN_MBUF
Return information about the mbuf control variables.
the third level names for the mbuf variables are detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "MBUFXNMBCLUSTERSXXX" "struct integerXXX" -offset indent
.It Sy Pa Third level name	Type	Changeable
.It MBUF\_MSIZE	integer	yes
.It MBUF\_MCLBYTES	integer	yes
.It MBUF\_NMBCLUSTERS	integer	yes
.It MBUF\_MBLOWAT	integer	yes
.It MBUF\_MCLLOWAT	integer	yes
.El
.Pp
The variables are as follows:
.Bl -tag -width "123456"
.It Li MBUF_MSIZE
The mbuf base size.
.It Li MBUF_MCLBYTES
The mbuf cluster size.
.It Li MBUF_NMBCLUSTERS
The limit on the number of mbuf clusters.
The variable can only be increased, and only increased on machines with
direct-mapped pool pages
.It Li MBUF_MBLOWAT
The mbuf low water mark.
.It Li MBUF_MCLLOWAT
The mbuf cluster low water mark.
.El
.It Li KERN_MEMLOCK
Returns 1 if the POSIX 1003.1b Process Memory Locking Option is available
on this system,
otherwise 0.
.It Li KERN_MEMLOCK_RANGE
Returns 1 if the POSIX 1003.1b Range Memory Locking Option is available
on this system,
otherwise 0.
.It Li KERN_MEMORY_PROTECTION
Returns 1 if the POSIX 1003.1b Memory Protection Option is available
on this system,
otherwise 0.
.It Li KERN_MONOTONIC_CLOCK
Returns the standard version the implementation of the POSIX 1003.1b
Monotonic Clock Option conforms to,
otherwise 0.
.It Li KERN_MSGBUF
The kernel message buffer, rotated so that the head of the circular kernel
message buffer is returned at the start of the buffer specified by
.Fa oldp .
The returned data may contain NUL bytes.
.It Li KERN_MSGBUFSIZE
The maximum number of characters that the kernel message buffer can hold.
.It Li KERN_NGROUPS
The maximum number of supplemental groups.
.It Li KERN_NO_TRUNC
Return 1 if file names longer than KERN_NAME_MAX are truncated.
.It Li KERN_NTPTIME
A
.Va struct ntptimeval
structure is returned.
This structure contains data used by the
.Xr ntpd 8
program.
.It Li KERN_OSRELEASE
The system release string.
.It Li KERN_OSREV
The system revision string.
.It Li KERN_OSTYPE
The system type string.
.It Li KERN_PATH_MAX
The maximum number of bytes in a pathname.
.It Li KERN_POSIX1
The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
attempts to comply.
.It Li KERN_POSIX_BARRIERS
The version of
.St -p1003.1
and its
Barriers
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_POSIX_READER_WRITER_LOCKS
The version of
.St -p1003.1
and its
Read-Write Locks
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_POSIX_SEMAPHORES
The version of
.St -p1003.1
and its
Semaphores
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_POSIX_SPIN_LOCKS
The version of
.St -p1003.1
and its
Spin Locks
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_POSIX_THREADS
The version of
.St -p1003.1
and its
Threads
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_POSIX_TIMERS
The version of
.St -p1003.1
and its
Timers
option to which the system attempts to conform,
otherwise 0.
.It Li KERN_PROC
Return the entire process table, or a subset of it.
An array of
.Va struct kinfo_proc
structures is returned,
whose size depends on the current number of such objects in the system.
The third and fourth level names are as follows:
.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
.It Pa Third level name	Fourth level is:
.It KERN\_PROC\_ALL	None
.It KERN\_PROC\_PID	A process ID
.It KERN\_PROC\_PGRP	A process group
.It KERN\_PROC\_SESSION	A session ID
.It KERN\_PROC\_TTY	A tty device
.It KERN\_PROC\_UID	A user ID
.It KERN\_PROC\_RUID	A real user ID
.It KERN\_PROC\_GID	A group ID
.It KERN\_PROC\_RGID	A real group ID
.El
.It Li KERN_PROC2
As for KERN_PROC, but an array of
.Va struct kinfo_proc2
structures are returned.
The fifth level name is the size of the
.Va struct kinfo_proc2
and the sixth level name is the number of structures to return.
.It Li KERN_PROC_ARGS
Return the argv or environment strings (or the number thereof)
of a process.
Multiple strings are returned separated by NUL characters.
The third level name is the process ID.
The fourth level name is as follows:
.Bl -column "Third level nameXXXXXX" -offset indent
.It KERN\_PROC\_ARGV	The argv strings
.It KERN\_PROC\_NARGV	The number of argv strings
.It KERN\_PROC\_ENV	The environ strings
.It KERN\_PROC\_NENV	The number of environ strings
.El
.It Li KERN_PROF
Return profiling information about the kernel.
If the kernel is not compiled for profiling,
attempts to retrieve any of the KERN_PROF values will
fail with EOPNOTSUPP.
The third level names for the string and integer profiling information
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
.It Sy Pa Third level name	Type	Changeable
.It GPROF\_STATE	integer	yes
.It GPROF\_COUNT	u_short[\|]	yes
.It GPROF\_FROMS	u_short[\|]	yes
.It GPROF\_TOS	struct tostruct	yes
.It GPROF\_GMONPARAM	struct gmonparam	no
.El
.Pp
The variables are as follows:
.Bl -tag -width "123456"
.It Li GPROF_STATE
Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
is running or stopped.
