sysctl - get or set system information
#include <sys/param.h>
#include <sys/sysctl.h>
int
sysctl(int *name, u_int namelen, void *oldp, size_t
*oldlenp, void *newp,
size_t newlen);
The sysctl() function retrieves system information and allows processes
with appropriate privileges to set system information. The
information
available from sysctl() consists of integers, strings, and
tables. Information
may be retrieved and set from the command interface using the
sysctl(8) utility.
Unless explicitly noted below, 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 sysctl() are serialized to avoid deadlock.
The state is described using a ``Management Information Base
(MIB)''
style name, listed in name, which is a namelen length array
of integers.
The information is copied into the buffer specified by oldp.
The size of
the buffer is given by the location specified by 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, oldp and oldlenp should be set to NULL.
The size of the available data can be determined by calling
sysctl() with
a NULL parameter for oldp. The size of the available data
will be returned
in the location pointed to by 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.
To set a new value, newp is set to point to a buffer of
length newlen
from which the requested value is to be taken. If a new
value is not to
be set, newp should be set to NULL and newlen set to 0.
The top level names are defined with a CTL_ prefix 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.
Name Next level names CTL_DDB ddb/db_var.h Kernel debugger
CTL_DEBUG sys/sysctl.h Debugging
CTL_FS sys/sysctl.h File system
CTL_HW sys/sysctl.h Generic
CPU, I/O
CTL_KERN sys/sysctl.h High kernel limits
CTL_MACHDEP sys/sysctl.h Machine
dependent
CTL_NET sys/socket.h Networking
CTL_USER sys/sysctl.h User-level
CTL_VFS ufs/ffs/ffs_extern.h Virtual
file system
CTL_VM uvm/uvm_param.h Virtual
memory
For example, the following retrieves the maximum number of
processes allowed
in the system:
int mib[2], maxproc;
size_t len;
mib[0] = CTL_KERN;
mib[1] = KERN_MAXPROC;
len = sizeof(maxproc);
sysctl(mib, 2, &maxproc, &len, NULL, 0);
To retrieve the standard search path for the system utilities:
int mib[2];
size_t len;
char *p;
mib[0] = CTL_USER;
mib[1] = USER_CS_PATH;
sysctl(mib, 2, NULL, &len, NULL, 0);
p = malloc(len);
sysctl(mib, 2, p, &len, NULL, 0);
CTL_DDB [Toc] [Back]
Integer information and settable variables are available for
the CTL_DDB
level, as described below. More information is also available in ddb(4).
Second level name Type DBCTL_CONSOLE integer yes
DBCTL_LOG integer yes
DBCTL_MAXLINE integer yes
DBCTL_MAXWIDTH integer yes
DBCTL_PANIC integer yes
DBCTL_RADIX integer yes
DBCTL_TABSTOP integer yes
DBCTL_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. As described in securelevel(7), a security
level greater than 1 blocks modification of
this variable.
DBCTL_LOG
When set, ddb output is also logged in the kernel
message buffer.
DBCTL_MAXLINE
Determines the number of lines to page in ddb(4).
This variable
is also available as the ddb $lines variable.
DBCTL_MAXWIDTH
Determines the maximum width of a line in ddb(4).
This variable
is also available as the ddb $maxwidth variable.
DBCTL_PANIC
When this variable is set, system panics may drop
into the kernel
debugger. As described in securelevel(7), a security level
greater than 1 blocks modification of this variable.
DBCTL_RADIX
Determines the default radix or base for non-prefixed numbers entered
into ddb(4). This variable is also available
as the ddb
$radix variable.
DBCTL_TABSTOP
Width of a tab stop in ddb(4). This variable is also available
as the ddb $tabstops variable.