.It Li GPROF_COUNT
Array of statistical program counter counts.
.It Li GPROF_FROMS
Array indexed by program counter of call-from points.
.It Li GPROF_TOS
Array of
.Va struct tostruct
describing destination of calls and their counts.
.It Li GPROF_GMONPARAM
Structure giving the sizes of the above arrays.
.El
.It Li KERN_RAWPARTITION
The raw partition of a disk (a == 0).
.It Li KERN_ROOT_DEVICE
The name of the root device.
.It Li KERN_RTC_OFFSET
Return the offset of real time clock from UTC in minutes.
.It Li KERN_SAVED_IDS
Returns 1 if saved set-group and saved set-user ID is available.
.It Li KERN_SECURELVL
The system security level.
This level may be raised by processes with appropriate privilege.
It may only be lowered by process 1.
.It Li KERN_SYNCHRONIZED_IO
Returns 1 if the POSIX 1003.1b Synchronized I/O Option is available
on this system,
otherwise 0.
.It Li 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_INFOXXX" "struct shm_sysctl_infoXXX" -offset indent
.It Sy Pa Third level name	Type
.It KERN\_SYSVIPC\_MSG\_INFO	struct msg_sysctl_info
.It KERN\_SYSVIPC\_SEM\_INFO	struct sem_sysctl_info
.It KERN\_SYSVIPC\_SHM\_INFO	struct shm_sysctl_info
.El
.Pp
.Bl -tag -width "123456"
.It Li KERN_SYSVIPC_MSG_INFO
Return information on the System V style message facility.
The
.Sy msg_sysctl_info
structure is defined in
.Aq Pa sys/msg.h .
.It Li KERN_SYSVIPC_SEM_INFO
Return information on the System V style semaphore facility.
The
.Sy sem_sysctl_info
structure is defined in
.Aq Pa sys/sem.h .
.It Li KERN_SYSVIPC_SHM_INFO
Return information on the System V style shared memory facility.
The
.Sy shm_sysctl_info
structure is defined in
.Aq Pa sys/shm.h .
.El
.It Li KERN_SYSVMSG
Returns 1 if System V style message queue functionality is available
on this system,
otherwise 0.
.It Li KERN_SYSVSEM
Returns 1 if System V style semaphore functionality is available
on this system,
otherwise 0.
.It Li KERN_SYSVSHM
Returns 1 if System V style share memory functionality is available
on this system,
otherwise 0.
.It Li KERN_TKSTAT
Return information about the number of characters sent and received
on ttys.
The third level names for the tty statistic variables are detailed below.
The changeable column shows whether a process
with appropriate privilege may change the value.
.Bl -column "KERNXTKSTATXRAWCCXXX" "struct integerXXX" -offset indent
.It Sy Pa Third level name	Type	Changeable
.It KERN\_TKSTAT\_NIN	quad	no
.It KERN\_TKSTAT\_NOUT	quad	no
.It KERN\_TKSTAT\_CANCC	quad	no
.It KERN\_TKSTAT\_RAWCC	quad	no
.El
.Pp
The variables are as follows:
.Bl -tag -width "123456"
.It Li KERN_TKSTAT_NIN
The total number of input characters.
.It Li KERN_TKSTAT_NOUT
The total number of output characters.
.It Li KERN_TKSTAT_CANCC
The number of canonical input characters.
.It Li KERN_TKSTAT_RAWCC
The number of raw input characters.
.El
.It Li KERN_VERSION
The system version string.
.It Li KERN_VNODE
Return the entire vnode table.
Note, the vnode table is not necessarily a consistent snapshot of
the system.
The returned data consists of an array whose size depends on the
current number of such objects in the system.
Each element of the array contains the kernel address of a vnode
.Va struct vnode *
followed by the vnode itself
.Va struct vnode .
.El
.Sh CTL_MACHDEP
The set of variables defined is architecture dependent.
Most architectures define at least the following variables.
.Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It Li CPU_CONSDEV	dev_t	no
.El
.Sh CTL_NET
The string and integer information available for the CTL_NET level
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It PF\_ROUTE	routing messages	no
.It PF\_INET	IPv4 values	yes
.It PF\_INET6	IPv6 values	yes
.It PF\_KEY	IPsec key management values	yes
.El
.Pp
.Bl -tag -width "123456"
.It Li 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 nameXXXXXX" "Sixth level is:XXX" -offset indent
.It Pa Fifth level name	Sixth level is:
.It NET\_RT\_FLAGS	rtflags
.It NET\_RT\_DUMP	None
.It NET\_RT\_IFLIST	None
.El
.It Li PF_INET
Get or set various global information about the 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" "Variable nameXX" "integer" "yes" -offset indent
.It Pa Protocol name	Variable name	Type	Changeable
.It ip	forwarding	integer	yes
.It ip	redirect	integer	yes
.It ip	ttl	integer	yes
.It ip	forwsrcrt	integer	yes
.It ip	directed-broadcast	integer	yes
.It ip	allowsrcrt	integer	yes
.It ip	subnetsarelocal	integer	yes
.It ip	mtudisc	integer	yes
.It ip	anonportmin	integer	yes
.It ip	anonportmax	integer	yes
.It ip	mtudisctimeout	integer	yes
.It ip	gifttl	integer	yes
.It ip	grettl	integer	yes
.It ip	lowportmin	integer	yes
.It ip	lowportmax	integer	yes
.It ip	maxfragpacket	integer	yes
.It icmp	maskrepl	integer	yes
.It icmp	errppslimit	integer	yes
.It icmp	rediraccept	integer	yes
.It icmp	redirtimeout	integer	yes
.It tcp	rfc1323	integer	yes
.It tcp	sendspace	integer	yes
.It tcp	recvspace	integer	yes
.It tcp	mssdflt	integer	yes
.It tcp	syn_cache_limit	integer	yes
.It tcp	syn_bucket_limit	integer	yes
.It tcp	syn_cache_interval	integer	yes
.It tcp	init_win	integer	yes
.It tcp	mss_ifmtu	integer	yes
.It tcp	sack	integer	yes
.It tcp	win_scale	integer	yes
.It tcp	timestamps	integer	yes
.It tcp	compat_42	integer	yes
.It tcp	cwm	integer	yes
.It tcp	cwm_burstsize	integer	yes
.It tcp	ack_on_push	integer	yes
.It tcp	keepidle	integer	yes
.It tcp	keepintvl	integer	yes
.It tcp	keepcnt	integer	yes
.It tcp	slowhz	integer	no
.It tcp	newreno	integer	yes
.It tcp	log_refused	integer	yes
.It tcp	rstppslimit	integer	yes
.It udp	checksum	integer	yes
.It udp	sendspace	integer	yes
.It udp	recvspace	integer	yes
.El
.Pp
The variables are as follows:
.Bl -tag -width "123456"
.It Li ip.forwarding
Returns 1 when IP forwarding is enabled for the host,
meaning that the host is acting as a router.
.It Li 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.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 ip.forwsrcrt
Returns 1 when forwarding of source-routed packets is enabled for
the host.
This value may only be changed if the kernel security level is less than 1.
.It Li ip.directed-broadcast
Returns 1 if directed broadcast behavior is enabled for the host.
.It Li ip.allowsrcrt
Returns 1 if the host accepts source routed packets.
.It Li ip.subnetsarelocal
Returns 1 if subnets are to be considered local addresses.
.It Li ip.mtudisc
Returns 1 if Path MTU Discovery is enabled.
.It Li ip.anonportmin
The lowest port number to use for TCP and UDP ephemeral port allocation.
This cannot be set to less than 1024 or greater than 65535.
.It Li ip.anonportmax
The highest port number to use for TCP and UDP ephemeral port allocation.
This cannot be set to less than 1024 or greater than 65535, and must
be greater than
.Li ip.anonportmin .
.It Li ip.mtudisctimeout
Returns the 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.gifttl
The maximum time-to-live (hop count) value for an IPv4 packet generated by
.Xr gif 4
tunnel interface.
.It Li ip.grettl
The maximum time-to-live (hop count) value for an IPv4 packet generated by
.Xr gre 4
tunnel interface.
.It Li ip.lowportmin
The lowest port number to use for TCP and UDP reserved port allocation.
This cannot be set to less than 0 or greater than 1024, and must
be smaller than
.Li ip.lowportmax .
.It Li ip.lowportmax
The highest port number to use for TCP and UDP reserved port allocation.
This cannot be set to less than 0 or greater than 1024, and must
be greater than
.Li ip.lowportmin .
.It Li ip.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.
.It Li icmp.maskrepl
Returns 1 if ICMP network mask requests are to be answered.
.It Li icmp.errppslimit
The variable specifies the maximum number of outgoing ICMP error messages,
per second.
ICMP error messages that exceeded the value are subject to rate limitation
and will not go out from the node.
Negative value disables rate limitation.
.It Li 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
The variable specifies lifetime of routing entries generated by incoming
ICMP redirect.
This defaults to 600 seconds.
.It Li tcp.rfc1323
Returns 1 if RFC1323 extensions to TCP are enabled.
.It Li tcp.sendspace
Returns the default TCP send buffer size.
.It Li tcp.recvspace
Returns the default TCP receive buffer size.
.It Li tcp.mssdflt
Returns the default maximum segment size both advertized to the peer
and to use when the peer does not advertize a maximum segment size to
us during connection setup.
Do not change this value unless you really know what you are doing.
.It Li tcp.syn_cache_limit
Returns the maximum number of entries allowed in the TCP compressed state
engine.
.It Li tcp.syn_bucket_limit
Returns the maximum number of entries allowed per hash bucket in the TCP
compressed state engine.
.It Li tcp.syn_cache_interval
Returns the TCP compressed state engine's timer interval.
.It Li tcp.init_win
Returns a value indicating the TCP initial congestion window.
If this value is 0, an auto-tuning algorithm designed to use an initial
window of approximately 4K bytes is in use.
Otherwise, this value indicates a fixed number of packets.
.It Li tcp.mss_ifmtu
Returns 1 if TCP calculates the outgoing maximum segment size based on
the MTU of the appropriate interface.
Otherwise, it is calculated based on the greater of the MTU of the
interface, and the largest (non-loopback) interface MTU on the system.
.It Li tcp.sack
TCP Selective ACKnowledgement (RFC 2018) is not implemented in
.Nx
at this time.