CTL_DEBUG [Toc] [Back]
The debugging variables vary from system to system. A debugging variable
may be added or deleted without need to recompile sysctl()
to know about
it. Each time it runs, sysctl() gets the list of debugging
variables
from the kernel and displays their current values. The system defines
twenty struct ctldebug variables named debug0 through
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
dospecialcheck as a debugging variable, the following declaration would
be used:
int dospecialcheck = 1;
struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
CTL_FS [Toc] [Back]
The string and integer information available for the CTL_FS
level is detailed
below. The changeable column shows whether a process
with appropriate
privileges may change the value.
Second level name Type Changeable
FS_POSIX_SETUID integer yes
FS_POSIX_SETUID
When this variable is set, ownership changes on a
file will cause
the S_ISUID and S_ISGID bits to be cleared. As detailed in
securelevel(7), this variable may not be changed if
the securelevel
is > 0.
CTL_HW [Toc] [Back]
The string and integer information available for the CTL_HW
level is detailed
below. The changeable column shows whether a process
with appropriate
privileges may change the value.
Second level name Type Changeable
HW_BYTEORDER integer no
HW_CPUSPEED integer no
HW_DISKCOUNT integer no
HW_DISKNAMES string no
HW_DISKSTATS struct no
HW_MACHINE string no
HW_MODEL string no
HW_NCPU integer no
HW_PAGESIZE integer no
HW_PHYSMEM integer no
HW_SENSORS struct no
HW_SETPERF integer yes
HW_USERMEM integer no
HW_BYTEORDER
The byteorder (4321 or 1234).
HW_CPUSPEED
The current CPU frequency (in MHz).
HW_DISKCOUNT
The number of disks currently attached to the system.
HW_DISKNAMES
A comma-separated list of disk names.
HW_DISKSTATS
An array of struct diskstats structures containing
disk statistics.
HW_MACHINE
The machine class.
HW_MODEL
The machine model.
HW_NCPU
The number of CPUs.
HW_PAGESIZE
The software page size.
HW_PHYSMEM
The bytes of physical memory.
HW_SENSORS
An array of struct sensor structures containing information from
the hardware monitoring sensors.
HW_SETPERF
Current CPU performance (percentage).
HW_USERMEM
The bytes of non-kernel memory.
CTL_KERN [Toc] [Back]
The string and integer information available for the
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.
Second level name Type KERN_ARGMAX integer
no
KERN_ARND integer
no
KERN_BOOTTIME struct timeval
no
KERN_CCPU integer
no
KERN_CLOCKRATE struct clockinfo
no
KERN_CPTIME long[CPUSTATES]
no
KERN_CRYPTODEVALLOWSOFT integer
yes
KERN_DOMAINNAME string
yes
KERN_EMUL node
not applicable
KERN_FILE struct file
no
KERN_FORKSTAT struct forkstat
no
KERN_FSCALE integer
no
KERN_FSYNC integer
no
KERN_HOSTID integer
yes
KERN_HOSTNAME string
yes
KERN_INTRCNT node
not applicable
KERN_JOB_CONTROL integer
no
KERN_MALLOCSTATS node
no
KERN_MAXCLUSTERS integer
yes
KERN_MAXFILES integer
yes
KERN_MAXPARTITIONS integer
no
KERN_MAXPROC integer
yes
KERN_MAXVNODES integer
yes
KERN_MBSTAT struct mbstat
no
KERN_MSGBUF char[]
no
KERN_MSGBUFSIZE integer
no
KERN_NCHSTATS struct nchstats
no
KERN_NFILES integer
no
KERN_NGROUPS integer
no
KERN_NOSUIDCOREDUMP integer
yes
KERN_NPROCS integer
no
KERN_NSELCOLL integer
no
KERN_NUMVNODES integer
no
KERN_OSRELEASE string
no
KERN_OSREV integer
no
KERN_OSTYPE string
no
KERN_OSVERSION string
no
KERN_POSIX1 integer
no
KERN_PROC struct kinfo_proc
no
KERN_PROC2 struct kinfo_proc2
no
KERN_PROC_ARGS node
not applicable
KERN_PROF node
not applicable
KERN_RAWPARTITION integer
no
KERN_RND struct rndstats
no
KERN_SAVED_IDS integer
no
KERN_SECURELVL integer
raise only
KERN_SEMINFO node
not applicable
KERN_SHMINFO node
not applicable
KERN_SOMAXCONN integer
yes
KERN_SOMINCONN integer
yes
KERN_SPLASSERT int
yes
KERN_STACKGAPRANDOM integer
yes
KERN_SYSVIPC_INFO node
not applicable
KERN_SYSVMSG integer
no
KERN_SYSVSEM integer
no
KERN_SYSVSHM integer
no
KERN_TIMECOUNTER node
not applicable
KERN_TTY node
not applicable
KERN_TTYCOUNT integer
no
KERN_USERASYMCRYPTO integer
yes
KERN_USERCRYPTO integer
yes
KERN_USERMOUNT integer
yes
KERN_VERSION string
no
KERN_VNODE struct vnode
no
KERN_WATCHDOG node
not applicable
KERN_ARGMAX
The maximum bytes of argument to exec(3).