Changing this value will have no effect.
.It Li tcp.win_scale
If rfc1323 is enabled, a value of 1 indicates RFC1323 window scale options,
for increasing the TCP window size, are enabled.
.It Li tcp.timestamps
If rfc1323 is enabled, a value of 1 indicates RFC1323 time stamp options,
used for measuring TCP round trip times, are enabled.
.It Li tcp.compat_42
Returns 1 if work-arounds for bugs in the 4.2BSD TCP implementation are
enabled.
Use of this option is not recommended, although it may be
required in order to communicate with extremely old TCP implementations.
.It Li tcp.cwm
Returns 1 if use of the Hughes/Touch/Heidemann Congestion Window Monitoring
algorithm is enabled.
This algorithm prevents line-rate bursts of packets that could
otherwise occur when data begins flowing on an idle TCP connection.
These line-rate bursts can contribute to network and router congestion.
This can be particularly useful on World Wide Web servers
which support HTTP/1.1, which has lingering connections.
.It Li tcp.cwm_burstsize
Returns the Congestion Window Monitoring allowed burst size, in terms
of packet count.
.It Li tcp.ack_on_push
Returns 1 if TCP is to immediately transmit an ACK upon reception of
a packet with PUSH set.
This can avoid losing a round trip time in some rare situations,
but has the caveat of potentially defeating TCP's delayed ACK algorithm.
Use of this option is generally not recommended, but
the variable exists in case your configuration really needs it.
.It Li tcp.keepidle
Time a connection must be idle before keepalives are sent (if keepalives
are enabled for the connection).
See also tcp.slowhz.
.It Li tcp.keepintvl
Time after a keepalive probe is sent until, in the absence of any response,
another probe is sent.
See also tcp.slowhz.
.It Li tcp.keepcnt
Number of keepalive probes sent before declaring a connection dead.
If set to zero, there is no limit;
keepalives will be sent until some kind of
response is received from the peer.
.It Li tcp.slowhz
The units for tcp.keepidle and tcp.keepintvl; those variables are in ticks
of a clock that ticks tcp.slowhz times per second.
(That is, their values
must be divided by the tcp.slowhz value to get times in seconds.)
.It Li tcp.newreno
Returns 1 if the use of J.
Hoe's NewReno congestion control algorithm is enabled.
This algorithm improves the start-up behavior of TCP connections.
.It Li tcp.log_refused
Returns 1 if refused TCP connections to the host will be logged.
.It Li tcp.rstppslimit
The variable specifies the maximum number of outgoing TCP RST packets,
per second.
TCP RST packet that exceeded the value are subject to rate limitation
and will not go out from the node.
Negative value disables rate limitation.
.It Li udp.checksum
Returns 1 when UDP checksums are being computed and checked.
Disabling UDP checksums is strongly discouraged.
.It Li udp.sendspace
Returns the default UDP send buffer size.
.It Li udp.recvspace
Returns the default UDP receive buffer size.
.El
.Pp
For variables net.*.ipsec, please refer to
.Xr ipsec 4 .
.It Li PF_INET6
Get or set various global information about the 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" "Variable nameXX" "integer" "yes" -offset indent
.It Pa Protocol name	Variable name	Type	Changeable
.It ip6	forwarding	integer	yes
.It ip6	redirect	integer	yes
.It ip6	hlim	integer	yes
.It ip6	maxfragpackets	integer	yes
.It ip6	accept_rtadv	integer	yes
.It ip6	keepfaith	integer	yes
.It ip6	log_interval	integer	yes
.It ip6	hdrnestlimit	integer	yes
.It ip6	dad_count	integer	yes
.It ip6	auto_flowlabel	integer	yes
.It ip6	defmcasthlim	integer	yes
.It ip6	gif_hlim	integer	yes
.It ip6	kame_version	string	no
.It ip6	use_deprecated	integer	yes
.It ip6	rr_prune	integer	yes
.It ip6	v6only	integer	yes
.It ip6	anonportmin	integer	yes
.It ip6	anonportmax	integer	yes
.It ip6	lowportmin	integer	yes
.It ip6	lowportmax	integer	yes
.It ip6	maxfrags	integer	yes
.It icmp6	rediraccept	integer	yes
.It icmp6	redirtimeout	integer	yes
.It icmp6	nd6_prune	integer	yes
.It icmp6	nd6_delay	integer	yes
.It icmp6	nd6_umaxtries	integer	yes
.It icmp6	nd6_mmaxtries	integer	yes
.It icmp6	nd6_useloopback	integer	yes
.It icmp6	nodeinfo	integer	yes
.It icmp6	errppslimit	integer	yes
.It icmp6	nd6_maxnudhint	integer	yes
.It icmp6	mtudisc_hiwat	integer	yes
.It icmp6	mtudisc_lowat	integer	yes
.It icmp6	nd6_debug	integer	yes
.It udp6	sendspace	integer	yes
.It udp6	recvspace	integer	yes
.El
.Pp
The variables are as follows:
.Bl -tag -width "123456"
.It Li 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.
IPv6 specification defines node behavior for
.Dq router
case and
.Dq host
case quite differently, and changing this variable during operation
may cause serious trouble.
It is recommended to configure the variable at bootstrap time,
and bootstrap time only.
.It Li 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.
.It Li 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.
There are APIs to override the value, as documented in
.Xr ip6 4 .
.It Li 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.
.It Li ip6.accept_rtadv
If set to non-zero, the node will accept ICMPv6 router advertisement packets
and autoconfigures address prefixes and default routers.
The node must be a host
.Pq not a router
for the option to be meaningful.
.It Li ip6.keepfaith
If set to non-zero, it enables
.Dq FAITH
TCP relay IPv6-to-IPv4 translator code in the kernel.
Refer
.Xr faith 4
and
.Xr faithd 8
for detail.
.It Li ip6.log_interval
The variable controls amount of logs generated by IPv6 packet
forwarding engine, by setting interval between log output
.Pq in seconds .
.It Li 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.
.It Li ip6.dad_count
The variable configures number of IPv6 DAD
.Pq duplicated address detection
probe packets.
The packets will be generated when IPv6 interface addresses are configured.
.It Li ip6.auto_flowlabel
On connected transport protocol packets,
fill IPv6 flowlabel field to help intermediate routers to identify packet flows.
.It Li 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.
There are APIs to override the value, as documented in
.Xr ip6 4 .
.It Li ip6.gif_hlim
The maximum hop limit value for an IPv6 packet generated by
.Xr gif 4
tunnel interface.
.It Li ip6.kame_version
The string identifies the version of KAME IPv6 stack implemented in the kernel.
.It Li ip6.use_deprecated
The variable controls use of deprecated address, specified in RFC2462 5.5.4.
.It Li ip6.rr_prune
The variable specifies interval between IPv6 router renumbering prefix
babysitting, in seconds.
.It Li ip6.v6only
The variable specifies initial value for
.Dv IPV6_V6ONLY
socket option for
.Dv AF_INET6
socket.
Please refer to
.Xr ip6 4
for detail.
.It Li ip6.anonportmin
The lowest port number to use for TCP and UDP ephemeral port allocation.
This cannot be set to less than 1024 or greater than 65535.
.It Li ip6.anonportmax
The highest port number to use for TCP and UDP ephemeral port allocation.
This cannot be set to less than 1024 or greater than 65535, and must
be greater than
.Li ip6.anonportmin .
.It Li ip6.lowportmin
The lowest port number to use for TCP and UDP reserved port allocation.
This cannot be set to less than 0 or greater than 1024, and must
be smaller than
.Li ip6.lowportmax .
.It Li ip6.lowportmax
The highest port number to use for TCP and UDP reserved port allocation.
This cannot be set to less than 0 or greater than 1024, and must
be greater than
.Li ip6.lowportmin .
.It Li 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.
.It Li icmp6.rediraccept
If set to non-zero, the host will accept ICMPv6 redirect packets.
Note that IPv6 routers will never accept ICMPv6 redirect packets,
and the variable is meaningful on IPv6 hosts
.Pq non-router
only.
.It Li icmp6.redirtimeout
The variable specifies lifetime of routing entries generated by incoming
ICMPv6 redirect.
.It Li icmp6.nd6_prune
The variable specifies interval between IPv6 neighbor cache babysitting,
in seconds.
.It Li icmp6.nd6_delay
The variable specifies
.Dv DELAY_FIRST_PROBE_TIME
timing constant in IPv6 neighbor discovery specification
.Pq RFC2461 ,
in seconds.
.It Li icmp6.nd6_umaxtries
The variable specifies
.Dv MAX_UNICAST_SOLICIT
constant in IPv6 neighbor discovery specification
.Pq RFC2461 .
.It Li icmp6.nd6_mmaxtries
The variable specifies
.Dv MAX_MULTICAST_SOLICIT
constant in IPv6 neighbor discovery specification
.Pq RFC2461 .
.It Li icmp6.nd6_useloopback
If set to non-zero, kernel IPv6 stack will use loopback interface for
local traffic.
.It Li icmp6.nodeinfo
The variable enables responses to ICMPv6 node information queries.
If you set the variable to 0, responses will not be generated for
ICMPv6 node information queries.
Since node information queries can have a security impact, it is
possible to fine tune which responses should be answered.
Two separate bits can be set.
.Bl -tag -width "12345"
.It 1
Respond to ICMPv6 FQDN queries, e.g.
.Li ping6 -w .
.It 2
Respond to ICMPv6 node addresses queries, e.g.
.Li ping6 -a .
.El
.It Li icmp6.errppslimit
The variable specifies the maximum number of outgoing ICMPv6 error messages,
per second.
ICMPv6 error messages that exceeded the value are subject to rate limitation
and will not go out from the node.
Negative value disables rate limitation.
.It Li icmp6.nd6_maxnudhint
IPv6 neighbor discovery permits upper layer protocols to supply reachability
hints, to avoid unnecessary neighbor discovery exchanges.
The variable defines the number of consecutive hints the neighbor discovery
layer will take.
For example, by setting the variable to 3, neighbor discovery layer
will take 3 consecutive hints in maximum.
After receiving 3 hints, neighbor discovery layer will perform
normal neighbor discovery process.
.It Li icmp6.mtudisc_hiwat
.It Li icmp6.mtudisc_lowat
The variables define the maximum number of routing table entries,
created due to path MTU discovery
.Pq prevents denial-of-service attacks with ICMPv6 too big messages .
When IPv6 path MTU discovery happens, we keep path MTU information into
the routing table.