KERN_ARND
Returns a random integer from the kernel
arc4random() function.
This can be useful if /dev/arandom is not available
(see
random(4)).
KERN_BOOTTIME
A struct timeval structure is returned. This structure contains
the time that the system was booted.
KERN_CCPU
The scheduler exponential decay value.
KERN_CLOCKRATE
A 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.
KERN_CPTIME
An array of longs of size CPUSTATES is returned,
containing
statistics about the number of ticks spent by the
system in interrupt
processing, user processes (niced or normal), system processing,
or idling.
KERN_CRYPTODEVALLOWSOFT
Permits userland to use /dev/crypto even if there is
no hardware
crypto accelerator in the system.
KERN_DOMAINNAME
Get or set the YP domain name.
KERN_EMUL
Enable binary emulation.
Third level name Type Changeable
KERN_EMUL_ENABLED integer yes
KERN_EMUL_NAME string no
KERN_EMUL_NEMULS integer no
Third level names in KERN_EMUL other than
KERN_EMUL_NEMULS refer
to a specific emulation available in the kernel.
Valid values
range from 1 to the return value of
KERN_EMUL_NEMULS. The fourth
level names available are KERN_EMUL_NAME, which returns a string
with the emulation name, and KERN_EMUL_ENABLED,
which is an adjustable
integer.
Note that using this interface exposes duplicate entries which
are consolidated by the userland frontend.
KERN_FILE
Return the entire file table. The returned data
consists of a
single struct filehead followed by an array of
struct file, whose
size depends on the current number of such objects
in the system.
KERN_FORKSTAT
A struct forkstat structure is returned. This
structure contains
information about the number of fork(2), vfork(2),
and rfork(2)
system calls as well as kernel thread creations
since system
startup, and the number of pages of virtual memory
involved in
each.
KERN_FSCALE
The kernel fixed-point scale factor.
KERN_FSYNC
Return 1 if the File Synchronisation Option is
available on this
system, otherwise 0.
KERN_HOSTID
Get or set the host ID.
KERN_HOSTNAME
Get or set the hostname.
KERN_JOB_CONTROL
Return 1 if job control is available on this system,
otherwise 0.
KERN_MALLOCSTATS
Return kernel memory bucket statistics. The third
level names
are detailed below. There are no changeable values
in this
branch.
Third level name Type
KERN_MALLOC_BUCKET node
KERN_MALLOC_BUCKETS string
KERN_MALLOC_KMEMNAMES string
KERN_MALLOC_KMEMSTATS node
The variables are as follows:
KERN_MALLOC_BUCKET.<size>
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 struct kmembuckets.
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.
Note that bucket sizes are typically powers
of 2.
KERN_MALLOC_BUCKETS
Return a comma-separated list of the bucket
sizes used by
the kernel.
KERN_MALLOC_KMEMNAMES
Return a comma-separated list of the names
of the kernel
malloc(9) types.