If the number of routing table entries exceed the 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.
Negative value disables the upper limit.
.It Li icmp6.nd6_debug
If set to non-zero, kernel IPv6 neighbor discovery code will generate
debugging messages.
The debug outputs are useful to diagnose IPv6 interoperability issues.
The flag must be set to 0 for normal operation.
.El
.Pp
We reuse net.*.tcp for
.Tn TCP
over
.Tn IPv6 ,
and therefore we do not have variables net.*.tcp6.
Variables net.inet6.udp6 have identical meaning to net.inet.udp.
Please refer to
.Li PF_INET
section above.
For variables net.*.ipsec6, please refer to
.Xr ipsec 4 .
.It Li PF_KEY
Get or set various global information about the IPsec key management.
The third level name is the variable name.
The currently defined variable and names are:
.Bl -column "blockacq_lifetime" "integer" "yes" -offset indent
.It Pa Variable name	Type	Changeable
.It debug	integer	yes
.It spi_try	integer	yes
.It spi_min_value	integer	yes
.It spi_max_value	integer	yes
.It random_int	integer	yes
.It larval_lifetime	integer	yes
.It blockacq_count	integer	yes
.It blockacq_lifetime	integer	yes
.It esp_keymin	integer	yes
.It esp_auth	integer	yes
.It ah_keymin	integer	yes
.El
The variables are as follows:
.Bl -tag -width "123456"
.It Li debug
Turn on debugging message from within the kernel.
The value is a bitmap, as defined in
.Pa /usr/include/netkey/key_debug.h .
.It Li spi_try
The number of times the kernel will try to obtain an unique SPI
when it generates it from random number generator.
.It Li spi_min_value
Minimum SPI value when generating it within the kernel.
.It Li spi_max_value
Maximum SPI value when generating it within the kernel.
.It Li random_int
Interval to stir pseudo-random number generator, in seconds.
Pseudo-random number generator is used only as a last resort when
random number source
.Pq Pa /dev/urandom
is not available.
It should not really be used, and if it were used,
kernel will warn about it.
.It Li larval_lifetime
Lifetime for LARVAL SAD entries, in seconds.
.It Li blockacq_count
Number of ACQUIRE PF_KEY messages to be blocked after an ACQUIRE message.
It avoids flood of ACQUIRE PF_KEY from being sent from the kernel to the
key management daemon.
.It Li blockacq_lifetime
Lifetime of ACQUIRE PF_KEY message.
.It Li esp_keymin
Minimum ESP key length, in bits.
The value is used when the kernel creates proposal payload
on ACQUIRE PF_KEY message.
.It Li esp_auth
Whether ESP authentication should be used or not.
Non-zero value indicates that ESP authentication should be used.
The value is used when the kernel creates proposal payload
on ACQUIRE PF_KEY message.
.It Li ah_keymin
Minimum AH key length, in bits,
The value is used when the kernel creates proposal payload
on ACQUIRE PF_KEY message.
.El
.El
.Sh CTL_PROC
The string and integer information available for the CTL_PROC
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
These values are per-process,
and as such may change from one process to another.
When a process is created,
the default values are inherited from its parent.
When a set-user-ID or set-group-ID binary is executed, the
value of PROC_PID_CORENAME is reset to the system default value.
The second level name is either the magic value PROC_CURPROC, which
points to the current process, or the PID of the target process.
.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" "yes" -offset indent
.It Sy Pa Third level name	Type	Changeable
.It PROC\_PID\_CORENAME	string	yes
.It PROC\_STOPEXEC	int	yes
.It PROC\_STOPFORK	int	yes
.It PROC\_PID\_LIMIT	node	not applicable
.El
.Bl -tag -width "123456"
.Pp
.It Li PROC_PID_CORENAME
The template used for the core dump file name (see
.Xr core 5
for details).
The base name must either be
.Nm core
or end with the suffix ``.core'' (the super-user may set arbitrary names).
By default it points to KERN_DEFCORENAME.
.It Li PROC_PID_LIMIT
Return resources limits, as defined for the
.Xr getrlimit 2
and
.Xr setrlimit 2
system calls.
The fourth level name is one of:
.Bl -tag -width PROC_PID_LIMIT_MEMLOCKAA
.It Li PROC_PID_LIMIT_CPU
The maximum amount of cpu time (in seconds) to be used by each process.
.It Li PROC_PID_LIMIT_FSIZE
The largest size (in bytes) file that may be created.
.It Li PROC_PID_LIMIT_DATA
The maximum size (in bytes) of the data segment for a process;
this defines how far a program may extend its break with the
.Xr sbrk 2
system call.
.It Li PROC_PID_LIMIT_STACK
The maximum size (in bytes) of the stack segment for a process;
this defines how far a program's stack segment may be extended.
Stack extension is performed automatically by the system.
.It Li PROC_PID_LIMIT_CORE
The largest size (in bytes)
.Pa core
file that may be created.
.It Li PROC_PID_LIMIT_RSS
The maximum size (in bytes) to which a process's resident set size may
grow.
This imposes a limit on the amount of physical memory to be given to
a process; if memory is tight, the system will prefer to take memory
from processes that are exceeding their declared resident set size.
.It Li PROC_PID_LIMIT_MEMLOCK
The maximum size (in bytes) which a process may lock into memory
using the
.Xr mlock 2
function.
.It Li PROC_PID_LIMIT_NPROC
The maximum number of simultaneous processes for this user id.
.It Li PROC_PID_LIMIT_NOFILE
The maximum number of open files for this process.
.El
.Pp
The fifth level name is one of PROC_PID_LIMIT_TYPE_SOFT or
PROC_PID_LIMIT_TYPE_HARD, to select respectively the soft or hard limit.
Both are of type integer.
.It Li PROC_STOPEXEC
If non zero, the process will be stopped on next
.Xr exec 3
call.
The process created by
.Xr exec 3
is created in the SSTOP state and is never scheduled for running
before being stopped.
This feature helps attaching a process with a debugger such as
.Xr gdb 1
before it had the opportunity to actually do anything.
.Pp
This value is inherited by the process's children.
.It Li PROC_STOPFORK
If non zero, the process' children will be stopped after
.Xr fork 2
calls.
The children is created in the SSTOP state and is never scheduled
for running before being stopped.
This feature helps attaching a process with a debugger such as
.Xr gdb 1
before it had the opportunity to actually do anything.
.Pp
This value is inherited by the process's children, and it also
apply to emulation specific system calls that fork a new process, such as
.Fn sproc
or
.Fn clone .
.El
.Sh CTL_USER
The string and integer information available for the CTL_USER level
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It USER\_BC\_BASE\_MAX	integer	no
.It USER\_BC\_DIM\_MAX	integer	no
.It USER\_BC\_SCALE\_MAX	integer	no
.It USER\_BC\_STRING\_MAX	integer	no
.It USER\_COLL\_WEIGHTS\_MAX	integer	no
.It USER\_CS\_PATH	string	no
.It USER\_EXPR\_NEST\_MAX	integer	no
.It USER\_LINE\_MAX	integer	no
.It USER\_POSIX2\_CHAR\_TERM	integer	no
.It USER\_POSIX2\_C\_BIND	integer	no
.It USER\_POSIX2\_C\_DEV	integer	no
.It USER\_POSIX2\_FORT\_DEV	integer	no
.It USER\_POSIX2\_FORT\_RUN	integer	no
.It USER\_POSIX2\_LOCALEDEF	integer	no
.It USER\_POSIX2\_SW\_DEV	integer	no
.It USER\_POSIX2\_UPE	integer	no
.It USER\_POSIX2\_VERSION	integer	no
.It USER\_RE\_DUP\_MAX	integer	no
.It USER\_STREAM\_MAX	integer	no
.It USER\_TZNAME\_MAX	integer	no
.It USER\_ATEXIT\_MAX	integer	no
.El
.Bl -tag -width "123456"
.Pp
.It Li USER_BC_BASE_MAX
The maximum ibase/obase values in the
.Xr bc 1
utility.
.It Li USER_BC_DIM_MAX
The maximum array size in the
.Xr bc 1
utility.
.It Li USER_BC_SCALE_MAX
The maximum scale value in the
.Xr bc 1
utility.
.It Li USER_BC_STRING_MAX
The maximum string length in the
.Xr bc 1
utility.
.It Li USER_COLL_WEIGHTS_MAX
The maximum number of weights that can be assigned to any entry of
the LC_COLLATE order keyword in the locale definition file.
.It Li USER_CS_PATH
Return a value for the
.Ev PATH
environment variable that finds all the standard utilities.
.It Li USER_EXPR_NEST_MAX
The maximum number of expressions that can be nested within
parenthesis by the
.Xr expr 1
utility.
.It Li USER_LINE_MAX
The maximum length in bytes of a text-processing utility's input
line.
.It Li USER_POSIX2_CHAR_TERM
Return 1 if the system supports at least one terminal type capable of
all operations described in POSIX 1003.2, otherwise 0.
.It Li USER_POSIX2_C_BIND
Return 1 if the system's C-language development facilities support the
C-Language Bindings Option, otherwise 0.
.It Li USER_POSIX2_C_DEV
Return 1 if the system supports the C-Language Development Utilities Option,
otherwise 0.
.It Li USER_POSIX2_FORT_DEV
Return 1 if the system supports the FORTRAN Development Utilities Option,
otherwise 0.
.It Li USER_POSIX2_FORT_RUN
Return 1 if the system supports the FORTRAN Runtime Utilities Option,
otherwise 0.
.It Li USER_POSIX2_LOCALEDEF
Return 1 if the system supports the creation of locales, otherwise 0.
.It Li USER_POSIX2_SW_DEV
Return 1 if the system supports the Software Development Utilities Option,
otherwise 0.
.It Li USER_POSIX2_UPE
Return 1 if the system supports the User Portability Utilities Option,
otherwise 0.
.It Li USER_POSIX2_VERSION
The version of POSIX 1003.2 with which the system attempts to comply.
.It Li USER_RE_DUP_MAX
The maximum number of repeated occurrences of a regular expression
permitted when using interval notation.
.ne 1i
.It Li USER_STREAM_MAX
The minimum maximum number of streams that a process may have open
at any one time.
.It Li USER_TZNAME_MAX
The minimum maximum number of types supported for the name of a
timezone.
.It Li USER_ATEXIT_MAX
The maximum namber of functions that may be registered with
.Xr atexit 3 .