KERN_MALLOC_KMEMSTATS
A node containing the statistics for the
memory types of
the specified name. Each node returns a
struct
kmemstats.
KERN_MAXCLUSTERS
The maximum number of mbuf(9) clusters that may be
allocated.
KERN_MAXFILES
The maximum number of open files that may be open in
the system.
KERN_MAXPARTITIONS
The maximum number of partitions allowed per disk.
KERN_MAXPROC
The maximum number of simultaneous processes the
system will allow.
KERN_MAXVNODES
The maximum number of vnodes available on the system.
KERN_MBSTAT
A struct mbstat structure is returned, containing
statistics on
mbuf(9) usage.
KERN_MSGBUF
Returns a buffer containing kernel log messages.
KERN_MSGBUFSIZE
The size of the kernel message buffer.
KERN_NCHSTATS
A struct nchstats structure is returned. This
structure contains
information about the filename to inode(5) mapping
cache.
KERN_NFILES
Number of open files.
KERN_NGROUPS
The maximum number of supplemental groups.
KERN_NOSUIDCOREDUMP
Programs with their set-user-ID bit set will not
dump core when
this is set.
KERN_NPROCS
The number of entries in the kernel process table.
KERN_NSELCOLL
Number of select(2) collisions.
KERN_NUMVNODES
Number of vnodes in use.
KERN_OSRELEASE
The system release string.
KERN_OSREV
The system revision number.
KERN_OSTYPE
The system type string.
KERN_OSVERSION
The kernel build version.
KERN_POSIX1
The version of ISO/IEC 9945 (POSIX 1003.1) with
which the system
attempts to comply.
KERN_PROC
Return the entire process table, or a subset of it.
An array of
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:
Third level name Fourth level is:
KERN_PROC_ALL None
KERN_PROC_KTHREAD A kernel thread
KERN_PROC_PID A process ID
KERN_PROC_PGRP A process group
KERN_PROC_RUID A real user ID
KERN_PROC_SESSION A session PID
KERN_PROC_TTY A tty device
KERN_PROC_UID A user ID
KERN_PROC2
Like KERN_PROC but an array of struct kinfo_proc2
structures is
returned. The fifth level name is the size of the
struct
kinfo_proc2 and the sixth level name is the number
of structures
to return.
KERN_PROC_ARGS
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:
KERN_PROC_ARGV
KERN_PROC_ENV
KERN_PROC_NARGV
KERN_PROC_NENV
KERN_PROC_NARGV and KERN_PROC_NENV return the number
of elements
in the argv or env array. KERN_PROC_ARGV returns
the argv array
and KERN_PROC_ENV returns the environ array.
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 privileges may change the value.
Third level name Type GPROF_COUNT u_short[]
yes
GPROF_FROMS u_short[]
yes
GPROF_GMONPARAM struct gmonparam
no
GPROF_STATE integer
yes
GPROF_TOS struct tostruct
yes
The variables are as follows:
GPROF_COUNT
Array of statistical program counter counts.
GPROF_FROMS
Array indexed by program counter of callfrom points.
GPROF_GMONPARAM
Structure giving the sizes of the above arrays.
GPROF_STATE
Returns GMON_PROF_ON or GMON_PROF_OFF to
show that profiling
is running or stopped.
GPROF_TOS
Array of struct tostruct describing destination of calls
and their counts.
KERN_RAWPARTITION
The raw partition of a disk (a == 0).
KERN_RND
Returns statistics about the /dev/random device in a
struct
rndstats structure.
KERN_SAVED_IDS
Returns 1 if saved set-group-ID and saved set-userID are available.
KERN_SECURELVL
The system security level. This level may be raised
by processes
with appropriate privileges. It may only be lowered
by process
1.