.El
.Sh CTL_VM
The string and integer information available for the CTL_VM level
is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It VM\_ANONMAX	int	yes
.It VM\_ANONMIN	int	yes
.It VM\_EXECMAX	int	yes
.It VM\_EXECMIN	int	yes
.It VM\_FILEMAX	int	yes
.It VM\_FILEMIN	int	yes
.It VM\_LOADAVG	struct loadavg	no
.It VM\_MAXSLP	int	no
.It VM\_METER	struct vmtotal	no
.It VM\_NKMEMPAGES	int	no
.It VM\_USPACE	int	no
.It VM\_UVMEXP	struct uvmexp	no
.It VM\_UVMEXP2	struct uvmexp_sysctl	no
.El
.Pp
.Bl -tag -width "123456"
.It Li VM_ANONMAX
The percentage of physical memory which will be reclaimed
from other types of memory usage to store anonymous application data.
.It Li VM_ANONMIN
The percentage of physical memory which will be always be available for
anonymous application data.
.It Li VM_EXECMAX
The percentage of physical memory which will be reclaimed
from other types of memory usage to store cached executable data.
.It Li VM_EXECMIN
The percentage of physical memory which will be always be available for
cached executable data.
.It Li VM_FILEMAX
The percentage of physical memory which will be reclaimed
from other types of memory usage to store cached file data.
.It Li VM_FILEMIN
The percentage of physical memory which will be always be available for
cached file data.
.It Li VM_LOADAVG
Return the load average history.
The returned data consists of a
.Va struct loadavg .
.It Li VM_MAXSLP
The value of the maxslp kernel global variable.
.It Li VM_METER
Return system wide virtual memory statistics.
The returned data consists of a
.Va struct vmtotal .
.It Li VM_USPACE
The number of bytes allocated for each kernel stack.
.It Li VM_UVMEXP
Return system wide virtual memory statistics.
The returned data consists of a
.Va struct uvmexp .
.It Li VM_UVMEXP2
Return system wide virtual memory statistics.
The returned data consists of a
.Va struct uvmexp_sysctl .
.El
.Sh CTL_DDB
The integer information available for the CTL_DDB level is detailed below.
The changeable column shows whether a process with appropriate
privilege may change the value.
.Bl -column "DBCTL_TABSTOPSXXX" "integerXXX" -offset indent
.It Sy Pa Second level name	Type	Changeable
.It DBCTL\_RADIX	integer	yes
.It DBCTL\_MAXOFF	integer	yes
.It DBCTL\_LINES	integer	yes
.It DBCTL\_TABSTOPS	integer	yes
.It DBCTL\_ONPANIC	integer	yes
.It DBCTL\_FROMCONSOLE	integer	yes
.El
.Pp
.Bl -tag -width "123456"
.It Li DBCTL_RADIX
The input and output radix.
.It Li DBCTL_MAXOFF
The maximum symbol offset.
.It Li DBCTL_LINES
Number of display lines.
.It Li DBCTL_TABSTOPS
Tab width.
.It Li DBCTL_ONPANIC
If non-zero, DDB will be entered when the kernel panics.
.It Li DBCTL_FROMCONSOLE
If not zero, DDB may be entered by sending a break on a serial
console or by a special key sequence on a graphics console.
.El
.Pp
These MIB nodes are also available as variables from within the DDB.
See
.Xr ddb 4
for more details.
.Sh CTL_VENDOR
The "vendor" toplevel name is reserved to be used by vendors who wish to
have their own private MIB tree.
Intended use is to store values under
.Dq vendor.\*[Lt]yourname\*[Gt].* .
.Sh RETURN VALUES
If the call to
.Nm
is successful, the number of bytes copied out is returned.
Otherwise \-1 is returned and
.Va errno
is set appropriately.
.Sh FILES
.Bl -tag -width \*[Lt]netinet6/udp6Xvar.h\*[Gt] -compact
.It Pa Aq sys/sysctl.h
definitions for top level identifiers, second level kernel and hardware
identifiers, and user level identifiers
.It Pa Aq sys/socket.h
definitions for second level network identifiers
.It Pa Aq sys/gmon.h
definitions for third level profiling identifiers
.It Pa Aq uvm/uvm_param.h
definitions for second level virtual memory identifiers
.It Pa Aq netinet/in.h
definitions for third level IPv4/v6 identifiers and
fourth level IPv4/v6 identifiers
.It Pa Aq netinet/icmp_var.h
definitions for fourth level ICMP identifiers
.It Pa Aq netinet/icmp6.h
definitions for fourth level ICMPv6 identifiers
.It Pa Aq netinet/tcp_var.h
definitions for fourth level TCP identifiers
.It Pa Aq netinet/udp_var.h
definitions for fourth level UDP identifiers
.It Pa Aq netinet6/udp6_var.h
definitions for fourth level IPv6 UDP identifiers
.It Pa Aq netinet6/ipsec.h
definitions for fourth level IPsec identifiers
.It Pa Aq netkey/key_var.h
definitions for third level PF_KEY 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 CTL_MAXNAME.
.It Bq Er EINVAL
A non-null
.Fa newp
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 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 privilege attempts to set a value.
.It Bq Er EPERM
An attempt to change a value protected by the current kernel security
level is made.
.El
.Sh SEE ALSO
.Xr ipsec 4 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
function first appeared in
.Bx 4.4 .