KERN_SEMINFO
Return the elements of struct seminfo. If the kernel is not compiled
with System V style semaphore support, attempts to retrieve
any of the KERN_SEMINFO values will fail with EOPNOTSUPP. The
third level names for the elements of struct seminfo
are detailed
below. The changeable column shows whether a process with appropriate
privileges may change the value.
Third level name Type Changeable
KERN_SEMINFO_SEMAEM integer no
KERN_SEMINFO_SEMMNI integer yes
KERN_SEMINFO_SEMMNS integer yes
KERN_SEMINFO_SEMMNU integer yes
KERN_SEMINFO_SEMMSL integer yes
KERN_SEMINFO_SEMOPM integer yes
KERN_SEMINFO_SEMUME integer no
KERN_SEMINFO_SEMUSZ integer no
KERN_SEMINFO_SEMVMX integer no
The variables are as follows:
KERN_SEMINFO_SEMAEM
The adjust on exit maximum value.
KERN_SEMINFO_SEMMNI
The maximum number of semaphore identifiers
allowed.
KERN_SEMINFO_SEMMNS
The maximum number of semaphores allowed in
the system.
KERN_SEMINFO_SEMMNU
The maximum number of semaphore undo structures allowed
in the system.
KERN_SEMINFO_SEMMSL
The maximum number of semaphores allowed per
ID.
KERN_SEMINFO_SEMOPM
The maximum number of operations per semop(2) call.
KERN_SEMINFO_SEMUME
The maximum number of undo entries per process.
KERN_SEMINFO_SEMUSZ
The size (in bytes) of the undo structure.
KERN_SEMINFO_SEMVMX
The semaphore maximum value.
KERN_SHMINFO
Return the elements of struct shminfo. If the kernel is not compiled
with System V style shared memory support, attempts to retrieve
any of the KERN_SHMINFO values will fail with
EOPNOTSUPP.
The third level names for the elements of struct
shminfo are detailed
below. The changeable column shows whether a
process with
appropriate privileges may change the value.
Third level name Type Changeable
KERN_SHMINFO_SHMALL integer yes
KERN_SHMINFO_SHMMAX integer yes
KERN_SHMINFO_SHMMIN integer yes
KERN_SHMINFO_SHMMNI integer yes
KERN_SHMINFO_SHMSEG integer yes
The variables are as follows:
KERN_SHMINFO_SHMALL
The maximum amount of total shared memory
allowed in the
system (in pages).
KERN_SHMINFO_SHMMAX
The maximum shared memory segment size (in
bytes).
KERN_SHMINFO_SHMMIN
The minimum shared memory segment size (in
bytes).
KERN_SHMINFO_SHMMNI
The maximum number of shared memory identifiers in the
system.
KERN_SHMINFO_SHMSEG
The maximum number of shared memory segments
per process.
KERN_SOMAXCONN
Upper bound on the number of half-open connections a
process can
allow to be associated with a socket, using listen(2). The default
value is 128.
KERN_SOMINCONN
Lower bound on the number of half-open connections a
process can
allow to be associated with a socket, using listen(2). The default
value is 80.
KERN_SPLASSERT
Modify the system interrupt priority level. Valid
values are:
0 Disable error checking.
1 Print a message if an error is detected.
2 Print a message if an error is detected,
and a stack
trace if possible.
3 The same as 2, but also drop into the
kernel debugger.
Any other value causes a system panic on errors.
See
splassert(9) for more information.
KERN_STACKGAPRANDOM
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.
KERN_SYSVIPC_INFO
Return System V style IPC configuration and run-time
information.
The third level name selects the System V style IPC
facility.
Third level name Type
KERN_SYSVIPC_MSG_INFO struct
msg_sysctl_info
KERN_SYSVIPC_SEM_INFO struct
sem_sysctl_info
KERN_SYSVIPC_SHM_INFO struct
shm_sysctl_info
KERN_SYSVIPC_MSG_INFO
Return information on the System V style
message facility.
The msg_sysctl_info structure is defined in
<sys/msg.h>.
KERN_SYSVIPC_SEM_INFO
Return information on the System V style
semaphore facility.
The sem_sysctl_info structure is defined in
<sys/sem.h>.
KERN_SYSVIPC_SHM_INFO
Return information on the System V style
shared memory
facility. The shm_sysctl_info structure is
defined in
<sys/shm.h>.
KERN_SYSVMSG
Returns 1 if System V style message queue functionality is available
on this system, otherwise 0.
KERN_SYSVSEM
Returns 1 if System V style semaphore functionality
is available
on this system, otherwise 0.
KERN_SYSVSHM
Returns 1 if System V style share memory functionality is available
on this system, otherwise 0.
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.
Third level name Type KERN_TIMECOUNTER_CHOICE string
no
KERN_TIMECOUNTER_HARDWARE string
yes
KERN_TIMECOUNTER_TICK integer
no
KERN_TIMECOUNTER_TIMESTEPWARNINGS integer
no
The variables are as follows:
KERN_TIMECOUNTER_CHOICE
Get the list of kernel time counter sources
and their
claimed quality (higher is better).
KERN_TIMECOUNTER_HARDWARE
Get or set the kernel time counter source by
name.
KERN_TIMECOUNTER_TICK
Get the number of times we have reset the
kernel time
counter information.
KERN_TIMECOUNTER_TIMESTEPWARNINGS
Get or set a flag to log a message when the
kernel time
is stepped.
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.
Third level name Type Changeable
KERN_TTY_INFO struct itty no
KERN_TTY_NPTYS integer no
KERN_TTY_MAXPTYS integer yes
KERN_TTY_TKCANCC int64_t no
KERN_TTY_TKNIN int64_t no
KERN_TTY_TKNOUT int64_t no
KERN_TTY_TKRAWCC int64_t no
The variables are as follows:
KERN_TTY_INFO
Returns an array of struct itty structures
containing tty
statistics.
KERN_TTY_MAXPTYS
The maximum number of pty(4) devices supported by the
kernel. This is the upper bound on
KERN_TTY_NPTYS.
KERN_TTY_NPTYS
The current number of pty(4) devices allocated by the
kernel.
KERN_TTY_TKCANCC
Returns the number of input characters in
canonical mode.
KERN_TTY_TKNIN
Returns the number of input characters from
a tty(4).
KERN_TTY_TKNOUT
Returns the number of output characters on a
tty(4).
KERN_TTY_TKRAWCC
Returns the number of input characters in
raw mode.
KERN_TTYCOUNT
Number of available tty(4) devices.
KERN_USERASYMCRYPTO
Permits userland to use /dev/crypto for cryptographic support for
asymmetric (public) key operations via hardware
cryptographic devices.
kern.usercrypto must also be set.
KERN_USERCRYPTO
Permits userland to use /dev/crypto for cryptographic support via
hardware cryptographic devices.
KERN_USERMOUNT
Return non-zero if regular users can issue mount(2)
requests.
The default value is 0.
KERN_VERSION
The system version string.
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 struct vnode * followed by the vnode
itself struct vnode.
KERN_WATCHDOG
If the kernel does not support a hardware watchdog
timer, attempts
to retrieve or set any of the KERN_WATCHDOG
values will
fail with EOPNOTSUPP.
Third level name Type Changeable
KERN_WATCHDOG_AUTO integer yes
KERN_WATCHDOG_PERIOD integer yes
The variables are as follows:
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
KERN_WATCHDOG_PERIOD variable.
KERN_WATCHDOG_PERIOD
The period of the watchdog timer in seconds.
Set to 0 to
disable the watchdog timer.
CTL_MACHDEP [Toc] [Back]
The set of variables defined is architecture dependent.
Most architectures
define at least the following variables.
Second level name Type Changeable
CPU_CONSDEV dev_t no
CTL_NET [Toc] [Back]
The string and integer information available for the CTL_NET
level is detailed
below. The changeable column shows whether a process
with appropriate
privileges may change the value.
Second level name Type PF_ROUTE routing messages no
PF_INET IPv4 values yes
PF_INET6 IPv6 values yes
PF_ROUTE
Return the entire routing table or a subset of it.
The data is
returned as a sequence of routing messages (see
route(4) for the
header file, format, and meaning). The length of
each message is
contained in the message header.
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:
Fifth level name Sixth level is:
NET_RT_DUMP None
NET_RT_FLAGS rtflags
NET_RT_IFLIST None
PF_INET
Get or set various global information about IPv4
(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:
Protocol name Variable name Type ah enable integer
yes
bpf bufsize integer
yes
bpf maxbufsize integer
yes
carp allow integer
yes
carp arpbalance integer
yes
carp log integer
yes
carp preempt integer
yes
esp enable integer
yes
esp udpencap integer
yes
esp udpencap_port integer
yes
etherip allow integer
yes
gre allow integer
yes
gre wccp integer
yes
icmp bmcastecho integer
yes
icmp errppslimit integer
yes
icmp maskrepl integer
yes
icmp rediraccept integer
yes
icmp redirtimeout integer
yes
icmp tstamprepl integer
yes
ip directed-broadcast integer
yes
ip encdebug integer
yes
ip forwarding integer
yes
ip ipsec-allocs integer
yes
ip ipsec-auth-alg string
yes
ip ipsec-bytes integer
yes
ip ipsec-comp-alg string
yes
ip ipsec-enc-alg string
yes
ip ipsec-expire-acquire integer
yes
ip ipsec-firstuse integer
yes
ip ipsec-invalid-life integer
yes
ip ipsec-pfs integer
yes
ip ipsec-soft-allocs integer
yes
ip ipsec-soft-bytes integer
yes
ip ipsec-soft-firstuse integer
yes
ip ipsec-soft-timeout integer
yes
ip ipsec-timeout integer
yes
ip maxqueue integer
yes
ip mtudisc integer
yes
ip mtudisctimeout integer
yes
ip portfirst integer
yes
ip porthifirst integer
yes
ip porthilast integer
yes
ip portlast integer
yes
ip redirect integer
yes
ip sourceroute integer
yes
ip ttl integer
yes
ipcomp enable integer
yes
ipip allow integer
yes
mobileip allow integer
yes
tcp ackonpush integer
yes
tcp baddynamic array
yes
tcp ecn integer
yes
tcp ident structure no
tcp keepidle integer
yes
tcp keepinittime integer
yes
tcp keepintvl integer
yes
tcp mssdflt integer
yes
tcp reasslimit integer
yes
tcp recvspace integer
yes
tcp rfc1323 integer
yes
tcp rfc3390 integer
yes
tcp rstppslimit integer
yes
tcp sack integer
yes
tcp sendspace integer
yes
tcp slowhz integer
no
tcp synbucketlimit integer
yes
tcp syncachelimit integer
yes
udp baddynamic array
yes
udp checksum integer
yes
udp recvspace integer
yes
udp sendspace integer
yes
The variables are as follows:
ah.enable
If set to 1, enable Authentication Header
(AH) IPsec protocol.
Enabled by default. See ipsec(4)
for more information.
bpf.bufsize
The initial size of BPF buffers.
bpf.maxbufsize
The maximum size a user may request a BPF
buffer to be.
carp.allow
If set to 0, incoming CARP packets will not
be processed.
If set to any other value, processing will
occur. Enabled
by default.
carp.arpbalance
If set to any value other than 0, the ARP
balancing functionality
in carp is enabled. When ARP requests are received
for an IP address which is part of
any virtual
host, carp will hash the source IP in the
ARP request to
select one of the virtual hosts from the set
of all the
virtual hosts which have that IP address.
The master of
that host will respond with the correct virtual MAC address.
Disabled by default.
carp.log
If set to any value other than 0, carp(4)
will log errors.
Disabled by default.
carp.preempt
If set to 0, 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.
esp.enable
If set to 1, enable Encapsulating Security
Payload (ESP)
IPsec protocol. Enabled by default. See
ipsec(4) for
more information.
esp.udpencap
If set to 1, enable processing of UDP encapsulated ESP
packets. Disabled by default.
esp.udpencap_port
Contains the value of the UDP port that
triggers decapsulation
for incoming UDP encapsulated ESP
packets. The
default port is 4500.
etherip.allow
If set to 0, incoming Ethernet-in-IPv4 packets will not
be processed. If set to any other value,
processing will
occur.
gre.allow
If set to 0, incoming GRE packets will not
be processed.
If set to any other value, processing will
occur.
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.
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 "smurfing", and is thus not advised.
icmp.errppslimit
This 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. A negative
value disables
rate limitation.
icmp.maskrepl
Returns 1 if ICMP network mask requests are
to be answered.
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.
icmp.redirtimeout
This variable specifies the lifetime of
routing entries
generated by incoming ICMP redirect. The
default timeout
is 10 minutes.
icmp.tstamprepl
If set to 1, reply to ICMP timestamp requests. If set to
0, ignore timestamp requests.
ip.directed-broadcast
Returns 1 if directed broadcast behavior is
enabled for
the host.
ip.encdebug
Returns 1 when error message reporting is
enabled for the
host. If the kernel has been compiled with
the ENCDEBUG
option, then debugging information will also
be reported
when this variable is set.
ip.forwarding
Returns 1 when IP forwarding is enabled for
the host, indicating
the host is acting as a router.
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.
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
setsockopt(2), or as a result of dynamic
vpn(8) entries.
Supported values are hmac-md5, hmac-sha1,
and hmacripemd160.
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.
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.
ip.ipsec-comp-alg
The compression algorithm to use with an IP
Compression
Association (IPCA). Possible values are
``deflate'' and
``lzs''. Note that lzs is only available
with hifn(4).
See ipsecadm(8) for more information.
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
setsockopt(2), or as a result of dynamic
vpn(8) entries.
Supported values are aes, des, 3des, blowfish, cast128,
and skipjack. 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.
ip.ipsec-expire-acquire
How long should the kernel allow key management to dynamically
acquire security associations, before
re-sending a
request. The default value is 30 seconds.
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.
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.
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
isakmpd(8) exchanges.
The default value is 1.
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.
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.
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.
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.
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.
ip.maxqueue
Fragment flood protection. Sets the maximum
number of
unassembled IP fragments in the fragment
queue.
ip.mtudisc
Returns 1 if Path MTU Discovery is enabled.
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.
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.
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.
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.
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.
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.
ip.sourceroute
Returns 1 when forwarding of source-routed
packets is enabled
for the host. As detailed in securelevel(7), this
variable may not be changed if the securelevel is > 0.
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.
ipcomp.enable
Enable the IPComp protocol. See ipsecadm(8)
for more information.
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.
mobileip.allow
If set to 0, incoming MobileIP encapsulated
packets (RFC
2004) will not be processed. If set to any
other value,
processing will occur.
tcp.ackonpush
Returns 1 if tcp segments with the TH_PUSH
set are being
acknowledged immediately, otherwise 0.
tcp.baddynamic
An array of 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).
tcp.ecn
Returns 1 if Explicit Congestion Notifications for TCP
are enabled.
tcp.ident
A structure struct tcp_ident_mapping specifying a local
and foreign endpoint of a TCP socket is
filled in with
the euid and ruid of the process that owns
the socket.
If no such socket exists, then the euid and
ruid values
are both set to -1.
tcp.keepidle
If the socket option SO_KEEPALIVE has been
set, time a
connection needs to be idle before
keepalives are sent.
See also tcp.slowhz.
tcp.keepinittime
Unused.
tcp.keepintvl
Time after a keepalive probe is sent until,
in the absence
of a
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